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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 A thermo-sensitive graphene-based hybrid is prepared by the electrostatic interactions between the poly(diallyldimethylammonium chloride)-co-poly(N- isopropylacrylamide) (PDDA-co-PNIPAM) and graphene oxide (GO). The electrostatic interaction, chemical structure, morphology and thermo-sensibility of the hybrid are systematically characterized, which have been manifested that the electrostatic interaction between the PDDA-co-PNIPAM and GO is strong, and the employment of the cationic PDDA-co-PNIPAM results into a well distributed polymer nanoparticles on the GO sheets. The new PDDA-co-PNIPAM/GO hybrid has good dispersity in some polar solvents. Notably, the phase transition of this hybrid can be reversibly modulated by temperature in water, which can be applied as thermo-switch material for the adsorption and separation of the organic pigments in aqueous solutions. Graphical abstract Image Highlights • A thermo-sensitive graphene hybrid is prepared by electrostatic interaction. • The hybrid has good thermo-sensibility. • The hybrid can be applied for the adsorption and separation of organic pigments. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermo- and pH sensitive supramolecular micelles were formed based on host-guest recognition. • The drug loaded supramolecular micelles exhibited higher anti-cancer activity than free DOX. • Release of DOX was accelerated at acidic pH and temperatures above the LCST. Abstract In this paper, temperature and pH dual-sensitive supramolecular micelles were constructed from star polymer β-cyclodextrin-poly(N -isopropylacrylamide) (β-CD-PNIPAM) and benzimidazole terminated poly(ε-caprolactone) (BM-PCL). The supramolecular micelles were formed based on the reversible host-guest recognition between β-CD and BM. The size of supramolecular micelles was about 50–100 nm and the LCST was about 30.5 ℃. The drug loading efficiency of supramolecular micelles for DOX was high due to the hydrophobic micelles core of PCL and hydrophobic cavity of β-CD. The release of drugs from supramolecular micelles was suppressed at neutral solution and room temperature but accelerated at acidic solution and 37 ℃. The drug loaded supramolecular micelles exhibited higher anti-cancer activity than free drugs. These temperature and pH dual-sensitive supramolecular micelles might possess potential applications for anticancer drug delivery. [ABSTRACT FROM AUTHOR]

