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We investigated the pH-responsive behavior of the carboxybetaine-sulfobetaine diblock copolymer poly(2-(2-(methacryloyloxy)ethyl)dimethylammonio)acetate-block-3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate (PGLBT-b-PSPE) in aqueous solution under varying temperatures. Alongside the temperature-responsive PSPE block which induces self-assembly of polymer micelles under the upper critical solution temperature, the PGLBT motifs having protonation sites caused additional changes in the phase behaviors. In acidic conditions where the pH is lower than the pKa of PGLBT-b-PSPE, the transmittance of polymer solutions more abruptly dropped and became cloudy at higher temperatures compared to the case of salt-free solutions. There were two simultaneous diffusive modes in the turbid solutions equivalent to unimers or micelles and large aggregates over a few hundred nanometers. Unlike in neutral and basic conditions, those large aggregates did not disappear after the emergence of the polymer micelles. The trend of the temperature-responsive behavior hardly changed in the alkaline solutions; however, the critical temperature significantly decreased. The surface charge of the unimers and self-assembled objects determined by zeta potential measurement varied from neutral or negative to positive with proton addition and further positively increased below the micelle formation temperature. This indicates the cationization of PGLBT moieties and their arrangement in the outer layer of the polymer micelle surface. In spite of the positively charged outer surface, two fast and slow diffusive modes representing micelles and large clusters were repeatedly observed in acidic solutions, and to some extent, size-grown particles eventually precipitated.

In globular protein systems, upper critical solution temperature (UCST) behavior is common, but lower critical solution temperature (LCST) phase transitions are rare. In addition, the temperature sensitivity of such systems is usually difficult to tune. Here we demonstrate that the charge state of globular proteins in aqueous solutions can alter their temperature-dependent phase behavior. We show a universal way to tune the effective protein interactions and induce both UCST and LCST-type transitions in the system using trivalent salts. We provide a phase diagram identifying LCST and UCST regimes as a function of protein and salt concentrations. We further propose a model based on an entropy-driven cation binding mechanism to explain the experimental observations.

Thermoresponsive poly(methyl methacrylate) (PMMA) and EDA-modified PMMA-stabilized Pd nanoparticles were prepared and used as smart catalysts for the hydrogenation of 4-nitrophenol and hydrodechlorination (HDC) of 4-chlorophenol (4-CP) to realize the quasi-homogeneous reaction and heterogeneous separation. The catalysts were characterized via UV-visible spectroscopy, FT-IR spectroscopy and transmission electron microscopy (TEM). UV-visible spectroscopy shows that PMMA has an upper critical solution temperature (UCST) of 45.2 °C in an aqueous alcohol solution, and the EDA modification slightly increased the UCST value of the polymer. TEM characterization indicates highly dispersed Pd nanoparticles due to the stabilization by organic groups of the polymers. The kinetics study shows that the reduction of 4-nitrophenol was pseudo first order. High conversions of 4-nitrophenol and 4-chlorophenol were obtained on Pd/PMMA-EDA, which is similar to that on Pd-PVP and higher than those on Pd/PMMA and Pd/C. After the reaction, the soluble catalyst Pd/PMMA-EDA spontaneously precipitated from the solution with the decrease in temperature, and simply separated from the reaction medium for the next run. The Pd/PMMA-EDA catalyst can be reused more than three times with a slight decrease in activity.

International audience; A new kind of near-infrared (NIR) light-responsive polymer nanogel is demonstrated. The micellar aggregates of an ABA-type triblock copolymer, whose core is a thermosensitive polymer displaying an upper critical solution temperature (UCST), are crosslinked using a photothermal nickel-bis(dithiolene) complex that absorbs NIR light and converts efficiently optical energy into heat. We show that when the nanogel aqueous solution is exposed to NIR light, even at a low power density of 0.16 W cm(-2)and a low nickel-bis(dithiolene) complex concentration of 61.4 mu g mL(-1), the photothermally induced heating is sufficient to allow the nanogel particles to undergo a volume phase transition. The induced volume increase due to the positive thermosensitivity of the polymer leads to the release of loaded hydrophobic dye molecules. Using an energy balance model, the photothermal conversion efficiency of the nickel-bis(dithiolene) complex in the nanogel was evaluated through solution temperature and transmittance measurements under NIR laser irradiation at various light power densities as well as different nanoparticle concentrations and solvents. The photothermal conversion efficiency can reach about 64%, which positions the nickel-bis(dithiolene) complex among the most efficient photothermal agents in the NIR spectral region around 1000 nm.

Liquid-liquid microfluidic systems rely on the intricate control over the fluid properties of either miscible or immiscible mixtures. Herein, we report on the use of partially miscible binary liquid mixtures that lend their microfluidic properties from a highly temperature-sensitive mixing and phase separation behaviour. For a blend composed of the thermotropic liquid crystal 4-Cyano-4'-pentylbiphenyl (5CB) and methanol, mixing at temperatures above the upper critical solution temperature (UCST; 24.4°C) leads to a uniform single phase while partial mixing can be achieved at temperatures below the UCST. Thermally-driven phase separation inside the microfluidic channels results in the spontaneous formation of very regular phase arrangements, namely in droplets, plug, slug and annular flow. We map different flow regimes and relate findings to the role of interfacial tension and viscosity and their temperature dependence. Importantly, different flow regimes can be achieved at constant channel architecture and flow rate by varying the temperature of the blend. A consistent behaviour is observed for a binary liquid mixture with lower critical solution temperature, namely 2,6-lutidine and water. This temperature-responsive approach to microfluidics is an interesting candidate for multi-stage processes, selective extraction and sensing applications.

Dual thermo- and pH-responsive star polymers with tunable upper critical solution temperatures (UCST) were synthesized by an “arm-first” RAFT polymerization approach. Crosslinking took place in a single step involving polymerization of 3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate (DMAPS) mediated by a macroRAFT agent containing carboxylic end-group and in the presence of crosslinker N,N-methylenebis(acrylamide) (MBA). Varied-temperature turbidity analysis, dynamic light scattering (DLS) and rheology analysis revealed that the star-shaped PDMAPS had a smaller hydrodynamic volume while retaining fast response properties, compared with linearly-shaped PDMAPS. Meanwhile, zeta-potential was used to determine that the range of UCST regulated by pH was greatly expanded and proportional to the number of end-groups that could be generally manipulated through RAFT polymerization. By changing the pH values from 3 to 10, the adjustable UCST range of the star polymer solution can reach over 36 °C. These results demonstrate that the topological structure and end-group effect are able to manipulate the phase transition behavior of polyzwitterions. These materials offer great potential as additives or drug delivery vehicles in biomedical applications.

A dumbbell-shaped copolymer (PDMAEMA)4-PCL-SS-PCL-(PDMAEMA)4 with a lower critical solution temperature (LCST) and redox responses was first synthesized by the combination of ring opening polymerization (ROP), click chemistry and atom transfer radical polymerization (ATRP). Then a dumbbell-shaped copolymer (PDMAPS)4-PCL-SS-PCL-(PDMAPS)4 with an upper critical solution temperature (UCST) and redox responses was obtained through the quaternization reaction between DMAEMA and excess 1,3-propane sultone. Both (PDMAEMA)4-PCL-SS-PCL-(PDMAEMA)4 and (PDMAPS)4-PCL-SS-PCL-(PDMAPS)4 were amphiphilic, and they could self-assemble into spherical micelles under certain conditions. Benefitting from the LCST-type thermoresponse of PDMAEMA and UCST-type thermoresponse of PDMAPS, both dumbbell-shaped copolymers (PDMAEMA)4-PCL-SS-PCL-(PDMAEMA)4 and (PDMAPS)4-PCL-SS-PCL-(PDMAPS)4 presented temperature-responsive properties. The morphology and size of their assemblies would be changed when the temperature is altered. Meanwhile, due to the redox-response of disulfide bonds, both (PDMAEMA)4-PCL-SS-PCL-(PDMAEMA)4 and (PDMAPS)4-PCL-SS-PCL-(PDMAPS)4 showed redox-responsive properties. When DL-dithiothreitol (DTT) was added into the systems, disulfide bonds were broken, causing the change of (PDMAEMA)4-PCL-SS-PCL-(PDMAEMA)4 to PCL-(PDMAEMA)4, while (PDMAPS)4-PCL-SS-PCL-(PDMAPS)4 changed into PCL-(PDMAPS)4. The distributions of Rh for both (PDMAEMA)4-PCL-SS-PCL-(PDMAEMA)4 and (PDMAPS)4-PCL-SS-PCL-(PDMAPS)4 assemblies broadened with asymmetric peaks, giving rise to curves with double peaks. After 24 h, DLS curves became symmetric with a single peak, and the Rh was about half that of the original assemblies. In the meantime, dispersed spherical micelles could be observed by TEM.

A brand new pH and thermo-responsive amphiphilic ABC triblock copolymer of poly(acrylic acid)-block-poly(N,N-dimethyl acrylamide)-block-poly(acrylamide-co-acrylonitrile) (PAA-b-PDMA-b-P(AM-co-AN)) was synthesized via sequential reversible addition–fragmentation chain transfer (RAFT) polymerization. Due to the pH-responsive blocks of PAA and thermo-responsive blocks of P(AM-co-AN), the properties of the copolymer solution were controlled by varying parameters such as temperature and pH. Specifically, it formed different nanostructures and showed gel behavior under different conditions. In detail, under high temperature alkaline conditions, ADAA was dissolved in an aqueous solution in the form of a molecular chain. Thereafter, when the temperature became lower or pH became acidic, the triblock copolymer self-assembled into different micelle structures, including shell–core, core–shell–core and tighter core–linking–core nanoparticles. In addition, the phase transition temperature of the copolymer was adjusted by pH and concentration. When the copolymer hydrogel was injected into a simulated human body device, it showed sustained drug release behavior and low transient drug concentrations. MTT experiments demonstrated the good biocompatibility of the ADAA hydrogels. This research provides inspiration to develop new polymers which are expected to be promising candidates as part of drug delivery platforms. Compared with traditional responsive hydrogels, its UCST can be easily controlled and is more stable through the feeding ratio, making it more advantageous in human drug delivery applications. In summary, we believe that this UCST and pH-responsive injectable ADAA hydrogel is researchable and applicable in the biomedical field.

Synthesis of polyampholytes based on cationic and anionic monomers that exhibit upper critical solution temperature (UCST) behavior is challenging as both the monomers need to be incorporated in stoichiometric amounts. By virtue of their charges, these polymers can exhibit special properties when both their ratios and/or the distance between the two charges are tuned. Here, the synthesis of alternating charge-neutral polyampholytes is described via reversible addition–fragmentation chain transfer (RAFT) statistical copolymerization of cationic styrenic and anionic N-substituted maleimide monomers. The percentage of N,N-dimethylaminomethylstyrene (DMAMSt) and N-carboxyethylmaleimide (CEMI) monomers in P(DMAMSt-alt-CEMI) copolymers is in 50/50 molar ratios, as confirmed by 1H NMR measurements during the polymerization of DMAMSt and tBuEMI monomers. The thermoresponsive UCST behavior of the obtained charge neutral polyampholytes is demonstrated in water and alcohol–water (methanol, ethanol and 2-propanol) solvent mixtures. Moreover, the effect of the charge neutral polyampholyte concentration on the UCST phase transition in ethanol/H2O solvent mixtures is discussed. The intermediate tert-butyl protected CEMI-based alternating copolymers P(DMAMSt-alt-tBuEMI) were found to be pH responsive and a diblock copolymer with a poly(N,N-isopropylacrylamide)block(PNIPAM-b-P(DMAMSt-alt-tBuEMI) demonstrated pH and LCST thermoresponsive behavior. These results demonstrate the use of these dual responsive polymers for future work on the exploration of these cationic and thermoresponsive polymers for the development of self-assembled responsive drug carriers.

