LAPORAN
PENELUSURAN INFORMASI ILMIAH SECARA
ONLINE
DENGAN PENGGUNA NYATA (REAL USER)
D
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S
U
S
U
N
I
S
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OLEH :
NAMA : LUKNAH UYUNI
NIM : 132201061
KELAS : A
D-III
PERPUSTAKAAN
FAKULTAS
ILMU BUDAYA
UNIVERSITAS
SUMATERA UTARA
MEDAN
2015
1. Latar Belakang
Perkembangan teknologi terutama
teknologi informasi untuk memenuhi kebutuhan informasi membawa berbagai
perubahan dalam cara menangani, memperoleh, mengumpulkan, dan mengelola
informasi. Dewasa ini terdapat kecenderungan peningkatan pencarian dan
pemanfaatan informasi dalam kehidupan masyarakat, terutama di lingkungan
akademis, dan peneliti melalui kegiatan search engine. Diduga salah satu
penyebab peningkatan tersebut karena sumber-sumber informasi ilmiah dalam
bentuk media digital semakin tersedia untuk diakses secara online.
Di sisi lain, perkembangan teknologi
penyimpanan informasi berkembang pesat. Media digital seperti, Compact
Disk-Read Only Memory (CD-ROM) dan Write Once Read Many (WORM) menjadi media
yang umum digunakan dalam penyimpanan informasi (Koulopoulos, 1995:129). Alasan
utama menjadikan media digital sebagai media penyimpanan informasi adalah
karena kapasitas simpan yang sangat besar, efisiensi dan efektifitas
pengelolaan, kemudahan akses dan temu kembali yang diberikannya kepada pencari
informasi jauh lebih mudah dibanding dengan media cetak.
Peningkatan pencarian dan
pemanfaatan informasi merupakan fenomena yang mengindikasikan bahwa informasi
telah menjadi salah satu kebutuhan hidup yang utama. Oleh karena itu, muncul
banyak cara dan strategi yang dilakukan untuk mendapatkan informasi.
Banyak pencari informasi yang
menginginkan agar informasi yang di butuhkannya bisa diperoleh tanpa meluangkan
waktu yang banyak untuk melakukan penelusuran di internet, CD-ROM, maupun pada
sumber lainnya karena berbagai alasan seperti kesibukan melakukan tugas yang
lain, kurang mengetahui keberadaan sumber-sumber informasi, tidak menguasai
teknik penelusuran secaraa online, dll. Oleh karena itu, pencari informasi
membutuhkan jasa perantara (intermediary) seperti information professional atau
information broker yang peranannya sebagai agen informasi, yang bisa memberikan
layanan jasa untuk mencari informasi yang dibutuhkan, melalui kegiatan penelusuran
dari berbagai basisdata maka dari itu tentunya para pencari informasi tersebut
bersedia memberi imbalan jasa kepada intermediary atas bantuan layanan jasa
pencarian informasi yang disediakan oleh intermediary tersebut. Pencari
informasi merasa wajar membayar layanan jasa pencari informasi yang dilakukan
oleh intermediary tersebut asalkan ia merasa puas, karena informasi yang
diperolehnya sesuai dengan yang diinginkannya (information wants). Dengan
demikian pencari informasi merasa puas, karena bisa menggunakan informasi
tersebut untuk keperluannya (Nicholas, 1996 : 9-10).
Kecenderungan ini tidak selamanya
bisa ditangkap dan diantisipasi oleh mereka yang berkecimpung di bidang
perpustakaan, dokumentasi dan informasi. Bahkan mereka seringkali masih melihat
atau memandang intermediary sebagai suatu problema yang berada di lingkungan
luar lembaga perpustakaan, dokumentasi dan informasi. Padahal menurut
esensinya, bahwa salah satu fungsi dari lembaga sejenis perpustakaan,
dokumentasi, dan informasi adalah sebagai perantara atau agen informasi.
Uraian di atas memberi gambaran bahwa peranan
intermediary dalam kegiatan pencarian informasi semakin diperlukan, karena
kebutuhan informasi masyarakat semakin hari semakin meningkat, sedangkan
kesanggupan mereka melakukan pencarian sendiri sangat terbatas karena
keterbatasan waktu dan berbagai kegiatan lain yang harus dilakukannya. Oleh
karena itu dapat diduga bahwa peran intermediary di kemudian hari pasti akan
berkembang baik secara individual maupun institusional.
Mahasiswi Fakultas MIPA USU membutuhkan peran intermediary
untuk mencari sejumlah dokumen atau informasi yang diperlukan dalam kegiatan
pembuatan jurnal pratikumnya. Ia membutuhkan sebuah informasi berupa jurnal,
dengan subjek Solvents topic polymer. Ia menjelaskan bahwa dokumen atau
informasinya benar-benar terbaru 2014 dan berupa abstrak. Maka dari itu ia
membutuhkan peran intermediary untuk mencari dan mendapatkan dokumen atau
informasi yang berhubungan dengan topik jurnal pratikumnya (penelitian) dengan
alasan keterbatasan waktu sebagai seorang mahasiswi yang sibuk dengan kegiatan
tugas lainnya. Untuk memenuhi kebutuhan pemakai tersebut, saya mencoba membantu
dengan peran sebagai intermediary atau information professional.
2. Kajian Kepustakaan
2.1 Sistem Temu Kembali Informasi
2.1.1 Pengertian dan Tujuan
Penelusuran informasi merupakan
bagian dari sebuah proses temu kembali informasi yang dilakukan untuk memenuhi
kebutuhan pemakai akan informasi yang dibutuhkan, dengan bantuan berbagai alat
penelusuran dan temu kembali informasi yang dimiliki unit informasi. Temu balik informasi merupakan istilah generik yang
mengacu pada temu balik/kembali dokumen atau sumber atau data dari fakta yang
dimiliki unit informasi atau perpustakan.
Konsep dasar dari sistem temu kembali informasi
adalah proses untuk mengidentifikasi kecocokan (match) diantara permintaan
(query) dengan representasi dokumen, kemudian mengambil (retrieve) dokumen dari
suatu simpanan (file), sebagai jawaban atas permintaan tersebut. Sistem temu
kembali informasi pada prinsipnya bekerja berdasarkan ukuran antara istilah
query dengan istilah yang ada dalam dokumen. Oleh karena itu sistem temu
kembali bisa memanggil sejumlah dokumen yang relevan dengan kebutuhan pemakai
dengan efektif dan efisien.
Ingwerson (1992 : 49) sistem temu kembali informasi adalah
proses yang berkaitan dengan representasi, penyimpanan,
pencarian, dan pemanggilan
(retrieval) informasi yang relevan
dengan permintaan yang diinginkan pemakai (user). Salton (1989 : 229) sistem temu
kembali informasi adalah suatu proses (dari suatu file) untuk mengidentifikasi dan memanggil (retrieve) dokumen tertentu dari file tersebut dalam memberikan jawaban atas permintaan informasi. Bisa tidaknya
suatu dokumen terpanggil (pemanggilan
dokumen) tergantung pada kesamaan antara dokumen dengan pertanyaan/permintaan (query). Sulistyo-Basuki (1992 : 132) sistem temu kembali
informasi adalah sejumlah kegiatan yang bertujuan menyediakan dan memasok
informasi bagi pengguna sebagai jawaban atas permintaan pemakai.
