Reaction-Induced Phase Separation of PPG/PEO/HDI based bi-Soft Segment Polyurethanes I n a u g u r a l - D i s s e r t a t i o n zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Universität zu Köln vorgelegt von Christian Wenning aus Emsbüren Köln, 2018 Berichterstatter/in: Prof. Dr. Annette M. Schmidt Prof. Dr. Marc C. Leimenstoll Tag der letzten mündlichen Prüfung: 24. Mai 2017 Danksagung An dieser Stelle möchte ich mich besonders bei Prof. Dr. Marc C. Leimenstoll für das Vertrauen mir gegenüber in der Bearbeitung des Themas bedanken. Besonderen Dank möchte ich aussprechen für die gebotene Offenheit in der Gestaltung der Arbeit, für die dies betreffenden konstruktiven Diskussionen und für die immerwährende Hilfsbereitschaft. Mein besonderer Dank gilt außerdem Prof. Dr. Annette M. Schmidt für die Betreuung meiner Arbeit als Erstgutachterin seitens der Universität zu Köln. Vielen Dank für die Aufnahme in die freundliche Arbeitsgruppe und für die stetige, konstruktive Beratung in jedweden Belangen. Der Covestro Deutschland AG danke für die Bereitstellung der verwendeten Polyurethanrohstoffe. Hier geht außerdem mein herzlicher Dank an Dr. Dirk Achten, Dr. Dick Dijkstra und Dr. Hans Grablowitz für die fachlichen Diskussionen im Laufe des Projektes. Prof. Dr. Stéphan Barbe möchte ich zum einen für seine Hilfestellung im Rahmen der Berechnung der Phasendiagramme und zum anderen für die intensiven Diskussionen über die daraus entstandenen Ergebnisse danken. Außerdem danke ich Jens Noe für die Unterstützung dieser Arbeit durch die Erstellung seiner Masterarbeit unter meiner Leitung. Weiterhin bedanke ich mich bei meinen Kolleginnen und Kollegen für das freundliche Arbeitsklima und die konstruktiven Diskussionen. Zu guter Letzt möchte ich mich herzlich bei meiner Familie, insbesondere meinen Eltern Agnes und Werner für die fortwährende Unterstützung danken. Besonderer Dank gilt meiner Freundin Jessica für ihren unermüdlichen Rückhalt und ihre Geduld. Table of Contents I Abstract ........................................................................................................................... i II Kurzzusammenfassung .................................................................................................. ii III Abbreviations and symbols .......................................................................................... iii 1 Introduction ................................................................................................................... 1 2 Scope of this study and objectives ................................................................................. 3 3 Theory ............................................................................................................................ 5 3.1 Polyurethane chemistry ........................................................................................... 5 3.1.1 Isocyanate chemistry ............................................................................................. 5 3.1.2 Catalysis ................................................................................................................ 8 3.1.3 Polyether polyols .................................................................................................. 9 3.1.4 Isocyanate-terminated polyurethanes.................................................................. 10 3.1.5 Morphology of polyurethanes ............................................................................. 12 3.2 Solubility parameters ............................................................................................. 14 3.2.1 Definition ............................................................................................................ 14 3.2.2 Determination of solubility parameters .............................................................. 15 3.3 Flory-Huggins lattice theory .................................................................................. 20 3.3.1 Definition and function ....................................................................................... 20 3.3.2 Estimation of phase diagrams ............................................................................. 21 4 Results and discussion ................................................................................................. 23 4.1 Ternary phase diagram of PPG/PEO/HDI mixtures .............................................. 23 4.1.1 The binary mixture of PPG/PEO ........................................................................ 23 4.1.2 Phase diagram of the ternary mixture PPG2k/PEO600/HDI .............................. 29 4.1.3 Summary on PPG/PEO/HDI phase diagrams ..................................................... 36 4.2 Reaction kinetics, phase behaviour and properties of PPG/PEO bi-soft segment polyurethanes ......................................................................................................... 38 4.2.1 Kinetics of the reaction in ternary PPG/PEO/HDI mixtures .............................. 39 4.2.2 Onset of phase separation ................................................................................... 49 4.2.3 Thermal properties and glass transitions of the ITPUs ....................................... 60 4.2.4 Molecular weight distribution of the ITPUs ....................................................... 64 4.2.5 Phase behaviour of the ITPU .............................................................................. 66 4.2.6 Summary on the reaction-induced phase separation in PPG2k/PEO600/HDI reaction mixtures ................................................................................................. 78 5 Conclusion and outlook ............................................................................................... 79 6 Experimental part ........................................................................................................ 83 6.1 Materials ................................................................................................................ 83 6.2 Analytical methods ................................................................................................ 85 6.3 Synthesis of isocyanate-terminated polyurethanes ................................................ 88 6.4 Phase isolation and composition analysis ............................................................. 89 6.5 Determination of the solubility parameters ........................................................... 90 6.6 Determination of cloud points ............................................................................... 93 6.7 Binodal composition analysis by size exclusion chromatography ........................ 93 6.8 Computational determination of phase diagrams .................................................. 94 7 References ................................................................................................................... 98 IV Appendix ................................................................................................................... 107 V Figures ....................................................................................................................... 129 VI Tables ........................................................................................................................ 131 I Abstract The presented thesis explores the physicochemical background of reaction-induced phase separation (RIPS) in bi-soft segment isocyanate-terminated polyurethanes (ITPUs). ITPUs are a preliminary product in the synthesis of various PU products like foams, dispersions or elastomers. Typically, only one soft segment is used but it was shown in the literature that the application of two different soft segments can lead to an improvement of morphological properties. In this work, it is hypothesized that the combination of two soft segments can lead to RIPS during the ITPU formation process. It is suggested that the occurrence and the extent of phase separation is closely related to the initial phase diagram of the reactants. In order to study the proposed relationship, the initial ternary phase diagram of the reaction mixture, consisting of poly (ethylene oxide) (PEO), poly (propylene oxide) (PPG) and 1,6-hexamethylene diisocyanate (HDI) is determined at first. Secondly, detailed experimental observation of the RIPS is conducted to identify critical parameters. Furthermore, the composition and morphology of the phase separated products are studied briefly. The ternary phase diagram is determined by theoretical and experimental methods. Flory- Huggins theory and solubility parameters are applied in order to calculate equilibrium compositions of demixed phases in the binary (PEO/PPG) and ternary (PEO/PPG/HDI) mixtures. The obtained data is in qualitative agreement with experimental cloud points and equilibrium compositions. The results demonstrate that HDI acts as a solvent for PEO and PPG. Reaction monitoring by NCO%-content titration, FTIR- and UV-Vis spectroscopy revealed a dependency between the onset of phase separation and the reaction conversion. It is found that an increase of the initial HDI content leads to a delayed onset of phase separation. The competing second order kinetic of the reaction is studied by 1H-NMR analysis. DSC analysis reveals that the phase separation is a consequence of the incompatibility of the soft segment structures. The composition and molar weight distribution found in isolated phases of the ITPUs indicate that the phase