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Title: Poly(alkyl methacrylate-co-acrylic acid) copolymers of varying architecture for improved adhesion
Author: Canning, Sarah
ISNI:       0000 0004 5366 4134
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2015
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Amphiphilic copolymers composed of hydrophilic polyacrylic acid segments and hydrophobic poly(alkyl methacylate) segments were targeted as adhesion-promoting additives for use in printing inks. Methyl, butyl and lauryl methacrylates were chosen to vary hydrophobicity. Initially, a phase transfer-catalysed backbone functionalisation and a reversible addition-fragmentation chain transfer (RAFT)-controlled grafting step were employed to form graft copolymers, although polyacrylic acid homopolymer was also produced. The lauryl methacrylate synthesis proved more difficult due to the steric effect of the long alkyl chain. Branched and linear poly(alkyl methacrylate-acrylic acid) copolymers were then synthesised using RAFT, in either a one-pot polymerisation, producing random copolymers, or a two-step procedure forming block copolymers. Molecular weights of close to 20 000 g mol-1 were achieved, with methacrylate:acrylic acid ratios close to 1:1, as targeted. Branching was confirmed through calculation of Mark-Houwink parameters using GPC with viscometric detection, and a 13C NMR method was developed to identify block or random monomer sequence distribution. Due to their amphiphilic nature, the copolymers were found to self-assemble in water to form macromolecular structures. These varied according to architecture, monomer distribution, and hydrophobicity of the methacrylate segment. Small angle neutron scattering was used to study the copolymers in a range of solvent systems. Whilst Gaussian coils were formed in d-THF and self-assembled spheres or multi-lamellar micelles were formed in D2O, the copolymers were found to aggregate into fractal structures in intermediate solvency conditions. The behaviour of the copolymers when coated on polyolefin substrates was studied by contact angle measurements, and the random materials created more polar surfaces compared to the segmented analogues. A force spectroscopy technique showed potential for accurate comparison of copolymer adhesion. Ink formulations containing the butyl methacrylate copolymers jetted well on both thermal inkjet and drop on demand printers. Adhesion was assessed using industry standard tests, and better overall performance was observed for the branched copolymers.
Supervisor: Rimmer, Stephen ; Geoghegan, Mark ; Reynolds, Stuart Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available