Search

The self-assembly of block co-polymers have led to the formation of a variety of structures such as vesicles, lamellae, micelles, bi-layers and many more types. Such self-assembled materials can find applications in catalysis, engineering, drug-delivery and many other fields. A specific class of these materials is silica and block co-polymer based periodic, porous materials. In this work, we study the phase behaviour of silica, block co-polymer Poly Ethylene Oxide12- b-Poly Butyl Methacrylate10 in a solvent (Tetrahydrofuran), co-solvent (water) system. This system was selected as there are experimental evidences that this system can form certain structures with specific characteristics suited to specific applications such as in controlled delivery systems. This work builds on the phase diagram of previously reported on the same polymer, water and tetrahydrofuran (THF). While it gave valuable insights on different morphologies of the self-assembled polymer structures, no information was available on the behaviour of such systems in the presence of silica. Molecular dynamics simulations have been employed to study these systems with coarse-grained models of different molecules. A new coarse-grained model of silica has been developed under the specific conditions at which the synthesis of these materials are observed experimentally. This new model of silica was then applied to build a quaternary phase diagram of block co-polymer PEO12-b-PBMA10, THF (solvent), water (co-solvent) and silica. This phase diagram showed that by introducing silica into the polymer, water and THF system generated a phase separation over a wide range, into polymer rich phase and solvent rich phase. This separation into two phases was observed even at low concentrations of silica, with the polymer forming different structures in the polymer rich phase.

Organic coatings protect metals from corrosion by acting as a barrier between the substrate and the environment. In addition to this passive mechanism, primer coatings also contain active corrosion inhibitors that leach out of the paint upon exposure to moisture and interfere with the corrosion reactions. Chromate-based inhibitors have been employed for decades due to their excellent corrosion protection properties, but are toxic and need to be replaced, although few alternatives show promising properties. However, the research has highlighted that the protection performance of a primer does not depend only on the effectiveness of the corrosion inhibitor, but also on the leaching kinetics. In addition, the process of inhibitor leaching is affected by the coating microstructure, which, in turn, is influenced by the coating formulation. This suggests the possibility to design optimised, chromate-free coatings by tuning their composition and microstructure in order to control the leaching of inhibitors and the protection performance during the service life. However, the relationship between formulation, microstructure and leaching kinetics is complex and still the object of research. The aim of this thesis is the development of a modelling approach to investigate the microstructure and leaching behaviour of primers, as a function of the coating formulation. The research methodology is based on the generation of virtual representations of coatings with given formulation parameters and on the subsequent simulation of the leaching process using the Cellular Automata method. The virtual coatings were characterised with suitably defined descriptors to investigate the effect of the formulation on the features of the pigment clusters, which are fundamental to the leaching mechanism. The analysis demonstrated the percolating nature of the clusters and suggested the importance of the percolation threshold as a critical factor in the design of a coating. The results of the microstructure characterisation and leaching simulation suggested that intervening on the pigment volume concentration and on the particles attributes (such as size distribution and shape) can be an effective way to control the properties and improve the performance of a primer. Furthermore, this work demonstrated the feasibility of a modelling approach in studying active protective coatings and suggested its potential applicability as a tool in the development of new formulations.

Carbon Monoxide (CO) is an important feedstock in the chemical industry. Current CO/N2 separation methods involve expensive cryogenic distillation or toxic solution separation techniques. Another promising alternative is to use solid adsorbents with open metal sites. PU-1, a Cu+ impregnated zeolite, has shown some industrial significance, however, no large scale implementation of this technology has yet been achieved. Metal organic frameworks (MOFs) are well suited to potentially replace current technologies due to their high porosity and capability to include a range of open metal sites suitable to selectively bind CO from N2. Recent advancements in the CO capacity have focused on the impregnation of frameworks with metal nanoparticles. Currently, the key structural features for MOFs to selectively adsorb CO have not been evaluated. Therefore, a study into a broad range of structural features is required for the understanding of the interaction of CO with a range of frameworks. A range of MOFs have been studied for their CO/N2 interaction using a gravimetric approach. These include archetypal MOFs, such as HKUST-1 and MIL-100(Fe), which show a range of selectivities calculated from the ideal adsorbed solution theory. It has been shown that a high heat of adsorption, dependent on the metal element and its oxidation state, improves the selective adsorption of CO. It was also revealed the relationship between the pore dimensions and N2 adsorption indicating lower N2 adsorption for larger pored MOFs. M-MOF-74 has previously been shown to be highly CO/N2 selective, yet lacks the high-pressure measurements suitable for a pressure swing adsorption application. Investigations adapting the structure involving direct exchange of the M2+ ion, alongside changes in the M2+ coordination and pore cavity, are made. Highly electronegative ligands improve both the low-pressure uptake of CO and the CO/N2 selectivity but at the cost of the working capacity beyond 1 bar. Furthermore, unusual hysteresis in the Cu2+ analogues are observed with evidence pointing towards a previously unobserved introduction of structural changes in the MOF via the Jahn-Teller effect. The results show MOF materials with a range of metrics including the highest current capacity and CO/N2 selectivity at both 1 and 20 bar. The work presented here shows that MOFs provide a promising alternative for CO/N2 separation application at both low and high pressures.

Light hydrocarbons are important platform chemicals in petrochemical industries. Adsorptive separation of ethylene/ethane (C2H4/C2H6) using solid porous adsorbents is an attractive alternative compared to the conventional energy intensive cryogenic distillation. The separation performance of a process is strongly influenced by the adsorption selectivity and the adsorbent capacity, which depend on the chemical and porous properties of adsorbents. Pillared-layer metal-organic frameworks (MOFs), having large adsorption capacity and controllable pore structure, are promising materials for gas adsorption and separation. In this PhD project, combined simulation and experimental methods were employed to study the adsorptive separation of ethylene/ethane mixtures in microporous materials. The work was carried out by (i) developing a new computational method (direct numerical integration method) to rapidly predict the C2H6/C2H4 selectivity in two-dimensional (2D) materials for designing and screening suitable adsorbents; (ii) studying the effect of pore size and shape on the adsorption selectivity using grand canonical Monte Carlo (GCMC) simulations; (iii) experimentally testing the properties of different pillared-layer MOFs upon adsorption of ethane and ethylene, understanding the framework variation of the pillared-layer MOF upon gas adsorption, and investigating the effects of metal ions and pillar linkers in the MOFs on their framework structure, moisture stability and adsorption performance. The relevant research findings from the project on the separation of ethylene/ethane using the adsorption technology provides the guidance for the design of porous adsorbents with desired properties and demonstrate the potential of using pillared-layer MOFs for separating gas mixtures.

