Longitudinal acoustic modes of polytetrafluoroethylene copolymers and oligomers
Longitudinal acoustic modes of polytetrafluoroethylene copolymers and oligomers
复制标题
聚四氟乙烯共聚物和低聚物的纵向声模
DOI：
10.1016/0032-3861(77)90290-7
复制
发表时间：
1977
期刊：
影响因子：
4.6
通讯作者：
B. Fanconi
中科院分区：
文献类型：
--
作者：
J. Rabolt;B. Fanconi
在全氟正构烷烃和四氟乙烯-六氟丙烯无规共聚物（TFE-HFP）中观察到了拉曼主动纵声模（LAM）。低频带被发现在熔融和固相的低聚物，和他们的比较表明，定期扩展的螺旋构象存在于熔融相的全氟正构烷烃低于n-C12 F26。发现共聚物的片层长间距与由LAM频率计算的片层长间距之间有很好的一致性。正常模式的计算，使用现有的力场，已经进行了无限的均聚物（PTFE）和n-C16 F34。发现螺旋反转型链缺陷不影响喇曼光谱的频率和强度。
Raman active longitudinal acoustic modes (LAM) have been observed in the perfluoro n-alkanes and in a random copolymer of tetrafluoroethylene and hexafluoropropylene (TFE-HFP). Low frequency bands were found in both the melt and solid phases of the oligomers, and their comparison indicates that regular extended helical conformations exist in the melt phase of perfluoro n-alkanes below n-C12F26. Good agreement is found between the lamellar long spacings of the copolymer and that calculated from theLAMfrequencies. Normal mode calculations, using available force fields, have been performed on the infinite homopolymer (PTFE) and n-C16F34. It was found that the helix reversal type of chain defect does not affectLAMfrequencies and intensities.