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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 (

Per- and polyfluoroalkyl substances (PFAS) have rapidly accumulated in the environment due to their widespread use prior to commercial discussion in the early 21st century, and their slow degradation has magnified concerns of their potential toxicity. Monitoring their distribution is, therefore, necessary to evaluate and control their impact on the health of exposed populations. This investigation evaluates the capability of a simple polymeric detection scheme for PFAS based on crosslinked, thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) hydrogels. Surveying swelling perturbations induced by several hydrotropes and comparable hydrocarbon analogs, tetraethylammonium perfluorooctane sulfonate (TPFOS) showed a significantly higher swelling ratio on a mass basis (65.5 ± 8.8 at 15°C) than any of the other analytes tested. Combining swelling with the fluorimetric response of a solvachromatic dye, nile red, revealed the fluorosurfactant to initiate observable aggregation (i.e., its critical aggregation concentration) at 0.05 mM and reach saturation (i.e., its charge neutralization concentration) at 0.5 mM. The fluorosurfactant was found to homogeneously distribute throughout the polymer matrix with energy dispersive X-ray spectroscopy, marking the swelling response as a peculiar nexus of fluorinated interfacial positioning and delocalized electrostatic repulsion. Results from the current study hold promise for exploiting the physiochemical response of PNIPAM to assess TPFOS's concentration.

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.

Lanthanide-based upconverting nanoparticles (UCNPs) are trustworthy workhorses in luminescent nanothermometry. The use of UCNPs-based nanothermometers has enabled the determination of the thermal properties of cell membranes and monitoring of in vivo thermal therapies in real time. However, UCNPs boast low thermal sensitivity and brightness, which, along with the difficulty in controlling individual UCNP remotely, make them less than ideal nanothermometers at the single-particle level. In this work, it is shown how these problems can be elegantly solved using a thermoresponsive polymeric coating. Upon decorating the surface of NaYF4:Er3+,Yb3+ UCNPs with poly(N-isopropylacrylamide) (PNIPAM), a >10-fold enhancement in optical forces is observed, allowing stable trapping and manipulation of a single UCNP in the physiological temperature range (20–45 °C). This optical force improvement is accompanied by a significant enhancement of the thermal sensitivity— a maximum value of 8% °C+1 at 32 °C induced by the collapse of PNIPAM. Numerical simulations reveal that the enhancement in thermal sensitivity mainly stems from the high-refractive-index polymeric coating that behaves as a nanolens of high numerical aperture. The results in this work demonstrate how UCNP nanothermometers can be further improved by an adequate surface decoration and open a new avenue toward highly sensitive single-particle nanothermometry, This work was supported by the Ministerio de Ciencia e Innovación de España (PID2019-106211RB-I00 PID2019-105195RA-I00 and MAT2017- 83111R), by the Comunidad de Madrid (S2017/BMD-3867 RENIM-CM), co-financed by European Structural and Investment Fund and by the Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid (SI1/PJI/2019-00052 and PR38/21-36 ANTICIPA-CM). D.L. acknowledges a scholarship from the China Scholarship Council (201808350097). J.R.B. acknowledges the support from Carl Tryggers Foundation (CTS18:229). M.I.M acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M) and the MELODIA PGC2018-095777-B-C22 projec

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.

Aqueous solutions of some polymers exhibit a lower critical solution temperature (LCST); that is, they form phase-separated aggregates when heated above a threshold temperature. Such polymers found many promising (bio)medical applications, including in situ thermogelling with controlled drug release, polymer-supported radiotherapy (brachytherapy), immunotherapy, and wound dressing, among others. Yet, despite the extensive research on medicinal applications of thermoresponsive polymers, their biodistribution and fate after administration remained unknown. Thus, herein, they studied the pharmacokinetics of four different thermoresponsive polyacrylamides after intramuscular administration in mice. In vivo, these thermoresponsive polymers formed depots that subsequently dissolved with a two-phase kinetics (depot maturation, slow redissolution) with half-lives 2 weeks to 5 months, as depot vitrification prolonged their half-lives. Additionally, the decrease of T-CP of a polymer solution increased the density of the intramuscular depot. Moreover, they detected secondary polymer depots in the kidneys and liver; these secondary depots also followed two-phase kinetics (depot maturation and slow dissolution), with half-lives 8 to 38 days (kidneys) and 15 to 22 days (liver). Overall, these findings may be used to tailor the properties of thermoresponsive polymers to meet the demands of their medicinal applications. Their methods may become a benchmark for future studies of polymer biodistribution.