This study has been undertaken in order to investigate the functionalisation of polyaromatic hydrocarbon cores (pyrene and perylene) and their interaction with graphitic surfaces, for potential application in the non-covalent modification of graphene for the generation of aqueous graphene-based dispersions and sensors. Graphene is a 2D-material that has been globally recognised for its potential to transform many technologies. Liquid-phase exfoliation of graphite is a promising strategy for ef- ficient mass-production of graphene. Water is an ideal solvent for industrial-scale pro- cessing, however the hydrophobic nature of graphene means a surfactant additive is re- quired. This study, in conjunction with that from other members of the group, has led to the synthesis of a series of pyrene and perylene structures where it has been established that insertion of alkyl spacers between a PAH core and a polar head group led to im- proved exfoliation efficiency. Graphene has excellent electrical properties and large surface area which could trans- form chemical sensors beyond the current limits of detection, however advances to en- sure selective responses toward target molecules are necessary. A series of monopodal and tripodal scaffolds, bearing one or three pyrene binding sites respectively and armed with a maleimide head group, were synthesised with a view to investigating their inter- action with representative thiols and sulfite anion. The non-covalent adsorption of these scaffolds onto a variety of surfaces was analysed by AFM and QCM, which suggested that the tripodal platform (3Py-Base, 29) has greater stability against desorption than its monopodal equivalent (1Py-Base, 28). A prototype nanofabricated graphene device showed an encouraging electronic response, which might be ascribed to the sensing re- action occurring on the surface of graphene.

The self-assembly of functional ordered structures from discrete building blocks is a central process in nanotechnology. The building blocks giving rise to organised nanometre- and micron-size materials span a wide range of technologically important substances, including amphiphilic molecules, nanocrystals and many other organic and inorganic molecules. While in the past few decades we have witnessed significant advances in synthesis and assembly technologies, achieving architecture designability remains an important challenge. This task requires a detailed insight into the relevant length- and time-scales at which thermal agitation and fluctuations on such particles occur. Statistical mechanics is the theoretical framework defining the equilibrium and out-of equilibrium properties of these many-body systems; computer simulations of particle-based models are the tools that make their investigation possible. This thesis is primarily devoted to the study of relevant self-assembling soft-matter systems by computer simulation. The first part is dedicated to the derivation of coarse-grained potentials describing effective interactions of Methacrylate-based block-copolymers, which have been recognised as excellent candidates for the assembly of nano-structured aggregates. The examination of the aggregation behaviour of low-molecular weight poly(ethylene oxide-b-butylmethacrylate) copolymers reveals a set of morphologies that can be controlled solely by the ratio of selective and common solvents. Morphological phase diagrams are presented and the effects of solvent correlations and chain conformation on the morphological transitions of self-assembled aggregates are investigated. This thesis also addresses the assembly the ionic surfactant Cetyl Trimethyl Ammonium Bromide and an OH-terminated propa(ethylene glycol) alkanethiol surfactant onto the surface of gold nanorods. The stabilised structures, including hemimicelles, cylindrical micelles and bilayers, show a strong dependence on the relative surfactant composition and the in-plane order of adsorbed headgroups. A systematic study of the phase-behaviour of rod-like nanocrystals coated with a soft repulsive corona demonstrates that the ubiquitous hexagonal close-packing observed in assembled superlattices of standing aligned colloidal rods is not the only accessible symmetry. Depending on the macroscopic conditions, other non-conventional phases such as square crystals can be assembled. This curious behaviour may lead to new ways for controlling the assembly of anisotropic nanoparticles into structures with pre-engineered catalytic and optical properties. Finally we study how the introduction of geometric constraints in confined glass-former glycerol induces molecular ordering close to symmetry breaking and the important implications on its dynamics.

