Effect of solvent-dependent viscoelastic properties of chitosan membranes on the permeation of 2-phenylethanol

Abstract

a b s t r a c tThe 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.

Chitosan Membranes Exhibiting Shape Memory Capability by the Action of Controlled Hydration

“…For 0 vol% of water, pure ethanol, values of E′ of 0.35 GPa were found, which are very similar to the data found in dry chitosan [12], indicating that, at this composition of ethanol, CHT is in a glassy state. In a previous work, Caridade et al [13] reported that no absorption was detected for 100 vol% ethanol in swelling experiments. When water started to be introduced in the ethanol bath, the values of E′ decreased continuously.…”

“…This peak around 35 vol% is in accordance with the water content above which the Young's modulus reaches a plateau, mentioned before ( Figure 2). This peak is attributed to the glass transition (T g ) of chitosan, whereby it passes from a glass to rubber-like state transition that is induced by the entrance of water in the chitosan matrix [13]. Such water content can be seen as an external variable that may control the molecular mobility of the polymeric structure.…”

“…CHT can be processed into devices with a variety of shapes using different processing techniques to be used in tissue engineering and other biomedical applications [10,11]. Previous studies showed that CHT can undergo a glass transition by the action of hydration [12,13]. Therefore, we hypothesize that the occurrence of a T g in CHT activated by hydration variation could be used in the production of devices with shape memory, which could find interest in the biomedical field.…”

Nacre‐Inspired Biomaterials

“…Indeed, if a stress normal to the platelet plane is applied, a viscoelastic dissipative process will take place mainly in the hydrated state [2] and the ductile organic fraction that glues the crystals will prevent an uncontrolled crack growth [50]. Regarding the transition from a brittle (glassy) state to a more elastomeric behavior that occurs on nacre's hydration, a similar behavior was observed in chitosan using nonconventional dynamic mechanical analysis, in which glass transition could be detected in intermediate hydration levels [51,52]. Moreover, photoacoustic Fourier transform infrared spectroscopy results suggest that the water present at the nanograin interfaces also contributes significantly to the viscoelasticity of nacre [53,54].…”

Biomimetic design of materials and biomaterials inspired by the structure of nacre

“…This viscoelastic dissipative process takes place mainly in the hydrated state, and dry nacre behaves very much similar to pure aragonite because the organic material becomes brittle (Barthelat 2007). The transition from a brittle (glassy) state to a more elastomeric behaviour was observed in a polysaccharide (chitosan) upon hydration using non-conventional dynamic mechanical analysis, in which a glass transition could be detected in intermediate hydration levels (Mano 2008;Caridade et al 2009). Photoacoustic Fourier transform infrared spectroscopy results suggest that the water present at the nanograin interfaces also contributes significantly to the viscoelasticity of nacre (Mohanty et al 2006;Verma et al 2006).…”