Low back pain is a major public health issue associated with degeneration of the intervertebral disc (IVD). The early stages of degeneration are characterized by the dehydration of the central, gelatinous portion of the IVD, the nucleus pulposus (NP). One possible treatment approach is to replace the NP in the early stages of IVD degeneration with a hydrogel that restores healthy biomechanics while supporting tissue regeneration. The present study evaluates a novel thermosensitive hydrogel based on poly(N‐isopropylacrylamide‐graft‐chondroitin sulfate) (PNIPAAM‐g‐CS) for NP replacement. The hypothesis was tested that the addition of freeze‐dried, calcium crosslinked alginate microparticles (MPs) to aqueous solutions of PNIPAAm‐g‐CS would enable tuning of the rheological properties of the injectable solution, as well as the bioadhesive and mechanical properties of the thermally precipitated composite gel. Further, we hypothesized that the composite would support encapsulated cell viability and differentiation. Structure‐material property relationships were evaluated by varying MP concentration and diameter. The addition of high concentrations (50 mg/mL) of small MPs (20 ± 6 μm) resulted in the greatest improvement in injectability, compressive mechanical properties, and bioadhesive strength of PNIPAAm‐g‐CS. This combination of PNIPAAM‐g‐CS and alginate MPs supported the survival, proliferation, and differentiation of adipose derived mesenchymal stem cells toward an NP‐like phenotype in the presence of soluble GDF‐6. When implanted ex vivo into the intradiscal cavity of degenerated porcine IVDs, the formulation restored the compressive and neutral zone stiffnesses to intact values and resisted expulsion under lateral bending. Overall, results indicate the potential of the hydrogel composite to serve as a scaffold for supporting NP regeneration. This work uniquely demonstrates that encapsulation of re‐hydrating polysaccharide‐based MPs may be an effective method for improving key functional properties of in situ forming hydrogels for orthopedic tissue engineering applications.

Stimuli-sensitive drug delivery systems show beneficial features of both medical and pharmaceutical fields. In this article, polymeric nanogel P (N-isopropylacrylamide-N,N '-dimethylaminoethyl methacrylate [NIPAM-DMAEMA]) (PND) with pH/redox/thermo-responsivenesses was synthesized by the in situ polymerization of NIPAM and DMAEMA for the controlled release of doxorubicin hydrochloride (DOX) and N,N '-bis(acryloyl)cystamine (BAC) and N,N '-methylenebisacrylamide (MBA) act as the crosslinkers, respectively. The structure, size, and zeta potential of PND-BAC and PND-MBA were further characterized. Moreover, after loading DOX, the encapsulation efficiency and the in vitro release behavior of PND-BAC/DOX and PND-MBA/DOX nanogels were discussed in detail. Compared to PND-MBA NGs, PND-BAC nanogels have redox degradability due to the presence of the crosslinker BAC. After loading DOX, the PND-BAC/DOX nanogel showed a higher encapsulation efficiency (81.6 ± 1.2)% and thermo- and pH-responsiveness as well as redox-responsive in vitro release. These properties together with excellent environmentally sensitive properties make PND-BAC as an attractive candidate for application in drug nanocarriers for the targeted drug delivery of model payloads. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1195-1203, 2019.

