Effect of poly(ethylene glycol)-derived crosslinkers on the properties of thermosensitive hydrogels

Three crosslinkers, poly(ethylene glycol) diacrylate (PEGDA), glycerol ethoxylate triacrylate (GETA) and citric acid-(PEG acrylate)₃ (CA-PEGTA) derived from poly(ethylene glycol) (PEG) were synthesized at first. The three series of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels were prepared by photopolymerization with the crosslinkers and compared with a hydrogel based on commercial crosslinker, N,N′-methylene bis-acrylamide (NMBA). The influence of the crosslinker structures and contents on the swelling behaviour, mechanical properties, and drug release of the hydrogels was investigated. The results showed that the hydrogels based on PEGDA and NMBA exhibited the highest and the lowest swelling ratio, respectively. The content of crosslinker of all hydrogel series showed good thermosensitivity and thermo-reversibility. The critical gel transition temperature (CGTT) appeared at 32 °C for the hydrogel based on NMBA, but appeared at about 34 °C for other hydrogels due to higher hydrophilicity of the crosslinker. In the mechanical properties, three-arms crosslinker GETA and CA-PEGTA led to higher mechanical strength than a linear crosslinker PEGDA. A hydrogel based on GETA (NG6) showed the highest shear modulus of 656.9 kPa and Young’s modulus of 1655.0 kPa. The hydrogels containing higher content of crosslinker revealed lower swelling ratio and higher mechanical strength. In the drug release, the hydrogels with higher swelling ratios showed higher drug absorbed. The highest release percentage of caffeine and vitamin B12 for hydrogel based on PEGDA (NP6) could reach 68.3% and 75.4%, respectively. In addition, the bound water and toxicity of the hydrogels were also investigated.

     

Enhancing the crystallization and orientation of electrospinning poly (lactic acid) (PLLA) by combining with additives

Novel hydrogel films composed of hydroxyethylacryl chitosan (HC) and sodium alginate (SA) were prepared for biomedical application by using calcium chloride (CaCl₂) as a nontoxic ionic crosslinker to form a semi-interpenetrating polymer network (semi-IPN). HC was successfully prepared by following a Michael addition reaction of chitosan (CS) and hydroxyethylacrylate completely dissolved in distilled water at 70 °C. The distribution pattern of Ca²⁺ ions were well-dispersed within the hydrogel films examined by scanning electron microscope-energy dispersive spectrometry (SEM-EDS), implying uniformity of crosslinking. The swelling behavior of the hydrogel films in distilled water, simulated gastric fluid (SGF, pH?=?1.2) and phosphate buffer solution (PBS, pH?=?7.4) were investigated. The equilibrium swelling degree of the hydrogel films in distilled water increased with a decreas of either the SA content or the concentration of CaCl₂. The hydrogel films showed pH-dependent behavior in that the shapes of the hydrogel films were stable in SGF while they degraded in PBS. The tensile strength and elongation of the hydrogel films reached 12.1 MPa and 162%, respectively, which presented reasonable mechanical properties during use and enough flexibility to follow skin movement. Cell viability of the hydrogels was measured using a methylthiazol tetrazolium (MTT) assay. The results indicated that the hydrogel films are not cytotoxic.     

Synthesis and Characterization of Thermoresponsive Terpolymer for Protein Separation

Thermoresponsive hydrogels with fixed molar ratio (25 mol%) N-isopropylacrylamide (NIPAM) and different concentration of N-tertiary butylacrylamide (NTBA) and hydroxyethylacrylamide (HEAA) were synthesized and characterized. Differential scanning calorimetry indicated that the amount of the bound water and the bound water to total water ratio increased with increasing the hydrophobic NTBA in the hydrogel. The kinetic study of the swelling of hydrogels showed that all samples followed the non-Fickian type of diffusion. The separation efficiency of hydrogels having higher content of HEAA were found to be up to 90% at 5°C but it decreases upon raising the temperature up to 30°C.     

