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Title: The synthesis of branched, vinyl functional polyacids via CCTP & their application to dual-cure dental materials
Author: Godfrey, Jamie
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2014
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This thesis details the synthesis of non-linear, acid functional polymers and their application to photo-curable polymer-inorganic dental composites. Many polyacids containing photopolymerizable groups used in current materials require multi-step synthesis and purification, due to the toxic solvents and reagents used. This work describes the synthesis of non-linear polyacids containing vinyl functionality that can be synthesized in a one step process, using non-toxic, aqueous media, as well as their subsequent testing in glass ionomer cements. Initial work in Chapter 2 set out to investigate the feasibility of synthesizing low molecular weight linear poly(methacrylic acid) (PMAA) via Catalytic Chain Transfer Polymerization (CCTP). The process was found to proceed efficiently, with good control over the molecular weight achieved by varying concentration of the chain transfer agent (CTA). Work then moved toward the incorporation of the less CCT-active acidic monomer, acrylic acid. It was found that the monomer reactivity ratios for the CCT copolymerization led to substantial compositional drift during the reaction and the formation of high molecular weight species. Additionally, multidetector size exclusion chromatography (SEC) analysis revealed the formation of non-linear polymer architectures, likely due to the CCT-derived vinyl group participating in propagation leading to an extent of grafting. The copolymerization of MAA with the difunctional monomer ethylene glycol dimethacrylate (EGDMA) was then investigated in two aqueous solvent systems. It was found that conducting the copolymerization in water led to a biphasic system at the outset of polymerization. This solvent system yielded a branched polymer of higher molecular weight and dispersity than analogous products synthesized in homogeneous solutions in water/IPA. The presence of a high level of vinyl functionality was confirmed using a bromination-titration methodology and the branched architecture revealed by multi-detector SEC. In Chapter 3, the linear and branched polyacids synthesized were then applied to dual-cure glass ionomer cements (GICs), a class of polymer-inorganic composite materials. A model photo-polymerizable GIC system was established via optimization of a three component, camphorquinone based photo-initiating system and investigation of the effect of additives and polymer concentration on the curing of the cement. This model system was used to investigate the influence of the polymer component on the final cement, with polymers of higher molecular weight generally leading to cements with greater compressive strengths. The resulting materials were characterized using a range of online monitoring techniques, including photo-DSC, photo-rheology and in situ FTIR, and the final cements’ compressive strength tested. Several methacrylate-modified PAAs were also synthesized in order to investigate the effect of photo-polymerizable functionality, and their properties compared to those of the linear and branched PMAA-based materials. It was found that the acrylic polymers led to cements with substantially higher compressive strengths than both the linear and branched methacrylic systems. However, the methacrylate-modified PAAs were found to give compressive strengths of similar magnitude to commercial materials, verifying that the relatively simple materials developed were an appropriate model system for this investigation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry