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This work reports a simple and scalable strategy to prepare a series of thermoresponsive polyurethanes synthesized via copolymerization of dicyclohexyl diisocyanate with glycerol ethoxylate in a single one‐pot system. These polyurethanes exhibit lower critical solution temperatures (LCST) at 57 °C. The LCST of synthesized polyurethane was determined from Dynamic Scanning Calorimetry and UV‐vis measurements. Both the LCST and Tg of synthesized polyurethane was tuned by varying the ratio between hard segment (dicyclohexyl diisocyanate) and soft segment (glycerol ethoxylate). Thus, Tg values could be tuned from −54.6 °C to −19.9 °C for samples with different flexibility. The swelling and deswelling studies were done at room temperature and above the LCST respectively. The results showed that the swelling ratio increases with the increase of soft segment (glycerol ethoxylate) in synthesized polyurethanes. Furthermore, the mechanical properties of the membrane were studied by universal tensile testing measurements. Specifically, stress at break values varied from 0.35±0.07 MPa to 0.91±0.15 MPa for the tested membranes, whereas elongation at break data ranged from 101.9±20.9 % to 192.4±24.4 %, and Young's modulus varied from 0.35±0.03 MPa to 1.85±0.19 MPa. Tensile strength of the films increased with the increase of the hard segment and elongation at break decreased. [ABSTRACT FROM AUTHOR]

An analysis of standard thermodynamic functions of protein structure in solution allows revealing important features of protein solution phase behavior, particularly the presence of higher and lower critical solution temperatures on phase diagram (PD). Linking the phase and the corresponding conformational transitions of protein molecules to phase transitions of the protein solution as a whole will provide consideration of the relationship between protein conformation and the structural organization of protein systems in predenaturational interval. A phase diagram (PD) for the globular protein solution is presented in the temperature-entropy coordinate plane. Solution phase states have been analyzed and a probable interrelation of topological structures arising in the supercritical region with the phase processes in low- and high-temperature range has been defined when considering PD. This shows the possibility to superpose two types of PD: for normal and retrograde protein solubility. PD in the temperature-packing density plane has been presented for a protein solution with low and high critical solution temperatures and a supercritical zone between them typical of native protein solution, and a closed zone typical of denatured protein solution in the near physiological temperature interval. Supramolecular organization of protein solution has been described on this basis including metastable phases of protein molecules in conformations altered with respect to native (N) and denatured (D) states as well as dynamical protein clusters and oligomers in the supercritical zone. The contribution of the solvent in the low- and high-temperature ranges has also been taken into account. Various PD regions have been interpreted under the assumption that molecules in conformations, corresponding to N and D states are capable of forming different nanocrystal lattices which define the topological features of the corresponding solutions in a wide temperature range. Probable significance of supercritical phase states of protein solutions for the self-regulation of the components chemical potentials at the expense of the solution supramolecular organization at changing temperature and/or salt concentration and thereby at changing environmental factors has been discussed.

Phase transitions of protein solutions which are of interest for biotechnological and biomedical purposes should be analyzed from the point of view of their interrelation with phase transitions of the structure of protein molecules on the basis of the state thermodynamic functions. This is suggested by the coupling of intra- and intermolecular interactions in protein systems. Temperature trends of the standard thermodynamic functions of native (N) and denatured (D) protein in solution have been considered within the framework of the concept of excessive melting functions that determine the thermodynamic affinity of protein molecules for solvent. Thermodynamic solution functions of protein in native (N) and denatured (D) states have been built on the basis of microcalorimetry data. The nature of enthalpy, entropy and free energy temperature changes has been shown to suggest a theoretical possibility of both higher and lower critical solution temperatures. Previously there were only experimental indications for some proteins under certain conditions (solvent composition, pH etc.), but thermodynamical interpretation was lacking. Furthermore, there appears a supercritical zone between higher and lower critical solution temperatures on the phase diagram. The zone is of open (two-phase) or closed (one-phase) type depending on the protein conformation – D or N, respectively. This applies to the range next to physiological temperatures and makes the description of supramolecular organization of protein solution possible under such conditions. Significance of the supercritical zone of protein phase states is determined by its probable contribution into self-regulation of the system in response to the changes in environmental conditions (temperature, salinity, acidity etc.).

Several new types of temperature-responsive ion exchange resins of different polymer composition have been prepared by grafting the products from the co-polymerisation of N- phenylacrylamide, N -iso-propylacrylamide and acrylic acid derivatives onto cross-linked agarose. Analysis of the binding isotherms for these different resins obtained under batch adsorption conditions indicated that the resin based on N -iso-propylacrylamide containing 5% (w/w) N- phenylacrylamide and 5% (w/w) acrylic acid resulted in the highest adsorption capacity, B max , for the whey protein, bovine lactoferrin, e.g. 14 mg bovine lactoferrin/mL resin at 4 °C and 62 mg bovine lactoferrin/mL resin at 40 °C, respectively. Under dynamic loading conditions at 40 °C, 94% of the loaded bovine lactoferrin on a normalised mg protein per mL resin basis was adsorbed by this new temperature-responsive ion-exchanger, and 76% was eluted by a single cycle temperature shift to 4 °C without varying the composition of the 10 mM sodium dihydrogen phosphate buffer, pH 6.5, or the flow rate. The binding characteristics of these different ion exchange resins with bovine lactoferrin were also compared to results obtained using other resins based on N -isopropylacrylamide but contained N - tert -butylacrylamide rather than N -phenylacrylamide, where the corresponding dynamic capture and release properties for bovine lactoferrin required different temperature conditions of 20 °C and 50 °C, respectively for optimal desorption/adsorption. The cationic protein, bovine lactoperoxidase, was also adsorbed and desorbed with these temperature-responsive resins under similar conditions of changing temperature, whereas the anionic protein, bovine β-lactoglobulin, was not adsorbed under this regime of temperature conditions but instead eluted in the flow-through. [ABSTRACT FROM AUTHOR]

Using a simple molecular model and the configurational-bias Monte Carlo method combined with the parallel tempering technique, solvent driven changes in conformations of a homopolymer chain in a simple supercritical solvent are systematically investigated. The solvent is modelled as a square-well fluid, and two types of chain are considered: the flexible chain of tangentially touching (i) hard spheres (purely repulsive chain) and (ii) square-well spheres (purely attractive chain). The mean square end-to-end distance and radius of gyration are the main quantities computed and used to characterize the changes in conformations in dependence on the temperature and density of the solvent. It is found that the attractive chain exhibits both the upper and lower critical solution temperatures, whereas the repulsive chain exhibits only the upper critical solution temperature. [Copyright &y& Elsevier]

Lead halide perovskites have shown much promise for high-performing solar cells due to their inherent electronic nature, and though the color of bright-light emitters based on perovskite nanoparticles can be tuned by halide mixing and/or size control, dynamic switching using external stimuli remains a challenge. This article reports an unprecedented lower critical solution temperature (LCST) for toluene solutions containing methylammonium lead bromide (MAPbBr 3 ), oleic acid, alkylamines, and dimethylformamide. The delicate interplay of these molecules and ions allows for the reversible formation and decomposition of MAPbBr 3 nanoparticles upon heating and cooling, which is accompanied by green and blue photoemissions at each state. An intermediate 1D crystal with PbBr 2 -amine coordination is found to play pivotal role in this, and a mechanistic insight is provided based on a three-state model. In addition to a high quantum yield (up to 85%), this system allows for control over the cloud point (30-80 °C) through compositional engineering and the luminescent color (blue to red) via halogen exchange, thus making it a versatile solution for developing functional molecular organic-inorganic LCST quantum dots., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)