Solid-state thermolytic and catalytic reactions in functionalized regioregular polythiophenes

(3-(2-(2-Tetrahydropyranyloxy)ethyl)thiophene) (THPET) was homopolymerized (PTHPET) and copolymerized with 3-hexylthiophene (PTHPET-co-3HT) to obtain functionalized regioregular pi-conjugated polymers. Thermolytic and catalytic removal of the bulky tetrahydropyran (THP) group from thin solid films of the polymers was studied. Thermolytic cleavage of the THP group occurs with a remarkably high yield in the solid state. Deprotection can be achieved catalytically in the presence of acids, at a significantly lower temperature. For PTHPET homopolymer, an increased degree of conjugation persists upon removal of the THP group. Copolymer films, however, exhibit a melting transition and a subsequent decrease in coplanarity at high temperatures. This disorder prevails upon cooling due to either strong interchain H-bonding or the absence of crystallizable side chains. When deprotection is carried out at lower temperatures, a high degree of pi-delocalization can be retained. The influence of composition on the reactivity of the polymers is described.