Polymer Structures and Their Glass Transition Temperatures: An Intriguing Relationship

Abstract:Polymer structure play an essential role in dictating chain stiffness and glass transition temperature (Tg). The characteristic ratio (C_∞) is an important parameter to describe chain stiffness. In general, polymers with stiffer chains have higher glass transition temperature and correspondingly higher C_∞.However, for poly(n-alkyl methacrylates), this is not always true. For example, poly(ethyl methacrylate) has Tg of 65 °C and C_∞ of 8.2, but poly(n-hexyl methacrylate) has Tg of -5 °C and C_∞ of 11.1. Furthermore, poly(n-alkyl acrylates) generally have lower Tgs than the corresponding poly(n-alkyl methacrylate) but actually have higher C_∞values. We believe other structural characteristics, such as stereoisomerism, might play a role in these discrepancies. In this contribution we discuss the intriguing relationships of polymer structure (chain stiffness) and glass transition temperatures with relation to structural parameters and solution properties of well-characterized poly(meth)acrylates.