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Sorption‐based atmospheric water harvesting (SAWH) has great potential for clean water acquisition and renewable energy use. Adsorption and desorption properties of sorbents play a crucial role in SAWH systems. However, most sorbents with high adsorption capacities are hindered by either slow sorption/desorption kinetics or poor regeneration performance. Here, a highly efficient block copolymer composite sorbent with dual functions of thermo‐responsive and photothermal properties is designed based on rape pollens. This sorbent has a hierarchical porous structure, in which the outermost layer of poly‐pyrrole enables it to convert light energy into heat and the second layer of poly(N‐isopropylacrylamide) imparts thermo‐responsive properties to improve the desorption ability. Meanwhile, confined LiCl improves its sorption capacity and cavities of the pollen can store captured moisture to avoid liquid leakage. This sorbent can sorb moisture to more than 144% of its own weight within 3 h under 20 °C&80% relative humidity (RH) and 82% of captured water can be released within 0.5 h under 1 sun. The water harvester using this sorbent can realize an exceptional water productivity of up to 2.21gwater gsorbent−1 day−1 only by three continuous water adsorption‐desorption cycles in a day. The high‐performance sorbent smooths the path for efficiently extracting water from the atmosphere to tackle water scarcity. [ABSTRACT FROM AUTHOR]

Smart microgels can be used as sorbents, possessing high surface area and rapid stimuli‐responsiveness. A series of poly(N‐isopropylacrylamide) (pNIPAM) and pNIPAM‐co‐starch nanoparticles (pNIPAM‐co‐SNPs) thermo‐responsive microgels were synthesized, presenting different hydrophilic/hydrophobic behavior according to the composition. The adsorption studies were carried out for methylparaben (MPB), ethylparaben (EPB), propylparaben (PPB), butylparaben (BPB), and bisphenol A (BPA), and the extraction and desorption efficiency were determined by high‐performance liquid chromatography and spectrophotometric detection (HPLC‐UV). The effect of microgel phase transition according to the temperature and the copolymerization with SNPs in each sorptive step was investigated. The extraction of less polar compounds (BPA, PPB, and BPB) above the volume phase transition temperature (VPTT) was favored, driven by a predominant hydrophobic interaction. According to microgel composition, the desorption capacity as a function of temperature can be influenced by hydrophilic interactions and water competition. Molecular dynamics (MD) simulations and binding free energy calculations were performed to provide theoretical evidence about binding energies between pNIPAM and BPA, which experimentally showed the best extraction efficiency results. These findings may provide a strategy for designing high‐performance sorptive phases that could remove hydrophilic and hydrophobic compounds from water and a hypothesis about the driving forces of such processes. [ABSTRACT FROM AUTHOR]

Materials with ultra‐fast responsive properties are essential for various applications. Among the responsive materials, poly(N‐isopropylacrylamide) (PNIPAM) stands out due to its well‐studied temperature‐responsive properties. Improving the kinetics of the responsive properties of PNIPAM is, however, still essential for advancing its practical use. Here, the responsive rate of PNIPAM hydrogels is enhanced by first incorporating sub‐micrometer porosity into the material through polymerization‐induced phase separation (PIPS), followed by introducing millimeter scale pores via 3D printing, thereby rendering the material with hierarchical porosity. The 3D‐printed porous PNIPAM structures show accelerated swelling and deswelling, when compared to non‐porous PNIPAM structures, due to enhanced water permeability associated with the continuous network of micrometer to millimeter‐sized pores. Additionally, thinner polymer structures result in faster temperature response rates. At the same time, the mechanical strength of PNIPAM hydrogels with high porosity and thinner polymer walls is not compromised, overcoming the common trade‐off between swelling and mechanical properties. [ABSTRACT FROM AUTHOR]

Förster resonance energy transfer (FRET) is ubiquitous in optical processes in the natural world. A methodology is proposed that uses an optical force to control its efficiency without contact in an aqueous solution of a thermo‐responsive polymer, polyvinyl methyl ether (PVME). Focusing irradiation of a near infrared laser beam into the solution results in the formation and trapping of a single polymer droplet. The polymer concentration in the droplet is controllable by changing the optical force from the laser light is shown. The polarity inside the droplet decreases with increasing the optical force. When small amounts of dye molecules, D (energy donor) and A (energy accepter), are dissolved in the polymer solution, D and A are absorbed (extracted) into the droplet. The concentrations of D and A are controllable by the optical force. Based on this mechanism, FRET between D and A is induced successfully, and can control the FRET efficiency. Finally, the modulation of fluorescence color of the droplet from blue, green, yellow, to an orange color is demosntrated simply by changing the optical force. The concept and technique are unique and will open a new channel to develop droplet chemistry and photochemistry. [ABSTRACT FROM AUTHOR]

A temperature‐responsive surface‐enhanced Raman scattering (SERS) substrate with "ON–OFF" switching based on poly(ionic liquid)s (PILs) block copolymer microgels have been designed and synthesized. The PIL units act as a joint component to anchor the gold nanoparticles (AuNPs) and analytes onto poly(N‐isopropylacrylamide) (PNIPAm). This anchor allows the analytes to be fixed at the formed hot spots under temperature stimulus. Owing to the regulation of the PNIPAm segment, the SERS substrates exhibit excellent thermally responsive SERS activity with a reversible "ON–OFF" effect. Additionally, because of the anion exchange of PILs, microgels can introduce new analytes, which offers more flexibility for the system. The substrate shows excellent reversibility, controllability, and flexibility of SERS activity, which is expected to have a broad application in the field of practical SERS sensors. [ABSTRACT FROM AUTHOR]

Smart hydrogels responsive to external stimuli are promising for various applications such as soft robotics and smart devices. High mechanical strength and fast response rate are particularly important for the construction of hydrogel actuators. Herein, tough hydrogels with rapid response rates are synthesized using vinyl‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) microgels as macro‐crosslinkers and N‐isopropylacrylamide as monomers. The compression strength of the obtained PNIPAM hydrogels is up to 7.13 MPa. The response rate of the microgel‐crosslinked hydrogels is significantly enhanced compared with conventional chemically crosslinked PNIPAM hydrogels. The mechanical strength and response rate of hydrogels can be adjusted by varying the proportion of monomers and crosslinkers. The lower critical solution temperature (LCST) of the PNIPAM hydrogels could be tuned by copolymerizing with ionic monomer sodium methacrylate. Thermo‐responsive bilayer hydrogels are fabricated using PINPAM hydrogels with different LCSTs via a layer‐by‐layer method. The thermo‐responsive fast swelling and shrinking properties of the two layers endow the bilayer hydrogel with anisotropic structures and asymmetric response characteristics, allowing the hydrogel to respond rapidly. The bilayer hydrogels are fabricated into clamps to grab small objects and flowers that mimicked the closure of petals, and it shows great application prospects in the field of actuators. [ABSTRACT FROM AUTHOR]

