Temperature‐sensitive poly(N‐tert‐butylacrylamide‐co‐acrylamide) hydrogels bonded on cotton fabrics by coating technique

Different from the conventional method of developing stimuli‐sensitive textiles by graft copolymerization of environmental responsive polymers onto the fabric, the coating technique was applied to bond temperature‐sensitive hydrogels with cotton fabric through chemical covalent in our work. A temperature‐sensitive linear copolymer of N‐tert‐butylacrylamide (NTBA) and acrylamide (AAm) was prepared in methanol. Then, the cotton fabrics were coated using an aqueous solution of this copolymer containing 1,2,3,4‐butanetertracarboxylic acid as a crosslinker and sodium hypophosphite (SHP) as a catalyst, followed by drying and curing. The surface of the cotton fabrics was bonded on more or less coatings of poly (NTBA‐co‐AAm) hydrogels, as verified by Fourier transform infrared spectroscopy and scanning electron microscopy images. The poly(NTBA‐co‐AAm) hydrogels‐coated fabrics exhibited temperature sensitive, and the temperature interval of the deswelling transition was higher than lower critical solution temperature of linear copolymer solution. The coated fabrics presented good water‐impermeable ability because of the swelling of hydrogels bonded, especially when the add‐on was as high as 14.14%. Environmental scanning electron microscopy images revealed that coating hydrogels swelled and covered on the surface as a barrier to prevent water from penetrating once the coated fabric came into contact with water. The findings demonstrate that the temperature‐sensitive hydrogels can be covalently bonded on the cotton fabrics by coating technique and the coated fabrics have potential on immersion fabrics. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Two‐step synthesis and properties of a magnetic‐field‐sensitive modified maltodextrin‐based hydrogel

A magnetic‐field‐sensitive modified maltodextrin‐based hydrogel (ferrogel) was synthesized. Fourier transform infrared and ¹³C‐CP/MAS NMR spectral analyses confirmed the efficiency of the gelling process. X‐ray diffraction analysis revealed the appearance of new crystalline planes in the hydrogel diffractograms after embedding of magnetite nanoparticles. Magnetization curves and Mössbauer analysis revealed that the magnetic hydrogel has a high lattice strain due to bonded iron atom covalence. Moreover, some magnetite molecules embedded in the hydrogel ensure a degree of paramagnetism and iron atoms exhibiting oxidation states alternating between 2 and 3 in the final material. Scanning electron microscopy and energy‐dispersive X‐ray analysis revealed that no phase separation occurred between the magnetite nanoparticles and crosslinked hydrogel, indicating excellent dispersion throughout the hydrogel. Moreover, the average pore sizes decreased on increasing the amount of magnetite inside the polymer network. The results of compression stress versus strain revealed that the elasticity of the magnetic hydrogel was increased on increasing the amount of magnetite nanoparticles. Finally, kinetic studies revealed that the diffusion mechanism of water in the hydrogel is driven by anomalous release with a tendency towards the occurrence of macromolecular relaxation. Copyright © 2011 Society of Chemical Industry     

Preparation and Swelling Properties of Temperature‐Sensitive Semi‐Interpenetrating Polymer Networks Composed of Poly[(N‐tert‐butylacrylamide)‐co‐acrylamide] and Hydroxypropyl Cellulose

Summary: Temperature‐responsive hydrogels based on linear HPC and crosslinked P(NTBA‐co‐AAm) were prepared by the semi‐IPN technique. The structure of these semi‐IPN hydrogels was investigated by FT‐IR spectroscopy. An increase in normalized band ratios (A₂₉₈₀/A₁₆₆₅) was observed with increasing HPC content in the initial mixture. The swelling kinetics and water transport mechanism of these semi‐IPN hydrogels were examined and their temperature responsive behaviors were also investigated by measuring equilibrium swelling ratios and pulsatile swelling experiments. The results showed that these semi‐IPN hydrogels underwent a volume phase transition between 18 and 22 °C irrespective of the amounts of MBAAm and HPC. However, below the volume phase transition temperature, their equilibrium swelling ratios were affected by the amount of MBAAm and HPC. The pulsatile swelling experiments indicated that the lower the MBAAm and the higher HPC contents in semi‐IPN hydrogels the faster the response rate temperature change.

Equilibrium swelling ratios of the semi‐IPN P(NTBA‐co‐AAm)/HPC hydrogels in water shown as a function of temperature.     

