Synthesis,characterization, and swelling behavior of alginate‐g‐poly(sodium acrylate)/kaolin superabsorbent hydrogel composites

A novel superabsorbent composite based on sodium alginate and the inorganic clay kaolin was synthesized via the graft copolymerization of acrylic acid (AA) in an aqueous medium with methylene bisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The effects of reaction variables, such as the MBA, AA, and APS concentrations and the alginate/kaolin weight ratio, on the water absorbency of the composite were systematically optimized. Evidence of grafting and kaolin interactions was obtained by a comparison of the Fourier transform infrared spectra of the initial substrates with that of the superabsorbent composite, and the hydrogel structure was confirmed with scanning electron microscopy. The results indicated that with an increasing alginate/kaolin weight ratio, the swelling capacity and gel content increased. The effects of various salt media were also studied, along with the swelling kinetics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Crosslinked poly(sodium acrylate) hydrogels

Summary Samples of poly(acry1ic acid) (PAA) neutralized to varying degrees with sodium hydroxide were subjected to -irradiation to yield insoluble crosslinked polyacrylate hydrogels. The efficiency of crosslinking was found to be dependent on the degree of neutralization of the sample and the concentration of the irradiated polymer solution. The extent of water uptake of the gel was shown to be related to the degree of neutralization by titration of acid groups within the gel subsequent to cross-linking. Lightly crosslinked gels exhibited a maximum degree of swelling at a particular neutralization level. This was ascribed to a maximum in the long-range forces exerted cooperatively by the polymeric charges. The presence of simple electrolyte ions reduces swelling by screening these forces.     

Synthesis,characterization, and in vitro biocompatibility study of novel disulfide cross‐linked hydrogels based on poly(amic acid)

In this study, novel disulfide cross‐linked hydrogels were designed and synthesized. First, ethylenediaminetetraacetic dianhydride reacted with butanediamine and amino‐terminated polyethylene glycol via N‐acylation reaction to give biocompatible poly(amic acid) (PAA) with pendant carboxyl groups; then, the amino groups of cystamine reacted with carboxyl groups of PAA to generate disulfide cross‐linked network polymer (PAA‐SS). Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance imaging, gel permeation chromatography with multiangle laser light scattering, potentiometric titration, rheology, hydrolytic degradation, morphology, porosity, and in vitro biocompatibility studies were used to qualitatively and quantitatively characterize the obtained polymers. The results indicated that the equilibrium swelling ratio of the PAA‐SS decreased with the increase in Rm. The PAA‐SS provided good mechanical strength to maintain their integrity, and the storage modules (G′) of the hydrogels can be adjusted by Rm. The PAA‐SS presented co‐continuum pores, and the pore size correlated with the cross‐linking degree. The degradation of PAA‐SS could be controlled by regulating the concentration of dithiothreitol. Particularly, the PAA‐SS possessed an excellent biocompatibility, as the average proliferating rate of osteoblasts on PAA‐SS was appreciably higher than that on PAA and glass coverslips. In conclusion, the above obtained results demonstrate that the performance of the PAA‐SS outbalance and facilitate the application in biomedical region, particularly in bone tissue regeneration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40930.     

Synthesis and characterization of poly(butyl acrylate)/silica and poly(butyl acrylate)/silica/poly(methyl methacrylate) composite particles

Poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) core–shell particles embedded with nanometer‐sized silica particles were prepared by emulsion polymerization of butyl acrylate (BA) in the presence of silica particles preabsorbed with 2,2′‐azobis(2‐amidinopropane)dihydrochloride (AIBA) initiator and subsequent MMA emulsion polymerization in the presence of PBA/silica composite particles. The morphologies of the resulting PBA/silica and PBA/silica/PMMA composite particles were characterized, which showed that AIBA could be absorbed effectively onto silica particles when the pH of the dispersion medium was greater than the isoelectric potential point of silica. The critical amount of AIBA added to have stable dispersion of silica particles increased as the pH of the dispersion medium increased. PBA/silica composite particles prepared by in situ emulsion polymerization using silica preabsorbed with AIBA showed higher silica absorption efficiency than did the PBA/silica composite particles prepared by direct mixing of PBA latex and silica dispersion or by emulsion polymerization in which AIBA was added after the mixing of BA and silica. The PBA/silica composite particles exhibited a raspberrylike morphology, with silica particles “adhered” to the surfaces of the PBA particles, whereas the PBA/silica/PMMA composite latex particles exhibited a sandwich morphology, with silica particles mainly at the interface between the PBA core and the PMMA shell. Subsequently, the PBA/silica/PMMA composite latex obtained had a narrow particle size distribution and good dispersion stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3425–3432, 2006     

