Functional poly(2-oxazoline)s by direct amidation of methyl ester side chains

Poly(2-alkyl/aryl-2-oxazoline)s (PAOx) are biocompatible pseudopolypeptides that have received significant interest for biomedical applications in recent years. The growing popularity of PAOx in recent years is driven by its much higher chemical versatility compared with the gold standard in this field, poly(ethylene glycol) (PEG), while having similar beneficial properties, such as stealth behavior and biocompatibility. We further expand the PAOx chemical toolbox by demonstrating a novel straightforward and highly versatile postpolymerization modification platform for the introduction of side-chain functionalities. PAOx having side chain methyl ester functionalities is demonstrated to undergo facile uncatalyzed amidation reactions with a wide range of amines, yielding the corresponding PAOx with side-chain secondary amide groups containing short aliphatic linkers as well as a range of side-chain functionalities including acid, amine, alcohol, hydrazide, and propargyl groups. The PAOx with side-chain methyl ester groups can be prepared by either partial hydrolysis of a PAOx followed by the introduction of the methyl ester via modification of the secondary amine groups with methyl succinyl chloride or by the direct copolymerization of a nonfunctional 2-oxazoline monomer with a 2-methoxycarbonylethyl-2-oxazoline. Thus, this novel synthetic platform enables direct access to a wide range of side-chain functionalities from the same methyl-ester-functionalized poly(2-oxazoline) scaffold

Thermoresponsive poly(2-oxazoline)s, polypeptoids, and polypeptides

This review covers the recent advances in the emerging field of thermoresponsive polyamides or polymeric amides, i.e., poly(2-oxazoline)s, polypeptoids, and polypeptides, with a specific focus on structure-thermoresponsive property relationships, self-assembly, and applications

Organic produce and production system conformity assessments : eggs and isotope analysis

Eggs were analysed for stable isotope composition, as a measure for organic produce authentication

Self-healing metallo-supramolecular hydrogel based on specific Ni2+ coordination interactions of poly(ethylene glycol) with bistriazole pyridine ligands in the main chain

In this study, a supramolecular hydrogel formed by incorporating the 2,6-bis(1,2,3-triazol-4-yl)-pyridine (btp) ligand in the backbone of a polymer prepared by copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) "click" polyaddition reaction of 2,6-diethynylpyridine and diazido-poly(ethylene glycol) is reported. The hydrogelation is selectively triggered by the addition of Ni2+ ions to aqueous copolymer solutions. The gelation and rheological properties could be tuned by the change of metal to ligand ratio and polymer concentration. Interestingly, the hydrogel exhibits a fast (within 2 min) and excellent repeatable autonomic healing capacity without external stimuli. This self-healing behavior may find potential applications for the repairing of metal coatings, in the future

Bio-inspired hydrogels as multi-task anti-icing hydrogel coatings

In a recent report in Matter, Zhu, Wang, He and co-workers report a straightforward and effective strategy for the design of icephobic hydrogel coatings on the basis of polydimethylsiloxane (PDMS)-grafted polyelectrolyte hydrogels. These passive anti-icing and de-icing coatings were demonstrated to synergistically suppress ice nucleation, ice propagation, and ice adhesion

Research study of pressure instrumentation

To obtain a more vibration resistant pressure sensor for use on the Space Shuttle Main Engine, a proximity probe based, diaphragm type pressure sensor breadboard was developed. A fiber optic proximity probe was selected as the sensor. In combination with existing electronics, a thermal stability evaluation of the entire probe system was made. Based upon the results, a breadboard design of the pressure sensor and electronics was made and fabricated. A brief series of functional experiments was made with the breadboard to calibrate, thermally compensate, and linearize its response. In these experiments, the performance obtained in the temperature range of -320 F (liquid N2) to +200 F was comparable to that of the strain gage based sensor presently in use on the engine. In tests at NASA-Marshall Space Flight Center (MSFC), after some time at or near liquid nitrogen temperatures, the sensor output varied over the entire output range. These large spurious signals were attributed to condensation of air in the sensing gap. In the next phase of development of this sensor, an evaluation of fabrication techniques toward greater thermal and mechanical stability of the fiber probe assembly must be made. In addition to this, a positive optics to metal seal must be developed to withstand the pressure that would result from a diaphragm failure

Structural diversification of pillar[n]arene macrocycles

Despite the fact that pillar[n]arenes receive major interest as building blocks for supramolecular chemistry and advanced materials, their functionalization is generally limited to the modification of the hydroxy or alkoxy units present on the rims. This limited structural freedom restricts further developments and has very recently been overcome. In this article, we highlight three very recent studies demonstrating further structural diversification of pillar[n]arenes by partial removal of the alkoxy substituents on the rims, which can be considered as the next generation of pillar[n]arenes

Impact of climate change using CRAFT: a case study for West Africa

The CGIAR research program on Climate Change, Agriculture and Food Security Program’s (CCAFS) Regional Agricultural Forecasting Toolbox (CRAFT) is a framework for multi-scale spatial gridded simulations using an ensemble of crop models. The toolbox facilitates studies on the potential impact of climate change on crop production for a region in addition to other capabilities such as the regional in-season yield forecasting and risk assessment. CRAFT can be used to generate and conduct multiple simulation scenarios, maps, and interactive visualizations using a crop engine that can run the crop simulation models DSSAT, APSIM, and SARRA-H, in concert with the Climate Predictability Tool (CPT) for probabilistic seasonal climate forecasts

Effect of Water Price on the Multicrop Production Decision: Appling Fixed Allocatable Input Model in Georgia

This study applies the fixed allocatable input model to test the effect of water price on the multiple production decision in Georgia, U.S. The limited dependent variable models are applied and intensive data are analyzed in this study to estimate the decision for crop choice, land allocation, product supply, and water demand functions at crop-level. In order to investigate the effect of water price on crop-level demand, the total water price effect on farm water demand is decomposed the intensive margin and extensive margin.Resource /Energy Economics and Policy,