A comb-like alternating copolymer of thiophene and hydroxyalkylthiophene: synthesis and characterization

The synthesis and characterization of an alternating copolymer formed by thiophene and alkylated thiophene obtained by means of Ni (Yamamoto method) and Pd (Suzuki coupling) is reported here. The side chain of the alkylated monomer contains a tetrahydropyranyl group which can be removed leaving the --OH function free. The copolymers obtained with the two different synthetic procedures are almost equivalent, with the exceptions that the one prepared using Pd has a strictly alternating structure, while the copolymer from Ni contains some enchainment irregularities, hence a rigorously alternating structure is not reached. The copolymer from Pd has been characterized in its deprotected form by XRD analysis and DSC. When the protective groups are removed, interchain hydrogen bond formation occurs, leading to a structure exhibiting a certain degree of order (at least bidimensional) with a high melting point. Graphite-like interchain spacing (3.5 Å) observed after annealing is indicative of a very planar backbone.