In this work, in order to enhance the desalination performance, a unique thin-film composite membrane was designed by in situ assembly of a polyamide (PA)–graphene oxide quantum dot (GQD) framework. This unique assembly was supported on a templated hierarchical porous membrane derived from the de-mixing of a classical UCST (upper critical solution temperature) system consisting of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA). The de-mixing was achieved by melt processing the blend above the UCST (in the miscible state) and quenching it below UCST. The pore size was controlled by varying the composition in the blends and by etching the PMMA phase. A sandwich architecture was developed by stacking different membranes using polyacrylic acid, as an adhesive, to achieve a gradient in pore size. Pure water flux, dye removal, and desalination experiments were carried out to study the efficacy of this strategy. The stacked membrane (used here as control) showed moderate dye rejection (about 50%) and poor desalination performance. In order to improve the desalination performance, the membranes were suitably modified by depositing a layer of polyamide (PA)–GQD framework obtained using interfacial polymerization. This strategy resulted in efficient salt rejection (more than 94% and 98% for monovalent salt and divalent salt, respectively) when studied through a pressure enhanced osmosis process using a 1000 ppm draw solution, and dye rejection (more than 90% and 85% for methylene blue (MB) and Congo red (CR), respectively) was studied through a cross-flow experimental set up using a 10 ppm feed solution @ 60 psi. Moreover, the antifouling properties of the PA–GQD modified membranes were superior (80%) to those of the control stacked membrane.

Stimuli-responsive polymers with excellent biocompatibility and biodegradability are highly demanded as carriers for controlled drug delivery. Herein, a functional poly(e-caprolactone) (PCL) of poly(6-acetoxyl-e-caprolactone)-graft-(6-methyluracil) (PCCL-g-MU) was synthesized via post modification of poly(6-acetoxyl-e-caprolactone) (PCCL) with 6-(chloromethyl) uracil (MU). The incorporation of carboxyl and uracil groups endowed the PCL backbone with both pH and upper critical solution temperature (UCST) responsiveness. Benefiting from the structural similarity between MU and the anticancer drug 5-fluorouracil (5-FU), the self-assembled PCCL-g-MU nanoparticles resulted in a high 5-FU loading efficiency of 42%. Temperature-dependent release behavior of 5-FU loaded PCCL-g-MU nanoparticles was found to have originated from UCST transition. MTT assay against the L929 cell line revealed low cytotoxicity of PCCL-g-MU nanoparticles. The hydrolysis of the PCL backbone in either PBS or enzymatic solution indicated excellent biodegradability of PCCL-g-MU. It was demonstrated for the first time that biodegradable poly(e-caprolactone) with UCST behavior was developed, which is significant for enriching the thermo-responsive polymer library as well as biomedical applications.

Thermoresponsive gels of the upper critical solution temperature (UCST) type shrink below their critical temperature and swell above it. Changes in water uptake by these gels are driven by thermally induced dissociation of hydrogen or ionic bonds between chains. A simple model is developed for the description of the equilibrium swelling of thermophilic gels with hydrogen bonds. To confirm its ability to describe observations, equilibrium swelling diagrams are fitted on poly(acrylamide-acrylic acid) and poly(acrylamide-acrylonitrile) macroscopic gels and microgels with various structures (copolymer gels, gels with interpenetrating networks, nanocomposite gels), as well as on biocompatible poly(N-acryloyl-glycinamide) and poly(allylurea-co-allylamine) gels. Numerical simulation reveals that material parameters evolve consistently with molar fractions of crosslinker, hydrophobic and hydrophilic comonomers in the feed, degree of ionization of functional groups, and concentration of nanofiller. It is shown that the model can also be applied to describe observations on thermophilic zwitterionic gels.

A light-sensitive moiety, azobenzene, is incorporated into polyacrylamide (PAM) to yield copolymers with upper critical solution temperatures (UCST) in aqueous solutions. The thermoresponsiveness of the copolymers can be tuned not only by light irradiation, which causes the transition between the trans- and cis-forms of the azobenzene, but also by addition of α-cyclodextrin (α-CD), which preferentially complexes with the trans-form of azobenzene. The UCST transition is a combined effect of hydrogen bonding between the amide groups of the PAM chains and the hydrophobic interaction between azobenzene units, the latter of which can be influenced by the photoisomerization of azobenzene and the host–guest interaction between azobenzene and α-CD. The strategy of incorporating switchable hydrophobicity may inspire designs of UCST polymers, which may have potential applications as drug delivery devices and catalyst carriers.

The mutual solubility of epoxy oligomer with polysulfone (PSU) and polyethersulfone (PES) was studied by optical interferometry. Additionally, phase diagrams (PDs) were plotted and their evolution during the curing process was shown. The phase structures of modified hardened systems, as well as their tensile strengths, elastic moduli, and crack resistance, have been studied by scanning electron microscopy and physico-mechanical techniques. The effect of initial components&rsquo, mutual solubility on the phase structure and, subsequently, on the physico-mechanical properties of the composite material is shown. Differences in the structure and properties of the cured modified compositions depending on the type of PD (with Upper Critical Solution Temperature (UCST) for PSU and Lower Critical Solution Temperature (LCST) for PES) of the initial components are shown.