Tujuan
utama dari pengembangan sistem temu kembali informasi adalah untuk menemukan
dokumen yang sesuai dengan kebutuhan informasi pengguna secara efisein dan
efektif, sehingga dapan memberikan kepuasan baginya. Dengan demkian sasaran
akhir dari sistem temu kembali informasi adalah kepuasan pemakai. Secara teknis
tujuan sistem temu kembali informasi adalah mencocokkan (macthing) term atau
istilah yang dibangun (query) dengan term atau indeks yang ada dalam dokumen,
sehingga dengan kecocokan tersebut maka dokumen-dokumen yang relevan akan
terambil. Dokumen relevan yang terambil tersebut itulah tujuan dari sistem temu
kembali informasi.
2.1.2 Komponen Sistem Temu Kembali Informasi
Secara
garis besar komponen sistem temu kembali informasi terdiri dari pemakai,
dokumen dan macther-machine (Hasibuan, 1996 : 42). Pertanyaan pemakai (query)
dan dokumen masing-masing di representasikan oleh istilah indeks (index term).
Kemudian kedua bentuk representasi ini akan dipertemukan oleh macther-machine
untuk mengambil dokumen yang relevan dari basisdata. Biasanya representasi
dokumen dan pertanyaan pemakai menggunakan dua jenis bahasa pengindeksan yaitu
bahasa pengindeksan alamiah dan bahasa pengindeksan terkontrol.
Pencocokan
(mactching) adalah proses membandingkan antara istilah yang tercantum dalam
pertanyaan pemakai (query) dengan istilah yang tercantum dalam dokumen (Meadow,
1973 : 131). Pencocokan membutuhkan representasi dokumen. Umumnya sistem temu
kembali informasi didasarkan pada representasi dokumen, karena representasi
tersebut jauh lebih pendek atau lebih ringkas dari dokumen aslinya.
Representasi tersebut dapat berupa abstrak dan istilah indeks. Abstrak adalah
representasi dokumen yang jelas dan ringkas dengan mengikuti pola dan
penyusunan seperti aslinya. Sedangkan indeks adalah dokumen yang telah disimpan
dan diorganisir melalui proses pengindeksan. Dengan menggunakan indeks, maka
proses pencarian dalam sistem temu kembali informasi semakin mudah dilakukan.
2.2 Strategi Pencarian
Strategi pencarian adalah suatu
proses untuk bisa mendapatkan dokumen yang benar-benar relevan dengan kebutuhan
informasi pengguna. Strategi pencarian merupakan himpunan keputusan dan
tindakan yang dilakukan dalam proses pencarian, dengan tujuan untuk menemukan
sejumlah cantuman yang relevan, menghindari ditemukannya dokumen yang tidak
relevan, menghindari jumlah cantuman yang terlalu banyak, dan juga menghindari
tidak ditemukannya cantuman sama sekali. Strategi pencarian dapat dilakukan
dengan pencarian berdasarkan istilah atau dengan Operator Boolean.
2.2.1 Pencarian Berdasarkan Istilah
Umumnya pemilihan istilah yang akan
digunakan dalam pencarian dapat dilakukan dengan menganalisis pertanyaan
sehingga menghasilkan suatu konssep., kemudian konsep tersebut diterjemehkan ke
dalam kosa kata atau indeks yang akan digunakan dalam pencarian. Proses
penerjemahan konsep yang terkandung di dalam pertanyaan menjadi istilah yang
akan digunakan dalam pencarian, harus dilakukan dengan cara yang sama
sebagaimana proses penerjemahan konsep yang menghasilkan indeks dokumen,
sehingga kedua istilah representasi tersebut dapat dipertemukan. Oleh karena
itu dapat dinyatakan bahwa proses temu kembali santa bergantung kepada istilah
pencarian yang dibangun.
2.2.2 Operator Boolean
2.3 Penilaian Relevansi
Penilaian relevansi untuk menyatakan
dokumen mana yang dinilai sesuai atau tepat dari dokumen-dokumen yang telah
ditemukan dari proses temu kembali informasi. Masalah relevansi merupakan
konsep yang sangat penting karena menyangkut ukuran yang menggambarkan efektifitas
dari suatu sistem temu kembali informasi. Efektifitas dari sistem temu kembali
informasi tersebut dapat diukur. Ada dua hal yang biasanya digunakan sebagai
acuan dalam mengukur kemampuan sistem temu kembali informasi yaitu perolehan
(recall) dan ketepatan (precicion) (Leo Pao, 1989 : 225).
Perolehan
(recall) berhubungan dengan kemampuan sistem untuk memanggil dokumen yang
relevan, sedangkan ketepatan (precicion) berkaitan dengan kemampuan sistem
untuk tidak memanggil dokumen yang tidak relevan. Rasio dari tingkat perolehan
(recall) dan ketepatan (precicion) yang dicapai dalam kegiatan penelusuran
dapat diungkapkan sebagai berikut :
Recall
sebenarnya sangat sulit diukur karena jumlah seluruh dokumen yang relevan dalam
basisdata sangat besar. Oleh karena itulah presisi lah (precision) yang
biasanya menjadi salah satu ukuran yang digunakan untuk menilai keefektifan
suatu sistem temu kembali informasi. Untuk memudahkan pemahanan akan kedua
pengukuran tersebut, berikut dikemukakan tabel perhitungan penentuan recall dan
precision.
Tabel 1 Perhitungan
Recall dan Precison
Relevant
|
Not Relevant
|
Total
|
|
Retrieved
|
a
|
b
|
a+b
|
Not Retrieved
|
c
|
d
|
c+d
|
Total
|
a+c
|
b+d
|
Selanjutnya untuk menghitung precision hal sama pada perhitungan recall diberlakukan yaitu jumlah dokumen relevan yang terambil adalah a, sedangkan jumlah dokumen yang terambil dalam pencarian adalah a+b. Dengan demikian rasio precision (P) dapat dinyatakan sebagai berikut :
Kondisi ideal dari keefektifan suatu sistem temu kembali
informasi adalah apabila rasio recall dan precision sama besarnya (1:1).
3. Metodologi
3.1 Pendekatan dan Interaksi dengan Pemakai
Langkah awal untuk memahami kebutuhan informasi
(information need) ialah dengan melakukan pendekatan kepada pemakai (user
approach). Pendekatan ini dilakukan terutama untuk mengetahui karakteristik
umum pemakai, memahami ruang lingkup atau konteks informasi yag dibutuhkan,
mengidentifikasi subjek, dan menyeleksi sumber-sumber basisdata yang akan
digunakan dalam penelusuran. Salah satu cara yang terbaik digunakan adalah
melalui komunikasi personal antara penelusur dengan pemakai.
Pada pertemuan awal, penelusur dan pemakai saling
memperkenalkan diri. Pemakai menjelaskan, bahwa dia mengalami kesulitan
menemukan dokumen yang dibutuhkannya untuk penelitiannya. Ia telah melakukan
pencarian di internet namun masih belum menemukan dokumen atau informasi yang
tepat. Informasi yang diinginkan harus bersifat terbaru dalam bentuk abstrak. Maka dari itu, pemakai membutuhkan jasa penelusur ini untuk
kebutuhan penelitiannya.
3.2 Menaksir atau Menilai Kebutuhan
Informasi Pemakai
Langkah selanjutnya adalah menaksir
atau menilai kebutuhan informasi pemakai (assessing information needs)
berdasarkan paparan atau pernyataan yang di kemukakan oleh pemakai kepada
penelusur. Upaya ini dilakukan dengan menganalisis pernyataan pemakai untuk
menghasilkan suatu konsep, kemudian konsep tersebut diterjemahkan ke dalam kosa
kata atau indeks dengan mengkonsultasikannya kepada thesaurus atau tajuk
subjek. Selanjutnya indeks yang diperoleh digunakan untuk membangun query dalam
pencarian informasi pada basisdata.