Preparation and properties of the novel photoluminescent and thermosensitive hydrogels

Bis[4-(phenyl-isopropyl)phenyl]-4-nitrophenylamine (BiPNPA) (iii) was firstly synthesized via nucleophilic substitution of 4-fluoronitrobenzene (ii) and bis-[4-(phenyl-isopropyl)phenyl]amine (BiPA) (i) in this study, and then compound (iii) was reduced to bis[4-(phenyl-isopropyl)phenyl]-4-aminophenylamine (BiPAmPA) (iv). At last, acrylation of BiPAmPA with acryloyl chloride was performed to obtain a novel bis[4-(phenyl-isopropyl)phenyl]-4-acrylamidophenylamine (BiPAcPA) compound (v). Then, a series of thermosensitive hydrogels were prepared by copolymerization of BiPAcPA and N-isopropyl acrylamide (NIPAAm) by UV irradiation. The effect of BiPAcPA content in the copolymeric hydrogels on the swelling ratio, mechanical properties, and drug release behaviors of the hydrogels was investigated. Results showed that the swelling ratios of the copolymeric hydrogels decreased from 8.2 (g/g) to 5.01 (g/g) when the monomer BiPAcPA content in the copolymeric hydrogel increased from 0.1 mol% to 0.9 mol%. In addition, the thermosensitive behavior obviously decreased with increasing of BiPAcPA content in the hydrogels, but the mechanical properties and crosslinking density of the hydrogel increased with increasing of BiPAcPA content; the caffeine release ratio from 46 % decreased to 29 %. The result of caffeine release also showed that the caffeine-loading amounts decreased with increasing content of BiPAcPA in the hydrogel, but their fractional release increased. In addition, the corresponding copolymers of the copolymeric hydrogels were prepared. Furthermore, the UV absorbance and photoluminescent (PL) behavior of the BiPAcPA, NIPAAm/BiPAcPA copolymeric hydrogels, and their corresponding copolymers in some solvents with different polarities were investigated. The results showed the PL intensity increased with increasing BiPAcPA amounts, especially the wavelength had obvious blue shift phenomenon in THF solvent. The wavelength of UV absorbance and PL emission of BiPAcPA all appeared in visible region. No matter what BiPAcPA monomer, NIPAAm/BiPAcPA hydrogels or NIPAAm/BiPAcPA copolymers, the wavelengths of UV absorbance and PL emission in DMSO solvent are all the same.     

Fabrication of anisotropic nanocomposite hydrogels by magnetic field-induced orientation for mimicking cardiac tissue

The ordered structure of biological tissues is a precondition for the development of high performance in these tissues. Hydrogels with anisotropic structures provide a good starting point for studying their biomimetic applications. In this work, a hydrogel that mimics the endogenous anisotropic structure of heart tissue was reported. The gel consists of acrylamide (AM) and 2-Acrylamide-2-methylpro panesulfonic acid (AMPS) as gel monomers, α-ketoglutaric acid as photoinitiator, and modified magnetic nanoparticles (Fe₃O₄-R_S) as crosslinking agent. Thus, AM, AMPS and Fe₃O₄-Rs was called AAF for short. In the system, the orientation of Fe₃O₄-Rs was arranged by an external magnetic field. Under ultraviolet (UV) irradiation, the precursor solution was polymerized in situ to form an AAF hydrogel. The structure, pore distribution, rheological properties, mechanical performance, swelling property, and biocompatibility of the prepared anisotropic AAF hydrogel were studied in this paper. Results showed that the mechanical performance of the AAF hydrogels was remarkably enhanced in comparison with the isotropic ones. The tensile strength of AAF hydrogel could reached 184 kPa in the direction of the parallel Orientation of Fe₃O₄-Rs, and 80 kPa in the direction of the vertical Orientation of Fe₃O₄-Rs under 25% strain (no magnetic field was applied during all test). Moreover, the anisotropic tensile ratio of AAF hydrogel also reached 2.3. The strength and modulus of anisotropic hydrogels were similar to cardiac tissue (anisotropic tensile ratio was 2.5), which has great potential for application in cardiac tissue engineering.     

Design and fabrication of a triple-responsive chitosan-based hydrogel with excellent mechanical properties for controlled drug delivery

A pH-, temperature- and salinity responsive hydrogel with enhanced mechanical performance was developed based on semi interpenetrating network that was formed as a result of concurrent free radical polymerization of acrylic acid (AA), oligo(ethylene glycol) methacrylate (OEGMA) and 2-(2-methoxyethoxy) ethyl methacrylate (MEO₂MA) along with chitosan (CS) for controlled drug delivery. The mechanical behaviors and swelling properties of these hydrogels were systematically investigated, and the results indicated that they were strongly affected by the content of AA and MEO₂MA and exhibited strong pH-, temperature and salinity sensitivity. Bovine serum albumin (BSA) and 5-Fluorouracil (5-Fu) were used as the model drugs to evaluate the sustained release of the hydrogel. The result indicated that the amount of both drugs released was relatively low in acidic condition (pH 1.2) but high in neutral environment (pH 7.4), and the release rate of the drugs was slower at 37 °C than that at 25 °C. Cytotoxicity results suggested that the blank hydrogels had negligible toxicity to normal cells, whereas the 5-Fu-loaded hydrogels remained high in cytotoxicity for LO2 and HepG2 cancer cells. These results suggest that the synthesized hydrogels have the potential to be used as an effective pH/temperature sustainable site-specific oral drug delivery in intestine and colon.     

