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Poly (acrylic acid) (PAA), an anionic polymer was used to prepare ion pair self-assembly (IPSAM) with 4-(methylthio)aniline (MTA), a hydrophobic counter ion, which is responsive to temperature and oxidation. The IPSAM was formed when the carboxylic to amino group molar ratio was 7/3-5/5. The structure of the IPSAM nanoparticle was spherical whose diameter was 30-40 nm on the TEM images. The PAA/MTA ion pair showed the upper critical solution temperature (UCST) that hiked with increasing MTA content. When the MTA of the ion pair was oxidized by H2O2, the UCST was also increased. The amphiphilic property of the ion pair was responsible for interface activity which declined upon the oxidation of the MTA. The surface tension was low for the ratio of PAA/MTA (5/5), which made the 5/5 ratio suitable for further studies. The interaction between PAA and MTA, which was ionic, and the oxidation of MTA was confirmed by FT-IR spectroscopy. The release of payload (i.e. Nile red) in IPSAM was restrained below the UCST but it was triggered above the phase transition temperature possibly due to the disintegration of the IPSAM whereas on MTA oxidation the release was shielded due to more hydrophobicity. The release was found to be higher in tumor environment temperature which could be controlled with the input concentration of H2O2 giving a stable IPSAM. The cell viability results showed that IPSAM has no significant cytotoxicity and can serve as a drug carrier for stimulus-response. [ABSTRACT FROM AUTHOR]

Swelling is ubiquitous for conventional hydrogels but is not favorable for many situations, especially underwater applications. In this study, an anti‐swelling and mechanically robust polyacrylic acid (PAAc)/gelatin composite hydrogel is reported with a rapid gelation process (101 s) under mild conditions via the synergy of MXene‐activated initiation and zirconium ion (Zr4+)‐induced cross‐linking, without the requirement of external energy input. The MXene is found efficient to activate the chain initiation, while the Zr4+ is prone indispensable for facilitating the cross‐linking of formed polymer chains. The resulting hydrogel exhibits integration of exceptional anti‐swelling properties and high mechanical performance at room temperature, thanks to the dense hydrogen bonds between PAAc and gelatin chains that enable an upper critical solution temperature above room temperature. Also, desirable electrical conductivity emerges in the hydrogel due to the simultaneous contribution of MXene and Zr4+, allowing stable electrical signal output of the gel upon deformation underwater. As a demonstration, an underwater communicator by harnessing the gel as a sensing module is assembled, which is capable of wirelessly delivering messages to the decoder on the ground via Morse codes. This study provides an exemplary way for the rapid gelation of tough and anti‐swelling hydrogels for durable underwater applications. [ABSTRACT FROM AUTHOR]

Near-infrared light (NIR) triggered transdermal drug delivery systems are of great interest due to their on-demand drug release, which enable to enhance drug treatment efficiency as well as reduce side effect. Herein, a NIR-triggered microneedle (MN) patch array has been fabricated through depositing the photothermal conversion agent and anti-diabetic drug-loaded polymer vesicles with upper critical solution temperature (UCST) into dissolvable polymer matrix. The UCST-type polymer has a clearing point temperature of 41 °C and the drug-loaded polymer vesicles present excellent NIR-triggered and temperature responsive drug release behavior in vitro due to the disassociation of polymer vesicles upon NIR irradiation. After applying MNs to diabetic rats, significant hypoglycemic effect is achieved upon interval NIR irradiation and the blood glucose concentration can decrease to normal state for several hours, which enables to achieve the goal of on-demand drug release. This work suggests that the NIR-triggered MN drug release device has a potential application in the treatment of diabetes, especially for those requiring an active drug release manner. [ABSTRACT FROM AUTHOR]

Cucurbit[6]uril‐derivatized vinyl monomer (cucurbit[6]uril methacrylate) was synthesized. Acrylic acid (AA) was used as the comonomer for copolymerization with the cucurbit[6]uril‐derivatized monomer. A series of copolymers of poly(acrylic acid‐co‐cucurbit[6]uril methacrylate) (PAA‐co‐CB[6]MA) were synthesized by free radical polymerization. The cucurbit[6]uril‐derivatized monomer and PAA‐co‐CB[6]MA copolymers were characterized by 1H NMR spectra, high‐resolution mass spectroscopy and gel permeation chromatography. The solution behavior was examined using UV–visible spectroscopy and dynamic light scattering. The PAA‐co‐CB[6]MA showed an upper critical solution temperature (UCST) in water. The UCST‐type thermoresponsive behavior of these CB[6]‐derivatized copolymers was highly dependent on the composition of the copolymer. For the same type of copolymer, changes in its composition gave rise to different UCSTs. Additionally, the PAA‐co‐CB[6]MA copolymers were successful in trapping azocarmine B. The stimuli‐responsive release of encapsulated azocarmine B was achieved by a combination of temperature and pH value stimuli. According to the results, the novel PAA‐co‐CB[6]MA copolymers can be used as carriers. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Water‐soluble and thermoresponsive macrocycles with stable inclusion toward guests are highly valuable to construct stimuli‐responsive supramolecular materials for versatile applications. Here, we develop such macrocycles – ureido‐substituted cyclodextrins (CDs) which exhibit unprecedented upper critical solution temperature (UCST) behavior in aqueous media. These novel CD derivatives showed good solubility in water at elevated temperature, but collapsed from water to form large coacervates upon cooling to low temperature. Their cloud points are greatly dependent on concentration and can be mediated through oxidation and chelation with silver ions. Significantly, the amphiphilicity of these CD derivatives is supportive to host‐guest binding, which affords them inclusion abilities to guest dyes. The inclusion complexation remained nearly intact during thermally induced phase transitions, which is in contrast to the switchable inclusion behavior of lower critical solution temperature (LCST)‐type CDs. Moreover, ureido‐substituted CDs were exploited to co‐encapsulate a pair of guest dyes whose fluorescence resonance energy transfer process can be switched by the UCST phase transition. We therefore believe these novel thermoresponsive CDs may form a new strategy for developing smart macrocycles and allow for exploring smart supramolecular materials. [ABSTRACT FROM AUTHOR]

