SCHOOL OF CHEMISTRY CARDIFF UNIVERSITY Microporous Polymers Containing Tertiary Amine Functionality for Gas Separation Membrane Fabrication Thesis submitted for the degree of Doctor of Philosophy by: Richard Malpass-Evans Supervisor: Neil B. McKeown 2014 Preface Declaration This work has not been submitted in substance for any other degree or award at this or any other university or place of learning, nor is it being submitted concurrently in candidature for any degree or other award. Signed ………………………………………… (candidate) Date ………………………… Statement 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD). Signed ………………………………………… (candidate) Date ………………………… Statement 2 This thesis is the result of my own independent work/investigation, except where otherwise stated. Other sources are acknowledged by explicit references. Any views expressed are my own. Signed ………………………………………… (candidate) Date ………………………… Statement 3 I hereby give consent for my thesis, if accepted, to be available for photocopying and for inter-library loan, and for the title and summary to be made available to outside organisations. Signed ………………………………………… (candidate) Date ………………………… i Preface Acknowledgements First and foremost, I would like to thank my supervisor, Professor Neil McKeown, for giving me the opportunity to join his research group and for his constant guidance and support throughout my MChem, PhD and PDRA position. Special thanks should also go to Lino, Grazia and Kadhum for their guidance and support. I would also like to thank everyone who has made lab 1.107A a friendly and fun place to work over the past five years: Alaa, Alex, Ali, Ben, Heulyn, Ian, James, Jono, Luke, Matt, Mike, Mo, Rhodri, Rhys, Rupert, Sabeeha, Sadiq and Yulia. A big thanks to all our collaborators, especially Johannes (John) Jansen and everyone at ITM CNR for measuring the transport parameters of our membranes. I would like to thank Dr. Rob Jenkins, Robin Hicks, Dave Walker, Gaz Coleman, Simon James and all of the technical staff within the School of Chemistry, for their expertise and willingness to help at any given moment. I would also like to thank Dr. Benson Kariuki and Grazia for measuring and solving the crystal structures featured in this thesis. I would like to thank my family and friends for their love and support, especially my wife Ellie for putting up with me working evenings and weekends and my son William for letting me get just enough sleep to complete this thesis on time. Finally I would like to thank the European Commission for funding under the Doublenanomem project (Nanocomposite and Nanostructured Polymeric Membranes for Gas and Vapour Separations), a collaborative research project under the EU’s Seventh Framework Programme. ii Preface Abstract This research reported in this thesis is based on the synthesis of novel polymers of intrinsic microporosity (PIMs) with the aim of fabricating membranes for gas separation applications. PIMs are composed of rigid and awkwardly-shaped monomeric segments which lack the conformational and rotational freedom needed to pack space efficiently. As a result these polymers display high BET surface areas and display excellent gas permeabilities when solution-cast into films which can be used as gas separation membranes. This thesis describes the synthesis of a range of aromatic diamine, tetraamine, dianhydride, and dicarboxylic acid monomers that conform to the PIM design concept, featuring rigid and contorted architectures. These monomers were then used to synthesise five classes of polymer featuring tertiary amine functionality. Structure-property relationships were established between these polymers and BET surface area measurements. Polymers that displayed adequate film forming properties were also evaluated by our collaborators at The Institute of Membrane Technology for their gas transport parameters. Chapter 6 describes the synthesis of a new class of polymer, Tröger's Base PIMs, featuring a novel polymerisation reaction using chemistry first reported 127 years ago. One of these polymers, DMEA.TB, displays a BET surface area of 1028 m2/g which is the highest recorded for any soluble polymer to date. DMEA.TB places gas permeation data for technologically important gas pairs far over the present Robeson upper bound and has unrivalled potential to separate mixtures containing hydrogen. Chapter 7 deals with quaternerisation and subsequent ion exchange of selected Tröger's Base polymers. Chapter 8 discusses the synthesis of three novel polyimides using highly rigid and contorted ethanoanthracene monomers containing methyl groups that restrict rotation around polymer segments. These polymers display only moderate gas permeation characteristics and possess BET surface areas of up to 694 m2/g. Chapter 9 describes the synthesis of a new class of zwitterionic polysquaraines however, these polymers were shown to be non-porous due to strong ionic/hydrogen bonding. Chapter 10 describes the synthesis of polybenzimidazoles using the PIM design concept but it was found that extensive hydrogen bonding reduces free volume, forming non porous solids. Chapter 11 describes the synthesis of novel polypyrrolones with surface areas of up to 284 m2/g however, film formation was not possible with these materials. Chapter 12 features a brief investigation onto the cross-linking of a Tröger's Base membrane using hydrolysed PIM-1 as polyanionic counterion. iii Preface Abbreviations 4MPDA Tetramethylphenyldiamine IUPAC International Union of Pure and Applied Chemistry 6FDA Hexafluoroisopropylidene Lit Literature diphthalic anhydride AIBN Azobisisobutyronitrile MALDI Matrix Assisted Laser Desorption Ionisation Anth Anthracene