固体1H-NMR表征玻璃态高分子链的缠结、互穿及链间邻近度

系统回顾了缠结定义的演化及对其表征的各种方法,比较了这些方法的特点和不足.在以往研究的基础上,发展了一套在分子尺度上表征玻璃态高分子链互穿的方法.该方法结合高速魔角和偶极滤波,用固体1H-NMR探测互穿区域的质子信号,表征了玻璃态聚苯乙烯的链互穿程度.该方法在0.5 nm尺度范围内测定了分子链间的距离,且与以往方法相比,该方法具有耗时短、需要样品量少、灵敏度和信噪比高等优点.

PROBING CHAIN ENTANGLEMENT, INTERPENETRATION AND PROXIMITY IN POLYMER GLASSES BY 1H SOLID STATE NMR

This paper reviewed the concept of chaim entanglement and the methods to characterize entanglement.A new 1H-NMR strategy was developed to characterize the degree of chain interpenetration in glassy polymers chain,which indirectly offer the information of entanglement.This strategy was run in the isotopically enriched polymer blends using dipolar filter under fast magic angle spinning.By this strategy we found the original degree of interpenetration of polymer chains in solution could be partly retained by freeze drying.It was also found that in the PS cast film,even when the molecular weight of PS was much less than its critical entanglement molecular weight(M_c),the PS chains interpenetrated heavily,in which Van der Waals interaction played an important role.