HIGHLY SWOLLEN RUBBERY NETWORK IN A GLASSY POLYMER PARTICLE

Fluorescence measurements were carried out on poly(vinyl acetate) particles, prepared by dispersion polymerization in isooctane using a copolymer of 2-ethylhexyl methacrylate [EHMA] and 2-isocyanatoethyl methacrylate as a steric stabilizer These reactive particles were treated with 2-(1-naphthyl)ethanol to produce particles labelled specifically in the stabilizer phase. Energy transfer experiments were carried out first on the N-labelled particles doped with a hydrocarbon soluble anthracene derivative which dissolved exclusively in the rubbery PEHMA phase. Donor fluorescence decay profiles were measured, and the data were fitted to the Klafter Blumen model for energy transfer on fractal. The finding that the effective dimensionally dBAR = 2 for this energy transfer process is interpreted in terms of a crossover in a restricted geometry if the PEHMA is present in the form of interconnected long thin (30 angstrom diameter) cylinders. Supporting this idea is our finding that swelling agents for PEHMA, such as hexadecane, are also taken up by the particle from pentane solution. Experiments on these particles give dBAR values that increase with increasing hexadecane until dbAR becomes equal to 3.0. Further swelling measurement were performed with cyclohexane as swelling agent. We found that energy transfer kinetics obeyed a Stern-Volmer type of relation in highly swollen. non-restricted PEHMA phase.