Spin probe studies of nonsolvent penetration into polymer particle formed from poly(vinyl acetate) and poly(2‐ethylhexyl methacrylate)

Abstract

AbstractNonaqueous dispersion (NAD) of poly(vinyl acetate) (PVAc) particles sterically stabilized by poly(2‐ethylhexyl methacrylate) were examined by ESR spectroscopy after introduction of a trace quantity of a spin probe, 3‐carbomoyl‐2,2,5,5‐tetramethyl 3‐pyrolin‐1‐yloxy. ESR spectra were monitored as a function of temperature from ‐160 to 100°C. In spite of the complex morphology of the particle, it is found that the behavior of the probe in the NAD was essentially identical to that in a pure PVAc matrix. Solvent penetration into (NAD) particles were studied. These colloidal particles were exposed to a dilute solution of the spin probe, and the bimodal distribution of the ESR spectra of this probe molecule were carefully monitored as a function of time. Fickian‐type diffusion of spin probes into the particles was observed and a spherical model was employed to obtain the diffusion coefficients (D) in various solvents. D values were found around 10–15 cm2/s and were interpreted as the parameter, inversely proportional to the apparent viscosity of the environment inside the PVAc particle. The maximum amount of diffused solvent molecules (M∞) into the PVAc particle was found inversely proportional to polymer‐solvent interaction through the solubility parameters. © 1993 John Wiley & Sons, Inc.