The drive to reduce costs and maximise profits, as well as increased awareness of the environmental impacts of greenhouse gas emissions, has led the chemicals industry to seek to improve energy efficiency and source cheaper or more sustainable feedstocks. Traditionally, efforts to improve efficiency focused on improving or optimising existing technologies and processes, leading to highly heat-integrated and complex flowsheets. This approach, although leading to improvements in process performance, is inherently limited in its potential to bring about energy savings, as the core technology underpinning unit operations is the same. Novel approaches and technologies are required to truly revolutionise the performance of chemical processes. This work presents a systematic, multidisciplinary approach to explore the potential of adsorptive separation processes as alternatives to cryogenic distillation-based processes for the separation of challenging gas mixtures. The proposed approach is intended to be used at the early, conceptual stage of process development. As such, it focuses on assessing the technical capability of adsorbents and adsorption processes to achieve a desired separation, without explicit consideration of cost implications. Process energy demand and working capacity are used as indicators of potential cost. The project focuses on the separation of fluid mixtures where the constituents have similar volatilities. Separation by distillation of such mixtures is inherently difficult and energy intensive, as distillation relies on exploiting volatility differences to achieve separation. A simplified adsorption process model is proposed for rapid screening of adsorbents for the separation of binary gas mixtures in temperature swing adsorption (TSA) processes. The proposed model is validated by comparison with a rigorous adsorption column model and found to be in good agreement, with a maximum deviation of 14% observed in performance predictions over a range of operating conditions. The simplified model is also circa four orders of magnitude faster to compute than the rigorous model, making it ideal for large-scale adsorbent screening exercises. The model is applied to screen adsorbents for post-combustion CO2 capture, and identifies potential adsorbents which could meet industrial CO2 capture targets. This project is an industrial-academic collaboration and is sponsored and technically supported by BP through its International Centre for Advanced Materials (ICAM). As such, in developing and demonstrating the proposed approach, separation of CO from N2-containing gas mixtures - a challenging separation of particular interest to BP - is primarily considered as a case study. The impact of N2 contamination on the performance of the conventional cryogenic distillation process for the production of high purity (~99 mol%) CO from syngas is also investigated. Cryogenic distillation process flowsheets for CO production from syngas feeds containing up to 4 mol% N2 are developed and evaluated using a commercial process simulation software. Results show that N2-contamination to the degree where a CO/N2 separation unit becomes necessary has significant capital and operating cost implications for the conventional cryogenic distillation technology. This work also proposes a comprehensive multiscale methodology for integrated adsorbent and process selection. The proposed methodology combines molecular simulations, experimental adsorbent synthesis and characterisation, and shortcut and detailed process simulation and optimisation to identify the most suitable adsorbent(s) and process scheme for a given gas separation problem. The methodology is applied to investigate the potential to produce CO from blast furnace gas, a cheaper and more sustainable potential alternative to syngas. Blast furnace gas is the flue gas produced during the iron oxide reduction step of steel production. Due to its low heating value, blast furnace gas is not considered to be a viable fuel for process heating and is usually flared, contributing to greenhouse gas emissions. Despite its CO content (~21 mol%) and low cost, its high N2 content (~55 mol%) makes blast furnace gas an unattractive feedstock for conventional cryogenic distillation processes. 94 adsorbents from a family of metal organic frameworks (MOFs), a class of highly tuneable adsorbents, are considered in the study. The methodology successfully identifies 20 adsorbents which could potentially be used for high purity CO production from blast furnace gas in a TSA process. Three of the shortlisted adsorbents are further evaluated through preliminary cycle design and scheduling of multi-bed temperature swing adsorption processes for continuous production of CO from blast furnace gas. Each bed is considered to have a multi-tubular configuration, with the adsorbent packed within tubes and the heat transfer fluid in the shell side of the unit. All three adsorbents are shown to be able to meet CO product specifications of 99 mol% purity and 90% recovery, with continuous CO production achievable with just 5 beds and a cycle time of 40 minutes in one case. The comprehensive approach presented in this work is demonstrated to aid the development of novel adsorptive separation processes for challenging gas mixtures. Multiscale computational screening of candidate adsorbents and adsorption process options could significantly reduce the cost and time associated with the conceptual stage of process development. The approach augments computational isotherm generation with experimental validation for selected reference materials, further increasing confidence in the validity of subsequent results. The proposed approach identifies promising adsorbent(s) and process technology for a given separation based on technical feasibility. It should however be noted that, once technical feasibility has been established, practical considerations such as thermal and mechanical stability of the adsorbents, and the cost of manufacturing the adsorbents on an industrial scale, among others, should be ascertained prior to significant investment in a new technology. These additional considerations, although important, are beyond the scope of this work.

In the automotive industry, a kind of fuel additives, known as surfactant, is used to protect metallic surfaces. Its efficiency strongly depends on factors such as temperature, solvent properties and the presence of other surfactants in the system. In this thesis, both classical and ReaxFF molecular dynamics (MD) simulations are used in studying the impacts of these factors on the adsorption of organic surfactants at the fluid-solid interface. Firstly, a classical MD simulation study of competitive adsorption is carried out on a multi-functional phenol and amine surfactant model with ethanol at the oil/iron oxide interface. As the concentration of ethanol increases, the ethanol molecules effectively compete for the adsorption sites on the iron oxide surface. This observation concurs with the experimental findings of similar oil/iron oxide systems. Unlike most MD interfacial studies, ReaxFF MD uses a fully flexible and polarizable solid surface. The second part of the thesis includes a study on the effect of polarity of organic molecules on the structure of iron oxide using ReaxFF-based MD simulations. The simulation results suggest that care must be taken when parameterising empirical and transferable force fields because the fixed charges on a solid slab may not be a perfect representation of the real system, especially when the solid is in contact with polar compounds. Lastly, but not the least, missing ReaxFF interaction parameters for Fe/N have been developed to simulate the adsorption of amine based surfactant on iron oxide. The parameterisation of the force field is done by fitting these interaction parameters to a set of quantum mechanical data involving iron-based clusters. These newly developed parameters are able to capture chemisorption and proton transfer between hexadecylamine and iron oxide.