Environmentally sensitive hydrogels: N‐isopropyl acrylamide/Acrylamide/ Mono‐, Di‐, Tricarboxylic acid crosslinked polymers

Environmentally sensitive hydrogels responsive to various stimuli such as temperature, pH, ionic strength of the medium and the solvent were prepared by using N‐isopropyl acrylamide (NIPAM), acrylamide (AAm) and monomers that have various number of carboxylic acid (XA) functionality using N,N′‐methylene bisacrylamide (Bis) as crosslinker. Hydrogels were prepared via free radical polymerization reaction in aqueous solution. P(NIPAAm‐co‐AAm) and p(NIPAAm‐co‐AAm)/XA hydrogels that contain monoprotic crotonic acid (CA) exhibit a lover critical solution temperature (LCST) at 28°C, whereas p(NIPAAm‐co‐AAm)/IA (IA:itaconic acid), and P(NIPAAm‐co‐AAm)/ACA (ACA:acotonic acid) hydrogels exhibit a lover critical solution temperature at 30.7°C and 34.4°C, respectively. Spectroscopic and thermal analyses were performed for the structural and thermal characterizations of the prepared hydrogel. The swelling experiments as equilibrium swelling percentages by gravimetrically were carried out in different solvents, at different solutions temperature, pH, and ionic strengths to determine their effects on swelling characteristic of hydrogels. POLYM. ENG. SCI., 55:843–851, 2015. © 2014 Society of Plastics Engineers     

The studies on the stimuli‐response of poly (N,N‐dimethylamino ethyl methacrylate/acrylic acid‐co‐acrylamide) complex hydrogel under DC electric field

A polyelectrolyte complex hydrogel, poly (N,N‐dimethylaminoethyl methacrylate/acrylic acid‐co‐acrylamide) hydrogel designed as PDMEAA, was prepared by the free radical copolymerization in aqueous solutions. Without chemical crosslinker, PDMEAA hydrogel network was formed by electrostatic attraction of the proton‐transfer between acrylic acid and N,N‐dimethylamino ethyl methacrylate. Since the electrostatic attraction could be weakened by the application of electric field, PDMEAA hydrogel was decomposed under contacted electric field. Various factors such as gel composition, the species and concentration of electrolytes, voltage, and the experimental set‐ups, could effect the decomposing process of PDMEAA hydrogel. In CaCl₂ and MgCl₂ solutions, PDMEAA hydrogel had no change under electric field. And in high concentration of NaCl and Na₂SO₄ solutions, PDMEAA hydrogel has been eroded linearly with the increasing time applied electric field. In low concentration of NaCl and Na₂SO₄ solutions, however, a swelling process was found before the erosion. The stimuli‐responsive mechanism was investigated through scanning electron microscope (SEM) and gel permeation chromatography (GPC). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dual pH‐ and thermal‐responsive nanocomposite hydrogels for controllable delivery of hydrophobic drug baicalein

Hydrogels have been widely used as mild biomaterials due to their bio‐affinity, high drug loading capability and controllable release profiles. However, hydrogel‐based carriers are greatly limited for the delivery of hydrophobic payloads due to the lack of hydrophobic binding sites. Herein, nano‐liposome micelles were embedded in semi‐interpenetrating poly[(N‐isopropylacrylamide)‐co‐chitosan] (PNIPAAm‐co‐CS) and poly[(N‐isopropylacrylamide)‐co‐(sodium alginate)] (PNIPAAm‐co‐SA) hydrogels which were responsive to both temperature and pH, thereby establishing tunable nanocomposite hydrogel delivery systems. Nano‐micelles formed via the self‐assembly of phospholipid could serve as the link between hydrophobic drug and hydrophilic hydrogel due to their special amphiphilic structure. The results of transmission and scanning electron microscopies and infrared spectroscopy showed that the porous hydrogels were successfully fabricated and the liposomes encapsulated with baicalein could be well contained in the network. In addition, the experimental results of response release in vitro revealed that the smart hydrogels showed different degree of sensitiveness under different pH and temperature stimuli. The results of the study demonstrate that combining PNIPAAm‐co‐SA and PNIPAAm‐co‐CS hydrogels with liposomes encapsulated with hydrophobic drugs is a feasible method for hydrophobic drug delivery and have potential application prospects in the medical field. © 2018 Society of Chemical Industry     

Synthesis and characterization of a novel stimuli‐responsive magnetite nanohydrogel based on poly(ethylene glycol) and poly(N‐isopropylacrylamide) as drug carrier

