Study on superabsorbent composites. XVIII. Preparation,characterization, and property evaluation of poly(acrylic acid‐co‐acrylamide)/organomontmorillonite/sodium humate superabsorbent composites

A series of novel multifunctional poly (acrylic acid‐co‐acrylamide) (PAA‐AM)/organomontmorillonite (O‐MMT)/sodium humate (SH) superabsorbent composites were synthesized by the graft copolymerization reaction of partially neutralized acrylic acid and acrylamide on O‐MMT micropowder and SH with N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in an aqueous solution. The superabsorbent composites were characterized by means of Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The effect of the relative weight ratio of SH to O‐MMT on the water absorbency was studied, and the results indicated that the best water absorbency of 591 g/g in distilled water was obtained when an O‐MMT content of 20 wt % and an SH content of 30 wt % were incorporated. The superabsorbent composite possessed a good capacity for water retention; even after 30 days, 24.4 wt % of water could still be saved by the sand soil containing 1.0 wt % superabsorbent composite. The results from this study show that the water absorbency of a superabsorbent composite is improved by the simultaneous introduction of O‐MMT and SH into a PAA‐AM network in comparison with the incorporation of only O‐MMT or SH. Also, in comparison with PAA‐AM/MMT/SH, an appropriate amount of O‐MMT can benefit the developed composites with respect to their water absorbency, salt resistance, and capacity for water retention in sand soil. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and swelling behavior of macroporous poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels

Macroporous superabsorbent hydrogels (SAHs) composed of acrylamide (AAm) and sodium methacrylate (NMA) were prepared by aqueous solution polymerization in the presence of a glucose solution. Their swelling capacity was investigated as a function of the concentrations of the glucose solution, sodium methacrylate, crosslinker, initiator, and activator. The porosity of the poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels was confirmed using scanning electron microscopy. The SAHs were characterized by IR spectroscopy. To estimate the effect on the swelling behavior, three types of crosslinkers were employed: N,N′‐methylenebisacrylamide, 1,4‐butanediol diacrylate, and diallyl phthalate. Network structural parameters such as initial swelling rate, swelling rate constant, and maximum equilibrium swelling were evaluated by water absorption measurement. The equilibrium water content (EWC%) of the AAm–NMA macroporous SAHs was found to be in the range of 93.31–99.68, indicating that these SAHs may have applications as biomaterials in the medicinal, pharmaceutical, and veterinary fields. Most of the SAHs prepared in this investigation followed non‐Fickian‐type diffusion, and few followed a case II– or super–case II‐type diffusion. The diffusion coefficients of these macroporous SAHs were investigated. Further, the swelling behavior of these SAHs also was investigated at different pHs and in different salt solutions and simulated biological fluids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3202–3214, 2006     

Influence of potassium humate on the swelling properties of a poly(acrylic acid‐co‐acrylamide)/ potassium humate superabsorbent composite

A novel superabsorbent composite, poly(acrylic acid‐co‐acrylamide)/potassium humate (PAA‐AM/KHA), was prepared by aqueous solution polymerization from acrylic acid, acrylamide, and potassium humate (KHA) with N,N′‐methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator. The effects of incorporated KHA on the water absorbency, swelling rate, and reswelling capability were investigated. The swelling property of PAA‐AM/KHA in various saline solutions was studied systematically. The results show that the comprehensive properties and especially salt‐resistant ability of PAA‐AM/KHA were enhanced. There was a linear relationship between the saturated water absorbency and the minus square root of the ionic strength of the external medium, and the water absorbency of PAA‐AM/KHA in various salt solutions had the following order: NH₄Cl_(aq) = KCl_(aq) = NaCl_(aq) > MgCl_2(aq) > CaCl_2(aq) > AlCl_3(aq) > FeCl_3(aq). Moreover, the polymeric net structure of PAA‐AM/KHA was examined with respect to that of poly(acrylic acid‐co‐acrylamide). The results indicate that the polymeric net of PAA‐AM/KHA was improved by the introduction of a moderate amount of KHA into the superabsorbent composite and made more suitable for agriculture and horticulture applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Overshooting effect of poly(dimethylaminoethyl methacrylate) hydrogels