This study focuses on analyzing the noncovalent interaction patterns between three lipid‐nanodisc‐forming polymers and nitroxide radicals which are used as small organic tracer molecules. Besides the negatively charged polymers diisobutylene/maleic acid (DIBMA) and styrene/maleic acid (SMA) (2:1), the solvation behavior of a newly synthesized zwitterionic styrene/maleic amide sulfobetaine copolymer named SMA‐sulfobetaine (SB) is characterized. The applied spin probes vary in their respective chemical structure, allowing the report of different local micropolarities and nanoscopic regions by recording temperature‐dependent continuous‐wave electron paramagnetic resonance (CW EPR) spectra. In combination with light scattering experiments, a nanoscopic interpretation of the dominant polymer/guest molecule interaction patterns is provided. The results indicate that in SMA and DIBMA, ionic interactions dominate the interaction patterns with other molecules. In SMA‐SB, the zwitterionic side chains mainly induce a dynamic assembly with guest molecules due to weaker noncovalent interactions. Depending on the applied spin probe, temperature‐dependent CW EPR measurements reveal nanoscopic cloud points depending on the interaction patterns with SMA‐SB which can occur more than 20 °C below its macroscopically observed upper critical solution temperature. Finally, the detailed dissection of interaction patterns may provide a better understanding that may even allow tuning the polymers' properties for use in lipid nanodisc formation. [ABSTRACT FROM AUTHOR]

The synthesis of thermo‐responsive polymers from non‐responsive and water‐soluble monomers has great practical advantages but significant challenges. Herein, the authors report a novel aqueous copolymerization strategy to prepare polymers with tunable upper critical solution temperature (UCST) or lower critical solution temperature (LCST) from non‐responsive monomers. Acrylic acid (AAc), N‐vinylpyrrolidone (NVP), and acrylamide (AAm) are copolymerized in water, yielding copolymers with UCST behavior. Interestingly, by simply replacing AAm with its methylated homologue, dimethyl acrylamide (DMA), the thermo‐responsiveness of the copolymers is converted into LCST‐type. The cloud points of the copolymers can be tuned rationally with their monomer ratios and the condition of the solvent. The UCST property of the poly(AAc–NVP–AAm) comes from the AAc–AAm and AAc–NVP hydrogen‐bonds, while the LCST property of poly(AAc–NVP–DMA) originates from the hydrophobic aggregation of AAc–NVP complex and DMA, as indicated by temperature‐dependent 1H NMR and dynamic light scattering. [ABSTRACT FROM AUTHOR]

Nonionic double thermoresponsive diblock copolymers with both upper critical solution temperature (UCST) and lower critical solution temperature (LCST) phase transitions are synthesized via eco‐friendly photoiniferter reversible addition–fragmentation chain transfer polymerization. While the biocompatible random copolymer of di(ethylene glycol) methyl ether methacrylate and oligo(ethylene glycol) methacrylate accounts for the LCST transition, the block of polymethacrylamide from an easily accessible monomer with low health hazard is responsible for the UCST transition. Temperature‐dependent dynamic light scattering measurements confirm the formation of micellar aggregates in water at the temperatures below UCST‐ and above LCST‐type cloud points. Additionally, the temperature interval between UCST and LCST, where both blocks are dissolved, can be tailored by varying the comonomer ratio in the random copolymer block. With these unique advantages, the presented work introduces a new polymer system for the design of schizophrenic polymers. [ABSTRACT FROM AUTHOR]

Polyetherimide (PEI) nanoparticles with the size range from about 200 nm to 1 μm were successfully prepared from a PEI/DMSO solution by a simplified cooling-down method. The formation of PEI nanoparticles is caused by the temperature drop. The particle size is related to the temperature, cooling time, and PEI concentration. At low concentrations, well-separated PEI nanoparticles appear, and the lower the concentration is, the narrower the particle size distribution is. At high concentrations, a membrane structure appears, meaning that evaporation at room temperature rather than centrifugation would be a better way to separate the PEI nanoparticles from the PEI/DMSO suspension. [ABSTRACT FROM AUTHOR]

Copolymers of acrylamide (AAm) and hydrophobic monomers are known as non‐ionic polymers to show an upper critical solution temperature (UCST) in aqueous solution. By utilizing cyclic ketene acetals and carrying out the radical ring opening polymerization along with copolymerization with AAm, a UCST polymer, poly(acrylamide‐co‐2‐methylene‐1,3‐dioxepane) (P(AAm‐co‐MDO)), is obtained. The AAm/MDO content results in the shift of UCST phase transition temperature. The present work shows how the combination of water‐soluble PAAm and polycaprolactone‐like structured PMDO develops a new type of thermoresponsive polymer which can be expected for bio‐related applications. [ABSTRACT FROM AUTHOR]

The influence of temperature on the miscibility of the {methanol + p-xylene + isooctane} and {methanol + benzene + isooctane} ternary systems at atmospheric pressure are investigated. The effect of temperature on the phase equilibrium is discussed for each system. All chemicals are verified using gas chromatograph, density, viscosity and refractive index. Phase equilibrium are reached using a modified version of measurement equipment used previously. Some ternary systems and binary subsystems are taken from the literature at different temperatures to determine the influence of the temperature on the systems. The upper critical solution temperature for the methanol + isooctane binary system was determined by the constant-composition method with an accuracy of ± 0.1 K. Experimental data are compared with the literature. Calculated values by the non-random two liquids (NRTL) and universal quasi-chemical (UNIQUAC) equations are contrasted with experimental data for the ternary systems. Deviations from the experimental binodal curve have good adjustment of less than one per cent for all systems. [ABSTRACT FROM AUTHOR]

