Development of Sodium Carboxymethyl Cellulose-based Poly(acrylamide-co-2acrylamido-2-methyl-1-propane sulfonic acid) Hydrogels for In Vitro Drug Release Studies of Ranitidine Hydrochloride an Anti-ulcer Drug

The formation of sodium carboxymethyl cellulose (SCMC) based semi-interpenetrating networks (semi-IPN) with poly(acylamide-co-2-acrylamido-2-methy-l-propanesulfonic-acid) hydrogels. The hydrogels were prepared by free-radical polymerization using redox initiator. The characterizations of hydrogels were done by swelling experiments, FTIR spectroscopy and DSC analysis. Morphology of the samples were examined by SEM. Experimental results indicate that the semi-IPN hydrogel containing 0.10 g of SCMC and 5.829 mM of AMPS, shows the highest swelling capacity (64.83 g/g). The swelling behavior of the semi-IPN hydrogel (AS5) was studied in different pH solutions. The ranitidine hydrochloride drug loading and release of the semi-IPN hydrogels were studied by using a UV spectrophotometer.     

Modification of Na-bentonite by polycations for fabrication of amphoteric semi-IPN nanocomposite hydrogels

Na-bentonite was modified by intercalation of poly(dimethyldiallylammonium chloride) (PDMDAAC). The XRD pattern and TEM image indicated that an exfoliated nanocomposite was obtained. Then, graft polymerization of acrylic acid onto starch was carried out to form an amphoteric nanocomposite hydrogels with semi-interpenetrating polymer networks (semi-IPN) in the dispersion of the nanocomposite. The swelling behavior of the hydrogels was studied in buffer solution at different pH. The amphoteric semi-IPN hydrogels had excellent pH-sensitivity in the range of pH from 2 to 4. The amphoteric semi-IPN hydrogels exhibited excellent compressive strength even at high water content.     

Investigation the correlation between chemical structure and swelling,thermal and flocculation properties of carboxymethylcellulose hydrogels

Hydrophilic polymer networks (hydrogels) based on sodium carboxymethylcellulose (NaCMC) and polycarboxylic acids (oxalic, succinic, citric and adipic) as cross-linking agents are synthesized by esterification reaction; one series of NaCMC hydrogels cross-linked with citric acid is prepared with acrylamide and acrylic acid (Aam/Aac) copolymers using the design of semi-interpenetrating polymer networks (semi-IPN), in order to increase their potential application for flocculation purposes. The Infrared spectroscopy (FTIR) of hydrogels confirms the esterification reaction between NaCMC and cross-linking agents. Results of swelling measurements show that citric acid in the amount of 15 wt% gives the hydrogels with the best absorption capacity. The results of Differential scanning calorimetry (DSC) and Thermal gravimetric analysis (TGA) show no significant difference in thermal properties of neat and semi-interpenetrating NaCMC hydrogels. The amorphous nature of hydrogels is confirmed by X-ray diffraction analysis (XRD). The results of flocculation study show that combination of NaCMC network and Aam/Aac copolymer with initial mass ratio of 10/90 creates a theoretical platform for the production of flocculant which could show high efficacy in purifying of water dominated by positively charged particles.     

pH敏感性P(AAm-co-AA)半互穿网络水凝胶的制备、表征及溶胀动力学研究

以N,N-亚甲基双丙烯酰胺(N,N-MBA)为交联剂、过硫酸钾(KPS)为引发剂,采用自由基交联共聚法合成了具有pH敏感性的半互穿网络水凝胶聚丙烯酰胺-co-丙烯酸[P(AAm-co-AA)],通过傅立叶红外光谱、差热分析研究了水凝胶的结构及热稳定性.水凝胶的溶胀研究表明,随着缓冲溶液pH值的增大平衡溶胀率增大;在不同...     

