Hydrogels of starch/carboxymethyl cellulose crosslinked with sodium trimetaphosphate via reactive extrusion

Hydrogels are materials with advantages in specific applications, such as, retention of food active compounds. This work aims to develop starch (S)/carboxymethyl cellulose (CMC) hydrogels with porous structure, using reactive extrusion to promote crosslinking with sodium trimetaphosphate (STMP). The expansion, porosity, degree of substitution, gel fraction, swelling properties, and FTIR are studied, comparing S, S/CMC, S/STMP, and S/CMC/STMP formulations. Samples containing STMP present the same degree of substitution (0.050 ± 0.001). Higher porosity and percentage of open pores are observed in the mixed hydrogel (S/CMC/STMP). Crosslinking increase the swelling capacity at pH 7, and this property, just like the gel fraction, are sensitive to pH variations. The hydrogel S/CMC present the highest swelling rate compared with the other samples, suggesting strong interaction between components. The reactive extrusion process is efficient to produce starch and starch/CMC hydrogels crosslinked with STMP and the overall results demonstrate the advantages of the mixed hydrogel.     

An approach for preparing an absorbable porous film of silk fibroin–rice starch modified with trisodium trimetaphosphate

The absorbable porous material, especially gelatin porous film, is widely used for surgical use to stop bleeding, but its price is quite high. Thus, a new material at lower price with desirable properties is required. This article presents an approach to prepare a porous film of silk fibroin–rice starch (SF–RS) modified with trisodium trimetaphosphate (STMP). The preparation was performed using freeze‐drying method aiming to increase the porosity and improve some other properties of the modified porous film. The solutions of SF and RS (5 : 95 weight ratio) and STMP were mixed and adjusted to pH 12 before being neutralized to pH 7 and freeze‐dried for 48 h. Result from the SEM images showed that the average pore size of the SF–RS film increased from 17 to 126 μm after STMP was added up to 5.0% w/w. Similar to the SF–RS–STMP hydrogel, the linkages within the modified SF–RS porous film also occurred mainly between the O? H groups of RS and the triphosphate group of STMP. Moreover, cross‐linking density of the porous film increased with the increasing content of STMP, evidenced from the increase of relative methylene blue adsorption. The addition of STMP also affected the physical properties of the modified porous film such as degree of swelling, oxygen permeability, but not the water solubility. Whereas, the residual ash of the modified porous films was lower than 2.0% and the degradation of the film ceased after soaking in 0.01M PBS solution for about 2 weeks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41517.     

Crosslinking of corn starch with sodium trimetaphosphate in solid state by microwave irradiation

Corn starch was crosslinked with sodium trimetaphosphate (STMP) in solid state under microwave irradiation to improve the degree of substitution (DS) and decrease the reaction time. The effects of modification factors on the crosslinking of starch were systematically studied. It was found that the microwave irradiation provided a convenient and efficient method to prepare crosslinked starch with sufficient DS. The DS value of crosslinked starches obtained by microwave irradiation was significantly improved and the reaction time was also dramatically decreased to achieve an appropriate DS value by microwave irradiation, when compared with using traditional method. The high microwave power provided faster reaction kinetics to obtain the desired DS value at an identical reaction condition. If the reaction temperature is lower than the decomposition temperature of crosslinked starch, the higher DS value can be achieved at the higher microwave power. It was detected that the DS data obtained by reacting intermittently was higher than those by reacting continuously. It was also noticed that DS data varied drastically with the increasing of the amount of STMP and sodium carbonate. The swelling ratio of crosslinked starch in water was lower than that of native starch because of the nongelatinization of highly crosslinked starch. SEM analysis indicated that the crosslinking of corn starch by microwave irradiation caused no significant changes in the microstructure of starch granules. Light microscope analysis also showed the uniformity of so‐prepared crosslinked corn starch applying microwave irradiation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5854–5860, 2006     

Preparation and characterization of chitosan films,crosslinked with symmetric aromatic dianhydrides to achieve enhanced thermal properties

This study has developed a new generation of crosslinked chitosan‐based films using symmetric aromatic dianhydrides as crosslinking agents. The formation of the dianhydride‐crosslinked chitosan hydrogel films was confirmed using Fourier transform infrared and solid‐state ¹³C NMR spectral analyses. The films obtained from these derivatives were characterized by their thermal, swelling and hydrophilic properties. The results showed that introducing a cyclic imide moiety into the chitosan matrices played a significant role in enhancing the thermal properties of these chitosan films. It was found that even at high levels of substitution, thermal stability of the studied chitosan derivatives was improved, in spite of a reduction in crystallinity. Heterocyclic imide linkages produced networks that were insoluble in both acidic and alkaline media but allowed swelling in aqueous media. An increase in the hydrophobicity of the chitosan film surfaces was observed after introduction of the cyclic imide moiety. These engineered films produced noteworthy results concerning their thermal and swelling properties. There is a need to further investigate these films for drug delivery and biomaterials applications. © 2014 Society of Chemical Industry     

