Tuning the transport dynamics of small penetrant molecules in glassy polymers

The effects of network structure of crosslinked poly(methyl methacrylate) (PMMA) discs on dynamic penetrant transport behavior were investigated through gravimetric integral sorption studies. Samples of P(MMA-co-(EG)(x)DMA) were synthesized via an iniferter-mediated, thermally-initiated free radical polymerization procedure to produce polymers with controlled variations in network structure by altering the comonomer feed ratios of dimethacrylate crosslinkers and changing the crosslinker interchain bridge length. The front velocity in the Case II transport regime was shown to scale directly with the square root of the crosslinking density over varied thermal and structural conditions, and increasing the crosslinker interchain bridge length moved the observed penetrant transport behavior towards the Fickian regime. The demonstrated ability to tune the dynamic transport behavior through modification of the polymer network structure holds promise as a means to mitigate solvent-induced material failure due to cracking and crazing encountered in many high-tech applications. (C) 2012 Elsevier Ltd. All rights reserved.