Novel thermo‐responsive semi‐interpenetrating network microspheres of gellan gum‐poly(N‐isopropylacrylamide) for controlled release of atenolol

Thermoresponsive microspheres of gellan gum‐poly(N‐isopropylacrylamide), i.e., GG‐P(NIPAAm) semi‐interpenetrating polymer networks (semi‐IPNs) have been prepared by ionic crosslinking and used to study the controlled release (CR) of atenolol (ATL), an antihypertensive drug. Interaction of the drug with polymers was studied by Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC) was used to confirm the polymorphism and molecular level dispersion of ATL. Scanning electron microscopy (SEM) indicated spherical nature and smooth surfaces of the microspheres with some debris attached on their surfaces. Mean particle size measured by laser light diffraction ranged between 34 and 76 μm. Equilibrium swelling performed at 25°C and 37°C in pH 7.4 phosphate buffer exhibited thermoresponsive nature of the polymers. In vitro drug release performed at 25°C and 37°C indicated temperature‐dependency of ATL release, which was extended up to 12 h. In vitro release profiles at both the temperatures confirmed thermoresponsive nature of the polymers giving pulsatile trends. The % cumulative release data have been fitted to an empirical equation to estimate transport parameters and to understand the nature of drug release. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Swelling kinetics,mechanical properties,and release characteristics of chitosan‐based semi‐IPN hydrogels

Two series of pH‐sensitive semi‐interpenetrating network hydrogels (semi‐IPN) based on chitosan (CS) natural polymer and acrylamide (AAm) and/or N‐hydroxymethyl acrylamide (HMA) monomers by varying the monomer and CS ratios were synthesized by free radical chain polymerization. 5‐Fluorouracil (5‐FU), a model anticancer drug, has been added to the feed composition before the polymerization. The characterization of gels indicated that the drug is molecularly dispersed in the polymer matrix. The swelling kinetics of drug‐loaded gels have decreased with increased HMA content at 37°C in both distilled water and buffer solutions with a pH of 2.1 or 7.4. Elastic modulus of the gels increased with the increase in HMA content and higher CS concentration enhanced the elastic modulus positively. Moreover, cumulative release percentages of the gels for 5‐FU were ca. 10% higher in pH 2.1 than those in pH 7.4 media. It was determined that they can be suitable for the use in both gastric and colon environments. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41886.     

Recycling of reactive dye using semi‐interpenetrating polymer network from sodium alginate and isopropyl acrylamide

A sequence of semi‐interpenetrating polymer network (semi‐IPN) were synthesized by free radical photo copolymerizing acrylic acid and isopropyl acrylamide (NIPAAm) in aqueous sodium alginate (NaAlg). Their structures (FT‐IR), thermal stability (TG/DTG), morphology (SEM), mechanical properties, reactive blue 4 (RB 4) dye adsorption (624 mg/g) and its dying characteristics, reusability of dye and adsorbent were evaluated. TG thermograms of semi‐IPN in air revealed zero order kinetics for initial step thermal degradation with an activation energy of 68.68 kJ/mol. Dye adsorption showed best fit for Langmuir adsorption isotherm and the kinetics followed pseudo‐second‐order model. The water and dye diffusion kinetics followed non‐Fickian mechanism. The changes in thermodynamic parameters namely Gibbs free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) indicated that the adsorption was spontaneous and exothermic process for RB 4/semi‐IPN system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40968.     

Preparation of alginate/poly(N‐isopropylacrylamide) semi‐interpenetrating and fully interpenetrating polymer network hydrogels with γ‐ray irradiation and their swelling behaviors

Semi‐interpenetrating polymer network (semi‐IPN) and fully interpenetrating polymer network (full‐IPN) hydrogels composed of alginate and poly(N‐isopropylacrylamide) were prepared with γ‐ray irradiation. The semi‐IPN hydrogels were prepared through the irradiation of a mixed solution composed of alginate and N‐isopropylacrylamide (NIPAAm) monomer to simultaneously achieve the polymerization and self‐crosslinking of NIPAAm. The full‐IPN hydrogels were formed through the immersion of the semi‐IPN film in a calcium‐ion solution. The results for the swelling and deswelling behaviors showed that the swelling ratio of semi‐IPN hydrogels was higher than that of full‐IPN hydrogels. A semi‐IPN hydrogel containing more alginate exhibited relatively rapid swelling and deswelling rates, whereas a full‐IPN hydrogel showed an adverse tendency. All the hydrogels with NIPAAm exhibited a change in the swelling ratio around 30–40°C, and full‐IPN hydrogels showed more sensitive and reversible behavior than semi‐IPN hydrogels under a stepwise stimulus. In addition, the swelling ratio of the hydrogels continuously increased with the pH values, and the swelling processes were proven to be repeatable with pH changes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4439–4446, 2006     

