The Use of Heterocomplementary Hydrogen Bonding Motifs for Supramolecular Materials Chemistry Kelly Ann Houton Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Chemistry March 2015 Intellectual Property and Publication Statements The candidate confirms that the work submitted is her own, except where work, which has formed part of jointly-authored publications, has been included. The contribution of the candidate and the other authors to this work has been explicitly indicated below. The candidate confirms that appropriate credit has been given within the thesis where reference has been made to the work of others. Chapter 1- Introduction; adapted from a review article ‘Hydrogen-bonded polyurethanes’, Houton, K.A and Wilson, A. J. Polymer International, 2015; 64, 165-173. The contributions of the authors are as follows: KAH (the candidate) wrote the corresponding sections of the review and produced related figures, whilst AJW edited the manuscript into its present form. Chapter 2- Light-triggered supramolecular self-sorting cascades; the work reported in this chapter formed part of a research paper ‘Sequential and Photo triggered Supramolecular Self-Sorting Cascades Using Hydrogen-Bonded Motifs’, Chemical Science, 2013, 4, 1825-1829. The contributions of the authors are as follows: AJW, MLP and KAH (the candidate) designed the research, KAH (the candidate) performed the research and characterisation of AIC motifs appended with a light- cleavable motif, and drafted the corresponding section of the manuscript. MLP performed the non-triggered self-sorting experiments and AJW edited the manuscript into its present form. Chapter 3- Mechanical properties of supramolecular polymers; the work reported in this chapter formed part of a research paper ‘Tuneable Self-Assembled Elastomers Using Triply Hydrogen-Bonded Arrays’, Macromolecules, 2012, 45, 4723-4729. The contributions of the authors are as follows: AJW, AG, CIL, AS, CN and KAH (the candidate) designed the research, KAH (the candidate) performed the research and characterisation of control compounds bearing mismatching hydrogen bonding ii motifs and their assembly behaviour, and drafted the corresponding section of the manuscript. AG synthesised and characterised all supramolecular polymers assembled using the DAC motif with the UIM macromonomer. CN aided characterisation and performed compression moulding. CIL, AS and AJW edited the manuscript into its present form. Chapter 4- Reducing the environmental impact of polyurethane synthesis; the work reported in this chapter formed part of a research paper: ‘Development of Solvent- Free Synthesis of Hydrogen-Bonded Supramolecular Polyurethanes’, Houton, K.A, Burslem, G.M and Wilson, A. J. Chemical Science, 2015, 6, 2382. The contributions of the authors are as follows: KAH (the candidate) and AJW designed the research, KAH (the candidate) performed the research on 1-propanol and PEG based reactions and produced related figures, GMB performed research on the ether diol and produced related figures, whilst AJW edited the manuscript into its present form. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. The right of Kelly Ann Houton to be identified as Author of this work has been asserted by her in accordance with the Copyright, Designs and Patents Act 1988. ©2015 Kelly Ann Houton and The University of Leeds iii Acknowledgments Thank you primarily to Professor A.J. Wilson, for the support and guidance throughout the whole of this project. The dynamic of the Wilson Group can only be attributed to your exceptional judgement of character. I’ll never forget the many Christmas dinners, summer trips, barbeques, group welcome drinks and of course interesting discussions with Huntsman. Tremendous thanks to all Wilson members past and present. Especially my original next-hood-neighbour Maria, my H-bond sister! To Kérya, Tasha and Panchami for welcoming me into the office and the lab. I will always listen to Taylor Swift and the eHarmony ‘I love cats’ song with fond memories. To George P, for always making coffee and playing Smashing Pumpkins in the lab. Dave, Valeria, Phil and Giorgia for our long days building a pretty awesome imaginary company- and all the laughs/trials we had along the way. Sarah, for addressing the vegetarian vs. meat-eaters balance within the group. The ‘foreign office’ members: Irène, for just being you- letting us draw on your house, always getting too drunk and always speaking the truth. Jayapal- purely for your amazing giggle. Even when you’re stressed you still look happy. Sìlvìa for always looking out for my best interests, I knew we’d always be friends from the first day you came into the lab and I cleared