Star block copolymer POEGMA-b-P3HT enables tunable charge transport in organic field-effect transistors

Abstract

Conjugated polymers are widely recognized for their potential in advanced optoelectronic applications due to their tunable electrical and optical properties. Integrating a conjugated polymer with a star-shaped, non-conducting polymer matrix introduces unique physical and optoelectronic characteristics driven by architectural control. Based on this concept, we synthesized and explored star-shaped conjugated block copolymers composed of four-arm poly(oligo (ethylene glycol) methacrylate) (POEGMA) and linear poly(3-hexylthiophene) (P3HT). The star-shaped POEGMA cores were synthesized via atom transfer radical polymerization using a tetrafunctional initiator, pentaerythritol tetrakis(2-bromoisobutyrate). Separately, the alkyne-terminated P3HT was prepared through Kumada catalyst-transfer polymerization. The two polymer segments were then conjugated via copper(I)-catalyzed azide–alkyne cycloaddition, affording well-defined POEGMA-b-P3HT block copolymers with star-like architecture. Comprehensive structural characterization was conducted using nuclear magnetic resonance spectroscopy, gel permeation chromatography, and Fourier-transform infrared spectroscopy. The optoelectronic properties and surface morphology of the resulting materials were systematically investigated in the solid state. The star block copolymer POEGMA-b-P3HT exhibited isotropic behavior in thin films, along with a well-defined spike-like morphology. The resulted optical behavior and morphology is associated with ambipolar transistor characteristics, indicating that the P3HT segment retained its properties effectively within the star-shaped architecture. These findings demonstrate that the star-shaped molecular design significantly influences the optical properties, underscoring its potential for application in ambipolar organic field-effect transistors.