کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5182559 1380992 2013 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
New insights on the crystallization and melting of cyclic PCL chains on the basis of a modified Thomson-Gibbs equation
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
New insights on the crystallization and melting of cyclic PCL chains on the basis of a modified Thomson-Gibbs equation
چکیده انگلیسی

Low polydispersity linear and cyclic poly(ε-caprolactone) with molecular weights of 2-7.5 kg/mol were synthesized. Differences in the morphology of cyclic and linear single crystals (obtained from solution at identical temperatures) indicate that cyclic PCL crystals were obtained at higher supercoolings than linear ones. Cyclic PCL crystals (both crystallized from solution and from the melt) exhibited higher melting point values (Tm) than analogous linear PCL lamellae. In addition, cyclic PCLs crystallize from the melt at higher rates than linear PCLs at identical crystallization temperatures. Results showed that cyclic PCLs possess a higher equilibrium melting point (Tm0) than linear PCL crystals. A modified Thomson-Gibbs equation and a modified Hoffman-Weeks equation have been derived in this work to demonstrate that the higher Tm0 of the cyclic polymer stemmed from the negative cyclization entropy associated with the absence of chain ends and the more collapsed conformation of the cyclic chain in the melt state.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 54, Issue 2, 24 January 2013, Pages 846-859
نویسندگان
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