Effect of crosslinkers on size and temperature sensitivity of poly(N-isopropylacrylamide) microgels

In this work, we study the effect of crosslinkers on the size and swelling properties of temperature sensitive N-isopropylacrylamide (NIPAAm) microgels produced by dispersion polymerization. The crosslinkers studied were N,N′-methylenebisacrylamide (MBA), ethylene glycol dimethacrylate (EGDMA) an 3,9-divinyl-2,4,8,10-tetra-oxaspiro[5.5] undecane (DVA). The type of crosslinker had a major impact on the size and swelling behavior, although the proportion of crosslinker used in each case was low (maximum 5 mol%). The effect can be related to the hydrophilic/hydrophobic characteristics of the crosslinkers. DVA produces smaller hydrogels with reduced swelling ratio, MBA produces bigger microgels with higher swelling ratio, while EGDMA results in an intermediate behavior. With increasing amount of crosslinker used in the synthesis, the extent of the swelling ratio decreases for DVA and EGDMA crosslinked microgels, while increases for MBA crosslinked microgels. There is also a slight effect on the critical transition temperature (T _c) of the microgels from 30 °C (DVA) to 34 °C (MBA) as observed in copolymers of NIPAAm with hydrophilic or hydrophobic comonomers.     

Templating polyacrylamide hydrogel for interconnected microstructure and improved performance

In this study, the pressure and temperature are monitored during acrylamide polymerization and their effects on the mechanical properties and swelling of the resulting hydrogel are investigated. The polymerization kinetic and network formation mechanism are correlated to the environmental thermodynamic conditions under which the hydrogels are polymerized. Then, the swelling and Young's modulus are measured and shown to be tunable along a wide range of values. The swelling ratio varies between 50 and 2262 while Young's modulus varies between 10.99 and 40.70 kPa. In addition, the formation of macroporous hydrogel with channel like structures along the vacuum direction under a reduced pressure of 5 mbar is reported. The macroporous hydrogel has a modulus of 40.70 kPa and shrink approximatively three times faster than the hydrogel polymerized under normal pressure and has a modulus of 10.99 kPa. Hence, this interconnected network can overcome the fluid diffusion limitations of bulk hydrogels without compromising the mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46205.     

Preparation of poly(acrylamide-co-2-acrylamido-2-methylpropan sulfonic acid)-g-Carboxymethyl cellulose/Titanium dioxide hydrogels and modeling of their swelling capacity and mechanic strength behaviors by response surface method technique

It is very important that new generation, unique, high mechanical strength, and biocompatible hydrogel composites are developed due to their potential to be used as biomaterials in the biomedical field. Modeling of the swelling capacity and mechanical strength behavior of hydrogels is a domain of steadily increasing academic and industrial importance. These behaviors are difficult to model accurately due to hydrogels show very complex behavior depending on the content. In this study, a series of poly(acrylamide-co-2-acrylamido-2-methylpropan sulfonic acid)-g-carboxymethyl cellulose/TiO₂ (poly(AAm-co-AMPS)-g-CMC/TiO₂) superabsorbent hydrogel composites were prepared by free-radical graft copolymerization in aqueous solution. Structural and surface morphology characterizations were conducted by using Fourier-transform infrared spectroscopy and scanning electron microscope analysis techniques. For modeling the equilibrium swelling capacity and fracture strength behaviors of hydrogels, the composition parameters (such as mole ratio of AMPS/AAm, wt% of CMC, and wt% of TiO₂) was proposed by response surface method (RSM) Design Expert-10 software. Statistical parameters showed that the RSM model has good performance in modeling the swelling capacity and mechanic fracture strength behaviors of poly(AAm-co-AMPS)-g-CMC/TiO₂ hydrogel composites. According to the RSM model results, the maximum swelling capacity and fracture strength values were calculated as 270.39 g water/g polymer and 159.23 kPa, respectively.     