Preparation and characterization of microporous sodium poly(aspartic acid) nanofibrous hydrogel

A novel biodegradable sodium poly(aspartic acid) (PASP) hydrogel with microporous structure was manufactured using electrospun polysuccinimide (PSI) nanofibers. PSI is the intermediate of sodium PASP and could be electospun into nanofibers easily. Firstly, PSI nanofibers were prepared from PSI/N, N-dimethylformamide solution. Then the PSI nanofibrous mats were crosslinked and hydrolyzed to obtain biodegradable microporous sodium PASP nanofibrous hydrogels. The chemical structures, morphologies and pore sizes of PSI nanofibrous mats and microporous sodium PASP nanofibrous hydrogels were investigated. Moreover, the properties of PSI electrospinning solutions, and the swelling ratio and biodegradability of sodium PASP hydrogels were also examined. The results showed that the swelling ratio of microporous sodium PASP nanofibrous hydrogels achieved to 21.0–24.3 g/g and were obviously higher than that of the sodium PASP casting film, reporting a swelling ratio of only 4.6 g/g. When the microporous sodium PASP nanofibrous hydrogel was immersed in water, it exhibited quick absorption and morphological robustness. The microporous sodium PASP nanofibrous hydrogel showed 83 wt% weight loss after 7 days of trypsin catalyzed biodegradation, and the SEM analysis demonstrated the significant morphology change of the microporous sodium PASP nanofibrous hydrogel during the biodegradation.     

Crosslinked poly(vinyl alcohol) and starch composite films. II. Physicomechanical,thermal properties and swelling studies

Poly(vinyl alcohol) (PVA) was blended with 10, 20, 30, 40, and 50 wt % of starch with and without crosslinking by solution casting process. The solution‐casted films were dried and tested for physicomechanical properties like tensile strength, tensile elongation, tensile modulus, tear and burst strengths, density, and thermal analysis by differential scanning calorimetry (DSC). These PVA/starch films were further characterized for moisture content; solubility resistance in water, 5% acetic acid, 50% ethanol, and sunflower oil; and swelling characteristics in 50% ethanol and sunflower oil. The crosslinked PVA/starch composite films show significant improvement in tensile strength, tensile modulus, tear and burst strengths, and solubility resistance over the uncrosslinked films. Between the crosslinked and uncrosslinked films, the uncrosslinked films have higher tensile elongation, moisture content, moisture absorption, and swelling over the crosslinked films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 909–916, 2007     

Crosslinked glutinous rice starch filled polyvinyl alcohol films

The influence of glutinous rice starch (GRS) content and sodium hexametaphosphate (SHMP) in polyvinyl alcohol (PVOH) films were studied. The increase of GRS content (0–40 wt%) reduced the tensile strength (from 14.3 to 4.3 MPa) and elongation at break (from 183 to 52.5) of PVOH/GRS films. Nevertheless, the modulus of elasticity of PVOH/GRS films increased with GRS content, from 20.3 to 132.83 MPa. SHMP was used as a crosslinking agent, which improved more than 30% of tensile strength and modulus of elasticity of PVOH/GRS films. However, the elongation at break reduced after crosslinking process of the films. The crosslinked film showed better interaction between GRS and PVOH, as demonstrated by scanning electron microscopy. Conversely, the crosslinked films exhibited a lower swelling degree, but a higher gel content compared to uncrosslinked films. J. VINYL ADDIT. TECHNOL., 25:359–365, 2019. © 2019 Society of Plastics Engineers     

Tensile,Swelling, and Oxidative Degradation Properties of Crosslinked Polyvinyl Alcohol/Chitosan/Halloysite Nanotube Composites

Glutaraldehyde (GA) crosslinked polyvinyl alcohol (PVA)/chitosan (CS)/halloysite nanotube (HNT) composite films were prepared using a wet casting method. The tensile, morphology, thermal degradation, swelling, moisture, and oxidative degradation properties of crosslinked composite films were carried out. The presences of crosslinking in the composite films were confirmed by FTIR result. The tensile strength of the crosslinked composite films increased up to 0.5 wt% of HNTs loading. Increasing HNTs reduced the thermal degradation, swelling, and moisture properties of crosslinked composite films reduced with the increase of HNTs content. Results also indicated that the crosslinked composite films were degraded using Fenton reagent.     