Untuk mencapai hal tersebut, penelusur meminta
kesediaan pemakain untuk memaparkan ruang lingkup dari rencana penelitiannya. Kata
kunci dalam kebutuhan informasi yang dibutuhkan adalah pelarut (Solvents) dan
Fluids (Cairan). Dengan berpedoman pada tajuk subjek seperti LCSH dapat
ditaksir atau dinilai bahwa subjek utama yang merupakan istilah luas (Broader
Term) adalah Fluids, kemudian istilah yang berhubungan (Related Term) adalah
Plasticizers, sedangkan istilah khusus atau istilah sempitnya (Nerrower Term)
merupakan jenis-jenis dari solvents.
3.3 Memilih Basisdata
Setelah mengetahui ruang lingkup
subjek informasi yang akan dicari, maka kegiatan yang dilakukan selanjutnya
adalah memilih basisdata yang diperkirakan mengoleksi informasi yang akan
dicari. Ada dua pilihan yang mempertimbangkan untuk dijadikan basisdata yaitu
internet dan CD-ROM. Akan tetapi berdasarkan pengakuan pemakai, bahwa ia telah
melakukan pencarian di internet namun belum mendapatkan dokumen yang
diinginkannya, dan pertimbangan biaya penelusuran di internet saat ini sangat
mahal, maka akhirnya penelusur memutuskan bahwa basisdata yang akan ditelusur
adalah CD-ROM, CD-ROM di akan ditelusur merupakan CD-ROM milik Perpustakaan
USU, putusan ini juga di dukung oleh pemakai./
Untuk menemukan CD-ROM yang relevan
digunakan sebagai basisdata dalam penelusuran, maka penelusur mencari data pada
katalog penerbit CD-ROM yang di miiliki Perpustakaan USU. Ada beberapa
basisdata yang dianggap relevan dimiliki oleh Perpustakaan USU yaitu, ProQuest,
EBSCO, Gale Database, ScienceDirect, dll. Penelusur memilih menggunakan
basisdata ScienceDirect karena pernyataan dari pemakai merupakan bidang ilmu
pengetahuan alam, dan pemakai pun menyetujui basisdata tersebut.
3.4 Membangun dan Mengembangkan
Query
Berdasarkan penilaian atau
penaksiran yang dilakukan terhadap kebutuhan informasi pemakai (assessing
information needs), maka kata kunci (key word) yang akan digunakan dalam
penelusuran adalah
1) Fluids AND Plascitizers
2) Fluids AND Liquid crystalline solvents
3) Fluids AND Ether
4) Fluids AND Percolation
5) Solvents AND Fluids
4. Hasil dan Pembahasan
Kegiatan penelusuran dilakukan
berdasarkan query yang telah dibangun. Dokumen yang terambil dari basisdata
selanjutnya di download ke disk. Setelah kegiatan penelusuran dilakukan, maka
kegiatan selanjutnya adalah melakukan penilaian dan pembahasan terhadap semua
dokumen yang terambil. Pembahasan dilakukan dengan membaca semua dokumen yang
ditemukan, kemudian diperiksa keterkaitan atau keterhubungan (retaledness) dari
masing-masing dokumen dengan setiap query yang telah dibangun dan digunakan
dalam penelusuran. Dengan demikian, penelusur melakukan evaluasi (searcher
evaluation) terhadap semua dokumen yang terambil.
4.1 Dokumen berhubungan yang
terambil dari basisdata
Dokumen berhubungan (retated) adalah
seluruh dokumen yang terambil dari basisdata yang dinilai oleh penelusur
berkaitan atau berhubungan dengan query yang dimasukkan dalam proses
penelusuran. Dengan perkataan lain, dokumen-dokumen yang terambil tersebut
adalah merupakan dokumen yang memiliki relasi atau berhubungan dengan
istilah-istilah pencarian atau query yang dimasukkan ke dalam basisdata pada
saat penelusuran dilakukan.
Tabel
2 Jumlah Dokumen yang Terambil dari Basisdata
No
|
Query
|
Terambil
|
Dicetak
|
1.
|
Fluids AND Plasticizers
|
10
|
8
|
2.
|
Fluids AND Liquid crystalline
solvents
|
17
|
11
|
3.
|
Fluids AND Ether
|
20
|
10
|
4.
|
Fluids AND Percolation
|
7
|
5
|
5.
|
Solvents AND Fluids
|
56
|
27
|
Jumlah
|
110
|
61
|
4.2 Dokumen yang relevan menurut
pemakai
Setelah melakukan penelusuran,
selanjutnya dicetak dan diberikan kepada pemakai unruk mengetahui atau
menetapkan apakah dokumen tersebut relevan atau tidak dengan menyerahkan sati
(1) formulir penilain relevan. Hasil penilaian yang diberikan pemakai terhadap
dokumen tersebut dapat dilihat pada table berikut :
Tabel
3 Dokumen yang Relevan Menurut Pemakai
Nomor
Query
|
Dokumen yang
diberikan
|
Penilaian
Dokumen
|
||
Relevan
|
Hampir
Relevan
|
Tidak
Relevan
|
||
1
|
8
|
4
|
4
|
-
|
2
|
11
|
5
|
4
|
2
|
3
|
10
|
4
|
4
|
2
|
4
|
5
|
2
|
2
|
1
|
5
|
27
|
8
|
12
|
7
|
Jumlah
|
61
|
23
|
26
|
12
|
4.3 Presisi (Precision)
Setelah dinilai relevan oleh
pemakai, maka selanjutnya yang dilakukan adalah menghitung presisi untuk
mengetahui ketepatan dari kinerja penelusur. Untuk menginterpretasikan angka
presisi, ada tiga kategori atau kelas yaitu:
a) Presisi rendah, apabila presisi berada pada rentang
0,00-0,33
b) Presisi sedang, apabila presisi berada pada rentang
0,33-0,66
c) Presisi tinggi, apabila presisi berada pada rentang
0,67-1,00
Tabel 4 Precision
Nomor
Query
|
Dokumen yang
diberikan
|
Dokumen
Relevan
|
Precision
|
1
|
8
|
4
|
0,5
|
2
|
11
|
5
|
0,45
|
3
|
10
|
4
|
0,4
|
4
|
5
|
2
|
0,4
|
5
|
27
|
8
|
0,3
|
Jumlah
|
61
|
23
|
2,05
|
Berdasarkan data pada table diatas
dapat diketahui bahwa rata-rata presisi dari keseluruhan query yaitu 2,05 : 5 =
0,41. Dapat dinyatakan bahwa keseluruhan query memperoleh presisi yang sedang.
Data tersebut membuktikan bahwa secara keseluruhan kinerja penelusuran dinilai
lumayan memuaskan.
5. Kesimpulan
Information professional atau
intermediary yang memberikan layanan jasa untuk pencarian informasi, melalui
kegiatan penelusuran ke berbagai basisdata semakin dibutuhkan. Peran information
professional atau intermediary dirasakan semakin penting, karena kebutuhan
informasi masyarakat semakin hari semakin meningkat. Sedangkan kesanggupan
mereka melakukan pencarian sendiri sangat terbatas, karena keterbatasan waktu,
fasilitas dan berbagai kegiatan lainnya.
Information professional atau intermediary harus
mampu menerjemahkan konsep menjadi istilah-istilah pencarian dengan
mengkonsultasikan terlebih dahulu kepada tajuk subjek seperti LCSH dan Tesaurus.