Adsorption using activated carbon has become an important separation process applied in industrial wastewater treatment. Presently, the need to reduce the cost of this process has driven the search for low cost adsorbents such as those obtained from agricultural by-products in effluent treatment especially in developing countries. In this study, seven agricultural residues were investigated as adsorbents for the removal of cadmium(II) and lead(II) ions from aqueous systems using a batch sorption. The residues were: oil palm fruit fibre (OPFS), cocoa pod (CCPS), coconut shell fibre (CNFS) plantain peel residue (PTHS) cocoyam peel (CCYBS), sweet potato peel (PTPS) and white yam peel (YTBS). These residues were further subjected to hydrothermal carbonisation at 200°C & 170°C, carbonisation at 400°C in limited air, pyrolysis at 700°C in N2 and chemical activation using K2CO3 and Na2CO3 in N2 to develop a number of carbon adsorbents that improve their sorption capabilities. Adsorbent characterisation studies included: functional group analysis; BET surface area; morphology, thermal degradation profile, zeta potential and chemical composition. The pHpzc was used to determine the most favourable pH for sorption and this was 6.5 for the residues and 7 for the prepared adsorbents. The results show that the BET surface area of the adsorbents did influence the rate of uptake of the two metal ions. The kinetics of sorption showed a two-stage profile for all adsorbents- initial uptake time was 180 minutes (residues) and 30-60 minutes for the other adsorbents. Sorption kinetics indicated that for Cd(II) ion sorption, optimum uptake was obtained using the CNFS; CNFS-HTC 200; CCPPCA and CNFKCA adsorbents, while for Pb(II) ion this was observed for the OPFS; CNFS-HTC; YTBPCA and CNFNCA adsorbents. Kinetic modelling indicated that the pseudo-first order (PFO) model described the sorption better than the pseudo second order (PSO) for both ions implying that the rate limiting step of sorption depends on concentration. Equilibrium isotherm modelling for metal ion sorption for the unmodified residues; Na2CO3 activated adsorbents and a commercial activated carbon (CGAC) was also studied from which the Langmuir isotherm parameter (qmax) to rank their adsorption capacities. The results obtained showed that the CCPNCA was the best adsorbent for Cd(II) ion removal with a qmax value of 29.4 mgg-1, while for Pb(II) ion, the CCYBNCA adsorbent was the best with an optimum qmax value of 41.9 mgg-1.These values were higher than those of the CGAC adsorbent used to benchmark this sorption study which were; 20.3 mgg-1 and 27.2 mgg-1 for Cd(II) and Pb(II) ions respectively. Finally, spent adsorbent ash stabilization using polymer encapsulation was successful carried out as leached samples after 60 days showed no leaching of the two ions.

In this work membranes containing 2D materials, namely graphene-like materials, and the most representative polymer of intrinsic microporosity (PIM), PIM-1, were developed for their use in bioalcohol recovery and CO2 gas separation. Graphene-like materials resulting from the alkyl-functionalization of graphene oxide (GO) using octylamine (OA) and octadecylamine (ODA), and their further chemical reduced forms were used as fillers for both applications. The incorporation of graphene-based fillers in freestanding membranes enhanced the separation performance for n-butanol (n-BtOH)/water separation and an average separation factor of 32.9 for n-BtOH/water was obtained with mixed matrix membranes (MMMs) containing 0.1 wt.% reduced alkyl-functionalized GO (OA functionalization), while pristine PIM-1 membranes presented an average separation factor of 13. In order to improve the productivity of the aforementioned membranes, thin film nanocomposite (TFN) membranes were fabricated via dip-coating. Herein, porous polyvinylidene fluoride (PVDF) membranes were used as support layers. The addition graphene-like materials with lateral sizes in the nanometer-range improved the separation performance, in comparison with pristine PIM-1 thin film composite (TFC) membranes. As expected, their fluxes were greater than that for freestanding membranes. Besides that, the incorporation of nanometer-sized fillers also enhanced the total flux of TFN membranes in approximately 40% when compared to PIM-1 TFC membranes. Finally, the addition of graphene-like materials into freestanding PIM-1 polymer matrices and their effect on the physical aging was studied. After 155 days, pristine PIM-1 membranes presented a CO2 permeability of (2.0 ± 0.7) × 10^3 Barrer, corresponding to a reduction in 68% from their initial value. The addition of graphene-based fillers proved to be an efficient way to retard the physical aging of PIM-1; after the same period of 155 days, MMMs containing 0.05 wt.% reduced OA-functionalized GO membranes showed a CO2 permeability of (3.5 ± 0.6) × 10^3 Barrer, i.e., a reduction of 39% relatively to day 0.

Hydrogen sulphide needs to be removed from natural gas for economic and environmental reasons. Adsorption is a commonly used operation to remove H2S, and the development of novel adsorbents with larger capacity and selectivity is an active area of research. This thesis focuses on adsorption and separation of hydrogen sulphide using metal organic frameworks (MOFs). MOFs are constructed from a metal cluster and an organic linker. The organic ligands can be tailored by changing their chemical nature, tuning their length, or modify by adding functional groups. The pore shape can be tuned by changing or mixing the metal ion. The ability to tailor the MOFs makes them interesting materials for industrial applications because their properties can be optimised, but it also creates an extraordinarily large number of possibilities that need to be tested to find the optimum material for a given separation. Molecular simulations are an attractive tool to study the properties of MOFs, as it allows to predict their performance based on intermolecular interactions, and provides insight into the molecular level structure of the system. In this work, two different families of MOF materials were studied: FPYEu and UiO. The first one has applications for sensors due to its low capacity while the second can have applications for gas separations. The validity of the force fields to describe the gas molecules and the solid frameworks were assessed, as well as the influence of using different approximations in the description of the solid framework. In general, it was found that force field applicability needs to be treated carefully, as in some cases large deviation with experimental results are obtained. Nevertheless, for a single family of materials, like UiO-66, UiO-67, UiO-68, it is possible to use the same force field parameters to describe correctly the adsorption in all of them. More importantly, it was also shown that using simplified descriptions of the functionalised material structure gives results within 10% of those obtained with the most accurate descriptions. Overall, it was found that functionalised UiO-67 with four carboxylic acid groups has the best compromise in terms of selectivity, adsorbent selection parameter and adsorption capacity for H2S separations. The enhancement in selectivity due to the functional groups is approximately 80%. The selection of an adsorbent requires a lot of additional information beyond the selectivity and capacity, which are the focus of this work, but having fast and accurate approaches to calculate adsorption selectivity and capacity can provide an initial screening of potentially interesting adsorbents for a given application.

