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Abstract: By electrospinning poly(ethylene oxide) (PEO)-blended sodium dodecyl sulfate (SDS) functionalized carbon nanotube (CNT) solutions, we engineered single- and double-walled nanotubes into highly aligned arrays. CNT alignment was measured using electron microscopy and polarised Raman spectroscopy. Mechanical tensile testing demonstrates that a CNT loading of 3.9 wt% increases the ultimate tensile strength and ductility of our composites by over a factor of 3, and the Young's modulus by over a factor of 4, to ∼260 MPa. Transmission electron microscopy (TEM) reveals how the aligned nanotubes provide a solid structure, preventing polymer chains from slipping, as well as polymer crystallisation structures such as ‘shish-kebabs’ forming, which are responsible for the improved mechanical properties of the composite. Differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) reveals micellar and hexagonal columnar structures along the axis of the fibers, some of which are associated with the presence of the CNT, where these hexagonal structures are associated with the SDS functionalization on the CNT surfaces. This work demonstrates the benefits of CNT alignment within composites, revealing the effectiveness of the electrospinning technique, which enables significantly improved functionality, increasing the utility of the composites for use in many different technological areas.

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Abstract: To date, only several microporous, and even fewer nanoporous, glasses have been produced, always via post synthesis acid treatment of phase separated dense materials, e.g. Vycor glass. In contrast, high internal surface areas are readily achieved in crystalline materials, such as metal-organic frameworks (MOFs). It has recently been discovered that a new family of melt quenched glasses can be produced from MOFs, though they have thus far lacked the accessible and intrinsic porosity of their crystalline precursors. Here, we report the first glasses that are permanently and reversibly porous toward incoming gases, without post-synthetic treatment. We characterize the structure of these glasses using a range of experimental techniques, and demonstrate pores in the range of 4 – 8 Å. The discovery of MOF glasses with permanent accessible porosity reveals a new category of porous glass materials that are elevated beyond conventional inorganic and organic porous glasses by their diversity and tunability.

Open Access

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Abstract: Stress oscillation has been observed in a number of linear thermoplastic polymers during the cold-drawing process, where the polymers exhibit periodic self-excited oscillatory neck propagation. However, the origin of the mechanical stress oscillation process and its relationship with the crystalline morphology of the polymer are still under debate. In this work, we revisit the stress oscillation behavior by studying a semi-crystalline polyester, poly(butylene succinate) (PBS), a biodegradable polymer suitable for biomedical and packaging applications. Stress oscillation of PBS is observed when deformed at a range of elongation rates from 10 to 200 mm min−1, and the fluctuation magnitude decays as the deformation temperature increases from 23 to 100 °C. Periodic transparent/opaque bands form during necking of PBS, which consists of alternating regions of highly oriented crystalline zones and microcavities due to crazing and voiding, although the degree of crystallinity did not change significantly in the bands. Simultaneous small- and wide-angle X-ray scattering confirms that the alternating stress increases, as shown in the stress–strain curves, correspond to the appearance of the transparent bands in the sample, and the abrupt drop of the stress is the result of voiding during the neck propagation. The voiding and cavitation are ultimately responsible for the stress oscillation process in PBS. The in-depth analysis of this work is important in understanding and controlling the occurrence of instabilities/cavitation during polymer processing such as film blowing, biaxial stretching and injection moulding of biodegradable polymer materials.

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Abstract: Lyotropic non-lamellar liquid crystalline (LLC) nanoparticles are attractive nanocarriers for drug delivery, particularly for the solubilization of poorly water-soluble drugs. Due to the reported problems of complement activation and cytotoxicity of most investigated Pluronic F127-stabilized cubosomes and hexosomes, there is an interest in introducing safe stabilizers for these LLC nanodispersions. Citrem appears to be the stabilizer of choice for the colloidal stabilization of these LLC nano-self-assemblies owing to its hemocompatiblity and poor activation of the complement system. This anionic food-grade emulsifier in combination with soy phosphatidylcholine (SPC) can be used to introduce a library of hemocompatible lamellar and non-lamellar liquid crystalline nanodispersions at different lipid compositions. We found that batch-to-batch variability in citrem composition is associated with slight alterations in the size, structural characteristics, and surface charge of the produced citrem/SPC nanoparticles. Further, we report on the temperature-triggered alterations in these nano-self-assemblies at different lipid compositions by using synchrotron small angle X-ray scattering (SAXS). The addition of citrem at different temperatures induces lamellar to non-lamellar structural transitions as evident from the appearance of inverse bicontinuous cubic Pn3m and discontinuous hexagonal (H2) phases, respectively, upon increasing citrem concentration and varying temperature in the range of 5–59 °C. Citrem/SPC nanoparticles are attractive for use in the development of nanocarriers for drug delivery owing to their structural tunability and hemocompatiblity.

Open Access

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Abstract: Solvent-induced physical hydrogels of TEMPO-oxidized cellulose nanofibrils (OCNFs) were obtained from aqueous/alcoholic dispersions of fibrils in lower alcohols, namely, methanol, ethanol, 1-propanol and 2-propanol. The sol-gel transition occurs above a critical alcohol concentration of ca. 30 wt% for all alcohols tested. The rheological properties of the hydrogels depend on the nature of the alcohol: for ethanol, 1-propanol and 2-propanol the magnitude of the shear storage modulus follows the alcohol hydrophilicity, whilst methanol produce the weakest gels in the group. Above a second critical concentration, ca. 60 wt% alcohol, phase separation is observed as the gels undergo syneresis. Analysis of small-angle X-ray scattering data show that the OCNFs may be modelled as rigid rods. In the presence of lower alcohols, attractive interactions between nanofibrils are present and, above the alcohol concentration leading to gelation, an increase of OCNF cross-section is observed, suggesting alcohol induced aggregation of nanofibrils.