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Preparation And Characterization Of Cyclodextrin-Based Inclusion Complex Hydrogel And Hydrophobic Association Hydrogel

Posted on:2011-04-23Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q R ChenFull Text:PDF
GTID:1101360305953415Subject:Polymer Chemistry and Physics
Abstract/Summary:PDF Full Text Request
Hydrogel is a disquisitive hotspot in materials science at present. It was divided into physically crosslinked hydrogel and chemically crosslinked hydrogel according to different crosslinking ways. Physically crosslinked hydrogel is three-dimensional crosslinked network formed by noncovalent bond interaction, it includes van der Waals force,π-πinteraction, ionic interaction, hydrogen bonding action, hydrophobic action and entanglement action, and so on. These noncovalent bond interactions led physically crosslinked hydrogel marked difference from chemically crosslinked hydrogel in many properties, such as intelligent sol-gel transformation, special mechanical behavior and swelling behavior. Consequently, physically crosslinked hydrogel showed significance application prospect in bio-medicine and tissue engineering. Presently, just four kinds of hydrogels, topological hydrogels, double network hydrogels, nanocomposite hydrogels and macromolecular microsphere composite hydrogels, possess excellent mechanical property. In order to meet the needs of gels in mechanical property and tissue engineering, new hydrogels with high mechanical strength were hankered.In this thesis, preparation of physically crosslinked hydrogel is the major objectives. Physically crosslinked inclusion complex hydrogel (IC gels) and hydrophobically associating hydrogel (HA gels) were prepared. Study on IC gels were supported in theory and practice by investigating the interaction betweenβ-cyclodextrin (β-CD) and nonionic surfactant Octyl phenol polyethoxy ether (OP-n), such as crystallization behavior and temperature responsibility. IC gels were prepared by inclusion complex interaction betweenβ-CD polymer and surmonomer OP-10-AC. In addition, HA gels with high mechanical strength were prepared by micellar copolymerization, and the structure and formation of HA gels were discussed by swelling behavior and tensile mechanical properties.For the mixed dispersity system consisting ofβ-CD and OP-n, the inclusion complex of 2∶1 stoichiometry betweenβ-CD and OP-n was determined via the optical transparency method as well as the color method. The transparency of mixed dispersity system first increased and then decreased with increasingβ-CD contents, and crystallization was formed by hydrogen bonds action. The phase distribution behaviors ofβ-CD and OP-n were determined by UV-Visible spectrum and Gravimetric analysis, respectively. The roles ofβ-CD and OP-n (n = number of oxyethylene units) in phase distribution process were investigated. The results indicated thatβ-CD could promote the phase separation and whereas OP-n surfactants'hydrophilic part hinder the phase separation. The crystal morphologies of mixed systems were powders and branches, which were characterized by polarized light microscope. The crystalline structure was further characterized by X-ray Diffraction (XRD), and the results revealed that these inclusion complexes presented a channel-type structure by intermolecular hydrogen bonding.Furthermore, the temperature response of the mixed dispersity systems ofβ-CD and OP-n in water was investigated by UV-visible spectrum. Changes of four kinds of interaction, hydrogen bond interaction between pseudorotaxanes, association interaction of surfactants, inclusion-exclusion action and hydrogen bond interaction between oxyethylene group and H2O, were investigated through discussion in turbidity with varied temperature. The results revealed that hydrophilic polyoxyethylene part transformed into hydrophobic conformation at high temperature by the induction ofβ-CD, and the three hydrophobic parts, octyl, phenyl and oxyethylene groups, could be included into the cavity ofβ-CD, the mixed systems were in dynamic equilibrium state of inclusion-exclusion.β-CD polymeric particle was prepared by reactivity of hydroxyl group, and the particle size was determined by AFM and TEM. Surfactant OP-10 was modified into polymerizable monomer OP-10-AC. IC gels consisting of OP-10-AC,β-CD NP and AM were prepared with inclusion complexes ofβ-CD NP and OP-10-AC as multifunctional crosslinker. The effects ofβ-CD NP on structure and properties of IC gels were investigated by rheology and mechanical proerties tests. The results showed that the association structure converted into inclusion structure with increasingβ-CD NP contents, and viscosity first increased and then decreased in IC gels systems. The tensile strength basically unchanged and elongation at break increased with increasingβ-CD NP contents.Hydrophobic associating hydrogels (HA gels) with high mechanical strength were synthesized through micellar copolymerization of acrylic acid (AA) and a small amount of octadecyl methacrylate (OMA) in an aqueous solution containing sodium dodecyl sulfate (SDS). The three-dimensional network of HA gels can be constructed with the solubilization micelles that act as effective cross-linker. Therefore, the effects of SDS contents on various physical properties, such as optical transparency, mechanical property and swelling behavior were investigated. The mechanical properties and swelling ratios exhibited approximately the same inflection point with increasing SDS content, it was obviously differ from other hydrogels such as conventional chemically cross-linked hydrogels and nanocomposite hydrogels. The structural and elastic parameters were evaluated by the theory of rubber elasticity, Mooney-Rivlin theory and the theory of micellar copolymerization. The results showed that the number of solubilization micelles increase, but, the number of effective cross-linking points first increase and then decrease with increasing SDS contents. This is the reason why some properties of HA gels exhibit inflection points with the increasing of SDS contents. The formation process of HA gels could be divided into two processes: one was the micellar copolymerization process of mixed dispersed system, and the other was the associating process between different hydrophobic microblocks solubilized by surfactant SDS.The physically crosslinked hydrogel possess particular swelling behavior. The side was obviously differ from section in swelling ratio and rate, it due to the different structure. Therefore, the shape of IC gels changed from cylinder type to dumbbell type, and cylinder type again. The swelling behavior of HA gels in aqueous solutions at different pH values, salt concentration and temperature were investigated. The results showed that the swelling process could be divided into three stages: namely, the gels erosion stage, swelling equilibrium stage and gels disruption stage. Salt would restrained the swelling of HA gels, and inorganic salt is more stronger than organic salt. For HA gels, the increasing temperature can promote gels erosion.In summary, IC gels were prepared via host-guest interaction based on the study ofβ-CD and OP-n mixed dispersity system, and received significant results. The formation mechanism and swelling process of HA gels were investigated. These results gave a basis for study on physically crosslinked hydrogel.
Keywords/Search Tags:Cyclodextrin, Octyl phenol polyethoxy ether, Crystallization behavior, Temperature responsivity, Inclusion complex hydrogel, Hydrophobic association hydrogels, mechanical property, swelling behavior
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