Crosslinking reactions and swelling behavior of matrices based on N-acryloyl-TRIS(hydroxymethyl)aminomethane

Summary In this study, new hydrogels in rod shape were prepared from N-acryloyl-TRIS(hydroxymethyl)aminomethane (NAT) using ethylene glycol dimethacrylate (EGDMA) or N,N’methylenebisacrylamide (BIS) as crosslinking agent, dimethylformamide (DMF) as solvent and benzoyl peroxide (BPO) as initiator. In most cases, 2-hydroxyethyl methacrylate (HEMA), acrylamide (Aam) or acrylic acid (Aac) were used as co-monomers. The polymeric matrices obtained by free radical polymerization exhibited different properties by changing crosslinker, crosslinker concentration, co-monomer and initial NAT/co-monomer mole ratio. Besides, hydrogels from HEMA, Aam and Aac with BIS in absence of NAT were prepared under the same experimental reaction conditions in order to compare the properties of these products with those synthesized from NAT and the respective co-monomers. Some of the final products were selected to perform urea release assays, conducted through swelling-controlled release. Urea was chosen as “model” plant fertilizer agent.     

Preparation of Sodium carboxymethylcellulose/poly(methyl acrylate) IPN hydrogels and their application for adsorption

Sodium carboxymethylcellulose/poly(methyl acrylate) (NaCMC/PMA) interpenetrating polymer networks (IPNs) were prepared by fractional step in 40 wt % ethanol solution with N,N′‐methylenebisacrylamide as a crosslinker. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimeter were used to characterize the NaCMC/PMA IPN hydrogels and confirm the IPN structure as well. Simultaneously, adsorption of the obtained IPN hydrogels to methylene blue (MB) was also investigated. It was observed that the adsorption of MB onto the hydrogels was mainly dependent on the initial concentration of MB and the pH of the solution. Adsorption rate of MB was much higher in the first 9 h than that in the following period and saturated adsorption amount of MB was 2370 mg/g at the initial MB concentration of 100 mg/L. Moreover, the adsorption capacity of the IPN hydrogels at the neutral pH condition is much higher than those at acid or alkaline pH conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41101.     

Functionalized galactoglucomannan‐based hydrogels for the removal of metal cations from aqueous solutions

New types of hydrogels derived from O‐acetyl galactoglucomannan (AcGGM) hemicellulose have been synthesized and characterized. The objective of this work was to analyze the sorption capacity (S) of three types of hydrogels containing AcGGM derivatives incorporated into the carboxylic groups of the polymer chain in the AA hydrogel, sulfonic groups in the APA hydrogel, and amide groups in the acrylamide (Aam) hydrogel. These hydrogels are capable of interacting and removing ions such as cadmium [Cd(II)], copper [Cu(II)], lead [Pb(II)], nickel [Ni(II)], and zinc [Zn(II)]. The results show that AA and Aam hydrogels had a lower sorption capacity of ions compared to the APA hydrogel, which had a high sorption capacity. The maximal sorption capacity was determined by the successive enrichment method, obtaining Pb(II) amount of 48.3 mg/g of AA hydrogel, 65.8 mg/g of APA hydrogel, and 40.8 mg/g of Aam hydrogel. Hence, Pb(II) ions are greatly retained by the three hydrogels. These results are promising for the development of new materials with potential applications in metal ion removal. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44093.     

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     

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...     

聚乙烯吡咯烷酮半互穿网络智能凝胶的合成和电场行为研究

利用化学交联法,制备了由聚乙烯吡咯烷酮(PVP)和丙烯酰胺(Am)、丙烯酸(AA)复合的具有半互穿网络(Semi-IPNs)结构的高分子水凝胶。研究了凝胶在直流电场作用下NaCl溶液中的溶胀、弯曲行为及交联剂含量、PVP含量对水凝胶的溶胀性质、拉伸强度的影响。结果表明凝胶的最大弯曲率随着时间和电场强度的增加而增大,随溶液离子浓度的增加呈现出最大值。增加PVP可以提高拉伸强度降低弯曲度,适当增加交联剂,可以加强拉伸强度108.51%,降低溶胀度68.29%。     

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.     

