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Synthesis, Relaxation Dynamics and Rheology of Supramolecular Polymers

Cui, Guanghui (2017) Synthesis, Relaxation Dynamics and Rheology of Supramolecular Polymers. PhD thesis, University of Leeds.

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Abstract

A supramolecular polymer is a complex assembly of molecules held together by noncovalent bonds, such as hydrogen bonding, host-guest interactions or coordinative bonds. The last few decades great developments have been made in the research and application of supramolecular polymers, and a wide variety of supramolecular polymers have been prepared. These supramolecular polymers have been applied within many application areas, especially for medical applications such as drug or DNA delivery into living cells, and controlled drug release. However, many fundamental aspects such as the relaxation dynamics and rheological properties over a wide temperature range as well as the detailed structure-properties relationships are still not well understood for supramolecular polymers. This thesis addresses this, and aims at a better understanding of how the supramolecular interactions affect the structure, relaxation dynamics and rheological properties of different supramolecular polymer systems over a wide timescale or temperature range ranging from the glassy to the melt states. The goal is to determine the structure-property relationships, and to provide guidelines for the design and synthesis of new supramolecular polymers. In this thesis, the dynamics of four different supramolecular polymers are investigated. The first system is based on a comb-like polymeric backbone of poly(2-ethylhexyl acrylate) (PEHA) to which a random distribution of 2-ureido-4[1H]-pyrimidinone (UPy) supramolecular side-groups are added. A series of polymers with varying side-group UPy contents have been synthesised using the reversible addition fragmentation chain transfer (RAFT) polymerization. The second system is based on poly(propylene glycol) (PPG) for which the chain ends were functionalised using supramolecular hydrogen-bonding UPy-groups. The unfunctionalized PPG is a viscous liquid at room temperature whereas the end-functionalised UPyPPG is a rubbery material due to the formation of long extended chains formed through multiple hydrogen bonds. For this supramolecular polymer system, we have investigated two possible application areas: (i) the use of blends of PPG and UPyPPG with lithium salts in polymer electrolytes for Li-ion batteries and (ii) the use together with UV curable components for self-healing coatings. The third system is based on hydroxyl-capped polytetrahydrofuran (PTHF) with varying molecular weights and the fourth is a set of alkane diols of different chain-length. For both these systems, intermolecular supramolecular hydrogen bond interactions via the chain-ends will become more important for shorter chains. Generally, the relaxation dynamics, thermodynamic response and rheological response were determined using a range of experimental techniques, including broadband dielectric relaxation spectroscopy, differential scanning calorimetry (both in the standard and modulated mode), shear and extensional rheology and nuclear magnetic resonance relaxometry.

Item Type: Thesis (PhD)
Academic Units: The University of Leeds > Faculty of Maths and Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds)
Identification Number/EthosID: uk.bl.ethos.733584
Depositing User: Mr. Guanghui Cui
Date Deposited: 19 Feb 2018 12:45
Last Modified: 11 Apr 2020 09:53
URI: http://etheses.whiterose.ac.uk/id/eprint/19373

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