Swelling dynamics of IPN hydrogels including acrylamide‐acrylic acid‐chitosan and evaluation of their potential for controlled release of piperacillin‐tazobactam

For to be used in controlled releasing of piperacillin‐tazobactam, a series of semi and full IPN type hydrogels composed of acrylic acid (AA), acrylamide (AAm) and Chitosan (CS) were prepared via free‐radical polymerization. Ethylene glycol dimethacrylate (EGDMA) was used for crosslinking of PAAm and PAA chains to form semi‐IPN hydrogels. However, the full‐IPN type hydrogels were prepared by using glutaraldehyde (GA) and EGDMA as cocrosslinkers. Characteristics of the hydrogels were investigated by swelling experiments and SEM and FTIR analysis. Generally, full‐IPN type hydrogels swell much more than the semi‐IPN types. By comparing the full‐IPN type hydrogels in between, it is found that the increasing amount of GA causes the decreasing in S% values from 4860 to 4300%. Releasing of piperacillin‐tazobactam from selected three hydrogels were investigated in phosphate buffer solution at pH = 7.4, 37°C. The kinetic release parameters, n and k were calculated and non‐Fickian type diffusion was established for these hydrogels. The behaviors of the piperacillin‐tazobactam loaded hydrogels in Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) culture suspensions were also studied and the statistically significant differences for the microorganism growth values were determined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chitosan‐based interpolymeric pH‐responsive hydrogels for in vitro drug release

Two series of pH‐responsive biodegradable interpolymeric (IPN) hydrogels based on chitosan (Ch) and poly(vinyl alcohol) (PVA) were prepared for controlled drug release investigations. The first series was chemically crosslinked with different concentrations of glutaraldehyde and the second was crosslinked upon γ‐irradiation by different doses. The equilibrium swelling characteristics were investigated for the gels at 37°C in buffer solutions of pH 2.1 and 7.4 as simulated gastric and intestinal fluids, respectively. 5‐Fluorouracil (FU) was entrapped in the hydrogels, as a model therapeutic agent, and the in vitro release profiles of the drug were established at 37°C in pH 2.1 and 7.4. FTIR, SEM, and X‐ray diffraction analyses were used to characterize and investigate the structural changes of the gels with the variation of the blend composition and crosslinker content before and after the drug loading. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2864–2874, 2007     

Thermo‐ and pH‐responsive behaviors of graft copolymer and blend based on chitosan and N‐isopropylacrylamide

Thermo‐ and pH‐sensitive polymers were prepared by graft polymerization or blending of chitosan and poly(N‐isopropylacrylamide) (PNIPAAm). The graft copolymer and blend were characterized by Fourier transform‐infrared, thermogravimetric analysis, X‐ray diffraction measurements, and solubility test. The maximum grafting (%) of chitosan‐g‐(N‐isopropylacrylamide) (NIPAAm) was obtained at the 0.5 M NIPAAm monomer concentration, 2 × 10⁻³ M of ceric ammonium nitrate initiator and 2 h of reaction time at 25°C. The percentage of grafting (%) and the efficiency of grafting (%) gradually increased with the concentration of NIPAAm up to 0.5 M, and then decreased at above 0.5 M NIPAAm concentration due to the increase in the homopolymerization of NIPAAm. Both crosslinked chitosan‐g‐NIPAAm and chitosan/PNIPAAm blend reached an equilibrium state within 30 min. The equilibrium water content of all IPN samples dropped sharply at pH > 6 and temperature > 30°C. In the buffer solutions of various pH and temperature, the chitosan/PNIPAAm blend IPN has a somewhat higher swelling than that of the chitosan‐g‐NIPAAm IPN. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1381–1391, 2000     

In vitro degradation and protein release of semi‐IPN hydrogels consisted of poly(acrylic acid‐acrylamide‐methacrylate) and amylose