The potential of photoactive Prussian blue nanoparticles dispersed in thermo‐responsive PNIPAM hydrogels in 4D printing using a stereolithography is investigated with digital light processing. The proportion of Prussian blue nanoparticles used in the resin is chosen to deliver a significant photothermal effect providing a heating above the volume phase transition temperature of the final nanocomposite hydrogels; while, giving only a limited effect on light scattering during the 3D printing process. Four formulations with various amounts of Prussian blue nanoparticles are used to print 3D structures with different shapes, such as Aztec pyramids, cylinders, gyroid porous cubes, and porous films. The shrinkage effect triggered by light irradiation at 808 nm on the as‐obtained nanocomposite hydrogels is demonstrated through the delivery of a representative molecule fluorescein and a triggered 4D shape‐morphing effect. [ABSTRACT FROM AUTHOR]

Temperature is a widely incorporated stimulus in pharmaceutical applications because of its efficiency as a therapeutic medium; thus, substantial evidence on temperature‐responsive polymer applications is reported. Poly(N‐isopropylacrylamide) (PNIPAAm) is a well‐established, temperature‐responsive polymer that exhibits a low critical solution temperature (LCST) at ≈ 32°C, which is close to physiological temperature. Hence, they are widely used in various pharmaceutical applications, such as drug delivery with nanocarriers and thermogels. Varying the LCST for different applications can be achieved by copolymerization with other hydrophobic or hydrophilic molecules, making it a favorable smart polymer. PNIPAAm is reported to enhance drug delivery by incorporation with nanocarriers and to facilitate prolonged drug delivery, thereby avoiding the burst release of drugs in temperature‐responsive hydrogels. The application of PNIPAAm is not limited to drug delivery, and it is also applied in biomedical applications such as chromatography systems and cell culture applications, where its incorporation in cell culture media enhances cell production. The unique and versatile properties of PNIPAAm render it a promising smart polymer for various functional applications. Hence, this review focuses on the diverse applications of PNIPAAm. [ABSTRACT FROM AUTHOR]

Over the past few decades, stimuli‐responsive materials have been widely applied to porous surfaces. Permeability and conductivity control of ions confined in nanochannels modified with stimuli‐responsive materials, however, have been less investigated. In this work, the permeability and conductivity control of ions confined in nanochannels of anodic aluminum oxide (AAO) templates modified with thermo‐responsive poly(N‐isopropylacrylamide) (PNIPAM) brushes are demonstrated. By surface‐initiated atom transfer radical polymerization (SI‐ATRP), PNIPAM brushes are successfully grafted onto the hexagonally packed cylindrical nanopores of AAO templates. The surface hydrophilicities of the membranes can be reversibly altered because of the lower critical solution temperature (LCST) behavior of the PNIPAM polymer brushes. From electrochemical impedance spectroscopy (EIS) analysis, the temperature‐gating behaviors of the AAO‐g‐PNIPAM membranes exhibit larger impedance changes than those of the pure AAO membranes at higher temperatures because of the aggregation of the grafted PNIPAM chains. The reversible surface properties caused by the extended and collapsed states of the polymer chains are also demonstrated by dye release tests. The smart thermo‐gated and ion‐controlled nanoporous membranes are suitable for future smart membrane applications. [ABSTRACT FROM AUTHOR]

Temperature‐sensitive (thermosensitive) hydrogels, which are part of the family of stimulus‐sensitive hydrogels, consist of water‐filled polymer networks that display a temperature‐dependent degree of swelling. Thermosensitive hydrogels, which can undergo phase transition or swell/de‐swell as temperature changes, have great potential in various technological and biomedical purposes for a number of reasons: their temperature response is reversible, hydrogels are stable and easy to prepare, they can be biocompatible and also be suitably combined with other organic and inorganic materials, resulting in new materials with outstanding properties. Among thermosensitive hydrogels poly(N‐isopropylacrylamide) (PNIPAAm) is the most extensively studied because it brings together the best properties of these materials. Consequently, in the past few years, a wide number of applications and new chemical processes to prepare PNIPAAm and their derivatives are being proposed. The objective of this review is to summarize the fundamentals of thermosensitive hydrogels and recent advances in preparation and both technological and biomedical applications of thermosensitive hydrogel, with a special focus on PNIPAAm and their derivatives. Special attention has been given to the discussion of challenges and future research perspectives based on new horizons not yet considered. [ABSTRACT FROM AUTHOR]

This work describes the empirical screening of base types and amounts on the catalytic property of gold‐polymer composite particles in the aerobic homocoupling of arylboronic acid. As these particles notably improve the yields of biaryl in the presence of bases, various bases and their amounts are systematically tested to experimentally identify an ideal base that can provide high reactivity and recyclability of the composite particles in mild and green conditions. Interestingly, the following conditions ‐ soluble strong bases at sub‐stoichiometric quantities (0.5 eq.) and insoluble weak bases at excess amounts (3.0 eq.) in EtOH ‐ significantly enhance the catalytic activities of the composite particles. Upon screening two ideal bases, overall catalytic properties of the composite particles including reaction rate at three different temperatures, activation energy (51–52 kJ/mole), and recyclability (7 cycles) were compared. Understanding the effect of bases and fine‐tuning reaction conditions can potentially improve overall reactivity and recyclability of the composite particles as a green quasi‐homogenous catalyst. [ABSTRACT FROM AUTHOR]

Poly(N‐isopropylacrylamide) is a thermosensitive polymer which undergoes coil to globule transition in which chains collapse and aggregate when passing to and above lower critical solution temperature (LCST). This property of the polymer is due to its unique structure. The synthesis of thermosensitive polymer Poly(N‐isopropylacrylamide) by novel and eco‐friendly routes has been reported in this work. The synthetic routes adapted are microwave method and a nonlinear chemical oscillator. In both of these methods, chemistry of polymerisation takes place in a single pot involving less toxic end products. To evolve a comparative trend conventional method was also used as a standard. Based on this, the mechanism for the synthesis of thermosensitive polymer was also proposed. It is found that the above mentioned nonconventional methods of synthesis have advantages over the conventional method in terms of the time of reaction and yield. The polymers synthesized by different routes were then characterised by different techniques which confirmed their thermosensitive behaviour and other properties. [ABSTRACT FROM AUTHOR]

A series of poly(N‐isopropylacrylamide) (PNIPAm) homopolymers with narrow molecular weight distributions (MWDs) is prepared via photoinduced electron/energy transfer–reversible addition‐fragmentation chain transfer (PET–RAFT) polymerization. The thermal transition temperature of these polymer samples is analyzed via turbidity measurements in water/N,N'‐dimethylformamide mixtures, which show that the cloud point temperatures are inversely proportional to the weight average molecular weight (Mw). Binary mixtures of the narrowly distributed PNIPAm samples are also prepared and the statistical parameters for the MWDs of these blends are determined. Very interestingly, for binary blends of the PNIPAm samples, the thermoresponsive transition is not only dependent on the Mw, which has been shown previously, but also on higher order statistical parameters of the MWDs. Specifically, at very high values of skewness and kurtosis, the polymer blends deviate from a single sharp thermoresponsive transition toward a broader thermal response, and eventually to a regime of two more distinct transitions. This work highlights the importance of in‐depth characterization of polymer MWDs for thermoresponsive polymers. [ABSTRACT FROM AUTHOR]

