Designing 100 K Glass Transition Breadths in Bulk Polymer Systems: Effects of Architecture in Homopolymers, Copolymers, and Copolymer Blends

Gradient copolymers have attracted interest as vibration or acoustic damping materials due to their extremely broad, tunable glass transition temperature (Tg) responses, up to 100 K in breadth. This behavior is caused by large compositional heterogeneity resulting from sinusoidal composition profiles in nanophase-separated systems. We have also found that some homopolymers and random copolymers exhibit large Tg breadths caused by incompatible main- and side-chain interactions. For example, the Tg response broadens with increasing side-chain length in the poly(n-alkyl methacrylate) series by more than a factor of 2 in going from poly(methyl methacrylate) to poly(n-hexyl methacrylate). We have also blended weakly-segregating styrene/n-butyl acrylate random copolymers of different compositions to allow for tunable Tg breadths over a 100 K temperature range. Finally, we have shown that blending a selective plasticizer into a styrene/4-vinylpyridine gradient copolymer results in a dramatic shift in the Tg response of a single nanophase region, increasing the Tg breadth above 100 K.