Highlights • LCST phase transition kinetics of PNIPAM solutions characterized by DSC and DLS. • Large activation energy (E α) and pre-exponential factor (A α) illustrated. • Both E α and A α dependent on temperature. • Cooperatively breaking multiple hydrogen bonds occurs in phase transition. • Phase transition kinetics of PNIPAM solutions obeys nucleation and growth models. Abstract LCST phase transition kinetics of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions was studied by using non-isothermal differential scanning calorimeter (DSC) and isothermal dynamic light scattering (DLS) techniques. The DSC data obtained from 5 and 10 wt% PNIPAM solutions were used in isoconversional kinetics analysis. The resultant large activation energy (E α) and pre-exponential factor indicated that the phase transition occurred by cooperatively breaking multiple hydrogen bonds. E α decreased with increasing temperature approximately in a hyperbola form. Theoretical nucleation and growth models were used to adequately describe the temperature dependent E α. Furthermore, the phase transition process obeyed Avrami–Erofeev nucleation and growth models. As to the 0.05 wt% PNIPAM solution using the isothermal DLS technique, the reaction rate constant was determined at different temperatures, and the Avrami–Arofeev nucleation and growth models adopted to predict the phase transition process. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Isotactic poly (N -isopropylacrylamides) (PNIPAMs) with a wide range of tacticity exhibit upper critical solution temperature (USCT) type phase transition in an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSI]). The phase transition temperature becomes higher with increasing isotacticity, since more amide groups are aligned along the same side of backbones to form stronger intramolecular hydrogen bonding. Phase diagrams of highly isotactic PNIPAMs show prominent UCST peaks at low concentrations, similar with the typical polymer solution, which implies the dissolution of isotactic PNIPAMs is dominated by the entropy-driven effect. The increase in phase transition temperature with molecular weight is also from the entropic reason. The phenomena above reveal that the phase transition behavior of PNIPAMs in ionic liquids is highly influenced by tacticity effect. Graphical abstract Left: The phase separation temperature as a function of tacticity for 5% PNIPAM in [BMIM][TFSI] solutionsRight: The phase diagram for PNIPAM with 78–79% meso-diad content in [BMIM][TFSI] solutionsCodes: m represents PNIPAMs with molecular weight of 34900–43600 g/mol, while HMWm represents PNIPAMs with molecular weight of 60200–85700 g/mol. Image 1 Highlights • A UCST phase transition is observed in PNIPAM/ionic liquid mixture. • The transition temperature increases with increasing isotacticity. • The phase diagram exhibits a prominent UCST peak for isotactic PNIPAM. • The transition temperature increases with increasing molecular weight. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis procedure of universal hydrogel matrix for controlled implementation of metal sorbents. • Highly efficient silver removal by a "magnetic sponge" (pNIPA / magnetite thermoresponsive ferrogel). • Silver adsorption on magnetite in pNIPA ferrogel is described by the Freundlich model. • The presence of gel matrix increases efficiency of silver sorption on magnetite. Abstract A new method for metal removal from waste water samples using thermoresponsive ferrogel sorbents is presented. For this purpose a novel method of synthesising composite materials made from a polymeric hydrogel and sorbent materials was developed. The key aspect of synthetic work was the selection of a polymer matrix for homogeneous implementation of a sorbent material. Poly(N -isopropylacrylamide) (pNIPA) hydrogel, characterised by discontinuous volume phase transition induced by the temperature change, was selected as the polymeric matrix. The synthesised materials were applied for the removal of silver cations in aqueous media. The phenomenon of volume phase transition of pNIPA gels allowed one to absorb solution containing examined metal into the gel matrix with the sorbent material and effectively separate polymer phase from the solution depleted of metal after the phase transition was completed. Magnetite (Fe 3 O 4) acted as a sorbent in designing of the composite material. Magnetite particles implemented in the pNIPA gel matrix form a ferrogel, which can be fully controlled using a magnetic field. The maximum adsorption capacity was estimated experimentally to be 13.6 mg Ag / g Fe 3 O 4. The number was verified by the kinetic data. The proposed mechanism of silver sorption on magnetite postulates a chemical deposition of metallic silver followed by intensified diffusion of silver cations to magnetite grains. The ferrogel sorption system is stable from pH 5 to 8 and can be easily restored via the swelling – shrinking cycling. The sorption procedure was validated for the real samples containing excessive amount of copper ions. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop thermo-sensitive in situ gelling formulation of KCL based on poly(N-isopropylacrylamide)/hyaluronic acid. The prepared preparations were characterized for in vitro gelation, drug release and antifungal activity. In this study, drug content of prepared gels was found to be in the range of 91-96%. The pH value was in the range of 6.0-7.5. By measuring the gelation temperature of the prepared PN-HA thermogelling solutions, it was 33 °C. In vitro release showed that the release of KCL from in situ gels was moderate without burst effects. The KCL PN-HA in situ gels were well-tolerated by the rabbits, and no macroscopic signs of irritation, redness, or other toxic effects were observed. From in vivo antimicrobial study, KCL PN-HA in situ gels may be concluded to have a better cure percent in clinical profile and negative growth of Candida albicans in microbiological test. Therefore, this new formulation could prove to be a novel ocular dosage form able to prolong the residence time and to control the release of drug when administered into the eye. [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]

This paper presents an in-depth study of the surface modification of polyethylene terephthalate fabric (PET) with non-thermal plasma and temperature- and pH-responsive nanogel (PNCS) to impart smart thermoregulation properties. To increase the adsorption of the PNCS nanogel onto the PET, ammonia and oxygen plasma and a combination of both plasma gases were used. Chemical changes caused by the plasma treatment were investigated using X-ray photoelectron spectroscopy (XPS), morphological changes were determined using scanning electron microscopy (SEM) and the swelling and de-swelling ability was determined by measuring the moisture content at 20 and 40 °C. The greatest deposition of the PNCS nanogel, with unimpaired swelling ability, was found on the oxygen-plasma-treated samples, as they had the highest O/C ratio. Meanwhile, the least promising results were found for the samples treated with a combination of oxygen and ammonia plasma, where the highest concentration of nitrogen was present on the fibre surface. Since the treatment with oxygen plasma proved to be the most effective method, different exposure times to the oxygen plasma, namely, 10, 30 and 60 s, were studied in the second part of this study. The optimal oxygen plasma treatment time was found to be 30 s, where the greatest deposition and unhindered swelling/de-swelling ability of the PNCS nanogel on the PET fabric was achieved. [ABSTRACT FROM AUTHOR]