Developing smart temperature-sensitive hydrogels with a wide response range and highly stretchable and healable properties for simulation of the temperature perception function of human skin remains a great challenge. Here, a novel PNIPAm/PNAGA double-network hydrogel was developed by a self-assembly cross-linking strategy to achieve this goal. Benefiting from the double-network structure and a large number of multiple hydrogen bond interactions between the PNIPAm and PNAGA, the PNIPAm/PNAGA hydrogel realizes wide and adjustable dual temperature response behaviors of 0–32.5 °C (LCST) and 32.5–65 °C (UCST) and exhibits extraordinary mechanical properties with a maximum tensile strength of 51.48 kPa, elongation at break over 1400%, compressive stress over 1 MPa, and Young's modulus approximately 5.51 kPa, and excellent healable properties of nearly 100% temperature-sensitive repair rate. To the best of our knowledge, this is the highest mechanical strength of the reported PNIPNm-based dual temperature-sensitive hydrogels and simultaneously achieved the healable performance of dual temperature-sensitive hydrogels for the first time. The PNIPAm/PNAGA hydrogel displayed superior capability for simulation of the human skin to monitor various ambient temperatures, such as human skin temperature, hot and cold water, a refrigerator, room temperature and oven temperature, indicating promising applications in the fields of electronic skin, wearable device, bionics, etc.

The self-assembly of block copolymers constitutes a timely research area in polymer science with implications for applications like sensing or drug-delivery. In here, we investigate the unprecedented aggregation behaviour of high molecular weight block copolymer poly(N,N-diethylacrylamide)-b-poly(4-acryloylmorpholine) (PDEA-b-PAM) (Mn>400 kg/mol) in organic solvent tetrahydrofuran (THF). To elucidate the aggregation, dynamic light scattering, cryo transmission electron microscopy and turbidimetry were employed. The aggregate formation was assigned to the unprecedented upper critical solution temperature behaviour of PAM in THF at elevated concentration (> 6 wt%) and high molar masses. Various future directions for this new thermo-responsive block copolymer are envisioned, e.g. in the areas of photonics or templating of inorganic structures. This article is protected by copyright. All rights reserved

Liquid–liquid phase separation of binary systems for imidazolium-based ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cnmim][TFSI], where n represents the alkyl chain length of the cation), with 1,4-dioxane (1,4-DIO) was observed as a function of temperature and 1,4-DIO mole fraction, x1,4-DIO. The phase diagrams obtained for [Cnmim][TFSI]–1,4-DIO systems showed that the miscible region becomes wider with an increase in the alkyl chain length, n. For n = 6 and 8, an upper critical solution temperature (UCST) was found. To clarify the mechanism of the UCST-type phase separation, small-angle neutron scattering (SANS) experiments were conducted on the [C8mim][TFSI]–1,4-DIO-d8 system at several x1,4-DIO. The critical exponents of γ and ν determined from the SANS experiments showed that phase separation of the system at the UCST mole fraction occurs via the 3D-Ising mechanism, while that on both sides of UCST occurs via the mean field mechanism. Thus, the crossover of mechanism was observed for this system. The microscopic interactions among the cation, anion, and 1,4-DIO were elucidated using 1H and 13C NMR and IR spectroscopic techniques, together with the theoretical method of molecular dynamics (MD) simulations. The results on the microscopic interactions suggest that 1,4-DIO molecules cannot strongly interact with H atoms on the imidazolium ring, while they interact with the octyl chain of the cation through dispersion force. With a decrease in temperature, 1,4-DIO molecules gradually aggregate to form 1,4-DIO clusters in the binary solutions. The strengthening of the C–H⋯O interaction between 1,4-DIO molecules by cooling is the key to the phase separation. Of course, the electrostatic interaction between the cations and anions results in the formation of IL clusters. When IL clusters are excluded from 1,4-DIO clusters, liquid–liquid phase separation occurs. Accordingly, the balance between the electrostatic force between the cations and anions and the C–H⋯O interaction between the 1,4-DIO determines the 3D-Ising or the mean field mechanism of phase separation.

Indocyanine green (ICG) was incorporated into poly(ethylenimine)/(phenylthio) acetic acid (PEI/PTA) ion pair self-assembly (IPSAM) as a photosensitizer. PEI/PTA/ICG IPSAM was more stable against a thermal dissolution as the PTA and ICG content were higher. The zeta potential of the IPSAM without ICG (the amino group(A)/carboxyl group(C) molar ratio was 5.3:4.7) was a strong positive charge. Upon the addition of a small amount of ICG (A/C/ICG molar ratio was 5.3:4.7:0.01), it changed to a strong negative charge. The IPSAM on TEM micrographs was found as almost sphere-like nanoparticles and its diameter was around 50 nm. The doxorubicin-loaded IPSAM on CLSM micrographs was found as nano-sized circular red domains, indicating that the anti-cancer drug was successfully loaded in the IPSAM without disrupting the shape. When A to C molar ratio was 4:6, the ICG-incorporated IPSAM released its cargo appreciably under NIR irradiation even though the temperature of the IPSAM suspension could hardly reach the upper critical solution temperature (UCST) under NIR irradiation, suggesting that the release took place mainly by the radical oxygen species (ROS)-induced oxidation of PTA. When A to C molar ratio was 5.3:4.7, the temperature of the IPSAM suspension could reach the UCST under NIR irradiation and the release degree increased in proportion to the temperature increase, indicating the release took place mainly by the temperature change. According to the FT-IR spectroscopy, the NIR irradiation-triggered release could be attributed to the heat and ROS generated by ICG under NIR irradiation.

Photothermal therapy (PTT) has become effective method for the treatment of malignant cancer. The development of PTT system with high anti-tumour effect is still the feasible research direction. Here, a new type of gold nanorods (AuNRs)-doxorubicin (DOX)/mPEG10K-peptide/P(AAm-co-AN) (APP-DOX) nano drug delivery system was proposed. Among them, AuNRs was used as high-efficiency photothermal agent. APP-DOX had a suitable size and can be targeted to accumulate in tumour tissues through circulation in the body. The abundant matrix metalloproteinase 2 (MMP-2) in the tumour environment intercepted and cut off the short peptide chain structure grafted on APP-DOX. At the same time, the removal of the PEG segment leaded to an increase in the hydrophobic properties of the system. Nanoparticles aggregated into large particles, causing them to stay and aggregate further at the tumour site. When irradiated by 808 nm near-infrared laser, APP-DOX achieved a gradual heating process. High temperature can effectively ablate tumours and enable UCST polymer to achieve phase transition, resulting in more anti-cancer drugs loaded in the polymer layer DOX was released, effectively killing cancer cells. Animal experiments had verified the possibility of the nano drug-carrying system and good tumour treatment effect. What’s more worth mentioning is that compared with free DOX, the nano drug delivery system had lower biological toxicity and not cause obvious harmful effects on normal organs and tissues.

