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URN etd-0209110-120152 Statistics This thesis had been viewed 3149 times. Download 1245 times. Author Wei-Jen Huang Author's Email Address No Public. Department Chemical Engineering Year 2009 Semester 1 Degree Master Type of Document Master's Thesis Language English Page Count 105 Title STUDY ON PREPARATION AND PROPERTIES OF THERMOSENSITIVE ORGANIC-INORGANIC HYBRID GELS Keyword interpenetrating networks silane coupling agent siloxane organic-inorganic hybrid thermosensitive hydrogel hydrogel thermosensitive organic-inorganic hybrid siloxane silane coupling agent interpenetrating networks Abstract Poly(N-isopropylacrylamide), PNIPAAm, hydrogels are well known to show thermally reversible swelling-deswelling behavior around 32℃ in aqueous solutions with respect to a critical gel transition temperature (CGTT). Introducing inorganic moiety to prepare organic-inorganic hybrid gels can affect some properties of hydrogels. In this research, organic-inorganic hybrid gels were prepared by introducing silane monomers to copolymerize or crosslink with PNIPAAm by emulsion polymerization and sol-gel reaction, and the effects of silane coupling agent, IPN structure, TEOS content, silica content, and modification of silica on swelling ratios, swelling kinetics, and mechanical properties of hybrid gels were investigated. The results showed that the swelling and mechanical properties would be mainly affected by various situation of gel structure caused by introduction of inorganic moiety and the silane coupling agent.
A series of organic-inorganic hybrid thermosensitive gels with three different structures were prepared from N-isopropylacrylamide (NIPAAm), and N, N’-methylenebisacrylamide (NMBA) and tetraethoxysilane (TEOS) [N-IPN]; NIPAAm, 3-(trimethoxysilyl) propyl methacrylate (TMSPMA) as coupling agent and TEOS [NT-IPN]; and NIPAAm, TMSPMA and TEOS [NT-semi-IPN] by emulsion polymerization and sol-gel reaction. The effect of different gel structures and coupling agent on the swelling behavior, mechanical properties, and morphologies of the present gels was investigated. Results showed that the properties of the gels would be affected by the gel networks such as IPN or semi-IPN and with or without existence of TMSPMA as the bridge chain between networks. The NT-semi-IPN gel had higher swelling ratio and faster diffusion rate because poly (NIPAAm) moiety in the semi-IPN gels was not restricted by NMBA network. However, the IPN gels such as N-IPN and NT-IPN had good mechanical properties and lower swelling ratio, but had a poor thermosensitivity due to the addition of coupling agent, TMSPMA, into the gel system that resulted in denser link between organic and inorganic components. The morphology showed that IPN gels had partial aggregation (siloxane domain) and showed some denser phases.
Further discussion of above-mentioned series, the effect of TEOS content on the swelling behavior, mechanical properties, and morphologies of the present gels was investigated. Results showed that the properties of the gels would be affected by the gel networks such as IPN or semi-IPN, existence of TMSPMA as the bridge chain between networks, and content of TEOS. The results of effect on gel structure were similar as mentioned before. The swelling ratios and thermosensitivity of the hybrid gels decreased with an increase of TEOS content. As the content of TEOS increased, the phase separation occurred that resulted in loosen gel structure and consequently showed a weaker modulus and lower crosslinking density.
Moreover, nanosilica and modified nanosilica were introduced into this system to replace the TEOS and the effect of inorganic nano-silica on swelling behaviors and mechanical properties were investigated by adding different amount of nano-silica and modified nano-silica. Results showed that the swelling ratios of the hybrid gels decrease with increasing nano-silica content. Existence of silane coupling agent would also reduce the swelling ratios of the hybrid gels. Adding coupling agent or nano-silica would improve the gel strength. Modification of nano-silica by grafting amino-silane via sol-gel process was carried out and the effect of addition of modified silica on gel properties was also investigated. Results showed that the hybrid gels containing modified silica would have higher swelling ratios and moduli than those containing unmodified silica. Gels containing both silane coupling agent and silica would have higher crosslinking density because the silica would be better crosslinked with coupling agent.
Advisor Committee Wen-Fu Lee - advisor
Chi-Yuan Huang - co-chair
Chin-Tsou Kuo - co-chair
Sheng-Huei Hsiao - co-chair
Shiaw-Guang Hu - co-chair
Trong-Ming Don - co-chair
Files Date of Defense 2010-01-28 Date of Submission 2010-02-09