Free radical polymerization of methyl methacrylate up to the glassy state. Rates of propagation and termination

The free radical polymerization of methyl methacrylate in bulk at 0 deg C initiated by photochemical decay of azobis(cyclohexanenitrile) (ACN) is tested over the full range of conversion up to the glassy state. Rate constants of propagation, k sub p , and termination, k sub t , are evaluated by the rotating sector technique and after effect. Instantaneous degree of polymerization and efficiencies, f, are given for all conversions. The conversion dependence of f can be expressed by the self-diffusion of small molecules in a polymer matrix. Both rate constants depend on the conversion; k sub t for conversions near and beyond the onset of entanglement also depends on the chain length of the polymer radicals, but becomes independent of this length at approx 45% conversion. The diffusion processes describing the different stages of conversion are discussed. 19 ref.--AA