Gelatin is used widely in the biomedical field, among other for wound healing. Given its upper critical solution temperature, crosslinking is required. To this end, gelatin is chemically modified with different photo-crosslinkable moieties with low (32-34%) and high (63-65%) degree of substitution (DS): gelatin-methacrylamide (gel-MA) and gelatin-acrylamide (gel-AA) and gelatin-pentenamide (gel-PE). Next to the more researched gel-MA, it is especially interesting and novel to compare with other gelatin-derived compounds for the application of wound healing. An additional comparison is made with commercial dressings. The DS is directly proportional to the mechanical characteristics and inversely proportional to the swelling capacity. Gel-PE shows weaker mechanical properties (G' < 15 kPa) than gel-AA and gel-MA (G' < 39 and 45 kPa, respectively). All derivatives are predominantly elastic (recovery indices of 89-94%). Gel-AA and gel-MA show excellent biocompatibility, whereas gel-PE shows a significantly lower initial biocompatibility, evolving positively toward day 7. Overall, gel-MA shows to have the most potential to be applied as wound dressing. Future blending with gel-AA to improve the curing kinetics can lead to dressings able to compete with current commercial dressings.

Poly(2,2,2-trifluoroethyl methacrylate)-b-poly(imidazoled glycidyl methacrylate-co-diethylene glycol methyl ether methacrylate) (PTFEMA-b-P(iGMA-co-MEO2MA)) containing an upper critical solution temperature (UCST) polymer chain was prepared and blended with poly(vinylidene fluoride) (PVDF) to produce a thermoresponsive membrane with smart self-cleaning performance. The successful preparation of the membrane was demonstrated by attenuated total reflection-Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy characterization. The membrane shows UCST performance, and its flux changes with the filtrate temperature as the UCST polymer chain stretches out and contracts in response to various temperatures. In addition, the UCST polymer chain can disrupt the foulant and push it away from the membrane when the temperature is above the UCST and thus enables membranes to exhibit a smart self-cleaning behavior. To the best of our knowledge, this work is the first report of a smart self-cleaning membrane based on the blending of a diblock copolymer containing a UCST polymer chain with PVDF.

In this study, we carried out the synthesis of a thermo- and pH-sensitive binary graft, based on N-vinylcaprolactam (NVCL) and pH sensitive acrylic acid (AAc) monomers, onto chitosan gels (net-CS) by ionizing radiation. Pre-oxidative irradiation and direct methods were examined, and materials obtained were characterized by FTIR-ATR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and swelling tests (equilibrium swelling time, critical pH, and temperature). The best synthesis radiation method was the direct method, which resulted in the maximum grafting percentages (~40%) at low doses (10–12 kGy). The main goal of this study was the comparison of the swelling behavior and physicochemical properties of net-CS with those of the binary system (net-CS)-g-NVCL/AAc with the optimum grafting percentage (~30%). This produced a material that showed an upper critical solution temperature (UCST) of 33.5 °C and a critical pH value of 3.8, indicating the system is more hydrophilic at higher temperatures and low pH values. Load and release studies were carried out using diclofenac. The grafted system (32%) was able to load 19.3 mg g−1 of diclofenac and release about 95% within 200 min, in comparison to net-CS, which only released 80% during the same period. When the grafted system was protonated before diclofenac loading, it loaded 27.6 mg g−1. However, the drug was strongly retained in the material by electrostatic interactions and only released about 20%.

The solubility and interdiffusion of polystyrene (PS) with polymethyl acrylate (PMA), polyethyl acrylate (PEA), polybutyl acrylate (PBA), and polyethylhexyl acrylate (PEHA) have been studied by the optical interferometry method. Phase state diagrams are plotted. It is shown that they are characterized by the upper critical solution temperatures (UCST), which are localized in the temperature range above 450 K. Pair interaction parameters and their temperature dependences are determined and analyzed. Extrapolation of the temperature dependence of the interaction parameter was used to construct the dome of binodal curves and determine the spinodal curves in the framework of the Flory–Huggins theory. The diffusion coefficients of polystyrene into polyacrylates and polyacrylates into polystyrene are calculated. The dependences of the interdiffusion coefficients on the concentration, temperature, polystyrene molecular weight, and the number of carbons in the side chain of polyacrylate are analyzed. The numerical values of the interdiffusion coefficients of PS-1 into polyacrylates at 433 K change as −8.5 → −6.7 → −6.4 in the homologous series PMA → PEA → PBA. The coefficients of friction are calculated and the effect of change in the matrix structure on the diffusion of polystyrene in them is estimated.

Vinyl polymers are the focus of intensive research due to their ease of synthesis and the possibility of making well-defined, functional materials. However, their non-degradability leads to environmental problems and limits their use in biomedical applications, allowing aliphatic polyesters to still be considered as the gold standards. Radical ring-opening polymerization (rROP) of cyclic ketene acetals (CKAs) is considered the most promising approach to impart degradability to vinyl polymers. Despite considerable efforts, rROP-synthesized materials still exhibit poor hydrolytic degradation and thus cannot yet compete with traditional polyesters. Here we show that a simple copolymerization system based on acrylamide and CKA can lead to well-defined copolymers with faster hydrolytic degradation than that of polylactide and poly(lactide-co-glycolide). Moreover, by changing the nature of the CKA, the copolymers were either water-soluble or exhibited tunable upper critical solution temperatures (UCST) relevant for mild hyperthermia-triggered drug release. To illustrate the interest of these new copolymers, we showed that they were cytocompatible on different healthy cell lines and we synthesized amphiphilic diblock copolymers that were formulated into degradable, UCST nanoparticles by an all-water nanoprecipitation process. Given all its important benefits, we anticipate this copolymerization system to offer new avenues in different applications such as biodegradation of commodity polymers, drug delivery or tissue engineering.

