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Synthesis and Characterization of Chiral Monomers and Polymers Syed Aziz Ashraf University of Wollongong, [email protected]

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Synthesis and Characterization of Chiral Monomers and Polymers Syed Aziz Ashraf University of Wollongong, Syed@Uow.Edu.Au University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 1997 Synthesis and characterization of chiral monomers and polymers Syed Aziz Ashraf University of Wollongong, [email protected] Recommended Citation Ashraf, Syed Aziz, Synthesis and characterization of chiral monomers and polymers, Doctor of Philosophy thesis, Department of Chemistry, University of Wollongong, 1997. http://ro.uow.edu.au/theses/1187 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] SYNTHESIS AND CHARACTERIZATION OF CHIRAL MONOMERS AND POLYMERS A thesis submitted in fulfilment of the requirements for the award of the degree DOCTOR OF PHILOSOPHY from UNIVERSITY OF WOLLONGONG by SYED AZIZ ASHRAF M.Sc DEPARTMENT OF CHEMISTRY June 1997 DECLARATION This is to certify that the work described in this thesis has not been submitted for a higher degree at any other University or institution. Syed Aziz Ashraf I ACKNOWLEDGMENTS I wish to express my sincere gratitude to my supervisors Professor Gordon G. Wallace, Professor Leon A.P. Kane-Maguire and Associate Professor Stephen G. Pyne for their enthusiastic supervision and encouragements throughout the completion of my thesis. I greatly appreciate the help and discussion of Professor Alan G. MacDiarmid of University of Pennsylvania, Philadelphia, USA, where I have carried out some of the experimental work of Chapter 3. The helps and friendships of staff and my fellow colleagues in Chemistry department are also greatly appreciated, especially Chee O. Too, Mir Reza Majidi, Zhao Hujin, Richard John, Ian Norris, Trevor Lewis and Norm Barisi, for their support and fruitful discussion. Finally, words cannot describe my love, esteem, affection and values that I constantly have for my wife Aisha and children for their great deal of endurance, selfless love and support throughout my PhD while I spent countless hours in the lab to achieve this goal. Thankyou to everyone. II ABSTRACT This thesis describes the synthesis and characterization of optically active monomers and their subsequent polymerization to optically active polymers (polyelectrolytes) and in one case a chiral hydrogel. The novel chiral monomers (IS, 2R, 4S)- and (IS, 2S, 4S)-a-[2-amino- 7,7-dimethylbicyclo[2,2,l]-l-heptyl] methylsulfonic acid 4a and 4b were synthesised as two diastereomers (Chapter 2) via the reductive amination of (75)-(+)-10-camphorsulfonic acid (HCSA). Reaction of these diastereomers with acroyl chloride yielded the corresponding optically active acrylamide monomers, 5a and 5b. These novel monomers incorporate a chiral auxiliary that also has an ionisable sulfonic acid group. Ultimately, the acrylamides were converted to novel, polyacrylamides la and lb, via free radical polymerization. These polyacrylamides possessed the useful features of both optical activity and polyelectrolyte behaviour. Hydrolysis of the polymer lb to give polyacrylic acid confirmed (via iH NMR spectroscopy) that the polymer was ca. 72% isotactic.The monomer 4a was also used to form cross- linked or interpenetrated networks that have chiral hydrogel properties and exceptional water intake (EWC=99.96%) properties. The electrochemical syntheses of new polyaniline and polypyrrole salts were subsequently carried out in which the above mentioned monomers and polyelectrolyte were incorporated as a counterion (Chapter 2). Polypyrrole salts were successfully grown by both potentiostatic and galvanostatic methods and characterised by cyclic voltammetry. However, attempts to synthesise polyaniline salts incorporating the above monomers or polyelectrolyte were unsuccessful. This was probably due to the unsuitable pH conditions, since in order to grow polyaniline salts electrochemically, the pH of the reaction solution should normally be in the range 0-2. Chemical doping of neutral emeraldine base (EB) with the novel monomers and polymers to generate chiral polyaniline salts was also examined (Chapter 3). A green film of optically active polyaniline salt was obtained by doping with the chiral acrylamide monomer 5b, as confirmed by uv-visible and CD spectroscopy. It was proposed that the polyaniline chain in this chiral polymer adopts a helical conformation maintained in one hand via H-bonding to the acrylamide (CO) group and ionic bonding to the SO3" group. In contrast, the monomer 4b did not dope EB, presumably because of the presence of a zwitterion structure for 4b, therefore restricting salt formation. Salt formation also did not occur upon the addition of polymer lb to EB. A detailed study was also carried out of the influence of various conditions on the chiroptical properties and conformations of the polyaniline salt generated by doping EB with (+)-HCSA under a variety of conditions (Chapter 3). The optical activity and conformational changes after doping were monitored in various solvents such as CHCI3, DMF, NMP, DMSO and THF by uv-visible