FUNCTIONALIZATION OF HYPERBRANCHED POLYACRYLATES BY RADICAL QUENCHING A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Master of Science Zewei Wang May, 2014 FUNCTIONALIZATION OF HYPERBRANCHED POLYACRYLATES BY RADICAL QUENCHING Zewei Wang Thesis Approved: Accepted: Advisor Dean of the College Dr. Coleen Pugh Dr. Stephen Z.D. Cheng Faculty Reader Dean of the Graduate School Dr. Chrys Wesdemiotis Dr. George R. Newkome Department Chair Date Dr. Coleen Pugh ii ABSTRACT Hyperbranched polyesters have drawn great attention in many applications, including lubricants, paints, catalyst supports, and drug delivery. Similar to dendrimers, hyperbranched polymers have high branching densities which contribute to higher solubilities and lower viscosities as compared to linear polymers. Furthermore, they have a considerable amount of terminal functional groups throughout their structures, which contribute to their excellent ability to encapsulate molecules and act as a catalyst support. There are many publications on further grafting on hyperbranched polymers, but few reports on the modification of their end groups. This project concentrates on the synthesis of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) derivatives which will be coupled to the bromine end groups of hyperbranched poly(n-butyl acrylate) by nitroxide radical coupling (NRC). The substituted functional groups include hydroxy, alkene, azido, cyano and nitro groups. TEMPO derivatives are being synthesized from 4-hydroxy TEMPO to form ester or ether by multiple coupling methods such as DCC coupling, mesylation, and alkoxidation. Further nitroxide mediated radical polymerizations may be carried out to modify the behavior of the polymers, mostly by addition of styrenes. The hyperbranched polymers are being synthesized by self-condensing vinyl polymerization (SCVP) of a bromo acrylate inimer. iii TABLE OF CONTENTS Page LIST OF SCHEMES ........................................................................................................ vi LIST OF FIGURES ........................................................................................................ viii LIST OF TABLES ..............................................................................................................x CHAPTER Ⅰ. INTRODUCTION ........................................................................................................1 1.1 Hyperbranched Polyacrylates ...................................................................................1 1.2 Atom Transfer Radical Polymerization .....................................................................6 1.3 Atom Transfer Nitroxide Radical Coupling ............................................................11 1.4 TEMPO and Its Derivatives ....................................................................................15 1.5 Model Compound for Hyperbranched Polyacrylate................................................18 II. EXPERIMENTS .........................................................................................................20 2.1 Materials .................................................................................................................20 2.2 Techniques ..............................................................................................................21 2.3 Synthesis Procedures ..............................................................................................22 III. RESULTS AND DISCUSSION ................................................................................. 39 1 13 3.1 H and C NMR Spectra ........................................................................................39 iv 3.2 Nitroxide Radical Coupling Results .......................................................................67 IV. CONCLUSION .......................................................................................................... 70 REFERENCES .................................................................................................................71 APPENDIX .......................................................................................................................75 v LIST OF SCHEMES Scheme Page 1.1 Synthesis of Hyperbranched Polyacrylates from Inimers ......................................3 1.2 Synthetic Route of Acrylate Inimer .......................................................................4 1.3 Use of Hyperbranched MIs for Synthesis of “Hyper-star” Polymers ....................5 1.4 ATRP Equilibrium ..................................................................................................6 1.5 Mechanism of Reverse ATRP ................................................................................8 