Owing to their tunable properties, hydrogels comprised of stimuli-sensitive polymers are one of the most appealing scaffolds with applications in tissue engineering, drug delivery and other biomedical fields. We previously reported a thermoresponsive hydrogel formed using a coiled-coil protein, Q. Here, we expand our studies to identify the gelation of Q protein at distinct pH conditions, creating a protein hydrogel system that is sensitive to temperature and pH. Through secondary structure analysis, transmission electron microscopy, and rheology, we observed that Q self-assembles and forms fiber-based hydrogels exhibiting upper critical solution temperature behavior with increased elastic properties at pH 7.4 and pH 10. At pH 6, however, Q forms polydisperse nanoparticles, which do not further self-assemble and undergo gelation. The high net positive charge of Q at pH 6 creates significant electrostatic repulsion, preventing its gelation. This study will potentially guide the development of novel scaffolds and functional biomaterials that are sensitive towards biologically relevant stimuli.

Three novel ionic liquids were synthesized. Their binary mixtures with water exhibit tunable thermomorphic behaviors involving monophasic–biphasic transition. Through electrostatic potential maps, ...

Self-complementary supramolecular polymers (SCSPs), an efficient combination of sextuple hydrogen-bonded dimer moieties and a temperature-responsive polymer, can promote the construction of stable supramolecular polymer networks (SPNs) that enable the formation of well-defined nanospherical micelles in aliphatic alcohols. These micelles undergo tailorable, thermoresponsive phase transitions at the upper critical solution temperature (UCST) and have a desirable spherical morphology and size ranges, thus, are potential candidates for applications in interfacial engineering and biomedical fields. Moreover, concentration-dependent UCST measurements and variable-temperature experiments indicated that the hydrogen-bonded complexes are strong enough to form stable intermolecularly entangled SPNs within the micelles, even above the UCST or at low concentrations in solution, which enables the micelles to undergo reversible temperature-dependent conformational changes between insoluble and soluble globules without significant changes in particle size or size distribution. Thus, this newly discovered system offers a new approach toward the development of next-generation temperature-responsive SCSPs with the desired structural stability that undergoes UCST transitions.

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. H...

Thermoresponsive hydrogel actuators have attracted tremendous interest due to their promising applications in artificial muscles, soft robotics, and flexible electronics. However, most of these materials are based on polymers with lower critical solution temperature (LCST), while those from upper critical solution temperature (UCST) are rare. Herein, we report a multiple-responsive UCST hydrogel actuator based on the complex of poly(acrylic acid) (PAAc) and poly(acrylamide) (PAAm). By applying a heterogeneous photopolymerization, a bilayer hydrogel was obtained, including a layer of the interpenetrating network (IPN) of PAAm/PAAc and a layer of a single network of PAAm. When cooled down below the UCST, the PAAm/PAAc layer contracted due to the hydrogen bonding of the two polymers while the PAAm layer stays in swelling state, driving the hydrogel to curl. By adjusting the composition of the two layers, the amplitude of actuation behavior could be regulated. By creating patterned IPN domains with photomasks, the hydrogel could deform into complex two-dimensional (2D) and three-dimensional (3D) shapes. An active motion was realized in both water and oil bath, thanks to the internal water exchange between the two layers. Interestingly, the hydrogel actuator is also responsive to urea and salts (Na2SO4, NaCl, NaSCN), due to that the strength of the hydrogen bonds in the IPN changes with the additives. Overall, the current study realized an anisotropic UCST transition by introducing asymmetrically distributed polymer-polymer hydrogen bonds, which would inspire new inventions of intelligent materials.

The wide range of applications of poly(N-isopropylacrylamide) (PNIPAM) is based on the temperature dependence of its coil-to-globule transition, which strongly relies on the solvent. Here, we focus...

We investigated the thermoresponsive behavior of poly(acrylamide-co-acrylonitrile) (poly(AAm-co-AN)) with an upper critical solution temperature (UCST) in water to apply this polymer in cosmetic pr...

Multi‐l‐arginyl‐poly‐l‐aspartic acid (MAPA), also known as cyanophycin, can incorporate lysine into the side‐chain position of arginine when being prepared with recombinant Escherichia coli. The soluble fraction (sMAPA) is known to display both lower critical solution temperature (LCST) and upper critical solution temperature (UCST) responses at the physiological condition. In an attempt to alter the UCST thermal response, maltodextrin was employed to conjugate onto the amine group of lysine of sMAPA via the formation of Schiff base. In phosphate buffered saline, the UCST of the conjugates appeared around 50–62°C, depending on the extent of conjugation. In contrast to the unmodified sMAPA, the UCST of the conjugate became independent of pH ranging from 1 to 11. Heating the conjugate solution to complete transparent caused a delayed and partial recovery of the original turbidity during subsequent cooling. However, the turbidity can be restored by further precipitation with ethanol or isopropanol followed lyophilization and re‐dissolution. At room temperature, below UCST, the agglomerates exhibited a size of around 200–400 nm under TEM and DLS. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2048–2055

The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (salicylaldehyde, SAC) + CH3(CH2)nCH3 mixtures (n = 5,6,7,8,9). The equilibrium temperatures were determined observing, by means of a laser scattering technique, the turbidity produced on cooling when a second phase takes place. All the systems show an upper critical solution temperature, which linearly increases with n. Intermolecular effects have been investigated in alkanol + benzaldehyde systems using data from the literature. Interactions in 1-alkanol mixtures are mainly of dipolar type. The corresponding excess molar enthalpies, H m E , are large and positive, which reveals that interactions between like molecules are dominant. Interactions between unlike molecules are stronger for the methanol-containing system. For the other mixtures, the enthalpy of the 1-alkanol-benzaldehyde interactions remains more or less constant. At 298.15 K and equimolar composition, the replacement of a linear polar solvent by the isomeric aromatic one leads to increased H m E values in systems with a given 1-alkanol. The phenol + benzaldehyde system shows strongly negative deviations from the Raoult’s law. Proximity effects have been examined in SAC + hydrocarbon mixtures. Alkane-containing systems are essentially characterized by dipolar interactions, while dispersive interactions are prevalent in the solution with benzene. All the mixtures have been treated in terms of DISQUAC. The interaction parameters for the OH/CHO contacts and for the SAC/aromatic and SAC/alkane contacts have been reported. DISQUAC provides a correct description of the thermodynamic properties considered. In the case of SAC systems, this is done by defining a new specific group HO–C–C–CHO for salicylaldehyde.

