Ring-Opening Polymerization of [Beta]-Substituted-[Beta]- Propiolactones :: Synthesis of Biodegradable Polymers and Stereochemistry Study
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University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 1896 - February 2014 1-1-1990 Ring-opening polymerization of [beta]-substituted-[beta]- propiolactones :: synthesis of biodegradable polymers and stereochemistry study/ Yan, Zhang University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_1 Recommended Citation Zhang, Yan,, "Ring-opening polymerization of [beta]-substituted-[beta]-propiolactones :: synthesis of biodegradable polymers and stereochemistry study/" (1990). Doctoral Dissertations 1896 - February 2014. 771. https://scholarworks.umass.edu/dissertations_1/771 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 1896 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. RING-OPENING POLYMERIZATION OF 6-SUBSTITUTED-G-PROPIOLACTONES: SYNTHESIS OF BIODEGRADABLE POLYMERS AND STEREOCHEMISTRY STUDY A Dissertation Presented By YAN ZHANG Submitted to the Graduate School of the University of Massachusetts in partial fulfillment of the requirments for the degree of DOCTOR OF PHILOSOPHY September 1990 Polymer Science and Engineering ' RING-OPENING POLYMERIZATION OF B-SUBSTITUTED-3-PROPIOLACTONES: SYNTHESIS OF BIODEGRADABLE POLYMERS AND STEREOCHEMISTRY STUDY A Dissertation Presented By YAN ZHANG Approved as to style and content by: Robert W. Lenz, Chairma Thomas J. McCarthy, Member William E. McEwen, Member 2£ W.J. MacKnlght,night, Department Head Polymer Science and Engineering Dedicated to my husband, Li Dong and my daughter Angela. AKNOWLEDGEMENTS I want to express great gratitude to my advisor Prof. Robert W. Lenz for his precious guidance and tremendous support during my study at the University of Massachusetts. I also want to thank Prof. Thomas J. McCarthy and Prof. William E. McEwen for their time and effort spent in serving on my thesis committee. I have had the wonderful opportunity to study here and have met many talented and friendly people. In particular, I want to acknowledge Dr. Richard A. Gross and Dr. Gerd Konrad for their contributions and many helpful discussions in this research. I am grateful for the cooperation and friendship of my lab partner Mr. Herbert W. Ulmer whom I wish all the best in his Ph.D. study. I am indebted to many fellow students and the faculty of the Polymer Science and Engineering Department, especially Ms. Carol Moro and Christine Salame for their logistical assistance. I would also like to thank my office-mate Dr. David F. Gilmore for his help in editing of my thesis. Last but not the least, I want to show my deep appreciation to my parents for their moral and indispensable support coming far away from my homeland, China; my mother-in-law who has shouldered the burden of taking care of my daughter, Angela to spare my limited time; my husband, Li Dong for his devotion, continuous encouragement and much needed patience. I thank the CUMIRP, Center for UMass-lndustry Research on Polymer, for the funding during my study. i v ABSTRACT RING-OPENING POLYMERIZATION OF G-SUBSTITUTED-G-PROPIOLACTONES: SYNTHESIS OF BIODEGRADABLE POLYMERS AND STEREOCHEMISTRY STUDY SEPTEMBER, 1990 YAN ZHANG, B.S., BEIJING UNIVERSITY M.S, BEIJING UNIVERSITY Ph.D., UNIVERSITY OF MASSACHUSETTS Directed by: Professor Robert W. Lenz Biodegradable polymers, for biodegradable plastic utility and drug release biomedical applications, are the primary objectives of this theses research. We have synthesized poly(B-hydroxybutyrate) (PHB), poly(3-malic acid) (PMA) and their copolymers by the ring- opening polymerization reactions of 3-butyrolactone and 3-benzyl malolactonate. A varity of catalysts were used, including the stereoregulating catalysts, ethyl aluminoxane (EAO) and the of in-situ preparation of AI/H well product the Et3 2 0, as as the non- stereoselective catalysts, Et 2 Zn/H 2 0 and (5,10,15,20- tetraphenylporphinato)aluminum chloride (TPPAICI). The degree of stereoregulation of the homopolymers was enhanced by the use of a stereoregulating catalyst, followed by product extraction. The resulting insoluble fractions of PHB and PBML are stereoregular crystalline polymers having high molecular v weights, with the former compared with naturally occurring P([R]- HB) in corresponding properties. The stereoregularity of the synthetic polymers 13 was determined by C (75.4 MHz) NMR spectroscopy, differential scanning calorimetry (DSC) and FTIR spectroscopy. The yield of polymerization was optimized by using the Et Zn/H 2 2 0 and TPPAICI catalysts, resulting the amorphous polymers with relatively low molecular weights. The analysis of copolymer 13 tacticity and comonomer sequences by using C-NMR and DSC indicats a random distribution of the copolymer sequences. The stereochemical couse of the ring-opening polymerization of BL with the Et AI/H and Et 3 2 0 2 Zn/H 2 0 catalysts was studied using [S]-BL as a stereochemical probe. The [S]-3-BL, which was prepared in five steps from naturally occurring P([R]-HB), had an optical purity in excess of 97% as measured by 1 H NMR spectroscopy in the presence of a chiral europium shift reagent, Eu(hfc) . 