Marc Malfois

Here we provide microscopic insight into the improved mechanical performance of biomass derived films of poly(lactic acid) (PLA) following melt blending with medium-density polyethylene (MDPE) and high-density polyethylene (HDPE). Laboratory based characterisations show that twin screw extrusion of the blend in the melt introduced elongated micron-scale phase-separated structures consisting of phase-separated semicrystalline PE with some degree of crystallographic orientation along the machine direction, and isotropic poorly ordered PLA. Characteristic regions of failure during uniaxial tensile deformation of films were identified using optical microscopy. The regions associated with failure. which appear as crazes and domains oriented orthogonally to the extension direction, are micron-scale in pure PLA but expand to millimetre-scale in the blended materials.. Polarised vibrational (infrared and Raman) microspectroscopy reveals specific molecular orientation of the PLA and PE chains in the failure regions. Spatially localised X-ray scattering provided information on electron density correlations from crystalline- (wide angle X-ray scattering, WAXS) and meso-scale domains (small angle X-ray scattering, SAXS) as well as orientational information on these domains. It was found from WAXS that the polymer chains in the brittle PLA films are not more ordered on the length-scale of chain packing following extension, but that ordered and oriented nm-scale domains are produced (fibrils). The phaseseparated PE structures are shown to play a role in the distribution of load in the blend during extension, inhibiting the formation of PLA fibrils. The synchrotron-based measurements reveal the differences in polymer organisation both in and away from the failure regions: the regions associated with failure show well-defined perturbations, whereas away from the failure the material does not display any resolvable perturbation from the bulk unstretched structure. These results indicate that the improved mechanical performance arises from a local redistribution of stresses in the brittle PLA by the PE phase in the craze region.

Here we provide microscopic insight into the improved mechanical performance of biomass derived films of poly(lactic acid) (PLA) following melt blending with medium-density polyethylene (MDPE) and high-density polyethylene (HDPE). Laboratory based characterisations show that twin screw extrusion of the blend in the melt introduced elongated micron-scale phase-separated structures consisting of phase-separated semicrystalline PE with some degree of crystallographic orientation along the machine direction, and isotropic poorly ordered PLA. Characteristic regions of failure during uniaxial tensile deformation of films were identified using optical microscopy. The regions associated with failure. which appear as crazes and domains oriented orthogonally to the extension direction, are micron-scale in pure PLA but expand to millimetre-scale in the blended materials.. Polarised vibrational (infrared and Raman) microspectroscopy reveals specific molecular orientation of the PLA and PE chains in the failure regions. Spatially localised X-ray scattering provided information on electron density correlations from crystalline- (wide angle X-ray scattering, WAXS) and meso-scale domains (small angle X-ray scattering, SAXS) as well as orientational information on these domains. It was found from WAXS that the polymer chains in the brittle PLA films are not more ordered on the length-scale of chain packing following extension, but that ordered and oriented nm-scale domains are produced (fibrils). The phaseseparated PE structures are shown to play a role in the distribution of load in the blend during extension, inhibiting the formation of PLA fibrils. The synchrotron-based measurements reveal the differences in polymer organisation both in and away from the failure regions: the regions associated with failure show well-defined perturbations, whereas away from the failure the material does not display any resolvable perturbation from the bulk unstretched structure. These results indicate that the improved mechanical performance arises from a local redistribution of stresses in the brittle PLA by the PE phase in the craze region.

The lipids located in the outermost layer of the skin, the stratum corneum (SC), play a crucial role in maintaining the skin barrier function. The primary components of the SC lipid matrix are ceramides (CERs), cholesterol (CHOL), and free fatty acids (FFAs). They form two crystalline lamellar phases: the long periodicity phase (LPP) and the short periodicity phase (SPP). In inflammatory skin conditions like atopic dermatitis and psoriasis, there are changes in the SC CER composition, such as an increased concentration of a sphingosine-based CER (CER NS) and a reduced concentration of a phytosphingosine-based CER (CER NP). In the present study, a lipid model was created exclusively forming the SPP, to examine whether alterations in the CER NS:CER NP molar ratio would affect the lipid organization. Experimental data were combined with molecular dynamics simulations of lipid models containing CER NS:CER NP at ratios of 1:2 (mimicking a healthy SC ratio) and 2:1 (observed in inflammatory skin diseases), mixed with CHOL and lignoceric acid as the FFA. The experimental findings show that the acyl chains of CER NS and CER NP and the FFA are in close proximity within the SPP unit cell, indicating that CER NS and CER NP adopt a linear conformation, similarly as observed for the LPP. Both the experiments and simulations indicate that the lamellar organization is the same for the two CER NS:CER NP ratios while the SPP NS:NP 1:2 model had a slightly denser hydrogen bonding network than the SPP NS:NP 2:1 model. The simulations show that this might be attributed to intermolecular hydrogen bonding with the additional hydroxide group on the headgroup of CER NP compared with CER NS.