PAAm／PEG／PVP半互穿网络水凝胶的制备、表征及茶碱释放研究．

以N,N-亚甲基双丙烯酰胺（N,N-MBA）为交联剂、过硫酸钾（KPS）为引发剂·通过丙烯酰胺（AAm）、聚乙二醇（PEG）和聚乙烯吡咯烷酮（PVP）发生共聚反应制备具有半互穿网络结构的水凝胶PAAm／PEG／PVP。采用红外光谱（FTIR）、热重分析（TG）对水凝胶的结构和热学性质进行了分析,研究了中性条件下水凝胶的溶胀性能,并进一步研究了其负栽茶碱在不同缓冲溶液中的释放行为。     

pH敏感瓜胶/聚丙烯酸半互穿网络水凝胶研究

制备了瓜胶/聚丙烯酸(GG/PAA)的半互穿网络(sem i-IPN)水凝胶,以N,N-亚甲基双丙烯酰胺(MBA)为交联剂,考察了加料量、溶胀介质pH对平衡溶胀率(ESR)的影响。结果表明:GG/PAA半互穿网络水凝胶的ESR在pH≤3时较小,pH>4后增加较快,pH=8.2时达最大值,继续增加pH,ESR又呈下降趋势,体系具有pH敏感性。在pH相同条件下,ESR随GG用量增加而减小,随丙烯酸(AA)用量增加而增大。pH=8.2、ρ(GG)从5 g/L增加到25 g/L时,ESR从3 142降低到1 026;当ρ(AA)用量从125 g/L增加到375 g/L时,ESR从1 195增加到2 611。m(MBA)∶m(AA)=(0.5∶100)~(1.2∶100)时,ESR略有增加。GG/PAA半互穿网络水凝胶的溶胀动力学表明,该类凝胶满足在胃液pH环境中溶胀率较小、小肠部位pH环境中溶胀率较高的要求,因此,通过调整配方,结合瓜胶只被结肠部位细菌降解的特性,GG/PAA半互穿网络水凝胶有望成为一种理想的靶向结肠给药载体。     

Transparent and semi-interpenetrating network P(vinyl alcohol)- P(Acrylic acid) hydrogels: pH responsive and electroactive application

ABSTRACT

In this paper, poly(vinyl alcohol)-poly(acrylic acid) based transparent semi-interpenetrating network (semi-IPN) hydrogels were synthesized by using a solvent mixture of dimethyl sulfoxide and deionized water via free radical polymerization and subsequent freeze-thaw technique. The formation of the semi-IPN hydrogels was conformed from FT-IR spectra. The acrylic acid concentration effect on the hydrogels was investigated in terms of transparency, crystalline structure and thermal stability by using UV-visible spectroscopy, X-ray diffraction and thermogravimetric analysis. Swelling behaviours of the semi-IPNPAP hydrogels were studied in deionized water and different pH solutions. The compression and electroactive behaviour was tested in fully hydrated stage by using compression test and by applying electrical voltage. The hydrogels showed displacements under the applying voltage and detailed experiment is illustrated.     

Temperature and pH sensitive hydrogels composed of chitosan and poly(ethylene glycol)

Summary Chitosan based semi-interpenetrating polymer network (semi-IPN) hydrogels containing different amounts of poly(ethylene glycol) (PEG) were prepared. The crosslinking of the hydrogels was achieved by using a naturally occurring nontoxic cross-linking agent genipin. The swelling behaviour of these hydrogels was studied by immersing the films in deionized water at 25, 37 and 45 °C and in media of different pHs at 37 °C. Swelling was found to be dependent on temperature, pH of the medium and the amount of PEG in the gel. States of water in the hydrogels swollen in deionized water at 37 °C were determined using Differential Scanning Calorimetry (DSC). The equilibrium water content and the amount of freezing water in the swollen hydrogels increased with the increase in PEG concentration in the gels.     