Preparation,characterization, and photocatalytic degradation properties of polyacrylamide/calcium alginate/TiO2 composite film

Titanium dioxide (TiO₂) nanoparticles were dispersed in the sodium alginate and acrylamide aqueous solution to prepare the casting solution. The casting solution was spread on a glass plate by a glass rod enlaced with brass wires to control the thickness of the film. Then polyacrylamide/calcium alginate/TiO₂ (PAM/CA/T) composite film was obtained after UV irradiation and crosslinking by CaCl₂. The PAM/CA/T film was characterized by scanning electron microscopy and transmission electron microscope. The mechanical properties of the films were tested in wet form and the results showed that PAM/CA/T film had good strength and toughness. PAM/CA/T films did not rupture after swelling in 5.0 wt% NaCl solution and still had good mechanical properties. The PAM/CA/T hydrogel film provided a suitable carrier for TiO₂ in the photocatalytic degradation of dyes and the degradation rate of PAM/CA/T‐30 for methyl orange reached 80.8%. The PAM/CA/T film had good reusability and could degrade dyes in a high concentration of NaCl solution. POLYM. COMPOS. 37:1292–1301, 2016. © 2014 Society of Plastics Engineers     

Swelling-induced surface instability of a hydrogen-bonded LBL film and its self-healing

Thin hydrogel films attached to a rigid substrate can only swell along the direction perpendicular to the substrate, which generates compressive stress within the gel. When the stress is sufficiently large, the free surface of the gel will locally buckle and fold against itself to form various wrinkling patterns. Here we show that hydrogen-bonded layer-by-layer (LBL) films of poly(vinyl pyrrolidone) (PVPON) and poly(acrylic acid) (PAA) also swell in ethanol/water mixtures. Like ordinary hydrogel films attached to a substrate, the LBL films also undergo mechanical instability when their swelling degree is large enough. By adjusting the composition and pH of the ethanol/water mixture, the swelling degree of the film can be adjusted, which further decides whether the mechanical instability occurs or not. Like ordinary hydrogel films, the surface wrinkling of the PVPON/PAA films occurs via a nucleation-growth process. Unlike ordinary hydrogels, the critical swelling degree for the onset of wrinkling for PVPON/PAA films increases with increasing film thickness. More importantly, the wrinkling patterns can be healed automatically, because the transient network of PVPON/PAA films allows for the relief of compressive stress via its rearrangement. The phenomenon observed here may provide a possible way to erase the undesired wrinkling patterns on constrained hydrogel films.     

Synthesis,characterization, and enzymatic degradation of chitosan/PEG hydrogel films

Poly(ethyleneglycol) (PEG)/tartaric acid (TA)‐crosslinked chitosan hydrogel (CPT) films were prepared, and the formation of the PEG/TA‐crosslinked structure was confirmed by Fourier transformed infrared (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscope (SEM) measurements. The thermal properties of the crosslinked films were also determined with thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis. The swelling properties of the films were investigated at different temperature and pH values. It was found that the swelling ratio increased with the decrease of pH value of the surrounding buffer solutions, amount of PEG, and with the increase of temperature. Swelling behavior of the PEG/TA‐crosslinked chitosan hydrogel films depended on pH and reversible with the temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of novel hyperbranched poly(amine‐ester) films crosslinked by glutaraldehyde

Novel films based on hydroxyl terminated hyperbranched poly (amine‐ester) (HPAE‐OH) of different generation were prepared by crosslinking the terminal hydroxyl groups of HPAE with glutaraldehyde (GA). The progress of crosslinking reaction was characterized by Fourier transform infrared (FTIR) and viscosity measurement. The surface morphology of the crosslinked HPAE films was characterized by field emission scanning electron microscope (FE‐SEM) and atomic force microscopy. The results suggested that the films have homogenously dense interior matrices and smooth surface. The hydrophilicity/hydrophobicity of the crosslinked HPAE films was characterized by the water contact angle measurement. Variable swelling behavior in different solvents was also studied. The in vitro biocompatibility of the film was investigated by the bovine hemoglobin (Hb) adsorption measurement. And these results showed that these crosslinked HPAE films had excellent hydrophilicity, variable swelling behavior in different solvents, and relative low protein absorption. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Edible starch sodium octenyl succinate film formation and its physical properties