Preparation of SMA functionalized sulfanilic acid hydrogels and investigation of their metal ions adsorption behavior

This study is concerned with the synthesis of some network polymers and their possibility of metal ions removal from aqueous solution. A chelating hydrogel based on modified poly(styrene-alt-maleic anhydride) with p-aminobenzene sulfonic acid (sulfanilic acid) was synthesized. This hydrogel was further reacted by 1,2-diaminoethane or 1,3-diaminopropane in presence of ultrasonic irradiation for preparation of tridimensional hydrogels. The prepared hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA/DTG) techniques. Also, the swelling index of the copolymers was measured and the results clearly indicate that the uptake of the water decreased with cross-linked hydrogels with respect to noncross-linked form. Adsorption capacity of the hydrogels for the selected metal ions, i.e., Zn(II), Cu(II) and Fe(II) was investigated in detail in aqueous solutions at pH 3–7 utilizing atomic absorption spectroscopy (AAS). Also the prepared hydrogels were examined for removal of metal ions from industrial wastewater samples. This study showed that the prepared cross-linked hydrogel is very efficient in chelating the selected metal ions from aqueous solutions, compared to noncross-linked hydrogel and the affinity order was: Fe(II) > Cu(II) > Zn(II). The equilibrium distribution coefficient (k _d) was determined and the findings proved that the k _d value is approximately high in the case of all measured metal ions.     

Synthesis of multifunctional high strength,highly swellable,stretchable and self‐healable pH‐responsive ionic double network hydrogels

The multifunctional double network (DN) soft hydrogels reported here are highly swellable and stretchable pH‐responsive smart hydrogel materials with sufficient strength and self‐healing properties. Such multifunctional hydrogels are achieved using double crosslinking structures with multiple physical and chemical crosslinks. They consist of a copolymer network of acrylamide (AM) and sodium acrylate (Na‐AA) and other reversible network of poly(vinyl alcohol)–borax complex. They were characterized by Fourier transform IR analysis and studied for their hydrogen bonding and ionic interaction. The degree of equilibrium swelling was observed to be as high as 5959% (at pH 7.0) for a hydrogel with AM/Na‐AA = 25/75 wt% in the network (GS‐6 sample). The highest degree of swelling was observed to be 6494% at pH 8.5. The maximum tensile strength was measured to be 1670, 580 and 130 kPa for a DN hydrogel (GS‐2 sample: AM/Na‐AA =75/25 wt% with 20, 40 and 60 wt% water content, respectively). The self‐healing efficiency was estimated to be 69% for such a hydrogel. These multifunctional DN hydrogels with amalgamation of many functional properties are unique in hydrogel materials and such materials may find applications in sensors, actuators, smart windows and biomedical applications. © 2018 Society of Chemical Industry     

Dual stimuli responsive glycidyl methacrylate chitosan‐quaternary ammonium hybrid hydrogel and its bovine serum albumin release

A new family of cationic hybrid hydrogels from two new positively charged aqueous soluble precursors, glycidyl methacrylate‐chitosan (GMA‐chitosan), and 2‐(acryloyloxy) ethyl trimethylammonium (AETA), was developed via a simple photocrosslinking fabrication method. These hybrid hydrogels have pendant quaternary ammonium functional groups on the AETA segments. The chemical composition of GMA‐chitosan/AETA hybrid hydrogels were characterized by Fourier transform infrared spectroscopy and their mechanical, swelling, and morphological properties were examined as a function of the composition of the hybrids as well as the effect of pH and ionic strength of the surrounding medium. GMA‐chitosan/AETA hybrid hydrogels show a porous network structure with average pore diameter 20–50 μm. The compression moduli of these hybrid hydrogels ranged from 27.24 to 28.94 kPa, which are significantly higher than a pure GMA‐chitosan (17.64 kPa). GMA‐chitosan/AETA hybrid hydrogel shows pH/ionic strength responsive swelling behavior because of the presence of the positive charge pendant groups. These hybrid hydrogels showed a sustained BSA protein release and a significantly lower initial burst release than a pure GMA‐chitosan hydrogel. The two aqueous soluble precursors and the cationic charge characteristics of the resulting GMA‐chitosan/AETA hybrid hydrogels may suggest that this new family of biomaterials may have promising applications as the pH responsive protein drug delivery vehicles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3736–3745, 2013     

Chitosan-graft-poly(acrylic acid)/rice husk ash based superabsorbent hydrogel composite: preparation and characterization