min Minute(s) APCI Atmospheric pressure chemical M Number average molecular weight n ionisation Asymm Asymmetric MOF Metal Organic Framework Benz Benzene MTR Membrane Technology and Research, Inc BET Brunauer, Emmett and Teller Mw Weight average molecular weight BTFSI Bistrifluoromethanesulfonimide NDSA Naphthalenedisulfonic acid COF Covalent Organic Framework NMDCEA N-methyldicarboximide ethanoanthracene DCE Dichloroethane NMP N-methyl pyrrolidone DCEA Dichloroethanoanthracene NMR Nuclear Magnetic Resonance DCM Dichloromethane OMIM Organic Molecule of Intrinsic Microporosity DEEEA Diethyl ester ethanoanthracene PAAA Polyamide amino acid DHEA Dihydroethanoanthracene PAN Polyacrylonitrile DIM Dendrimer of Intrinsic PBI Polybenzimidazole Microporosity DMAc N,N-Dimethylacetamide Pc Phthalocyanine DMAnth Dimethylanthracene PDI Polydispersity index DMDPM Dimethylphenylmethane PDMS Polydimethylsiloxane DMEA Dimethylethanoanthracene PI Polyimide DMF N,N-Dimethylformamide PIM Polymer of Intrinsic Microporosity DMN Dimethylnaphthidine PPA Polyphosphoric acid DMSO Dimethylsulfoxide Ppy Polypyrrolone DPM Diphenylmethane PSQU Polysquaraine DSC Differential scanning calorimetry PTFE Polytetrafluoroethylene Fig Figure PTMSP Polytrimethylsilylpropyne IR Infrared spectroscopy SBI Tetramethylspirobisindane GPC Gel Permeation Chromatography Symm Symmetric h Hour(s) TB Tröger’s base HCP Hyper-cross-linked polymer TFA Trifluoroacetic acid HFIP Hexafluoroisopropylidene dianiline TGA Thermal gravimetric Analysis HMEA Hexamethylethanoanthracene THF Tetrahydrofuran HPLC High performance liquid TLC Thin Layer Chromatography chromatography HRMS High Resolution Mass TMEA Tetramethylethanoanthracene Spectrometry IMFV Internal molecular free volume TMPI Trimethylphenylindane IPA Isopropyl alcohol TOF Time of flight ITM Institute of Membrane Technology ZTC Zeolite templated carbons iv Preface Table of Contents Declaration................................................................................................................................. i Acknowledgements .................................................................................................................. ii Abbreviations .......................................................................................................................... iv Chapter 1: Introduction .......................................................................................................... 1 1.1: Porous Materials ............................................................................................................. 1 1.2: Microporous Materials .................................................................................................... 2 1.3: Zeolites ............................................................................................................................ 2 1.4: Metal-Organic Frameworks ............................................................................................ 4 1.5: Covalent Organic Frameworks ....................................................................................... 5 1.6: Activated Carbons ........................................................................................................... 6 1.7: Hyper Cross-Linked Polymers ........................................................................................ 7 1.8: Polymers of Intrinsic Microporosity ............................................................................... 8 1.8.1: Linear Polymers ..................................................................................................... 12 1.8.1.1: Polyacetylenes ................................................................................................. 12 1.8.2: PIM Polyimides ...................................................................................................... 13 1.8.3: Ladder Polymers .................................................................................................... 15 1.8.3.1: PIM-1 ............................................................................................................... 15 1.8.3.2: PIM-7 ............................................................................................................... 17 1.8.4: Network Polymers .................................................................................................. 18 1.8.4.1: Triptycene Network PIMs ............................................................................... 18 1.8.4.2: Phthalocyanine Network PIMs ........................................................................ 19 Chapter 2: Background Theory ........................................................................................... 21 2.1: Determination of Surface Area ..................................................................................... 21 2.2: Membrane Technology ................................................................................................. 26 2.3: Membrane Theory ......................................................................................................... 28 2.3.1: Mass Transport Through Membranes .................................................................... 28 2.3.2: Transport Parameters.............................................................................................. 31 2.4: Measurement of Transport Parameters ......................................................................... 35 Chapter 3: Research Aims .................................................................................................... 38 Chapter 4: Monomer Synthesis ............................................................................................ 39 4.1: 1,3,3-trimethyl-1-phenylindane .................................................................................... 39 4.2: Spirobisindanes ............................................................................................................. 40 4.3: Ethanoanthracenes ........................................................................................................ 41 4.3.1: Ethanoanthracene Compounds Derived from Anthracene ..................................... 41 4.3.2: Ethanoanthracene Compounds Derived from Diols............................................... 43 4.4: Carboxylic Acid Compounds ........................................................................................ 47 4.5: Dianhydride Compounds .............................................................................................. 48 4.6: Dinitro Compounds ....................................................................................................... 48 4.7: Tetranitro Compounds .................................................................................................. 50 4.8: Diamino Compounds .................................................................................................... 51 v Preface 4.9: Tetraamine Hydrochloride Salts ................................................................................... 54 4.10: Tetraamino Compounds .............................................................................................. 55 4.11: Diamine Hydrochloride Salts ...................................................................................... 55 4.12: 9,10-dimethyl-9,10-dihydro-2,6(7)-diamino-9,10-ethanoanthracene trifluoroacetate 56 Chapter 5: Polymer Synthesis............................................................................................... 56 Chapter 6: Tröger's Base Polymers ..................................................................................... 58 6.1: Tröger's Base ................................................................................................................. 58 6.2: Tröger's Base Polymerisation ....................................................................................... 60 6.3: Tröger's Base Polymers from Synthetic Monomers ..................................................... 62 6.3.1: DMEA.TB .............................................................................................................. 62 6.3.2: DHEA.TB ............................................................................................................... 71 6.3.3: DCEA.TB ............................................................................................................... 74 6.3.4: TMEA.TB .............................................................................................................. 75 6.3.5: Anth.TB .................................................................................................................. 77 6.3.6: TMPI.TB ................................................................................................................ 79 6.3.7: SBI.TB.................................................................................................................... 81 6.4: Tröger's Base Polymers from Commercial Monomers ................................................. 84 Chapter 7: Quaternerised Tröger’s Base Polymers ........................................................... 88 7.1: Tröger’s Base Polymer Methylation ............................................................................. 88 7.2: Ion Exchange ................................................................................................................ 89 7.2.1: Exchange with Fluoride ......................................................................................... 89 7.2.2: Exchange with Bistrifluoromethanesulfonimide (Bistriflimide)............................ 90 7.2.3: Exchange with 2,6-Naphthalene Disulfonic acid ................................................... 93 Chapter 8: Polyimides ........................................................................................................... 96 Chapter 9: Polysquaraines .................................................................................................. 102 Chapter 10: Polybenzimidazoles ........................................................................................ 106 Chapter 11:Polypyrrolones ................................................................................................. 110 Chapter 12: Preliminary Study of Cross-Linking DHEA.TB with PIM-1 ................... 118 Chapter 13: Conclusions ..................................................................................................... 123 Chapter 14: Experimental ................................................................................................... 125 14.1: General Methods and Equipment.............................................................................. 125 14.2: Monomer Synthesis .................................................................................................. 128 14.3: Polymers Synthesis ................................................................................................... 161 14.4: Membrane Cross-linking .......................................................................................... 185 Bibliography ......................................................................................................................... 189 Publications .......................................................................................................................... 