Intelligent solar water evaporation (iSWE) was achieved with a thermally responsive and microstructured graphene/poly(N-isopropylacrylamide) (mG/PNIPAm) membrane. As the solar intensity varies, the water evaporation is tuned through reversible transformations of microstructures reminiscent of the stomatal opening and closing of leaves. Consequently, this mG/PNIPAm membrane displays a high water evaporation rate change (ΔWER) of 1.66 kg m-2 h-1 under weak sunlight (intensity

Composite materials consisting of nanoscale gold particles and protective polymer shells were designed and tested as catalysts in various chemical reactions. Initially, the systematic incorporation of multiple gold nanoparticles into a poly(N-isopropylacrylamide) particle was achieved by an in situ method under light irradiation. The degree of gold nanoparticle loading, along with the structural and morphological properties, was examined as a function of the amount of initial gold ions and reducing agent. As these gold nanoparticles were physically-embedded within the polymer particle in the absence of strong interfacial interactions between the gold nanoparticles and polymer matrix, the readily-accessible surface of the gold nanoparticles with a highly increased stability allowed for their use as recyclable catalysts in oxidation, reduction, and coupling reactions. Overall, the ability to integrate catalytically-active metal nanoparticles within polymer particles in situ allows for designing novel composite materials for multi-purpose catalytic systems.

Two different surface sulfonamide-functionalized poly(N-isopropylacrylamide)-based polymeric micelles were designed as pH-/temperature-responsive vehicles. Both sulfadimethoxine- and sulfamethazine-surface functionalized micelles were characterized to determine physicochemical properties, hydrodynamic diameters, zeta potentials, temperature-dependent size changes, and lower critical solution temperatures (LCST) in both pH 7.4 and 6.8 solutions (simulating both physiological and mild low pH conditions), and tested in the incorporation of a proof-of-concept hydrophobic antiproliferative drug, paclitaxel. Cellular uptake studies were conducted using bovine carotid endothelial cells and fluorescently labeled micelles to evaluate if there was enhanced cellular uptake of the micelles in a low pH environment. Both variations of micelles showed enhanced intracellular uptake under mildly acidic (pH 6.8) conditions at temperatures slightly above their LCST and minimal uptake at physiological (pH 7.4) conditions. Due to the less negative zeta potential of the sulfamethazine-surface micelles compared to sulfadimethoxine-surface micelles, and the proximity of their LCST to physiological temperature (37°C), the sulfamethazine variation was deemed more amenable for clinically relevant temperature and pH-stimulated applications. Nevertheless, we believe both polymeric micelle variations have the capacity to be implemented as an intracellular drug or gene delivery system in response to mildly acidic conditions. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1552-1560, 2018.

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 (T-c) of an aqueous Py-n-PNIPAM solution, determined by turbidimetry, was found to increase with the number-average molecular weight (M-n) 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 T-c, the solution cloud point, and T-m, 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. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 308-318

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.

Surface-initiated atom transfer radical polymerization (SI-ATRP) was used to graft poly(N-isopropylacrylamide) (PNIPAM) brush layers with a controllable thickness in the 10-nm range from silicon substrates. The rate of polymerization of N-isopropylacrylamide was tuned by the [Cu(II)]0/[Cu(I)]0 ratio between the deactivating and activating species. The polymer layer thickness was characterized by atomic force microscopy (AFM) and ellipsometry. PNIPAM layers with a dry thickness between 5.5 and 16 nm were obtained. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed that the chemical structure is PNIPAM brushes. Analysis of the AFM data showed that our procedure leads to polymer grafts in the "mushroom-to-brush" transition regime.

The tremendous reinforcing and pore-stabilizing effect of in-situ-formed nano-silica in a highly porous temperature-responsive poly (N-isopropylacrylamide) (PNIPA) matrix is demonstrated: A very weakly crosslinked semi-liquid hydrogel can be reinforced to the point that it displays a fast, extensive and nearly symmetrical temperature-responsiveness in combination with an acceptable modulus. In soft but solid porous PNIPA, only 0.6 wt.% of the nanofiller are sufficient to stabilize the pores against collapse upon deswelling, thus to enabling ultra-fast responsiveness. A spectacular effect is achieved with dried porous PNIPA (matrix is glassy, Tg = ca. 140 °C), which in case of optimal nano-SiO2 amounts can reswell in only 3 min. The key importance of efficient hydrogen bridging between PNIPA and SiO2 is demonstrated by comparing in-situ-formed nano-silica with similarly sized commercial Ludox particles, the surface of which is saturated with ammonia (for stabilization). Synthesis parameters like the amount of crosslinker and of nano-SiO2 were varied in a wide range, in order to achieve the fastest-possible responsiveness of the hydrogels in combination with a high modulus. The porosity, nano-SiO2 distribution, the moduli, the temperature-dependent swelling, as well as the swelling kinetics of the gels were determined as functions of contents of crosslinker and nano-SiO2.

