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Viscoelastic Properties of Chitosan with Different Hydration Degrees as Studied by Dynamic Mechanical Analysis
Author(s) -
Mano João F.
Publication year - 2008
Publication title -
macromolecular bioscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.924
H-Index - 105
eISSN - 1616-5195
pISSN - 1616-5187
DOI - 10.1002/mabi.200700139
Subject(s) - viscoelasticity , dynamic mechanical analysis , dynamic modulus , relative humidity , time–temperature superposition , glass transition , materials science , relaxation (psychology) , modulus , humidity , work (physics) , loss factor , composite material , thermodynamics , characterization (materials science) , superposition principle , polymer , nanotechnology , physics , psychology , social psychology , optoelectronics , quantum mechanics , dielectric
Dynamic mechanical analysis, DMA, is an adequate technique for characterizing the mechanical features of biomaterials, as one can use test conditions that can more closely simulate the physiological environments in which they are going to be applied. In this work it was possible to perform different tests on chitosan membranes using low/moderate hydration levels, as well in completely wet conditions. In the first case the data obtained at different relative humidity environments were rationalized under a time‐humidity superposition principle, where a master curve for the storage modulus could be obtained along a wide range of frequencies. The temperature dependence of the shift factors exhibited a curvature opposite to that expected by the WLF equation, and is consistent with relaxation dynamics behavior below the glass transition. Temperature scans above room temperature in both dry and wet conditions did not reveal strong variations in the viscoelastic properties. It was possible to follow in real time the water uptake in an initially‐dry membrane. During the initial strong and fast decrease of the storage modulus the loss factor exhibited a peak that should correspond to the occurrence of the glass transition resulting from the plasticization effect of water. Upon equilibration the loss factor reached similar values as for the dry material (tan δ ≈ 0.5). The viscoelastic characterization reported in this work for chitosan may be useful in the use of such material for a variety of biomedical applications.