Swelling and Thermal Characteristics of Genipin Crosslinked Chitosan and Poly(vinyl pyrrolidone) Hydrogels

Summary Chitosan / poly(vinyl pyrrolidone) (PVP) were used to prepare semi-interpenetrating polymeric networks. The hydrogels were crosslinked using genipin, a non-toxic cross-linking agent extracted from the fruits of Gardenia jasminoides Ellis. Swelling properties of these hydrogels were studied in media of different pHs and temperatures. States of water in the swollen hydrogels at 25°C and pH 7 were determined using Differential Scanning Calorimetry (DSC). The swelling behaviour of the hydrogels was found to be dependent on the temperature and the pH of the swelling medium. The total water content in the hydrogels was found to increase with increasing PVP content.     

Polymerization of glycidyl methacrylate,methacrylic acid,acrylamide and their mixtures with cotton fabric using fe2+-thioureadioxide-H2O2 redox system

Polymerization of glycidyl methacrylate (GMA), methacrylic acid (MAA), acrylamide (Aam) and their binary mixtures with cotton cellulose fabrics using Fe²⁺-thioureadioxide-H₂O₂ redox system was investigated under a variety of conditions. While temperatures of 50, 80, 65, and 95°C constituted the optimal polymerization temperature for GMA, MAA, Aam and GMA/MAA (8:2), respectively, maximum polymerization of GMA/MAA (2:8), Aam/MAA (8:2) and Aam/MAA (2:8) occurred at 75°C. The polymerization reaction proceeded initially very fast then levelled off irrespective of the monomer or monomer mixtures used. However, the magnitude of the polymer add-on at levelling off of polymerization followed the order GMA > GMA/MAA (2:8) ≥ GMA/MAA (8:2) > Aam/MAA (2:8) ≥ MAA ≥ Aam/MAA (8:2) > Aam. The polymer add-on enhanced by increasing the H₂O₂ concentration up to a certain limit and then decreased. The same situation was encountered with respect to thioureadioxide concentration. The involvement of the epoxy ring of GMA with MAA during polymerization of their mixture with cellulose occurred only at a higher ratio of GMA in the mixture. Also a significant contribution of Aam in the polymer add-on obtained with a Aam/MAA mixture could only be achieved at a higher ratio of Aam in this mixture.     

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.     

Swelling and Shrinking Properties of Thermo-Responsive Polymeric Ionic Liquid Hydrogels with Embedded Linear pNIPAAM

In this study, varying concentrations of linear pNIPAAM have been incorporated for the first time into a thermo-responsive polymeric ionic liquid (PIL) hydrogel, namely tributyl-hexyl phosphonium 3-sulfopropylacrylate (P-SPA), to produce semi-interpenetrating polymer networks. The thermal properties of the resulting hydrogels have been investigated along with their thermo-induced shrinking and reswelling capabilities. The semi-interpenetrating networks (IPN) hydrogels were found to have improved shrinking and reswelling properties compared with their PIL counterpart. At elevated temperatures (50–80 °C), it was found that the semi-IPN with the highest concentration of hydrophobic pNIPAAM exhibited the highest shrinking percentage of ~40% compared to the conventional P-SPA, (27%). This trend was also found to occur for the reswelling measurements, with semi-IPN hydrogels producing the highest reswelling percentage of ~67%, with respect to its contracted state. This was attributed to an increase in water affinity due to the presence of hydrophilic pNIPAAM. Moreover, the presence of linear pNIPAAM in the polymer matrix leads to improved shrinking and reswelling response compared to the equivalent PIL.     

Morphology and mechanical properties of styrene-butadiene-styrene/polystyrene semi-interpenetrating polymer networks and their blends

SBS/PS semi-interpenetrating polymer networks (semi-IPNS) were synthesized by swelling a linear styrene-butadiene-styrene (SBS) triblock copolymer (SBS, Kraton 1102) with styrene monomer plus benzoin as photoinitiator and divinylbenzene as cross-linking agent. Polyblends were prepared by solution casting of SBS and polystyrene (PS) in their ideal solvents. Measurements were made for viscoelastic properties and mechanical properties of phase-separated polymer alloy (including SBS copolymers Kraton 4122), semi-IPNs and polyblends of several SBS and PS, with the same total PS content (48% PS). The dynamic mechanical behaviour shows distinct transitions for each polymer, in agreement with electron microscopy results that SBS/PS polymer alloy forms two phases; however, the phase domains were finer in the semi-IPNs than in SBS triblock copolymer and in polyblends of the corresponding polymers. Stress-strain data show that semi-IPNs exhibit higher tensile strength and modulus than the other two corresponding polymer alloys. A master curve was plotted to illustrate the stress relaxation behaviour of samples at higher temperatures. Our results also reveal that semi-IPNs have much better high-temperature mechanical strength.     