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, T(ph), 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, T(meta), 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, T(gel), the proteins assemble into a kinetically trapped gel state that arrests ATPS formation. The kinetics of ATPS formation near T(gel) 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.

Zwitterionic sulfobetaine-containing diblock copolymer, poly(ethylene glycol)methyl ether-block-poly[3-dimethyl(methacryloyloxy ethyl)ammonium propane sulfonate] (MPEG-b-PSBMA), was successfully synthesized and utilized as a stabilizer to prepare mono- and bimetallic nanoparticles. Precursor poly(ethylene glycol)methyl ether-block-poly[2-(N-dimethylamino)ethyl methacrylate] (MPEG-b-PDMA) diblock copolymer was first synthesized via atom transfer radical polymerization. PDMA blocks were reacted with 1,3-propanesultone to obtain MPEG-b-PSBMA diblock copolymer. Spherical monometallic gold (Au), platinum (Pt) and bimetallic alloy gold/platinum (Au/Pt), gold/silver (Au/Ag), and silver/platinum (Ag/Pt) nanoparticles (with a diameter below 8.0 nm) were synthesized in aqueous media via sonochemical method using diblock copolymer as stabilizer. The zwitterionic sulfobetaine block copolymer provided thermodynamic (5 days at 65 °C) and kinetic (1 year at 25 °C) stability to the synthesized NPs without aggregation. Zwitterionic PSBMA blocks of MPEG-b-PSBMA diblock copolymer showed an upper critical solution temperature (UCST) in aqueous media. This thermo-responsive block copolymer provided better stabilization to metal NPs as compared with MPEG and PSBMA homopolymers. The structures of bi- and monometallic NP dispersions were characterized by measuring surface plasmon resonance and transmission electron microscopy. The prepared metal NP/polymer dispersions showed good catalytic activities (Ag/Pt > Au/Ag > Au > Au/Pt > Pt) in the reduction of p-nitrophenol to p-aminophenol.

A novel switchable luminescent thermometer based on thermo-responsive triblock copolymer poly(ethylene glycol)-b-poly(acrylamide-co-acrylonitrile-co-dimethylaminoethylmethacrylate) (PEO113-b-P(AAm264-co-AN112-co-DMA8)) and Eu-containing polyoxometalate (Eu-POM) was successfully constructed. The copolymer synthesized by RAFT exhibited a linear response to temperature variations in aqueous media, which was quite different from the uncharged copolymer P(AAm-co-AN) having a specific upper critical solution temperature (UCST). Eu-POM was surrounded around thermo-responsive blocks through electrostatic interactions, and its luminescence could be finely tuned due to the sensitivity of copolymer to the temperature variation. In cold water, POMs were trapped in highly hydrophobic cores, exhibiting an intense emission. With the upraising of temperature, the emission intensity presented a gradual decrease and showed a linear correlation with temperature. When the complex solution cooled down, the luminescence could also be perfectly restored. This temperature-luminescence correlation could be held for numerous trials, showing a potential application in thermometer.

Poly(acrylic acid) is water soluble but can be converted into a thermoresponsive polymer possessing an upper critical solution temperature (UCST) by copolymerizing with acrylonitrile. The copolymer...

A series of ABA-type triblock copolymers (PImBF4-b-PPG-b-PImBF4) comprising of poly(propylene glycol) (PPG) as middle block and UCST polypeptide on both sides of PPG was synthesized by ring-opening polymerization of γ-chloropropyl-L-glutamic acid-based N-carboxyanhydride (CPLG-NCA) and then side-chain modification including nucleophilic substitution of the chloro group followed by copper-mediated 1,3-dipolar cycloaddition and subsequent ion-exchange reaction. Variable-temperature UV–vis spectroscopy revealed that the upper critical solution temperature (UCST)-type cloud point temperature (Tcp) was highly dependent on both polypeptide and PPG chain length as well as polymer concentration. Increasing the polymer chain length or concentration frequently results in Tcp increases. Noticeable hysteresis in a cooling/heating cycle was observed for all resulting triblock copolymers owing to a slow disassembly of large aggregates (d = 145 nm) in the heating cycle. Moreover, the resulting UCST triblock copolymers were used to regulate the release property of ciprofloxacin (CIP)-loaded poly(vinyl alcohol) (PVA) hydrogel. The incorporation of PImBF4-b-PPG-b-PImBF4 hampered the burst release of CIP at 37 °C indicating their potential toward sustained release of drug-loaded hydrogels.

Thermo, pH, and photo triple-responsive hollow nanospheres self-assembled from amphiphilic random copolymer poly (styrene-stat-4-vinylpyridine) (PS-stat-P4VP) and azobenzene (AZO) 4-phenylazophenol have been investigated by means of TEM, SEM, FTIR, DLS and UV–vis spectrophotometry. Controlling over the ratio of PS-stat-P4VP and AZO can realize different size of hollow nanospheres. PS-stat-P4VP/AZO hollow nanospheres display UCST behavior and perform well reversible self-assembly and disassembly property between 25 °C and 45 °C as well as pH = 2.7 and pH = 8.1. Besides, the hollow nanospheres can be significantly elongated along the polarization direction of the polarizer, showing well photo-responsive performance. With the UCST of about 37 °C and pH responsive range close to human body, those PS-stat-P4VP/AZO hollow nanospheres demonstrate great potential in medicine and physiology.

