Molecular motions in poly(diethyl siloxane) studied by solid-state29Si NMR |
| |
Authors: | V M Litvinov A K Whittaker A Hagemeyer H W Spiess |
| |
Institution: | (1) Institute of Synthetic Polymer Materials, Academy of Sciences, Moscow, UdSSR;(2) Present address: Max-Planck-Institut für Polymerforschung, Mainz, F.R.G. |
| |
Abstract: | Molecular motions in poly(diethyl siloxane) were studied by solid-state29Si-NMR in the temperature range 180–350 K. In this temperature range two solid phases
1 and
2, a mesophase
m, and an amorphous isotropic phase exist. The nature of the chain mobility in the different phases was deduced from the resulting changes in the NMR line-shape governed by anisotropic chemical shift. In the intermediate solid phase
2 its anisotropy is reduced by 25% compared with the low temperature phase
1 due to the onset of oscillations around the chain axis and conformational transitions. In the mesophase
m the polymer chain rotates about its long axis yielding an axially symmetric chemical shift tensor opposite in sign to that in the
1,
2 phases. The broad transition of the mesophase into the isotropic phase is accompanied by an increase in a narrow Lorentzian line arising from the amorphous phase. The results are compared with previous1H NMR, Raman-spectroscopy and x-ray measurements.After completion of this work we learnt that PDES has recently also been studied through13C-MAS and29Si-NMR by Möller et al. 13]. |
| |
Keywords: | Poly(diethyl siloxane) molecularmotions NMR temperatureinfluence differentphases chainmobility |
本文献已被 SpringerLink 等数据库收录! |
|