Polyethylene/Bacterial-Cellulose Biocomposite Synthesized via In Situ Polymerization with Zirconocene/MMAO Catalyst

In this study, the polyethylene filled celluloses regarded as biocomposites was produced via in situ polymerization with zirconocene/MMAO catalyst. Three types of celluloses including microcrystalline cellulose (MCC), bacterial cellulose prepared from pineapple shell extract (BCP), and bacterial cellulose prepared from coconut (BCC) were used as fillers and also catalytic support in the polymerization system. It was found that the presence of cellulose fillers slightly decreased catalytic activity of the polymerization system, but it was still higher compared with that of other natural fillers such as coir dust. This is caused by the lower impurity of cellulose. The MCC provided the highest catalytic activity among all cellulose fillers. The obtained biocomposites were characterized with different techniques including scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). It was observed that all obtained biocomposites exhibited good morphology compared with the neat polyethylene. Thermal stability of the polymers was improved with the cellulose fillers

Chemically specifi C multiscale modeling of clay-polymer nanocomposites reveals intercalation dynamics, tactoid self-assembly and emergent materials properties

A quantitative description is presented of the dynamical process of polymer intercalation into clay tactoids and the ensuing aggregation of polymerentangled tactoids into larger structures, obtaining various characteristics of these nanocomposites, including clay-layer spacings, out-of-plane clay-sheet bending energies, X-ray diffractograms, and materials properties. This model of clay-polymer interactions is based on a three-level approach, which uses quantum mechanical and atomistic descriptions to derive a coarse-grained yet chemically specifi c representation that can resolve processes on hitherto inaccessible length and time scales. The approach is applied to study collections of clay mineral tactoids interacting with two synthetic polymers, poly(ethylene glycol) and poly(vinyl alcohol). The controlled behavior of layered materials in a polymer matrix is centrally important for many engineering and manufacturing applications. This approach opens up a route to computing the properties of complex soft materials based on knowledge of their chemical composition, molecular structure, and processing conditions.This work was funded in part by the EU FP7 MAPPER project (grant number RI-261507) and the Qatar National Research Fund (grant number 09–260–1–048). Supercomputing time was provided by PRACE on JUGENE (project PRA044), the Hartree Centre (Daresbury Laboratory) on BlueJoule and BlueWonder via the CGCLAY project, and on HECToR and ARCHER, the UK national supercomputing facility at the University of Edinburgh, via EPSRC through grants EP/F00521/1, EP/E045111/1, EP/I017763/1 and the UK Consortium on Mesoscopic Engineering Sciences (EP/L00030X/1). The authors are grateful to Professor Julian Evans for stimulating discussions during the course of this project. Data-storage and management services were provided by EUDAT (grant number 283304)

Heat stress in grapevine: the pros and cons of acclimation

Heatstressisamajorlimitingfactorofgrapevineproduction and quality.Acclimation and recovery are essential to ensure plant survival, and the recovery mechanisms can be independent of the heat response mechanisms.An experimental set up with and without acclimation to heat followed by recovery [stepwise acclimation and recovery (SAR) and stepwise recovery (SR), respectively] was applied to two grapevine varieties,Touriga Nacional (TN),and Trincadeira (TR), with different tolerance to abiotic stress. Major differences were found between leaves of SAR and SR,especially after recovery; in SAR, almost all parameters returned to basal levels while in SR they remained altered. Acclimation led to a swifter and short-term antioxidative response, affecting the plant to a lesser extent than SR. Significant differences were found among varieties: upon stress, TN significantly increased ascorbate and glutathione reduction levels, boosting the cell’s redox-buffering capacity, while TR needed to synthesize both metabolites, its response being insufficient to keep the redox state at working levels.TR was affected by stress for a longer period and the up-regulation pattern of antioxidative stress genes was more obvious. In TN, heat shock proteins were significantly induced, but the canonical heat-stress gene signature was not evident probably because no shutdown of the housekeeping metabolism was needed

Food Legumes and Rising Temperatures: Effects, Adaptive Functional Mechanisms Specific to Reproductive Growth Stage and Strategies to Improve Heat Tolerance

Ambient temperatures are predicted to rise in the future owing to several reasons associated with global climate changes. These temperature increases can result in heat stress- a severe threat to crop production in most countries. Legumes are well-known for their impact on agricultural sustainability as well as their nutritional and health benefits. Heat stress imposes challenges for legume crops and has deleterious effects on the morphology, physiology, and reproductive growth of plants. High-temperature stress at the time of the reproductive stage is becoming a severe limitation for production of grain legumes as their cultivation expands to warmer environments and temperature variability increases due to climate change. The reproductive period is vital in the life cycle of all plants and is susceptible to high-temperature stress as various metabolic processes are adversely impacted during this phase, which reduces crop yield. Food legumes exposed to high-temperature stress during reproduction show flower abortion, pollen and ovule infertility, impaired fertilization, and reduced seed filling, leading to smaller seeds and poor yields. Through various breeding techniques, heat tolerance in major legumes can be enhanced to improve performance in the field. Omics approaches unravel different mechanisms underlying thermotolerance, which is imperative to understand the processes of molecular responses toward high-temperature stress

Enhanced Exfoliation of Organoclay in Partially End-Functionalized Non-Polar Polymer

We found that enhanced exfoliation of clay up to 20 wt.-% in non-polar polybutadiene (PB) if the PB was blended with a relatively small fraction of hydroxyl-terminated PB (HTPB). The choice of an intermediate polymer composition to enhance exfoliation was motivated by theoretical predictions of end-functionalizing effects of Balazs, Farmer, and coworkers. A combination of X-ray diffraction and rheological measurements were used to optimize HTPB content for enhanced exfoliation. We also observed the competition of the kinetic and thermodynamic processes during the ripening of the exfoliated clay structure