Abstract
A series of copolymers of diethyl vinylphosphonate and styrene have been prepared in order to determine the conditions of preparation required to produce copolymers having given characteristics of phosphorus-content and intrinsic viscosity. The variation of these factors and the degree of conversion with change of initiator concentration, temperature of polymerisation, and initial mole ratio of the reactants has been studied. These changes have been expressed graphically and indicate that (a) increase of initiator concentration decreases the intrinsic viscosity of the products and also the degree of conversion to the resultant copolymers, but has little effect on their phosphorus-contents (b) an increase in the temperature of polymerisation causes a decrease in the intrinsic viscosity and has a non-linear effect on the percentage conversion and phosphorus-contents and (c) an increase in the molar concentration of styrene in the initial reaction mixture leads to an increase in the number of these units which enter the copolymer, and increases the intrinsic viscosity and percentage conversion. The monomer reactivity ratios for styrene (M[1]) and diethyl vinylphosphonate (M[2]) have been determined and are found to be: r[1]= 3.25 and r[2] = 0, the graphical method of Mayo and Walling being employed. The influence exerted by the phosphonic ester group on the course of the copolymerisation, by way of electronic and steric effects, is discussed in the light of these values. A selected number of the copolymers have been subjected to light-scattering measurements, whereby the weight-average molecular weights have been determined. These values have been correlated with intrinsic viscosity determinations - a linear relation between the logarithms of the viscosity and molecular weight being obtained; the constants k and a in the Houwink expression relating molecular weight and viscosity being thereby evaluated for this system. A copolymer containing 50% by weight of diethyl vinylphosphonate has been hydrolysed and a preliminary survey of its viscosity properties has been made at various hydrogen ion concentrations and at differing degrees of dilution.