Hierarchically ordered ABA triblock copolymer with large difference in glass transition temperatures of the two blocks

Rod-coil-rod triblock copolymers, poly[4′-(methoxy)-2-vinylbiphenyl- 4-methyl ether] -blockpolydimethylsiloxane-block-poly[4′-(methoxy)-2- vinylbiphenyl-4-methyl ether] (PMVBP-b-PDMS-b-PMVBP), were synthesized by nitroxide-mediated radical polymerization, and their hierarchically ordered structures were studied. A difunctional TEMPO macroinitiator was first synthesized by the hydrosilylation reaction between hydride-endcapped PDMS and allylic alkoxyamine. The polymerization of the monomer MVBP was triggered by the macroinitiator, resulting in a series of triblock copolymers. The molecular weights and polydispersity indexes were determined by gel permeation chromatography. Differential scanning calorimetry results demonstrate that the triblock copolymers exhibit two glass transition temperatures (-120 °C and 160 °C) that are markedly different. As revealed by small-angle X-ray scattering and transmission electron microscopy experiments, the triblock copolymers self-assemble into hierarchical structures with the liquid crystalline phase of PMVBP in the lamellar structures.