Induction of periodic nanostructures in polythiophene films through block copolymer templating

Abstract

A new class of periodically nanostructured polythiophene materials with high regularity and numerous morphologies is prepared through the cooperative self-assembly of polythiophene derivatives with a templating block copolymer (BCP) and poly(1,4-isoprene)-blockpoly(methacrylic acid) (PMA). The selection of the hydrophilic and aprotic triethylene glycol (TEG) group as side chains on polythiophene and the use of hydrophilic and protic PMA are crucial to producing well-ordered nanostructures in polythiophene films, as it enables selective coassembly within the hydrophilic domain through hydrogen bonding. The composite films are shown to have formed hexagonally packed cylinders with 28 nm periodicities based on small-angle X-ray scattering and transmission electron microscopy. The formation of hydrogen bonding is revealed by a shift in the carbonyl peak of PMA in the Fourier transform infrared spectra of the composite film relative to the neat film. This suggests that the TEG-functionalized polythiophene selectively incorporates into PMA.Recently, various methods have been suggested for creating nanostructures of π-conjugated polymer materials in a wide range of domain sizes. 7-9 Particularly, polythiophene derivatives have been investigated as representative π-conjugated polymers because of their superior charge carrier mobility, stability, and processability. 10,11 Ever since several substituted thiophene monomers were found to undergo living chain-growth polymerization, there has been a growing interest in the self-assembly of block copolymers (BCPs) composed of widely used polythiophene derivatives. 12 Although the self-assembly of polythiophene-based BCPs can be used to develop well-ordered nanostructures with tailorable morphologies and domain sizes, the rigid polythiophene backbone forms a rod-like structure that renders the controllability of the polythiophene-based so-called "rod-rod" BCP nanostructure difficult. [13][14][15] Another method for producing well-ordered nanostructures of π-conjugated polymers is to use the self-assembly of so-called "rod-coil" BCPs composed of rigid rod polythiophene and flexible coil polymers such as polystyrene-block-poly(3-hexylthiophene) (P3HT), poly(1,4-isoprene)-block-P3HT (PI-b-P3HT), 16 P3HT-block-poly(2-vinylpyridine) (P3HT-b-P2VP), 17 and P3HTblock-polylactide. [18][19][20] The introduction of the flexible coil block is expected to bring synergistic improvements in the mechanical, optoelectronic, and self-assembly properties for a wide variety of polythiophene derivatives. However, these rod-coil BCPs were synthesized using multistep polymerization techniques, which require the end functionalization of segments and additional purification of Additional supporting information may be found in the online version of this article.

Fabrication of Mesoporous Polyimide Composite Films by a Soft-Template Method Followed by Ozonolysis

“…PI-b-P2VP (M n = 37,000, PI 333 -P2VP 136 , M w /M n = 1.07) was synthesized via living anionic polymerization as described in the followed section 2.4 (Fig. 2) [45]. Phenolic resol was synthesized as described elsewhere [31,46].…”