Fully Conjugated Graft Copolymers Comprising a P-TypeDonor–Acceptor Backbone and Poly(3-hexylthiophene) Side ChainsSynthesized Via a “Graft Through” Approach.

A series of fully conjugated graftcopolymers containing poly(3-hexylthiophene)(P3HT) side chains and a p-type carbazole-diketopyrrolopyrrole (CbzDPP)donor–acceptor backbone were synthesized via a graft throughSuzuki polymerization. The macromonomers were formed by externallyinitiating P3HT growth from a boronic ester-functionalized carbazolevia Kumada catalyst transfer polycondensation. Subsequently, thismacromonomer was copolymerized with a DPP monomer via a graft throughSuzuki polymerization to yield the final graft copolymers. The graftcopolymers exhibit optical and electronic properties of both P3HTand the CbzDPP polymers independently due to the break in conjugationbetween the carbazole unit and P3HT chain. Moreover, these propertiesreflect the relative proportion of P3HT and CbzDPP polymers; shorterP3HT chain lengths lead to graft copolymers that possess more CbzDPPcharacter and vice versa. The macromonomers were characterized bygel permeation chromatography, mass spectrometry, and UV–visiblespectroscopy. The graft copolymers were further investigated usinggel permeation chromatography, UV–visible spectroscopy, cyclicvoltammetry, differential scanning calorimetry, and atomic force microscopy.Finally, organic field effect transistors were fabricated using thegraft copolymers and compared to an analogous linear CbzDPP copolymer.Ultimately, the graft copolymers with the longest P3HT chains (ca.75 repeat units) exhibited almost exclusively P3HT characteristics,possessing a small CbzDPP internal charge transfer (ICT) peak andonly p-type conductivity (μh∼ 6 × 10–4cm2V–1s–1). Conversely, the graft copolymers with the shortest P3HT chains(ca. 10 repeat units) showed significant CbzDPP character, includinga strong ICT peak and ambipolar mobilities (μh∼5 × 10–3cm2V–1s–1; μe∼ 7 × 10–4cm2V–1s–1). [ABSTRACT FROM AUTHOR]