Premature and incomplete drug release is the typical bottleneck of drug release in traditional chemotherapy. Synergistic therapies are highly desirable in medicine and biology because they can compensate for the drawbacks of single therapy and significantly enhance the therapeutic efficacy. Herein, a novel near infrared (NIR)-activated polymeric nanoplatform with upper critical solution temperature (UCST) was constructed for image-guided synergistic photothermal therapy (PTT) and chemotherapy. UCST-responsive amphiphilic block copolymers were synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization and then co-assembled with IR780 and cabazitaxel (Cab) to form spherical nanoparticles (NPs). IR780/Cab dual-loaded UCST polymeric NPs can produce local heating upon NIR laser irradiation and further lead to the dissociation of cargo-loaded NPs and controlled release of Cab. IR780 plays the role of both a heating generator and an activator for "on-demand" drug release. The investigation of in vivo fluorescence and photothermal imaging clearly demonstrated tumor targeting. Notably, both in vitro and in vivo studies illustrated that the synergistic PTT and chemotherapy presented better anticancer efficacy than that of PTT and chemotherapy simplely combined. Thus, the well-defined polymeric nanoplatform opens a versatile and effective path to develop image-guided synergistic therapies for tumor treatment.

This study compares the predictions of CP-PC-SAFT and SAFT-VR-Mie for binary systems of aliphatic hydrocarbons and the C3-C5 1-alkanols. Systems of carbon monoxide and hydrogen sulfide are considered as well. In all the cases zero values of the binary adjustable parameters have been implemented. Thanks to the superior flexibility achieved by fitting 6 pure compound parameters, SAFT-VR-Mie excellently represent various thermodynamic properties of the considered 1-alkanols. Since CP-PC-SAFT fits these data with only 2 adjustable parameters, its pertinent performance is less accurate, but remains reasonable good. At the same time, unlike SAFT-VR-Mie, CP-PC-SAFT rigorously obeys of the pure compound Tc and Pc, which allows accurate predictions of critical loci and VLE in the symmetric systems. Moreover, in exception of LLE in the systems of ethane and ethene, CP-PC-SAFT truthfully predicts critical data and the high pressure VLE in the asymmetric systems. SAFT-VR-Mie estimates these data in a less accurate manner, excepting the VLE of the C4-isomers and n-pentane systems. It the latter cases the results of both models are comparable. At the same time, SAFT-VR-Mie often yields more accurate results for the low-pressure VLE. Besides that, the predictions of CP-PC-SAFT for LLE in 1-alkanol – [C1MIM][NTF2] and – [C2MIM][NTF2] ionic liquid systems are presented. Despite the simplified approach to ILs, this model truthfully predicts the UCST data in 1-alkanol – [C1MIM][NTF2] and – [C2MIM][NTF2] systems, overestimating however the concentrations of ILs in both equilibria phases.

Bio-based products and processes were favored recently, because shifting towards a more sustainable economy might be a long-term solution for global challenges. Within this context, γ-valerolactone emerges as a sustainable alternative for industrially relevant solvents and as a potential additive for liquid fuels. Yet, few data have been published regarding the solubility behavior of binary mixtures containing this molecule, which is crucial for assessing its possible applications. Hence, this work determined the mutual solubility of γ-valerolactone and n-tetradecane, a representative molecule of diesel, using the cloud point method at temperatures between 288.15 K and 333.15 K, which guarantees compounds stability. This method was also employed to determine the lactone solubility in commercial diesel at selected temperatures. Results were correlated by the NRTL and UNIQUAC models, which succeeded in representing experimental data but could not predict the upper critical solution temperature.

In this work, the mixing of a hydrocarbon droplet in near- and super-critical water (NCW/SCW) is mathematically modeled, coupling thermodynamic properties calculation with transport processes. In non-ideal systems, mass transfer is captured using the generalized Maxwell-Stefan equations with the driving force expressed in terms of the fugacity gradients. The GCA-EOS is used to predict the thermodynamic properties and phase equilibrium compositions. We select n-decane, n-triacontane, benzene, naphthalene and 1-decylnaphthalene as representative hydrocarbons. Our simulations show delayed mixing processes as the temperature approaches the upper critical solution temperature (UCST) of the mixture, consistent with the impact of non-ideal diffusional driving forces evaluated from pure thermodynamic calculations. Results also show that the phase behavior notably affects the non-ideal driving forces near the UCST, which confirms the importance of coupling accurate thermodynamic models in predictive mixing studies. Fil: Sánchez, Francisco Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina Fil: He, Ping. Lamar University; Estados Unidos. Massachusetts Institute of Technology; Estados Unidos Fil: Ghoniem, Ahmed F.. Massachusetts Institute of Technology; Estados Unidos Fil: Pereda, Selva. University of KwaZulu-Natal; Sudáfrica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina

Novel multiresponsive hybrid biocompatible systems of κ-carrageenan-graft-poly(2-isopropyl-2-oxazoline-co-2-butyl-2-oxazoline)s with unique combination of responsiveness to external stimuli were synthesized and studied. The polymer thermoresponsive behavior proved the existence of both lower and upper critical solution temperatures in aqueous milieu, forming gel at lower temperature, a solution at room temperature and cloudy nanophase-separated dispersion at elevated temperature. The limit temperatures can easily be adjusted by the polyoxazoline graft length and grafting density. Moreover, the polymer behavior is additionally dependent on the concentration of potassium ions. The polymers behave similarly as the original κ-carrageenan, and thus, the poly(2-alkyl-2-oxazoline) grafts do not decrease the ability of the κ-carrageenan to form the self-assembled structures. Molecular principles beyond this multistimuli-responsive behavior were elucidated with the use of dynamic light scattering, magnetic resonance and fluorescence measurements as well as atomic force microscopy. These polymers could be used in a wide range of biological applications demanding thermo- and potassium-responsiveness.