Thermoresponsive polypeptides bearing amide pendants with an upper critical solution temperature (UCST) under physiologically relevant solution conditions are developed. A series of poly(γ‐propanyl‐l‐glutamate)s bearing amide pendants (PPLGn‐Am) with different molecular weight (or degree of polymerization, DP) is prepared by copper mediated 1,3‐dipolar cycloaddition. While fourier transform infra‐red and CD analysis reveal random coil conformation of the PPLGn‐Am in the solid‐state and in aqueous solutions, respectively, PPLGn‐Am shows reversible UCST‐type phase behaviors in deionized water (DI) water and phosphate‐buffered saline. Variable temperature UV–vis spectroscopy indicates that the UCST‐type cloud point temperature (Tcp) in the range of 25–75 °C can be readily tuned by molecular weight (or DP), polymer concentration, and incorporation of hydrophobic (i.e., n‐hexyl) pendants. Moreover, PPLGn‐Am is readily degraded by proteinase K within 48 h. The results indicate that UCST‐type thermoresponsive and biodegradable polypeptides in aqueous solutions can be constructed by conjugation of amide pendants which shall provide guidance for future UCST polymer designs. [ABSTRACT FROM AUTHOR]

Currently, the phase transition of aqueous binary systems containing thermoresponsive (co)polymers, and exhibiting upper critical solution temperature (UCST), is exclusively investigated in dilute solutions, which can limit the knowledge of their UCST‐type phase transition. Herein, a photo‐RAFT polymerization approach, using acrylamide (AAm) and acrylonitrile (AN) as monomer models, is used to prepare well‐controlled poly(AAm‐co‐AN) copolymers "in situ" in highly concentrated dispersions (60 wt%). The impact of the copolymer concentration and the chemical composition (as a variation of AN fraction in the copolymers) on the cloud point temperature (TCP) are investigated using turbidity measurements. Importantly, the results show that upon increasing the polymer concentration, a sharp increase of TCP up to a maximum point is observed, representing the UCST, before the decrease of TCP at higher polymer concentrations. Finally, a model equation is developed to fit the UCST values of poly(AAm‐co‐AN), which can be useful to design new poly(AAm‐co‐AN) copolymers with a desired UCST for a specific application. [ABSTRACT FROM AUTHOR]

This study was undertaken to investigate the extraction of In3+ and Ga3+ by 7-(4-ethyl-1-methyloctyl)-8-hydroxy-quinoline (Kelex100), which has been found to be a slow extraction process. Homogeneous liquid-liquid extraction utilizing upper critical solution temperature of 4-methyl-1,3-dioxolan-2-one (propylene carbonate, abbreviated as PC) was used to eliminate the interface and speed up the extraction, since distribution between two phases was thought to be the rate-determining step. The effect of contact time on the percentage of metal extraction was examined at 80ºC using Kelex100 dissolved in toluene and PC solutions and the difference between two solvents was evaluated. The results clearly show that the use of homogeneous liquid-liquid extraction using PC with Kelex100 is faster than traditional two phase extraction. [ABSTRACT FROM AUTHOR]

Aqueous two-phase system (ATPS) formation is the macroscopic completion of liquid-liquid phase separation (LLPS), a process by which aqueous solutions demix into 2 distinct phases. We report the temperature-dependent kinetics of ATPS formation for solutions containing a monoclonal antibody and polyethylene glycol. Measurements are made by capturing dark-field images of protein-rich droplet suspensions as a function of time along a linear temperature gradient. The rate constants for ATPS formation fall into 3 kinetically distinct categories that are directly visualized along the temperature gradient. In the metastable region, just below the phase separation temperature, Tph, ATPS formation is slow and has a large negative apparent activation energy. By contrast, ATPS formation proceeds more rapidly in the spinodal region, below the metastable temperature, Tmeta, and a small positive apparent activation energy is observed. These region-specific apparent activation energies suggest that ATPS formation involves 2 steps with opposite temperature dependencies. Droplet growth is the first step, which accelerates with decreasing temperature as the solution becomes increasingly supersaturated. The second step, however, involves droplet coalescence and is proportional to temperature. It becomes the rate-limiting step in the spinodal region. At even colder temperatures, below a gelation temperature, Tgel, the proteins assemble into a kinetically trapped gel state that arrests ATPS formation. The kinetics of ATPS formation near Tgel is associated with a remarkably fragile solid-like gel structure, which can form below either the metastable or the spinodal region of the phase diagram. [ABSTRACT FROM AUTHOR]

A novel class of aqueous biphasic systems (ABS) formed by zwitterions (ZI) has been investigated in the present work. A series of water soluble ZIs have been synthesized using triethylamine, N-Methylimidazole, N-Vinylimidazole, pyridine, N-Methylpyrrolidine, N-Ethylpiperidine and 1,4 butane sultone. The synthesized ZIs were explored for their ability to form biphasic systems in combination with aqueous inorganic salt solutions of K3PO4, K2HPO4 and K2CO3. The phase diagrams for all systems have been constructed through cloud point titration method at 298.15 K and atmospheric pressure. The phase behavior of ZI based ABS have been analyzed to understand the structural effects of ZIs as well as the effect of nature of salt used on the overall phase formation. Further the temperature dependence of the ZI based ABS was also explored by studying the phase behavior at variable temperatures of 298.15, 308.15 and 318.15 K. In order to estimate the applicability of proposed ZI based ABS, extraction experiments have been performed for an alkaloid i.e. caffeine for all synthesized ZIs with K3PO4 and at 298.15 K. ZI based ABS have been found to be capable of single step extraction of caffeine similar to IL based ABS thus providing the possibilities to explore these ZI based ABS as efficient extraction and separation systems. [ABSTRACT FROM AUTHOR]

Homopolypeptide bearing azobenzene and triethylene glycol spacers, and 1-butylimidazolium pendants, namely P(Azo-OEG3-ImX) (X = Cl, I, BF4) are prepared by 1,3-dipolar cycloaddition and subsequent ion-exchange reaction. Both 1H NMR and FTIR confirm the polymer structures and reveal a high grafting efficiency (97%). P(Azo-OEG3-ImI) shows reversible upper critical solution temperature (UCST)-type thermoresponsive property in ethanol while P(Azo-OEG3-ImI/BF4) shows a UCST in ethanol/water solvent mixtures. P(Azo-OEG3-ImI) shows UCST-type phase transitions in ethanol or ethanol/water solvent mixtures. After UV irradiation, the UCST-type cloud point temperature (Tcp) remains constant in ethanol. However, it decreases after UV irradiation and increases after visible light irradiation in ethanol/water solvent mixtures due to the trans-cis isomerization of azobenzene moieties. P(Azo-OEG3-ImCl/I) shows NaI-induced UCST in water. The Tcp of the P(Azo- OEG3-ImCl/I) aqueous solution is highly related to the polymer/salt concentration and nature of counteranions. P(Azo-OEG3-ImCl) also shows reversible light-responsive properties in NaI aqueous solutions. Higher NaI concentration is needed to induce a UCST for P(Azo-OEG3-ImCl) after UV irradiation. Moreover, ciprofloxacin-loaded hydrogel containing P(Azo-OEG3-ImCl) shows more efficient drug release while the UV irradiation leads to slightly low drug release. [ABSTRACT FROM AUTHOR]