Poly(N‐isopropylacrylamide) (PNIPAM) is an important thermo‐responsive polymer that finds applications in many areas. However, the preparation of PNIPAM‐based block copolymer nanoparticles with higher‐order morphologies at high solids is challenging. Herein, aqueous photoinitiated polymerization‐induced self‐assembly (photo‐PISA) of N‐isopropylacrylamide (NIPAM) using an asymmetrical cross‐linker is developed for one‐step preparation of PNIPAM‐based block copolymer nanoparticles with various morphologies (spheres, worms, and vesicles). It is demonstrated that reaction temperature has a great effect on both polymerization kinetics and morphologies of block copolymer nanoparticles. Reversible addition‐fragmentation chain transfer (RAFT) reactive groups embedded inside the PNIPAM core provide a landscape for further functionalization. PNIPAM‐based block copolymer nanoparticles with different surface properties are prepared by seeded photo‐PISA at room temperature. Finally, these block copolymer nanoparticles are also used as additives to tune mechanical properties of hydrogels via covalent cross‐linking. [ABSTRACT FROM AUTHOR]

Poly(N‐isopropylacrylamide) (PNIPAM) having lower critical solution temperature (LCST) behavior in aqueous solutions has been actively studied for various applications in nanotechnology and controlled drug delivery. In this work, a comb‐coil block copolymer is synthesized with PNIPAM coil and polyethyleneimine brushes. Self‐organization of the copolymer into micelle by heating and subsequent cross‐linking of the part of PEI corona resulted in a unique nanocapsule (i‐CLM) with hydrophilic cross‐linked PEI outer shell and thermo‐responsive PNIPAM inner brush. The nanocapsule appears as a vesicle‐like hollow at room temperature but did into micelle‐like spheres when heated. From dynamic light scattering measurement, it is revealed apparently that the nanocapsule exhibited well the swelling and the shrinking reversibly under heating and cooling and the feature is cycled repeatedly with gradual fashion under wide‐range of temperature responding. The carrier property of the nanocapsule is investigated by using hydrophobic fluorophore of Nile red (NR) as a probe and it is found that the hollow of the nanocapsule is a good nano pocket to promote the growth of nanocrystals of NR. [ABSTRACT FROM AUTHOR]

It is a great challenge to refine precious metals from e‐wastes under mild conditions without hazardous reagents. Herein, black phosphorus (BP) was covalently functionalized with poly(N‐isopropylacrylamide) (PNIPAM) to obtain thermo/near‐infrared (NIR)‐responsive BP−P for precious metal recovery. Precious metals (Au, Ag, and Pd) with higher redox potentials than BP−P could be efficiently recovered by reduction‐driven enrichment. Taking Au as an example, the recovery process presented fast kinetics (<15 min), excellent selectivity, and high efficiency (≈98 %). Remote operation with NIR light could generate heat by BP, which induced the hydrophilic‐to‐hydrophobic transition of PNIPAM, allowing the spontaneous gathering, facile collection, and practical recycle of BP−P following Au extraction. Thanks to the unique features of BP−P, not only could high‐quality Au nanoparticles (20–30 nm) be economically extracted (cost: $0.731–1.222 g−1 Au nanoparticles; 5–6 orders of magnitude lower than the market price), but also the formed BP−P‐Au nanocomposites have potential application in hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

In this article, we reported the synthesis of thermoresponsive palladium nanoparticles, stabilized by polymer‐tagged N‐heterocyclic carbenes (NHCs), using two different approaches. In one case, the nanoparticles were synthesized from the NHC–palladium complex, while in other cases, palladium nanoparticles and NHC were synthesized simultaneously for the in situ cappings of the nanomaterial. While the thermoresponsive nature of the nanomaterials was observed in both cases, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) analyses showed distinct characteristics in the thermal behavior of those materials. High‐resolution transmission electron microscopic (HRTEM) and scanning electron microscopic studies separately revealed temperature‐dependent aggregation in both cases although separate patterns were observed when the nanomaterials were synthesized using different approaches. Finally, both the nanomaterials were successfully used as a recyclable catalyst for Suzuki reactions in an aqueous medium, with slightly different catalytic activity, plausibly due to variations in the size of the nanoparticles. [ABSTRACT FROM AUTHOR]

The versatile design of stimuli‐responsive microparticles embedding valuable biomolecules has great potential in a variety of engineering fields, such as sensors, actuators, drug delivery, and catalysis. Here, results are reported on thermoresponsive core–gap–shell (TCGS) microcapsules made of poly(N‐isopropylacrylamide) (PNIPAm), which encapsulate hydrophilic payloads in a simple and stable manner. These are realized by a one‐step microfluidic approach using the phase separation of a supersaturated aqueous solution of NIPAm. Various designs of the microcapsules are achieved by individual control of the swelling or by incorporating pH‐responsive comonomers of the inner core and outer shell. The gap, i.e., the space between the inner core and outer shell, can be loaded with cargo‐like nanoparticles. The outer shell can serve as a stimuli‐responsive gateway for the transport of smaller molecules from the external solution. It is shown that the TCGS microcapsules are suitable as temperature controllable glucose sensors and hold promise in the design of controllable enzymatic reactions. The proposed platform provides an avenue for developing a new‐generation of microparticles for diverse and efficient engineering applications. [ABSTRACT FROM AUTHOR]

Thermoresponsive hydrogels with high stretchability and large swelling ratio are promising materials for fabricating soft devices, sensors, artificial muscles, etc. However, it remains a challenge to achieve these properties simultaneously within one hydrogel. Herein, highly swellable and stretchable thermoresponsive hydrogels are developed by incorporating functionalized boron nitride nanosheets (f‐BNNSs) into poly(maleic anhydride functionalized β‐cyclodextrin‐co‐N‐isopropylacrylamide) hydrogel. In such hydrogels, the dynamic host–guest interactions between f‐BNNSs and polymer matrix act as sacrificial bonds to efficiently dissipate energy, and the homogeneous covalent cross‐linking network of polymer leads to a smooth stress propagation, which enables the hydrogels to obtain excellent mechanical properties, such as remarkable strength (up to 0.15 MPa) and outstanding stretchability (up to 1457%). What is more, the resultant hydrogel also exhibits excellent thermoresponsive properties (swelling rate up to 5000% at 25 °C and deswelling rate down to 6% at 50 °C). Thus, this work offers a promising strategy to fabricate highly swellable and stretchable thermoresponsive hydrogels for potential soft actuators and bionic robotics applications. [ABSTRACT FROM AUTHOR]

