The surge of interest in and scientific publications on the structure and properties of nanocomposites has made it rather difficult for the novice to comprehend the physical structure of these new materials and the relationship between their properties and those of the conventional range of composite materials. Some of the questions that arise are: How should the reinforcement volume fraction be calculated? How can the clay gallery contents be assessed? How can the ratio of intercalate to exfoliate be found? Does polymerization occur in the clay galleries? How is the crystallinity of semi-crystalline polymers affected by intercalation? What role do the mobilities of adsorbed molecules and clay platelets have? How much information can conventional X-ray diffraction offer? What is the thermodynamic driving force for intercalation and exfoliation? What is the elastic modulus of clay platelets? The growth of computer simulation techniques applied to clay materials has been rapid, with insight gained into the structure, dynamics and reactivity of polymer-clay systems. However these techniques operate on the basis of approximations, which may not be clear to the non-specialist. This critical review attempts to assess these issues from the viewpoint of traditional composites thereby embedding these new materials in a wider context to which conventional composite theory can be applied. (210 references).

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Biomedical applications of graphene have recently attracted intensive attention, with graphene-based nanomaterials being reported as promising candidates in, for example, drug delivery, biosensing and bioimaging. In this paper, mechanical properties and bioactivity of nanofibrous and porous membranes electrospun from graphene oxide (GO) nanoplatelets reinforced poly(ε-caprolactone) (PCL) were investigated. The results showed that the presence of 0.3 wt% GO increased the tensile strength, modulus and energy at break of the PCL membrane by 95%, 66% and 416%, respectively, while improving its bioactivity during biomineralization and maintaining the high porosity of over 94%. The mechanical enhancements were ascribed to the change in the fiber morphology and the reinforcing effect of GO on PCL nanofibers, whereas the improvements on the bioactivity stemmed from the anionic functional groups present on the GO surface that nucleated the formation of biominerals. Systematic studies on the PCL/GO nanocomposite films with varying GO concentrations revealed that the reinforcing effect of GO on PCL was due to the strong interfacial interactions between the two phases characterized by Fourier transform infrared spectroscopy, the good dispersion of GO in the matrix and the intrinsic properties of GO nanoplatelets. The strong and bioactive PCL/GO nanofibrous membranes with a high porosity have great potential for biomedical applications.

Bioactive gelatin-graphene oxide (GO) nanocomposites with varying GO contents were fabricated by a solution-casting method. With the addition of 1 wt% GO, the tensile strength, Young's modulus and energy at break of gelatin were found to increase by 84%, 65% and 158%, respectively. Such reinforcement effects were investigated in detail in terms of the size and morphology of GO sheets, the dispersion degree of GO sheets in gelatin matrix and the interactions between the two phases. The Young's moduli of the nanocomposites were well predicted by the Mori-Tanaka model with application of the effective volume fraction of reinforcement that takes into account the nanofiller and a fraction of the macromolecules adsorbed onto its surface. The GO nanosheets also improved the bioactivity of gelatin by inducing more calcium phosphate nanocrystals on the composites. GO acts as both an effective reinforcement filler and a biological activator in hydrophilic biopolymers such as gelatin, offering the biopolymer-GO nanocomposites great potential to be further developed in biomedical fields.

The modulus-volume fraction relationship for a poly( -caprolactone)-montmorillonite nanocomposite follows composite materials theory provided the clay volume fraction is correctly calculated. Thus, for interpretation of mechanical properties, nanocomposites do not have to be treated as a separate class of material. The tensile modulus of biodegradable poly( -caprolactone) was increased by 50% at 8 wt % clay addition (as corrected for surfactant), but the more dramatic improvement was in tensile elongation at break which increased from 165% to 550% for additions of up to 10 wt % clay. Poly( -caprolactone) nanocomposites with various clay volume fractions were produced with two organo-modified montmorillonites. Untreated montmorillonite was used as an experimental control to compare the properties with a conventional composite over the same clay volume fraction range, The composites were confirmed and characterized by XRD, DSC, NMR, and TEM.

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Article:Frydrych, M., Roman, S., MacNeil, S. et al. (1 more author) (2015) Biomimetic poly(glycerol sebacate)/poly(L-lactic acid) blend scaffolds for adipose tissue engineering. Acta Biomaterialia, 18. 40 -49. ISSN 1742-7061 https://doi.org/10.1016/j.actbio.2015.03.004Article available under the terms of the CC-BY-NC-ND licence (https://creativecommons.org/licenses/by-nc-nd/4.0/) eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request.

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