An overshooting effect was observed during the swelling procedure of poly(dimethylaminoethyl methacrylate) (PDMAEMA) gel for the first time. The effects of the temperature, ionic strength, and pH on the overshooting effect of the PDMAEMA gel were investigated. We found that the overshooting effect of the gel could not be eliminated by changing the temperature; however, the overshooting effect was indiscernible in high‐concentration NaCl solutions (>0.2 mol/L) and basic (pH 11.9) and acidic solutions (pH = 2.1). The overshooting effect of the PDMAEMA gel was attributed to the dynamic conformational changes of the side chains of dimethylaminoethyl methacrylate (DMAEMA) units during the swelling of the gels. In the presence of NaCl or NaOH, the stretching of the macromolecular chains of the gels was disrupted. While in acidic solution, the protonation of tertiary amino groups in the DMAEMA units made the side chains of the DMAEMA units change from the cyclic conformation to the stretched one; this was analyzed with the aid of Fourier transform infrared spectroscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Determination of swelling behavior and morphological properties of poly(acrylamide‐co‐itaconic acid) and poly(acrylic acid‐co‐itaconic acid) copolymeric hydrogels

Poly(acrylamide‐co‐itaconic acid) (PAAmIA) and poly(acrylic acid‐co‐itaconic acid) (PAAIA) copolymeric hydrogels were prepared with different compositions via free‐radical polymerization. Ethylene glycol dimethacrylate (EGDMA) was used as an original crosslinker for these monomers. Gelation percentages of the monomers were studied in detail and it was found that addition of IA into the monomer mixture decreased the gelation percentage. The variation in swelling values (%) with time, temperature, and pH was determined for all hydrogels. PAA, which is the most swollen hydrogel, has the swelling percentage value of 2000% at pH = 7.4, 37°C. Swelling behaviors were explained with detailed SEM micrographs, which show the morphologic differences between dry and swollen hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5994–5999, 2006     

Synthesis and characteristics of an amphoteric semi‐IPN hydrogel composed of acrylic acid and poly(diallydimethylammonium chloride)

Semi‐interpenetrating polymer network (IPN) hydrogels, with acrylic acid (AA) and poly(diallydimethylammonium chloride) (PDMDAAC), were constructed by a sequential IPN method. The characterizations of the IPN hydrogels were investigated by FTIR, DTA, and swelling tests under various conditions. The prepared semi‐IPN hydrogels exhibited relatively high swelling capacity, in the range of 477–630 g/g at 25°C. The results show that the swelling capacity of AA/PDMDAAC semi‐IPN hydrogels was pH and temperature dependent. Swelling behaviors were also studied in the different salt solutions. Swelling kinetic parameters are given. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 345–350, 2007     

Effect of hydrotalcite on the physical properties and drug‐release behavior of nanocomposite hydrogels based on poly[acrylic acid‐co‐poly(ethylene glycol) methyl ether acrylate] gels

A series of nanocomposite hydrogels used for bioadhesive were prepared from acrylic acid, poly(ethylene glycol) methyl ether acrylate, and intercalated hydrotalcite (HT) by photopolymerization. The microstructures of the intercalated HT and sample gels were identified by X‐ray diffraction (XRD). The results showed that the swelling ratio for these nanocomposite hydrogels increased with an increase in HT, but the gel strength and adhesive force for these gels decreased with an increase in HT. The XRD results indicated that the exfoliation of intercalated HT was achieved in the xerogels and swollen gels. Finally, the drug‐release behaviors for these gels were also examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 692–699, 2004     