We report an in situ polymerization strategy to incorporate a thermo‐responsive polymer, poly(N‐isopropylacrylamide) (PNIPAM), with controlled loadings into the cavity of a mesoporous metal–organic framework (MOF), MIL‐101(Cr). The resulting MOF/polymer composites exhibit an unprecedented temperature‐triggered water capture and release behavior originating from the thermo‐responsive phase transition of the PNIPAM component. This result sheds light on the development of stimuli‐responsive porous adsorbent materials for water capture and heat transfer applications under relatively mild operating conditions. [ABSTRACT FROM AUTHOR]

A vitamin‐B2‐based macroinitiator is prepared by esterification of riboflavin with 2‐bromoisobutyryl bromide. Following the "core first" methodology, "phoenix"‐shape (co)polymers with a polar riboflavin core and either a hydrophobic (poly(n‐butyl acrylate) or poly(methyl methacrylate)) or hydrophilic (poly(N‐isopropylacrylamide)‐block‐poly(oligo(ethylene glycol) acrylate) or poly(N‐isopropylacrylamide)‐block‐poly(2‐hydroxyethyl acrylate)) tails are synthesized via low ppm atom transfer radical polymerization procedures. Polymers have predetermined molecular weights and a low dispersity (Ð < 1.2). 1H NMR analysis confirms the successful formation of targeted (co)polymers with the preserved riboflavin functionality. [ABSTRACT FROM AUTHOR]

Many marine organisms have developed adhesives that are able to bond under water, overcoming the challenges associated with wet adhesion. A key element in the processing of several natural underwater glues is complex coacervation, a liquid–liquid phase separation driven by complexation of oppositely charged macromolecules. Inspired by these examples, the development of a fully synthetic complex coacervate‐based adhesive is reported with an in situ setting mechanism, which can be triggered by a change in temperature and/or a change in ionic strength. The adhesive consists of a matrix of oppositely charged polyelectrolytes that are modified with thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) grafts. The adhesive, which initially starts out as a fluid complex coacervate with limited adhesion at room temperature and high ionic strength, transitions into a viscoelastic solid upon an increase in temperature and/or a decrease in the salt concentration of the environment. Consequently, the thermoresponsive chains self‐associate into hydrophobic domains and/or the polyelectrolyte matrix contracts, without inducing any macroscopic shrinking. The presence of PNIPAM favors energy dissipation by softening the material and by allowing crack blunting. The high work of adhesion, the gelation kinetics, and the easy tunability of the system make it a potential candidate for soft tissue adhesion in physiological environments. [ABSTRACT FROM AUTHOR]

Multiple gold nanoparticles (AuNPs) are physically encapsulated within a poly(N‐isopropylacrylamide) particle at room temperature by an in situ reduction method using trisodium citrate (Cit) and sodium oxalate (Oxa) to serve as quasi‐homogeneous catalysts for carbon−carbon bond‐forming reactions under base‐free aerobic conditions. The use of Oxa results in a more rapid formation and higher loading of AuNPs within the polymer particles compared to those prepared with conventional Cit. Upon dispersing both composite particles in EtOH‐rich aqueous solvents, the polymer matrices maintain a fully swollen structure while still providing great stability to the AuNPs whose surfaces are analyzed to be nearly free from the reducing/stabilizing agents. As a catalyst in homocoupling reactions, the composite particles prepared with Oxa exhibit higher activity, selectivity, and recyclability with a much lower activation energy than those prepared with Cit. The preparation of the composite particles and their catalytic properties are optimized under environmentally‐friendly reaction conditions, and the relationship between structural features and catalytic functions are examined to potentially develop robust, versatile, and green catalytic systems. [ABSTRACT FROM AUTHOR]

BACKGROUND: Butanol production through ABE (acetone, butanol, and ethanol) fermentation has attracted a great deal of attention because of its potential to replace petroleum‐based fuels. Low butanol production and productivity due to butanol inhibition are the main challenges to make ABE fermentation viable economically. In this work, polydimethylsiloxane (PDMS) sponge and thermos‐responsive poly(N‐isopropylacrylamide)‐grafted PDMS (PNIPAAm‐PDMS) sponges (with different mass fractions of PNIPAAm on the PDMS surface) were investigated as adsorbents for butanol. RESULTS: The butanol model solutions showed that the adsorption–desorption efficiency of different types of sponges for butanol is highly temperature‐dependent. Higher temperatures exhibited higher adsorption efficiency. In contrast, lower temperatures markedly increased the desorption efficiency for butanol. PNIPAAm‐PDMS with 8.0 wt% of PNIPAAm on the PDMS surface showed as the best adsorbent for butanol. It had adsorption efficiency of 14, 24 and 46% at 25, 37 and 50 °C, respectively. Moreover, 96% of butanol adsorbed was recovered at 25 °C. When it was coupled with a batch ABE fermentation by Clostridium acetobutylicum, butanol production increased by 102% compared to batch fermentation without adsorption. A semi‐continuous fermentation with the initial feeding time at the 60th hour exhibited as the optimum condition. However, it failed to enhance butanol productivity due to a high accumulation of butanol in the broth. Then, a semi‐continuous fermentation with adsorption was conducted, yielding total butanol production of 20 g/L. CONCLUSION: PNIPAAm‐PDMS sponge is proposed as an adsorbent to overcome butanol inhibition in ABE fermentation by temperature manipulation to recover butanol. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Hydrogels with environment‐sensitive properties have great potential applications in the controlled drug release field. In this paper, hybrid hydrogels with semi‐interpenetrating polymer networks (semi‐IPNs), composed of poly(N‐isopropylacrylamide) (PNIPAM) as the thermo‐sensitive component by in situ polymerization and self‐assembled collagen nanofibrils as the pH‐sensitive framework, were prepared for controlled release of methyl violet as a model drug. From Fourier transform infrared spectroscopy and scanning electron microscopy, it was indicated that the crosslinking of PNIPAM in the presence of collagen nanofibrils led to the formation of semi‐IPNs with homogeneous porous structure, and the semi‐IPNs showed improved thermal stability and elastic properties compared with the native collagen as determined using differential scanning calorimetry and rheologic measurements. Furthermore, the semi‐IPNs possessed swelling behaviors quite different from those of neat collagen or PNIPAM hydrogel under various pH values and temperatures. Correspondingly, as expected, the drug release behavior in vitro for semi‐IPNs performed variously compared with that for single‐component semi‐IPNs, which revealed the tunable performance of semi‐IPNs for release ability. Finally the thermo‐ and pH‐responsive mechanism of the semi‐IPNs was illuminated to provide guidance for the application of the thermo‐ and pH‐sensitive collagen‐based hybrid hydrogels in controlled drug delivery systems. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