Setelah itu baru dibangun query –query yang akan dimasukkan ke dalam basisdata
pada sat melakukan penelusuran.
Temu kembali informasi pada basisdata membutuhkan
strategi dan teknik-teknik penelusuran. Strategi dan teknik penelusuran
mencakup kegiatan mengidentifikasi kebutuhan informasi, membangun query dan
memformulasikannya dengan operator Boolean, memilih basisdata yang tepat, serta
dapat melakukan evaluasi terhadap kinerja penelusuran. Dengan berpedoman pada
strategi dan teknik penelusuran tersebut maka system temu kembali ynag
dilakukan memperoleh hasil yang memuaskan.
Daftar Pustaka
Hasibuan, Zainal A. “Kajian Sistem
Temu-Kembali Informasi: Pergeseran Paradigma dari
Orientasi Teknologi ke Orientasi Pemakai”. Prosiding Seminar Sehari Layanan Pusdokinfo
Berorintasi Pemakai di Era Informasi. Depok, 16 Maret 1996
Hasibuan, Zainal A. “Pendekatan
Struktur Dokumen Dalam Sistem Temu-Kembali
Infomasi”. Kursus
Penyegaran dan Penambah Ilmu Perpustakaan Dokumentasi, dan Informasi (KPP Pusdokinfo
VI) di Universitas Indonesia. Depok,13-17 Oktober 1997
Ingwersen,
Peter. Information Retrieval Interaction.
Taylor Graham, London, 1992.
Hasibuan, Jonner. “Penelusuran
Informasi Ilmiah Secara Online: Eksperimen Terhadap
Sistem Temu
Kembali Informasi Dengan Seorang Peneliti Sebagai Real User”.
Koulopoulus, Thomas M; Frappaolo,
Carl. Electronic Document Management Systems.
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Los Angelos, 1973.
Nicholas, David. Assesing Information Needs : Tools and
Techniques. Aslib, London, 1996.
Pao, Miranda Lee. Concepts of Information Retrieval.
Libraries Unlimited, Englewood,
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Aldershot,
Gower, 1995
Lampiran
Dokumen Relevan Menurut Pemakai (User)
1. Query nomor 1 : Fluids AND Plasticizers (4 dokumen )
Solventless polymer coating of microparticles Volume 261, July 2014, Pages 118-132
Abstract :
Solventless
coating technologies have recently emerged to improve upon the processing
inefficiencies and practical limitations of solvent-based polymer film coating.
The purpose of this study was to introduce a dry-coating methodology by which
microparticles can be coated with polymers without the use of solvents,
plasticizers, or heat treatments and is applicable to particles including
those <100 μm, noted as major improvements upon solvent-based and
current dry-polymer coating technologies. Using a vibratory mixing device, the
dry-polymer-coating method developed here first forms an ordered mixture
consisting of a particulate substrate, ascorbic acid, ranging in size from
50 μm to 500 μm coated with a micronized polymer, polyethylene (PE)
wax. Surface energy measurements accurately predicted that PE wax particles
would strongly adhere to ascorbic acid through van der Waals induced attractive
forces indicating a simple approach for predicting substrate–polymer
compatibility. Due to vibration, subsequent particle–particle collisions
between constituents of the ordered mixture deform the polymer layer into a
continuous film resulting in encapsulation of the ascorbic acid. Discrete and
continuous polymer coating could be discriminated based on SEM imaging,
dissolution testing, or dispersive particle size measurements. Furthermore,
polymer coatings were able to prolong the dissolution time of ascorbic acid
from seconds to hours depending on the coating thickness. This novel
dry-polymer-coating technique, operating in dry state without solvents,
plasticizers, or heat treatments while also avoiding particle breakage and
agglomeration, can reasonably be extended to a wide variety of applications
ranging from the control release of pharmaceutical microparticles to protective
coatings for metal powders.
Keywords : Dry polymer
coating; Ordered mixtures; Control release; Water soluble
drugs; Microparticles; Solventless coating.
Control of the hierarchical structure of polymer
articles via “structuring” processing Volume 39, Issue 5, May 2014, Pages 891-920
Abstract :
Every
day, numerous polymer materials are fabricated into specific articles with
definite sizes, shapes and forms using polymer processing. Obviously, polymer
processing has become one of the most active areas of polymer science and
engineering. The key is to profoundly explore the
processing-structure-performance relations for various polymer-based materials.
From a structure-dominated performance point of view, the ultimate
physical/chemical properties of polymer articles are directly related to their
internal multiscale (hierarchical) structures, which range from the molecular,
nanometer, submicron and micron scale to the mesoscopic level. Because the
features of hierarchical structures strongly depend on the external fields that
are imposed during processing, many structural items, such as the chain
configuration, crystalline polymorphism, orientation and phase separation
behavior, can be well or precisely controlled, resulting in significant
variations in the hierarchical structure. Due to developments in mechanical
techniques, various external fields, such as thermal, shear, extension, ultrasonic,
electronic, magnetic and super-critical fluid fields, may be introduced into
polymer processing, leading to significant improvements in the tailoring of the
microstructure/morphology via processing. This process is characterized by an
“externally applied field determined hierarchical structure”, i.e., a
“structuring” processing, which represents an advanced trend in modern polymer
processing and is the topic of this review. This contribution includes the
following: (1) an introduction, (2) the in situ monitoring of polymer
processing, (3) progress in “structuring” processing and (4) concluding remarks
and perspectives.
Keywords : Polymer
processing; Structural control; Externally applied field
Aluminosilicate and aluminosilicate based polymer
composites: Present status, applications and future trends Volume 89, Issues
3–4, August–December 2014, Pages 239-277
Abstract :
Aluminosilicates
have traditionally been important materials for applications related to
adsorbents, water softeners, catalysis and mechanical and thermal reinforcement
due to their high surface area, excellent thermal/hydrothermal stability, high
shape-selectivity and superior ion-exchange ability. Recently, their use as
polymer fillers has allowed to increasingly extending their application range
to innovative areas such as medical and biological fields as well as in
sensors, filtration membranes, energy storage and novel catalysis routes.
Further, the large versatility and tailoring possibilities of both filler and
matrix indicates this area as one of the enabling key technologies of the near
future.
This
work summarizes the main developments up to date in this increasingly
interesting field, focuses on the main applications already developed as well as
on the key challenges for the near future.
Keywords
: Aluminosilicates; Polymers; Composites; Applications
Measuring and correlating diffusivity in
polymer–solvent systems using free-volume theory Volume 362, 25 January
2014, Pages 19-27
Abstract :
This
paper provides a review of the measurement, data reduction, and correlation of
diffusivities using the free-volume theory for polymer–solvent systems, particularly
in the range of very low solvent concentration. The experimental methods
discussed are inverse gas chromatography, gravimetric sorption, and pressure
decay. The free-volume model is described in terms of its potential and
limitations for correlation and extrapolation of diffusion data. Data are given
and analyzed for a number of systems including two of practical importance:
solvents in poly(vinyl alcohol) and bisphenol-A in poly(vinyl chloride).