Amine‐derivatized poly(diallyldimethylammonium chloride) from N‐vinylformamide copolymerization

The reactivity ratios for the aqueous free‐radical copolymerization of diallyldimethylammonium chloride and N‐vinylformamide were found to be 0.13 and 1.92, respectively, from a Fineman–Ross analysis of a series of batch polymerizations. Because batch polymerization could not give a uniform product in a high yield with two monomers of such different reactivities, a semibatch procedure was developed in which the more reactive N‐vinylformamide was added in 10 steps over the course of the copolymerization. The poly(diallyldimethyl‐ ammonium chloride‐co‐N‐vinylformamide) copolymers were hydrolyzed to give poly(diallyldimethylammonium chloride‐co‐vinylamine). The utility of the vinylamine/diallyldimethylammonium chloride copolymers was demonstrated by the preparation and characterization of three derivatives: (1) a copolymer with coupled dansyl groups for fluorescence detection; (2) a copolymer with coupled dabsyl groups for ultraviolet–visible detection; and (3) an ultra‐high‐molecular‐weight (1.6 × 10⁶ Da) poly(diallyldimethylammonium chloride) by chain extension (coupling) with glycerol diglycidyl ether. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1068–1075, 2007     

Kinetic analysis of the imidization of poly(styrene‐co‐maleic anhydride) with aniline in the melt

On the basis of the competitive reactions of intermediate poly(styrene‐co‐N‐phenyl maleamic acid) (SNPMA) to produce either poly(styrene‐co‐maleic anhydride) (SMA) or poly(styrene‐co‐N‐phenyl maleimide) (SNPMI), the imidization kinetics of SMA with aniline in the molten state were investigated by a novel approach. The volatiles emitted during the reaction of SNPMA were monitored online with both thermogravimetric analysis and Fourier transform infrared (FTIR) integrated technology. The experimental results directly and definitely indicate that the amidization reaction from SMA to SNPMA in the melt was reversible. Moreover, the kinetic parameters of the competitive reactions of SNPMA in the melt to produce either SMA or SNPMI were determined by FTIR analysis and then compared with those parameters in solution that were obtained in our previous study. It was also implied that the forward ring‐opening reaction of SMA in the melt was nearly instantaneous and that the rates of the competitive reactions of SNPMA to produce either SMA or SNPMI were crucial for the total imidization of SMA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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

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

Effect of porosigen on the swelling behavior and drug release of porous N‐isopropylacrylamide/poly(ethylene glycol) monomethylether acrylate copolymeric hydrogels

A series of porous thermoreversible hydrogels were prepared from N‐isopropylacrylamide (90 mol %) and poly(ethylene glycol) methylether acrylate (10 mol %), which was derived from poly(ethylene glycol) monomethylether, N,N′‐methylenebisacrylamide, and porosigen, or poly (ethylene glycol) (PEG) with different molecular weights (MWs). The influence of pore volume in the gel on the physical properties, swelling kinetics, and solute permeation from these porous gels was investigated. The results show that the surface areas, pore volumes, and equilibrium swelling ratios for the porous gels increased with increasing MW of PEG, but the shear moduli and effective crosslinking densities decreased with increasing MW of PEG. The results from the dynamic swelling kinetics show that the transport mechanism was non‐Fickian. The diffusion coefficients of water penetrating into the gels increased with increasing pore volume of the gels. In addition, we also studied solute permeation through the porous gel controlled by temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5490–5499, 2006     

Synthesis,swelling behaviors,and slow‐release characteristics of a guar gum‐g‐poly(sodium acrylate)/sodium humate superabsorbent

