Effect of Block Sequence in All-Conjugated Triblock Copoly(3-alkylthiophene)s on Control of the Crystallization and Field-Effect Mobility

Abstract

Despite recent impressive advances in synthesis of all-conjugated diblock copolymers via facile quasi-living Grignard metathesis (GRIM) polymerization, it remains challenging to achieve well-defined all-conjugated triblock copolymers of interest. Herein, we report the judicious design and synthesis of a series of all-conjugated triblock copoly­(3-alkylthiophene)­s consisting of poly­(3-butylthiophene) (P3BT), poly­(3-hexylthiophene) (P3HT), poly­(3-octylthiophene) (P3OT), or poly­(3-dodecylthiophene) (P3DDT) in all 12 possible combinations. The effects of block sequences and the length of alkyl side chains on their cocrystallization and microphase-separated structures are investigated. Moreover, the correlation between different crystalline structures and charge mobilities in organic field-effect transistors (OFETs) is scrutinized. These rationally synthesized triblock copoly­(3-alkylthiophene)­s self-assemble into cocrystals with an edge-on orientation in as-cast and 150 °C-annealed samples. Remarkably, the combinations with the shortest alkyl side chains placed as the central block (i.e., P3HT-b-P3BT-b-P3OT, P3HT-b-P3BT-b-P3DDT, P3OT-b-P3BT-b-P3DDT, and P3OT-b-P3HT-b-P3DDT) exhibit higher film crystallinity and charge mobilities than the other two combinations where the blocks with shortest alkyl side chains are located at two terminals. Intriguingly, upon thermal annealing near the melting temperature of these combinations, P3BT-b-P3OT-b-P3HT, P3BT-b-P3DDT-b-P3OT, and P3HT-b-P3DDT-b-P3OT can retain their cocrystalline structure while the other combinations are found to microphase separate. Finally, the all-conjugated triblock copoly­(3-alkylthiophene)­s with proper block sequence demonstrate stable charge mobilities at high temperatures and good flexibility in OFET devices. Taken together, this study elucidates that the block sequence is of key importance on control of the crystallization and charge transport behavior of poly­(3-alkylthiophene)-based triblock copolymers.

Unravelling the Correlation between Microphase Separation and Cocrystallization in Thiophene-Selenophene Block Copolymers for Organic Field-Effect Transistors

“…Recently, we have reported reversible phase transition between forms I and II in P3HS thin films treated by alternating thermal and solvent vapor annealing and the cocrystals of poly­(3-butylhexylthiophene)- block -poly­(3-hexylselenophene) (P3BT- b -P3HS) for high-performance organic field-effect transistors (OFETs). Furthermore, we have extended the cocrystals to triblock copoly­(3-alkylthiophene)­s and explored the effect of block sequence on their crystalline and charge transport behavior . However, as an important member in the P3AS family, the relation between crystalline structures of poly­(3-butylselenophene) (P3BS) and their charge transport properties has not yet been reported due to its synthesis difficulty and poor solubility in common organic solvents.…”

“…Furthermore, we have extended the cocrystals to triblock copoly(3-alkylthiophene)s and explored the effect of block sequence on their crystalline and charge transport behavior. 28 However, as an important member in the P3AS family, the relation between crystalline structures of poly(3-butylselenophene) (P3BS) and their charge transport properties has not yet been reported due to its synthesis difficulty and poor solubility in common organic solvents. Thus, it is challenging to do film deposition for the fabrication of thin film devices.…”

Synthesis and Conductivity Studies of Poly(Methyl Methacrylate) (PMMA) by Co-Polymerization and Blending with Polyaniline (PANi)

“…It was found that the stability of the triblock copolymers under visible light irradiation at ambient temperature was improved by the addition of PANi block [127]. It was also reported by the previous literature that the triblock copolymer has better control of the on-chain orientation and thus is able to give an improvement in the produced conjugated polymers properties [60]. Table 7 summarizes the advantages and disadvantages of the copolymerization and blending methods.…”

“…An acid dopant is usually used during the synthesis of PANi to improve its conductivity. One of the most common dopants used is hydrochloric acid (HCl) [60,61]. Sulphuric acid (H 2 SO 4 ) is another acid dopant that is used as an alternative to HCl in the PANi synthesis.…”

Improved Self-Assembly of P3HT with Pyrene-Functionalized Methacrylates

“…Many rod-coil block copolymers that consist of P3HT are reported to exhibit good optoelectronic properties. Rod-coil diblock and triblock copolymers with P3HT were synthesized using Grignard metathesis polymerization (GRIM) and other living polymerization techniques. − The synthesis of rod-rod block copolymers with P3HT was performed by attaching a liquid crystalline block to P3HT. There are a few recent reports based on the synthesis of all conjugated block copolymers based on P3HT or a block copolymer with liquid crystalline blocks attached to P3HT. , Stefan’s group reported P3HT block copolymers comprising poly­(γ-benzyl- l -glutamate) and poly­( N -hexylisocyanate). , In another report, Lin and co-workers had demonstrated the synthesis of a P3HT- b -poly­(3-butylthiophene) diblock copolymer with greatly improved crystallinity and electrical conductivity upon solvent annealing .…”