1.6 Illustration of SR&NI and AGET ..........................................................................8 1.7 Illustration of ICAR and ARGET ........................................................................10 1.8 Mechanism of Nitroxide Radical Coupling .........................................................12 1.9 Synthetic Mechanism for Poly(GTEMPO-co-EO)-g-PS by Atom Transfer Nitroxide Radical Coupling Chemistry ................................................13 1.10 The Illustration of Two Synthetic Routes for the Comb-like Block Copolymers .........................................................................................................13 1.11 Synthetic Route to Functionalized Hyperbranched Polyacrylates .......................14 1.12 Synthesis of Other Nitroxides form TEMPO-OH ...............................................16 1.13 Detailed Synthetic Routes for all TEMPO Derivatives .......................................18 2.1 Synthesis of 2-bromo-3-hydroxypropionic acid ..................................................22 2.2 Synthesis of n-butyl 2-bromo-3-hydroxypropionate ...........................................23 vi 2.3 Synthesis of n-butyl 3-acetoxy-2-bromopropionate (model compound) .............24 2.4 Synthesis of Acrylic Anhydride ...........................................................................25 2.5 Synthesis of (2-bromo-2-n-butoxycarbonyl)ethyl acrylate ..................................25 2.6 Polymerization of (2-bromo-2-n-butoxycarbonyl)ethyl acrylate (standard ATRP) ....................................................................................26 2.7 Polymerization of (2-bromo-2-n-butoxycarbonyl)ethyl acrylate (AGET ATRP) .......................................................................................27 2.8 Synthesis of 2,2,6,6-tetramethyl-[4-yl-(4-methanesulfonate)] piperidine-1-oxyl .................................................................................................28 2.9 Unsuccessful synthesis of 4-acryloxy-2,2,6,6-tetramethyl- piperidine-1-oxyl from acrylic acid ....................................................................29 2.10 Synthesis of 4-acryloxy-2,2,6,6-tetramethylpiperidine-1-oxyl from acryloyl chloride .........................................................................................29 2.11 Unsuccessful synthesis of 4-(3-chloropropionyloxy)- 2,2,6,6-tetramethylpiperidine-1-oxyl ..................................................................30 2.12 Synthesis of 4-(4-Nitrophenylacetyloxy)- 2,2,6,6-tetramethylpiperidine-1-oxyl ..................................................................31 2.13 Synthesis of 4-(6-bromohexanoyloxy)-2,2,6,6-tetramethylpiperidine-1-oxyl .....32 2.14 Synthesis of 4-(6-azidohexanoyloxy)-2,2,6,6-tetramethylpiperidine-1-oxyl ......33 2.15 Synthesis of 4-(6-cyanohexanoyloxy)-2,2,6,6-tetramethylpiperidine-1-oxyl .....34 2.16 Synthesis of HTEMPO quenched model compound ...........................................35 2.17 Synthesis of 4-acryloxy-TEMPO quenched model compound ...........................36 2.18 General procedure of ATNRC ..............................................................................37 vii LIST OF FIGURES Figure Page 1.1 Six Different Types of Dendritic Structures ..........................................................2 1.2 Kinetic Plot (left) and Molecular Weight (lower Right) and Mw/Mn a (upper right) as a Function of Conversion in the CuCl2/TPMA -Mediated b ARGET ATRP of BA , with Variable Hydrazine (N2H4) Reducing Agent ...........10 1.3 Model Compound for Hyperbranched Polyacrylate ............................................19 3.1 1H NMR spectrum of 2-bromo-3-hydroxypropionic acid ...................................39 3.2 1H NMR spectrum of n-butyl 2-bromo-3-hydroxypropionate .............................40 3.3 1H NMR spectrum of n-butyl 3-acetoxy-2-bromopropionate ..............................41 3.4 1H NMR spectrum of acrylic anhydride ..............................................................42 3.5 1H NMR spectrum of (2-bromo-2-n-butoxycarbonyl)ethyl acrylate ...................43 3.6 13C NMR spectrum of (2-bromo-2-n-butoxycarbonyl)ethyl acrylate ..................44 3.7 1H NMR spectrum of poly(2-bromo-2-n-butoxycarbonyl)ethyl acrylate ............45 3.8 1H and 13C NMR spectrum of 4-mesyl-TEMPO .................................................46 3.9 1H and 13C NMR spectrum of 4-acryloxy-TEMPO synthesized from acryloyl chloride .........................................................................................48 3.10 1H and 13C NMR spectrum of 4-(4-nitrophenylacetyloxy)-TEMPO ...................50 3.11 1H and 13C NMR spectrum of 4-(6-bromohexanoyloxy)-TEMPO ......................52 3.12 1H and 13C NMR