Thiophene–Vinylene–Thiophene-Based Donor–Acceptor Copolymers with Acetylene-Inserted Branched Alkyl Side Chains To Achieve High Field-Effect Mobilities

2-Alkyl(1)alkyl(2)-type aliphatic side chains with a branching point position at the C2-position (such as 2-ethylhexyl or 2-octayldodecyl) have been widely implanted into numerous donor–acceptor conjugated copolymers for solution processable transistors or organic solar cells. However, the tertiary branching site located at the second carbon inevitably imposes steric hindrance that twists the main-chain coplanarity and attenuates interchain interactions. In this research, we developed a new two-dimensonal thiophene–vinylene–thiophene (TVT) derivative where a carbon–carbon triple bond is inserted between the thiophene unit and the 2-octyldodecyl group. This acetylene-incorporated TVT (aTVT) was copolymerized with 5,10-di(thiophen-2-yl)naphtho[1,2-c:5,6-c′]bis([1,2,5]thiadiazole) (DTNT) and 5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTFBT) to form the polymers PaTVT-NT and PaTVT-FBT, respectively. PTVT-FBT, without the triple bond, was also prepared for comparison. The insertion of a line...