Superabsorbents used in agricultural and ecological projects with low‐cost, slow‐release fertilizers and environmentally friendly characteristics have been extensively studied. The use of a natural polymer as the matrix and then further polymerization with some functional material has become the preferred method. In this work, with natural guar gum (GG), partially neutralized acrylic acid, and sodium humate (SH) as the raw materials, ammonium persulfate as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker, GG‐g‐poly(sodium acrylate) (PNaA)/SH superabsorbents were synthesized through a solution polymerization reaction and were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The effects of the SH content and MBA concentration on the water absorbency were investigated. The results showed that the introduction of SH into the GG‐g‐PNaA system could improve the water absorbency, swelling rate, pH‐resistant property, and reswelling capability, and the superabsorbent containing 15 wt % SH had the highest water absorbency of 532 g/g of sample in distilled water and 62 g/g of sample in a 0.9 wt % NaCl solution. The slow release in water and water retention in sandy soil tests revealed that the superabsorbent could act as a fertilizer as well as an effective water‐saving material for agricultural applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Adsorption of cationic dyes on poly(acrylic acid‐co‐sodium acrylate‐co‐acrylamide) superabsorbents

Inverse suspension polymerization was carried out to synthesize poly(acrylic acid‐co‐sodium acrylate‐co‐acrylamide) superabsorbent polymers (SAPs) crosslinked with ethylene glycol dimethacrylate (EGDMA). The equilibrium swelling capacities of the SAPs, determined by swelling them in DI water, were found to vary with the acrylamide (AM) content. The SAPs were used to adsorb four cationic dyes (Acriflavine, Auramine‐O, Azure‐I and Pyronin‐Y). The effect of AM content in the SAPs on the adsorption of the cationic dyes was investigated. Different initial concentrations of Azure‐I were used with the same amount of the SAP to explore the effect of initial dye concentration on the adsorption. The effect of the adsorbent amount was investigated by taking different amounts of SAP with a fixed initial concentration of Acriflavine. The kinetics of the dye adsorption was modeled by a first order model and the equilibrium amount of the dye adsorbed, adsorption rate coefficients, removal efficiency and partition coefficients were determined. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Novel mucoadhesive polymer: Synthesis and mucoadhesion of poly[acrylic acid‐co‐poly(ethylene glycol) monomethylether monomethacrylate‐co‐dimethylaminoethyl methacrylate]

This study was to design a mucoadhesive based on the biological and physicochemical properties of the buccal mucosa to achieve optimal mucoadhesion in the aqueous buccal environment. Since the buccal surface is negatively charged, a series of novel mucoadhesive poly[acrylic acid‐co‐poly(ethylene glycol) monomethylether monomethacrylate‐co‐dimethylaminoethyl methacrylate] [poly (AA‐PEGMM‐DMEMA)] were synthesized by incorporating the cationic monomer DMEMA into poly(AA‐PEGMM) to enhance the interactions between the mucohadhesive polymer and the buccal mucosa. The compositions of poly(AA‐PEGMM‐DMEMA) were varied by changing the content of DMEMA from 0 to 4.8 mol % while keeping the mole ratio of AA to PEGMM at a constant 9 : 1. It was found that the force of mucoadhesion of poly(AA‐PEGMM‐DMEMA) increased initially, as DMEMA content increased, and reached the maximum at 1% of DMEMA. Further increasing the content of DMEMA decreased the mucoadhesion. The polymers with 0.5 to 2.9% DMEMA appeared to have maximum mucoadhesion after prehydration for 5 min. An ATR–FTIR spectroscopy study revealed that intrapolymer interactions and intersurface interactions played opposite roles in the mucoadhesion performance of the polymers. Optimal mucoadhesion can be achieved by balancing these two interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:2431–2437, 2004     

Cephazoline sodium release from poly(N‐isopropyl acrylamide‐co‐N,N‐dimethylacrylamide) hydrogels

