MICROSTRUCTURAL EVOLUTION IN POLYMERIZATIONS OF TETRAFUNCTIONAL MONOMERS

To characterize the network structural evolution during polymerizations of multifunctional monomers and predict the relationship between reaction conditions and polymer structure, a balanced approach between experimental characterization and simulation is used. A novel method for characterizing the free volume distribution and network structure throughout the polymerization is presented. This technique involves the use of photochromic probes that require a certain local, critical volume to isomerize. By incorporating probes that require different isomerization volumes, a distribution of local volume in the network is determined. Since this technique allows in situ monitoring of the volume distribution, the effects of conversion, rates of polymerization, and monomer structure on the free volume distribution can be elucidated. Volume distributions are presented for diethylene glycol dimethacrylate. Information from the photochromic technique is further supported by kinetic gelation model predictions and transmission electron microscopy pictures of the evolving polymer structure.