PS-b-PMMA Block Copolymer Derived Electrospun Nanofibers: Synthesis, Characterization and Surface Properties Evaluation

Adaval, A (2014) PS-b-PMMA Block Copolymer Derived Electrospun Nanofibers: Synthesis, Characterization and Surface Properties Evaluation. Masters thesis, Indian Institute of Technology, Hyderabad.

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Abstract

Block copolymers represent a broad subject of current research due to their exotic property of controlled micro phase separation which paves way to fabricate periodic nanostructures that can be utilized in various engineering applications. Electrospinning of block copolymers to produce nanofibers is an emerging area which is simple and efficient for nanofiber production. The nanofibers with their high surface area and increased mechanical properties can be combined with the unique properties of block copolymers for use in numerous applications like filtration, biosensors, drug delivery, tissue engineering and protective clothing. In this work poly(styrene-block-methylmethacrylate) (PS-b-PMMA) was electrospun in an organic solvent and optimized a number of electrospinning parameters that affect the morphology of the obtained non-woven fabric such as concentration, applied electric field, distance between the source and collector and flow rate in order to yield long, continuous and uniform nanofibers. Thereafter, as-spun fibers were annealed by two methods such as thermal and using solvent assisted vapors. UV exposure to the annealed fibers were done to allow the phase separation of polymer blocks and complete the cross-linking of one phase. The non crosslinked phase was subsequently etched out selectively using a weak acid in order to generate the porosity in the PS-b-PMMA electrospun fiber mats. FESEM, FTIR spectroscopy and TGA were used for structural characterization of electrospun PS-b-PMMA fibers and the effect on the morphology of obtained fibers was observed by changing the different electrospinning parameters. We further studied the wettability characteristics using contact angle goniometer which showed that changing morphology affects the wettability. A comparative study on the reflectivity properties of as spun, beaded fibers and etched fibers revealed that the anti-reflectivity characteristics shown by as-spun fibers were the highest. Further, adsorption studies of a dye methylene blue were carried out with ACF fabric and fibers deposited on ACF fabric. Effect of changing the concentration of adsorbate, changing time and temperature was studied. The fibers showed higher adsorption capability compared to ACF fabric showing improved adsorption efficiency.

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