Effect of the graft ratio on the properties of polythiophene‐<i>g</i>‐poly(ethylene glycol)

Abstract

ABSTRACT Graft copolymers formed by anchoring poly(ethylene glycol) (PEG) chains to conjugated polythiophene have been prepared by copolymerizing two compounds: unsubstituted α‐terthiophene (Th 3 ) and a thiophene‐derived macromonomer having an α‐terthiophene conjugated sequence and one Th 3 bearing a PEG chain with molecular weight of 2000 as substitute at the 3‐position of the central heterocycle (Th 3 ‐PEG 2000 ). The grafting ratio of the resulting copolymers (PTh 3 * ‐ g ‐PEG), which were obtained using 75:25 and 50:50 Th 3 ‐PEG 2000 :Th 3 weight ratios, is significantly smaller than that of copolymers derived from polymerization of macromonomers consisting of a α‐pentathiophene sequence in which the central ring bears a PEG chain of M w = 2000 (PTh 5 ‐ g ‐PEG). The electroactivity and electrochemical stability of PTh 3 * ‐ g ‐PEG is not only higher than that of PTh 5 ‐ g ‐PEG but also higher than that of PTh 3 , the latter presenting a very compact structure that makes difficult the access and escape of dopant ions into the polymeric matrix during the redox processes. Furthermore, the optical π‐π * lowest transition energy of PTh 3 * ‐ g ‐PEG is lower than that of both PTh 5 ‐ g ‐PEG and PTh 3 . These properties, combined with suitable wettability and roughness, result in an excellent behavior as bioactive platform of PTh 3 * ‐ g ‐PEG copolymers, which are more biocompatible, in terms of cellular adhesion and proliferation, and electro‐compatible than PTh 5 ‐ g ‐PEG. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53 , 239–252