Assembly, characterization of Ag nanoparticles in P(AAm-co-NVP)/CS semi-IPN, and swelling of the resulting composite hydrogels

Silver nanoparticles (AgNPs) with controlled size and size distribution were prepared by an in situ chemical reduction route based on a microreactor template composed of poly(acrylamide-co-N-vinylpyrrolidone)/chitosan semi-interpenetrating network hydrogels, P(AAm-co-NVP)/CS semi-IPN, in the presence of sodium hypophosphite. The characterization of structures and morphologies of the as-fabricated P(AAm-co-NVP)/CS–Ag nanocomposite hydrogels was conducted on a Fourier transformation infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV–vis spectrometer. The effect of various component proportions of the reactants on formation of AgNPs and swelling of the resulting P(AAm-co-NVP)/CS–Ag nanocomposite hydrogels was investigated. The experimental results indicated that the Ag grains were uniformly dispersed within P(AAm-co-NVP)/CS hydrogel networks in a spherical shape, and were stabilized by the semi-IPN structure and a complexation and/or electrostatic interaction between Ag⁺ cations and chemical functional groups, such as –OH, –CONH₂, –NH₂ or –C=O based on the semi-IPN structure reactor templates. The size of the majority of AgNPs ranges from 12 to 25 nm, depending on the three-network templates, the presence of functional groups as well as feed ratios of N-vinylpyrrolidone, acrylamide, and chitosan. Thermogravimetric analysis (TGA) provides the stability of the resulting nanocomposite hydrogels. The nanocomposite hydrogels demonstrate reduced swelling in comparison with the P(AAm-co-NVP)/CS ones. The kinetics modeling confirms that transport mechanism of the samples follows anomalous diffusion mode, and the kinetic parameters vary with the component ratios, and the maximal theoretical water volume S _∞ is well in agreement with the experimental values.     

Poly(vinyl alcohol) Based pH Responsive Semi-IPN Hydrogels: A Comparative Swelling Investigation

The semi-interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and random copolymers of poly(acrylamide-co-sodium methacrylate), poly(AAm-co-NMA); poly(acrylamide-co-potassium methacrylate), poly(AAm-co-KMA); poly(acrylamide-co-maleic acid), poly(AAm-co-MA) were prepared by conventional co-polymerization employing ammonium persulphate (APS)/N,N,N¹,N¹-tetraethylmethylenediamine (TMEDA) as redox initiating system in presence of N,N¹-methylenebisacrylamide (MBA) as a crosslinker. The swelling behavior of these semi-IPN hydrogels were compared in detail in various swelling media, including different pH, salt, and biological fluids.     

The usability of (sodium alginate/acrylamide) semi-interpenetrating polymer networks on removal of some textile dyes

In this study, (sodium alginate/acrylamide) interpenetrating polymer networks ((NaAlg/AAm)IPN) have been prepared at definite composition. The aqueous solution of 3% (w/v) sodium alginate and 50% (w/v) acrylamide was irradiated with ⁶⁰Co-γ rays at a dose rate of 0.07 kGy/h up to 5 kGy. The percent conversion was determined gravimetrically and 100% gelation was achieved at 5 kGy dose. To understand whether the semi-interpenetrating polymer network of sodium alginate is performed, Fourier Transform Infrared (FTIR) spectra of polyacrylamide (PAAm), sodium alginate, and the semi-interpenetrating polymer network were recorded. It is found that the FTIR spectra of PAAm, NaAlg, and the semi-interpenetrating polymer network are different. The thermograms of PAAm, sodium alginate, and the semi-interpenetrating polymer network were recorded for investigating their thermal character. (NaAlg/AAm)IPN hydrogels were immersed to swell in a solution of pH 7, at a temperature of 25°C. The swelling results at pH 7.0 indicated that (NaAlg/AAm)IPN hydrogel, containing 3% NaAlg showed maximum % swelling in water but swelling increased in the order of water > Magenta > Methylene Blue > Safranine-O > Methyl Violet. Diffusion of water and aqueous solution of dyes within (NaAlg/AAm)IPN hydrogels was found to be of Fickian character at the initial stage of swelling with regard to values calculated for diffusion coefficient of (NaAlg/AAm)IPN hydrogels in water and aqueous solution of dyes. Some diffusion parameters were calculated from swelling of (NaAlg/AAm)IPN in water and dyes and their adsorption isotherms were plotted. In the adsorption experiments, the efficiency of (NaAlg/AAm)IPN hydrogels to adsorb Magenta, Safranine-O, Methylene Blue, and Methyl Violet dyes from water was studied. (NaAlg/AAm)IPN hydrogels showed different adsorption for different aqueous solution of dyes at pH 7.0. Adsorption isotherms were constructed for (NaAlg/AAm)IPN-dye systems. S type adsorption in the Giles classification system was found. Thermal and spectroscopic characterization of semi-interpenetrating polymer network of sodium alginate and acrylamide and dye adsorbed semi-interpenetrating polymer network of sodium alginate and acrylamide was recorded. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel semi-interpenetrated networks based on collagen-polyurethane-polysaccharides in hydrogel state for biomedical applications

