کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5189744 | 1381191 | 2006 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Characterization of pH-dependent micellization of polystyrene-based cationic block copolymers prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization
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موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی آلی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
A series of block copolymers composed of a fixed length of an (ar-vinylbenzyl)trimethylammonium chloride (Q) block (the number average degree of polymerization of the Q block, DPn,Q=57) and varying lengths of an N,N-dimethylvinylbenzylamine (A) block (the number average degrees of polymerization of the A blocks, DPn,A, ranging 11-50) were prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization, and their pH-dependent micellization was characterized by potentiometric titration, 1H NMR spectroscopy, dynamic and static light scattering, and fluorescence techniques as a function of the A block length. At pH<5.5, the A block is fully protonated, and hence the block copolymers act as a simple polyelectrolyte, dissolving molecularly in acidic water. At pH>7, the A block becomes deprotonated, and thereby the block copolymers aggregate into a micelle composed of hydrophobic microdomains formed from the deprotonated A blocks. Results of light scattering and fluorescence measurements indicated that the micellization behavior depended strongly on the length of the A block. The number of polymer chains comprising one micelle (i.e. mean aggregation number, Nagg) increased from 3 to 12 as DPn,A increased from 11 to 50 at pH 10.0. In the case of a random copolymer of Q and A with an A/Q molar ratio similar to that of a block copolymer with DPn,A=50, Naggâ¼1 (i.e. unimolecular micelle) was confirmed by static light scattering at pH 10.0.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 47, Issue 12, 31 May 2006, Pages 4333-4340
Journal: Polymer - Volume 47, Issue 12, 31 May 2006, Pages 4333-4340
نویسندگان
Yoshiro Mitsukami, Akihito Hashidzume, Shin-ich Yusa, Yotaro Morishima, Andrew B. Lowe, Charles L. McCormick,