Synthesis and characterization of poly(fluorinated acrylate)/silica hybrid nanocomposites

The nanocomposite particles (NPs) with inorganic silica as core and fluorinated polymer shell have been in situ synthesized via emulsion polymerization. The chemical composition and core‐shell structure were characterized by Fourier‐transform infrared spectrometry and transmission electron microscopy. The results showed that silica nanoparticles were encapsulated in latex particles, with single‐ and multicore morphologies coexisting. Thermal gravimetric analysis also suggested the successful encapsulation of silica into NPs with enhanced thermal stability. The surface properties of the latex films produced from the core‐shell particles were also investigated by contact angle method and water absorption measurement. Both fluorinated polymer and silica contributed to less water absorption ratio and lower surface‐free energy, which was composed of larger polar component and smaller disperse component, just reversed as usual. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Synthesis and characterization of poly(styrene‐co‐butyl acrylate)/clay nanocomposite latexes in miniemulsion by AGET ATRP

Polymer/clay nanocomposite latexes in the form of positively charged nanoparticles were synthesized by a newly developed initiating system, activators generated by electron transfer (AGET), which has been employed in atom transfer radical polymerization (ATRP). These clay‐dispersed latexes were synthesized using AGET ATRP of styrene and butyl acrylate in a miniemulsion system in which, ascorbic acid as a reducing agent was added drop wise to reduce termination reactions. Particle size and particle size distribution of resulted nanocomposite latexes were characterized by dynamic light scattering (DLS). These latexes were in the range of 138 to 171 nm in size. Gel permeation chromatography (GPC) was used to characterize the molecular weight and molecular weight distribution of the resultant copolymer nanocomposites. GPC traces showed that polymers of narrow molecular weight distribution and low Polydispersity Index (PDI) have been synthesized; this clearly shows ATRP reaction is conducted successfully. By increasing nanoclay content, molecular weight of the nanocomposites decreases. The presence of the nanofiller increases the thermal stability of the nanocomposites as investigated by thermogravimetric Analysis (TGA). Glass transition temperature of nanocomposites increases compared with the neat copolymer which was studied by differential scanning calorimetry (DSC). scanning electron microscope (SEM) showed sphere morphology of polymer particles synthesized by miniemulsion polymerization. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that mixed intercalated and exfoliated morphology is obtained. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Synthesis and swelling characteristics of a pH‐responsive guar gum‐g‐poly(sodium acrylate)/medicinal stone superabsorbent composite

A series of pH‐responsive superabsorbent composites were synthesized by the free‐radical grafting copolymerization of natural guar gum (GG), partially neutralized acrylic acid (NaA), and medicinal stone (MS) using ammonium persulfate (APS) as the initiator and N,N′‐methylene‐bis‐acrylamide (MBA) as the crosslinker. The structure, surface morphologies, and thermal stability of the developed composites were characterized by FTIR spectra, SEM, and TGA techniques, respectively. The effects of various saline, surfactant, and dye solutions on swelling properties were investigated, and the pH‐responsivity was also evaluated. Results indicated that NaA had been grafted onto GG macromolecular chains and MS participated in the polymerization reaction. The incorporation of MS obviously improved the surface structure, thermal stability, water absorption capacity, and rate. Multivalent saline, cationic surfactant, and dye showed more remarkable effect on the water absorption than did monovalent or anionic ones. The composites showed excellent responsive properties and reversible On–Off switching characteristics in various pH buffer solutions, which provided great possibility to extend the application domain of the superabsorbent composites. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Synthesis and swelling behaviour of poly (sodium acrylate)/sepiolite superabsorbent composites and nanocomposites

