Effect of solvent-dependent viscoelastic properties of chitosan membranes on the permeation of 2-phenylethanol
Caridade, S. G. | Silva, Ricardo M. P. da | Reis, R. L. | Mano, J. F.
The viscoelastic behaviour of chitosan was followed by dynamic mechanical analysis (DMA) while the sample was immersed in gradient compositions of water/ethanol mixtures. The swelling equilibrium of chitosan membranes, both crosslinked with genipin or not, increased linearly with the water content. Increasing the water content, it was simultaneously observed a peak in the loss factor (around 25 vol.%) and a reduction of the storage modulus, which was attributed to the a-relaxation of chitosan. This was the first time that the glass transition dynamics in a polymer was monitored in immersion conditions where the composition of the plasticizer in the bath is changed in a controlled way. The water content at which tan d presented a maximum increased with both increasing frequency and increasing crosslinking density. The permeability decreased steadily with the ethanol content, reaching very low values around the glass transition. Therefore we hypothesize that conformational mobility of the polymeric chains may play an important role in the diffusion properties of molecules trough polymeric matrices.
Показать больше [+] Меньше [-]This work was partially supported by the Portuguese Foundation for Science and Technology (FCT), through funds from the POCTI and/or FEDER programmes and through the scholarship SFRH/BPD/34545/2007 granted to Ricardo M.P. da Silva. This work was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283) and also partially supported by the EU funded projects HIPPOCRATES (STREP - NMP3-CT-2003-505758) and PROTEUS (INTERREG III A - SP1.P151/03). The technical assistance of Ana Pinheiro in the execution of the DMA experiments is also acknowledged.
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