All-Conjugated, All-Crystalline Donor Acceptor Block Copolymers P3HT-b-PNDIT2 via Direct Arylation Polycondensation

The synthesis and characterization of all conjugated, all-crystalline donor acceptor block copolymers (BCPs) containing poly(3-hexylthiophene) (P3HT) and poly{[N,ff-bis(2-octyldodecyOnaphthalene-1,4,5,8-bis-Br (dicarboximide)-2,6-diyll-alt-5,5'-(2,2'-bithiophene)} (PNDIT2) is presented. Direct arylation polycondensation (DAP) of dibromonaphthalenediimide and bithiophene is carried out in the presence of P3HT end-cappers to allow the in situ formation of BCPs P3HT-b-PNDIT2. As -prepared, well-defined H-P3HT-Br with hydrogen and bromine chain termini shows nonoptimal reactivity under the DAP conditions used. Therefore, H-P3HT-Br is converted into either H-P3HTTh (thiophene) or H-P3HT-Mes (mesitylene), giving a,co-hetero-C-H functionalized P3HT with modulated C-H reactivity. The influence of the different C-H chain termini of P3HT on the ability to act as end-capper and the resulting block structures is investigated in detail using wavelength-dependent size exclusion chromatography (SEC) and NMR spectroscopy. Different C-H reactivities of alpha,omega-hetero-C-H functionalized P3HT cause different contents of multiblocks, which in turn lead to varied degrees of crystallinity. These results show that careful tuning of C-H reactivity is a promising way to obtain well-defined, all-conjugated block copolymers via DAP.