A series of novel composites and nanocomposites xerogels based on acrylic acid, sepiolite and N,N′‐methylenebisacrylamide were prepared using a solution polymerization technique at 70 °C. The quality of dispersion of the micronized sepiolite in the monomer is the crucial point for obtaining nanocomposites. A good dispersion explains the improvement of the absorbent properties of the nanocomposites with respect to the composites. This work investigates not only the influence of the mixing procedure on the swelling behaviour, but also the effect of the amount of clay on the absorbency of these hydrogels in deionized water and saline solution (0.2 wt% NaCl_(aq)). A crosslinker concentration of 5 wt% sepiolite nanocomposite superabsorbent was shown to give the best results (1419 g g^?1). Moreover, experimental results indicate that the absorbency in saline solution is smaller than that in deionized water. Rates of swelling for these absorbents were found to fit the Voigt expression. Finally, the model approximates Case II sorption in the early stages of the swelling process and Case I in the later stages. Copyright © 2006 Society of Chemical Industry     

Preparation and morphology of high‐performance exfoliated poly(sodium acrylate)/hydrotalcite nanocomposite superabsorbents

A poly‐matrix composite—poly(sodium acrylate) (PSA)/hydrotalcite (HT) (PSA/HT) nanocomposite superabsorbent—with obvious improvements in both the water absorbency and salt absorbency has been prepared by the intercalated HT, using sodium methyl allyl sulfonate as an intercalation agent. The superabsorbents acquired their highest water (salt) absorbency when the content of HT is 3 wt%. The highest absorbency for deionized water and 0.9 wt% NaCl _(aq) were 1100 g/g and 145 g/g, respectively. Microstructures were analyzed by X‐ray diffraction and scanning electron microscope. Chemical analysis was determined measurements. Results showed that HT incorporated into the superabsorbents was by Fourier infrared spectroscopy and energy dispersion spectroscopy. Results showed that the superabsorbent particles were in the form of spheres, and the hydrogels were in the form of regular network structures. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Heterogeneities during the formation of poly(sodium acrylate) hydrogels

Summary In situ fluorescence and light scattering techniques were used to study the formation of heterogeneities during the free-radical crosslinking polymerization of sodium acrylate (NaAc) in the presence of N,N'-methylene(bisacrylamide) (BAAm) as a crosslinker. Pyranine was used as a fluorescence probe in the experiments. The reactions were carried out at room temperature and at a monomer concentration of 20.6 w/v% in water. It was found that the gel forming system became turbid at the start of the reaction; continuing polymerization and crosslinking reactions turned the opaque gels into slightly opaque and finally transparent gels. Two peaks were observed both in the scattered and emitted light intensities versus the reaction time plots. The first peak corresponds to the formation and growth of the phase separated domains whereas the second peak reflects the macrogelation point in the reaction system. Received: 14 June 1999/Revised version: 10 October 1999/Accepted: 10 October 1999     

Synthesis and thermal properties of poly(n‐butyl acrylate)/n‐hexadecane microcapsules using different cross‐linkers and their application to textile fabrics

This study focused on the preparation, characterization, and determination of thermal properties of microencapsulated n‐hexadecane with poly(butyl acrylate) (PBA) to be used in textiles with heat storage property. Microcapsules were synthesized by emulsion polymerization method, and the particle size, particle size distribution, shape, and thermal storage/release properties of the synthesized microcapsules were analyzed using Fourier‐transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry techniques. Allyl methacrylate, ethylene glycol dimethacrylate, and glycidyl methacrylate were used as cross‐linkers to produce unimodal particle size distribution. MicroPBA microcapsules produced using allyl methacrylate cross‐linker were applied to 100% cotton and 50/50% cotton/polyester blend fabrics by pad‐cure method. The mean particle size of microcapsules ranges from 0.47 to 4.25 μm. Differential scanning calorimetry analysis indicated that hexadecane in the microcapsules melts at nearly 17°C and crystallizes at around 15°C. The contents of n‐hexadecane of different PBA microcapsules were in the range of 27.7–50.7%, and the melting enthalpies for these ratios were between 65.67 and 120.16 J/g, respectively. The particle size and thermal properties of microcapsules changed depending on the cross‐linker type. The cotton and 50/50% cotton/polyester blend fabrics stored 6.56 and 28.59 J/g thermal energy, respectively. The results indicated that PBA microcapsules have the potential to be used as a solid‐state thermal energy storage material in fabrics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Swelling behavior of poly(sodium acrylate)/kaoline superabsorbent composite