To realize a renewable energy society, a polymeric system for photoinduced hydrogen generation utilizing a copolymer containing an electron acceptor was designed. In this system, the redox changes of viologen introduced into poly(N‐isopropylacrylamide) cause cyclic conformational changes owing to the shifting of the phase transition temperature (PTT). The polymeric coil–globule transitions with hydrophilic/hydrophobic changes accelerate the electron transfer for hydrogen generation. In particular, hydrogen generation using visible‐light energy with high efficiency is achieved around the PTT. In contrast to conventional solution systems, our polymeric system enables efficient hydrogen generation in a close molecular arrangement without the aggregation of catalytic nanoparticles. The utilization of conformational changes will provide a new strategy for synthesizing artificial photosynthetic hydrogels that split water to generate both hydrogen and oxygen. [ABSTRACT FROM AUTHOR]

Cell sheet tissue engineering is a concept for creating transplantable two‐dimensional (2D) and three‐dimensional (3D) tissues and organs. This review describes three elements of cell sheet tissue engineering in terms of the chemical and physical effects of material surfaces and the interfacial properties of cell sheets: preparation, harvesting/manipulation and transplantation of cell sheets. An essential technology for the preparation of cell sheets is the use of a temperature‐responsive cell culture surface, where the surface of tissue culture polystyrene (TCPS) dish is modified with thin layer of temperature‐responsive polymer, poly(N‐isopropylacrylamide) (PIPAAm). PIPAAm‐immobilized TCPS allows cultured cells to be harvested as a contiguous cell sheet with extracellular matrices (ECMs) by reducing the temperature, while chemical and physical disruption impair ECMs, cell–cell junction, and membrane proteins. Ligand‐immobilized and porous hydrophilic PIPAAm‐grafted surfaces are able to accelerate cell sheet preparation and harvesting, respectively. In addition, the manipulation of harvested cell sheets with the aid of cell sheet manipulator facilitates the formation of 3D tissues. Cell sheet‐based tissues and their transplantation are in seven clinical settings such as heart, cornea, esophagus, periodontal, middle chamber of ear, knee cartilage, and lung. In order to create thick and large 3D tissues and organs, large production of differentiated parenchymal cells from induced pluripotent stem (iPS) cells and vascularization within 3D tissues are key issues. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 955–967, 2019. [ABSTRACT FROM AUTHOR]

Recently, there are significant interests in the development of biomaterials with nonlinear response to an external stimulus. Thermoresponsive polymers as a well‐known class of stimuli‐responsive materials represent reversible hydrophilicity/hydrophobicity characteristics around a critical temperature. This switchable behavior applies for nondestructive cellular detachment from cultivation substrates. In this study, poly (N‐isopropylacrylamide) (PNIPAAm)‐grafted dishes were made up to harvest retinal pigmented epithelial (RPE) and periodontal ligament cell (PDLC) sheets. Wettability assessments verified that all functionalized surfaces were inverted from hydrophilic to hydrophobic state when the temperature rises from lower critical solution temperature (LCST) at 37 °C. Other physicochemical characteristics such as chemical composition, grafting thickness, and surface topography were investigated through attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR) and atomic force microscopy (AFM). ATR‐FTIR results showed typical peaks of amide group corresponding to successful PNIPAAm polymerization. AFM microscopy results also proved creating a rough PNIPAAm layer with thickness of 29.2 nm after grafting process in the mixture of methanol and water. Cell culture experiments showed an irreversible cellular attachment/detachment from modified surfaces upon temperature changes. These results introduced thermoresponsive TCPS to noninvasively harvest RPE and PDLCs sheets especially for application in scaffold‐free tissue engineering decorations. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1567–1576 In this study, a uniform polymeric layer with appropriate thickness (15 nm) was polymerized and grafted on the surface of TCPS substrate using electron beam irradiation at the static mode in the mixture of methanol/water solvents. Given the inherent intelligence of PNIPAAm and the versatility of the grafting method, obtained smart surfaces showed promising future in cell sheet engineering, particularly for periodontal tissue regeneration and treatment of sight‐threatening diseases caused by retina degeneration. [ABSTRACT FROM AUTHOR]

Thermosensitive microgel particles based on the polymeric network synthesized from N‐isopropylacrylamide, sodium acrylate and N,N′‐bisacryloylcystine have been functionalized with aminoferrocene, a mediatior, and a model enzyme‐glucose oxidase (GOx). The product was very stable. A thin coating of that material has been successfully attached to the glassy carbon electrode surface to form a sensing layer. A temperature increase to a value higher than the volume phase transition temperature led to a substantial increase in the amperometric signal. That behavior was well switchable. The amperometric signal was linearly dependent on glucose concentration in the physiological concentration range. It appeared that the synthesized and functionalized microgel was a kind of microreactor and might be very useful for the construction of the platforms that can enhance the activity of enzymes in biosensors. [ABSTRACT FROM AUTHOR]

Abstract: Large‐area dynamic switchable plasmonic metafilms composed of a network of gold nanoparticles (Au NPs) and the thermo‐responsive polymer poly(N‐isopropylacrylamide) (PNIPAM) are self‐assembled by casting Au@PNIPAM core–shell nanoparticles. These dense plasmonic films present an unusual optical behavior arising from the macroscale effective medium response of the film and the microscopic interactions of the gold nanoparticles. Such intensely colored plasmonic metafilms can be thermally actuated across large areas via direct heating, allowing extraction of the tuning of the effective dielectric permittivity of this metamaterial. By contrast, local plasmonic heating by illuminating the Au NPs in these metafilms enables sub‐second and highly reversible contraction of the plasmonic metafilms, capable of pumping water. This work provides a paradigm for switchable metafilms and metasurfaces that can be harnessed for different applications such as sensing, imaging optics, and image displays. [ABSTRACT FROM AUTHOR]

Abstract: The self‐diffusion of various nano‐objects investigated by high‐resolution nuclear magnetic resonance diffusometry proves to be an efficient method for the characterization of dynamics, aggregation kinetic, and matrix morphology. This study investigates how the two‐state model and Boltzmann function approach can be used for the evaluation of the thermodynamic parameters of temperature‐induced phase transition encoded in polymer diffusivity. The characteristics of the phase transition given by the transition temperature, change of entropy, and width of transition are obtained for poly(N‐isopropylacrylamide) (PNIPAm) linear polymers with hydrophilic and hydrophobic end‐group functionalization. The effect of end groups upon the polymer diffusivity is investigated as a function of molecular weight (M n), from which fractal dimensions and hydrodynamic drag coefficients are obtained. The PNIPAm diffusivity is affected strongly by the end groups, and it is reflected in the hydrodynamic radius dependence upon molecular weight that obeys different power‐law relations. In this study, the synthesis of α‐ω‐heterotelechelic PNIPAm of different molecular weights with a thiol end group and a hydrophilic NIPAm‐like as well as a hydrophobic benzyl end group are described by reversible addition–fragmentation chain‐transfer polymerization. [ABSTRACT FROM AUTHOR]