Abstract: Phase diagrams of the polyphenylsulfone (PPSU)-polyethylene glycol (PEG)-N-methyl-2-pyrrolidone (NMP) system have been plotted as a function of PEG molecular weight. For 15 wt % PPSU solutions containing 15 wt % of PEG with molecular weight of 6000-40 000 g mol-1, the occurrence of an upper critical solution temperature (UCST, solution-gel transfer (gel point)) and a lower critical solution temperature (LCST) was found. According to the phase diagrams analysis, a method for the preparation of high flux PPSU membranes using the systems with UCST and LCST in an experimentally attainable temperature range has been proposed. The method involves casting solution processing at a temperature of the existence of a one-phase homogeneous solution (UCST < T < LCST), and the use of a coagulation bath at a temperature between UCST (gel point) and LCST. Membranes prepared from 15 wt % PPSU solutions with the addition of PEG-20000 were found to have the highest pure water flux (500-1000 L m-2 h-1 at 0.1 MPa), and a human serum albumin rejection of ca. 90%. [ABSTRACT FROM AUTHOR]

Abstract: A thermoresponsive lipase catalyst with an upper critical solution temperature (UCST) of about 26 °C was exploited by covalent immobilization of an enzyme, Pseudomonas cepacia lipase (PSL), onto poly(acrylamide‐co‐acrylonitrile) by glutaraldehyde coupling. The experimental conditions for the PSL immobilization were optimized. The immobilized PSL was much more stable for wide ranges of temperature and pH than free PSL. The material was also evaluated as an asymmetric catalyst in the kinetic resolution of racemic α‐methylbenzyl butyrate at 55 °C in an aqueous medium and exhibited high catalytic performance and stability. Up to 50 % conversion and 99.5 % product enantiomeric excess were achieved, thus providing highly pure enantiomers. This biocatalyst could be easily recovered by simple decantation for reuse based on temperature‐induced precipitation. It showed good reusability and retained 80.5 % of its original activity with a well reserved enantioselectivity in the 6th cycle. This work would shed light on the future development of new UCST‐type enzyme catalysts. [ABSTRACT FROM AUTHOR]

The upper critical solution temperature (UCST) of poly(ethylene imine)/cinnamic acid (PEI/CA) conjugate decreased as the tris(hydroxymethyl) aminomethane (THMAM) concentration increased. On the optical micrographs of PEI/CA mixture solutions at 25°C, the microspheres were found when the THMAM concentration was 0 mM and 100 mM, but hardly found at 200 mM. Monoolein (MO) cubic phase containing PEI, CA, and THMAM exhibited a bilayer structure on the TEM micrograph. The release degree of methylene blue loaded in the cubic phase was not strongly dependent on THMAM concentration at 25°C and 37°C, but strongly dependent on the concentration at 50°C. [ABSTRACT FROM PUBLISHER]

We report a near-infrared (NIR) light-responsive hydrogel that is capable of undergoing the gel to sol transition upon 785 nm light exposure based on a photothermal effect. The new hydrogel design relies on loading gold nanorods (AuNRs) in an ABA-type triblock copolymer, namely P(AAm–co–AN)–b–PDMA–b–P(AAm–co–AN), where P(AAm–co–AN) stands for a random copolymer of acrylamide and acrylonitrile that exhibits an upper critical solution temperature (UCST) in aqueous solution and PDMA is water-soluble polydimethylacrylamide. At solution temperature below UCST, the insoluble P(AAm–co–AN) blocks lead to formation of hydrogel of flower-like micelles. When the hydrogel is exposed to 785 nm NIR light, the absorption due to the longitudinal surface plasmon resonance of loaded AuNRs generates heat that raises the hydrogel temperature above UCST and, consequently, the gel-to-sol transition. The NIR light-triggered release of a protein loaded in the hydrogel was found to display a switchable fashion. [ABSTRACT FROM AUTHOR]

A series of ionic polypeptides bearing p-tolyl pendants and 3-methyl-1,2,3-triazolium linkages is synthesized by N-alkylation and subsequent ion-exchange reaction. 1H NMR and Fourier transform infrared (FTIR) analysis verify their molecular structures and reveal quantitative conversions. The nonionic polypeptides bearing p-tolyl pendants and 1,2,3-triazole linkages show no thermoresponsiveness in various solvents. The resulting ionic polypeptides (i.e., P2) are able to show reversible upper critical solution temperature (UCST)-type phase behaviors both in methanol and ethanol/water binary solvent mixtures by incorporation with proper counteranions (i.e., iodide). FTIR analysis reveals that P2 may have interacted with solvent molecules via the van der Waals interaction, H-bonding, and dipolar-dipolar interactions. Variable-temperature UV-vis spectroscopy reveals that the UCST-type phase transition temperatures ( Tpts) of P2 are in the range of about 26-37 °C in MeOH and in the range of about 11-46 °C in EtOH/H2O solvent mixtures depending on the main-chain length, polymer concentration, and the weight percentage of ethanol ( fw). [ABSTRACT FROM AUTHOR]

A simplified one-pot and less harmful method has been introduced for the synthesis of borinic acid monomer. The corresponding borinic acid polymer (PBA) has been prepared by reversible addition-fragmentation chain transfer polymerization. Property investigations confirm the characteristics of PBA as a new type of 'smart material' in the field of thermo-responsive polymer. The potential application of PBA in the field of enzymatic biofuel cell has been illustrated with a wide open circuit potential of 0.92 V. [ABSTRACT FROM AUTHOR]

