Synthesis,characterization and swelling behavior of chitosan‐sucrose as a novel full‐polysaccharide superabsorbent hydrogel

A novel full‐polysaccharide hydrogel was prepared by crosslinking of chitosan with periodate‐oxidized sucrose. A tetraaldehyde molecule is synthesized via periodate oxidation of sucrose and then applied as a crosslinking agent to form a new hydrogel network. A mechanism for the superabsorbent hydrogel formation via reductive N‐alkylation was also suggested. The structure of the hydrogel was confirmed by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). It is shown that crosslinking of chitosan can improve its thermal stability. The effects of crosslinker concentration, pH, and inorganic salt on the swelling behavior of the hydrogel were studied. The results indicate that the hydrogel has good pH sensitivity and pH reversible response. The smart hydrogels may have potential applications in the controlled delivery of bioactive agents and for wound‐dressing application © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and super-swelling behavior of a novel protein-based superabsorbent hydrogel

Summary In this work, we synthesize a novel protein-based superabsorbent hydrogel and study its swelling behavior. The crosslinking graft copolymerization of acrylic acid (AA) onto the hydrolyzed collagen as a protein backbone was carried out in a homogeneous medium. Potassium persulfate (KPS) as an initiator and N,N^′-methylene bisacrylamide (MBA) as a crosslinker were used. The product’s structure was established using FTIR spectroscopy. We were systematically optimized the certain variables of the graft copolymerization (i.e. the monomer, the initiator, and the crosslinker concentration) to achieve a hydrogel with maximum swelling capacity. Under this condition, maximum capacity of swelling in distilled water was found to be 920 g/g. Morphology of the optimized sample was examined by scanning electron microscopy (SEM). The swelling ratio in various salt solutions was also determined. Additionally, the swelling of superabsorbing hydrogels was measured in solutions with pH ranged from 1 to 13. The synthesized hydrogel exhibited a pH-responsiveness character so that a swelling-collapsing pulsatile behavior was recorded at pH 2 and 8.     

Synthesis of superabsorbent hydrogel nanocomposites for use as hemostatic agent

Uncontrolled hemorrhage continues to be the major cause of death in trauma. In this study, the authors prepared hydrogel nanocomposites (HNCs) using three different nanoparticles, SiO₂, natural clinoptilolite (nC), and Ca²⁺-modified clinoptilolite (mC). Fast-swelling superabsorbent hydrogel was used as a matrix of NCs. The hydrogel and HNCs were characterized by FTIR, XRD, FE-SEM, and TGA. The hemocompatibility of HNCs was evaluated by hemolysis test and blood cells function. HNC formed a physical barrier by dehydrating the injury site and concentrating clotting factors. Additionally, highly charged nanoparticles, promoted local hemostasis by activating the intrinsic pathway of the blood coagulation cascade.     

NVP接枝壳聚糖水凝胶的合成与溶胀性能

合成了N-乙烯基吡咯烷酮（NVP）接枝壳聚糖（CHI）水凝胶,讨论了NVP/CHI、引发剂、交联剂、聚合温度、乙酸浓度等因素对接枝率及凝胶溶胀性能的影响,NVP∶CHI为6时,接枝率达到300%以上. 溶胀温度、pH值、盐浓度等对凝胶溶胀性能的影响实验表明,凝胶表现出温度敏感性,在40 ℃出现最大平衡溶胀率,并观察到一级相转变;在中性或弱酸性介质中溶胀性能较好;与PVP凝胶相比,NVP接枝CHI凝胶表现出反聚电解质效应. 溶胀动力学研究表明,在溶胀前期,CHI含量较高时,凝胶趋向于非Fick溶胀,说明除了溶剂扩散外,凝胶网络链段弛豫、水分子与凝胶网络间及凝胶高分子链段间相互作用对凝胶溶胀性能的影响至关重要;CHI含量较高时则趋向于Fick溶胀.     

Grafted CMC/silica gel superabsorbent composite: Synthesis and investigation of swelling behavior in various media

In the present study, we attempt to synthesize and characterize novel CMC-g-poly (acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid)/silica gel composite. Infrared spectroscopy and TGA thermal analysis were carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was examined by scanning electron microscopy. The effect of reaction variables affecting on water absorbency of the composite and swelling behavior in various solvents, salt, and pH solutions was investigated. Maximum water absorbency of the optimized final product was found to be 4000 g/g in distilled water. The absorbency under load (AUL) of the hydrogel was also determined by using an AUL tester at various applied pressures. Finally, dynamic swelling kinetics of the hydrogel was studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Partially hydrolyzed kappa carrageenan—polyacrylonitrile as a novel biopolymer‐based superabsorbent hydrogel: Synthesis,characterization, and swelling behaviors

In this paper, synthesis and swelling behavior of a novel superabsorbent hydrogel based on kappa carrageenan (κC) and polyacrylonitrile (PAN) was investigated. To achieve partially hydrolyzed κC‐PAN hydrogel, physical mixture of κC and PAN was hydrolyzed by NaOH solution. During alkaline hydrolysis, the nitrile groups of PAN are converted to a mixture of hydrophilic carboxamide and carboxylate groups follow by in situ crosslinking of the grafted PAN chains. The reaction variables affecting on the swelling capacity of the hydrogel were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Under the optimized conditions concluded, super swelling hydrogel with the ability of water absorption up to 3260 g/g (water/dry hydrogel powder) has been prepared. Swelling measurements of the synthesized hydrogels was carried out in various salt solutions and solutions with different pH. The results indicate that the hydrogels have good pH sensitivity and pH‐reversible property between pH 2 and pH 8. POLYM. ENG. SCI. 46:1778–1786, 2006. © 2006 Society of Plastics Engineers.     

Theoretical and experimental investigation of the swelling behavior of sodium polyacrylate superabsorbent particles

Sodium polyacrylate superabsorbent polymers were prepared in particle forms by the inverse suspension technique. The surfactant concentration effect on the polymer particle size was analyzed with molecular sieves and an optical microscope. Water absorption and desorption characteristics were analyzed by the gravimetric method. The equilibrium water uptake in sodium polyacrylate particles was strongly dependent on both the salt concentration of the aqueous media and the crosslinking density of the polymers. The polymer crosslinking density was determined from the measurement of Young's modulus and the polymer–solvent interaction parameter from the equilibrium swelling experiment. The degree of inonization was predicted from experimental measurements, and theoretical analysis was performed on the effects of the salt concentration and polymer crosslinking density on the equilibrium water swelling ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 252–257, 2003     

Salep‐g‐poly(sodium acrylate)/alumina superabsorbent hydrogel composite as a smart material: Irradiation synthesis and investigation of its swelling behavior

A novel environmentally sensitive superabsorbent composite was synthesized via the gamma (γ)‐irradiation graft copolymerization of sodium acrylate onto a homogeneous blend of natural salep and alumina in an aqueous medium. The reaction parameters (i.e., acrylic acid amount, neutralization percentage, alumina/salep weight ratio, and γ‐irradiation total dose) affecting the water absorbency of the hydrogel composite were optimized by using a systematic method in order to achieve a composite with as high a swelling capacity as possible. FTIR spectroscopy was used to confirm the structure of the final product. Morphology of the synthesized composite was examined by scanning electron microscopy. The swelling behavior of the optimum superabsorbent composite was measured in various environments, and the results showed excellent on–off switching behaviors which made this novel smart composite material a nominee that can potentially be used in agriculture, pharmaceutics, and biosensors. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Synthesis,characterization, and swelling kinetic study of porous superabsorbent hydrogel nanocomposite based on sulfonated carboxymethylcellulose and silica nanoparticles

New superabsorbent nanocomposite was synthesized by free-radical graft polymerization of sulfonated-carboxymethyl cellulose (SCMC) with acrylic acid (AA) in the presence of polyvinylpyrrolidone (PVP) and silica nanoparticles. Carboxymethyl cellulose (CMC) was first sulfonated using chlorosulfonic acid, and then AA monomers were grafted onto SCMC. FTIR results confirmed that sulfonation of CMC as well as grafting of AA monomers onto SCMC has been performed successfully. Moreover, the presence of silica nanoparticles into superabsorbent nanocomposite was evaluated with EDX analysis. The element mappings show a homogenous distribution of silica nanoparticles throughout the hydrogel nanocomposite. SEM images exhibited porous morphology for hydrogel nanocomposite, which was due to the incorporation of PVP in its network. The experimental findings from TGA analysis indicated that incorporation of PVP and silica nanoparticles into the hydrogel network improved thermal stability of superabsorbent nanocomposite. Swelling kinetic studies revealed that superabsorbent nanocomposite hydrogel had higher equilibrium swelling capacity and swelling rate compared with the neat hydrogel sample. Besides that, superabsorbent nanocomposite depicted excellent salt and pH-sensitive behavior in different saline and pH solutions. As a consequence, this hydrogel nanocomposite acts as useful water reservoir, which might be most profitable in agricultural applications.     

微波辐照合成聚丙烯酸水凝胶及其性能研究

采用微波辐照法合成了聚丙烯酸水凝胶,并对其溶胀性能进行了研究。所制得的凝胶不仅具有pH敏感性和良好的pH反复性,而且在pH<4的酸性溶液中表现出温度敏感性,其溶胀比随温度的升高而上升。     

Synthesis and swelling property of the starch‐based macroporous superabsorbent

The starch‐based macroporous superabsorbent polymer (St‐MP SAP) was synthesized by graft copolymerization of acrylic acid (AA)/2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) onto cassava starch through free radical polymerization method by using sodium bicarbonate (SHC) as porogen. The monomer conversion kinetics was investigated to determine the suitable time of adding SHC so as to produce large numbers of stable and uniform pores inside the SAP. Introduction of SHC led to the formation of increasing pores and loose structure in St‐MP SAP, the decrease of shear storage modulus (G′). With increasing SHC content, the size of the macro pores increased and the wall thickness decreased, and a large number of micropores can be observed on the pore walls. Meanwhile the equilibrium swelling ratio of St‐MP SAP first increased and then decreased, and reached maximum as high as 1878 g/g and 119 g/g in distilled water and NaCl aqueous solution respectively for the sample with presence of 0.8 wt % SHC. Furthermore, the swelling rate constant (k) increased monotonously and fast swelling was presented. The macro and micropore structure in St‐MP SAP enabled water to flow by capillary effect with much fewer obstructions, and the specific surface area increased, with the result that more hydrophilic groups can get in touch with water molecules rapidly. By introduction of SHC, the water molecules which can form hydrogen bonds with St‐MP SAP molecules decreased, resulting in the decrease of the binding capacity of water molecules and water retention property. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44855.     

瓜尔胶基高吸水性树脂的制备、溶胀行为与保水性能

以天然瓜尔胶（GG）和丙烯酸（AA）为原料,过硫酸铵（APS）为引发剂,N,N′-亚甲基双丙烯酰胺（MBA）为交联剂,采用水溶液聚合法制备了瓜尔胶接枝聚丙烯酸（GG-g-PAA）高吸水性树脂。考察了MBA浓度对树脂溶胀动力学和溶胀能力的影响,研究了树脂在不同亲水有机溶剂/水混合溶液、不同阳离子盐（NaCl、CaCl₂和FeCl₃）和阴离子盐（KNO₃、K₂SO₄和K₃PO₄）溶液中在各浓度和离子强度下的溶胀行为,测定了高吸水性树脂在室温和高温下的保水性能。结果表明,该树脂对亲水有机溶剂较为敏感,吸水倍率随着亲水有机溶剂浓度的增加迅速减小;在各种盐溶液中的吸水倍率随着离子强度的增加而下降。     

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     

New smart carrageenan‐based superabsorbent hydrogel hybrid: Investigation of swelling rate and environmental responsiveness

Synthesis of novel natural‐based superabsorbents with improved properties is of prime importance in many applications. In this article we report an efficient synthesis of new polysaccharide‐based superabsorbent hybrid composing carrageenan, acrylic acid, sodium acrylate, and 2‐hydroxyethyl acrylate through homogenous solution polymerization process. Infrared spectroscopy and thermogravimetric analysis (TGA) were carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was examined by scanning electron microscopy (SEM). To deeper studies on the structure‐property relation in SAP hydrogels, three hydrogels with different acrylic acid/2‐hydroxyethyl acrylate (AA/HEA) weight ratios were synthesized and swelling capacity in various media was assessed. The hydrogel hybrid was also tested to be swollen and deswollen alternatively in 0.01 and 0.1 M sodium chloride solution. Moreover, the swelling‐deswelling capability of the hydrogel in alternatively changed methanol‐water mixtures was studied. Additionally, the swelling kinetics of the synthesized hydrogels were examined. The absorbency under load (AUL) of hydrogel was also investigated by using an AUL tester at various applied pressures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,characterization, and swelling behavior of superabsorbent hydrogel from sodium salt of partially carboxymethylated tamarind kernel powder‐g‐PAN