The enzymatic degradation mechanism of semi‐interpenetrating network (semi‐IPN) hydrogel of poly (acrylic acid‐acrylamide‐methacrylate) crosslinked by azocompound and amylose in vitro was investigated in the presence of Fungamyl 800L (α‐amylase) and rat cecum content (cecum bacteria). The degradation mechanism involves degradable competition, i.e., reduction of azo crosslinkage is dominant in the earlier period of degradation. Subsequently, the degradation of gels is continued by combination of reduction of azo crosslinkage and hydrolysis of amylose. The cumulative release ratios of Bovine serum albumin (BSA, as a model drug) loaded semi‐IPN gels are 25% in pH 2.2 buffer solutions and 74% in pH 7.4 buffer solutions within 48 h. Moreover, the release behavior of BSA from the semi‐IPN gels indicates that it follows Fickian diffusion mechanism in pH 2.2 media and non‐Fickian diffusion and polymer chains relaxation mechanism in pH 7.4 media. The results indicate that the release of BSA from the semi‐IPN gels was controlled via a combined mechanism of pH dependent swelling and specificity to enzymatic degradation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Studies on novel semi‐2‐IPNs from polyetherimide and citraconimide

A series of novel semi‐2‐interpenetrating polymeric networks (semi‐2‐IPNs) were prepared through blending in solution using two different polyimides, biscitraconamic acid as a precursor of biscitraconimide (MBMI) with various proportions of polyetherimide (PEI) to achieve optimum properties. Biscitraconamic acid was prepared by reacting citraconic anhydride (CA), 3,3',4,4'‐benzophenone tetracarboxylic dianhydride (BTDA) and bis(3‐aminopropyl)phenyl phosphine (BAPPP) and it was characterized by differential scanning calorimetry (DSC), FTIR, and ¹H‐NMR spectroscopy. Both biscitraconamic acid and PEI were blended in N,N‐dimethylacetamide (DMAc) solution, casted and thermally cured up to 300°C to give semi‐2‐IPNs. The MBMI/PEI semi‐IPN systems were characterized by UV‐Vis spectroscopy, FTIR spectroscopy and thermal techniques. The phase morphology, isothermal aging, and water uptake of semi‐IPN systems have also been studied. The morphological studies on phase distribution were investigated by scanning electron microscopy (SEM). Thermal performance of MBMI/PEI semi‐IPN systems were evaluated by DSC and thermo gravimetric analysis (TGA). All the compositions of semi‐IPN polyimide system were stable up to 400°C and their thermal stability increased with increase in the content of PEI. Isothermal aging studies done at 300°C for various time periods showed good thermo‐oxidative stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of novel semi‐interpenetrating 2‐hydroxyethyl methacrylate‐g‐chitosan copolymeric microspheres for sustained release of indomethacin

A novel semi‐interpenetrating (semi‐IPN) graft copolymer of 2‐hydroxyethyl methacrylate (HEMA) with chitosan (CS) has been prepared in the form of microspheres, using water‐in‐oil (W/O) emulsion technique. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X‐ray diffractometry (X‐RD) to confirm the crosslinking and polymorphism of indomethacin (IDM). The X‐RD and DSC techniques indicated a molecular‐level dispersion of IDM in the IPN matrix. Scanning electron micrographs (SEM) taken at the cross section of the microspheres have shown rough surfaces around the microspheres. The sustained release characteristics of the matrices for IDM, an anti‐inflammatory drug, were investigated in pH 7.4 media. Particle size and size distribution of the microspheres were studied by laser light diffraction particle size analyzer. The drug was released in a sustained manner for up to 12 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Injectable and thermosensitive poly(organophosphazene) hydrogels for a 5‐fluorouracil delivery

