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To establish, and isolate, the influence of different chemical functional groups on the aggregation of polyaromatic hydrocarbons, a series of triphenylene-based compounds were investigated using a combined experimental and computational approach. Containing alkoxy side chains of varying lengths or amide appendages, both with and without a terminating carboxylic acid, their aggregation structures, sizes, and kinetics in toluene were studied over several length scales, using a combination of dynamic light scattering and diffusion-ordered nuclear magnetic resonance spectroscopy, complemented with molecular dynamics simulations. There is a strong correlation between molecular architecture and aggregation mechanisms: the addition of polar functional groups and heteroatoms resulted in compounds that are more prone to aggregation and form large, micrometer-sized clusters, while the increased steric hindrance imposed by alkoxy side chains led to stable nanometer-sized aggregates. These conclusions underline the strong structure-function relationship of polyaromatic hydrocarbons, such as asphaltenes, examined here over multiple length scales in a single solvent. We also demonstrate the importance of using complementary techniques to study the aggregation process of polyaromatic hydrocarbons that could form aggregates of various sizes over different time scales.

Using a combination of experimental and computational approaches, the interaction between anastellin, a recombinant fragment of fibronectin, and representative biomaterial surfaces has been examined. Anastellin and superfibronectin, have been seen to exhibit anti-angiogenic properties and other properties that may make it suitable for consideration for incorporation into biomaterials. The molecular interaction was directly quantified by atomic force microscope (AFM) based force spectroscopy, complemented by adsorption measurements using quartz crystal microbalance (QCM). By AFM, it was found that the anastellin molecule facilitates a stronger adhesion on polyurethane films (72.0 pN nm-1 ) than on poly (methyl methacrylate) films (68.6 pN nm-1 ). However, this is not consistent with the QCM adsorption measurements which shows no significant difference. Molecular dynamics simulations of the behaviour of anastellin on polyurethane in aqueous solution were performed to rationalise the experimental data, and show that anastellin is capable of rapid adsorption to PU while its secondary structure is stable upon adsorption in water. The authors would like to acknowledge the UK Engineering & Physical Sciences Research Council (EPSRC) and the University of Strathclyde for the studentship to David Mallinson, and the Bridging the gap (BTG) project at the University of Strathclyde for funding this work. Computational facilities were provided by the Archie-West HPC facility (EPSRC grant no. EP/K000586/1), and SFI/HEA Irish Centre for High-End Computing (ICHEC) and access to AFM and contact angle measurements was provided by the EPSRC Centre in Continuous Manufacturing and Crystallisation (CMAC). peer-reviewed 2017-10-24

Natural asphaltenes are defined as polyaromatic compounds whose chemical composition and structure is dependent on its geological origin and production history, hence are regarded as complex molecules with aromatic cores and aliphatic tails that occur in the heaviest fraction of crude oil. The aggregation of asphaltenes presents a range of technical challenges to the production and processing of oil. In this work we study the behaviour of the model asphaltene-like molecule hexa-tert-butylhexa-peri-hexabenzocoronene (HTBHBC) using molecular dynamics simulation. It was found that the regular arrangement of the tert-butyl side chains prevents the formation of strongly-bound dimers by severely restricting the configurational space of the aggregation pathway. In contrast, a modified molecule with only 3 side chains is readily able to form dimers. This work therefore confirms the influence of the molecular structure of polyaromatic compounds on their aggregation mechanism, and reveals the unexpected design rules required for model systems that can mimic the behavior of asphaltenes.