Dissertation > Excellent graduate degree dissertation topics show

Mechanical and Water-holding Properties of Chitosan Fiber/Gellan Gum Composite Hydrogels

Author: LiuLiMei
Tutor: BaiTongChun
School: Suzhou University
Course: Physical and chemical
Keywords: gellan gum chitosan fibers hydrogel mechanical property dehydrationkinetics
CLC: O648.17
Type: Master's thesis
Year: 2013
Downloads: 42
Quote: 0
Read: Download Dissertation

Abstract

Gellan gum is a food additive approved by U.S.A Food and Drug Administration (FDA). It has attracted much attention due to its good biocompatibility, controllable mechanical properties, and it also can provide microenvironment similar to cartilage extracellular matrix for chondrocyte proliferation and differentiation. However, the mechanical property of gellan gum is so poor that it cannot meet the requirements for cartilage substitute materials. Chitosan fibers (CSFs) were used to be the reinforcing phase since its high strength. In this thesis, the relationship between the structure and physicochemical properties of chitosan fiber reinforced composite gellan gum hydrogel was studied, and this study would promote the development of artificial tissue materials.Firstly, the CSF and high-acyl gellan gum (HG) hydrogels with different CSFs content were prepared. And the rheological properties, fracture morphology swelling behavior, dehydration kinetics and dielectric properties were systematically studied. The result shows that the CSFs significantly improve the storage modulus (G’) of HG hydrogel. In addition, CSFs were interspersed in the three-dimensional network of CSF-HG hydrogels, which hinder the motion of HG chain segments, and reducing the swelling degree and the water content in equilibrium. The2.0CSF-HG hydrogel has lower endothermic enthalpy than that of HG hydrogel during the dehydration process. Moreover, the hydrophilic amino groups of CSFs would form stronger interaction between water and macromolecules in2.0CSF-HG hydrogel, and increase its dehydration activation energy. Besides these, the polar amino groups endow the oven-dried2.0CSF-HG hydrogel with significantly enhanced dielectric constant,878at1Hz.Secondly, we added CSFs into a mixed gellan gum of high-acyl (HG) and low-acyl gellan gum (LG), which was cross-linked by calcium ion (Ca2+). Then, the interaction between CSFs and HLG macromolecule, and its effect on mechanical strength, swelling behavior, thermal stability and dielectric properties of composite hydrogels were systematically studied. The results showed that a large number of hydrogen bonds between CSFs and HLG macromolecules were formed, which improve the thermal stability and mechanical strength of2.0CSF-HLG hydrogel. Similarly, hindered by CSFs, the HLG macromolecular chain segments cannot change by a large margin to absorb water, so the2.0CSF-HLG hydrogel showed low swelling degree and water content in equilibrium, and its endothermic enthalpy is also lower than that of HG hydrogel during the dehydration process. However, due to the supporting effect by CSFs, there were plenty of holes in2.0CSF-HLG hydrogel after it was dried in thermal oven. By this treatment, the3D structure of HLG hydrogel was collapsed.Finally, CSFs were added into LG to prepared CSF-LG hydrogels, the rheological properties and thermal dehydration kinetics of CSF-LG hydrogels were studied. By using the iso-conversional method of Kissinger-Akahira-Sunose (KAS), the relationship between the dehydration activation energy and the conversion rate was obtained. It is found that the activation energy decreases as the conversion rate increases, and increases with the content of CSFs.

Related Dissertations

CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Colloid chemistry ( physical and chemical dispersion system ) > Colloid > Gel and soft
© 2012 www.DissertationTopic.Net Mobile