ABSTRACT Aqueous solutions of a series of monodisperse poly( N-isopropylacrylamide)s end-labeled with n-butyl-1-pyrene at one or both chain ends (Py n-PNIPAMs with n = 1 or 2) were studied by turbidimetry, light scattering, and fluorescence. For a given polymer concentration and heating rate, the cloud point ( Tc) of an aqueous Py n-PNIPAM solution, determined by turbidimetry, was found to increase with the number-average molecular weight ( Mn) of the polymer. The steady-state fluorescence spectra and time-resolved fluorescence decays of Py n-PNIPAM aqueous solutions were analyzed and all parameters retrieved from these analyses were found to be affected as the solution temperature passed through Tc, the solution cloud point, and Tm, the temperature where dehydration of PNIPAM occurred. The trends obtained by fluorescence to characterize the aqueous Py n-PNIPAM solutions as a function of temperature were found to be consistent with the model proposed for telechelic PNIPAM by Koga et al. in 2006. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 308-318 [ABSTRACT FROM AUTHOR]

Free and cellulose nanocrystals (CNCs)-grafted block copolymers of acrylic acid and N-isopropylacrylamide with various poly( N-isopropylacrylamide) (PNIPAAm) block lengths as dual temperature- and pH-sensitive materials were synthesized by reversible addition-fragmentation chain transfer polymerization via an R-approach method. Controlling lower critical solution temperature (LCST) of the products by changing the PNIPAAm block length, addition of CNC, and variation of pH was studied. The free and CNC-grafted block copolymers were analyzed by Fourier transform infrared and proton nuclear magnetic resonance. LCST of copolymers was measured by dynamic light scattering using their hydrodynamic diameters. The block copolymers reversibly form core-corona structure with PNIPAAm as core and poly(acrylic acid) (PAA) as shell above LCST at higher pH values. LCST point shifts to higher temperatures by increasing pH and CNC content and also lowering PNIPAAm block length. By decreasing pH below 4 at certainly low temperatures, PAA becomes core and PNIPAAm forms corona. Thermal behavior of the CNC-grafted polymers was studied by thermal gravimetric analysis and differential scanning calorimetry. Morphology of the polymer-grafted CNC was examined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 231-243, 2018. [ABSTRACT FROM AUTHOR]

Many low molecular weight and polymeric additives are found to be able to shift the phase transition temperature of poly( N-isopropylacrylamide) (PNIPAM), however, a large change can only be observed at a high concentration of the additive. Particularly, poly(vinyl alcohol) (PVA), a polymeric additive, can only induce a very small change in the phase transition temperature of PNIPAM, even at a high concentration. Unexpectedly, it is found that a low concentration of PVA can dramatically reduce the volume phase transition temperature (VPTT) of the surface layer of poly( N-isopropylacrylamide- co-2-acrylamido-phenylboronic acid) (P(NIPAM-2-AAPBA)) microgel. The concentration of PVA is about three orders of magnitude lower than the required concentration for other additives to achieve a comparable decrease in phase transition temperature of PNIPAM. The lowered VPTT cannot be explained by a change in the ionization degree of the PBA groups, or cross-link density, or hydrophilicity-hydrophobicity balance of the gel. Instead, it is proposed that the adsorption of PVA chains onto the P(NIPAM-2-AAPBA) microgel spheres shortens the distance between the PVA and PNIPAM chains, allowing they influence the thermal behavior of PNIPAM more effectively and hence dramatically reducing the phase transition temperature of the latter. [ABSTRACT FROM AUTHOR]

Magnetic core-shell nanoparticles are one of the most interesting nanocarriers. Smart polymers can be attached to nanoparticles as a suitable shell. Cancer tissues, with higher temperature than normal one, are one of the best targets for these systems in which the polymeric shell shrinks and thus drugs are released. The aim of this research is to synthesize such a smart nanocarrier with a thermoresponsive shell. Magnetic nanoparticles are coated with poly( N-isopropylacrylamide). Afterward, the as prepared nanoparticles are analyzed through different characterization methods (scanning electron microscope, Fourier-transform infrared spectroscopy, carbon-hydrogen-nitrogen-sulfur elemental analysis, energy-dispersive X-ray spectroscopy) and their response to the temperature is investigated in different temperatures (37 and 40 °C). Results demonstrate that a biocompatible nanocarrier with the average size of about 35 nm and 83% entrapment efficiency for curcumin is successfully synthesized. The drug release process shows a controlled behavior over temperature. It has an increasing trend by increasing the temperature from 4 to 37 °C and then to 40 °C. Moreover, the cytotoxicity of drug loaded nanocarrier is obviously increased at 40 °C compared to 37 °C. It can be concluded that this new smart nanotheranostics agent can be successfully applied for cancer treatment. [ABSTRACT FROM AUTHOR]

Quantification of the stimuli-responsive phase transition in polymers is topical and important for the understanding and development of novel stimuli-responsive materials. The temperature-induced phase transition of poly( N-isopropylacrylamide) (PNIPAm) with one thiol end group depends on the confinement-free polymer or polymer brush-on the molecular weight and on the nature of the second end. This paper describes the synthesis of heterotelechelic PNIPAm of different molecular weights with a thiol end group-that specifically binds to gold nanorods and a hydrophilic NIPAm end group by reversible addition-fragmentation chain-transfer polymerization. Proton high-resolution magic angle sample spinning NMR spectra are used as an indicator of the polymer chain conformations. The characteristics of phase transition given by the transition temperature, entropy, and width of transition are obtained by a two-state model. The dependence of thermodynamic parameters on molecular weight is compared for hydrophilic and hydrophobic end functional-free polymers and brushes. [ABSTRACT FROM AUTHOR]

ABSTRACT Mixed micelle formation between two oppositely charged diblock copolymers that have a common thermosensitive nonionic block of poly( N-isopropylacrylamide) (PNIPAAM) has been studied. The block copolymer mixed solutions were investigated under equimolar charge conditions as a function of both temperature and total polymer concentrations by turbidimetry, differential scanning calorimetry, two-dimensional proton nuclear magnetic nuclear Overhauser effect spectroscopy (2D 1H NMR NOESY), dynamic light scattering, and small angle X-ray scattering measurements. Well-defined and electroneutral cylindrical micelles were formed with a radius and a length of about 3 nm and 35 nm, respectively. In the micelles, the charged blocks built up a core, which was surrounded by a corona of PNIPAAM chains. The 2D 1H NMR NOESY experiments showed that a minor block mixing occurred between the core blocks and the PNIPAAM blocks. By approaching the lower critical solution temperature of PNIPAAM, the PNIPAAM chains collapsed, which induced aggregation of the micelles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1457-1469 [ABSTRACT FROM AUTHOR]

