Brush Polymer of Donor-Accepter Dyads via Adduct Formation between Lewis Base Polymer Donor and All Carbon Lewis Acid Acceptor.

Yang Wang,Travis Bailey,Eugene Chen,Miao Hong

doi:10.3390/molecules22091564

Abstract

A synthetic method that taps into the facile Lewis base (LB)→Lewis acid (LA) adduct forming reaction between the semiconducting polymeric LB and all carbon LA C60 for the construction of covalently linked donor-acceptor dyads and brush polymer of dyads is reported. The polymeric LB is built on poly(3-hexylthiophene) (P3HT) macromers containing either an alkyl or vinyl imidazolium end group that can be readily converted into the N-heterocyclic carbene (NHC) LB site, while the brush polymer architecture is conveniently constructed via radical polymerization of the macromer P3HT with the vinyl imidazolium chain end. Simply mixing of such donor polymeric LB with C60 rapidly creates linked P3HT-C60 dyads and brush polymer of dyads in which C60 is covalently linked to the NHC junction connecting the vinyl polymer main chain and the brush P3HT side chains. Thermal behaviors, electronic absorption and emission properties of the resulting P3HT-C60 dyads and brush polymer of dyads have been investigated. The results show that a change of the topology of the P3HT-C60 dyad from linear to brush architecture enhances the crystallinity and Tm of the P3HT domain and, along with other findings, they indicate that the brush polymer architecture of donor-acceptor domains provides a promising approach to improve performances of polymer-based solar cells.

Highlights

Poly(3-hexylthiophene) (P3HT) is a widely used electron-donating material in polymer-based organic photovoltaics (OPVs), thanks to its high hole mobility (~0.1–1 cm2 V−1 s−1 ), a band gap of ~1.9 eV, and solution processability [1,2]. These OPV devices are typically based on a bulk heterojunction (BHJ) fabricated from a blend of a donor, typically a conjugated polymer such as P3HT, and an acceptor, typically a fullerene such as C60 and its derivatives
To improve the performance of such OPV devices, intense research has focused on optimizing the morphology of the donor/acceptor active layers, controlling the phase separation between the electron-donating and electron-accepting components, and improving the ordered assembly of the two components in the active layers
Using the combined “graft through” and radical polymerization method, macromer P3HT-(CH2 )3 -VIM was successfully polymerized into a novel brush polymer, P[P3HT-(CH2 )3 -VIM], comprising a poly(vinyl imidazolium) backbone and P3HT side chains

Summary

Introduction

Poly(3-hexylthiophene) (P3HT) is a widely used electron-donating material in polymer-based organic photovoltaics (OPVs), thanks to its high hole mobility (~0.1–1 cm V−1 s−1 ), a band gap of ~1.9 eV, and solution processability [1,2]. Molecules 2017, 22, 1564 limitation of a linear donor polymer and fulfill the diverse requirements in organic electronic devices, polymer structures have focused on the engineering of copolymers having block, graft, or branched architectures [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. There are several methods to obtain brush polymers containing the P3HT side chains, including “grafting to” methods to graft P3HT to silicon surface and “click reaction” to link P3HT to a polymer main chain [15,16,17,18,19]; “grafting from” method to graft the P3HT chains on poly(4-bromostyrene) and poly(4-vinylpyridine)-block-poly(4-iodo-styrene) by Kumada catalyst-transfer polycondensation [20,21]; and “grafting through” method, known as the macromer method, to synthesize brush polymers of P3HT via ring-opening metathesis polymerization of the macromers containing the P3HT moiety [22,23]

Methods

Results

Conclusion