This research focuses on improving direct methanol fuel cell (DMFC) performance by using graphene based materials in their membrane electrode assembly (MEA). The main obstacles of commercialization, poor electrode kinetics and the fuel crossover are addressed by using reduced graphene oxide (rGO) in the cathode microporous layer and single layer graphene (SLG) as an anode barrier layer. In the microporous layer work, an rGO (by hydroiodic acid (HI) reduction of graphene oxide) coated electrode exhibited higher conductivity than conventionally used Ketjen Black electrode (standard). The MEA containing rGO produced peak power density of 79 ± 3 mW cm-2 compared to the standard MEA performance of 55 ± 3 mW cm-2 (44 % improvement) at 70 °C, 1 M methanol fuel cell operating conditions. Doping rGO with boron (B-rGO) or nitrogen (N-rGO) by boric acid and nitric acid treatment and utilizing them as electrodes produced peak power density of 90 ± 3 mW cm-2 for B-rGO (63 % improvement) and 101 ± 3 mW cm-2 for N-rGO (84 % improvement) respectively. This is attributed to the higher conductivity of doped rGO electrodes than rGO, owing to the replacement of heteroatoms in their graphene lattice, with detected boron and nitrogen levels at 2 at% and 6 at%, evidenced by x-ray photoelectron spectroscopy (XPS), aiding in improved electron transfer. In the barrier layer work, SLG added onto the anode side of the MEA, reduced methanol permeation from 1.72 ± 0.1 x 10-7 mol cm-2 s-1 (for the standard) to 1.21 ± 0.1 x 10-7 mol cm-2 s-1, with negligible resistance to protons observed at 70 °C, leading to 45 % improvement in power density (77 ± 1 mW cm-2), caused by the dense carbon lattice packing and single layer nature of SLG. Preliminary results using hexagonal boron nitride (hBN), showed that the cell performance improved by 18 %. Overall, it is evident from the performance improvement results that these graphene materials (first ever reported to have used in the MEA of a DMFC) hold great promise for paving the way towards DMFC commercialization by increasing the electrode kinetics (in case of rGO usage) and reducing methanol permeation (in case of SLG usage).

One of the most promising routes to create advanced materials is self-assembly. Self-assembly refers to the self-organisation of building blocks to form ordered structures. As the properties of the self-assembled materials will inherit the properties of the basic building blocks, it is then possible to engineer the properties of the materials by tailoring the properties of the building blocks. In order to create mesoscale materials, the self-assembly of molecular building blocks of different sizes and interactions is important. Mesoscopic materials can be obtained by using larger building blocks such as nano and colloidal particles. Colloidal particles are particularly attractive as building blocks because it is possible to design interparticle interactions by controlling both the chemistry of the particles' surface and the properties of the solvent in which the particles are immersed. The self-assembly of spherical colloidal particles has been widely reported in the literature. However, advances in experimental techniques to produce particles with different shapes and sizes have opened new opportunities to create more complex structures that cannot be formed using spherical particles. Indeed, the particles' shape and effective interactions between them dictate the spatial arrangement and micro-structure of the system, which can be engineered to produce functional materials for a wide range of applications. The driving forces determining the self-assembly of colloidal particles can be modified by the use of external influences such as geometrical confinement and electromagnetic forces. Geometrical confinement, for example, has been used to design quasi two-dimensional materials such as multi-layered structures of spheres, dimers, rods, spherical caps, and monolayers of platelets with various geometries and symmetries. In this dissertation, we present three computer simulations studies using Monte Carlo and Molecular Dynamics simulations determining the self-assembly of monolayer colloidal platelets with different shapes confined in two dimensions. These particles have been selected due to recent experiments in colloidal particles with similar shapes. All the particles' models are represented by planar polygons, and three different effects affecting their self-assembly have been analysed: (a) the curvature of the particles' vertices; (b) the curvature of the particles' edges; and finally (c) the addition of functional groups on the particles' surface. These studies aim to demonstrate that the subtle changes on the particle's shape can be used to engineer complex patterns for the fabrication of advanced materials. Monte Carlo simulations are performed to study the self-assembly of colloidal platelets with rounded corners with 4, 5, and 6-fold symmetries. Square platelets provide a rich phase behaviour that ranges between disorder-order and order-order phase transitions. Suprisingly, the disk-like shape of pentagons and hexagons prevents the total crystallisation of these systems, even at a high pressure state. A hysteresis gap is observed by the analysis of compression and expansion runs for the case of square platelets and the thermodynamic method known as direct coexistence method is used to be accurately determined the point of the order-order transition. Further, unexpected results are obtained by performing Molecular Dynamics simulations in systems with platelets with 3, 4, 5, and 6-fold symmetries when all the sides of each polygon are curved. Macroscopic chiral symmetry breaking is observed for platelets with 4 and 6-fold symmetries, and for the first time a rule is promoted to explain when these chiral structures can be formed driven only by packing effects. This unique rule is verified also for platelets with the same curved sides as previously when functional chains tethered to either vertices or sides. Indeed, square platelets with curved sides confined in two dimensions can form chiral structures at medium densities when flexible chains tethered to either vertices or sides. Triangular platelets with curved sides can form chiral structures only when the chains are tethered to the corners, since the chains experience an one-hand rotation to sterically protect one side. When the chains are symmetrically tethered to the sides, local chiral symmetry breaking is observed as both left-hand and right-hand sides on each vertex are sterically protected allowing the same probability for rotation either in clockwise or anticlockwise direction.

Self-assembly of colloidal particles into ordered structures is hailed as the preferred route to production of functional devices on the nanometre and micron length scales. The shape of a colloidal particle is one of the most influential factors determining the type of ordered structure that is assembled. Thus this thesis is devoted to understanding the role of particle shape on phase behaviour of colloidal systems. The effect of particle shape is isolated by using computer simulations to model particles as hard, anisotropic bodies which interact via purely repulsive interactions. Two particle models are studied which are representative of real colloids: non-convex wireframe polyhedra, and convex spherical caps. This thesis investigates the densest packings of several wireframe polyhedra. By comparing packings of six distinct polyhedra some general conclusions are drawn regarding the effects of rounded polyhedra edges, and a new shape descriptor is given which can suggest whether a wireframe polyhedron is likely to form new interpenetrating crystal structures. Wireframe cubes were studied in more detail, where the full phase behaviour was mapped out. A curious phenomenon was found whereby crystals formed by cubic wireframes exhibit plastic fluctuations. This unusual behaviour, if reproduced experimentally, may lead to useful optical properties. A systematic study of spherical caps demonstrates the effect of shape on collective behaviour as the particle model interpolates between a sphere and a thin platelet. Purely repulsive interactions are responsible for a range of different crystal structures, but the nucleation of these structures is challenging due to slow dynamics. Furthermore, there are often many ways for a spherical cap to pack in a given volume, which leads to multiple metastable states. The self-assembly of spherical caps was directed by sedimentation on a solid template which resulted in increased nucleation rates and more stable crystals. However, there is still a lack of control over the exact crystal structure due to the degeneracy in ways to pack.