A novel stimuli‐responsive magnetite nanohydrogel (MNHG), namely [poly(ethylene glycol)‐block‐poly(N‐isopropylacrylamide‐co‐maleic anhydride)₂]‐graft‐poly(ethylene glycol)/Fe₃O₄ [PEG‐b‐(PNIPAAm‐co‐PMA)₂]‐g‐PEG/Fe₃O₄, was successfully developed. For this purpose, NIPAAm and MA monomers were block copolymerized onto PEG‐based macroinitiator through atom transfer radical polymerization technique to produce PEG‐b‐(PNIPAAm‐co‐PMA)₂. The synthesized Y‐shaped terpolymer was crosslinked through the esterification of maleic anhydride units using PEG chains to afford a hydrogel. Afterward, magnetite nanoparticles were incorporated into the synthesized hydrogel through the physical interactions. The chemical structures of all synthesized samples were characterized using Fourier transform infrared and proton nuclear magnetic resonance spectroscopies. Morphology, thermal stability, size, and magnetic properties of the synthesized MNHG were investigated. In addition, the doxorubicin hydrochloride loading and encapsulation efficiencies as well as stimuli‐responsive drug release ability of the synthesized MNHG were also evaluated. The drug‐loaded MNHG at physiological condition exhibited negligible drug release values. In contrast, at acidic (pH 5.3) condition and a little bit higher temperature (41 °C) the developed MNHG showed higher drug release values, which qualified it for cancer chemotherapy due to especial physiology of cancerous tissue in comparison with the surrounding normal tissue. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46657.     

A facile preparation of pH‐temperature dual stimuli‐responsive supramolecular hydrogel and its controllable drug release

A series of pH‐temperature dual stimuli‐responsive random copolymers poly[N,N‐dimethylaminoethyl methacrylate‐co‐poly(poly(ethylene glycol) methyl ether methacrylate][poly(DMAEMA‐co‐MPEGMA)] were synthesized by free radical polymerization. The supramolecular hydrogel was formed by pseudopolyrotaxane, which was prepared with the host‐guest interactions between α‐cyclodextrin (α‐CD) and poly(ethylene glycol) (PEG) side chains. Fourier transform infrared (FT‐IR), nuclear magnetic resonance (¹H NMR), and X‐ray diffraction (XRD) confirmed the structures of the hydrogels. The pH‐temperature dual stimuli responsive properties of the hydrogels were characterized by rheometer. Finally, the controllable drug release behavior of the hydrogel, which was used 5‐fluorouracil (5‐Fu) as the model drug, was investigated at different temperatures and different pH values. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43279.     

Synthesis of pH‐responsive crosslinked poly[styrene‐co‐(maleic sodium anhydride)] and cellulose composite hydrogel nanofibers by electrospinning

BACKGROUND: Stimuli‐sensitive materials show enormous potential in the development of drug delivery systems. But the low response rate of most stimuli‐sensitive materials limits their wider application. We propose that electrospinning, a technique for the preparation of ultrafine fibrous materials with ultrafine diameters, may be used to prepare materials with a fast response to stimuli. RESULTS: Poly[styrene‐co‐(maleic sodium anhydride)] and cellulose (SMA‐Na/cellulose) hydrogel nanofibers were prepared through hydrolysis of precursor electrospun poly[styrene‐co‐(maleic anhydride)]/cellulose acetate (SMA/CA) nanofibers. In the presence of diethylene glycol, the SMA/CA composite nanofibers were crosslinked by esterification at 145 °C, and then hydrolyzed to yield crosslinked SMA‐Na/cellulose hydrogel nanofibers. These nanofibers showed better mechanical strengths and were pH responsive. Their water swelling ratio showed a characteristic two‐step increase at pH = 5.0 and 8.2, with the water swelling ratio reaching a maximum of 27.6 g g^?1 at pH = 9.1. CONCLUSION: The crosslinked SMA‐Na hydrogel nanofibers supported on cellulose showed improved dimensional stability upon immersion in aqueous solutions. They were pH responsive. This new type of hydrogel nanofiber is a potential material for biomedical applications. Copyright © 2009 Society of Chemical Industry     

Thermosensitive nanoparticles prepared from poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) and its blend with poly(lactide‐co‐glycolide) for efficient drug delivery system

