ipso-Arylative Ring-Opening Polymerization as a Route to Electron-Deficient Conjugated Polymers

Area of Science:

• Polymer Chemistry
• Organic Electronics
• Materials Science

Background:

• Polythiophenes are crucial in organic electronics.
• Tuning side chains is key to controlling polymer properties.
• Developing new synthetic routes for functional polythiophenes is ongoing.

Purpose of the Study:

• To synthesize novel polythiophenes using ipso-arylative ring-opening polymerization.
• To investigate the influence of specific aryl ketone side chains on polymer properties.
• To evaluate the potential of these polymers as n-type organic semiconductors.

Main Methods:

• Ipso-arylative ring-opening polymerization of functionalized indeno[2,1-b]thiophene monomers.
• Characterization of polymer molecular weight (M_n) and properties.
• Measurement of frontier orbital energy levels (HOMO/LUMO) and charge carrier mobilities.
• Density functional theory (DFT) calculations.

Main Results:

• Polymers with M_n up to 9 kg/mol were synthesized.
• Pendant aroylphenyl side chains were successfully incorporated.
• Poly(3-(2-(4-hexylbenzoyl)phenyl)thiophene) showed lower HOMO/LUMO levels (-5.9/-4.0 eV) than poly(3-hexylthiophene).
• Significantly higher electron mobility (2×10^-3 cm²/Vs) than hole mobility (8×10^-6 cm²/Vs) was observed.
• DFT calculations indicated backbone distortion influences charge mobility.

Conclusions:

• The synthesized polythiophenes possess tunable electronic properties due to side-chain engineering.
• The observed high electron mobility suggests suitability for n-type organic semiconductor applications.
• Side-chain steric effects on backbone conformation are critical for charge transport.