Keywords
: Free-volume model; Diffusion; Solubility; Polymer–solvent systems
2. Query 2 : Fluids AND Liquid Crystalline
Solvents (5 dokumen)
Plastic crystalline-semi
crystalline polymer composite electrolyte based on non-woven
poly(vinylidenefluoride-co-hexafluoropropylene)
porous membranes for lithium ion batteries Volume 125, 10 April 2014, Pages 362-370
Abstract :
The advantageous properties of both solid soft matter
electrolytes and polymer gel electrolytes (PGEs) are combined to develop a
electrospun polymer composite electrolyte (PCE) for lithium ion batteries, based on addition of butanedinitrile (BDN, the
plastic crystal) to poly(vinylidenefluoride-co-hexafluoropropylene)
{P(VdF-co-HFP)} (semi crystalline polymer). Polymer composite
electrolytes are prepared by activating the fibrous membrane with 1 M LiPF6 in EC/DEC. The electrochemical
characterization shows that the addition of BDN significantly improves the
ionic conductivity of composite electrolytes even at lower temperatures due to
the active role played by BDN in ion conduction. Also the compatibility of the
polymer composite electrolyte with lithium electrode improves by incorporation
of BDN. Galvanostatic cycling test demonstrates the suitability of these
polymer composite electrolytes for lithium ion batteries in both Li/PCE/LiFePO4 (half cell) and LTO/PCE/LiFePO4 (full cell) configurations. The addition of
BDN improves the charge discharge performance and cycling stability of the
polymer composite electrolytes.
Keywords
: Polymer gel electrolytes; Plastic crystal; Ionic conductivity; Electrospinning;
Lithium ion batteries.
Structure and polymer dynamics within PNIPAM-based microgel
particles Volume 205, March 2014, Pages 113–123
Benjamin
Sierra-Martin, Jorge
Rubio Retama, Marco
Laurenti, Antonio
Fernández Barbero, Enrique
López Cabarcos
Abstract :
The synthesis of temperature-responsive microgels of poly(N-isopropylacrylamide)
(PNIPAM) was first reported in 1986 and, since then, there have been hundreds
of publications describing the preparation, characterization and applications
of these systems. This paper reviews the developments concerning the study of
the structure of PNIPAM-based microgels performed over the last years using
small angle neutron scattering (SANS) and also the investigations of the
polymer-chain dynamics within the microgels carried out with incoherent elastic
and quasielastic neutron scattering, and pulse field gradient nuclear magnetic
resonance (PFG-NMR) techniques. Furthermore, the self-diffusion coefficient of
the water molecules within the microgel, determined by means of solvent
relaxation NMR, is also discussed as a function of the polymer volume fraction
of the microgels
Keywords: Microgel; PNIPAM; Polymer dynamics; Neutron scattering; PFG-NMR
Polymer–silica composite as a carrier of an active
pharmaceutical ingredient Volume 193, 15 July 2014, Pages 40–46
Abstract :
The present article describes the
synthesis of a novel type of a composite which has potential application in
controlled drug release. The system comprises of the porous polymer matrix with
embedded active agent and the silica gel. The silica is introduced into the
polymer beads with encapsulated drug by swelling in tetraethoxysilane as the
silica precursor. After the condensation of the silica source, the silica
membrane is formed inside the core of pores. Scanning electron microscopy (SEM)
combined with energy dispersive X-ray spectroscopy (EDX) allow for the
assumption that the examined polymer–drug–silica composite is rich in silica, homogeneously
dispersed within the polymer matrix. What is more, the introduction of the
siliceous membrane significantly changes the porosity, which affects drug
diffusion. The purpose of this study was to investigate the drug release
process from the pure polymer and polymer–silica
composite with regard to their structural parameters. The drug desorption was
examined in a NaCl solution and in a simulated body fluid (SBF) at different
temperatures.
Keywords : Polymer–silica
composite; Swelling; Drug
release; Naproxen
In situ FTIR micro-spectroscopy to investigate
polymeric fibers under supercritical carbon dioxide: CO2 sorption
and swelling measurements Volume 90, June 2014,
Pages 44–52
Abstract :
An original experimental set-up combining a FTIR (Fourier
Transformed InfraRed) microscope with a high pressure cell has been built in
order to analyze in situ and simultaneously the CO2 sorption
and the polymer swelling of microscopic polymer samples, such as fibers, subjected
to supercritical carbon dioxide. Thanks to this experimental set-up, we have
determined as a function of the CO2 pressure
(from 2 to 15 MPa) the CO2 sorption
and the polymer swelling at T = 40 °C
of four polymer samples, namely PEO (polyethylene oxide), PLLA (poly-l-lactide acid), PET (polyethylene
terephtalate) and PP (polypropylene). The quantity of CO2 sorbed in all the studied polymers increases
with pressure. PEO and PLLA display a significant level of CO2 sorption (20 and 25% respectively, at P = 15 MPa). However, we observe that a
lower quantity of CO2 can be sorbed into PP and
PET (7 and 8% respectively, at P = 15 MPa).
Comparing their thermodynamic behaviors and their intrinsic properties, we
emphasize that a high CO2 sorption
can be reach if on one hand, the polymer is able to form specific interaction
with CO2 in order to thermodynamically favor the
presence of CO2 molecules inside the
polymer and on the other, displays high chains mobility in the amorphous
region. PLLA and PEO fulfilled these two requirements whereas only one property
is fulfilled by PET (specific interaction with CO2) and PP (high
chains mobility). Finally, we have found that for a given CO2 sorption, the resulting swelling of the
polymer depends mainly on its crystallinity.
Keywords : Supercritical
carbon dioxide; Polymer swelling; CO2 sorption; FTIR
microscopy; Fiber
From polymer to polyelectrolyte: Studies of
star-branched poly(ethylene oxide) with lithium functional groups Volume 115, 1 January
2014, Pages 612–620
Abstract :
Star-branched poly(ethylene oxide) with PG-PPO core has
been synthesized. The branched structure had on average 18 poly(ethylene oxide)
arms with average molecular weight of 1680. The chain ends were capped with OH
groups which were then substituted with lithium-containing P(
O)(OLi)2, COOLi and SO3Li groups. The
substitution level ranged from 30% to 95%. Characterization of physical
properties was carried out by various methods, including differential scanning
calorimetry and impedance spectroscopy. The results show that polymers with
functional groups containing lithium are characterized by relatively high ionic
conductivity. The highest ionic conductivity, reaching 8 × 10−6 S/cm at 20 °C was obtained for polymer
with P(O)(OLi)2 groups, which demonstrates possibility of
using these polymers as polyelectrolyte. It has been also found, that the
presence of end groups can decrease crystallinity and lower glass transition
temperature of polymer. Electrolytes formed by adding LiN(CF3SO2)2 salt to polymers with functional groups
containing lithium had higher ionic conductivity and lower glass transition
temperature than electrolytes based on polymer without such groups.
O)(OLi)2, COOLi and SO3Li groups. The
substitution level ranged from 30% to 95%. Characterization of physical
properties was carried out by various methods, including differential scanning
calorimetry and impedance spectroscopy. The results show that polymers with
functional groups containing lithium are characterized by relatively high ionic
conductivity. The highest ionic conductivity, reaching 8 × 10−6 S/cm at 20 °C was obtained for polymer
with P(O)(OLi)2 groups, which demonstrates possibility of
using these polymers as polyelectrolyte. It has been also found, that the
presence of end groups can decrease crystallinity and lower glass transition
temperature of polymer. Electrolytes formed by adding LiN(CF3SO2)2 salt to polymers with functional groups
containing lithium had higher ionic conductivity and lower glass transition
temperature than electrolytes based on polymer without such groups.
Keywords : Poly(ethylene
oxide); Polymer electrolyte; Polyelectrolyte; Ionic conductivity
3. Query 3 : Fluids AND Ether (4 dokumen)
Liquid–liquid phase equilibria for ternary systems of
several polyethers with NaCl and H2O Volume 376, 25 August
2014, Pages 76–84
Abstract :
Liquid–liquid
extraction using polymers followed by induced phase separation is a potential
energy reducing technology for water–salt separation. Ternary equilibrium data
have been determined and reported for the (block co)poly ethers–sodium
chloride–water systems at two different temperatures at 298.15 K and 313.15 K
and atmospheric pressure. The experimental data were correlated with the NRTL
model, and the obtained binary interaction parameters to describe the ternary
liquid–liquid systems at different temperatures are presented. The model
predictions are in good agreement with the experimental data.