The development of collagen hydrogels with tailored properties for improved applications in biomedicine represents an area of opportunity for materials science. The collagen can form semi-interpenetrated networks (semi-IPN) with various natural and/or synthetic polymers. This work aims the preparation of novel hydrogels generated from a collagen matrix cross-linked with polyurethane (PU), and the subsequent inclusion of polysaccharide chains to form semi-IPN systems with improved properties. The choice of polysaccharides for this purpose is related to their ability to modulate the biocompatibility and the antibacterial capacity in various biomedical strategies. The work contemplates to study the effect of the chemical structure of polysaccharide (hydroxyethylcellulose (HEC), hydroxypropylmethylcellulose (HPMC) or starch (Alm)) on the properties of these novel hydrogels. The results indicate that the semi-IPN hydrogels that include Alm exhibit the formation of stronger intermolecular interactions promoted by hydrogen bonds than HEC and HPMC, significantly improving the mechanical properties and their degradation rate in acidic, alkaline, and proteolytic media; also showing high capacity to inhibit the growth of E. colli. The semi-IPN hydrogels based on HEC and HPMC exhibit excellent improvement in both thermal and proteolytic degradation, compared with the collagen-PU matrix. On the other hand, this semi-IPN system does not present cytotoxic character for monocytes and fibroblasts growing for up to 48 h of culture. Therefore, these innovative 3D matrices will be excellent candidates with potential application in biomedical strategies such as wound healing dressings.     

Effect of hydrophobic polystyrene microphases on temperature-responsive behavior of poly(N-isopropylacrylamide) hydrogels

Reversible addition-fragmentation chain transfer polymerization was employed to prepare the crosslinked poly(N-isopropylacrylamide)-graft-polystyrene networks (PNIPAAm-g-PS). Due to the immiscibility of PNIPAAm with PS, the crosslinked PNIPAAm-g-PS copolymers displayed the microphase-separated morphology. While the PNIPAAm-g-PS copolymer networks were subjected to the swelling experiments, it is found that the PS block-containing PNIPAAm hydrogels significantly exhibited faster response to the external temperature changes according to swelling, deswelling, and reswelling experiments than the conventional PNIPAAm hydrogels. The improved thermo-responsive properties of hydrogels have been interpreted on the basis of the formation of the specific microphase-separated morphology in the hydrogels, i.e., the PS blocks pendent from the crosslinked PNIPAAm networks were self-assembled into the highly hydrophobic nanodomains, which behave as the microporogens and thus promote the contact of PNIPAAm chains and water. The self-organized morphology in the hydrogels was further confirmed by photon correlation spectroscopy (PCS). The PCS shows that the linear model block copolymers of PNIPAAm-g-PS networks were self-organized into micelle structures, i.e., the PS domains constitute the hydrophobic nanodomains in PNIPAAm-g-PS networks.     