Rice husk ash (RHA), an industrial waste, was incorporated in the preparation of high performance chitosan (CTS) and poly(acrylic acid) (PAA) based superabsorbent hydrogel. Hydrogels filled with RHA previously calcinated at 900 °C (RHA₉₀₀) showed better water uptake (225 g_water/g_absorbent) than those with husk calcinated at 400 °C (RHA₄₀₀) (198 g_water/g_absorbent) due to the higher purity and crystallinity, at same composition. The hydrogel composite at 5 wt-% of RHA₉₀₀ showed the best water uptake (255 g_water/g_absorbent). A clear reduction in swelling degree is observed by increasing the amount of crosslinker from 1 to 3 wt-% due to the increase in the crosslinking density forming more rigid hydrogels. On the other hand, an increase in the initiator amount from 1 to 3 wt-% increased the water uptake due to the formation of greater numbers of active sites increasing the number of PAA chains grafted into CTS backbone. Furthermore, the hydrogel composites presented responsive behavior in relation to both pH and sat solution. The data shows it is possible to obtain high performance materials by incorporating an industrial waste, rice husk ash, in the preparation of hydrogel composites.     

Radical/Addition polymerization silicone hydrogels with simultaneous interpenetrating hydrophilic/hydrophobic networks

Transparent silicone hydrogels with interpenetrating hydrophilic/hydrophobic networks were simultaneously synthesized on the basis of the radical polymerization of the methacrylic monomer of 3‐methacryloxypropyl tris(trimethylsiloxy) silane (TRIS)/N,N‐dimethylacrylamide (DMA) and the addition polymerization of hydroxyl‐grafted polysiloxane (HPSO)/isophorone diisocyanate. The curing temperature was set at 80°C by a differential scanning calorimetry study. The polymerization process was studied by in situ Fourier transform infrared spectroscopy. The results indicate that the curing time was about 4.5 min, and the addition polymerization had a faster rate than radical polymerization. Then, the radical polymerization rate increased rapidly, and this led to instant curing. The interpenetrating polymer network (IPN) silicone hydrogels were characterized by swelling kinetics and dynamic mechanical thermal analysis. The results show that all of the hydrogels reached swelling equilibrium at about 4 h in water, and the IPN silicone hydrogels with a hydrophobic network of HPSO indicated a slower water transport than that of the copolymerization hydrogel of DMA and TRIS. The hydrophobic network was finely dispersed in the hydrophilic network, and the increasing hydrophobic network of HPSO decreased the glass‐transition temperature of the IPN silicone hydrogels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41399.     

Swelling behaviour and paracetamol release from poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-itaconic acid) hydrogels

Copolymer hydrogels of N-isopropylacrylamide and itaconic acid (IA), crosslinked with N,N′-methylenebisacrylamide, were prepared by radical copolymerization. These hydrogels were investigated with regard to their composition to find materials with satisfactory swelling and drug release properties. A paracetamol is used as a model drug to investigate drug release profile of the hydrogels. It was found that the investigated hydrogels exhibited pH- and temperature-dependent swelling behaviour with restricted swelling and lower equilibrium degree of swelling at lower pH values and temperatures above the LCST value of PNIPAM (around 34 °C). The diffusion exponent for paracetamol release indicate that the mechanism of paracetamol release are governed by Fickian diffusion, while in all release media initial diffusion coefficient was lower than late time diffusion coefficient. Furthermore, the paracetamol release rate depends on the hydrogel degree of swelling and it increased in the first stage of diffusion process, whereas was no significant difference thereafter. The presence of the IA moieties incorporated into the network weakened the shear resistance of the hydrogels. In order to calculate the pore size the characteristic ratio for PNIPAM, C _n  = 11.7, was calculated. Based on the pore size, the investigated hydrogels can be regarded as microporous. According to the obtained results swelling behaviour, mechanical properties, drug-loading capacity and the drug release rate could be controlled by hydrogel composition and crosslinking density, which is important for application of the investigated hydrogels as drug delivery systems.     