Quest for efficient fog harvesting methods has drawn immense attention in recent times. In this study, electrospinning is used to fabricate three different sets of membranes that are based on pristine poly( N-isopropylacrylamide) (PNIPAM) fibers, pristine polyvinylidene fluoride (PVDF) fibers, and PNIPAM-PVDF bead-on-string fibers. The wettability of these membranes is investigated as a function of temperature and the effect of their wettability on the fog collection efficiency is determined. Membranes based on pristine PNIPAM and pristine PVDF fibers are fabricated using conventional electrospinning and are shown to have a smooth surface morphology. On the other hand, PNIPAM-PVDF bead-on-string fibers are fabricated using core-shell electrospinning. Water collection efficiency of the membranes is compared to investigate the influence of microstructures and wettability gradient on fog harvesting ability of the samples. Among the three samples, the bead-on-string hierarchical fibrous membrane demonstrates the highest fog harvesting rate of 1150 ± 28 mg cm−2 h−1 at 25 °C and 909 ± 31 mg cm−2 h−1 at 40 °C. Furthermore, the results demonstrate that the presence of microstructures on the nanofibers improve the fog harvesting efficiency of PNIPAM-PVDF bead-on-string fibers. [ABSTRACT FROM AUTHOR]

Random copolymer gels of N-isopropylacrylamide (NIPAM) and N-ethylacrylamide (NEAM) are synthesized using different monomer compositions in 1:1 methanol-water mixtures. The samples are characterized by scanning electron microscopy, atomic force microscopy (AFM), and rheological studies. It is observed that with the variation of the monomer compositions in the reaction mixture, the thermoresponsive, morphological, AFM, and rheological properties varied significantly. Porosity and roughness of the gels gradually increase with the gradual increase in NIPAM loading in the gels, lower critical solution temperature, mechanical strength (Young's modulus, storage modulus) significantly decreases with the increase in poly( N-isopropylacrylamide) loading in the gels. All results can be explained on the basis of the differences in thermoresponsive character of homo- and copolymer gels of NIPAM and NEAM in water, their composition in the reaction mixtures, and their different kind of interactions with solvents. [ABSTRACT FROM AUTHOR]

Temperature-induced phase transition parameters of responsive free polymer and brushes onto nanoparticles are measured using high-resolution magic-angle sample spinning (HRMAS) NMR spectroscopy. To this purpose, a two-state statistical model of temperature dependence of thermodynamic observables is developed and applied to obtain parameters which characterize the process of temperature-induced phase transition of stimuli-sensitive polymers. In this investigation the thermodynamic observable is the integral intensity of the 1H HRMAS NMR spectrum peaks and the derived thermodynamic parameters are transition temperature and transition entropy. This approach is applied to investigate the dependence of temperature-induced coil-to-globule transition of poly( N-isopropylacrylamide), (PNIPAm), asymmetric end functionalized with benzyl and thiol groups (Bn-PNIPAm-SH) on molecular weight in the range 3600-30 000 g mol-1 in aqueous solutions. The characteristics of the phase transition represented by transition temperature, and transition entropy are compared to that of Bn-PNIPAm-SH brushes onto gold nanorods in the same range of molecular weight. The method used for measuring the characteristics of phase transition is based on transverse magnetization relaxation ( T2) spin-echo enhance editing of the integral intensities of the 1H HRMAS NMR spectra. This NMR observable reflects changes in transverse relaxation times as an indicative of the polymer chains conformations and dynamics reached in the process of temperature-induced phase transition. [ABSTRACT FROM AUTHOR]

Poly( N-isopropylacrylamide- co-3-(trimethoxysilyl)propyl methacrylate), P(NIPAAm- co-TMSPMA), copolymers with relatively high TMSPMA contents without insoluble fraction are successfully synthesized. Subsequent sol-gel reactions in both the absence and presence of tetraethyl orthosilicate lead to gels with high gel fractions. The resulting gels undergo gel collapse at 28.6-28.7 °C, i.e., below that of poly( N-isopropylacrylamide) homopolymer of 34.3 °C. Unexpectedly, the theophylline-loaded hybrid gels release the drug not only below but also above the gel collapse temperature (GCT) with considerable rates and released amounts of drug. Surprisingly, evaluation of the sustained release profiles by the Korsmeyer-Peppas equation indicates that the release occurs by Fickian diffusion above GCT, which can be attributed to the lack of significant drug-polymer interaction at such temperatures. These results can be widely applied for the design and utilization of TMSPMA-based sol-gel polymer hybrids with desired release profiles of solutes below and above GCT for a variety of applications. [ABSTRACT FROM AUTHOR]

Inappropriately, the critical solution temperature (CST) of lower CST(LCST)- or upper CST(UCST)-type thermoresponsive polymers, measured by one, individual set of conditions, is considered almost exclusively as the LCST or UCST, respectively. These are correctly the minimum or maximum, respectively, of the full phase diagrams. Because the dynamic phase transition depends on the conditions, and no standardized or widely accepted process exists for CST determination, systematic investigations are carried out with the most widely investigated poly( N-isopropylacrylamide) (PNIPAAm) to unveil the effect of data evaluation, measurement conditions on the transmittance-temperature curves, cloud point ( TCP), clearing point ( TCL), and heating-cooling hysteresis. The unusual dependence of the fundamental hysteresis parameters, i.e., width of hysteresis ( XH) and extent of transmittance recovery ( YH), on a broad range of conditions is revealed for the first time. On the basis of the findings, the inflection point of transmittance(absorbance)-temperature curves as TCP and TCL, 0.1 wt% solution, 0.2 °C min−1 heating/cooling steps with 5 min equilibration between the gradual change of temperature, 488 nm wavelength to obtain data comparable to light scattering at this wavelength, and determination of XH and YH are proposed as standard set of conditions. [ABSTRACT FROM AUTHOR]

Silver nanoparticle (AgNP)/poly( N-isopropylacrylamide) (PNIPAAm) composite solution was electrospun followed by crosslinking to fabricate AgNP/PNIPAAm composite nanofiber mats. Embedded AgNPs were found to align along the PNIPAAm nanofibers, which generate more hotspots upon laser-induced plasmonic heating. This kind of AgNP/PNIPAAm mats show enhanced surface-enhanced Raman scattering (SERS) effect upon continuous pulsed laser irradiation, showing a 'laser heating sensitive' SERS effect. Laser-induced plasmonic heating can also tune the temperature-responsive interaction between PNIPAAm and analytes and has been applied in the on-site 'laser heating sensitive' separation and SERS detection of analytes. The composite nanofiber mats also showed good reproducibility and stability. What is more, this 'laser heating sensitivity' has also been applied in the direct SERS detection of adenosine in urea solution without urea interference. Together with the advantages of ease of large-scale fabrication, stable and 'laser heating sensitivity', AgNP/PNIPAAm mats might find application in sensitive multicomponent biosensing. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Molecular-recognition-responsive characteristics of a novel poly( N-isopropylacrylamide- co-benzo-12-crown-4-acrylamide) (PNB12C4) hydrogel have been investigated. In the prepared PNB12C4 hydrogel, benzo-12-crown-4 (B12C4) groups act as guest molecules and γ-cyclodextrin (γ-CD)-receptors, and poly( N-isopropylacrylamide) (PNIPAM) networks act as phase-transition actuators. The formation of stable γ-CD/B12C4 complexes enhances the hydrophilicity of the PNB12C4 hydrogel networks, and induces positive shift of the volume phase transition temperature (VPTT) of PNB12C4 hydrogel. Moreover, the PNB12C4 hydrogel also shows thermoresponsive adsorption property selectively towards γ-CD. The γ-CD-recognition sensitivity of PNB12C4 hydrogel can be dramatically improved by increasing γ-CD concentration in solution or B12C4 content in PNB12C4 copolymer networks. The results in this study provide valuable information for developing crown ether-based smart materials in various applications. [ABSTRACT FROM AUTHOR]

