Molecular design and modification for polymeric semiconductors
File(s)
Author(s)
Wang, Simeng
Type
Thesis
Abstract
Besides being lightweight, flexible and cheap, one of the major attractions of plastic electronics is that they can be chemically modified to cater a broad range of applications. By changing the chemical structures of the molecule, the physical properties and in turn the device performance of the materials can be tuned accordingly. Though there are limited systematic ways to precisely determine the behaviour of an organic semiconductor based on its structure, chemists have learned to adjust the properties of a material based on well-understood functional groups or building blocks.
This thesis demonstrates four applications of strategic designs of novel structures and the modifications of the existing materials. By simply changing the branch point of an alkyl solubilising group on naphthalene diimide – bithiophene (NDI-T2) polymer can result in a 5-fold increase in its OFET performance. By using a new type of acetonitrile alkylation reaction, a highly solubilising group – super-branch was synthesised. With the super-branch, we were able to synthesise a NDI polymer with six unsubstituted thiophenes as the donor. Through the use of random co-polymerisation with a short chain NDI, we have successfully improved the super-branch polymer’s electron mobility by 3 orders of magnitude to 0.11 cm2 / Vs, comparable to N2200. The post-polymerisation modification on PEGylated polymer was realised by a nucleophilic aromatic substitution to replace a fluoro group on the polymer. A series of fluorinated benzotriazole polymers was also successfully synthesised to offer a relatively high hole mobility of 0.50 cm2 / Vs.
This thesis demonstrates four applications of strategic designs of novel structures and the modifications of the existing materials. By simply changing the branch point of an alkyl solubilising group on naphthalene diimide – bithiophene (NDI-T2) polymer can result in a 5-fold increase in its OFET performance. By using a new type of acetonitrile alkylation reaction, a highly solubilising group – super-branch was synthesised. With the super-branch, we were able to synthesise a NDI polymer with six unsubstituted thiophenes as the donor. Through the use of random co-polymerisation with a short chain NDI, we have successfully improved the super-branch polymer’s electron mobility by 3 orders of magnitude to 0.11 cm2 / Vs, comparable to N2200. The post-polymerisation modification on PEGylated polymer was realised by a nucleophilic aromatic substitution to replace a fluoro group on the polymer. A series of fluorinated benzotriazole polymers was also successfully synthesised to offer a relatively high hole mobility of 0.50 cm2 / Vs.
Version
Open Access
Date Issued
2018-10
Date Awarded
2019-02
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Heeney, Martin
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)