Temperature‐responsive polymers have become increasingly attractive as carrier for the injectable drug delivery systems. In the present work, we have studied the preparation of poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) (NIPAAm‐AAm‐VP terpolymer) nanoparticulated terpolymer and its blend with poly(lactide‐co‐glycolide, PLGA; molar ratio of lactide/glycolid 1/3). Thermosensitive terpolymer, poly(NIPAAm‐AAm‐VP) was prepared by free‐radical polymerization in aqueous solution. The nanoparticles of poly(NIPAAm‐AAm‐VP) and its blend with PLGA containing naltrexone were prepared using the evaporation and w/o emulsion‐solvent evaporation methods, respectively. Nanoparticles prepared from terpolymer‐PLGA blend at low polymer concentration (5%) shows larger particle size (>300 nm) and higher drug content%. Various types of nanoparticles showed a burst release of less than 10% after 24 h . The results suggest that by regulating different variables, desired release profiles of naltrexone can be achieved using a blend of PLGA‐poly(NIPAAm‐AAm‐VP) nanoparticulate system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hydrogels composite of poly(acrylamide‐co‐acrylate) and rice husk ash. I. Synthesis and characterization

Composite hydrogels of poly(acrylamide‐co‐acrylate) with rice husk ash (RHA) were synthesized and studies of the swelling variables were accomplished comparatively with commercial polyacrylamide gel and PAMACRYL, a poly(acrylamide‐co‐acrylate) hydrogel without RHA. FT‐IR and WAXS were the techniques employed for characterizing a series of hydrogel obtained by varying the percentage of RHA (1, 2, 5, 10, and 20 wt %) and the amount of crosslinking agent (0.05, 0.1, and 0.2 mol %) relative to sum of AAm and AAc. Superabsorbent hydrogel with W_eq > 800 g H₂O/g gel was obtained with percentage of 10 wt % of RHA and 0.1 of crosslinking agent mol %. The hydrogel showed to be sensitive to the pH variation and to the presence of salts. The hydrogels, even though submitted through cycles of drying and swelling, preserved their superabsorbent characteristics and demonstrated better water absorbance properties when compared with commercial polyacrylamide gel. The composite hydrogels of poly(acrylamide‐co‐acrylate) with RHA presented good characteristics to be applied as soil conditioner for using in agriculture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of magnetite and silver poly(2‐acrylamido‐2‐methyl propane sulfonic acid‐co‐acrylamide) nanocomposites for adsorption and catalytic degradation of methylene blue water pollutant

The aim of the present work was to prepare microgel nanocomposites based on silver and magnetite to apply as adsorbents and heterogeneous catalysts for removal of methylene blue (MB) cationic dye from aqueous solution. For this, 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and acrylamide (AAm) monomers were used to prepare AMPS/AAm microgel based on the emulsion technique. Ag and Fe₃O₄ nanoparticles were embedded into the AMPS/AAm microgel using the in situ technique. Their particle sizes, surface charges, crystalline lattice structure, morphology, magnetic properties and thermal stability were investigated. The AMPS/AAm hydrogel nanocomposites were used as an adsorbent to remove MB dye. The AMPS/AAm microgel nanocomposites were tested as catalysts to reduce MB and degrade its chemical structure with heterogeneous Fenton oxidation using Ag and Fe₃O₄ nanocomposites, respectively. This study presents promising data as the prepared materials used as adsorbents and catalysts show competitive features compared with the data presented in the literature. © 2019 Society of Chemical Industry     

Removal of heavy metal ions from aqueous solutions by radiation‐induced chitosan/(acrylamidoglycolic acid‐co‐acrylic acid) magnetic nanopolymer

An effective method was developed to isolate toxic heavy metal ions from the aqueous solution by the magnetic nanopolymers. The magnetic sorbent was prepared with radiation‐induced crosslinking polymerization of chitosan (CS), 2‐acrylamido‐glycolic acid (AMGA), and acrylic acid (AAc), which stabilized by magnetite (Fe₃O₄) as nanoparticles. The formation of magnetic nanoparticles (MNPs) into the hydrogel networks was confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and Scanning electron microscopy, which revealed the formation of MNPs throughout the hydrogel networks. The swelling behavior of the hydrogels and magnetic ones was evaluated at different pH values. The adsorption activity for heavy metals such as Cu²⁺ and Co²⁺ by nonmagnetic and magnetic hydrogels, Fe₃O₄/CS/(AMGA‐co‐AAc), in terms of adsorption amount was studied. It was revealed that hydrogel networks with magnetic properties can effectively be used in the removal of heavy metal ions pollutants and provide advantageous over conventional ones. POLYM. ENG. SCI., 55:1441–1449, 2015. © 2015 Society of Plastics Engineers     