Dye Sorption and Water Uptake Properties of Crosslinked Acrylamide/Sodium Methacrylate Copolymers and Semi-Interpenetrating Polymer Networks Composed of PEG

A series of novel semi-interpenetrating polymer networks hydrogels composed of poly(ethylene glycol) and random copolymer of acrylamide/sodium methacrylate were prepared by polymerization of aqueous solution of acrylamide, sodium methacrylate using ammonium persulphate/N,N,N′,N′-tetramethylethylenediamine as a redox-initiating pair in the presence of poly(ethylene glycol) and poly(ethylene glycol)diacrylate as crosslinker. Fourier Transform Infrared spectroscopy was used to identify the presence of different repeating units in the semi IPNs. Water uptake and dye-sorption properties of acrylamide/sodium methacrylate hydrogels and acrylamide/sodium methacrylate/poly(ethylene glycol) semi IPNs were investigated as a function of chemical composition of the hydrogels. Cationic dye, Janus Green B have been used in sorption studies as a model molecule. This study has given the quantitative information on the swelling and sorption characteristic of acrylamide/sodium methacrylate hydrogels and acrylamide/sodium methacrylate/poly(ethylene glycol) semi IPNs in many potential applications.     

Superabsorbent hydrogels from poly(aspartic acid) with salt-, temperature- and pH-responsiveness properties

Polyaspartic acid (PAsp) resin was synthesized by polysuccinimide (PSI), through chemical cross-linking using the cross-linking agent (diamine). The effects of reaction variables, such as PSI concentration and terminal pH on the water absorbent capacity have been studied. These phenomena were discussed according to structural parameters, which were confirmed by SEM. Water absorbencies were compared for the hydrogels at terminal pH 8 and 10. The water absorbent capacity enhanced with increasing terminal pH and decreasing PSI concentration. The swelling/deswelling kinetics of the super-absorbent hydrogels was investigated as well. It is found that the hydrogels showed ampholytic and reversible pH-responsiveness properties. The variational water absorbencies were attributed to swelling theory based on the hydrogel physical and chemical structure. The swelling was also extremely sensitive to the temperature, ionic strength and cationic kind. The reversible pH-responsiveness, salt- and temperature-sensitivity of the hydrogels make this intelligentized polymer had wider applications.     

Confinement effects on the kinetics of formation of sequential semi-interpenetrating polymer networks

Summary Peculiarities of formation kinetics of sequential semi-interpenetrating polymer networks based on crosslinked polyurethane with different cross-linking density and linear polystyrene and polybutylmethacrylate have been studied. Polyurethane networks were synthesized differing in molecular mass M_c of the chains between cross-links. Monomeric styrene and butyl methacrylate were introduced into these networks by swelling them in monomers up to equilibrium. The kinetics of polymerization of monomers in swollen networks was investigated. The experimental data show the dependence of the kinetic parameters of polymerization on M_c, this dependence being different for various monomers. Sharp discrepancy in molecular mass distribution of polymers formed in various matrices has been observed. The differences in dependencies of reaction kinetics and molecular mass distribution are supposed to be connected to various dependence of the chain growth and termination of various monomers on the density of network, i.e. on the confinements imposed by the intranetwork space.     

SO4^2-／TiO2／La^3＋型固体超强酸催化合成柠檬酸三丁酯

研究了以柠檬酸和正丁醇为原料、固体超强酸SO4^2-／TiO2／La^3＋为催化剂合成增塑剂柠檬酸三丁酯。合成柠檬酸三丁酯的最佳条件为：醇酸物质的量比为1：3．6．催化剂固体超强酸SO4^2-／TiO3/La^3＋用量为0．6％（质量分数）,适宜的反应时间为2．0h,酯化反应收率达93．1％。     

Poly(N-isopropylacrylamide) Hydrogels Crosslinked by Small-Molecular Crosslinkers Through Click Chemistry

