کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5191110 1381225 2005 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Toward an understanding of thermoresponsive transition behavior of hydrophobically modified N-isopropylacrylamide copolymer solution
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Toward an understanding of thermoresponsive transition behavior of hydrophobically modified N-isopropylacrylamide copolymer solution
چکیده انگلیسی
Poly(N-isopropylacrylamide-co-vinyl laurate)(PNIPAAm-co-VL) copolymers were prepared at various feed ratios via conventional radical random copolymerization. The formation, composition ratios and molecular weight of copolymers were examined. The thermoresponsive behaviors of PNIPAAm and PNIPAAm-co-VL solutions at low and high concentrations were intensively investigated by turbidity measurement, Micro-DSC, temperature-variable state fluorescence, 1H NMR and dynamic light scattering (DLS). Several important results were obtained that (1) incorporation of PVL results in much lower and broader LCST regions of the copolymer solutions, and facilitates the formation of hydrophobic microdomains far below LCST, causing a pronounced aggregation in solutions (2) temperature-variable 1H NMR spectra shows that during the phase transition, the 'penetration' of PNIPAAm into the hydrophobic core is a process accompanied with a transition of isopropyl from hydration to dehydration as well as a self-aggregation of hydrophobic chains at different temperature stages (3) according to the 1H NMR spectra of polymer solutions obtained at varied temperatures, the microdomains from hydrophobic VL moieties have a different accessibility for isopropyl groups and the entire chains during phase transition (4) temperature-variable DLS demonstrates that the temperature-induced transition behavior of copolymers is supposedly divided into three stages: pre-LCST aggregation (<20 °C), coil-globule transition at LCST (20-25 °C) and post-LCST aggregation (>25 °C).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 46, Issue 14, 27 June 2005, Pages 5268-5277
نویسندگان
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