196 vi Introduction Chapter 1: Introduction 1.1: Porous Materials A porous material is defined as a solid material that contains a void, cavity or interstice1 known as a pore. The structure of a pore can vary greatly depending upon the material or post treatment of that material. IUPAC (International Union of Pure and Applied Chemistry) defines pores by three parameters; size, shape and accessibility to an external fluid1. These factors influence the physical and chemical properties of that material and hence potential applications. Three classes of porous materials have been defined by IUPAC according to their pore size: Microporous (< 2 nm), Mesoporous (2-50 nm) and Macroporous (>50 nm)1. A sub-classification of pore size is accessibility (i.e. if the pore is open or closed). A closed pore (a in Fig 1.1a1) is inaccessible to external probes such as fluids and gas molecules. This type of pore influences only the macroscopic properties of a material such as bulk density and mechanical strength. Open pores (b, c, d, e and f in Fig 1.1a) possess an opening from the surface of the material. These type of pores are accessible to external probes, and therefore influence microscopic properties such as porosity and surface area. Fig 1.1a. Schematic Cross-Section of a Porous Solid. Open pores are further c lassified by their shape (c and f are cylindrical and b is "ink-bottled shaped" in Fig 1.1a, if a pore has only one opening (b and f) or if a pore penetrates the entire material (e). Rough surfaces (g) are not considered porous as convention states that irregularities must be deeper than they are wide to be defined as pores. 1 Introduction 1.2: Microporous Materials The smaller pore size a material possesses, the greater is the surface area to volume ratio of that material. It is for this reason that microporous materials have among the highest surface areas of all three classes of porous materials. High surface area materials have become of interest for a number of applications such as adsorption2, hydrogen storage3-5, gas purification4, 6, 7, liquid purification8, heterogeneous catalysis9-11, sensors12 and ion exchange13. Microporous materials can be sub-divided into two board classes: ordered crystalline materials and disordered amorphous materials. Ordered crystalline materials possess a long range order and have well defined pore structures which can be important factors for applications such as catalysis. Typical examples are zeolites, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). Amorphous materials usually possess little or no long-range order and have poorly defined pore structures. Typical examples include activated carbons, hyper cross-linked polymers (HCPs) and high free-volume polymers such as polymers of intrinsic microporosity (PIMs). There are however examples of amorphous materials that can be modified to demonstrate long range order such as zeolite templated carbons (ZTCs)14. Each of these materials possess their own unique properties and applications which will be discussed in the following sections. 1.3: Zeolites Zeolites are members of a large family of natural and synthetic microporous crystalline aluminosilicates discovered by the Swedish mineralogist Axel Fredrick Cronstedt. He noted in 1756 the ability of the mineral stilbite to absorb water and release it as steam upon heating. This observation led to the name zeolite, derived from the Greek words ‘zein’ (boiling) and ‘lithos’ (stone)15. Zeolites possess highly regular and well defined microporous cage-like framework structures. Zeolite frameworks can contain smaller sub-structures known as supercages and sodalite cages that form connected channels of roughly (1-20 Å) in diameter through the material. Zeolites are most commonly composed of tetrahedral silicate [SiO ]4- and aluminate [AlO ]5- 4 4 units connected through bridging oxygen atoms, although other compositions are known16. 2 Introduction The framework has a net negative charge due to the presence of [AlO ]5- units and this 4 enables the sub cage structures to accommodate a wide variety of loosely bound cationic species such as Na+, K+, Ca2+ and Mg2+. There are over 170 topologies known17 and one example is the Faujasite framework (X) [Al Si O ]·32(H O) where X= Na Ca or Mg (Fig 3.5 7 17 48 2 2, 1.3a9, 17). Fig 1.3a. Structure model of a Faujasite showing potential bonding positions of cations (types I, II and III). (left), Structure model of a Faujasite showing pore channels (right). Since their discovery 250 years ago zeolites have benefited many industries with their numerous applications: Zeolites have high thermal stability and upon removal of the adsorbed water by heating to 350-400 °C, zeolites remain highly stable frameworks10 with BET surface areas up to and in excess of 900 m2 g-1 18, 19. The high surface areas of zeolites combined with well-defined pore structures allows them to act as ‘molecular sieves’ in which external molecules are selectively adsorbed based on their size20. Guest cations can be readily exchanged for other species in solution. This has seen zeolites used in a number of ion exchange applications such as the treatment of liquid radioactive waste13. These guest cations may be utilised as evenly distributed catalytic sites that may be accessed selectively by reactants through the porous zeolite structure. For example, acidic zeolites (H+ counter ions) are commonly used in the petrochemical industry in the catalytic cracking of long chain hydrocarbons16, 21. The unique structure of a particular catalytic zeolite can be used to allow the shape and size of the pore system to exert a steric influence on reactants; a process known as “shape selective catalysis”11. 3