Synthesis, Cocrystallization, and Microphase Separation of All-Conjugated Diblock Copoly(3-alkylthiophene)s

A series of all-conjugated diblock copoly(3-alkylthiophene)s with varying alkyl chain length, poly(3-butylthiophene)- b -poly(3-hexylthiophene) (P3BT−P3HT), poly(3-butylthiophene)- b -poly(3-dodecylthiophene) (P3BT−P3DDT), and poly(3-hexylthiophene)- b- poly(3-dodecylthiophene) (P3HT−P3DDT), were synthesized by modified Grignard metathesis polymerization. The obtained diblock copoly(3-alkylthiophene)s have well-controlled block ratios and molecular weights with narrow polydispersity indices. The diblock copoly(3-alkylthiophene)s comprised by the blocks with the alkyl side-chain length different by two carbon atoms (represented by P3BT−P3HT) have the ability of cocrystallizing into an uniform crystal domain, with the mutual interdigitation of the different side chains of the two blocks into a common interchain lamella. Other diblock copoly(3-alkylthiophene)s with the side chains different by more than two carbon atoms prefer to microphase separating into two crystal domains formed by the independent crystallization of each block. The AFM images revealed the characteristics of microphase-separated morphology in P3BT−P3DDT and P3HT−P3DDT diblock copoly(3-alkylthiophene)s.