A series of glycopolypeptides with constant main-chain lengths and various compositions of mannose moieties and biphenyl pendants were synthesized by copper-mediated 1,3-dipolar cycloadditions. 1H NMR and Fourier transform IR (FTIR) analysis confirmed the molecular structures of the resulting polypeptides. FTIR analysis characterized the molar contents of the mannose pendants and α-helical conformations in the solid state. Glycopolypeptides conjugated with tetra- O-acetyl- d-(+)-mannopyranoside showed a reversible upper-critical-solution-temperature-type (UCST-type) phase behavior both in MeOH/H2O and EtOH/H2O binary solvent mixtures depending on the weight percentage of alcohols ( fw). Incorporation of a low content of biphenyl pendants (≤0.20) can broaden the range of fw at which polymers showed UCST-type phase behaviors. The UCST-type transition temperature ( Tpt) was highly related to the incorporation of biphenyl pendants, polymer concentrations, and the nature and weight percentage of alcohols. It decreased as the polymer concentration decreased and increased on incorporation of biphenyl groups. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The multiresponsive behavior of functionalized water-soluble conjugated polymers (CPs) is presented with potential applications for sensors. In this study, we investigated the aqueous solubility behavior of water-soluble CPs with high photoluminescence and with a particular focus on their pH and temperature responsiveness. For this purpose, two poly(phenylene vinylene)s (PPVs)—namely 2,5-substituted PPVs bearing both carboxylic acid and methoxyoligoethylene glycol units—were investigated, with different amount of carboxylic acid units. Changes in the pH and temperature of polymer solutions led to a response in the fluorescence intensity in a pH range from 3 to 10 and for temperatures ranging from 10 to 85 °C. Additionally, it is demonstrated that the polymer with the largest number of carboxylic acid groups displays upper critical solution temperature (UCST)-like thermoresponsive behavior in the presence of a divalent ion like Ca2+. The sensing capability of these water-soluble PPVs could be utilized to design smart materials with multiresponsive behavior in biomedicine and soft materials. [ABSTRACT FROM AUTHOR]

ABSTRACT A fast, one pot, solvent-free and metal-free synthesis of poly-ε-caprolactone and poly(ethylene oxide) block copolymers is reported. Copolymers with different molar mass, different hydrophilic to lipophilic balance, high degree of conversion and narrow molar mass dispersity have been obtained by organocatalyzed ring opening polymerization of ε-caprolactone in presence of mono- or diol-poly(ethylene oxide) as initiator and fumaric acid as catalyst. A new biocompatible and environmental friendly purification method is presented, exploiting the upper critical solution temperature of these class of copolymers in ethanol. The phase diagrams of the synthesized copolymers in ethanol are also reported. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2992-2999 [ABSTRACT FROM AUTHOR]

Characteristic properties of zwitterionic nanocomposite (NC) gels consisting of a sulfobetaine copolymer and inorganic clay were investigated. The zwitterionic NC gels were synthesized with different ratios of monomer ( x) and clay content ( n) by the in situ free-radical polymerization of two monomers, a sulfobetaine monomer (A3) and acrylamide derivative (D), in the presence of exfoliated clay in aqueous media. The resulting zwitterionic A3D x-NC n gels were all structurally uniform and mechanically tough because of the polymer-clay network. A3D x-NC n gels exhibited a thermoresponsive phase transition with an upper critical solution temperature (UCST) for x ≤ 10 and n ≤ 5. The changes in the property of the A3D10-NC3 gel across the UCST transition were elucidated in terms of optical transmittance, gel volume, dynamic viscoelasticity, and tensile mechanical properties, in addition to the change in self-healing behavior. [ABSTRACT FROM AUTHOR]

Water-miscible ionic liquids (ILs) may be salted out using kosmotropic salts such as potassium phosphate (KPO) to form salt-salt aqueous biphasic systems (ABS). The effect of temperature on these systems has been studied using phase diagrams and it is observed that the degree of binodal shift decreases (requiring lower IL and kosmotropic salt concentrations) with the increase of temperature following the trend [Cmim]Cl > [Cpy]Cl > [Cmmim] Cl ~ [N]Cl. This trend can be correlated with the decreasing hydrogen bonding abilities of each salt. The phase behavior was also interpreted on the basis of critical solution temperature behavior of pure aqueous ionic liquid solutions. Additionally, the distribution of alcohols in these systems was studied as a function of temperature and it was found that the distribution ratios did not change with changes in temperature. The Gibbs energy of transfer of a methylene group in these systems and correlation to tie-line length was also determined. It was concluded that while the miscibility of alcohols increases in the ILs with increasing temperature, phase divergence in the aqueous biphasic system decreases, and thus these competing forces tend to cancel each other out for small polar molecules. A comparison is provided for the response to temperature in the currently studied salt-salt systems and analogous ABS formed by the addition of hydrophilic polymers to kosmotropic salts (polymer-salt) or other polymers (polymer-polymer). [ABSTRACT FROM AUTHOR]

Thermally sensitive polymeric nanocarriers were developed to optimize the release profile of encapsulated compounds to improve treatment efficiency. However, when referring to thermally sensitive polymeric nanocarriers, this usually means systems fabricated from lower critical solution temperature (LCST) polymers, which have been intensively studied. To extend the field of thermally sensitive polymeric nanocarriers, we for the first time fabricated a polymeric drug delivery system having an upper critical solution temperature (UCST) of 43 °C based on an amphiphilic polymer poly(AAm-co-AN)-g-PEG. The resulting polymeric micelles could effectively encapsulate doxorubicin and exhibited thermally sensitive drug release both in vitro and in vivo. A drastically improved anticancer efficiency (IC50 decreased from 4.6 to 1.6 μg mL−1, tumor inhibition rate increased from 55.6 % to 92.8 %) was observed. These results suggest that UCST-based drug delivery can be an alternative to thermally sensitive LCST-based drug delivery systems for an enhanced antitumor efficiency. [ABSTRACT FROM AUTHOR]

