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The effects of pressures up to 3000 atmospheres on the polymerisation of styrene, systems containing styrene with vinylidene chloride, technical and trans-dichloroethylene, or trichloroethylene; and of systems containing vinyl acetate with vinylidene chloride or trichloroethylene have been investigated. Rates of reaction have been measured. Composition and limiting viscosity number of the polymers have been determined.

The effect of pressure on the free radical and ionic polymerisation of seven cyclic ethers has been studied up to 12,500 atm. Benzoyl peroxide was most frequently used as the free radical initiator. Boron trifluoride diethyl etherate was used as the ionic initiator for the polymerisation of tetrahydrofuran, 3,3'-bis (chloromethyl)-oxacyclobutane and 1,3,5-trioxane; and a complex of ferric chloride with propylene oxide or styrene oxide for the ionic polymerisation of propylene oxide and styrene oxide, respectively.

The thesis describes the effects of pressure from 1 to 4,400 atm. on the kinetics of polymerisation of acenaphthylene, and its copolymerisation with methyl methacrylate and with maleic anhydride. The rates of homopolymerisation were measured in toluene, benzene and carbon tetrachloride, with azobisisobutyronitrile (AIBN) as initiator at 60°C., and were found to be proportional to [1]0.62 and [M]0.9 at 1 atm. This result is interpreted in terms of degradative chain transfer involving the abstraction of a hydrogen atom from the naphthalene ring of the monomer, the resulting radical being resonance-stabilised.

The melting point-pressure relationship for three disubstituted ethylene compounds has been determined tc within 40 atmospheres. The melting pressures at 60° C. of these substances are: ethyl cinnamate, 2900 atmos.; diethyl fumarate, 3680 atmos.; and a-methylstyrene, 3700 atmos. The free radical polymerisations of ethyl cinnamate and diethyl fumarate have been studied in detail, particularly in the region of the freezing pressures. Previous research on a-methylstyrene polymerisation was verified in part, but the reported value of the freezing pressure of this compound at 60° C. was found to be in error. Some physical properties of polymers, especially molecular weights, have been determined and the pressure effect on these properties is discussed. A few experiments with ethyl crotonate are recorded. The overall volume of activation, AV*, has been determined for each reaction, the values being: ethyl cinnamate, - 54.0 cc./mole; diethyl fumarate, -14.7 cc./mole; and a-methylstyrene, -18.4 cc./mole. In the case of ethyl cinnamate, the reaction is complicated by a phase separation which accounts for the very high value of HIV* observed. The molecular weights were found to behave sigmoidally with pressure for all three compounds. This behaviour with a-methylstyrene is in disagreement with a previous study, but closely follows the behaviour of styrene. There was no discontinuity in the molecular weights of these three polymers in the vicinity of the liquid-solid phase boundary.

The object of the work described in this thesis was to study the effect of pressure on chain transfer to the solvent, tetradhloroethylene, in the polymerisation of styrene; and to investigate whether tetrachloroethylene copolymerisas with styrene. The rate of polymerisation in this solvent is found to be of half order with respect to initiator concentration and of order 3/2 with respect to monomer concentration. Pressure has an accelerating effect on the rate of polymerisation of styrene in tetrachloroethylene, and increases it 5 to 6—fold in the pressure range 1 to 2680 atmospheres. The molecular weight of polystyrene prepared in solution increases up to about 1030 atmospheres, beyond which there is no pronounced change up to 3000 atmospheres. However, in experiments with mole ratios of solvent to monomer > 3.04 the molecular weights are almost constant up to 2680 atmospheres.