ABSTRACT The heat-induced phase transition of aqueous solutions of Poly( N-isopropylacrylamide) (PNIPAM) in water is examined for a four-arm PNIPAM star ( s-PNIPAM), a cyclic PNIPAM ( c-PNIPAM), and their linear counterparts ( l-PNIPAM) in the case of polymers (1.0 g L−1) of 12,700 g mol−1 < Mn < 14,700 g mol−1. Investigations by turbidity, high-sensitivity differential scanning calorimetry (HS-DSC), and light scattering (LS) indicate that the polymer architecture has a strong effect on the cloud point ( Tc: decrease for s-PNIPAM; increase for c-PNIPAM), the phase transition enthalpy change (Δ H decrease for s-PNIPAM and c-PNIPAM), and the hydrodynamic radius of the aggregates formed above Tc ( RH: c-PNIPAM < s-PNIPAM < l-PNIPAM). The properties of s-PNIPAM are compared with those of previously reported PNIPAM star polymers (3 to 52 arms). The overall observations are described in terms of the arm molecular weight and the local chain density in the vicinity of the core of the star, by analogy with the model developed for PNIPAM brushes on nanoparticles or planar surfaces. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2059-2068. [ABSTRACT FROM AUTHOR]

ABSTRACT Exothermic nonreversing process is predicted to present in the phase transition of poly( N-isopropylacrylamide) (PNIPAM). By employing TOPEM-DSC, exothermic nonreversing heat flow peak is observed for the first time, and it usually appears under nonquasi-static conditions. The exothermic nonreversing heat flow is proved to be from the formation of hydrogen bonds by the comparative studies on the phase transition of poly( N, N-diethylacrylamide) (PDEAM) and cyclic heating and cooling of PDEAM and PNIPAM. Further TOPEM-DSC studies on the phase transition of poly(NIPAM- co-DEAM) and poly(NIPAM- co-AAm) prove that hydrophobic force rather than hydrogen bonding is the main driving force for the phase transition, and hydrophobic force is also the driving force for the formation of inter- and intrachain hydrogen bonding. However, the phase transition driven by only hydrophobic force is a slow process. The combined action of hydrogen bonding and hydrophobic force makes the phase transition occur much faster. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1869-1877 [ABSTRACT FROM AUTHOR]

A self-cleaning membrane that periodically rids itself of attached cells to maintain glucose diffusion could extend the lifetime of implanted glucose biosensors. Herein, we evaluate the functionality of thermoresponsive double network (DN) hydrogel membranes based on poly( N-isopropylacrylamide) (PNIPAAm) and an electrostatic co-monomer, 2-acrylamido-2-methylpropane sulfonic acid (AMPS). DN hydrogels are comprised of a tightly crosslinked, ionized first network [P(NIPAAm-co-AMPS)] containing variable levels of AMPS (100:0-25:75 wt% ratio of NIPAAm:AMPS) and a loosely crosslinked, interpenetrating second network [PNIPAAm]. To meet the specific requirements of a subcutaneously implanted glucose biosensor, the volume phase transition temperature is tuned and essential properties, such as glucose diffusion kinetics, thermosensitivity, and cytocompatibility are evaluated. In addition, the self-cleaning functionality is demonstrated through thermally driven cell detachment from the membranes in vitro. [ABSTRACT FROM AUTHOR]

Abstract: We developed a new facile method for the preparation of temperature‐responsive cell culture surfaces (TRCS) by photo‐polymerization of N‐isopropylacrylamide using a surface‐immobilized photoinitiator. In the first step, thioxanthone groups, which served as the photoinitiator, were directly formed on polystyrene culture dish surfaces (TX‐PSt). Second, poly(N‐isopropylacrylamide) (PIPAAm) was grafted onto the TX‐PSt surfaces (PIPAAm‐TX‐PSt) by using the visible light or light‐emitting diode irradiation‐induced surface‐initiated polymerization method. By optimizing the amount of grafted PIPAAm, the resulting PIPAAm‐TX‐PSt successfully exhibited characteristics of a TRCS. In addition, a striped micropatterned polyacrylamide area was successively formed on the photoirradiated PIPAAm‐TX‐PSt surface by using a chromium photomask. These results show that temperature‐responsive cell culture surfaces can be prepared through this new method. [ABSTRACT FROM AUTHOR]

The grim prognosis for patients diagnosed with malignant gliomas necessitates the development of new therapeutic strategies for localized and sustained drug delivery to combat tumor drug resistance and regrowth. Here we introduce drug encapsulated aerosolized microspheres as a biodegradable, intelligent glioma therapy (DREAM BIG therapy). DREAM BIG therapy is envisioned to deliver three chemotherapeutics, temporally staged over one year, via a bioadhesive, biodegradable spray directly to the brain surgical site after tumor excision. In this proof-of-principle article exploring key components of the DREAM BIG therapy prototype, rhodamine B (RB) encapsulated poly(lactic-co-glycolic acid) and immunoglobulin G (IgG) encapsulated poly(lactic acid) microspheres were formulated and characterized. The encapsulation efficiency of RB and IgG and the release kinetics of the model drugs from the microspheres were elucidated in addition to the release kinetics of RB from poly(lactic-co-glycolic acid) microspheres formulated in a degradable poly(N-isopropylacrylamide) solution. The successful aerosolized application onto brain tissue ex-vivo demonstrated the conformal adhesion of the RB encapsulated poly(lactic-co-glycolic acid) microspheres to the convoluted brain surface mediated by the thermoresponsive carrier, poly(N-isopropylacrylamide). These preliminary results suggest the potential of the DREAM BIG therapy for future use with multiple chemotherapeutics and microsphere types to combat gliomas at a localized site. [ABSTRACT FROM AUTHOR]

Ordered mesoporous silica nanoparticles with pore diameter of 5 nm were synthesized by modification of the sol-gel synthesis method. Post-synthesis two-step grafting of thermoresponsive poly( N-isopropylacrylamide) inside the mesopores of the nanoparticles was carried out by distillation-precipitation polymerization of the methacryloxy-functionalized mesoporous nanoparticles with N-isopropylacrylamide monomer. A precise control on the quantity of the grafted polymer was achieved by changing the ratio of monomer to methacryloxy-functionalized nanoparticles. The polymer-grafted hybrid nanoparticles obtained were fully characterized by infrared spectroscopy, X-ray diffraction, dynamic light scattering, transmission electron microscopy, thermal, and gas-volumetric analyses, which clearly showed presence and thermoresponsive behavior of the polymer inside the mesopores with the preservation of the characteristic mesoporous structure of the nanoparticles. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]