The drug solubility and its release profiles of an anticancer drug from an injectable thermosensitive poly(organophosphazene) hydrogel bearing hydrophobic L ‐isoleucine ethyl ester and hydrophilic α‐amino‐ω‐methoxy‐poly(ethylene glycol) with and without hydrolysis‐sensitive glycyl lactate ethyl ester or functional glycyl glycine have been investigated. 5‐Fluorouracil (5‐FU) was used as a model anticancer drug. The aqueous solutions of 5‐FU incorporated poly(organophosphazenes) were an injectable fluid state at room temperature and formed a transparent gel at body temperature. The poly(organophosphazene) solution could enhance the solubility of 5‐FU and its solubility (34.26 mg/mL) was increased up to 10‐fold compared to that in phosphate‐buffered saline (3.39 mg/mL, pH 7.4, 4°C). The in vitro drug release profiles from poly(organophosphazene) hydrogels were established in phosphate‐buffered saline at pH 7.4 at 37°C and the release of 5‐FU was significantly affected by the diffusion‐controlled stage. The results suggest that the injectable and thermosensitive poly(organophosphazene) hydrogel is a potential carrier for 5‐FU to increase its solubility, control a relatively sustained and localized release at target sites and thus decrease systemic side effects. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Application of syndiotacticity‐rich PVA hydrogels prepared at a low temperature to thermo‐ and pH‐responsive release devices

Three kinds of physically cross‐linked syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA) hydrogels were prepared at 0°C with use of the buffer solutions (BS) of pHs 4.0, 7.4, and 9.0. Three gels swelled at first and then began to shrink after 12 h when they were dipped in the same BS for preparation at higher temperature than 0°C. The release of Brilliant Blue (3 mg/1 mL) from the cylindrical gels prepared using BS of pH 7.4 was studied at 27, 37, and 47°C. Brilliant Blue has been released spending 4–12 h almost completely. The rate of release from the gel at temperatures of 27, 37, and 47°C became large with increasing temperature. The main factor on release of Brilliant Blue is not the contraction of gel, but swelling, because the degree of swelling (DS) became large with increasing temperatures for 27, 37, and 47°C. The rate of release from the gel (pH 4.0) was larger than that (pH 7.4) due to the increased DS of the hydrogel in early step at pH of 4.0. The apparent diffusion exponents of these releases at pH 7.4 evaluated from first 60% of the fractional release were lower than 0.45 due to the swelling during release. The exponent at pH 4.0 was 0.45 due to immediate swelling. The on‐off of shrinking behavior of atactic PVA (a‐PVA) hydrogel was observed under several temperature changes. The rate of release of Brilliant Blue at 5°C was lower than that at 27°C and no change was observed at 5°C after one on‐off cycle. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 41–46, 2000     

Thermal characterizations of semi‐interpenetrating polymer networks composed of poly(ethylene oxide) and poly(N‐isopropylacrylamide)

Poly(N‐isopropylacrylamide) (PNIPAAm)/poly(ethylene oxide) (PEO) semi‐interpenetrating polymer networks (semi‐IPNs) synthesized by radical polymerization of N‐isopropylacrylamide (NIPAAm) in the presence of PEO. The thermal characterizations of the semi‐IPNs were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). The melting temperature (T_m) of semi‐IPNs appeared at around 60°C using DSC. DEA was employed to ascertain the glass transition temperature (T_g) and determine the activation energy (E_a) of semi‐IPNs. From the results of DEA, semi‐IPNs exhibited one T_g indicating the presence of phase separation in the semi‐IPN, and T_gs of semi‐IPNs were observed with increasing PNIPAAm content. The thermal decomposition of semi‐IPNa was investigated using TGA and appeared at around 370°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3922–3927, 2003     

Comparison of the pervaporation separation of a water–acetonitrile mixture with zeolite‐filled sodium alginate and poly(vinyl alcohol)–polyaniline semi‐interpenetrating polymer network membranes

The pervaporation (PV) separation performance of ZSM‐5‐ and Na‐Y‐type zeolite‐filled sodium alginate (NaAlg) membranes were compared with those of pure NaAlg and semi‐interpenetrating polymer network (semi‐IPN) membranes of poly(vinyl alcohol) (PVA) with polyaniline (PANI) for the dehydration of acetonitrile. The PV separation characteristics of the zeolite‐filled membranes showed a dependence on the nature of the zeolites. The variation of the acidity function of the ZSM‐5 zeolite had an influence on the flux and selectivity of the membranes when compared to unfilled membranes. The crosslinked membranes were characterized by differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Increasing the PANI content of the semi‐IPN network increased the separation selectivity. Among the NaAlg membranes, the plain NaAlg membrane showed the highest selectivity of 414 at 30 mass % water in the feed mixture, whereas the Na‐Y‐ and ZSM‐5 (40)‐filled NaAlg membranes exhibited much lower values of selectivity, that is, 7.3 and 4.3, respectively for 30 mass % water in the feed. When the flux and selectivity data of ZSM‐5 (250)‐filled NaAlg membranes were compared with that of Na‐Y‐ or ZSM‐5 (40)‐filled NaAlg membranes, a noticeable increase in the selectivity for the ZSM‐5 (250)‐filled NaAlg membrane was observed, but a somewhat comparable flux was observed compared to the plain NaAlg membrane. For the first time, PANI was polymerized with PVA to yield a semi‐IPN. The total flux and water flux increased systematically, whereas the selectivity decreased greatly from 251.87 to 5.95 with increasing amounts of water in the feed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1968–1978, 2005     