Both water and methanol are good solvents for poly(N-isopropylacrylamide) (PNIPAM), while PNIPAM does not dissolve in their mixed solvents, this phenomenon is called cononsolvency. Cononsolvency is closely related to many phenomena in life but so far, its mechanism is still controversial. In this work, the dielectric behavior of PNIPAM methanol aqueous solution was studied in the frequency of 40Hz–40GHz. From lower frequency to higher frequency, four relaxations were found. They are, respectively, from global chain motion, local motion of backbone, motion of side chain group, and the dipole orientation of the solvent molecule. The solvent dependence of dielectric parameters for the chain motion implied that the PNIPAM chain has undergone the coil-globule-coil transition. Dielectric analysis to microwave frequency showed that the volume of the bound solvent units on PNIPAM chain increases with the increasing methanol concentration, which suggested that the structure of solvation units bound on PNIPAM side chains undergo a changing process experience from water to water-methanol cluster to the ternary methanol cluster. This work reveals the structure and dynamics of the PNIPAM chain and the solvent unit that involved in the solvation of PNIPAM, and provides some new insight into the cononsolvency phenomenon. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

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.

In this study, inorganic/organic composites containing poly (N-isopropylacrylamide) coated core-shell SiO2 microspheres were prepared via surface-initiated atom transfer radical polymerization (ATRP). The thermal responsive polymer, N-isopropylacrylamide was treated with methanol, water and CuBr/CuBr2/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) at room temperature to form PNIPAM@SiO2 microspheres. The as-prepared PNIPAM@SiO2 microspheres were characterized by FT-IR, TGA, XPS, SEM, TEM analyses. Hemoglobin (Hb) was immobilized onto the surfaces of PNIPAM@SiO2 microspheres via hydrophobic and π-π stacking interactions. The as-prepared Hb/PNIPAM@SiO2 electrode exhibits well-defined redox peak at a formal potential of −0.38 V, validating the direct electrochemistry of Hb. The Hb immobilized composite film retained its bioelectroactivity without any significant loss of catalytic activity. The modified electrode detects H2O2 over a wide linear concentration range (0.1 μM to 333 μM) with a detection limit of 0.07 μM. This modified electrode also successfully detects H2O2 from food and disinfectant samples with appreciable recovery values, validating its practicality. We believe that PNIPAM@SiO2 composite has great potential to be used in the detection of H2O2 and development of other enzyme based biosensors.

Four kinds of poly(N-isopropylacrylamide)-grafted silicas with different grafting ratios and the same grafting density were prepared by atom transfer radical polymerization. The chemical groups in the stationary phase was verified by FTIR spectroscopy, and the content of elements was measured by elemental analysis. The grafting ratio of thermoresponsive chromatographic materials was measured by thermogravimetric analysis and was 2.36-21.10% mg/m2 . The retention behaviors of the stationary phase with different grafting ratios were evaluated by separating five kinds of steroids and ten kinds of different hydrophobic properties compounds. With the increase in grafting ratio, the retention time of analytes was prolonged in high-performance liquid chromatography. The results showed that grafting ratio had a significant influence on the separation effect under the same grafting density. And the optimal grafting ratio of poly(N-isopropylacrylamide) was 5.81-13.15%.

Summary Amino-terminated poly(N-isopropylacrylamide) (PNIPAM-NH2) was synthesized by free-radical polymerization in water by using the redox pair potassium persulfate/2-aminoethanethiol hydrochloride (KPS/AET.HCl) in a glove box under N2(g) atmosphere. PNIPAM-NH2 was then used to produce graft copolymers with carboxymethylcellulose (CMC) in water by applying a water-soluble carbodiimide and N-hydroxysuccinimide as activators. The samples were characterized by infrared spectroscopy and the thermal behaviour on solid state was investigated by thermogravimetry. Also, the rheological behaviour of the copolymers at 25 and 60 °C was evaluated in water at 3 and 7 g/L. Contrary to CMC and PNIPAM-NH2, which had only one DTG peak, the thermal decomposition of the graft copolymers occurred at two steps, being the first DTG peak higher and second one lower than the corresponding precursors. Thermoassociative behaviour in water for CMC-g-PNIPAM graft copolymers depend on the amount of chain transfer agent used for the PNIPAM-NH2 synthesis. Thermothickening effect occurred for the copolymer that had PNIPAM-NH2 prepared with lower AET.HCl content, at a polymer concentration of 7 g/L, which is much lower than the concentrations previously reported in literature for graft copolymers with poly(N-isopropylacrylamide).

