An ultrastretchable iono-elastomer with resistance sensitive to both elongation strain and temperature has been developed by hierarchical self-assembly of an end functionalized triblock copolymer in a protic ionic liquid (ethylammonium nitrate) followed by cross-linking. Small-angle X-ray scattering experiments in situ with uniaxial elongation reveal a nanoscale microstructural transition of the hierarchically self-assembled cross-linked micelles that is responsible for the material's remarkable mechanical and ionic conductivity responses. The results show that the intermicelle distance extends along the deformation direction while the micelles organize into a long-range ordered face-centered-cubic structure during the uniaxial elongation. Besides good cyclability and resistance to selected physical damage, the iono-elastomer simultaneously achieves an unprecedented combination of high stretchability (340%), highly linear resistance vs elongation strain ( R = 0.998), and large temperature gauge factor (Δ R/ R = 3.24%/°C@30 °C). Human subject testing demonstrates that the iono-elastomer-based wearable thermomechanical sensor is able to effectively and accurately register both body motion and skin temperature simultaneously.

Roles of naturally occurring low-molecular-weight organic acids (LMWOAs) on the dissolution of hydroxyapatite nanoparticles (HANPs) were explored. Our results indicate that phosphate release during HANPs dissolution is highly dependent on the type of LMWOA, which has important implications when HANPs are used as a promising phosphorus (P) nanofertilizer in agricultural soils particularly at the rhizosphere. Furthermore, stable oxygen isotope technique was employed for the first time to accurately trace O-isotopic fractionation and evolution of phosphate during HANPs dissolution in abiotic systems. Given that the HANPs pool has distinct phosphate oxygen isotope signatures compared to soil P pools, the isotope technique could be used to identify whether plant uptake of P comes from HANPs or from soils, and thus to evaluate use efficiency of HANPs by plants in agricultural soils. ABSTRACT 25Hydroxyapatite nanoparticles (HANPs) have recently been advocated as a highly-efficient and 26 environmentally-benign 'green' phosphorus (P) nanofertilizer in modern agriculture. However, 27 knowledge on how low-molecular-weight organic acids (LMWOAs) secreted by plants in 28 agricultural soils mediate the dissolution of HANPs and release of dissolved phosphate is 29 nonexistent. Here, three most commonly occurring LMWOAs (acetic, oxalic, and citric acids) 30were evaluated for their roles on HANPs dissolution in both batch and column systems. 31Particularly, O-isotopic ratios of dissolved phosphate during HANPs dissolution were measured 32 to disentangle mechanisms controlling isotope fractionation. Our results reveal that in batch 33 system HANPs dissolution was very fast but the overall dissolution efficiency was low (≤30%), 34 unlike in column system where ~100% dissolution was achieved. The low dissolution efficiency 35 of HANPs in batch system was due predominately to rapid consumption of proton; whereas in 36 column system the HANPs were progressively dissolved by low pH LMWOAs and reaction 37 products were eluted out. Regardless of LMWOA type and experimental system, the 38 isotopically-lighter phosphate (P 16 O 4 ) was preferentially released during initial phases of 39 dissolution and dissolved phosphate became gradually P 18 O 4 -enriched with time. This 40 fractionation was less in batch (−0.3‰ to +1.1‰) than in column (−1.3‰ to +1.1‰) systems 41 due primarily to lower dissolution efficiency and higher P 16 O 4 and P 18 O 4 exchange between 42 HANPs and dissolved phosphates. The Rayleigh model well described O-isotopic fractionation 43 of dissolved phosphate under different LMWOAs. Overall, our findings provide important 44 insights into the dissolution kinetics and O-isotopic evolution of phosphate-based NPs that are 45 relevant to plant-soil systems particularly at the rhizosphere. 46 47

The micellization of dilute solutions of Pluronic block copolymers P123 (EO 20 −PO 70 −EO 20 ) and F127 (EO 106 −PO 70 −EO 106 ) and comicellization of binary mixtures in partially deuterated ethylammonium nitrate (d 3 EAN, a protic ionic liquid) are studied by small-angle neutron scattering. The average Pluronics composition in micelles shows a linear dependence on the bulk Pluronic composition. The mole ratio between P123 molecules in the micelles to those existing as unimers in solvent increases with temperature and P123 concentration. At a fixed F127/P123 ratio, the micelle core radius, the micelle corona thickness, and the aggregation number decrease with increasing temperature, while the total micelle volume fraction increases. At a fixed temperature, increasing P123 content in the binary mixtures leads to a weak minimum in micelle core size and aggregation number and a weak maximum in micelle corona thickness and total volume fraction of micelles. The comicellization behavior in d 3 EAN resembles that in aqueous solutions reported experimentally and theoretically. To our knowledge, this is the first experimental report on comicellization behavior of Pluronic triblock copolymers in a protic ionic liquid.

No abstract