Decomposition by microorganisms of plastics in soils is almost unexplored despite the fact that the majority of plastics released into the environment end up in soils. Here, we investigate the decomposition process and microbiome of one of the most promising biobased and biodegradable plastics, poly­(butylene succinate-co-adipate) (PBSA), under field soil conditions under both ambient and future predicted climates (for the time between 2070 and 2100). We show that the gravimetric and molar mass of PBSA is already largely reduced (28–33%) after 328 days under both climates. We provide novel information on the PBSA microbiome encompassing the three domains of life: Archaea, Bacteria, and Eukarya (fungi). We show that PBSA begins to decompose after the increase in relative abundances of aquatic fungi (Tetracladium spp.) and nitrogen-fixing bacteria. The PBSA microbiome is distinct from that of surrounding soils, suggesting that PBSA serves as a new ecological habitat. We conclude that the microbial decomposition process of PBSA in soil is more complex than previously thought by involving interkingdom relationships, especially between bacteria and fungi.

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The phase behavior of binary mixtures of non-crystallizable racemic poly (D, L-lactic acid) (PDLLA) and the mosquito-repellent/drug N,N-diethyl-3-methylbenzamide (DEET) was analyzed with respect to the effect of the polymer molar mass on the liquid-liquid (L-L) phase separation characteristics, by cloud-point measurements and differential scanning calorimetry. The PDLLA/DEET system shows a subambient upper critical solution temperature (UCST), with the critical temperature decreasing and critical polymer concentration increasing with decreasing molar mass of PDLLA. The obtained L-L phase separation curves were used to estimate the temperature-dependence of the interaction parameter, confirming that the enhanced miscibility of the system components in case of low molar mass PDLLA is due to increased entropy of mixing.

BACKGROUND The effectiveness of mosquito repellents, whether applied topically on the skin or released from a wearable device, is determined by the evaporation rate. This is because a repellent has to be present in the form of a vapour in the vicinity of the exposed skin that needs protection. Therefore, gravimetric techniques were used to investigate the direct evaporation of selected liquid repellents, their permeation through polymer films, and their release from a microporous polyethylene matrix. RESULTS Evaporation of a repellent into quiescent air is determined by its air permeability. This is a product of the vapour pressure and the diffusion coefficient, i.e. SA=PAitalicsatDA. It was found that repellents could be ranked in terms of decreasing volatility as: ethyl anthranilate > citriodiol > dimethyl phthalate > N,N‐diethyl‐meta‐toluamide (DEET) > decanoic acid > ethyl butylacetylaminopropionate > Icaridin. Experimental SA values, at 50 °C, ranged from 0.015 ± 0.008 mPa m2 s−1 for the least volatile repellent (Icaridin) to 0.838 ± 0.077 mPa m2 s−1 for the most volatile (ethyl anthranilate). The release rate from microporous polyethylene strands, produced by extrusion‐compounding into ice water baths followed a similar ranking. These strands featured an integral skin‐like membrane that covered the extruded strands and controlled the release of the repellent at a low effective rate. CONCLUSION The high thermal and thermo‐oxidative stability together with the low volatility of the mosquito repellents ethyl butylacetylaminopropionate and Icaridin make them attractive candidates for long‐lasting wearable mosquito‐repellent devices. Such anklets/bracelets may have utility for outdoor protection against infective mosquito bites in malaria‐endemic regions. © 2019 Society of Chemical Industry

Poly(l‐lactic acid) (PLLA) can be used as a carrier for the mosquito repellent N,N‐diethyl‐3‐methylbenzamide (DEET). PLLA dissolves in DEET at elevated temperature and crystallizes on cooling to below the concentration‐dependent equilibrium melting temperature, leading to scaffold formation. In this work, non‐isothermal and isothermal crystallization experiments were performed, using differential scanning calorimetry and polarized‐light optical microscopy. Crystallization of PLLA in solution with DEET is faster than melt‐crystallization of neat PLLA, with the maximum crystallization rate decreasing with decreasing PLLA content in the investigated range from 5 to 50 m% PLLA. The decrease of the maximum crystallization rate with increasing solvent content is due to decreases in both the maximum crystal growth rate and the nuclei density. The observed downward shift of the temperature range of crystallization is caused by the depression of equilibrium melting temperature and a strong decrease of the glass transition temperature, both occurring with increasing solvent concentration. It is assumed that the strong decrease of the glass transition temperature due to the presence of DEET, and the related increase of the mobility of PLLA chains, is the main reason for the increased crystallization rate compared to melt‐crystallization of PLLA. It is demonstrated that a large variety of spherulitic superstructures can be obtained by variation of the crystallization conditions, presumably leading to largely different 3D scaffold structures and DEET‐delivery characteristics.