Compressive moduli and network parameters of N‐isopropylacrylamide hydrogels copolymerized by monoesters of itaconic acid and crosslinked with tetraallylammonium bromide

The present study focuses on the mechanical properties of hydrophilically or hydrophobically modified poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels, and all discussions on their improved mechanical strengths are based on the conformational effects of hydrophobic side chains attached to the comonomers and the structural differences between the crosslinkers. Three different types of monoalkyl itaconates, bearing octyl (Oc), cetyl (Ce), and cyclohexyl (CH) groups as comonomers, were used to prepare the copolymeric PNIPAAm hydrogels crosslinked with N,N′‐methylenebisacrylamide (BIS) and tetraallylammonium bromide (TAB) as neutral tetrafunctional and ionic octafunctional crosslinkers, respectively. The most striking result is the compressive E modulus of TAB‐crosslinked PNIPAAm hydrogel containing 10 mol % of mOcI. It reaches nearly 1.0 MPa and is independent of the temperature and pH of the swelling/shrinking medium. The result was discussed in terms of the inter/intramolecular interactions between hydrophobic octyl groups adopting a rod‐like conformation in the case of 25 °C/distilled deionized water (DDW) and 37 °C/DDW combinations. Further, it was observed that the electrostatic repulsive forces between the carboxylate groups on mOcI units could be suppressed even at 37 °C and pH 9 due to the rod‐like conformations of C₈H₁₇ groups. Its micrographs under bright‐field and polarized light supported the presence of an ordered anisotropic phase and multiple associations of extended, hydrophobic side chains. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45039.     

Synthesis of copolymeric acrylamide/potassium acrylate hydrogels blended with poly(vinyl alcohol): Effect of crosslinking and the amount of poly(vinyl alcohol) on swelling behavior

A novel series of copolymeric acrylamide/potassium acrylate superabsorbents, blended with poly(vinyl alcohol), have been synthesized by using N, N′‐methylenebisacrylamide as a crosslinker and potassium persulphate (K₂S₂O₈) as an initiator. Swelling behavior of these hydrogels in water was investigated; and on the basis of swelling properties, the diffusional behavior of water into these hydrogel systems was analyzed. It was observed that with the increase of amount of poly(vinyl alcohol) or crosslinking, the swelling of the hydrogels decreased. The hydrogel synthesized by addition of 5% poly(vinyl alcohol) and 0.25% crosslinking showed maximum swelling of 54445%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1927–1931, 2005     

水溶性Janus型POSS的设计合成及其对PAA/PAM水凝胶力学性能影响的研究

利用丙烯酰氧丙基多面体低聚倍半硅氧烷（Acrylo-POSS）和3-巯基-1-丙烷磺酸盐（MPS）之间的巯基点击反应，一步合成水溶性Janus型多面体低聚倍半硅氧烷（AS-POSS）。通过改变投料比可以调控AS-POSS的水溶性和双键与磺酸钠基团的物质的量比。将AS-POSS与丙烯酸（AA）和丙烯酰胺（AM）共聚制备了一系列不同AS-POSS含量的AS-POSS/PAA/PAM水凝胶，其中AS-POSS质量占单体总质量1%的1% AS-POSS/PAA/PAM水凝胶的平衡溶胀比达到512，断裂伸长率达到1074%，压缩强度为583 kPa，压缩应变为89%，屈服应变为330%，均大于对照组MBA/PAA/PAM水凝胶，表明AS-POSS的引入显著提高了水凝胶的溶胀度，明显增强了水凝胶的韧性、抗压缩性能和动态力学性能。AS-POSS/PAA/PAM水凝胶具有良好的导电性，离子电导率最高可达0.401 S/m。     

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.     

Swelling,pH sensitivity,and mechanical properties of poly(acrylamide‐co‐sodium methacrylate) nanocomposite hydrogels impregnated with carboxyl‐functionalized carbon nanotubes

A series of novel nanocomposite hydrogels were prepared by a cross‐linking copolymerization method. Structural and morphological characterizations of the nanocomposite hydrogels revealed that a good compatibility exists between poly(acrylamide‐co‐sodium methacrylate) [P(AM‐co‐SMA)] and carboxyl‐functionalized carbon nanotubes (MWNTs–COOH). The P(AM‐co‐SMA)/MWNTs–COOH nanocomposite hydrogels with a suitable MWNTs–COOH loading exhibited better swelling capability, higher pH sensitivity, good reversibility, and repeatability, and rapid response to external pH stimuli, compared with the P(AM‐co‐SMA). The compression mechanical tests revealed that the nanocomposite hydrogel displayed excellent compressive strengths and elastic mechanical properties, with higher ultimate compressive stress, and meanwhile still retain a good recoverable strain in the presence of MWNTs–COOH. These excellent properties may primarily be attributed to effectively dispersing of a suitable MWNTs–COOH loading into the matrix of the polymers and formation of additional hydrogen bonds. The nanocomposite hydrogels were expected to find applications in drug controlled release and issue engineering. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers