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Development and Characterization of Segmented Polyurethanes Based on L-Amino Acid Based Chain Extenders

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Development and Characterization of Segmented Polyurethanes Based on L-Amino Acid Based Chain Extenders Development and characterization of segmented polyurethanes based on L-amino acid based chain extenders A Thesis submitted for the degree of Doctor of Philosophy By Swati Sharma (M.Sc. Biochemistry) Faculty of Life and Social Sciences Swinburne University of Technology Melbourne Australia February 2016 Abstract The acid catalysed Fischer and alkali metal salt based esterification reactions were used to synthesise a series of diamine ester and dihydroxy ester compounds respectively from various naturally occurring L-amino acids. L-leucine, L-isoleucine, L-phenylalanine, L- tyrosine amino acid were used to synthesise diamine diester compounds whilst amine group protected L-Z-serine, L-Z-threonine and L-Z-tyrosine amino acids were used to synthesise novel dihydroxy diester compounds. For the dihydroxy ester compounds, in particular, optimisation of the reaction temperature was done. The yield for both diamine and dihydroxy ester synthesis were ~ 80 % and 85% respectively. Few of the synthesised ester compounds were yellow colour oil and few of them were white solid in appearance. The synthesised compounds were fully characterised by nuclear magnetic resonance, infrared resonance spectroscopy and mass spectroscopy. The success of the reaction and the purity of the synthesised compounds were confirmed by these techniques. The intended purpose of the synthesis of these novel amino acid based ester compounds is to use them as dihydroxy and diamine chain extender for polyurethane and polyurethane urea synthesis. A series of polyurethane and polyurethane urea based on amino acid based chain extender (mentioned above) was synthesised. Polycaprolactone (Mw1000) act as polyol and 4,4- methylenediphenyl diisocyanate act as diisocyanate component for polyurethane synthesis. The control polyurethane synthesised was based on 1,4-butanediol as chain extender with polycaprolactone as polyol and 4,4-methylenediphenyl diisocyanate as diisocyanate component. Synthesised polymers were fully characterised for structural, thermal, surface and mechanical properties. Obtained properties of the amino acid based polyurethane/polyurethane urea were compared with the control polyurethane to evaluate the effect of chain extender type and its structure onto the physiochemical properties of the synthesised polymer. Synthesised amino acid based polyurethane/polyurethane urea showed moderately high molecular weight with narrow polydispersity. The percent yield of the polyurethane/polyurethane urea synthesis was ~ 70%. The amino acid based polymers ranged from completely amorphous to semicrystalline polymer. The hard segment was amorphous in all cases of the amino acid based polyurethane/polyurethane urea. Phase mixed morphology was shown by amino acid based i polyurethane/polyurethane urea as compared to phase segregated morphology observed for control polyurethane. Mechanical properties were tested by obtaining stress strain curve. The amino acid based polymers were weak elastomeric material with low tensile strength and high extensibility as compared to control polyurethane. Non-linear structure of chain extenders and weak hydrogen bonding might be one of the main reasons for low mechanical properties. The amino acid based polyurethane/polyurethane urea were stable up to high temperature. The polymer surface hydrophobicity was increased with the incorporation of amino acid based chain extender. The benzyloxycarbonyl protecting group of serine amino acid based polyurethane was removed by the use of Hydrogen bromide/Acetic acid solution method. Reaction time was optimised for the deprotection reaction. Nuclear magnetic resonance spectroscopic analysis indicated that deprotection resulted in 62 mol % reduction in benzyloxycarbonyl group content with minimal affecting polyurethane backbone. Structure property relationship of the polymer was studied by using high molecular weight (Mw 2,000) of polycaprolactone as soft segment. A series of polyurethane and polyurethane urea were synthesised and characterised with polycaprolactone (Mw 2,000 Dalton) as soft segment and obtained properties were compared to polyurethane/polyurethane urea series made with polycaprolactone (Mw 1,000 Dalton). It was observed that as soft segment molecular weight increases, phase segregation, percent crystallinity increases and glass transition of soft segment decreases. Increase in phase segregation morphology has also helped to obtain improved mechanical properties of the amino acid based polyurethane/polyurethane urea. Surface hydrophobicity increases as soft segment molecular weight increases. However, thermal stability was decreased due to phase segregated morphology. At the end, the in vitro cytotoxicity response of the amino acid based polyurethane/polyurethane urea was evaluated by LIVE/DEAD assay kit. Mouse fibroblast cells were seeded on to the polyurethane/polyurethane urea films. The polyurethane/polyurethane urea did not show any cytotoxic response and healthy cell growth, attachment and proliferation was observed on polymer films which indicates that these polyurethane/polyurethane urea may be useful for biomedical applications. ii Acknowledgements On this great occasion of my thesis submission, first of all I am grateful to the almighty God without whose blessings I would not have been able to complete this challenging journey. I would like to convey my sincere thanks to my supervisor Professor Ian Harding for his valuable guidance, advice and availability whenever required during this PhD. I would also like to thank Senior Research Scientist Roshan Mayadunne for providing me help and guidance during my research work performed at CSIRO. I would like to express my gratitude to Dr. Keith McLean, Dr. Thilak Gunatillake and Dr. Tim Hughes from CSIRO for providing me encouragement, guidance and friendly advice whenever I needed during my experimental work. I would like to pass on a big Thank You to Dr. Akhil Gupta whose immense knowledge and support helped me to think out of the box and do things in a different way to achieve the desired outcome. I really appreciate the help of Dr. Roger Mulder from CSIRO for NMR analysis, Dr. James Mardel from CSIRO for FTIR analysis and Veronica Glattauer from CSIRO for polymer cell studies. Last but not the least I would like to thank my husband Rahul Bhardwaj for showing great faith in me. Thanks for being such a wonderful husband and always there to make me feel stronger mentally and providing all love and support to me in fulfilling my motherhood duties during thesis writing. iii Declaration This thesis contains no material which has been accepted for the award of any other degree or diploma, in any University, college or any other educational institute. To the best of my knowledge, this thesis contains no material previously published or written by another person except where due reference is made in the text of the thesis. Signature of Candidate: ..................................................................... Date: ........................................................................ iv List of Conference Presentations Following is a list of conference presentations from the work contained in this thesis. Conference Presentations Sharma S., Harding I., Mayadunne R. M., (January, 2009). Amino acid based diamine diester as chain extender in polyurethane synthesis. 19th Annual conference of the Australasian society for biomaterials and tissue engineering (ASBTE) Sydney, Australia. Sharma S., Harding I., Mayadunne R. M., (February, 2010). Novel complex amino acid based diols as chain extenders in polyurethane synthesis. 20th Annual society for biomaterials and tissue engineering (ASBTE) Queensland, Brisbane, Australia. Sharma S., Harding I., Mayadunne R. M., (October, 2010). Novel complex amino acid based diols as chain extenders in polyurethane synthesis. Symposium on biomaterials, Rutgers University, New Jersey, USA. Sharma S., Harding I., Mayadunne R. M., (May, 2011). Synthesis and characterization of amino acid based polyurethane. CSIRO advanced material conference (CAM), 2011, Melbourne, Australia. v Table of Contents Abstract .......................................................................................................................................... i Acknowledgements ...................................................................................................................... iii Declaration ................................................................................................................................... iv List of Conference Presentations .................................................................................................. v Table of Contents ......................................................................................................................... vi Index of Figures .......................................................................................................................... xii Index of Schemes ........................................................................................................................ xv Index of Tables .......................................................................................................................... xvi Abbreviations ........................................................................................................................... xviii Chapter 1: Introduction ................................................................................................................ 1
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