Well-Defined ABA Triblock Copolymers Containing Carbazole and Ethynyl Groups: Living Anionic Polymerization, Postpolymerization Modification, and Thermal Cross-Linking

Abstract

A block copolymer that can be thermally cross-linked is synthesized by copolymerization of N-phenyl-2-vinylcarbazole (A) and trimethyl(2-(4-vinylphenyl) ethynyl)silane (B), followed by a deprotection reaction (d-PBAB). A t riblock copolymer containing carbazole and (trimethylsilyl)ethynyl groups (PBAB) is first prepared using potassium naphthalenide in tetrahyrdofuran at -78℃for 60 min. Well-controlled poly(A) and PBAB can be obtained under the conditions employed in this anionic block copolymerization. The well-defined d-PBAB with thermally cross-linkable ethynyl group is then prepared by the deprotection of the trimethylsilyl group from PBAB without side reactions. The thermal cross-linking behavior of d-PBAB is investigated using thermogravimetric analysis and differential scanning calorimetry. The d-PBAB is cross-linked under different conditions, and it is observed that the d-PBAB film heated at 250℃for 60 min shows excellent solvent resistance and increased film density. In addition, the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of cross-linked d-PBAB are estimated to be -5.09 and -1.57 eV, respectively.