Shape-memory behavior of poly (methyl methacrylate-co –N-vinyl-2-pyrrolidone) / poly (ethylene glycol) semi-interpenetrating polymer networks based on hydrogen bonding

Based on hydrogen bonding interactions, Poly(methyl methacrylate-co-N-vinyl-2-pynolidone) (P(MMA-co-VP)) networks and linear poly(ethylene glycol) (PEG) can form semi-interpenetrating polymer networks (semi-IPNs), i.e. P(MMA-co-VP)/PEG semi-IPNs, which has shape memory behaviour; its maximum storage modulus ratio can be more than 400, and its shape recovery ratio could reach 99%. The morphology, thermal behaviors and dynamic mechanical properties of P(MMA-co-VP)/PEG semi-IPNs were studied by FTIR, TEM, DSC and DMA. When PEG with higher molecular weight was introduced into P(MMA-co-VP) networks, they possess higher glassy state modulus and higher recovering rate. In such a system, the maximum molecular weight of PEG required for the semi-IPN formation reaches 1000.     

Synthesis and Characterization of Temperature-Sensitive Poly(N-isopropylacryamide) Hydrogel with Comonomer and Semi-IPN material

A series of temperature and pH sensitive hydrogels were synthesized using N-isopropylacrylamide (NIPAAm) as main monomer, sodium alginate (SA) as semi-IPN material, ethyl acrylate (EA) and acrylic acid (AA) as comonomer, and N-maleyl chitosan (N-MACH) as cross-linker. The temperature and pH sensitive behavior, swelling/deswelling kinetics of the hydrogels were investigated. And the mechanism of the phase transition was summed up. Sodium alginate/Poly(N-isopropylacryamide) semi-interpenetrating polymer network (SA/PNIPAAm semi-IPN) hydrogels exhibited a lower critical solution temperature (LCST) at about 32 °C with no significant deviation from the conventional PNIPAAm hydrogels. Poly(N-isopropylacryamide-co-ethyl acrylate) (P(NIPAAm-co-EA)) hydrogels exhibited LCST at 29–31°C, increasing the amount of EA in the hydrogel gradually decreased the LCST. Poly(N-isopropylacryamide-co-acrylic acid) [P(NIPAAm-co-AA)] hydrogels exhibited LCST at 34–39°C, with decreasing NIPAAm/AA from 96/4 to 92/8 and 90/10, the LCST increased from 34°C to 37°C and 39°C. In the swelling/deswelling kinetics, all the dried hydrogels exhibited fast swelling/deswelling behavior, which might be attributed to macroporous structures of the hydrogels.     

Dynamic mechanical study of filled semi-interpenetrating polymer networks: Influence of γ-Fe2O3 on microphase structure

The preparation of filled two-component semi-interpenetrating polymer networks (semi-IPNs) is described and the results of an investigation of their morphology by means of dynamic mechanical spectroscopy are considered. The influence of an active dispersed filler (γ-Fe₂O₃) on the semi-IPNs phase structure is studied. A comparison is made between filled and unfilled semi-IPNs consisting of compatible or incompatible polymers. In the case of a semi-IPN of compatible polymers, the introduction of γ-Fe₂O₃ was observed to cause phase separation. With a two-phase semi-IPN the introduction of the filler enhanced the phase separation. The presence of two distinct peaks (the dynamic glass transition temperatures) corresponding to those of the two initial homopolymers shows the semi-IPN to have a two-phase structure.     

基于动态共价键的pH响应自修复水凝胶制备与评价

以α-甲基丙烯酸、2-丙烯酰胺-2-甲基丙磺酸共聚产物和聚乙烯醇为单体，十水合四硼酸钠为交联剂合成P(MAA /AMPS)-PVA二重互穿网络的pH响应水凝胶；通过扫描电子显微镜(SEM)、红外光谱(FTIR)、凝胶渗透色谱（GPC）、热重分析(DSC-TG)和流变仪等表征了水凝胶的表面形貌和化学状态；测定了水凝胶的溶胀性﹑pH响应性﹑自修复性和流变性。结果表明，水凝胶形成稳定的IPN互穿网络结构且该水凝胶具pH敏感性、自修复性；PVA羟基与硼酸根离子形成的共价配位硼酸酯键决定水凝胶自修复性并受到介质酸碱控制；力学性能测定结果显示，自修复水凝胶拉伸强度668 kPa,断裂伸长率可达665%，修复效率可达81%。     