Using partly neutralized acrylic acid as monomer, kaoline ultrafine powder as filler and N,N′‐(dimethyl)acrylamide as crosslink agent, poly(sodium acrylate)/kaoline superabsorbent composite was synthesized by aqueous solution polymerization method. Using the superabsorbent composite as collagen, a hydrogel was prepared. The influence of the neutralization degree of superabsorbent collagen, the compositions, the concentration, and the pH value of exterior solution on the swelling behavior of the hydrogel was investigated. It was found that the swelling capability of the hydrogel depended on the groups on the collagen. The swelling capability of the hydrogel relied on the ionic intensity, molecular polarity, molecular volume, as well as the concentration of exterior solution. When the pH value of exterior solution was equal to seven, the hydrogel has a maximum swelling value of 800 times. POLYM. ENG. SCI. 46:324–328, 2006. © 2006 Society of Plastics Engineers     

Synthesis and characterization of poly(n‐undecyl isocyanate)/polyaniline polyblend

Poly(n‐undecyl isocyanate) (PUDIC)/n‐dodecylbenzenesulfonic acid (DBSA)‐doped polyaniline (PANIDBSA) polyblend was prepared and the effect of the H‐bonding between these two polymers on the compatibility, conjugation chain length of PANIDBSA, and helixity of PUDIC in the polyblend system were studied. The monomer and polymer were characterized by NMR spectra and the polyblend was analyzed by FTIR, UV–vis spectra, and wide‐angle X‐ray diffraction. It was found when the blend composition of the PUDIC was higher than 10%, the WAXD patterns demonstrated lower angle shifting for the peaks at around 2θ = 2–2.5°, referring to the distance between the layers of the layered structure of PANIDBSA crystalline with increasing PUDIC, indicating the expansion of the layered structure of PANIDBSA. The FTIR spectra illustrated the presence of an absorption peak at 1700 cm^?1 shift to higher wave number with PUDIC due to its H‐bonding with PANIDBSA. The UV–vis spectra of PANIDBSA described a blue‐shift of the λ_max with PUDIC, indicating that the presence of PUDIC in the polyblend system can interrupt and decrease the conjugation chain length of PANIDBSA. The optical activity of the helical PUDIC decreased notably with the presence of PANIDBSA, resulting from the reversed helical effect (de‐nature) of H‐bonding. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of poly(sodium acrylate‐co‐sodium 1‐(acryloyloxy) propan‐2‐yl phosphate) and comparative study on its swelling properties with poly(sodium acrylate) and poly(sodium acrylate‐co‐2‐hydroxypropyl acrylate)

A new superabsorbent copolymer, poly(sodium acrylate‐co‐sodium 1‐(acryloyloxy) propan‐2‐yl phosphate) [P(SA‐co‐SAPP)], was synthesized by a novel prepared monomer, 1‐(acryloyloxy) propan‐2‐yl phosphoryl dichloride. The swelling properties of the superabsorbent were investigated by comparison with poly(sodium acrylate) (PSA) and the copolymer of poly(sodium acrylate‐co‐2‐hydroxypropyl acrylate) [P(SA‐co‐HPA)]. The results showed that (1) the superabsorbent containing sodium 1‐(acryloyloxy) propan‐2‐yl phosphate had higher water absorbency at general testing conditions; (2) the swelling properties of P(SA‐co‐SAPP) and PSA were obviously influenced by pH of solutions, which were different from that of P(SA‐co‐HPA); (3) the swelling process and the saturated water absorbency of all superabsorbents were remarkably affected by cations, especially multivalent ones, while barely affected by anions. POLYM. ENG. SCI., 47:728–737, 2007. © 2007 Society of Plastics Engineers.     

Synthesis and characterization of poly(glycidyl methacrylate)/Na‐montmorillonite nanocomposites

Poly(glycidyl methacrylate)/Na–montmorillonite nanocomposites were synthesized by free‐radical polymerization of glycidyl methacrylate containing dispersed montmorillonite. By changing the concentration of glycidyl methacrylate several polymer–clay nanocomposites were prepared and the resulting nanocomposites were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results indicated that the properties of the composite were significantly improved. The thermogravimetric analysis results revealed that the degradation temperatures of nanocomposites were higher than that of pure polymer and the thermal degradation rates decreased. Examination of these materials by scanning electron microscopy showed that the clay layers are dispersed homogenously in the polymer matrix and the formation of intercalation nanostructure. Furthermore, adsorptive, moisture regain, and water uptake properties of nanocomposites were also investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1532–1538, 2004     

Synthesis and characterization of poly(urethane‐benzoxazine)/clay hybrid nanocomposites

Poly(urethane‐benzoxazine)/clay hybrid nanocomposites (PU/Pa–OMMTs) were prepared from an in situ copolymerization of a polyurethane (PU) prepolymer and a monofunctional benzoxazine monomer, 3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine (Pa), in the presence of an organophilic montmorillonite (OMMT), by solvent method using DMAc. OMMT was made from cation‐exchange of Na‐montmorillonite (MMT) with dodecyl ammonium chloride. The formation of the exfoliated nanocomposite structures of PU/Pa‐OMMT was confirmed by XRD from the disappearance of the peak due to the basal diffraction of the layer‐structured clay found in both MMT and OMMT. DSC showed that, in the presence of OMMT, the curing temperature of PU/Pa lowered by ca. 60°C for the onset and ca. 20°C for the maximum. After curing at 190°C for 1 h, the exothermic peak on DSC disappeared. All the obtained films of PU/Pa–OMMT were deep yellow and transparent. As the content of OMMT increased, both the tensile modulus and strength of PU/Pa–OMMT films increased, while the elongation decreased. The characteristics of the PU/Pa–OMMT films changed from plastics to elastomers depending on OMMT content and PU/Pa ratio. PU/Pa–OMMT films also exhibited excellent resistance to the solvents such as tetrahydrofuran, N,N‐dimethylformamide and N‐methyl‐2‐pyrrolidinone. The thermal stability of PU/Pa were enhanced remarkably even with small amount of OMMT. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4075–4083, 2003     

Synthesis and characterization of cross‐linkable poly(phthalazinone ether ketone)s

A novel class of crosslinkable poly(phthalazinone ether ketone)s with relative high molecular‐weight and good solubility were successfully synthesized by the copolymerization of bisphthalazinone containing monomer, 3,3′‐diallyl‐4,4′‐dihydroxybiphenyl and 4,4′‐di‐ fluorobenzophenone. The synthesized polymers with inherent viscosities in the range of 0.42 to 0.75 dL/g can form flexible and transparent membranes by casting from their solution. The crosslinking reaction of these polymers can be carried out by thermally curing of the virgin polymers in or without the presence of crosslinking agent. The experimental results demonstrated that the crosslinking reaction also occurred to some extent during the polymerization. The crosslinked polymers exhibited equivalent glass transition temperature (T_g) at lower crosslinking density, and showed higher T_g than virgin polymers at higher crosslinking density. The crosslinked high‐temperature polymer can be used as the base material for high temperature adhesive, coating, enamel material, and composite matrices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Development of a biodegradable rice straw‐g‐poly(methyl methacrylate)/sodium silicate composite flame retardant

Natural fiber composites have been prepared by grafting hydrophobic monomer methyl methacrylate (MMA) onto chemically modified rice straw (RS) using complex initiating system [CuSO₄/glycine/ammonium persulfate (APS)] in an aqueous medium with and without the additive, sodium silicate (SS). The chemically modified RS, RS‐g‐PMMA, and RS‐g‐PMMA/SS composite have been characterized by FT‐IR, and their morphology was studied by scanning electron microscopy (SEM). The thermal behavior and tensile properties of the samples have been studied, and the flame retardant properties have also been evaluated by limiting oxygen index (LOI) test and cone calorimetry. The biodegradation and water absorbency have been carried out for its ecofriendly nature and better commercialization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

pH‐ and temperature‐responsive IPN hydrogels based on soy protein and poly(N‐isopropylacrylamide‐co‐sodium acrylate)

pH‐ and temperature‐responsive interpenetrating polymer network (IPN) hydrogels based on soy protein and poly(N‐isopropylacrylamide‐co‐sodium acrylate) were successfully prepared. The structure and properties of the hydrogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analyzer. The equilibrium and dynamic swelling/deswelling behaviors and the drug release properties of the hydrogels responding to pH and/or temperature were also studied in detail. The hydrogels have the porous honeycomb structures, good miscibility and thermal stability, and good pH‐ and temperature‐responsivity. The volume phase transition temperature of the hydrogels is ca. 40°C. Changing the soy protein or crosslinker content could be used to control the swelling behavior and water retention, and the hydrogels have the fastest deswelling rate in pH 1.2 buffer solutions at 45°C. Bovine serum albumin release from the hydrogels has the good pH and temperature dependence. The results show that the proposed IPN hydrogels may have potential applications in the field of biomedical materials such as in drug delivery systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39781.