Dynamic mechanical thermal analysis (DMTA) is an accessible and versatile analytical technique where a sample is submitted to an oscillating stress or strain as a function of oscillatory frequency and temperature. Through this non-destructive measurement, a comprehensive understanding of the dynamic mechanical properties of polymers may be obtained. In this context, two series of polymers having different tacticity-dependent stereochemical microstructures have been submitted to controlled dynamo-mechanical strength. One series consists of three different PVC samples prior to and after substitution reaction to various extents in solution and in melt state. And one series consists of three commercial PMMA samples. In this review, we provide a straight correlation between β-relaxation and the content of mmr tetrads termini of isotactic sequences of at least one heptad in length, especially with those mmr structures taking the GTTG -TT conformation. Basically it is demonstrated that β-relaxation both, temperature and intensity, decrease with the content of the aforementioned microstructures, giving further support to the implication of magnitudes such as free volume and of coupling degree of the local motions in the mechanisms of the physicochemical processes responsible of the PVC and PMMA mechanical behaviors.
PVC, PMMA, β-relaxation, chain conformation, local motion, nucleophilic substitution, molecular microstructure, поливинилхлорид, полиметилметакрилат, релаксационный β-переход, конформация цепей, нуклеофильное замещение, молекулярная микроструктура
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