Properties of modification chitosan

• Main Authors: Huang-Shian Tsai, 蔡皇仙
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/50752197858912081697

博士 === 雲林科技大學 === 工程科技研究所博士班 === 96 === There are four parts included in the work, concentration the preparation of various sulfonation degree sulfonated chitosan (SCS) and crosslinked sulfonated chitosan (GASCS) membranes first. Second part of this work was about introduced binary croslinked agents of hydrophilic chitosan network membranes (GASSACS). Third part of this work related to the synthesis Octa[3-propylglycidylether] dimethylsiloxy] petacycloctasilanae (OG) was synthesized as the crosslinked agent for the preparation of organic-inorganic hybrid chitosan network nanocomposite membranes. Eventually, the pervaporation separation performance for 90wt% ethanol aqueous dehydration of the above network membranes was studied. For Part I investigation, chitosan (CS) is modified by propane sultone via a sulfonation reaction to be subjected with various degrees of sulfonation. The sulfonated chitosan (SCS) has a pendant alkyl sulfate group dangling at the side chain, which can improve its hydrophilicity and water-solubility. Elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR) and 13C nuclear magnetic resonance (13C NMR) were adopted to identify the structure and determinine the distribution of the substituents of the final product. The degree of sulfonation in the SCS can be controlled and the hydrogen-bonding interaction can be reduced by varying the degree of sulfonation. A solubility test proved that solubility increased with degree of sulfonation at a wide range of pH values. X-ray diffraction patterns of sulfonated chitosan samples demonstrated that the crystallinity declined as the increasing degree of sulfonation. Thermogravimetric analysis (TGA) and modulated differential scanning calorimetry (MDSC) results indicated that thermal stability fell down but water absorbance increased with the degree of sulfonation. Better water soluble sulfonated chitosan is thus obtained. The controllable free pendant amino-groups of the chitosan polymer suggest new possibilities for the application of chitosan-based materials. Glutaraldehyde (GA) was used as a crosslinking agent for preparing crosslinking sulfonated chitosan membranes. The structures of crosslinking sulfonated chitosan membrane were elucidated using FT-IR and 13C NMR. The XRD results demonstrate that the degree of crystallinity of the GASCS membrane declines as the degree of crosslinking increase. An experiment on swelling and contact angle indicates that the degree of swelling and the contact angle of cross-linked chitosan membrane drop as the amount of glutaraldehyde increases; the hydrophilicity of GASCS decreases as the amount of glutaraldehyde increases. The pervaporation performance experiment indicates that the GASCS membrane separation is governed by diffusivity of the membrane. In Part II, chitosan was crosslinked using a sulfosuccinic acid (SSA) and glutaraldehyde mixture as the binary crosslinking agents to form hydrophilic chitosan network membranes. GA and SSA improve tensile strength and contribute to the hydrophilicity, respectively. The membranes that are produced by varying the crosslinking agent content are also characterized using FT-IR, X-ray diffraction and tensile testing, and by measuring their swelling ratio and thermal properties. Experimental results reveal that the contact angle of the membrane decreases from 84.54o to 69.83o and the maximum stress rises from 39.62 MPa to 133.66 MPa as the increase of the binary crosslinking agent content. These resultant membranes not only maintain the hydrophilicity but also enhance the mechanical strength. In Part III, chitosan was crosslinked using a synthesis Octa[3-propylglycidylether] dimethylsiloxy] petacycloctasilanae (OG) as the crosslinked agent to form a organic-inorganic hybrid chitosan network nanocomposite membranes(OGCS). The synthesis of OG was characterized using 1H-NMR and FT-IR. The OGCS was characterized by FT-IR. Contact angle measurement, swelling ratio, bulk density and fraction free volume all reveal that those properties increased at lower OG contents and then decreased with increasing OG contents. It was caused by the coagulation effect. The main factor of above results is the competition between crosslinking and coagulation. The degree of coagulation is enhanced with increasing OG contents in chitosan nanocomposite membranes. The OG coagulation behaves as the plasticizer and caused less improvement and the poorer properties. The tensile test, X-ray, TGA and MDSC analyses results show that the tensile properties and thermal properties slightly increased with increasing OG contents. This result originated from the OG regular cage-like structure and the X-ray pattern was demonstrated. Finally, the pervaporation separation performance for 90wt% ethanol aqueous dehydration of the above network membranes results show that a GA30SCS membrane at 60℃ has a permeation flux rate of 2532 g/m2-hr and the permeate contains 99.78% water.