The relation between the polymerization rates and swelling coefficients for copolymers obtained by photoinitiation

Copolymers of HEMA/HDDMA were obtained by photoinitiation in the presence of substituted thioxanthones and different amines, and the polymerization rates were measured by Fourier-transform infrared spectroscopy (FTIR). The swelling of films of these copolymers was determined by chloroform absorption. A good inverse relationship was found between the swelling and the polymerization rates. The production of more initiating radicals, which accelerate the polymerization processes, also induces a higher degree of crosslinking, conferring more rigidity to the polymer material and preventing larger solvent absorption and swelling. From the time evolution of the solvent uptake (n-values ∼0.5) it can be deduced that the swelling process is controlled by the diffusion in the polymer network.