Effect of degree of crosslinking on water transport in polymer microparticles

The water transport in microparticles of poly(2‐hydroxyethyl methacrylate) crosslinked with small amounts of ethylene glycol dimethacrylate was investigated as a function of time. Dynamic swelling curves were obtained and analyzed with a simple, empirical, exponential expression, where the exponent n indicates the mechanism of water transport. It was determined that the mechanism changed from Fickian to non‐Fickian transport as the nominal crosslinking ratio increased from X = 0.007 to X = 0.124 mol EGDMA/mol HEMA. Smaller particles attained their equilibrium swelling value faster. The velocity of the penetrant front was determined with optical microscopy, and it was found to decrease from 22.2 to 11.2 μm/min as the crosslinking ratio increased.