A series of polymer hydrogel bilayers that show temperature-sensitive deformations were prepared and their temperature-responsive gripping ability was tested. One layer was an interpenetrating polymer network (IPN) of poly(N-isopropylacrylamide) (PNIPAAm) and poly(vinyl alcohol) (PVA), and the other layer was crosslinked PVA. The IPN layer was prepared by absorbing N-isopropylacrylamide monomer solution into the crosslinked PVA film and then polymerizing it by UV irradiation. The structure, swelling properties, and mechanical properties of the IPN and PVA films were investigated. The interpenetration of PNIPAAm appeared to restrict the crystallization of PVA, which affected the swelling and mechanical properties of IPN. The bending deformation of the bilayer fabricated by attaching the IPN and PVA films was observed in 25 °C and 37 °C water. The bending diameter and bending direction could be controlled by combining IPN and PVA films with different degree of crosslinking. The gripping test using starfish-shaped bilayers demonstrated mechanical robustness as well as temperature-sensitivity by lifting and releasing an object much heavier than itself in 25 °C and 37 °C water. [ABSTRACT FROM AUTHOR]

In the present work, PNIPAM-DNA films were fabricated on the surface of electrodes by GOD-induced radical polymerization, where PNIPAM is poly(N-isopropylacrylamide), DNA represents natural DNA from salmon testes, and GOD is glucose oxidase. The prepared film electrodes demonstrated reversible temperature-, SO 4 2− -, and pH-switched cyclic voltammetry (CV) and electrochemiluminescence (ECL) behaviors toward tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy) 3 2+ ) in solution. Particularly, both CV and ECL signals at 1.15 V belonging to Ru(bpy) 3 2+ were significantly amplified by the electrocatalysis of DNA in the films. Moreover, the addition of ferrocenemethanol (FcMeOH) into the solution led to the substantial quenching of the ECL signal of the system and produced a new CV peak pair at 0.35 V. Based upon these experiments, a 4-input/7-output logic gate system was successfully built, which also lead to a 2-to-1 encoder and a 1-to-2 decoder. On the same platform, a more complicated logic device, a half-adder, was also constructed. The present system combined electrocatalysis of natural DNA mediated by Ru(bpy) 3 2+ and multiple stimuli-responsive PNIPAM-DNA films together with simultaneously obtained CV and ECL signals as outputs, leading to the development of novel types of biocomputing systems. [ABSTRACT FROM AUTHOR]

The preparation of thermo-responsive polymeric porous membranes with well-defined morphology and high mechanical strength is still a great challenge. In our work, high strength and self-supporting polysulfone/poly(N-isopropylacrylamide) (PSf/PNIPAm) membranes with tuning wormlike network morphology and thermo-responsibility were successfully prepared via the approach combining in situ cross-linking polymerization with vapor-liquid nonsolvent induced phase separation (V-LIPS). With increasing the NIPAm concentration and the exposure time during the VIPS process, the wormlike networks self-assembled on the membrane surfaces, and their diameter rapidly increased to ~ 63 nm in 60 s. As a result, the pore size/porosity of the membranes increased and the membrane hydrophilicity improved, leading to high water flux with a maximum value of ~ 222 L m −2 h −1 at 23 °C. Furthermore, the permselectivity of the fabricated membranes exhibited strong and fully reversible thermo-responsive character as feed temperature ranged from 23 to 50 °C, in which the thermo-responsive coefficient was as high as ~ 3.7 after viscosity correction and the size distribution of silver nanoparticles in the filtrates narrowed down sharply. In addition, the fabricated membranes with wormlike network morphology exhibited the maximum tensile strength of ~ 6 MPa and elongation at break of ~ 33%, which are much higher than the block copolymers based membranes with the similar morphology. The approach provided here opens a new and simple way to prepare high strength PSf membranes with tuning network morphology and thermo-responsive permselectivity in large scale, and which is expected to be expanded to fabricate other polymeric microporous membranes. [ABSTRACT FROM AUTHOR]

To prepare temperature and pH dual-responsive drug delivery systems, the thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAAm) was first synthesized by free-radical polymerization. It was then co-dissolved with the pH-sensitive polymer Eudragit® L100-55 (EL100-55) and processed into fibers using electrospinning. Ketoprofen (KET), a model drug, was also incorporated into the composite fibers, and fibers based on a single polymer additionally prepared. The fibers had smooth cylindrical morphologies, and no obvious phase separation could be seen. Using X-ray diffraction, KET was determined to be present in the amorphous state in the fiber matrix. FTIR spectroscopy also indicated the successful incorporation of amorphous KET in the fibers. In vitro drug release studies in media at different pH (4.5 or 7.4) or temperature (25 and 37 °C) showed that the release of KET from the blend PNIPAAm/EL100-55 fibers was dependent both on environmental temperature and pH, reflecting the dual-responsive properties of the fibers. The MTT assay was used to explore the biocompatibility of the PNIPAAm/EL100-55 composite fibers towards L929 fibroblasts. Viability was always found to be >80%, even at polymer concentrations of 100 mg/L. Therefore, the fibers prepared here could lead to the development of multi-responsive materials for drug delivery and tissue engineering. [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]