and CD spectroscopy. Other conditions examined included the presence or absence of an inert argon atmosphere, the mode of mixing of EB and dopant (+)-HCSA, the concentration of EB (+)-HCSA, and the molecular weight of the EB. In each case, samples were examined over an extended period of time. CD and uv-visible spectra indicated that the PAn. (+)-HCSA salts generated in CHCI3 and NMP solvents in air had different initial conformations for their polyaniline chains, believed to be "compact coil", and "expanded coil" respectively. Interestingly, the CD spectrum observed in CHCI3 changed over 48 hr to that observed in NMP, indicating a change in polymer conformation. In contrast, analogous doping reactions in the presence of argon gave circular dichroism bands (at ca. 340, 405, and 460 nm) that were insensitive to the nature of the solvent. It is also significant that no optical activity was observed when small oligomers of EB (tetramer and sixteen-omer) were doped with (+)-HCSA in CHCI3 solvent, indicating the importance of the molecular weight of the EB substrate. Spin-cast films of EB doped with (+)-HCSA in m-cresol, CHCI3 and 1,1,1,3,3,3-hexafluoropropanol solvents were also studied by CD and uv- visible spectroscopy (Chapter 3). The CD spectrum of a spin-coated film of PAn. (+)-HCSA cast from CHCI3 onto quartz showed a localised polaron band at 767 nm. In contrast, a film of PAn. (+)-HCSA cast onto glass or quartz from m-cresol solvent showed that the localized polaron band had almost disappeared and was replaced by a free carrier tail in the near-infrared region. This suggests a change in conformation for the polymer chain from a "tight coil" to an "extended coil" on changing solvent from CHCI3 to m- cresol. Similar behaviour was found for a PAn. (+)-HCSA film spun cast from 1,1,1,3,3,3-hexaflouropropanol, suggesting a similar change in conformation for the polyaniline backbone. An alternative approach to chiral polyelectrolytes was explored in Chapter 4, namely the synthesis of vinyl monomers containing a 2- phenyl- or 2-te7t-butyloxazolidin-5-one unit and their polymerization to the related polyvinyl species. Although polymerization was readily achieved via radical reaction (AIBN) in a quantitative yield, characterization was limited to solid state 13C NMR and ir and uv-visible spectra, due to the insolubility of the polymers in a wide range of solvents. This insolubility also rendered the polymers inert to hydrolysis, even under severe conditions. Finally the synthesis and characterization of a related vinyl monomer in which the vinyl unit bears a thiophene substituent was also achieved. V ABRREVIATIONS A electrode surface area A" doping anion Ag/AgCl silver/silver chloride reference electrode c- counterion °c degree Celsius CA chronoamperogram CD circular dichroism cm centimetre CP chronopotentiogram CV cyclic voltammetry or voltammogram DMF N, N-dimethylformamide DMSO dimethylsulfoxide E potential EC electrochemical EP peak potential EMS electron microscopy F Faraday constant C-mol"l g gram HCSA camphorsulfonic acid lH proton hr hour Hz hertz I current IR infrared M molar m milli millilitre cation milliampere minute molecular weight (g) milivolt number of electron 1 -methyl-2-pyrrolidinone nuclear magnetic resonance oxidation process polyaniline polypyrrole polyelectrolyte reduction process resistance conductivity second Siemens per centimetre conductivity (S-cm"l) time (s) working electrode PUBLICATIONS a- Journal papers 1 "Optically Active Sulfonated Acrylamide Monomer Derivatives", S.A. Ashraf, S.G. Pyne, L.A.P. Kane-Maguire and G.G. Wallace, Aus. Provisional Patent no. P-3414 YS/JP (1995). 2. "Influence of the Chiral Dopant Anion on the Generation of Induced Optical Activity in Polyanilines", S.A. Ashraf, L.A.P. Kane-Maguire, M.R. Majidi, S.G. Pyne and G.G. Wallace, Polymer, Vol. 38 No. 1, pp. 2627-2631. (1997). 3. "Factors Controlling the Induction of Optical Activity in Chiral Polyanilines", S.A. Ashraf, L.A.P. Kane-Maguire, l.D. Norris and G.G. Wallace, Synthetic Metals, 84 (1997) 115-116. 4. "Synthesis and Polymerisation of Novel Chiral Acrylamido-sulfonic acid Monomers; Preparation of New Chiral Polyelectrolytes and Gels". Macromolecules. (submitted). b- Conference Publications 1. "New Chiral Polyelectrolytes and Gels derived from Camphorsulfonic Acid", S.A. Ashraf, L.A.P. Kane-Maguire, S.G. Pyne and G.G. Wallace, Abstracts, 21st Australian Polymer Symposium, Wollongong, February 1996, PS 2-6. 2. 'New Chiral Polyelectrolytes and Gels", S.A. Ashraf, L.A.P. Kane -Maguire, S.G. Pyne and G.G. Wallace, Proceedings of American Chemal Society. PMSE, New Orleans, March 1996; 74, 151-153. VIII 3. "Novel Optically Active Polyanilines", M.R. Majidi, S.A. Ashraf, L.A.P. Kane-Maguire and G.G. Wallace, Abstracts, Advances in Polymers III - Designer Polymers, RACI Symposium, Melbourne, September 1996, pp. 12-17 (ISBN 09095 89 855). TABLE OF CONTENTS ACKNOWLEDGEMENTS I ABSTRACT II ABBREVIATIONS IV PUBLICATIONS VI CHAPTER 1 INTRODUCTION 1 1.1 CHIRALITY 1 1.1.1. Biological Significance of Chirality 3 1.1.2. Diastereomers 5 1.1.3. The Selective synthesis of Diastereomers 8 1.2 TYPES OF CHIRALITY 9 1.2.1.
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