p(AAm/TA)‐based IPN hydrogel films with antimicrobial and antioxidant properties for biomedical applications

Interpenetrating polymer networks (IPN), either semi‐IPN (s‐IPN) or full IPN, based on a natural polymer tannic acid (TA) and synthetic poly(acrylamide) (p(AAm)) were prepared by incorporation of TA during p(AAm) hydrogel film preparation with and without crosslinking of TA simultaneously. The synthesis of p(AAm/TA) s‐IPN and IPN hydrogels with different amounts of TA were prepared by concurrent use of redox polymerization and epoxy crosslinking. The p(AAm)‐based hydrogels were completely degraded at 37.5°C within 9 and 2 days at pHs 7.4 and 9, respectively. Biocompatibility of p(AAm), s‐IPN, and IPN were tested with WST assay and double staining, they had 75% cell viability up to almost 20 μg mL^?1 concentration against L929 fibroblast cell. Antioxidant properties of IPN and s‐IPN hydrogels were investigated with FC and ABTS^? methods. Antimicrobial properties of TA‐containing s‐IPN, and IPN hydrogels were determined against three common bacterial strains, Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Bacillus subtilis ATCC 6633, and it was found that p(AAm/TA)‐based s‐IPN and IPN hydrogels are effective antimicrobial and antioxidant materials. Moreover, almost up to day‐long linear TA release profiles were obtained from IPN and s‐IPN hydrogels in phosphate buffer solution at pH 7.4 at 37.5°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41876.     

Effect of silane coupling agent on swelling behaviors and mechanical properties of thermosensitive hybrid gels

A series of organic–inorganic hybrid thermosensitive gels with three different structures were prepared from N‐isopropylacrylamide (NIPAAm), and N, N′‐methylenebisacrylamide (NMBA) and tetraethoxysilane (TEOS) [N‐IPN]; NIPAAm, 3‐(trimethoxysilyl) propyl methacrylate (TMSPMA) as coupling agent and TEOS [NT‐IPN]; and NIPAAm, TMSPMA, and TEOS [NT‐semi‐IPN] by emulsion polymerization and sol–gel reaction in this study. The effect of different gel structures and coupling agent on the swelling behavior, mechanical properties, and morphologies of the present gels was investigated. Results showed that the properties of the gels would be affected by the gel networks such as IPN or semi‐IPN and with or without existence of TMSPMA as the bridge chain between networks. The NT‐semi‐IPN gel had higher swelling ratio and faster diffusion rate because poly(NIPAAm) moiety in the semi‐IPN gels was not restricted by NMBA network. However, the IPN gels such as N‐IPN and NT‐IPN had good mechanical properties and lower swelling ratio, but had a poor thermosensitivity due to the addition of coupling agent, TMSPMA, into the gel system that resulted in denser link between organic and inorganic components. The morphology showed that IPN gels had partial aggregation (siloxane domain) and showed some denser phases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

In vitro degradation and release profiles of poly‐DL‐lactide‐poly(ethylene glycol) microspheres with entrapped proteins

