Mechanical properties and structures under the deformation of thiophene copolymers with cyclic siloxane units

Abstract

Polythiophene is a typical semiconductive conjugated polymer; however, thiophene conjugated systems suffer from low flexibility. Although flexible polythiophene with siloxane side chains has been investigated, control of the cross-linking points remains to be achieved. Herein, thiophene copolymers with cyclic siloxane side chains were synthesized and the cross-linking points were controlled by a ring-opening reaction and the reduction of tetrathiophene-substituted cyclic siloxane cross-linkers. The obtained thiophene copolymer network possessed higher glass transition temperatures, larger Young's moduli and strengths, and lower strains at breaking. These behaviors are attributed to the formation of the cross-linking points. In addition, in situ X-ray diffraction measurements during cyclic tensile tests confirmed that the recovery of the crystallite orientation, which corresponded to the macroscopic deformation of the polythiophene network, was better than that of the thiophene copolymer without a network structure.