Polyacrylonitrile (PAN)‐grafted sodium salt of partially carboxymethylated tamarind kernel powder (Na‐PCMTKP‐g‐PAN, %G = 413.76 and %GE = 96.48) was prepared using the established optimal reaction conditions for ceric‐initiated graft copolymerization of acrylonitrile onto Na‐PCMTKP (DS = 0.15) in a homogeneous medium. The graft copolymer was hydrolyzed by 0.7N KOH solution at 90–95°C to yield the superabsorbent hydrogel H‐Na‐PCMTKP‐g‐PAN. The nitrile groups of Na‐PCMTKP‐g‐PAN were completely converted into a mixture of hydrophilic carboxamide and carboxylate groups during alkaline hydrolysis, followed by in situ crosslinking of the grafted PAN chains. The products were characterized spectroscopically and morphologically. The swelling behavior of the unreported superabsorbent hydrogel, H‐Na‐PCMTKP‐g‐PAN, was studied by carrying out its absorbency measurements in low‐conductivity water, 0.15M salt (NaCl, CaCl₂, and AlCl₃) solutions, and simulated urine (SU) at different timings. The swelling behavior of the hydrogel in different swelling media followed the second‐order kinetics. The values of the various swelling characteristics were reported. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development of a superporous hydroxyethyl cellulose‐based hydrogel by anionic surfactant micelle templating with fast swelling and superabsorbent properties

The self‐assembling anionic surfactant, sodium n‐dodecyl sulfonate (SDS) micelles were used as pore‐forming templating for fabricating novel superporous hydroxyethyl cellulose‐grafting‐poly(sodium acrylate)/attapulgite (HEC‐g‐PNaA/APT) hydrogels. The network characteristics, morphologies of the hydrogels and removing of SDS micelles from the final product by washing with ethanol/water (v/v, 7 : 3) procedure were determined by Fourier transform infrared spectroscopy and scanning electron microscopy, as well as by determination of swelling ratio, swelling rate, and stimuli response to salts and pHs. The results showed that the added‐SDS concentration significantly affected the morphologies and pore structure of the hydrogel, and 2 mM SDS facilitates to form a homogeneous and well‐defined pore structure in the gel network to extremely improve the swelling ratio and swelling rate. The 2 mM SDS‐added superporous HEC‐based hydrogel not only had highest equilibrium swelling ratio (Q_eq, 1118, 102 g g^?1 in distilled water and 0.9 wt % NaCl solution), rapid swelling rate (k_is, 5.2840 g g s^?1), also showed multistimulus responses to salts and pHs, which may allow its applications in several areas such as adsorption, separation and biomedical materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42027.     

PAA/PNIPAAm互穿网络水凝胶的微波合成与性能研究

以微波为辐射源,对丙烯酸(AA)水溶液进行辐照制得了PAA水凝胶。将脱水后的PAA水凝胶浸泡于含引发剂过硫酸钾(K_2S_2O_8)和交联剂N,N’-亚甲基双丙烯酰胺(BIS)的N-异丙基丙烯酰胺(NIPAAm)水溶液中,待溶胀平衡后取出,进行第二次微波辐照反应,制备了聚丙烯酸/聚N-异丙基丙烯酰胺互穿聚合物网络(PAA/PNIPAAm IPN)水凝胶,并对其溶胀性能进行了研究。研究结果表明,合成的IPN水凝胶兼具pH敏感性和温度敏感性,有望在药物控制释放领域得到应用。     

新型黄原胶基高吸水性树脂的合成

在水溶性引发剂过硫酸钾的引发下,使丙烯酸（AA）在黄原胶（XG）分子链上接枝聚合,并加入N,N′-亚甲基双丙烯酰胺进行一定程度的交联,制备高吸水性树脂。研究了反应条件对产品吸水率的影响,利用傅里叶红外光谱、X射线衍射、偏光显微镜对接枝共聚物进行表征。实验结果表明：最佳合成条件AA与XG质量比m(AA) ∶m(XG)=6∶1,交联剂、引发剂与黄原胶的质量比分别为0.01和0.003,丙烯酸的中和度为70%,反应温度为60 ℃,反应时间为4 h。最佳合成条件下制备的树脂最大吸水倍数854 g/g,吸生理盐水倍数156 g/g。     

Enhanced swelling and responsive properties of an alginate-based superabsorbent hydrogel by sodium p-styrenesulfonate and attapulgite nanorods

In this work, a series of sodium alginate-g-poly(sodium acrylate-co-sodium p-styrenesulfonate)/attapulgite (NaAlg-g-poly(NaA-co-NaSS)/APT) superabsorbent composites were prepared by graft copolymerization using N,N’-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate as an initiator. Fourier transform infrared spectroscopy revealed that NaA and NaSS had been grafted onto NaAlg, and APT participated in polymerization reaction through reactive –OH groups. The introduction of proper amount of NaSS and APT induced the improved surface morphology, swelling capacity, and swelling rate. Moreover, the swelling behaviors of the superabsorbent composites were remarkably influenced by various salt medium, pH buffer solutions and organic solvents, and especially an intriguing swelling–deswelling behavior was observed with altering water/organic solvent ratio.