Computer simulation techniques for exploring the microscopic world are quickly gaining popularity as a tool to complement theoretical and experimental approaches. Molecular dynamics (MD) simulations allow the motion of an N–body soft matter system to be solved using a classical mechanics description. The scope of these simulations are however limited by the available computational power, requiring the development of multiscale methods to make better use of available resources. Dual scale models are a novel form of molecular model which simultaneously feature particles at two levels of resolution. This allows a combination of atomistic and coarse-grained (CG) force fields to be used to describe the interactions between particles. By using this approach, targeted details in a molecule can be described at high resolution while other areas are treated with fewer degrees of freedom. This approach aims to allow for simulating the key features of a system at a reduced computational cost. In this thesis, two generations of a methodology for constructing dual scale models are presented and applied to various materials including polyamide, polyethene, polystyrene and octanol. Alongside a variety of well known atomistic force fields, these models all use iterative Boltzmann inversion (IBI) force fields to describe the CG interactions. In addition the algorithms and data structures for implementing dual scale MD are detailed, and expanded to include a multiple time step (MTS) scheme for optimising its peformance. Overall the IBI and atomistic force fields were compatible with each other and able to correctly reproduce the expected structural results. The first generation methodology featured bonds directly between atoms and beads, however these did not produce the correct structures. The second generation used only atomistic resolution bonds and this improved the intramolecular structures greatly for a relatively minor cost. In both the polyamide and octanol systems studied, the models were also able to properly describe the hydrogen bonding. For the CG half of the force field, it was possible to either use preexisting force field parameters or develop new parameters in situ. The resulting dynamical behaviour of the models was unpredictable and remains an open question both for CG and dual scale models. The theoretical performance of these models is faster than the atomistic counterpart because of the reduced number of pairwise interactions that must be calculated and this scaling was seen with the proposed reference implementation. The MTS scheme was successful in improving the performance with no effects on the quality of results. In summary this work has shown that dual scale models are able to correctly reproduce the structural behaviour of atomistic models at a reduced computational cost. With further steps towards making these models more accessible, they will become an exciting new option for many types of simulation.

There were three main driving forces behind this thesis: global concern over climate change mainly due to uncontrolled carbon dioxide (CO2) emissions, the excitement over the discovery of graphene and its versatile potential, and the potential to design three-dimensional (3D) or two-dimensional (2D) structures, in our case using unique triptycene molecule. We examined two polymeric materials for CO2 adsorption and suggested simple design of disordered carbons suitable for gas adsorption studies. The approach in each task was to examine structural and adsorption properties of materials using detailed atomistic modelling employing Monte Carlo and Molecular Dynamics techniques and where possible provide experimental measurements to validate the simulations. The thesis is presented as a collection of papers and the work can be divided into three independent projects. The aim of the first project is to utilize graphene as an additive in polymer composites in order to increase separation between the polymer chains increasing available surface area. The matrix used is a polymer of intrinsic microporosity (PIM-1), which possess large surface area and narrow nano-sized ( > 2nm) pore distribution attractive for gas separation membrane applications. Adding a filler can reduce aging of the polymer, and enhance permeability across the membrane, often to the expense of loosing selectivity. Therefore, we investigated the packing of PIM-1 chains in presence of discrete 2D graphene platelets and 3D graphene-derived structures and its effect on composite structure and adsorption properties. We found that additives do not alter structural polymer properties at the molecular level preserving the same adsorption capacity and affinity. Potential permeability increase would benefit from the retention of selectivity in the material. Building on design philosophy of materials with intrinsic microporosity we continued further investigation of 3D graphene-derived structures. The idea is that highly concave molecules or polymer chains pack inefficiently creating microporous materials with sufficient surface area for gas adsorption. 3D propeller-like structures were derived from graphene arms connected through the rigid triptycene and other types of cores. The resulting structures created a large amount of micropores and showed similar CO2/CH4 selectivity to activated carbons reported in the literature. It was shown that rigid triptycene core leads to more open structures. The model was also applied to model commercially available activated carbon to predict n- perfluorohexane adsorption. The fitting to experimental structural information proved to be challenging due to trial and error nature of the approach. Nevertheless, the simple packing procedure and diverse structure design have a great potential to serve as a virtual model for porous carbons that possess pore complexity and does not require any previous experimental data to be build on. The last project concerns CO2 adsorption and selectivity over CH4 and N2 in recently reported triptycene-based polymer. The triptycene shape polymer can form a porous 2D network that can be exfoliated into free-standing sheets and potentially used as a membrane. Sheets stack in the bulk material forming anisotropic channel pores. Additionally it contains fluoro- functional groups, which are known to have a high CO2 affinity. We explored pore structure and chemistry of stacked material for gas adsorption and predicted comparable capacity and CO2 selectivity to other microporous covalent materials such as activated carbons and PIMs. The CH4/N2 selectivity was similar to currently most selective material belonging to MOF family. We showed that fluoro-group have a positive effect on CO2 affinity, however predictions are sensitive to the charges of fluorine atoms assigned by different methods.

