Aggregation of Rigid Polymer Chains and Formation of Heterogeneous Structures During Bulk Radical Polymerization of Dialkyl Fumarates

ABSTRACT

Radical polymerization of dialkyl fumarates (DRF) as the 1,2‐disubstituted ethylene monomers affords poly(dialkyl fumarate)s (PDRF) with rigid poly(substituted methylene) structure. Bulk polymerization of DRF proceeds homogeneously or heterogeneously, depending on the structure of the ester groups. In this study, we clarified the relationship between the homogeneity/heterogeneity of bulk radical polymerization behavior of DRF and the structure of the ester alkyl groups, and revealed the formation process of the heterogeneous structure during the polymerization by optical microscopy and wide‐angle X‐ray scattering (WAXS) measurements. In the heterogeneous polymerization system, it was observed by optical microscopy that a small spherical structure was formed in the reaction solution. On the other hand, it was confirmed by the WAXS measurements that a unique aggregated structure with rigid PDRF chains was formed during the polymerization regardless of the homogeneity/heterogeneity of the system. The formation and evolution of the spherical structures were consistent with the development of a phase‐separated state during polymerization. The development of turbidity was accompanied by the formation of local intermolecular correlations among PDRF chains. Based on these experimental results, processes for the aggregated structure formation and the formation of heterogeneous structure during the bulk polymerization of DRF are discussed.