Keywords
: Aqueous two-phase systems; Polyethers; Sodium chloride; Extraction; NRTL modeling
Experimental data and thermodynamic modeling of
ternary aqueous biphasic systems of EO/PO polymers–Na2SO4–H2O Volume 366, 25 March 2014,
Pages 45–56
Abstract :
Liquid–liquid
extraction using thermoresponsive polymers as solvents in aqueous two phase
systems followed by induced phase separation to recover the polymers is a
potential technology for water–salt separations. Here we report for seven
polymers on their ternary systems containing water, sodium sulfate and the
(block co)poly ether. Equilibrium data were measured at 298.15 K and
313.15 K and atmospheric pressure. Empirical equations have been used to
correlate the experimental equilibria for both temperatures separately and the
semi-empirical NRTL model has been applied with a temperature dependent
parameter to describe the complete dataset for both temperatures together.
Model predictions were in good agreement with the experimental data.
Keywords
: Liquid–liquid extraction; Aqueous two-phase systems; (block co)
polyethers; Sodium sulfate; NRTL
Polymer conjugates of doxorubicin bound through an
amide and hydrazone bond: Impact of the carrier structure onto synergistic
action in the treatment of solid tumours Volume 58, 16 July 2014,
Pages 1–12
Abstract :
In this study, we describe the synthesis, physico-chemical
characterisation and results of the in vitro and in vivo evaluation of the biological behaviour
of N-(2-hydroxypropyl)methacrylamide-based (HPMA)
copolymer conjugates bearing doxorubicin (DOX) partly bound via a pH-sensitive
hydrazone and partly via enzymatically degradable amide bonds, each
contributing to a different anti-tumour mechanism of action of the
polymer–doxorubicin conjugate. The following two types of HPMA copolymer drug
carriers designed for passive tumour targeting were synthesised and compared:
the linear non-degradable copolymer and the biodegradable high-molecular-weight
(HMW) diblock copolymer. The HMW diblock copolymer carrier containing a
degradable disulphide bond between the polymer blocks showed a rapid
degradation in a buffer containing glutathione within the first few hours of
incubation. In contrast to the conjugate with the amide bond-bound DOX
requiring the presence of lysosomal enzymes to release DOX, the polymer–drug
conjugate with the DOX bound via a hydrazone bond released DOX by pH-sensitive
hydrolysis, which was significantly faster in a buffer of pH 5.0 (intracellular
pH) than pH 7.4, mimicking the conditions in the bloodstream. The significant
and comparable in vivo anti-tumour activity
of the diblock HMW conjugate and an equimolar mixture of the conjugates
differing in the DOX attachment method along with the development of cancer
resistance during treatment with these conjugates demonstrated the high
potential of these compounds in the development of new nanomedicines suitable
for the treatment of solid tumours.
Keywods
: HPMA copolymer; Synergistic effect; Doxorubicin; Drug delivery; In vivo efficacy
Nano-emulsion based on acrylic acid ester co-polymer
derivatives as an efficient pre-tanning agent for buffalo hide Available online 9 July 2014
Farouk
Abd El-Monem, Ahmed
I. Hussain, EL-Shahat
H.A. Nashy, Hamada
Abd El-Wahhab, Abd
El-Rahman M. Naser
Abstract :
Acrylic
copolymer nanoemulsions were prepared based on methyl methacrylate (MMA) and butyl
acrylate (BA). The prepared acrylic copolymer emulsions were characterized
using solid content, rheological properties, molecular weight, MFFT and TEM.
The prepared polymers were used as pre-tanning of the depickled hide to enhance
the physico-mechanical properties of tanned leather. The key parameters which
affect exhaustion and fixation of chrome tan as well as shrinkage temperature
of the tanned leather were studied and evaluated using SEM, shrinkage
temperature and the mechanical properties of the pre-tanned leather. The
results showed that, the prepared polymers A & C are the best polymers in
improving the physical properties of the treated leather. Furthermore, the
shrinkage temperature and the mechanical properties of the tanned leather were
improved. In addition, a significant enhancement in the texture of the leather
treated by the polymers was noticed as proved by scanning electron microscopy
(SEM).
Keywords
: Acrylic acid ester copolymers; Nanoemulsion; Pre-tanning agent; Depickled hide; Chrome tan; Chromium uptake
4.
Query
4 : Fluids AND Percolation (2 dokumen)
Structuration, selective dispersion and
compatibilizing effect of (nano)fillers in polymer blends Volume 39, Issue 8, August 2014,
Pages 1526–1563
Abstract :
Hybrid ternary blends comprising two polymers and one
mineral (nano)filler are increasingly studied because they are starting to be
widely used to respond to industrial issues. The objective of this review is to
gather information on these particular systems. Concerning first thermodynamic
effects of fillers on the phase separation of an immiscible polymer blend,
Flory–Huggins theory demonstrate stabilization. This theory was particularly
taken up and developed for the case of two polymers and one filler by Lipatov
and Nesterov in the 90s. More recently, Ginzburg generalized this theory to the
case of unfavorable enthalpic interactions between a particle and the two
polymers. They showed that the amount of particles had to attain a certain
threshold to stabilize the system and the lower the particle radius, the higher
the stable zone area. Generally speaking, all the phenomena regarding the
morphology of polymer blends are governed by thermodynamics and/or kinetic
effects, as well as the localization of nanoparticles. The main discussed
thermodynamically controlling parameter of the localization is the wetting
parameter ωAB. However,
because of the viscosity of the system, the equilibrium dictated by ωAB may never
be reached. Hence, concerning the kinetic effects, the final localization of
fillers in a polymer pair is guided by the sequence of mixing of the
components, the viscosity ratio, the composition, the temperature, the shear
rate and the time of mixing. When the particles are placed at the interface
between two polymers, coalescence can be suppressed or/and interfacial tension
can be reduced. In that case, particles are known to play the role of a
compatibilizer. In a ternary system, (i) the shape of the particle (spheres,
rods or “onions-shape”), (ii) the particle radius (Rp) versus the
radius of gyration of the polymers (Rg) and (iii) the surface chemistry of the particles
affect the final localization of the particles (thus, the compatibilizing
effect) and the final properties of the material, such as mechanical,
conductive, magnetic and thermal properties. This review details recent works
for which those four above mentioned properties are improved by incorporating
different kind of fillers in polymer blends.
Keywords
: Polymer blends; Nanoparticles; Compatibilization; Thermodynamics effects; Kinetics effects; Wettability
Pros and cons of melt annealing on the properties
of MWCNT/polypropylene composites Volume 110, December 2014,
Pages 56–64
Abstract :
The
combined effect of melt annealing and surface modification of multiwalled
carbon nanotubes (MWCNT) on polypropylene (PP) based nanocomposites is
reported. Melt annealing markedly improved the filler dispersion in PP. The
rheological and electrical percolative threshold was achieved at a content of
3 wt% MWCNT, due to the dynamic reconstruction of nanotube network in the
polymer matrix. This behaviour was particularly evident in the case of surface-modified
MWCNT. However, the heat treatment also induced an overall worsening of
mechanical properties due to polymer heterogeneous oxidation at a microscopic
scale, as detected by oxygen mapping through SEM/EDS. Crack initiation sites
eventually leading to the failure of the polymer were formed due to
peroxide-mediated spreading of oxidation, radiating from residual
polymerisation catalyst particles. FTIR-ATR spectroscopy demonstrated that
blooming of the phenol stabilizer due to thermal annealing was responsible for
early oxidation of polypropylene. The reported results highlight the advantages
and drawbacks of physical strategies designed to improve the dispersion
stability of nanotubes in polymer nanocomposites.