We recently introduced the possibility of performing operando small-angle X-ray scattering measurements using a novel industrially relevant injection moulding system for plastics. We show that useful time-resolving measurements can be performed with a time-cycle of 1 s and highlight the possible steps to reduce this to 0.5 s. We show how we can use the transmission measurements to provide a time marker when plastic first enters the mould cavity in the region probed by the incident X-ray beam. We show the opportunities provided by this experimental stage mounted on the NCD-SWEET beamline at ALBA to probe the reproducibility of the injection moulding system on different scales. The design of the equipment allowed for the development of the structure and the morphology to be evaluated in different parts of mould cavity, and we evaluated any differences in a rectangular mould cavity. We identified future prospects for this equipment in terms of novel mould heating and cooling systems and the opportunities for quantitatively evaluating radical approaches to injection moulding technology.

We have recently introduced the possibility of performing operando small-angle X-ray scattering measurements using a novel industrially relevant injection moulding system for plastics. We show that useful time-resolving measurements can be performed with a time-cycle of 1s and we highlight the possible steps to reduce this to 0.5s. We show how we can use the transmission measurements to provide a time-marker when plastic first enters the mould cavity in the region probed by the incident X-ray beam. We show the opportunities provided by this experimental stage mounted on the NCD-SWEET beamline at ALBA to probe the reproducibility of the injection moulding system on different scales. The design of the equipment allows the development of the structure and the morphology to be evaluated in different parts of mould cavity and we evaluate any differences in a rectangular mould cavity. We identify future prospects for this equipment in terms of novel mould heating and cooling systems and the opportunities for quantitatively evaluating radical approaches to injection moulding technology.

The signaling molecule auxin coordinates many growth and development processes in plants, mainly through modulating gene expression. Transcriptional response is mediated by the family of auxin response factors (ARF). Monomers of this family recognize a DNA motif and can homodimerize through their DNA-binding domain (DBD), enabling cooperative binding to an inverted binding site. Most ARFs further contain a C-terminal PB1 domain that is capable of homotypic interactions and mediating interactions with Aux/IAA repressors. Given the dual role of the PB1 domain, and the ability of both DBD and PB1 domain to mediate dimerization, a key question is how these domains contribute to DNA-binding specificity and affinity. So far, ARF–ARF and ARF–DNA interactions have mostly been approached using qualitative methods that do not provide a quantitative and dynamic view on the binding equilibria. Here, we utilize a DNA binding assay based on single-molecule Förster resonance energy transfer (smFRET) to study the affinity and kinetics of the interaction of several Arabidopsis thaliana ARFs with an IR7 auxin-responsive element (AuxRE). We show that both DBD and PB1 domains of AtARF2 contribute toward DNA binding, and we identify ARF dimer stability as a key parameter in defining binding affinity and kinetics across AtARFs. Lastly, we derived an analytical solution for a four-state cyclic model that explains both the kinetics and the affinity of the interaction between AtARF2 and IR7. Our work demonstrates that the affinity of ARFs toward composite DNA response elements is defined by dimerization equilibrium, identifying this as a key element in ARF-mediated transcriptional activity.

This study reports on the synthesis of novel bienzyme polymer-assisted nanoflower complexes (PANF), their morphological and structural characterization, and their effectiveness as cascade biocatalysts. First, highly porous polyamide 6 microparticles (PA6 MP) are synthesized by activated anionic polymerization in solution. Second, the PA6 MP are used as carriers for hybrid bienzyme assemblies comprising glucose oxidase (GOx) and horseradish peroxidase (HRP). Thus, four PANF complexes with different co-localization and compartmentalization of the two enzymes are prepared. In samples NF GH/PA and NF GH@PA, both enzymes are localized within the same hybrid flowerlike organic-inorganic nanostructures (NF), the difference being in the way the PA6 MP are assembled with NF. In samples NF G/PAiH and NF G@PAiH, only GOx is located in the NF, while HRP is preliminary immobilized on PA6 MP. The morphology and the structure of the four PANF complexes have been studied by microscopy, spectroscopy, and synchrotron X-ray techniques. The catalytic activity of the four PANF was assessed by a two-step cascade reaction of glucose oxidation. The PANF complexes are up to 2–3 times more active than the free GOx/HRP dyad. They also display enhanced kinetic parameters, superior thermal stability in the 40–60 °C range, optimum performance at pH 4–6, and excellent storage stability. All PANF complexes are active for up to 6 consecutive operational cycles.