Poly‐DL ‐lactide (PLA) and poly‐DL ‐lactide‐poly(ethylene glycol) (PELA) were produced by bulk ring‐opening polymerization using stannous chloride as initiator. PLA, PELA microspheres, and PELA microspheres containing the outer membrane protein (OMP) of Leptospira interrogans with the size of 1.5–2 μm were prepared by a solvent evaporation process. In vitro degradation and release tests of PLA, PELA, and OMP‐loaded PELA microspheres were performed in pH 7.4 buffer solution at 37°C. Quantitatively, the degree of degradation was monitored by detecting the molecular weight reduction, by evaluating the mass loss and the apparent degradation rate constant, and by determining the intrinsic viscosity and poly(ethylene glycol) content of retrieved polymer, while the release profile was assessed by measuring the amount of protein presented in the release medium at various intervals. Qualitatively, the morphological changes of microspheres were observed with scanning electron micrography. The observed relative rates of mass loss versus molecular weight reduction are consistent with a bulk erosion process rather than surface erosion for PELA microspheres. The introduction of hydrophilic poly(ethylene glycol) domains in copolymer PELA and the presence of OMP within microspheres show critical influences on the degradation profile. The OMP‐loaded PELA microspheres present triphasic release profile and a close correlation is observed between the polymer degradation and the OMP release profiles. It is suggested that the polymer degradation rate, protein diffusion coefficient, and the water‐swollen structure of microspheres matrix commonly contribute to the OMP release from PELA microspheres. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 140–148, 2000     

Ionic conductivity and morphology of semi‐interpenetrating‐type polymer electrolyte entrapping poly(siloxane‐g‐allyl cyanide)

We prepared a semi‐IPN (interpenetrating network)‐type solid polymer electrolyte (SPE) using poly (ethylene glycol)dimethacrylate (PEGDMA) as a polymer matrix containing a monocomb‐type poly(siloxane‐g‐allyl cyanide) and poly(ethylene glycol)dimethylether (PEGDME) for the lithium secondary battery. The poly(siloxane‐g‐allyl cyanide)s were prepared by a hydrosilation reaction of poly (methyl hydrosiloxane) with allyl cyanide and characterized by ¹H NMR and FTIR. The semi‐IPN‐type electrolyte was prepared by thermal curing, and conductivities of samples were measured by impedance spectroscopy using an indium tin oxide (ITO) electrode. The ionic conductivity of the semi‐IPN‐polymer electrolyte was about 1.05 × 10^?5 S cm^?1 with 60 wt % of the poly(siloxane‐g‐allyl cyanide) and 6.96 × 10^?4 S cm^?1 with 50 wt % of the PEGDME and 10 wt % of the poly(siloxane‐g‐allyl cyanide) at 30°C. The SEM morphology of the cross section of the semi‐IPN‐polymer electrolyte film was changed from discontinuous network to continuous network as increasing the PEGDME content and decreasing the poly(siloxane‐g‐allyl cyanide) content. The mechanical stability was also enhanced when increasing the PEGDME content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Reduction of free radicals and endotoxin by conjugated linoleic acid loaded in an in situ‐synthesized poly(N‐isopropyl acrylamide) thin layer

A thin layer of poly(N‐isopropyl acrylamide) (pNIPAAm) was synthesized in situ on the surface of hydrolyzed polyacrylonitrile (PAN) membrane. This thin layer exhibited both pH response due to the poly(acrylic acid) moiety and temperature response due to the pNIPAAm moiety. The swelling behavior of the membranes was evaluated under various temperatures and pH. The curve of the swelling ratio for the PAN‐NIPAAm showed a lower critical solution temperature. Then, conjugated linoleic acid (CLA) was loaded into the pNIPAAm layer. The effects of CLA on the blood coagulation and oxidative stress were evaluated with the use of human blood. The level of reactive oxygen species (ROS) was measured by the chemiluminescence (CL) method to evaluate the oxidative stress. Furthermore, the removal of bacterial endotoxin (lipopolysaccharide) by CLA‐loaded PAN‐NIPAAm was measured with enzyme‐linked immunosorbent assay. The results show that the LCST swelling curve was at 37°C. PNIPAAm chains form expanded structures under 37°C. At temperatures greater than 37°C, however, the chains form compact structures by dehydration. This makes PNIPAAM membrane due to rapid hydration and dehydration changes of the polymer chain. In addition, the swelling ratio increased by 71% when the pH increased from 5 to 10. The concentration of LPS can be reduced by CLA‐loaded PAN‐NIPAAm 2.1 and 1.2 times of that by unmodified PAN and PAN‐NIPAAm membranes, respectively. In addition, the level of ROS against CLA‐loaded PAN‐NIPAAm was reduced significantly than that against unmodified PAN and PAN‐NIPAAm. Therefore CLA‐loaded PAN‐NIPAAm membrane could offer protection for patients against oxidative stress and could also inhibit lipopolysaccharide for clinical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.