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We prepared thermoresponsive hydrogels by mixing poly(N-isopropylacrylamide) (PNIPAAm) derivatives as the main chain components, octa-arm polyethylene glycol (PEG) as a crosslinker, and the Arg-Gly-Asp-Ser (RGDS) peptides as cell adhesion units. Human bone marrowderived mesenchymal stem cells (hbmMSCs) were cultured on the hydrogels. The PNIPAAm gel prepared by the post-crosslinking gelation method was revealed to be cytocompatible and showed temperature-dependent changes in mechanical properties. Repeated changes in the swelling ratio of the PNIPAAm gel affected the shape of the hbmMSCs. With respect to both cytocompatibility and reversibility of changes in mechanical properties, the PNIPAAm gel system could be potentially useful for the analysis of cell mechanobiology. [ABSTRACT FROM AUTHOR]

The thermoresponsive poly(N-isopropylacrylamide) and matching thermal-liftoff method are widely employed for cell culture. There is already growing evidence that this special cell culture system not only provides an appropriate growth environment for anchorage-dependent cells at physiologic conditions, but also supports mild and efficient cell harvesting by cooling treatment. This review elaborates the internal and external factors affecting two-dimensional surface thermosensitivity and cell behavior, and then briefly discusses three-dimensional cell culture systems involved in thermosensitive microcarriers, scaffolds, hydrogels, and hollow fiber membranes, and finally presents their potential applications including large-scale cell expansion as well as tissue repair and reconstruction. [ABSTRACT FROM AUTHOR]

Continuing efforts to develop novel smart materials are anticipated to upgrade the quality of life of humans. Thermo-responsive poly(N-isopropylacrylamide) and glucose-responsive phenylboronic acid--typical representatives--are often integrated as multi-stimuli-sensitive materials, but few are available for side-by-side comparisons with their properties. In this study, both copolymers bearing N-isopropylacrylamide (NIPAAm), with or without 3-acrylamidophenylboronic acid (AAPBA), were synthesized by free radical polymerization, and characterized by Fourier transform infrared spectrometry, nuclear magnetic resonance hydrogen spectroscopy and gel permeation chromatography. Dynamic light scattering was used to analyze and compare the responsive behaviors of the copolymers in different aqueous solutions. Atomic force microscopy was also employed to investigate the apparent morphology changes with particle sizes. The results demonstrated that the introduction of NIPAAm endowed the composite materials with thermosensitivity, whereas the addition of AAPBA lowered the molecular weight of the copolymers, intensified the intermolecular aggregation of the nanoparticles, reduced the lower critical solution temperature (LCST) of the composites, and accordingly allowed the copolymers to respond to glucose. It was also concluded that the responding of smart copolymers to operating parameters can be activated only under special conditions, and copolymer dimension and conformation were affected by inter/intramolecular interactions. [ABSTRACT FROM AUTHOR]

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] Poly(N -isopropylacrylamide) (PNIPAM) is a unique stimuli-responsive material that exhibits a lower critical solution temperature (LCST). Owing to this characteristic temperature-dependent behavior, PNIPAM has found extensive utilization as an active material in various applications, including sensors, drug delivery, and cellular imaging. Herein, we demonstrate temperature-directed fluorescent switchable nanoparticles based on poly(3-octylthiophene-2,5-diyl) (P3OT) nanoaggregate-embedded PNIPAM nanogel composites (POPNs) featuring different crosslinker contents. The amount of P3OT loading in the nanogel composites can be gradually controlled by varying the crosslinking density of the PNIPAM matrix; this may be attributable to the efficient entrapment of P3OT nanoaggregates in case of a dense polymeric network with the increase in crosslinking density. POPNs exhibit dramatic temperature-dependent fluorescence enhancement (by a factor of 2.11). This is based on the environmental changes affecting fluorescent P3OT chains at temperatures below and above the LCST of the PNIPAM matrix. Based on this temperature-directed fluorescent switching capability, POPN could find potential applications in various fields, including biomedical imaging and sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV-induced photochromic ink was printed onto paper for anticounterfeiting purposes. • Rare-earth strontium aluminum oxide was encapsulated into PNIPAM nanoparticles. • LAA particles had diameters of 3–8 nm; LAA@PNIPAM had diameters of 80–175 nm. • Colorless printed films changed color to green (519 nm) under ultraviolet light. • Printed sheets displayed photostability and high mechanical reliability. Ultraviolet-induced fluorescence has proven an intriguing encoding strategy to increase the effectiveness of anti-counterfeiting measures for commercial materials. Recently, fluorescent inks showed severe disadvantages such as high costs, poor durability, and low efficiency. In this context, we present the development of a security encoding ink based on poly(N -isopropylacrylamide) (PNIPAM) nanoparticles immobilized with lanthanide-activated aluminate (LAA) nanoparticles (NPs), which can be used for advanced anticounterfeiting applications. LAA-encapsulated PNIPAM nanoparticles were prepared. Authentication inks based on LAA@PNIPAM nanoparticles provide a unique combination of photostability and endurance. Therefore, the composite ink containing LAA@PNIPAM nanoparticles exhibited strong reversible and photostable UV-induced fluorescence. Different composite inks with distinct emission properties were prepared by varying the concentration of LAA@PNIPAM nanoparticles. Paper sheets printed with a homogenous layer of the composite inks displayed a transparent appearance under visible lighting but became green beneath ultraviolet illumination, as proven by photoluminescence and CIE Lab tests. Using transmission electron microscopic (TEM) analysis, the morphological study of LAA particles displayed diameters of 3–8 nm, whereas LAA@PNIPAM nanoparticles displayed diameters in the range of 80–175 nm. Multiple methods were utilized to examine both structure and elemental composition of the fluorescent prints. The ink rheology and mechanical properties of prints were tested. The emission and excitation wavelength were detected at 519 (green color) and 365 nm (colorless), respectively. The present smart ink can be reported as a highly efficient technology for the production of anticounterfeiting commercial products. [ABSTRACT FROM AUTHOR]

When ingesting a drug on its own or injecting it directly into tissue, its concentration increases immediately within the body, which often exacerbates the side effects and increases its toxicity. To solve this problem, we synthesized the thermally reactive polymer poly(N-isopropylacrylamide) (PNIPAM) using reversible addition−fragmentation chain transfer (RAFT) polymerization and prepared nanocarriers by binding PNIPAM to gold nanorods (GRs), with the anticancer agent doxorubicin (DOX) used as a model drug. PNIPAM changes from hydrophilic to hydrophobic at temperatures above its lower critical solution temperature, which represents a coil-to-globule volume phase transition. Because GRs absorb near-infrared (NIR) laser light and emit energy, PNIPAM aggregation occurs when the synthesized PNIPAM/GR are subjected to an NIR laser, and the temperature of the GRs rises. Using this principle, DOX was combined with the PNIPAM/GR complex, and the resulting anticancer effects with and without laser treatment were observed in Hela and MDA-MB-231 cells. In our proposed complex, the GR binding rate of PNIPAM reached 20% and the DOX binding rate reached 15%. The release profile of the drug following laser irradiation was determined using a drug release test and confocal microscopy imaging. It was subsequently confirmed that the release of the drug is higher at higher temperatures, especially with laser treatment. The proposed combination of temperature-reactive polymers and gold nanostructures shows promise for future research into controlled drug release.

We examined the flocculation of suspended particles using a thermosensitive polymer which undergoes a reversible hydrophilic/hydrophobic transition when heating or cooling its aqueous solution. As a thermosensitive polymer poly(N-isopropylacrylamide) (polyNIPAM), whose transition temperature is about 32°C, was used. Flocculation experiments were performed by the jar test using kaolin suspension. In the case of operating temperature lower than the transition temperature of poly-NIPAM, there was an optimum polymer dosage, and by dosing excessively kaolin particles were dispersed stably in the same manner as conventional polymeric flocculants. However, floc formation was observed by heating the suspension above the transition temperature under the excess polymer dosage. Furthermore, by cooling the floc-containing suspension down to below the transition temperature again, the flocs were disorganized to the particles. These phenomena show that the floc formation caused by heating to above the transition temperature is due to the hydrophobic interaction of polyNIPAM molecules adsorbed on the particles.† This report was originally printed in Kagaku Kogaku Ronbunshu, 26(5), 734-737 (2000) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Chemical Engineers, Japan.