Keywords : Polypropylene; Multiwalled carbon nanotubes; Heat
treatment; Rheological properties; Electrical properties; Thermal oxidation
5.
Query
5 : Solvents AND Fluids (8 dokumen)
Effect of solvent exchange on the
stability of sterically functionalized magnetite nanoparticles in poly(methyl
methacrylate) solutions and resulting spray dried composites Volume 92, Issue 11, November 2014, Pages 2523–2533
Abstract
:
In
this study highly filled nanoparticle–polymer composites consisting of the
polymer poly(methyl methacrylate) and magnetite nanoparticles are synthesized
via the solution and spray drying method. The synthesis process is carried out
for two different solvents, dichloromethane and ethyl acetate, and the
resulting suspensions and composites are compared to each other. The
preparation of the composites consists of the following steps: First the
magnetite nanoparticles are precipitated in an aqueous phase. In the next step
the nanoparticles are coated with ricinoleic acid for stabilization and are
transferred to the organic solvent dichloromethane. In a rotating evaporator
the solvent dichloromethane is exchanged with ethyl acetate. Finally, the
nanoparticles in the respective solvent and dissolved polymer are mixed and
spray dried.The stability of the nanoparticle suspensions is characterized
using thermogravimetric and photometric analyses. The specific surface of
spray-dried composites is determined via BET measurements and the distribution
of the nanoparticles is assessed with BSE-SEM imaging and laser diffraction.The
stability of the nanoparticles is independent of the examined solvents. Both
solvents provide a homogeneous distribution of nanoparticles in the composite
at high filler concentrations.
Keywords : Polymer nanocomposites; Spray drying; Magnetite nanoparticles; Solvent; Ethyl acetate; Dichloromethane
Abstract
:
Nanoparticles (NPs) composed of polymers are of great
interest since they can add a functionality in many applications, ranging from
food and pharma to plastics and electronics. A key factor that determines the
functionality of NPs is their size. Nanoprecipitation is a commonly used
technique to prepare NPs. We have performed a combined experimental and theoretical
study on the size of NPs formed by precipitation of polymers into a bad solvent
in the presence of a stabilizing surfactant. We propose an extension of the
theoretical framework put forward by Lannibois et al. for nanoparticle
formation via precipitation. Our theory is based upon a kinetic model for
diffusion limited coalescence (DLC) in which the relevant transport and
diffusion mechanisms are quantified. We find that the macroscopic mixing time
and the diffusivity of the polymer and surfactant are the main parameters
determining the final particle size. The theoretical result for the final size
can be condensed into a single analytical expression. At given polymer
concentration and mixing time, it follows that the smallest particles can be
obtained in the excess of surfactant. This situation corresponds well to the
experimentally used conditions. The mixing efficiency is predicted to have a
profound influence on the final particle diameter: faster mixing results in
smaller particles. The final particle size in the slow mixing regime, which is
the typical situation in experiments, turns out to be independent of the molar
mass of the polymer and scales as a power 1/3 with the initial polymer
concentration. An increase of the surfactant molar mass is predicted to lead to
larger particles, because of longer mixing time and lower surfactant mobility. We
have performed systematic experimental investigations on nanoparticles
formation using various systems but focused on polycaprolactone (PCL) polymers
in acetone precipitated in aqueous solutions containing polyvinyl alcohol as
surfactant. The PCL molar mass and concentration and mixing time were varied.
We show that both our experimental results as well as literature data are in
good agreement with our theoretical DLC predictions. This work therefore
provides a solid framework for tailoring nanoparticles with a desired size.
Keywords : (Nano)Precipitation; Particle size; Encapsulation; Surfactant; Polymer; Diffusion limited coalescence
Abstract
:
Solventless
coating technologies have recently emerged to improve upon the processing
inefficiencies and practical limitations of solvent-based polymer film coating.
The purpose of this study was to introduce a dry-coating methodology by which
microparticles can be coated with polymers without the use of solvents,
plasticizers, or heat treatments and is applicable to particles including
those <100 μm, noted as major improvements upon solvent-based and
current dry-polymer coating technologies. Using a vibratory mixing device, the
dry-polymer-coating method developed here first forms an ordered mixture
consisting of a particulate substrate, ascorbic acid, ranging in size from
50 μm to 500 μm coated with a micronized polymer, polyethylene (PE)
wax. Surface energy measurements accurately predicted that PE wax particles
would strongly adhere to ascorbic acid through van der Waals induced attractive
forces indicating a simple approach for predicting substrate–polymer
compatibility. Due to vibration, subsequent particle–particle collisions
between constituents of the ordered mixture deform the polymer layer into a
continuous film resulting in encapsulation of the ascorbic acid. Discrete and
continuous polymer coating could be discriminated based on SEM imaging,
dissolution testing, or dispersive particle size measurements. Furthermore,
polymer coatings were able to prolong the dissolution time of ascorbic acid
from seconds to hours depending on the coating thickness. This novel
dry-polymer-coating technique, operating in dry state without solvents,
plasticizers, or heat treatments while also avoiding particle breakage and
agglomeration, can reasonably be extended to a wide variety of applications
ranging from the control release of pharmaceutical microparticles to protective
coatings for metal powders.
Keywords
: Dry polymer coating; Ordered mixtures; Control release; Water soluble drugs; Microparticles; Solventless coating
A critical
review on use of polymer microgels for conformance control purposes October 2014,
Vol.122:741–753
Mazen
Abdulbaki; Chun Huh; Kamy Sepehrnoori; Mojdeh Delshad ; Abdoljalil Varavei
Abstract :
1. Context
Polymer microgels are
submicron-to-micron size, water-dispersible particles that are formed through
use of a crosslinking agent. Their permeability reduction capabilities, when
triggered, enable the strategic plugging of high-permeability channels so as to
divert flooding fluid to the relatively unswept adjacent low-permeability
zones. This improves macroscopic sweep efficiency, increasing hydrocarbon
production and decreasing associated water production. Polymer microgel
flooding thus serves to provide in-depth conformance control, distinguishing it
from conventional polymer floods that offer primarily mobility control
benefits.
2. Objective
This paper provides a literature
review on the use of polymer microgel technology for conformance control
purposes.
3. Method
Polymer microgel flooding is first
introduced, and the motivation for their use over conventional polymer flooding
is outlined. This is followed by a discussion on the characterization of
polymer microgels as well as some theories on how they act as conformance
control agents. In addition, an extensive survey of four different types of
polymer microgels (Colloidal Dispersion Gels, Preformed Particle Gels,
Temperature-Sensitive Microgels, and pH-Sensitive Polymer Microgels) is
provided. Attention is mainly given to the microgel characteristics, laboratory
observations, and field applications. The rheology and plugging mechanism of
the different polymer microgels are also discussed in some detail.
4.Conclusion
Polymer microgel flooding is gaining
popularity as a means of conformance control. Despite uncertainty around the
precise mechanism by which microgels divert flow, numerous lab and field
applications have demonstrated this technology׳s ability to improve sweep
efficiency and enhance oil recovery.
