電子顯微鏡在解析高分子結晶結構與行為上的應用

The Application of Transmission Electron Microscopy on the Study of Polymer Crystal Structure and Growth Mechanism

阮至元(Jrjeng Ruan)

《科儀新知》 160期 (2007/10) Pp. 18-27

https://doi.org/10.29662/IT.200710.0002

摘要

長鏈高分子的有序相有著豐富的規則排列與形成機制，但許多可能影響聚集與結晶行為的因素均尚待瞭解。而解析高分子在晶相中的排列與分子構形，可以對探討長鏈分子如何聚集及參與結晶，有很大的幫助。本文所報導的研究，即是利用所獲得的單晶電子繞射，重新認識了聚烯烴分子P4MP之Form II晶相，發現其分子排列應較原先依據X-ray及NMR光譜的瞭解，有著更低的對稱性。這一較不常見的低對稱性分子排列，事實上反映出adjacent reentry之chain folding方式對結晶成長的影響。

並列摘要

Fruitful ways of molecular packing in the ordered phases formed by long-chain molecules are directly linked to various applications that can be possibly developed from soft materials. However, due to the complicated natures of long-chain molecules, it is frequently met that many mechanisms able to influence and govern molecular assembly and crystallization behavior still wait to be further investigated and learned. The studies on the packing of polymer provide the possibility to reveal the knowledge at molecular level, which might be elusive for other techniques, about how these longchain molecules continuously join into the crystalline phase or other types of ordered phases. Reported in this article, single crystal diffraction pattern of Form II crystalline modification of poly-4-methyl-pentene-1 (P4MP) obtained by TEM surprisingly helps to decipher an unusual monoclinic structure, which has lower symmetry than what have been previously learned based on X-ray powder and NMR spectrums. It is suggested that this lower symmetry of Form II results from conformational restrictions set by chain folding on the stem chirality and clinicity of helical polyolefins, and this structural analysis is well consistent with the single crystal growth habit (preferred ac growth planes). And the adjacent-reentry mechanism should be adopted in the crystal growth.