Polydimethylsiloxane modified chitosan. Part III: Preparation and characterization of hybrid membranes |
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Authors: | Daniela Enescu Viorica Hamciuc Rodinel Ardeleanu Mariana Cristea Aurelia Ioanid Valeria Harabagiu Bogdan C. Simionescu |
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Affiliation: | 1. Departament of Macromolecules, “Gh. Asachi” Technical University, 700050 Iasi, Romania;2. “Petru Poni” Institute of Macromolecular Chemistry, Department of Inorganic Polymers, 41A Aleea Grigore Ghica Voda, 700487 Iasi, Romania |
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Abstract: | The paper deals with the synthesis of organic–inorganic hybrid membranes, Hy, obtained by simultaneous grafting and crosslinking of chitosan with epoxy-terminated polydimethylsiloxane and γ-glycidoxypropyltrimethoxysilane. Porous membranes, HyP, were also obtained by acid decomposition, at different temperatures (25 and 50 °C), of calcium carbonate porogenic agent trapped inside the material. As proved by electron and atomic force microscopy, the non-porous membrane is a phase segregated material with spherical domains (10–40 μm) of silica core covered by hydrophobic siloxane in a hydrophilic chitosan matrix. The porous membranes showed different morphologies with irregular circular pores of 10–30 μm diameters for the membranes obtained at lower temperature, while the membranes prepared at 50 °C tend to adopt a plan-parallel porosity. The water contact angles of hybrid membranes (78°) and pure chitosan membranes (72°) indicated a lower hydrophilic character of modified chitosan. As a result of the crosslinking and of increased hydrophobicity, the hybrid membranes were characterized by a smaller water swelling degree (about 30%) as compared to pure chitosan membrane (700%). However, the presence of the pores in HyP membranes determined an increase of the water adsorption (maximum swelling degree, about 100%). The hybrid membranes possess a slightly higher thermal stability as compared to chitosan (first initial decomposition temperature, 147 and 175 °C for chitosan and hybrid membranes, respectively), but a lower one as compared to pure polydimethylsiloxane. The high storage modulus of chitosan (about 5.1 × 109 Pa at 20 °C) is decreased by about one order of magnitude by the introduction of the highly flexible polysiloxane and the hybrid membranes are more flexible. |
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