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.

Providing a controllable and definable three-dimensional (3D) microenvironment for chondrogenic differentiation of mesenchymal stem cells (MSCs) remains a great challenge for cartilage tissue engineering. In this work, poly(N-isopropylacrylamide) (PNIPAAm) polymers with the degrees of polymerization of 100 and 400 (NI100 and NI400) were prepared and the polymer solutions were introduced into the preprepared chitosan porous scaffolds (CS) to form hybrids (CSNI100 and CSNI400, respectively). SEM images indicated that the PNIPAAm gel partially occupied chitosan pores while the interconnected porous structure of chitosan was preserved. MSCs were incorporated within the hybrid and cell proliferation and chondrogenic differentiation were monitored. After 7-day incubation of the cell-laden constructs in a growth medium, the cell viability in CSNI100 and CSNI400 were 54 and 108% higher than that in CS alone, respectively. Glycosaminoglycan and total collagen contents increased 2.6- and 2.5-fold after 28-day culture of cell-laden CSNI400 in the chondrogenic medium. These results suggest that the hybrid structure composed of the chitosan porous scaffold and the well-defined PNIPAAm hydrogel, in particular CSNI400, is suitable for 3D stem cell culture and cartilage tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2764-2774, 2016.

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

A telechelic thermoresponsive polymer, α-amino-ω-thiol-poly(N-isopropylacrylamide) (H2N-PNiPAM-SH), is used as the polymeric glue to assemble gold nanoparticles (AuNPs) around gold nanorods (AuNRs) into a satellite structure. Prepared by reversible addition-fragmentation chain transfer polymerization followed by hydrazinolysis, H2N-PNiPAM-SH is able to interlink the two types of the gold building blocks with the thiol-end grafting on AuNRs and the amine-end coordinating on the AuNP surface. The density of the grafted AuNPs on AuNRs can be tuned by adjusting the molar ratio between AuNPs and AuNRs in the feed. The resulted satellite-like assembly exhibits unique optical property that was responsive to temperature change.

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.

As a kind of temperature-responsive hydrogel, polystyrene-co-poly(N-isopropylacrylamide)/poly(N-isopropylacrylamide) (PS-co-PNIPAM/PNIPAM) core-shell nanoparticles prepared by two-step copolymerization are widely studied and used because of their specific structures and properties. Unlike most reports about the steady stability of PS-co-PNIPAM/PNIPAM core-shell nanoparticle hydrogel emulsion, in this work, the PS-co-PNIPAM/PNIPAM core-shell nanoparticle hydrogel emulsion (symbolized as PS/PNIPAM hydrogel emulsion), which is prepared after the second step of synthesis and without washing out a large number of PNIPAM polymer segments, shows a reversible temperature-dependent sol-gel transition characteristic during the temperature range of 34-80 °C. The PS/PNIPAM hydrogel emulsion is a normal solution at room temperature, and it changes from a sol to a gel statue when the temperature approaches up to low critical solution temperature (LCST). As the temperature continues to increase, the gel (core-shell nanoparticles as the crosslinkers and the linear PNIPAM chain as the 3D gel network) of the PS/PNIPAM hydrogel emulsion gradually shrinks and drains linearly. Compared with most crosslinked hydrogels, the hydrogel here can be arbitrarily changed in shape according to use needs, which is convenient for use, transportation, and storage. Here a new route is provided for the preparation of a PS/PNIPAM core-shell hydrogel nanoparticle system, as well as a new supramolecular crosslinking sol-gel system for application in biomedical materials, sensors, biological separation, drug release, macromolecular adsorption, and purification.