Self-Assembly of All-Conjugated Poly(3-alkylthiophene) Diblock Copolymer Nanostructures from Mixed Selective Solvents

The use of mixed selective solvents provides an effective means to control self-assembly of the all-conjugated diblock copolymer poly(3-butylthiophene)-b-poly(3-hexylthiophene) (P3BHT) into nanostructured morphologies. The solvent and temperature effects on the self-assembly of P3BHT during cooling and subsequent crystallization were explored for the first time. Depending on the poor/good solvent ratio (i.e., anisole/chloroform), P3BHT chains experience different kinetic pathways, yielding nanowires at a low anisole/chloroform ratio (<= 2:1), and nanorings coexisted with some nanowires at a high anisole/chloroform ratio (>= 6:1). The nanowires are formed as a direct consequence of strong interchain pi-pi stacking, while the formation of nanorings is governed by solvophobic interactions between conjugated blocks and the poor solvent anisole to minimize the unfavorable contacts between the P3BT block (similar to 50 degrees C) and later P3HT (below 35 degrees C) block and anisole.