Shifting Electronic Structure by Inherent Tension in Molecular Bottlebrushes with Polythiophene Backbones

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• 作者：Yuanchao Li ; Alper Nese ; Xiangqian Hu ; Natalia V. Lebedeva ; Travis W. LaJoie ; Joanna Burdy艅ska ; Mihaela C. Stefan ; Wei You ; Weitao Yang ; Krzysztof Matyjaszewski ; Sergei S. Sheiko
• 刊名：ACS Macro Letters
• 出版年：2014
• 出版时间：August 19, 2014
• 年：2014
• 卷：3
• 期：8
• 页码：738-742
• 全文大小：376K
• ISSN：2161-1653

文摘

Bottlebrush macromolecules can be regarded as molecular tensile machines, where tension is self-generated along the backbone due to steric repulsion between densely grafted side chains. This intrinsic tension is amplified upon adsorption of bottlebrush molecules onto a substrate and increases with grafting density, side chain length, and strength of adhesion to the substrate. To investigate the effects of tension on the electronic structure of polythiophene (PT), bottlebrush macromolecules were prepared by grafting poly(n-butyl acrylate) (PBA) side chains from PT macroinitiators by atom transfer radical polymerization (ATRP). The fluorescence spectra of submonolayers of PT bottlebrushes were measured on a Langmuir鈥揃lodgett (LB) trough with the backbone tension adjusted by controlling the side-chain length, surface pressure, and chemical composition of a substrate. The wavelength of maximum emission has initially red-shifted, followed by a blue-shift as the backbone tension increases from 0 to 2.5 nN, which agrees with DFT calculations. The red-shift is ascribed to an increase in the conjugation length due to the extension of the PT backbone at lower force regime (0鈥?.0 nN), while the blue-shift is attributed to deformations of bond lengths and angles in the backbone at higher force regime (1.0鈥?.5 nN).