The intermolecular interactions of branching onto collagen chains and its effects on the formation of nanocomposite fibres
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Collagen is an important biomimetic material. Several attempts to electrospin this biopolymer have proved difficult due to significant denaturation and degradation occurring while being dissolved in a solvent and spun. Acid soluble collagen (ASC) was successfully pre-treated by grafting Methyl Methacrylate-coEthyl Acrylate onto its chains leading to ASC-g-poly(methyl methacrylate-co-ethyl acrylate) (CME). This was not only to add stability to its structure but also allowed electrospinning of the material which would otherwise have a deteriorating effect on its degradation rate and would have required post treatment. Experimental relations depending on monomer feed ratios and physiochemical properties of side chains that affect fibre formation, diameter, and distribution were investigated. Increasing the number of branching onto ASC chains can significantly reduce the deteriorative impact of electrospinning conditions along with improving its stability in high humidity conditions. The short chain branching onto ASC chains can effectively influence the fibre thermal stability while long chain branching provides a higher density of chain entanglements that improves fibre uniformity. The study has shown how to process a composite fibre which can consist of CME with a structurally and electrically incompatible polymer, by using coaxial electrospinning. Nylon 66 has been taken as an example of this methodology. By tailoring the intensity of the electric field, different fibre content was achieved from the core and shell components, leading to varied physical properties; thermal, mechanical and degradability. The effect of chain orientation and intermolecular interactions between two structurally different polymer chains were investigated; custom-built electrostatics and supplementary bonding e.g. hydrogen bonds were identified the major factors for the design of reinforced CME/nylon 66 core-shell fibres. Finally, a functionalisation methodology has been successfully established in which SMART nanofillers, such as graphene oxide (GO) is attached to CME. By increasing the GO content, significantly increases were achieved in the performance of polymerisation onto ASC. This nanofiller can improve the physiochemical properties of ASC chains, the same as the grafted side chains. It was found that humidity and temperature play key roles in the degradation rate of GO-CME composite; above 50 oC, GO is not as stable as branches on the surface of collagen chains. The impact of this research is in the ability of collagen to be used in a variety of applications by making it more stable via grafting from new end groups. In consequence, new methodologies in electrospinning of nanofibres; composite fibres and smart nanofillers become possible, imparting new properties and new possibilities of this biopolymer for numerous end uses.