Synthesis and characterization of graft polymethacrylates containing conducting diphenyldithiophene for organic thin-film transistors

Abstract

A class of [5,5′]-diphenyl-[5,5′]-dithiophene (PTTP)-modified methacrylates has been synthesized and free radically polymerized to form graft polymethacrylates with the conducting PTTP segments as pendant side chains. Both the terminal alkyl side chain and spacer between the PTTP segments and polymer backbone could be varied to study fundamental structure–property relationships for this class of materials. Specifically, a group of three different PTTP graft polymethacrylates has been successfully synthesized with the alkyl side chain varying from hexyl to dodecyl. For the dodecyl-terminated poly(4-(5′-(4-dodecylphenyl)-[2,2′-bithiophen]-5-yl)phenethyl methacrylate), p(DPTTPEM), a counterpart, poly(4-(5′-(4-dodecylphenyl)-[2,2′-bithiophen]-5-yl)phenbutyl methacrylate), p(DPTTPBM), where the ethyl spacer was replaced by a butyl group, was synthesized. The experimental results indicated that both the alkyl side chain and spacer significantly affected the reactivity of the PTTP-modified methacrylates during free radical polymerization as well as the physical properties of the resultant graft polymers including solubility, morphology, and electrochemical and electrical properties. Typical field-effect mobilities on the order of 10−5 cm2 V−1 s−1 were observed for all the PTTP monomers in air, which was attributed to their crystalline phase as revealed by differential scanning calorimetry and X-ray diffraction studies. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012