Keywords : Microgels; Conformance control; Mobility control; Polymer gels
Preparation
of uniform micrometer-sized polymer particles with closed-cell porous
architecture made by limited coalescence of a double emulsion 20 February 2014,
Vol.443:583–595
Mridula
Nair; Charles P. Lusignan; David C. Boris
Abstract :
We describe a new and practical
process for making narrow size distribution polymer particles in the 4–20 μm
size range that contain uniform multiple closed-cell pores with excellent
simultaneous predictive regulation of micrometer and sub-micrometer sized
features. Our approach involves making a water-in-oil-in-water (W1/O/W2)
double emulsion through a sequence of controlled emulsification and droplet
solidification steps with several differentiating aspects from the standard
double emulsion method. Firstly, providing colloidal stability to the inner
emulsion (W1/O) through the use of an ionized hydrocolloid in W1,
where the oil phase (O) is a high molecular weight branched polyester in ethyl
acetate. Secondly, control of particle size and size distribution using the
limited coalescence (LC) process after high pressure homogenization of the
water-in-oil-in-water (W1/O/W2) emulsion through an
orifice plate, delivering rapid pressure drop, constant back pressure and large
extensional deformation to break up the oil phase droplets of the W1/O/W2 premix
without destroying the integrity of the inner emulsion. While Pickering double
emulsions have been made, conventional wisdom regarding the robustness of such
emulsions, has precluded high pressure homogenization required in the LC
process to make <20 μm, narrow size distribution particles. In this work we
present a material system and an emulsification technique that were co-designed
to overcome this limitation. Finally, the ionized hydrocolloid enables manipulation
of osmotic pressure of the inner and outer water phases across the oil
membrane, tuning the size of the internal features from hundreds of nanometers
to several microns while maintaining the closed-cell architecture of the final
particle. While it is especially challenging to achieve such control in
structurally complex microparticles, this paper demonstrates a simple, yet
truly versatile, adaptable and scalable solution for making functional,
closed-cell porous polymer particles. Representative images of whole and
fractured porous particles are shown in the Graphical Abstract.
Keywords :Porous
polymer particles; Limited coalescence;
Double emulsion; Pickering
emulsion; Osmotic pressure
Conductive
polymers: Towards a smart biomaterial for tissue engineering June 2014,
Vol.10(6):2341–2353
Richard
Balint; Nigel J. Cassidy; Sarah H. Cartmell
Abstract :
Developing stimulus-responsive biomaterials
with easy-to-tailor properties is a highly desired goal of the tissue
engineering community. A novel type of electroactive biomaterial, the
conductive polymer, promises to become one such material. Conductive polymers
are already used in fuel cells, computer displays and microsurgical tools, and
are now finding applications in the field of biomaterials. These versatile
polymers can be synthesised alone, as hydrogels, combined into composites or
electrospun into microfibres. They can be created to be biocompatible and
biodegradable. Their physical properties can easily be optimized for a specific
application through binding biologically important molecules into the polymer
using one of the many available methods for their functionalization. Their conductive
nature allows cells or tissue cultured upon them to be stimulated, the
polymers’ own physical properties to be influenced post-synthesis and the drugs
bound in them released, through the application of an electrical signal. It is
thus little wonder that these polymers are becoming very important materials
for biosensors, neural implants, drug delivery devices and tissue engineering
scaffolds. Focusing mainly on polypyrrole, polyaniline and
poly(3,4-ethylenedioxythiophene), we review conductive polymers from the
perspective of tissue engineering. The basic properties of conductive polymers,
their chemical and electrochemical synthesis, the phenomena underlying their
conductivity and the ways to tailor their properties (functionalization,
composites, etc.) are discussed.
Keywords : Conductive
polymer; Drug release; Biocompatibility; Polypyrrole
Polyaniline
Multiscale modeling of polymer
flow-induced migration and size separation in a microfluidic contraction flow September 2014,
Vol.211:84–98
Lei
Jiang; Ronald G. Larson
Abstract :
We
study polymer migration in a periodic pressure-driven sudden
contraction-expansion flow with contraction dimension comparable to the polymer
radius of gyration, for which several polymer migration mechanisms can be
important: (1) sieving by the thin channel of polymers too large to easily
enter them; (2) deformation-hydrodynamic coupling, including wall-hydrodynamic
interaction, which causes polymers to drift away from the walls towards the
center of the channel; (3) streamline-curvature-induced migration, in which
polymers traveling along curved streamlines migrate towards the center of
curvature; and (4) depletion-convection coupling, in which depletion layers in
thin channels are convected across wide side chambers, creating a one-sided
diffusion barrier that leads to depletion from the side chamber. We use both
Stochastic Rotation Dynamics (SRD), which includes hydrodynamic interaction
(HI), and simple Brownian dynamics (BD), with HI omitted and flow field given
by finite element analysis. The similarity in results from SRD and BD at
Weissenberg number Wi less than 10 (where Wi is based on the shear rate in the
narrow region of the contraction channel) shows that HI (Mechanism 2) has only
a weak effect on polymer migration in our tight geometry. At Wi > 1, the
polymer migrates towards the centerline in the wide region, due mainly to
streamline-curvature-induced (SCI) migration (Mechanism 3), but also to
depletion-convection-induced migration (Mechanism 4). And we demonstrate these
two mechanisms more explicitly in a pressure-driven flow in a grooved channel
that is significantly wider than the polymer. SCI migration dominates in the
contraction geometry, and produces a migration velocity proportional to Wi2.
Using the central limit theorem, we accurately predict the position and width
of a band of polymer passing through N periodic
contractions, thereby demonstrating the potential for SCI migration as a
mechanism of size separation in a multi-step planar contraction channel. We
find that the best separation is achieved at Wi around 2, where SCI migration
has the greatest resolving power between polymers of different size. We also
find that sieving (Mechanism 1) is dominant at low Wi less than unity, where
the chains with large radius of gyration are delayed in their entry to the thin
channel, relative to shorter polymers. This sieving separation mechanism
differs from that of size-exclusion chromatography which yields faster
migration by the shorter chains. Our strategy of combining simulation methods
with the central limit theorem could also be used to predict separation
efficiencies of a wide variety of polymers and colloids in microfluidic
geometries.
Keywords : Stochastic Rotation Dynamics (SRD); Brownian dynamics (BD); Polymer
separation; Contraction flow
Adsorption of polyelectrolytes and
polyelectrolytes-surfactant mixtures at surfaces: a physico-chemical approach
to a cosmetic challenge Available online 6 June 2014
Sara
Llamas; Eduardo Guzmán; Francisco Ortega; Nawel Baghdadli; Colette Cazeneuve;
Ramón G. Rubio; Gustavo S. Luengo
Abstract :
The
use of polymer and polymer - surfactant mixtures for designing and developing
textile and personal care cosmetic formulations is associated with various
physico-chemical aspects, e.g. detergency and conditioning in the case of hair
or wool, that determine their correct performances in preserving and improving
the appearance and properties of the surface where they are applied. In this
work, special attention is paid to the systems combining polycations and
negatively charged surfactants. The paper introduces the hair surface and
presents a comprehensive review of the adsorption properties of these systems
at solid-water interfaces mimicking the negative charge and surface energy of
hair. These model surfaces include mixtures of thiols that confer various
charge densities to the surface. The kinetics and factors that govern the
adsorption are discussed from the angle of those used in shampoos and
conditioners developed by the cosmetic industry. Finally, systems able to
adsorb onto negatively charged surfaces regardless of the anionic character are
presented, opening new ways of depositing conditioning polymers onto keratin
substrates such as hair.
Keywords :Polymers;
Surfactant; Cosmetic; Surfaces; Hair
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