Edible starch sodium octenyl succinate (SSOS) films, with or without glycerol as plasticizer, were prepared by solution‐casting method. The effect of SSOS concentration, degree of substitution (DS) of octenyl group, as well as glycerol content, on the properties of SSOS films was studied including tensile strength, water vapor permeability (WVP), and oil permeability (OP). The results indicated that the tensile strength of SSOS film was up to 39.4 ± 1.9 MPa when the concentration of SSOS was 0.05 g/mL and DS was 0.05. The increase of glycerol content resulted in a decrease of film tensile strength. WVP of SSOS films was relatively low. Meanwhile, study in OP showed that SSOS films were oilproof. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Radiation initiated synthesis of 2‐acrylamidoglycolic acid grafted carboxymethyl cellulose as pH‐sensitive hydrogel

This article exploits a new approach for synthesis of carboxymethyl cellulose/poly 2‐acrylamidoglycolic acid by graft and crosslinked copolymerization in aqueous solution by a simple one‐step using γ‐radiation. The reaction parameters affecting the equilibrium swelling, i.e., mass ratio of AG to CMC and irradiation dose were systematically optimized to achieve a superabsorbent hydrogel with a maximum swelling capacity. The structure, crystallinity, thermal stability, and surface morphology were characterized by Fourier transform infrared spectroscopy (FT‐IR) and elemental analysis, X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. FTIR proved that the grafting reaction occurred between the hydroxyl group of CMC and PAG chain. The thermal analysis data show that the prepared hydrogel is more thermally stable than pure CMC. The swelling behaviors in distilled water in various pH solutions, temperature and various ionic salt solutions (NaCl as monovalent, CaCl₂ as divalent and FeCl₃ as trivalent) were investigated in detail. The effect of cationic salt solutions on the swelling had the following order: Na⁺ > Ca²⁺ > Fe³⁺. In addition, the pH‐reversibility was preliminarily investigated with alternating pH between 12 and 2. The equilibrium swelling of CMC/PAG was achieved in 70 min. The hydrogel was responsive to the pH and salts; it also has reversible swelling and deswelling character. POLYM. ENG. SCI., 54:2753–2761, 2014. © 2013 Society of Plastics Engineers     

Adsorption removal of Brilliant green and Safranin-O contaminants from water using a hydrogel based on carboxymethyl cellulose and sodium alginate crosslinked by epichlorohydrin

The current study investigates the adsorption properties of a chemically crosslinked hydrogel based on sodium alginate (NaALG) and carboxymethyl cellulose (CMC). The structural characteristics of the investigated hydrogel are described using information from Fourier Transform–infrared spectra, X-ray diffraction patterns and field emission scanning electron microscopy pictures. The NaALG/epichlorohydrin (ECH)/CMC hydrogel was synthesised under optimised conditions with respect to the swelling percentage. Various reaction parameters were varied to obtain the maximum swelling percentage. The synthesised hydrogel was taken as an adsorbent in the decolorisation of Brilliant green (BG) and Safranin-O (SO) dyes from water. According to the kinetic investigations, the decolorisation equilibrium of SO by NaALG/ECH/CMC was discovered in 4 hours (98.98%), while the removal of BG by NaALG/ECH/CMC took 6 hours (97.7%). Chemical processes were used to describe the decolorisation mechanisms, which significantly supported the pseudo-first-order model. NaALG/ECH/CMC hydrogel absorption was indicated to take place in monolayer adsorption form (Langmuir isotherm). The highest adsorption capacity for BG was discovered to be 864.8 mg g⁻¹ and for SO it was 193.1 mg g⁻¹, by synthesised hydrogel, where “mg” refers to the commercial colourant and not to the pure dye. Therefore, the synthesised hydrogel can be considered as a smart device for the adsorption of dye in water purification tasks.     

Synthesis and characterization of photo-crosslinkable hydrogel membranes based on modified chitosan

In order to develop a non toxic and biocompatible hydrogel system with potential ability in biotechnology, modified photo-crosslinkable hydrogel membranes based on chitosan were prepared. Using an EDC/NHS conjugation method, chitosan was chemically modified to incorporate a photosensitive α-cyano-4-hydroxycinnamic acid moiety with various degrees of substitutions. Fourier transform infrared spectra (FTIR), proton nuclear magnetic resonance (¹H NMR) and ultraviolet-visible light spectra (UV-vis) were used for structural characterization of modified chitosan, The obtained membranes were crosslinked by irradiation in the ultraviolet region, where the photosensitive monomers showed maximum sensitivity. The prepared photo-crosslinked hydrogel membranes were investigated by thermal gravimetric analysis (TGA) and wide angle X-ray diffraction (WAXD). The swelling behaviors were investigated in terms of pH, time of swelling, and degree of substitution. Also, mechanical properties of the different photo-crosslinked hydrogel membranes were studied in both dry and wet conditions.     