Hydrogels are hydrophilic polymers that swell to an equilibrium volume in the presence of water, preserving their shape. The dynamic swelling behavior of poly(N‐isopropylacrylamide‐co‐N,N‐dimethylacrylamide) [poly(NIPA‐co‐DMA)] copolymers at 37°C was investigated. It was observed that the swelling degree in the copolymers decreases with the N‐isopropylacrylamide content. In addition, the liberation mechanism was found to be Fickian. Diffusion coefficients according to Fick′s law as a function of the N‐isopropylacrylamide concentration and results of the release process are reported. The kinetics of cephazoline sodium release from poly(NIPA‐co‐DMA) hydrogels with different compositions was studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3433–3437, 2004     

Hydrolyzed collagen‐grafted‐poly[(acrylic acid)‐co‐(methacrylic acid)] hydrogel for drug delivery

Hydrolyzed collagen‐grafted‐poly[(acrylic acid)‐co‐(methacrylic acid)] hydrogels were synthesized by solution polymerization and confirmed by infrared spectroscopy. From sequential univariate analysis, the optimal molar ratio of acrylic acid: methacrylic acid was 92:8 in the presence of N,N′‐methylenebisacrylamide, ammonium persulfate, and N,N,N′,N′‐tetramethylethylenediamine at 0.12, 0.015, and 0.2% mol of the monomers, respectively. The water absorbency of this hydrogel was both pH‐ and temperature‐dependent, but was higher in nonbuffered water than in boric acid/citric acid/phosphate buffer under the same conditions. The optimal hydrogel could swiftly swell and deswell in neutral and acid solutions, respectively. Its potential application in drug delivery was examined using insulin and methylene blue as model payload drugs. Loading in a 50% (v v^?1) ethanol solution gave a higher insulin loading level than in the buffer water. Insulin and methylene blue were both released at pH 6.8 but not at pH 1.2, but followed first order kinetics and the Higuchi equation, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45654.     

Swelling behavior of thermoreversible poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels

Thermoresponsive hydrogels based on N‐isopropylacrylamide and N‐vinylimidazole were synthesized, and their swelling–deswelling behavior was studied as a function of the total monomer concentration. For copolymeric structures with better thermoresponsive properties with respect to poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels, these hydrogels were protonated with HCl and HNO₃, and the copolymer behaviors were compared with those of the unprotonated hydrogels. The temperature was changed from 4 to 70°C at fixed pHs and total ionic strengths. The equilibrium swelling ratio, dynamic swelling ratio, and dynamic deswelling ratio were evaluated for all the hydrogels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1619–1624, 2004     

Swelling characterization of the semiinterpenetrating polymer network hydrogels composed of chitosan and poly(diallyldimethylammonium chloride)

Temperature‐ and pH‐responsive semiinterpenetrating polymer network (SIPN) hydrogels, constructed with chitosan (CS) and poly(diallyldimethylammonium chloride) (PDADMAC), were studied. The characterizations of the IPN hydrogels were investigated by fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and swelling tests, under various conditions. CS/PDADMAC SIPN hydrogels exhibited a relatively high swelling ratio, in the range of 248–462%, at 25°C. The swelling ratio of CS/PDADMAC IPN hydrogels are pH, temperature, and ionic concentration dependent. DSC was used for the quantitative determination of the amounts of freezing and nonfreezing water. The amount of free water increased with increasing PDADMAC content in the IPN hydrogels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2876–2880, 2004     

Swelling and drug‐release behavior of the poly(AA‐co‐N‐vinyl pyrrolidone)/chitosan interpenetrating polymer network hydrogels

A series of novel hydrogels were prepared from acrylic acid (AA), N‐vinyl pyrrolidone (NVP), and chitosan by photopolymerization. The swelling behavior, gel strength, and drug release behavior of the poly(AA/NVP) copolymeric hydrogels and corresponding interpenetrating polymer network hydrogels were investigated. Results showed that the swelling ratios for the present hydrogels decreased with an increase of NVP content in the gel, but the gel strength increased with an increase of NVP content in the gel. Results also showed that the drug‐release behavior for the gels is related to the ionicity of drug and the swelling ratio of the gel. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2135–2142, 2004