Investigation of the preparation and physical properties of a novel semi-interpenetrating polymer network based on epoxised NR and PVA using maleic acid as the crosslinking agent

Natural rubber (NR) and its derivatives as renewable and biodegradable materials have attracted considerable attention because of the serious pollution problems caused by synthetic materials and a shortage of resources. A new semi-interpenetrating polymer network (semi-IPN) based on epoxidised natural rubber and polyvinyl alcohol containing maleic acid as a crosslinking reagent was synthesized and characterized by FTIR, XRD, SEM, swelling ratio in both distilled water and toluene, and mechanical properties. The curing time and dose of maleic acid were varied from 10 to 60 min, and from 10 to 60% (w/w), respectively. An IR spectroscopic study indicated the presence of an ester linkage at 1730 cm⁻¹ in maleic acid crosslinked with PVA in semi-IPN films. In addition, the crystalline content of PVA dramatically decreased after adding maleic acid in the semi-IPN, as observed from its XRD. The semi-IPNs exhibit good mechanical properties, thermal stability, characteristics of a polyvinyl alcohol–maleic acid polymer network. An SEM of the semi-IPNs containing maleic acid showed no phase separation, when compared with the sample prepared in the absence of maleic acid.     

pH- and thermo-sensitive semi-IPN hydrogels composed of chitosan, <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide,and poly(ethylene glycol)-<Emphasis Type="Italic">co</Emphasis>-poly(ε-caprolactone) macromer for drug delivery

In this study, semi-IPN chitosan/poly(N-isopropylacrylamide) (PNIPAAm) hydrogels have been prepared via in situ UV-photo-crosslinking of N-isopropylacrylamide monomer using poly(ethylene glycol)-co-poly(ε-caprolactone) (PEG-co-PCL) macromer as a crosslinker in the presence of chitosan. Swelling properties of the resultant hydrogels were studied by investigating pH- and temperature dependence of equilibrium swelling ratio and oscillatory swelling–deswelling kinetics. It was found that semi-IPN hydrogels responded to both temperature and pH changes, and such stimuli-responsiveness was rapidly reversible. The rheological measurements demonstrated that the incorporation of chitosan greatly improved the mechanical strength of the hydrogels prepared. The release profiles of bovine serum albumin (BSA) from the hydrogels were also evaluated. The results showed that the release rate of BSA was higher in pH 2.0 buffer solution than in pH 7.4 buffer solution at 37 °C. Such double-sensitive hydrogels have the potential to use as smart carriers for drug delivery systems.     

Introduction of silica into thermo-responsive poly(N-isopropyl acrylamide) hydrogels: A novel approach to improve response rates

The response rates of novel thermo-responsive poly(N-isopropyl acrylamide) (PNIPAM) hybrid hydrogels are compared to those of conventional chemically crosslinked PNIPAM hydrogels. The former materials were obtained by applying the sol-gel technology, in which the inorganic silica particles act as physical crosslinks for the organic polymer chains, leading to a semi-interpenetrating polymer network structure. In situ modulated temperature DSC shows that the introduction of hydrophilic silica improves the thermal response rate of the hybrid hydrogels to a great extent as compared to aqueous PNIPAM solutions and conventional PNIPAM hydrogels. Ex situ gravimetrical measurements also illustrate that the shrinking/swelling rate of the hybrid hydrogels is largely improved. It is assumed that the uniform distribution of the SiO₂ units, as demonstrated by cryo-field emission scanning electron microscopy, causes the silica to act as nano-sized water reservoirs, which reduce the characteristic diffusion length of water in the PNIPAM matrix so that it can be transported faster within the hybrid PNIPAM nano-composite.