Vinyl Ether Functional Polyurethanes as Novel Photopolymers Dissertation zur Erlangung des Grades „Doktor der Naturwissenschaften” im Promotionsfach Chemie am Fachbereich Chemie, Pharmazie und Geowissenschaften der Johannes Gutenberg-Universität Mainz Stefan Kirschbaum geboren in Köln Mainz, 2015 Dekan: 1. Berichterstatter: 2. Berichterstatter: Tag der mündlichen Prüfung: 17. Dezember 2015 Ich versichere, die als Dissertation vorliegende Arbeit selbstständig angefertigt zu haben und alle verwendeten Quellen und Hilfsmittel kenntlich gemacht zu haben. Die vorliegende Arbeit wurde von Oktober 2012 bis November 2015 unter Betreuung von in Kooperation zwischen dem Max-Planck-Institut für Polymerforschung in Mainz und der Henkel AG und Co. KGaA in Düsseldorf angefertigt. IV Introduction Table of Content 1 Introduction .......................................................................................................... 1 2 Theoretical Background ...................................................................................... 5 2.1 Basic Considerations of Photocuring ........................................................................ 5 2.1.1 Photoinitiation and Electronic States ............................................................................ 6 2.1.2 Cationic Photoinitiators .............................................................................................. 11 2.1.3 Photoinduced Cationic Polymerization ...................................................................... 14 2.1.4 Photoinduced Radical Polymerization of Acrylates ................................................... 19 2.1.5 Photoinduced Thiol-Ene Curing ................................................................................. 22 2.2 Chemistry of Vinyl Ethers ...................................................................................... 25 2.2.1 Technical Synthesis and Availability ......................................................................... 25 2.2.2 Properties and Reaction Capabilities .......................................................................... 29 2.3 Chemistry of Polyurethanes .................................................................................... 32 2.3.1 Technical Considerations ........................................................................................... 36 2.3.2 Polyhydroxyurethanes (PHUs) ................................................................................... 38 2.4 Chemistry of Benzoxazines .................................................................................... 42 3 Characterization Techniques ............................................................................ 47 3.1 Differential Scanning Calorimetry (DSC) .............................................................. 47 3.1.1 Temperature Modulated DSC ..................................................................................... 48 3.1.2 Photo-DSC .................................................................................................................. 49 3.2 Real Time (Near) Infrared Spectroscopy ................................................................ 50 3.3 Rheology ................................................................................................................. 51 3.3.1 Photorheology............................................................................................................. 52 3.3.2 UV/NIR-Rheology ..................................................................................................... 53 4 Results and Discussion ....................................................................................... 55 4.1 Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks.......... 57 4.1.1 Motivation .................................................................................................................. 58 4.1.2 Synthesis of VEPUs ................................................................................................... 59 4.1.3 Radiation Curing of VEPUs ....................................................................................... 60 4.1.4 Vitrification Induced Curing Time Out and Thermal Post-Curing ............................. 65 4.1.5 Durability of Trapped Cationic Chain-Ends ............................................................... 66 4.1.6 Influence of the Curing Conditions on the Network Structure ................................... 67 4.1.7 Conclusion and Outlook ............................................................................................. 68 4.2 Vinyl Ether Functional Polyols as Building Blocks for UV-Curable Polyurethanes and Isocyanate-Free Polyhydroxyurethanes .................................... 69 Introduction V 4.2.1 Motivation ................................................................................................................... 70 4.2.2 Synthesis of Urethane Containing VEOHs ................................................................. 71 4.2.3 Synthesis and UV-Curing of Novel VEPUs ................................................................ 73 4.2.4 Polyhydroxyurethanes via Thiol-Ene Addition of Urethane Containing VEOHs ....... 76 4.2.5 Conclusion and Outlook .............................................................................................. 78 4.3 Synergistic and Sequential Dual Curing Mechanism for Vinyl Ether Functional Polyurethanes ........................................................................................ 79 4.3.1 Motivation ................................................................................................................... 80 4.3.2 Synthesis and Curing of Isocyanate Terminated VEPUs ............................................ 82 4.3.3 Conclusion and Outlook .............................................................................................. 86 4.4 Cationic Phototransfer Polymerization: pH-Responsive Acetal-Based Polymer Networks .................................................................................................................. 87 4.4.1 Motivation ................................................................................................................... 88 4.4.2 Mechanism of Cationic Phototransfer Polymerization ................................................ 89 4.4.3 Addition of Difunctional Alcohols .............................................................................. 91 4.4.4 Addition of Monofunctional Alcohols ........................................................................ 93 4.4.5 Conclusion and Outlook .............................................................................................. 98 4.5 Cationic Phototransfer Polymerization of Photocurable Polyhydroxyurethanes..... 99 4.5.1 Motivation ................................................................................................................... 99 4.5.2 Synthesis of the VEPHU ........................................................................................... 102 4.5.3 Cationic Curing of the VEPHU ................................................................................. 105 4.5.4 Conclusion and Outlook ............................................................................................ 110 4.6 Synthesis and Thermal Curing of Benzoxazine Functionalized Polyurethanes .... 111 4.6.1 Motivation ................................................................................................................. 112 4.6.2 Synthesis and Oligomerization of the P-m ................................................................ 114 4.6.3 Benzoxazine Functionalization of the Polyurethane ................................................. 121 4.6.4 Curing of the Polyurethane/Benzoxazine-Hybrids .................................................... 123 4.6.5 Conclusion and Outlook ............................................................................................ 124 5 Experimental Section ...................................................................................... 126 5.1 Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks ........ 126 5.1.1 Materials .................................................................................................................... 126 5.1.2 Synthesis of Vinyl Ether Polyol (VEOH).................................................................. 126 5.1.3 Synthesis of the Hydrogenated Vinyl Ether Polyol (h-VEOH) ................................. 128 5.1.4 General Synthesis Procedure for Vinyl Ether Functionalized Polyurethanes (VEPUs) .................................................................................................................... 128 5.1.5 Formulation of the VEPUs with Photoinitiator ......................................................... 130 5.1.6 Size Exclusion Chromatography (SEC) .................................................................... 130 5.1.7 UV/NIR-Rheology .................................................................................................... 131 5.1.8 Differential Scanning Calorimetry (DSC) ................................................................. 132 5.1.9 Comparability of UV/NIR-Rheology and Photo-DSC .............................................. 132 5.2 Vinyl Ether-Functional Polyols as Building Blocks for UV-Curable Polyurethanes and Isocyanate-Free