Relationships between Architectures and Properties of Highly Branched Polymers: The Cases of Amorphous Poly(trimethylene carbonate) and Crystalline Poly(ε-caprolactone)

Highly branched polymers (HBPs) are a special class of functional polymeric materials and possess unique properties due to their unique topological structure. A new series of highly branched linear-comb and star-comb amorphous poly(trimethylene carbonate)s (PTMC) and crystalline poly(epsilon-caprolactone)s (PCL) with well-defined structure and high molecular weight were first synthesized using hydroxylated polybutadiene (HPB) as macroinitiators by simple one-step and graft from strategies. It is expected that the impact of long-chain, highly branched architecture on the properties of amorphous and crystalline polymers, respectively, is different. We explored systematically for the first time the effect and comparison of branched architectures on the physical and chemical properties of highly branched PTMCs and PCLs, including the intrinsic viscosity, glass transition, thermal degradation, creep property, rheological property, and crystallization and melting behaviors. It is found that the intrinsic viscosities in solution for both comb-branched PTMCs and PCLs were much lower compared with their linear and star counterparts arise from more compact structure and smaller hydrodynamic volumes. For amorphous PTMC, the creep strain and rate increased remarkably with degree of branching increasing due to the shorter side chains making it difficult for the highly branched molecules to entangle. For crystalline PCL, both WARD and DSC analysis of PCLs with different topological structures indicated that the comb branched architectures have no significant influence on the crystal structure of PCL, but greatly promote the crystallization behavior, e.g., higher crystallinities. The deep understanding of structure-property relationship expects to guide the synthesis of designed functional polymer materials and the processing of polymer products.