Mass transfer and phase equilibrium characteristics of crosslinked polymers
Polymers may be functionalised via the introduction of crosslinks between adjacent polymer chains, yielding three-dimensional macromolecular networks. The resulting crosslinked polymers are of considerable interest when applications such as protective films and membranes for separation purposes or fuel cells are concerned. Fundamental insight into both sorption characteristics and mass transfer mechanisms is required for this class of materials in order to assess and evaluate the polymers’ respective performance.
Phase equilibrium and mass transfer are studied by means of Micro-Raman-Spectroscopy considering physically crosslinked poly(vinyl alcohol). As a semicrystalline polymer, PVA is not fully ordered, but contains crystallites embedded in an amorphous phase.
Figure 1: Structure of the PVA network with crystallites acting as physical crosslinks.
PVA films are readily prepared and their performance may be customised by the systematic introduction of crystallites via thermal treatment. These acting as crosslinks, both mechanical properties and solvent resistance are greatly enhanced with increasing degree of crystallinity. Thus, with crosslinked polymers, particular attention must be paid to the characterization of the macromolecular network as polymer microstructure has a potential bearing on both phase equilibrium and mass transfer parameters.
The results of this study are expected to contribute to the understanding and modelling of mass transfer processes in crosslinked polymers.
Figure 2: Experimental setup for the determination of phase equilibrium data via Micro-Raman-Spectroscopy and water vapour sorption isotherm for physically crosslinked PVA membranes at T = 25°C.
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