Water-soluble polypeptides bearing 1-alkylimidazolium (methyl or n-butyl) and various counter-anions (i.e., Cl−, I− or BF4−) are prepared by ring-opening polymerization of γ-4-chloromethylbenzyl-l-glutamate-based N-carboxyanhydride ( 3), post-polymerization of poly( γ-4-chloromethylbenzyl-l-glutamate) ( 4), and ion-exchange reaction. Circular dichroism (CD) analysis reveals that the resulting polypeptides adopt an α-helical conformation in water with a fractional helicity in the range of 30%-56% at 20 °C and exhibit good conformational stability against temperature variations. The polypeptides exhibit lower critical solution temperature (LCST)-type or upper critical solution temperature (UCST)-type transitions in organic solvents or in water. The UCST-type transition temperature ( Tpt) in water is independent on the molecular weight, yet it decreases upon addition of NaCl and increases upon addition of NaI or NaBF4, suggesting a mainly electrostatic interaction mechanism. [ABSTRACT FROM AUTHOR]

Trithiocarbonate end-functionalized poly( N-acryloylglycinamide) (PNAGA), synthesized via reversible addition-fragmentation transfer (RAFT) polymerization of different molecular weights, is grafted onto gold nanoparticles (AuNPs) by ligand exchange in phosphate-buffered saline. The PNAGA-grafted AuNPs display upper critical solution temperature (UCST)-type transitions: stable colloidal distribution and aggregation above and below the cloud points, respectively. Cloud points of PNAGA are not affected by the grafting procedure, and PNAGA@AuNPs show similar cloud points as that of the trithiocarbonate end-functionalized free-PNAGAs used for grafting. The UCST-type phase transition is reversible for many cycles. The reversible control of the phase transition is proved by turbidity measurements and UV-vis spectroscopy, as well as by transmission electron microscopy (TEM). [ABSTRACT FROM AUTHOR]

A series of zwitterionic model polymers with defined molar masses up to 150,000?Da and defined end groups are prepared from sulfobetaine monomer N,N-dimethyl-N-(3-(methacrylamido)propyl)ammoniopropanesulfonate (SPP). Polymers are synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT) using a functional chain transfer agent labeled with a fluorescent probe. Their upper critical solution temperature-type coil-to-globule phase transition in water, deuterated water, and various salt solutions is studied by turbidimetry. Cloud points increase with polyzwitterion concentration and molar mass, being considerably higher in D2O than in H2O. Moreover, cloud points are strongly affected by the amount and nature of added salts. Typically, they increase with increasing salt concentration up to a maximum value, whereas further addition of salt lowers the cloud points again, mostly down to below freezing point. The different salting-in and salting-out effects of the studied anions can be correlated with the Hofmeister series. In physiological sodium chloride solution and in phosphate buffered saline (PBS), the cloud point is suppressed even for high molar mass samples. Accordingly, SPP-polymers behave strongly hydrophilic under most conditions encountered in biomedical applications. However, the direct transfer of results from model studies in D2O, using, e.g.1H NMR or neutron scattering techniques, to ‘normal’ systems in H2O is not obvious. [ABSTRACT FROM AUTHOR]

A new type of smart borinic acid polymer with luminescence and multiple stimuli-responsive properties is reported. In DMSO with small amounts of water, the homopolymer PBA shows a tunable upper critical solution temperature (UCST). As the amount of water increases from 0 to 2.5 % (v/v), the UCST rises linearly from 20 °C to 100 °C (boiling point of water). Thus, the thermal responsive behavior can be tuned over a wide temperature range. Furthermore, polymer solutions in DMSO show a reversible response to fluoride ions, which can be correlated to the presence of the Lewis acidic borinic acid groups. Upon addition of fluoride, the polymer becomes soluble because the functional R2BOH groups are converted into ionic [R2BF2]− groups, but turns insoluble again upon addition of H2O, which reverses this process. [ABSTRACT FROM AUTHOR]

The first example of a chemically crosslinked synthetic non-ionic hydrogel showing reversible positive swelling behavior in pure water as well as electrolyte solution is highlighted. Homopolymeric hydrogels are synthesized from N-acryloylglycinamide with N, N′-methylenbis(acrylamide) as a chemical crosslinker via free radical polymerization in dimethyl sulfoxide (DMSO). The swelling-ratio dependency of the hydrogels upon temperature as well as on the amounts of crosslinker from 1 to 4.8 mol% is studied. With 1 mol% crosslinker, the hydrogel is able to take up over three times water of its weight at 37 °C in pure water and phosphate-buffered saline. All the samples show almost 100% of reversibility for at least 6 d up to 37 °C irrespective of the amount of the crosslinker, making them promising candidates for biomedical applications. The sample with a higher amount of crosslinker, i.e., 4.8 mol% is even stable for over 6 d at 70 °C. [ABSTRACT FROM AUTHOR]

ABSTRACT The change of polymerization method from conventional free radical polymerization to the reversible addition fragmentation chain transfer (RAFT) method provided thermoresponsive behavior of upper critical solution temperature (UCST)-type in water to copolymers of styrene (St) and acrylamide (AAm). Sample preparation conditions (temperature and time of dissolution) for turbidity measurements could also significantly influence the thermoresponsive behavior of polymers based on AAm. Poly(AAm- co-St)s made by RAFT method till high conversions showed sharp cloud points ranging 50-62 °C with low hysteresis in water depending upon the copolymer composition. Samples for turbidity measurements were prepared under optimized conditions, that is, 70 °C for 1.5 h. In contrast, the copolymers made by conventional radical polymerization in all copolymer composition range were not thermoresponsive. The example [poly(AAm- co-St)] emphasizes the importance of compositional homogeneity of macromolecular chains for showing UCST-type transitions in water for a system with wide difference in reactivity ratios of the comonomers. Since, examples of polymeric systems showing UCST in water are not too many, this work highlights how compositional homogeneity would help in developing many more systems with tuned cloud points. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1878-1884 [ABSTRACT FROM AUTHOR]

