THE THERMAL DEGRADATION STUDIES OF GLYCIDYL METHACRYLATE COPOLYMERS

This research is concerned with the preparation, characterisation and thermal degradation of some copolymers containing the glycidyl methacrylate unit. The comonomers used along with glycidyl methacrylate (GMA) include styrene (ST), methyl methacrylate (MMA), and vinyl acetate (VAc).\ud \ud A general description of the major types of degradation processes which may occur during thermal decomposition is given in Chapter 1. The introductory chapter also reviews briefly the relationships between the chemical structure and thermal stability of vinyl polymers. A brief note on degradation techniques is also included.\ud \ud Chapter 2 summarises the experimental procedure of the several thermo-analytical techniques employed in the present work, with emphasis on thermal volatilisation analysis. A brief description of additional analytical methods used for characterisation and identification of polymers and degradation products is also included.\ud \ud Chapter 3 describes the preparation, isolation and characterisation of various homo - and copolymers of glycidyl methacrylate used in the present investigation. Analytical details are tabulated in the end of this chapter. Reactivity ratios for styrene - glycidyl methacrylate monomer pair is recalculated.\ud \ud The experimental work regarding the thermal aspects of various glycidyl methacrylate polymers and copolymers is described in Chapter 4,5,6 & 7.\ud \ud Chapter 4 is concerned, as a basis, with the thermal behaviour of high and low molecular weight glycidyl methacrylate polymers made by using different concentration of AIBN as initiator. It is observed that depolymerisation and ester decomposition proceed simultaneously during the thermal degradation of poly (glycidyl metbacrylate). It is proposed that monomer formation at lower temperature is due to initiation at unsaturated chain ends, whereas at higher temperature it is associated with initiation by random chain scission. It is also observed that the overall thermal stability of polymer increases with increasing molecular weight of poly (glycidyl methacrylate). The effect is attributed to the presence of less unsaturated chain ends in high molecular weight polymer.\ud \ud Chapter 5 details the thermal degradation of .GMA/ST copolymers. It is observed that the thermal stability of copolymers is intermediate between those of the individual homopolymers of ST and GMA. The presence of ST is found to have a disproportionate stabilising effect. A well separated two stage decomposition tends to merge in to a sharp single stage degradation, with increasing ratios of styrene monomer in the copolymer. An increase in T onset and T max is also observed with increasing ratios of styrene units in the copolymer. A mechanistic route has been proposed for the formation of various degradation products from the GMA/ST copolymers.\ud \ud In Chapter 6 studies of the thermal degradation of GMA/MMA copolymers are reported. The monomers remain the major products of degradation in the case of the copolymers, which, unlike the PMMA, also yield CRF products. An hydride rings are detected in the CRF and in the residue of partial degradation to 340°C. Glycidyl methylether is also present as one of the degradation product in GMA/MMA copolymers. The presence of the second monomer favours combination rather than disproportionation as the termination step.\ud \ud The thermal degradation of GMAN Ac copolymers is discussed in detail in Chapter 7. GMAN Ac copolymers display a new reaction not found in either of the homopolymers, the adjacent unit lactonization process. Features which particularly distinguish the behaviour of the copolymers from the homopoymers are (a) the low yield of GMA (b) the appearance of glycidylacetate as one of the major product