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Title: Synthesis of polyacrylonitrile/MWCNT composites for potential bone replacement therapy
Author: Korobeinyk, Alina Vladimirovna
Awarding Body: University of Brighton
Current Institution: University of Brighton
Date of Award: 2011
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Polyacrylonitrile (PAN) is a linear polymer that is used in industry to produce carbon materials. While PAN-based carbon materials demonstrate excellent mechanical properties and promote bone cell growth along their surface, their porous properties are not sufficient for cell growth and proliferation. Carbon nanotubes (CNTs) are the one of strongest material available, which themselves posses some biological properties, and have the potential to extend clinical use of the carbon materials when manufactured in form of PAN-based composite and carbonized in order to form porous fibrous mat where nanotube-nanotube junctions are cemented with carbonized PAN. The work sought to develop and characterise PAN-CNT composites in main areas: 1) production of PAN-CNT composites, 2) carbonization of obtained composites, 3) investigation of reactivity of CNTs in order to improve interaction between polymer and nanotube in composite, and 4) assessment of the biological properties in vitro cell culture. PAN was synthesised via free-radical polymerization of acrylonitrile (AN) using azobisisobutyronitrile (AIBN) as initiator, and multi-walled CNTs were produced by chemical vapour deposition. Composites were produced by addition of acid-oxidized CNTs to AN solution as PAN was precipitating in form of loose powder or buckypaper. Characterization of the composite material with FTIR and I3C NMR found that the CNTs have no dramatic influence on AN polymerization. Composites made of buckypaper soaked in AN precursor solution were found to have better PAN distribution within composite. It was found that regardless of the synthesis approach, PAN-CNT composites were found to be non-porous and therefore unsuitable for cell growth, therefore silica-based CNT composites were synthesised as prospective candidates for the bone replacement material. It was found that silica forms a thin protecting layer around CNTs, when synthesised via sol-gel transformation of the 3-aminopropyltriethoxysilane, but was not thick enough to support a continuous CNT network. Furthermore this approach was used in synthesis of magnetic CNT -silica based composites for prospective application in magnetic driven adsorption and controlled drug delivery. To optimize the composite microstructure the CNT sidewall reactivity was investigated to determine its effect on porosity of the final composite. It was found that high temperature acid oxidation of pristine CNTs lead to an increase in the number of carboxylic groups' number and therefore contribute in the CNT's sidewall reactivity. In order to create porous carbonised materials, PAN and methylmethacrylate (MMA) was formed into a copolymer (PAN-co-MMA) in which mass content of MMA was 10% wt, was derived. Carbonisation of this copolymer in an inert atmosphere and in air leads to formation of the continuous open porous structure with a pore diameter in the range from 30 to 130μm, which is suitable for cell penetration. This was confirmed by in vitro cellular response to the PAN-co-MMA based carbon monolith was examined by culturing 3T3 mouse fibroblasts. It was also found that the copolymer under high heating rates lead to expansion and exfoliation. Examination of the resulting material shows that carbon nanomaterials produced are single- and multi- layered graphenes which may give a useful production route towards single layered graphene (SLG). This study has resulted in improved understanding of the processing of CNTs and the effect of a wide range of synthetic approaches on the final materials characteristics. The interesting preliminary results were obtained in the areas of CNTs reactivity, formation of magnetically driven adsorbents, and potential biological behaviour of porous carbonized PAN-co-MMA based monoliths
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available