کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5187249 | 1381124 | 2009 | 9 صفحه PDF | دانلود رایگان |
We recorded temperature-dependent high-resolution 13C NMR spectra of dry and swollen poly(acrylate)s [poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(tetrahydrofurfuryl acrylate) (PTHFA)] by dipolar decoupled-magic angle spinning (DD-MAS) and cross-polarization-magic angle spinning (CP-MAS) methods, to gain insight into their network structures and dynamics. Suppressed or recovered intensities (SRI) analysis of 13C CP-MAS and DD-MAS NMR was successfully utilized, to reveal portions of dry and swollen polymers which undergo fast and slow motions with fluctuation frequencies in the order of 108Â Hz and 104-105Â Hz, respectively. Fast isotropic motions with frequency higher than 108Â Hz at ambient temperature were located to the portions in which 13C CP-MAS NMR signals of swollen PMEA were selectively suppressed. In contrast, low-frequency motion was identified to the portions in which 13C DD-MAS (and CP-MAS) signals are most suppressed at the characteristic suppression temperature(s) Ts. Network of PMEA gels (containing 7Â wt% of water) turns out to be formed by partial association of backbones only, as manifested from their Ts gradient at lowered temperature, whereas networks of PHEMA (containing 40Â wt% of water) and PTHFA (9Â wt% of water) gels are tightly formed through mutual inter-chain associations of both backbones and side-chains, as viewed from the raised Ts values for both near at ambient temperature. It is also interesting to note that flexibility of gel network (PMEAÂ >Â PTHFAÂ >Â PHEMA) characterized by the suppression temperature Ts (PMEAÂ <Â PTHFAÂ <Â PHEMA) is well related with a characteristic parameter for biocompatibility such as the production of TAT (thrombin-antithrombin III complex) as a marker of activation of the coagulation system.
Journal: Polymer - Volume 50, Issue 25, 27 November 2009, Pages 6091-6099