The liquid-liquid phase separation kinetics and phase behaviour of hydrogenated polyethylene and deuterated polypropylene blends have been systematically studied by optical microscope. Phase diagram was constructed from the phase transition temperature. The hydrogenated polyethylene/deuterated polypropylene blend exhibits upper critical solution temperature in the melt. The time evolution of the characteristics morphology for liquid-liquid phase separation is determined for the hydrogenated polyethylene/deuterated polypropylene blend at various compositions and following a quench from initial homogenous melts at higher temperature to various lower temperatures. Liquid-liquid phase separation kinetics follows nucleation and growth mechanism. The experimental results from optical microscope measurement at various conditions are all consistent with the nucleation and growth mechanism. [ABSTRACT FROM AUTHOR]

A new thermosensitive poly( N-propionyl-aspartic acid/ethylene glycol) (PPAE) with no cytotoxicity and an upper critical solution temperature (UCST) is synthesized by polycondensation of l-aspartic acid and ethylene glycol. The chemical structures of the monomer and polymer are confirmed by FTIR and 1H NMR spectroscopy, and by elemental analysis measurements. Turbidimetric measurements indicate that PPAE shows a reversible UCST phase transition at 1.5-37.6 °C in pure water or an alcohol/water mixture. The UCST can be facilely tuned via changing the content of alcohol in water or the normal saline. Moreover, the survival rate of HeLa cells to PPAE is close to 100% within 48 h, demonstrating no cytotoxicity. Such aspartic acid-based polymers with tunable thermosensitivity could be useful in the biomedical field. [ABSTRACT FROM AUTHOR]

Zwitterionic nanocomposite gels (Zw-NC gels) composed of a zwitterionic sulfobetaine copolymer and inorganic clay (hectorite) are synthesized through the in situ free-radical copolymerization of N,N-dimethyl(acrylamidopropyl)ammonium propanesulfonate (90 mol%) and N,N-dimethylacrylamide (10 mol%) with exfoliated clay platelets in an aqueous medium. The effects of polymer concentration ( Cp) on the dynamic viscoelasticity, tensile mechanical properties, transparency, and the thermosensitivity with the upper critical solution temperature (UCST) of the Zw-NC gels are investigated in the range Cp = 26-260 g L−1 and are compared with those of chemically cross-linked zwitterionic gels. All the mechanical and thermosensitive properties strongly change depending on the type of network and Cp. The Cp-induced changes in the polymer-clay structure of the Zw-NC gel are discussed based on the mechanical, optical, and thermosensitive properties, and on transmission electron microscopy and X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

A double hydrophilic block copolymer, poly(ethylene glycol)-poly(3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate) (PEG-SB), is synthesized by reversible addition-fragmentation transfer (RAFT) polymerization using PEG methyl ether (4-cyano-4-pentanoate dodecyl trithiocarbonate) as a chain transfer agent. PEG-SB forms multi-layered microspheres with dipole-dipole interactions of the SB side chains as the driving force. The PEG-SB polymers show an upper critical solution temperature (UCST) and the UCST is controllable by the polymerization degree. The PEG-SB microspheres are dissociated above the UCST and then monodispersed microspheres (∼1 μm) are obtained when the solution temperature is decreased below the UCST again. The disassociation/association of the microspheres is also controllable using the concentration of NaCl. These multi-responsive microspheres could be a powerful tool in the field of nano-biotechnology. [ABSTRACT FROM AUTHOR]

The synthesis of cationic mono-(6- O-(1-vinylimidazolium))-ß-cyclodextrin with toluenesulfonate as the corresponding anion is described. Free-radical copolymerization of the resulting host-guest complex with N-isopropylacrylamide or N,N-diethylacrylamide yielded copolymers showing a temperature-controlled solubility window in water. The impact of different anionic guests and salt concentrations on solubility behavior was investigated via turbidity measurements. [ABSTRACT FROM AUTHOR]

N-Acryloylglycinamide was polymerized via the reversible addition fragmentation transfer process without sacrificing its key property, the upper critical solution temperature in water. This could be achieved by choosing an appropriate nonionic initiator [2,2′-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V-70)] and nonionic chain-transfer agent (cyanomethyl dodecyl trithiocarbonate). A good molar mass control was accomplished as proved by the linear increase of molar mass with conversion, a chain extension experiment, and low dispersity. The influence of molar mass, polymer end groups, or salt concentration on the cloud point was analyzed by turbidimetry. Polymer end groups exerted a distinct effect on the cloud points, whereas the influence increased with decreasing molar masses. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Comb-like copolymer of N-phenyl maleimide and n-octadecyl vinyl ether was synthesized by conventional free radical solution polymerization. The molecular weight and molecular weight distribution were measured by GPC. The chemical composition of copolymer was characterized by FT-IR, H NMR and C NMR, and the results indicated that the obtained copolymer contained much more content of N-phenyl maleimide rather than equal molar ratio of monomer unit. The comb-like copolymer can exhibit upper critical solution temperature thermoresponsive phase behavior reversibly in N, N-dimethylformamide and some proper alcohols such as 1-butanol, 1-hexanol, etc. The effect of polymer concentration and co-solvent on thermoresponsive behavior of polymer solution was investigated, and the cloud point of polymer solution can be tuned conveniently. The high resolution H NMR method was used to comprehend the reversible thermoresponsive behavior in molecular level, and the results revealed that as temperature decreased the pendent long alkyl side chain aggregated and phase separation occurred at cloud point temperature; however, the mobility of main polymer chain decreased at lower temperature. [ABSTRACT FROM AUTHOR]

The phase behavior of branched polycarbonate (BPC) blends with poly(ethylene terephthalate- co-1,4-dimethyl cyclohexane terephthalate) copolyesters (PECT), as well as their rheological properties, were assessed. Even though BPC blends with PECT prepared by solvent casting proved to be immiscible, BPC and PECT copolyesters containing 1,4-dimethyl cyclohexane (CHDM) from 32 to 80 mole% formed homogeneous mixtures upon heating. The homogenization temperatures of the blends decreased with increasing CHDM content in PECT. The interaction energies of the BPC-PECT pairs calculated from the phase boundary in accordance with the lattice-fluid theory were positive and also decreased with increasing CHDM content in PECT. It was shown that the phase homogenization of these blends occurs upon heating when the combinatorial entropy term, which is favorable for miscibility, overcomes unfavorable energetic terms at elevated temperatures. A novel product, which is not limited by the drawbacks of linear polycarbonate (PC) and evidences processability superior to that of the PC/PECT blends, can be developed via the blending of BPC and PECT. [ABSTRACT FROM AUTHOR]