3 The stereochemical configuration and isomeric purity of the repeating units in the polymers obtained were determined both from their specific optical rotation and by degradation of the polymers to their component methyl 8-hydroxybutyrate units. From our investigations it was concluded that the ring-opening reaction can be carried out by different routes in the Al- and/or Zn-water catalysts, and the two enantiomers, P([R]-HB) and P([S]-HB) were obtained as the result of the configuration retention or inversion. These enantiomers of PHB are very useful for the study of the stereochemistry of synthetic poly(G-lactone)s and their biodegradability. vi TABLE OF CONTENTS Page ACKNOWLEDGEMENTS.. IV ABSTRACT v LIST OF TABLES ..A LIST OF FIGURES ..xi Chapter 1 . INTRODUCTION ...1 1 .1 Biodegradable Polymers ..1 1.2 Polyesters Studied. ..2 1.3 Ring-Openina Polymerization of B-Sustituted-8-Propiolactones ...5 1.3.1 Ionic Polymerization ...5 1 .3.2 Coordination Polymerization ...8 1 .4 P(HB-co-HV) Copolymers 11 1 .5 Functional Copolymers, P(HB-co-BML).... .11 1.6 Biomedical Applications 12 1 .7 Stereochemistry of the Ring-Opening Polymerization of the B-Lactone 14 References on 2. RESULTS AND DISCUSSION 2.1 Synthesis and Characterization of Racemic Polyesters 24 2.1.1 Synthesis of Benzyl Malolactonate (BML) 24 2.1 .2 Catalyst Preparations 30 2.1.2.1 "In-situ Catalyst" of EW\I/H ? 0 32 2.1.2.2 Ethylaluminoxane, EAO. 32 2.1.2.3 Diethylzinc-Water Catalyst, Et 2 Zn/H 2 0 37 2.1 .2.4 (5,1 0,1 5,20-Tetraphenylporphinato) aluminum Chloride, TPPAICI 38 2.1.2.5 Catalyst Solutions 38 2.1.3 Polymerizations of Butyrolactone and Benzyl Malolactone 40 2.1.3.1 Optimization of the Polymerization Reactions 40 2.1.3.2 Homopolymerization of B-BL 42 2.1 .3.3 Homopolymerization of BML 55 * • Vll 2.1.4 Copolymerization of Racemic BL and BML 65 2.1.4.1 Copolymerization with the Aluminum-Water Catalysts 65 2.1.4.2 Copolymerization witn the Cataivsts ZnEt^O and TPPAICI 73 2.1.4.3 Comonomer Sequences of P(HB-co-BM)...'..'.'.'.'..75 2.2 Stereochemical Study on the Ring-Openinq Polymerization of B-Butyrolactone 82 2.2.1 Synthesis of Optically Active [Sl-B-BL 82 2.2.2 Optical Purity of the S]-6-BL... .... 89 2.2.3 Synthesis of the Optically Active Polymers from [S]-3-BL 94 2.2.3.1 Characterization of the Synthetic Optical Polymers 96 2.2.3.2 Fractionation of the Optical Active Polymer 101 2.2.4 Polymerization of [S]-3-BL with EtoAIOAIEt? 105 2.2.5 Stereoisomeric Purity of the Synthetic PHB. 107 2.2.6 Mechanism of the Ring-Opening Polymerization 111 References 115 3. EXPERIMENTAL..., 120 3.1 Reagents and Solvents 120 3.2 Monomer Preparations 120 3.2.1 Synthesi of Racemic Benzyl Malolactone 121 3.2.2 Synthesis of Optically Active [S]-3-Butyrolactone 122 3.3 Catalyst Preparations 127 3.3.1 Determination of EtoAl Concentration 127 3.3.2 "In-situ" Preparation of Et AI/H 129 3 2 0 3.3.3 Ethylaluminoxane (EAO), Metnylaluminoxane (MAO) and Iso-Butylaluminoxane (IBAO) 129 3.3.4 Diethylzinc Water Catalyst Et2 Zn/H 2 0 131 3.3.5 (5,10,15,20-Tetraphenylporphinato) Aluminum Chloide, (TPPJAICI 131 3.3.6 Tetraethyl (Et AI) Aluminoxid 2 2 0 133 3.4 Polymer Preparations 134 3.4.1 General Procedure 1 34 3.4.2 Polymer Purification and Fractionation 134 3.4.3 Polymer Characterization 135 viii 137 138 138 139 141 3.5 Degradation of the Optically Active Polymers by Methanolysis 3.6 Optical Purity Measurements 1 3.6.1 H NMR Spectra with an Europium Shift Reagent 3.6.2 Specific Rotations Z.ZZ References 4. RECOMMENDED FUTURE WORK APPENDICES A. INFRARED AND FTIR SPECTRA B. PROTON NMR SPECTRA C. CARBON-13 NMR SPECTRA BIBLIOGRAPHY ix LIST OF TABLES Table 2.1 The degree of polymerization of oligomeric alkylaluminoxane, -[AlRO] n - 36 2.2 The polymerization of [R,S]-BL using the I aluminum-water catalysts 43 2.3 Metal (Al or Zn) contents in the catalysts and polymer fractions 47 2.4 The polymerization of [R,S]-R-BL & BML using the catalyst ZnEt /H O (1.0/0.6) and the polymer characterization. .„ 55 2.5 The polymerization of BL and BML using the catalyst TPPAICI and polymer characterization 57 2.6 The polymerization of [R,S]-BML using the aluminum-water catalysts 60 2.7 Copolymerization of [R,S]-BL and BML using the aluminum-water catalysts 66 2.8 Experimental