PVPh/PEO共混物动力学演化过程的NMR研究

Dynamic Evolution in PVPh/PEO Blend Studied by Solid-State NMR

聚合物共混物中链段的慢取向运动与其玻璃化转变行为和宏观力学性质密切关联,而基于化学位移各向异性重聚的^(13)C CODEX(centerband-only detection of exchange)固体核磁共振(SSNMR)技术能够有效表征共混物中链段的慢取向运动.该文利用^(13)C CODEX NMR技术详细研究了相容性聚合物共混物聚乙烯基苯酚/聚氧乙烯(PVPh/PEO)中的刚性组分PVPh在较宽温度范围内的慢取向运动特性与玻璃化转变过程的关联.研究表明,在玻璃化转变起始温度以下,PVPh主链的分子运动被冻结,而侧基存在b-松弛的慢取向运动;在玻璃化转变起始温度附近,PVPh主链具有明显的慢取向运动,而且主链和侧基是一种协同的分子运动.该文利用NMR技术揭示了共混物中的玻璃化转变起止温度分别对应于高分子主链慢取向运动CODEX信号的开始和极大值处的温度.

The ^（13）C centerband-only-detection-of-exchange（CODEX） variable-temperature solid-state NMR（SSNMR） technique was used to investigate the evolution of segmental dynamics in poly（vinyl phenol）（PVPh）/ poly（ethylene oxide）（PEO） polymer blend within a wide range of temperatures. It was found that the glass transition began with the emergence of remarkable slow motions of the PVPh backbone segments, and ended when the CODEX signal intensity of segmental slow motion reached maximum. The SSNMR results revealed, at molecular level, that the onset and endpoint of conventional calorimetric glass transition are closely associated with the evolution of slow motions in this polymer blend.