that desk for you. To our lab parents, Ludwig and Anna, for showing us the light at the end of the tunnel and that it was possible to achieve a PhD. George Burslem, my brother from another mother (told you I’d write it!). Thank you for all the pints, pep talks, uncomfortable (for you) hugs, cups of tea, cake, encouragement and inventive obscenities. I definitely wouldn’t have got this far alone. To Steven Kane, we’ll never remember how we became friends, but I’m glad we did. Thank you also for all the pints and half pints, advice and agony-aunting, cups of coffee, nights out, memes and lab visitations. I’m sorry I broke your ankle, but it cemented our friendship for sure. iv To the best MChem ever, Aisling, who became a true friend. To Dr. “Sri” Sridharan, for always telling me I was Andy’s favourite and I worked too hard. With the greatest thanks to my family; my mum who always called this thesis “homework” and my sister Corrie who always knew someone who ‘might do something like you talked about once’. The inspiring teachers who led me to a Chemistry degree in the beginning… Dr. Hanmer, Mrs. Hennah and Mrs. Harris. The Core- de Bray and Tayler- we went our separate ways after Southfields and scattered ourselves across the country in the process, but we’ve never lost our closeness. Thank you for all the Skypes, escapes to different cities and most of all for always lending an ear. Last but not least, thank you to my future husband, Matthew Squires, to whom this thesis is dedicated. As my best friend and non-scientist, I appreciate the patience you’ve had with the long hours I’ve worked the past 3 years. You have supported me through the highs and lows of this PhD, and I’m not sure I could have completed it without you. We took a few big steps together during my time at Leeds and I can’t wait for our next one. v Abstract Hydrogen bonding is one of the most useful of the non-covalent interactions. Highly directional and easily tuneable, the strength of hydrogen bonded arrays enable controlled assembly of macromolecular structures. Because association can be designed to be selective, self-assembly involving low-molecular-weight amides and ureas has been expanded to higher order polymeric structures, so called ‘supramolecular polymers’. Chapter 1 introduces and develops upon the current themes of research in small-molecule hydrogen bonding, and the subsequent application towards the assembly of supramolecular polymers, in particular polyurethanes. The Wilson group is focused on the development of orthogonal recognition pathways, and their future application in the controlled assembly of polymers. The work presented in this thesis, therefore focuses on the development of self-sorting cascades- where molecules capable of hydrogen bonding have defined partners at specific stages of the cascade. Selecting two heterocomplementary hydrogen bonding arrays, and using them to form supramolecular polymers then advance this. Chapter 2 introduces the design and investigation of these self-sorting pathways involving hydrogen bonding arrays reported both in the literature and from within the Wilson group. The application of two of these hydrogen bonding motifs to assemble supramolecular polyurethanes is described in Chapter 3. The effect of the thermal history of supramolecular polyurethanes is then investigated, highlighting the change in response to thermal stimuli dependent on previous processing and treatment. The latter part of Chapter 3 introduces a ‘toolbox’ for supramolecular chemists, whereby components of the supramolecular polymer are changed systematically to gauge effect on subsequent mechanical properties. The synthetic route to supramolecular polymers is then discussed in Chapter 4, and the evolution of a solvent-free route to this particular class of polyurethanes is realised. vi Table Of Contents 1 Introduction ...................................................................................................... 2 1.1 Covalent Polymers .................................................................................... 2 1.1.1 Step-Growth and Chain- Growth Polymerisation ............................ 3 1.1.2 Condensation Polymerisation .......................................................... 5 1.1.3 Polyurethanes ................................................................................... 5 1.2 Supramolecular Polymers ......................................................................... 7 1.2.1 Controlling hydrogen bond strength .............................................. 10 1.2.2 Homocomplementary hydrogen bonding motifs for supramolecular polymers ..............................................................