Synthesis of an alginate–poly(sodium acrylate‐co‐acrylamide) superabsorbent hydrogel with low salt sensitivity and high pH sensitivity

This article describes the synthesis and swelling behavior of a superabsorbing hydrogel based on sodium alginate (NaAlg) and polyacrylonitrile (PAN). The physical mixture of NaAlg and PAN was hydrolyzed with a solution of NaOH to yield an alginate–poly(sodium acrylate‐co‐acrylamide) [Alg–poly(NaAA‐co‐AAm)] superabsorbent hydrogel. A proposed mechanism for hydrogel formation was suggested, and the structure of the product was established with Fourier transform infrared spectroscopy. The effects of reaction variables were systematically optimized to achieve a hydrogel with a swelling capacity as high as possible. Under the optimized conditions concluded, the maximum capacity of swelling in distilled water was 610 g/g. The absorbency of the synthesized hydrogels was also measured in various salt solutions. The swelling ratios decreased with an increase in the ionic strength of the salt solutions. In addition, the swelling capacity was determined in solutions with pHs ranging from 1 to 13. The Alg–poly(NaAA‐co‐AAm) hydrogel exhibited pH responsiveness, so a swelling–deswelling pulsatile behavior was recorded at pHs 2 and 8. This on–off switching behavior made the hydrogel as a good candidate for the controlled delivery of bioactive agents. Finally, the swelling kinetics of the hydrogels with various particle sizes were preliminarily investigated as well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2927–2937, 2006     

Alkaline protease production by immobilized growing cells of Serratia marcescens with interpolymer complexes of P(TM‐co‐AAm)/PAA

The growing cells of Serratia marcescens (SM) were immobilized with the interpolymer complex carrier, which is formed by the cationic polymer, poly(allyltrimethyl ammonium chloride‐co‐acrylamide) [P(TM‐co‐AAm)], and poly(acrylic acid) (PAA). When the association degree of PAA is suitable to the cationic degree of P(TM‐co‐AAm), the effective crosslinking network provides the most favorable circumstances for the cell immobilization. The alkaline protease can be produced by the immobilized SM with high activity. Compared with the free cells, the immobilized SM has higher thermal stability, acid‐base stability, operational stability, and storage stability. Under the optimum immobilizing conditions, not only the living cells of SM but also thermophilic Bacillus firmus (TBF) were immobilized with the complex of P(TM‐co‐AAm)/PAA. The results show the carrier of P(TM‐co‐AAm)/PAA complex to be superior in properties to the usual carriers, such as Na‐alginate and carrageenan. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 178–183, 2002; DOI 10.1002/app.10293     

Influence of carboxyl and amide groups on in vitro hemocompatibility of sulfonated polypropylene non‐woven fabric

The sulfonated polypropylene non‐woven fabric (PP_NWF) was successfully fabricated via γ‐ray simultaneous radiation‐induced graft polymerization of acrylic acid (AA)/sodium styrenesulfonate (NaSS) and acrylamide (AAm)/NaSS. The existence of graft chains in both PP‐g‐P(AA‐co‐NaSS) and PP‐g‐P(AAm‐co‐NaSS) was proved by attenuated total reflection Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Water contact angle measurement illustrated the sulfonated PP_NWF owning good hydrophilicity. The in vitro hemocompatibility evaluation showed that both PP‐g‐P(AA‐co‐NaSS) and PP‐g‐P(AAm‐co‐NaSS) inhibited effectively the adhesion of platelets and were significantly compatible with erythrocytes. Moreover, no obvious difference was confirmed in the prevention of platelet adhesion and hemolysis ratio between carboxyl and amide groups. However, as compared with that of PP‐g‐P(AAm‐co‐NaSS), PP‐g‐P(AA‐co‐NaSS) exhibited outstanding anticoagulant activity via increased activated partial thromboplastin time and thrombin time. This result indicated that the carboxyl group but not amide group featured strong synergistic effect on the anticoagulant activity of sulfonated PP_NWF. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45915.     

