Photoresponsive property changes of polyethylacrylate membranes containing a spiropyran

Polyethylacrylate (PEA) polymers containing a spiropyran photochrome 1,1'-(alpha,alpha'-p-xylyl)-bis-[3,3-dimethyl-8-methacryloxymethyl-6-nitro-spiro(2H-1-benzopyran 2,2'-indoline)] "xylylene bis-DIPS" were fabricated into membranes. These membranes were used for separation in the dry state or were swollen in solvent for use in solution separation. The spiropyran undergoes photodissociation followed by molecular rearrangements that result in a net molecular volume reduction. The DIPS-PEA polymers contract 2--5% when irradiated with UV light (290--380 nm) followed by a further irradiation with visible light (lambda > 472) and swollen gels are expected to deswell by a larger percentage. This reversible photoresponse was used to control the membrane separation properties in real-time.; In gas separation studies the rubbery membranes were supported by a porous metal plate. For permanent gases that were studied, little or no changes were observed upon irradiation and all of the gases were characterized by low permeabilities that indicated the absence of high free volume in the polymer. Carbon dioxide, which plasticizes acrylate based polymers, had the highest permeability through the DIPS-PEA rubbery membranes. Photoirradiation also had no measurable effect on the dry DIPS-PEA physical properties such as crystallinity and density. This supports the small changes seen in permeability.; In solution studies, the DIPS-PEA did not form hydrogels, which limited its application. However, organogels with good mechanical properties were obtained in acetone and toluene. An increase in DIPS concentration resulted in an increase in the swelling ratios of nonirradiated polymer and an increased degree of deswelling upon irradiation. For the 0.5 mole % DIPS-PEA membranes there was a double fold increase in solubility of methyl orange and a 10--20% decrease in solubility sudan black B upon irradiation. The experimental permeabilities decreased by 24 times upon irradiation. This work showed that in solution studies both membrane shrinking and changes in membrane polarity controlled the permeability of both charged and neutral species and that modified Fickian models can be used to predict the species fluxes.