A well-defined azido-poly(N-isopropylacrylamide) (PNIPA) was prepared by reversible addition-fragmentation chain transfer polymerization of NIPA and glycidyl methacrylate followed by the azidization of pendant epoxyl groups. Then the polymer was crosslinked via Click chemistry by bis- or tetra-alkynyl terminated compounds, which were synthesized through esterification of 1,3-propanediol and pentaerythritol with propiolic acid and 6-heptynoic acid, to fabricate PNIPA hydrogels. And the swelling properties of obtained hydrogels were studied as functions of crosslinker dosage and species. The results showed that the decrease of crosslinker dosage or increase of chain length thereof could enhance swelling capacities of hydrogels due to bigger free volumes within networks; the functionality of crosslinkers almost had no influence on swelling properties of hydrogels. In addition, no obvious distinction was found for lower critical solution temperature and swelling response to a temperature jump during reswelling and deswelling course, no matter what and how much crosslinker was used.     

Cation exchange finishing of nonwoven polyester with polycarboxylic acids and cyclodextrins

We describe a chemical method for the finishing of polyester nonwoven fabrics that aimed to obtain ion exchange textiles. This approach was based on the use of polycarboxylic acids (PCA) and cyclodextrins as carbohydrate compounds and finishing agents, respectively. It was observed that the reaction between these reactants yielded a crosslinked polymer that was physically anchored onto the fibers. This polymer can be considered as a resin issued from the esterification between the COOH groups of the PCA with the OH groups of the carbohydrate. As the esterification reaction was not complete, many free carboxylic groups remained on the surface of the coating polymer. This feature offered the ion exchange properties to the textile support. In this article, we described the pad‐dry‐cure process and showed the influence of the curing parameters (time and temperature), the nature, and the concentration of the components and the pH of the impregnating bath. The grafting rate (in wt %) and the ion exchange capacity (IEC) were observed in parallel. First, it was observed that the best IEC capacity (that could reach 1 mmol/g) was obtained when an ideal compromise was applied between time and temperature of curing. We also evidenced that IEC depended on the nature and on the concentration of the PCA (chosen among citric acid, 1,2,3,4‐butanetetracarboxylic acid, and polyacrylic acid) and on the pH of the impregnating bath. Finally, it was observed that cyclodextrins were more appropriate than starch as finishing coreactants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3730–3738, 2007     

绿色环保增塑剂柠檬酸三正丁酯的催化合成

在固体催化剂氨基磺酸的催化作用下研究了柠檬酸三正丁酯(TBC)的酯化反应,讨论了原料配比、催化剂用量、反应时间和反应温度等因素对酯化反应的影响,并用GC/MS对酯化后反应产物进行了检测分析。结果表明,氨基磺酸对酯化反应具有良好的催化活性,用它作催化剂合成TBC的最佳条件为:酸与醇的摩尔比为1∶3.8,催化剂用量2.75%,反应时间1.5 h,反应温度116~160℃,酯化率高达98%。     

The structure of crosslinked poly(glyceryl methacrylate) hydrogel networks

Poly(glyceryl methacrylate) hydrogels with different degrees of hydration (75–98% H) and cross-linking densities (X = 0.005–0.05 mol tetraethylene glycol dimethacrylate/mol glyceryl methacrylate) have been prepared by solution polymerization. Cross-linking densities of the fully swollen hydrogels were analyzed using a modified Flory equation. Poly(glyceryl methacrylate) gels polymerized with no added cross-linker were found to be highly cross-linked, the degree of cross-linking depending upon monomer dilution at polymerization. Modeling studies indicated that entanglement of polymer chains explained the highly cross-linked nature of these materials. Gels polymerized with tetraethylene glycol dimethacrylate exhibited higher cross-link densities than did gels polymerized with no added cross-linker. However, for gels polymerized with cross-linker, but at different initial dilutions, cross-linking densities varied depending upon initial concentration, indicating that entanglement contributed appreciably to cross-linking. These hydrogels may be regarded as highly swollen entangled networks, contrary to previous views. Correlation of these findings with those from earlier studies on the ultrafiltration behavior of the poly(glyceryl methacrylate) hydrogels suggested that the packing density of polymer fibers in the matrix may be more predictive of ultrafiltration behavior than is mesh size. © 1993 John Wiley & Sons, Inc.