Synthesis and characterization of novel core‐shell magnetic nanogels based on 2‐acrylamido‐2‐methylpropane sulfonic acid in aqueous media

Ultrafine well‐dispersed Fe₃O₄ magnetic nanoparticles were directly prepared in aqueous solution using controlled coprecipitation method. The synthesis of Fe₃O₄/poly (2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS), Fe₃O₄/poly (acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AM‐co‐AMPS) and Fe₃O₄/poly (acrylic acid‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AA‐co‐AMPS) ‐core/shell nanogels are reported. The nanogels were prepared via crosslinking copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid, acrylamide and acrylic acid monomers in the presence of Fe₃O₄ nanoparticles, N,N′‐methylenebisacrylamide (MBA) as a crosslinker, N,N,N′,N′‐tetramethylethylenediamine (TEMED) and potassium peroxydisulfate (KPS) as redox initiator system. The results of FTIR and ¹H‐NMR spectra indicated that the compositions of the prepared nanogels are consistent with the designed structure. X‐ray powder diffraction (XRD) and transmission electron microscope (TEM) measurements were used to determine the size of both magnetite and stabilized polymer coated magnetite nanoparticles. The data showed that the mean particle size of synthesized magnetite (Fe₃O₄) nanoparticles was about 10 nm. The diameter of the stabilized polymer coated Fe₃O₄ nanogels ranged from 50 to 250 nm based on polymer type. TEM micrographs proved that nanogels possess the spherical morphology before and after swelling. These nanogels exhibited pH‐induced phase transition due to protonation of AMPS copolymer chains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Immobilization of chymotrypsin with interpolymer complexes of P(TM‐co‐AAm)/PAA

Chymotrypsin was immobilized with interpolymer complexes formed by the cationic polymer poly(allyltrimethyl ammonium chloride‐co‐acrylamide) [P(TM‐co‐AAm)] and poly(acrylic acid) (PAA). The introduction of a small amount of cationic groups led to a much stronger polymer–polymer interaction between P(TM‐co‐AAm) and PAA. The characteristic pH sensitivity of this kind of complex provided the possibilities of controlling the activity of the immobilized enzyme and separating the immobilized enzyme from the batch by changing the pH of the medium. Compared with the free enzyme, the immobilized chymotrypsin had higher thermal stability, acid–base stability, and stability in use. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2013–2018, 2001     

Synthesis of novel thermo‐ and redox‐sensitive polypeptide hydrogels

Multi‐responsive hydrogels have recently received considerable attention for bioapplications. Here, novel temperature‐ and redox‐responsive polypetide hydrogels have been developed. Thermo‐sensitive hydrogels based on poly(ethyleneglycol)‐block ‐poly(γ‐propargyl‐l ‐glutamate) (PEG‐PPLG ) were first synthesized by the ring opening polymerization of γ‐propargyl‐l ‐glutamate N ‐carboxyanhydride (PLG‐NCA ) with amino group terminated PEG monomethyl ether (mPEG‐NH₂ ) as macroinitiator and were then functionalized via the ‘thiol‐yne’ click reaction between the propargyl pendents and the thiol‐containing 1‐propanethiol. The sol ? gel phase transition of the obtained copolymer aqueous solution in response to temperature change was studied. The mass loss of the hydrogel in vitro was accelerated in the presence of H₂O₂ , exhibiting a redox‐responsive property. Further, the methyl thiazolyl tetrazolium viability results revealed that this polypetide hydrogel has excellent biocompatibility, presenting potential applications in the biomedical field. © 2016 Society of Chemical Industry     

Development of a thermosensitive grafted drug delivery system—synthesis and characterization of NIPAAm‐based grafts and hydrogel structure

A thermosensitive grafted hydrogel was investigated for heating‐activated drug release. The hydrogel was created by grafting oligomers of N‐isopropylacrylamide‐co‐acrylamide (AAm) to a poly(2‐hydroxyethyl methacrylate), or PHEMA, hydrogel. N‐Isopropylacrylamide‐co‐AAm oligomers were synthesized with a range of compositions to raise the lower critical solution temperature (LCST) above physiological temperature. PHEMA hydrogels with these thermosensitive grafts were synthesized by free‐radical solution polymerization, using an acrylated version of the oligomers. The oligomers were characterized for their molecular weight, LCSTs, and rate of response to a change in temperature. With the flexibility in tuning their properties by varying reaction parameters, these oligomers present possibilities in several fields, including drug delivery. The impact of cross‐linking agent type and the amount and presence of grafts on the polymer network structure was found by determining the hydrogel mesh sizes. PHEMA gels cross‐linked with methylenebisacrylamide had larger mesh sizes than those cross‐linked with ethylene glycol dimethacrylate. Increasing amounts of cross‐linking agent decreased mesh sizes. LCSTs exhibited by oligomers were slightly lower than those exhibited by polymer gels of the same composition. The grafting reaction was found to have only a slight impact on the hydrogel mesh size. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011