Understanding the physics of water evaporation from saline porous media is important in many processes such as soil salinity, terrestrial ecosystem functioning, vegetation and crop production, biological activities in vadose zone, and CO2 sequestration. Precipitation of salt is one of the possible outcomes of the evaporation process from saline porous media which may either enhance or interrupt the desired process depending on the localization and pattern of the precipitated salt. In the present study X-ray micro tomography was used to study the 3D dynamics and patterns of salt deposition in drying porous media under different boundary conditions and the effects of salt concentration, particle size distribution and shape of grains on the precipitation patterns and dynamics at pore-scale have been investigated. Evaporation process from porous media involves preferential invasion of large pores on the surface while the fine pores remain saturated serving as the evaporation sites to supply the evaporative demand. This results in increasing salt concentration in fine pores during evaporation. Precipitation starts when salt concentration exceeds the solubility limit in the preferential evaporation sites. At the early stages, the precipitation rate increases with time until all evaporation sites at the surface reach the solubility limit and turn into the precipitation sites. This is followed by a constant rate of precipitation proportional to the evaporation rate. We show that the formation of salt crust at the surface does not immediately interrupt the evaporation process due to the porous nature of the precipitated salt investigated using the scanning electron microscopy. Also, our results confirmed the formation of discrete efflorescence at the surface of porous media due to the presence of pores with different sizes. Distribution of these fine pores on the surface directly influences the patterns of salt precipitation and thickness of the salt crust such that in the media with more fine pores, precipitated salt forms a thinner crust as the solute transferred to the surface is distributed among more evaporation sites. In contrast, in the media with fewer evaporation sites at the surface the salt crust will be more discrete but thicker. A simple equation is also proposed to estimate the evolution if the thickness of the salt crust on the surface of porous media. Our results provide new insights regarding the physics of salt precipitation and its complex dynamics in porous media during evaporation.

This Thesis investigates computationally the behaviour of two novel microporous materials,organic molecules of intrinsic microporosity (OMIMs) and polymers of intrinsic microporosity(PIMs). OMIMs and PIMs are organic amorphous materials, which achieve microporosityby packing inefficiently. The design of amorphous materials is challenging because their self-assembly process is not known. Predictive molecular simulations can help in recognising thefeatures that affect the properties of these materials, and guiding in the design of new structures with desired performances. OMIMs are highly concave shaped molecules, consisting of a core and a series of termini, which provide the geometry and the general chemical environment of these structures, respectively. PIMs are polymers consisting of fundamental units such as stiff segments and contortionsites, which form either linear or network like porous structures. While chronologically olderthan OMIMs, they share with them a common design philosophy. This Thesis is presented in alternative format, and the results, consisting of five journal articles,can be divided into three main parts. The first part focuses on recognising a reliable method to generate representative models ofOMIMs. Different computational protocols and molecular mechanics descriptions were investigated; the development of the utilised simulation protocol was based on comparison of several simulation methods and force fields to experimental wide angle X-ray scattering (WAXS) patterns. Our work suggests that OMIMs can be described successfully by both PCFF and UFF; the final packed material can be generated using a 21-step compression-decompression molecular dynamics protocol, previously developed to generate virtual model of PIMs. The examination of the simulated structures has provided a deeper understanding of the features that affect the packing behaviour of this class of materials, suggesting that OMIMs have a greater microporosity when the molecules are the most shape-persistent, which required rigid structures and bulky end groups. The adsorption behaviour described by different generic force fields (Dreiding, OPLS and UFF) was also investigated to guide on the selection of the solid-fluid interactions when modelling OMIMs, for future comparison with experimental data. Our results suggest that very strong interactions between argon adsorbate and OMIM-based framework are described by UFF, while the weakest adsorbent is obtained using OPLS force field. The second part of the research focuses on assessing the effect that different termini’s chemistry and bulkiness have over the packing behaviour, adsorption properties and solubility of the OMIMs. The microporous frameworks generated by two selected families of cruciform OMIMs (benzene and naphthalene- based) were investigated with respect to their packing behaviour, porosity and adsorption properties. Our analysis suggests that the final density of the material, as well as the surface area and pore volume, depend on the ending group’s bulkiness. Bulkier molecules lead to materials with lower densities, but it was found that the adsorption behaviour is not just related to the material’s density, but also to the pore size and shape, which are determined by the way the molecules pack. The relationship between adsorption capacity and physical properties was analysed and the role of surface area, free volume and enthalpic interaction was used to identify different adsorption regimes. It was found that the uptake of argon at low pressure is proportional to the strength of the adsorbent-adsorbate interaction while at moderate pressure it is dependent on the free volume and surface area. The dissolution of three cruciform OMIMs was investigated in dichloromethane, ethyl acetateand toluene. Direct interface molecular dynamics simulations showed that the solubility process consists of two steps; the diffusion of the solvent in the OMIM-rich phase, and the departure of the OMIMs in the solvent bulk. We proposed a simple model to represent this mechanism. Furthermore, results from infinite dilution simulations show that the solvent-OMIMs interactions can be related to the chemistry of the OMIMs and to the solvent’s properties. We found that, in general, increasing the length of the OMIM’s arm affects negatively the solubility of the material, while adding bulky alkyl groups favours the interaction with the solvent molecules. The third part concentrates on the characterisation of PIMs and their application as CO2 adsorbent. Properties of four polymers of intrinsic microporosity containing Tröger’s base units were assessed for CO2 capture experimentally and computationally. Structural properties included average pore size, pore size distribution, surface area, and accessible pore volume, whereas thermodynamic properties focused on density, CO2 sorption isotherms, and enthalpies of adsorption. It was found that the shape of the contortion site plays a more important role than the polymer density when assessing the capacity of the material, and that the presence of a Tröger base unit only slightly affects the amount adsorbed at low pressures, but it does not have any significant influence on the enthalpy of adsorption fingerprint. A comparison of the materials studied with those reported in the literature allowed us to propose a set of guidelines for the design of polymers for CO2 capture applications.

Adverse changes in the Earth's climate are thought to be due to the output of carbon dioxide from power stations. This has led to the development of many new materials to remove CO2 from these gas streams. Polymers of intrinsic microporosity (PIMs) are a novel class of polymers that are rigid with sites of contortion. These properties result in inefficient packing and so lead to large pore volumes and high surface areas. The inclusion of Tröger’s base, a contortion site made up of two nitrogen atoms, is thought to lead to increased uptake of CO2. The combination of electrostatic interactions with strong van der Waals forces should interact favourable with the quadrupole moment of CO2.Here a molecular simulation study of a selection of these polymers is presented. The study begins by developing a quick screening method on single polymer chains. This shows that the high surface area and adsorption affinity are a result of the contorted nature of PIMs along with the inclusion of groups such as Tröger’s base.The creation of atomistic models that reproduce the space packing ability of these polymers is also explored. Methods developed for PIMs in literature are investigated along with a new method developed during this study. GCMC simulations are then used to investigate the adsorption of CO2. In this study it is seen that that these polymers possess a well percolated network of both ultramicropores and supermicropores with a significant fraction of these pores being close to the kinetic diameter of CO 2. It is posited that these pores may be the result of the inclusion of Tröger’s base. It is also shown that this produces a particularly favourable site for adsorption. The phenomenon of swelling as a result of CO2 adsorption is also investigated using a variety of methods that make use of the output from the GCMC simulations. It was found that swelling is negligible for pressures of up to 1 bar. This result is important as swelling in the polymer can lead to a reduction in selectivity and an increase in permeability, which can affect the overall material’s performance.

Ethylene-vinyl acetate co-polymers are widely used as cold-flow improving additives in diesel fuels. Although their functionality is undisputed, the mechanisms of action at a molecular level are not fully understood. Theories that EVA acts as both a nucleating agent for small wax crystals and as a crystal growth inhibitor are generally acknowledged, however the understanding of the effect of structure on additive performance is limited. Studies have been carried out using molecular simulation techniques with the aims of improving the understanding of the interactions between EVA and diesel fuels, and assessing the potential of these methods for the analysis of different additive structures and fuel compositions. Firstly, the ability of Monte Carlo simulations to predict the chemical potentials of n-alkanes in organic solvents was studied. This information would be of use in determining the characteristics of different fuel compositions. It was found that the particle insertion method used becomes more efficient as the aspect ratio of the solvent increases relative to that of the solute. Despite the identification of expected linear trends in the chemical potential of n-alkanes, it was not possible to produce high quality quantitative data using this method. The effect of vinyl acetate spacing and solvent environment on the configuration of lone EVA molecules in the liquid phase was studied. Molecular dynamics showed that closely spaced vinyl acetate groups increase the tendency of the molecule to fold at that point, whilst molecules with 2 or 3 ethylene groups in between show resistance to folding. It was shown that n-hexane as a solvent produced more folded configurations than benzene and n-hexadecane respectively. Monte Carlo simulations were also performed but were largely unsuccessful. Finally, molecular dynamics simulations were performed to study the effect of different EVA structures on the spontaneous crystallisation of n-hexadecane, and the interaction of the EVA with the resulting structures at a molecular level. It was shown that different EVAs had varying effects on the crystallisation, with trends attributed to the spacing of the vinyl acetate groups and the length and position of extended aliphatic sections of the EVA molecules. One molecule, with evenly spaced side-groups and no extended aliphatic sections was shown to fully prevent the formation of any crystalline structure within the time of the simulation where all other EVA molecules allowed some degree of wax formation to occur.

Consumer- and pharmaceutical-based products are a major component of the chemical industry. In the personal care industry, formulations often consist of a mixture of surfactants and fatty alcohols. The addition of surfactants aids the stability of the formulation. The formulated product microstructure depends upon the preparation conditions as well as the ingredients. Controlling which microstructures form during the production of a formulated product is important as different microstructures can have wildly different physical properties, making some far more favourable than others. This thesis examines several of the processes undertaken in the manufacture of formulated products. The dissolution of a surfactant in a bulk water phase is examined. This is examined in a number of ways; firstly, the dissolution times of the surfactants are measured using electrical resistance tomography. It is found that the dissolution time varies with the agitation rate, agitator size, and addition method. The dissolution is also examined using dissipative particle dynamics to gain insight into the dissolution on a molecular scale. It is found that the surfactant breaks into wormlike micelles on dissolution. If an oil is added to the initial bulk then the dissolution process is modified so that long cylinders are produced with some spherical micelles. Finally, the break-up rate is predicted using a breakage model based on the agitator shear rate and a network-of-zones model. This produces good results. The production and post-shear processing of a sample formulated product, hair conditioner, is examined. Firstly, the mixing in a vessel is examined with electrical resistance tomography. Problems are encountered when the production method involves the use of distilled water as the conductivity is very low; however, the mixing time of the final product in the vessel can be determined. It is also shown that the majority of the structural changes in the post-shearing process are caused by the in-line rotor-stator mixer. The viscosity of the product increases in a linear fashion with the shear rate, while the conductivity increases as a function of the shear rate and the recycle rate. This allows the monitoring of the post-shearing process to be carried out using electrical resistance tomography. This thesis also looks at the possibility of producing a multiple frequency electrical resistance tomography device to monitor formulated product production; however, it has been shown that the conductivity does not vary with the voltage frequency over a usable range. This meant that no further effort was put into developing this, as it gave no advantage over the traditional single frequency technique. Nevertheless, important advances towards better understanding of mixing processes resulted due to the investigations carried out.

The present thesis proposes to explore the potential of Zeolitic Imidazolate Framework ZIFs for CO2 capture applications in the conditions required by the Pressure Swing Adsorption separations process. Molecular modelling methods, combining Monte Carlo, Density Functional Theory and ab-initio simulations, were employed to mimic pure and mixture gas adsorption in ZIF materials. A transferable Force Field specifically developed for ZIFs materials is used to characterize a large variety of frameworks. Theses studies enable us to better understand the phenomena acting during adsorption process. Thereby several innovative modifications are proposed to enhance the ZIFs properties for CO2 capture and a series of hypothetical ZIFs are designed, characterized and compared to existing materials. The results cumulated during this thesis were then summarized to propose a first correlative model able to predict ZIF properties from a set of solids descriptors. This study enables to guide the structure design to optimize the ZIF properties.