Upper critical solution temperatures (UCST) of water-phenol systems are reported with 0.1 mol kg-1 halide salts, carboxylic acids, 1.0% PEG 200 in water, and 0.01 mol kg-1 surfactants and polynuclear aromatic compounds namely benzene, naphthalene, anthracene, chrysene; and benzene derivatives solutions in phenol. The valence electrons and shell numbers, bascity, -CH3 and -CH2-, hydrophilic, hydrophobic and π conjugated electrons of respective additives have been noted to affect the UCST values and mutual solubilities of the water and phenol. The surfactants decrease the UCST values with higher mutual solubilities due to effective hydrophilic as well as hydrophobic interactions with aqueous and organic phases, respectively. The stronger structure breaking action of the 3(-OH) of the glycerol outweighs than those of the 3(-COO-) and 1(-OH) of the citric acid and the urea does produce almost equal UCST values as compared to glycerol. A decrease in the UCST values is noted with number of conjugated π electrons of the benzene, naphthalene, anthracene, and chrysene. In general, the dTc/dx2 values of salts for 0.20-0.16 mole fractions of phenol are found positive while for 0.055-0.052 mole fractions, the negative. [ABSTRACT FROM AUTHOR]

Upper-critical-solution-temperature (UCST) behavior in a ternary blend of poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene is reported. The as-cast ternary blend is immiscible at ambient conditions and comprises two different phases, and, however, turns into a miscible system above the “clarity point” ranging from 160 to 300 °C for different ternary compositions. The maximum clarity point is labeled as the UCST for the ternary system, which is about 295 °C. Above the clarity point, the originally immiscible ternary blend turned into one miscible phase. Owing to the thermodynamic UCST behavior and kinetic hindrance, the immiscible ternary polymer blend can be locked into a pseudo-miscible state if it is heated to a temperature above the clarity point followed by a rapid-cooling processing scheme. The quenched ternary blend can remain in a pseudo-miscible state as long as the service temperature does not exceed the glass-transition temperature of the blend. [ABSTRACT FROM AUTHOR]

Acetates of α‐1,3‐glucan dissolved in N,N‐dimethyl acetamide/LiCl are prepared by converting the polysaccharide with acetyl chloride, acetic acid anhydride/pyridine, or with acetic acid/N,N′‐carbonyl diimidazole. Values of the degree of substitution for the acetyl groups (DSAc) of up to 2.6 are realized. NMR spectroscopic measurements reveal a preferred conversion of the primary hydroxyl group at position 6 followed by positions 2 and 4. Depending on the DSAc, the samples may be soluble in solvents of different polarity at room temperature or at elevated temperatures showing upper critical solution temperature at DS of about 2.5. This process is found to be reversible. [ABSTRACT FROM AUTHOR]

A self‐healing composite hydrogel with thermoresponsive three‐stage optical adjustment (opaque‐transparent‐translucent) is achieved by combining polyampholyte hydrogel (PAH) with a small amount of poly(N‐isopropylacrylamide) (PNIPAM) nanogels. The PAH has an upper critical solution temperature to dominate the initial optical stage of reversible opaque‐transparent transition and also offers its self‐healing properties via reversible ionic bonds. Meanwhile, the PNIPAM shows a lower critical solution temperature by hydrophilic‐hydrophobic phase transition and synergistic clustering of PAH, which controls the subsequent optical stage of reversible transparent‐translucent transition. Therefore, the PAH/PNIPAM composite hydrogel shows a reversible three‐stage optical modulation by controlling temperature from low (<15 °C) to medium (15–30 °C) to high (>30 °C) via double phase transition behavior of PAH/PNIPAM. Through different analytical methods, the synergistic thermoreposensive effects of PNIPAM nanogels and the bulk PAH are demonstrated. Finally, a prototype of a smart window is designed to demonstrate one of its potential applications. A self‐healing composite hydrogel with thermoresponsive three‐stage optical adjustment (opaque‐transparent‐translucent) is achieved by combining polyampholyte hydrogel (PAH) with a small amount of poly(N‐isopropylacrylamide) (PNIPAM) nanogels. The initial reversible opaque‐transparent transition is controlled by the UCST of PAH, and subsequent reversible transparent‐translucent transition is contributed to the LCST of PNIPAM nanogels. [ABSTRACT FROM AUTHOR]

Thermally induced phase separation (TIPS) is a technique to prepare commercial membrane. However, the quick polymer crystallization during the quenching process will bring about a dense and thick skin layer and thus decrease permeability markedly. In this paper, a diluent mixture with upper critical solution temperature (UCST) was used to prepare polyvinylidene fluoride (PVDF) hollow fiber membrane. That is, the separation between diluent (propylene carbonate (PC)) and non-diluent (dioctyl terephthalate (DOTP)) occurred during the quenching process when the temperature of the dope was lower than 110 °C. The effects of separation between PC and DOTP and the resulting coalescence of DOTP on the PVDF crystallization process, microstructure, and the permeability of the membranes were analyzed. The results showed that the suitable PC/DOTP weight ratio reduced the thickness of the skin layer near the outer surface markedly and resulted in a porous outer surface, and the microstructure evolution process was proposed. The maximum pure water flux for the prepared membrane is up to 128.5 L·m−2·h−1 even in a dry mode without using a hydrophilizing agent. The rejection rate of the carbonic particle is nearly 100%. This study presents a novel and simple way to fabricate the microporous membrane with the interconnected pore structure. [ABSTRACT FROM AUTHOR]

A correction to the article "Antitumor Drug Delivery Modulated by A Polymeric Micelle Having Upper Critical Solution Temperature" that was published in the 2015 issue is presented.