SA/PVA可降解复合塑料膜的制备与性能研究

对木薯原淀粉进行乙酰化改性,合成低酯化度的木薯淀粉醋酸酯(SA);经增塑、交联后与聚乙烯醇(PVA)合成可降解的SA/PVA复合塑料膜,重点研究了PVA、甘油、乙二醛的用量及SA的酯化度对复合膜力学性能的影响,并对复合膜性能进行了表征。结果表明:在PVA质量分数为40%,甘油质量分数为14%,乙二醛质量分数为4%时,可以得到力学性能较好的复合塑料膜;与原淀粉/PVA复合膜相比,复合膜致密性提高,玻璃化转变温度降低,结晶度下降,表现出更好的力学性能。     

Preparation of resistant starch/poly(vinyl alcohol) blend films with added plasticizer and crosslinking agents

We report on the physical properties of films synthesized with native corn starch (NCS) and resistant starch (RS4) prepared with NCS. NCS and RS4/poly(vinyl alcohol) (PVA) blend films were synthesized with a mixing process and casting method. Glycerol (GL) and citric acid (CA) were used as additives. Glutaraldehyde (GLU) was used as a crosslinking agent of the films. RS4 was synthesized with sodium trimetaphosphate and sodium tripolyphosphate as a crosslinker. Then, the RS4 thus synthesized was confirmed by the pancreatin–gravimetry method, swelling power, differential scanning calorimetry, and X‐ray diffraction. The tensile strength, elongation, swelling behavior, and solubility of the films were measured. The results of the measurements indicated that the RS4‐added film was better than the NCS‐added film. In particular, the RS4/PVA blend film with CA as an additive showed physical properties superior to those of the other films. Also, the physical properties with GLU added as a crosslinking agent to the films were investigated. With increasing GLU contents, the tensile strength increased but the elongation, swelling behavior, and solubility values of the GL‐added and CA‐added films decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of treelike and rodlike carboxymethylated nanocellulose and their effect on carboxymethyl cellulose films

In this work, carboxymethyl cellulose (CMC) with low substitution degree, followed by different posttreatments, was applied to prepare treelike CMC nanofibrils (CMCNFs) and rodlike CMC nanocrystals (CMCNCs), and their performance in CMC composite film was evaluated simultaneously. From transmission electron microscopy results, it was found that the treelike CMCNCFs exhibited a lager aspect ratio compared to the rodlike CMCNCs. As for reinforcing CMC film, 4 wt% was the best adding amount, at this time, the tensile strength of CMC/CMCNFs and CMC/CMCNCs composite films was increased by 72.1% and 47.3%, respectively. Moreover, adding these nanofillers to CMC also could enhance the thermal stability of composite films slightly, while the transmittance of composite films was reduced at the same time. In addition, CMC/CMCNFs film was designed as a packaging box to determine its performance. Therefore, this study could reveal the differences of properties for composites with different types of nanocellulose and provide a foundation for further application of nanocellulose.     

Properties of starch‐based blend films using citric acid as additive. II

Starch/polyvinyl alcohol (PVA) blend films were prepared by using corn starch, polyvinyl alcohol (PVA), glycerol (GL), and citric acid (CA) as additives and glutaraldehyde (GLU) as crosslinking agent for the mixing process. The additives, drying temperature, and the influence of crosslinker of films on the properties of the films were investigated. The mechanical properties, tensile strength (TS), elongation at break (% E), degree of swelling (DS), and solubility (S) of starch/PVA blend film were examined adding GL and CA as additives. At all measurement results, except for DS, the film adding CA was better than GL because hydrogen bonding at the presence of CA with hydroxyl group and carboxyl group increased the inter/intramolecular interaction between starch, PVA, and additives. CA improves the properties of starch/PVA blend film compared with GL. TS, % E, DS, and S of film adding GLU as crosslinking agent were examined. With increasing GLU contents, TS increases but % E, DS, and S value of GL‐added and CA‐added films decrease. When the film was dried at low temperature, the physical properties of the films were clearly improved because the hydrogen bonding was activated at low temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2554–2560, 2006