Synthesis and electronic properties of poly (3-hexylthiophene)-based semiconducting polymers

The overall goal of this research was developing novel semiconducting materials with tunable physical and electrical properties for potential use as flexible electronics. Poly(3-hexylthiophene) is one of the most investigated semiconducting polymers due to its good optical and electrical properties. The nature of dielectric gate insulator is one of the key factors that can affect the outcome of mobility measurements. Here we report the effect of surface treatment of SiO2 on the electrical properties of poly(3-hexylthiophene). Bottom-contact organic field effect transistors were fabricated with octyltrichlorosilane (S1), hexylmethyldichlorosilane (S2), and benzyltrichlorosilane (S3) modified SiO2 gate dielectric and poly(3-hexylthiophene) as the active layer. A mobility of 10-3 cm2/V s was estimated for the device treated with silane S1 and mobilities in the order of 10 -2 cm2/V s were measured for both S2 and S3 treated device. From contact angle measurements, S2 showed the most hydrophobic surface while S3 generating less hydrophobic surface compared to S1.;The synthesis and characterization of a di-block copolymer containing regioregular poly(3-hexylthiophene) and elastomeric poly(tetrahydrofuran) is presented. Hydroxypropyl-terminated poly(3-hexylthiophene) was subjected to chemical modification to generate end groups amenable for ring-opening cationic polymerization of tetrahydrofuran. This macroinitiator was used for the cationic ring-opening polymerization of tetrahydrofuran. 1H NMR and SEC data confirmed the formation of poly(3-hexylthiophene)-b-poly(tetrahydrofuran) di-block copolymer with an estimated mobility value of 8.9 x 10-3 cm2/V s.;By expanding the new synthetic method we have developed, cationic ring-opening polymerization of 2-ethyl-2-oxazoline. Here we synthesized amphiphilic rod-coil di-block copolymers that can self-assemble into micellar aggregates which can complex with CdSe quantum dots for organic/inorganic hybrid solar cells. The hydroxypropyl terminated poly(3-hexylthiophene) precursor was reacted with trifluoromethanesulfonic anhydride in the presence of 2,6-di- tert-butylpyridine resulting in the functional initiator intermediate used for ring-opening polymerization of 2-ethyl-2-oxazoline. 1H NMR and SEC confirmed the successful formation of di-block copolymers containing 5, 15 and 30 mol% poly(2-ethyl-2-oxazoline). UV-Vis spectra of solutions of di-block copolymers showed solvatochromic behavior. Field-effect mobility of the diblock copolymers was evaluated and was found to be in the order of 10-5-10-6 cm2/. AFM images of all the diblock copolymers showed the formation of distinct nanowire morphology with different order of packing.