Influence of chemical nature of citric and malic acids on reaction time of the crosslinking of polyvinyl alcohol hydrogels (2025)

Incorporation of organic acids in the crosslinking of polyvinyl alcohol hydrogels

Polimeros-ciencia E Tecnologia, 2022

This work studied the incorporation of organic acids as crosslinking agents and reaction time on the properties of poly(alcohol vinyl) (PVOH) hydrogels to act as scaffold systems to compounds incorporated into agriculture systems. PVOH hydrogels crosslinked with citric and L-malic acids were prepared, and the effects of heat-treatment time, and temperature on their swelling and hygroscopic performances were investigated by FTIR, thermal analysis and swelling. Both the swelling and rate of water uptake of hydrogels decreased with increasing heat-treatment time. While the swelling decreased with heat-treatment time, the chemical crosslinking shown in FTIR increased. DSC results indicated adsorbed water in the uncrosslinked PVOH and hydrogels, and the absorbed water changed the melting point and glass transition temperature. TGA analysis showed that the incorporation of organic acids brought thermal stability. The results obtained show effective crosslinking hydrogels by L-malic acids and possibilities to use in scaffold systems and controlled release.

Preparation and Characterization of Hydrogel Based on Poly(vinyl alcohol) Cross-Linked by Different Cross-Linkers Used to Dry Organic Solvents

Journal of Polymers and The Environment, 2010

Poly(vinyl alcohol) (PVA) hydrogels were chemically cross-linked with/without different cross-linkers such as glutaraldehyde and epichlorohydrin, in the presence of a catalyst, or activator (potassium hydroxide) to produce three types of hydrogels. The structures of PVA and the prepared gel types were determined by FTIR spectroscopy, the mechanical and thermal properties, of these hydrogels were examined. The effects of different pH values and temperatures on the swelling properties of the prepared gels were examined. From the obtained results, it was found that, the low concentration of the cross-linker produced hydrogel with moderate properties, but in absence of the cross-linker, the obtained hydrogel exhibited good properties and can be used as friendly environmentally moisture absorbents from the organic solvents. The insolubility and swelling properties of gels were tested in these solvents. The results indicated that these hydrogels can be used as moisture absorbents and solvent dryers.

EFFECT OF CHEMICAL CROSSLINKING ON SWELLING PARAMETERS OF MODIFIED POLY(VINYL ALCOHOL) HYDROGEL

Graft copolymerization of maleic anhydride (MA) onto partially and fully hydrolyzed poly(vinyl alcohol), PVA, was carried out in presence and in absence of an initiator. The structural features of these grafts were confirmed by JHNMR analysis. JHNMR analysis was also used to determine the percentage of grafting. These grafts were crosslinked using different concentrations of either l,l,l-trimethylolpropane trimethacrylate (TPT) or methylene bisacrylamide (MBA) as Hexa-or tetra-functional crosslinker, respectively. The crosslinkers concentrations ranged from 1% to 30% (wt. %) based on the total weight of grafts. The final water content, volume fraction of the polymer and swelling capacity were determined for all grafts. The effect of MBA and TPT crosslinkers structure on swelling properties of both partially and fully hydrolyzed PVA grafts were also determined.

New chemical hydrogels based on poly(vinyl alcohol)

Journal of Polymer Science Part A: Polymer Chemistry, 1996

SYNOPSIS The syntheses of two new types of chemical hydrogels based on poly(viny1 alcohol), PVA, are reported. Common to both synthetic routes is the preparation of a telechelic PVA (tel-PVA) obtained by periodate splitting of the vicinal diol units present in few percent along the chain. tel-PVA was then used as crosslinking agent with chitosan and PVA in two simple reactions in aqueous phase such as reductive alkylation of chitosan and acetalyzation of PVA. Both reactions yielded firm wall-to-wall networks showing marked differences in their swelling capability. 0 1996 John Wiley & Sons, Inc.

Characterization of Methylcellulose Based Hydrogels by Using Citric Acid as a Crosslinking Agent

2018

This research work aims at studying citric acid crosslinking capacity, evaluating structural modifications produced on hydrogels based on methylcellulose and sorbitol, along with the effect on the barrier properties of the obtained hydrogels. This additive, besides its preservative capacity in foods, can act as a crosslinking agent in some polymers matrix. Methylcellulose (A4M) solutions were prepared at 1.5%/ v at 80 °C. Sorbitol analyzed concentration was 0.25%. Citric acid was added to 5 and 10 (p/pMC) concentrations as a crosslinker agent in hydrogels forming solutions. Hydrogels were obtained by casting and drying method. Moisture content, swelling capacity and films’ solubility in water at different temperatures were evaluated. Hydrogels’ microstructural and mechanical properties were determined through DMTA and FTIR. Water vapor permeability was determined according to the ASTM E96 standard, and oxygen permeability through an Oxtran 2/20 permeability meter by following the me...

Study of Hybrid Hydrogel Based on Polyvinyl Alcohol with Respect to Tailoring of the Internal Structure by Lecithin

Research Square (Research Square), 2023

The presented paper is focused on preparation and subsequent characterization of structural and transport properties of hydrogels with double-network concerning their application potential. Hybrid hydrogels were prepared as a combination of synthetic polymer and natural polysaccharide, such as polyvinyl alcohol (PVA) and sodium alginate (SA), where mass ratio of those polymers was 1:1. In the preparation of the gel's hybrid network a freeze-thawing cycle technique for physical cross-linking of PVA was used, also calcium ions were used for ionic cross-linking of sodium alginate. Lecithin as a modi cation of the internal structure of hybrid hydrogels was also used in gel's system preparation. Physicochemical methods were used to characterise their viscoelastic, swelling and transport properties. Rheology measurements, speci cally oscillation and amplitude tests, were used to study these mechanical properties. Morphology of the prepared hybrid hydrogels was con rmed by electron microscope scanning. Transport and release properties of gel systems were determined by diffusion experiments with the UV-VIS spectrometry detection method, in which an organic dye (methylene blue) was used as a model probe.

Characterization of hydrogels formed from acrylate modified poly(vinyl alcohol) macromers

Polymer, 2000

Poly(vinyl alcohol) was modified with pendent acrylate groups to form a macromer that was crosslinked via photopolymerization. Polymerization behavior was studied for several initial macromer concentrations using DSC and Near-IR spectroscopy. Under mild photoinitiating conditions (e.g. 0.05 wt% initiator and less than 20 mW/cm 2 of 365 nm light), the hydrogels polymerized to 100% conversion in less than 5 min. To characterize the network structure, the hydrogels formed from the acrylated poly(vinyl alcohol) macromer were compared to gels that were chemically crosslinked with glutaraldehyde and gels that were physically crosslinked by semi-crystalline regions introduced through freeze-thaw cycles. The equilibrium swelling ratio and compressive modulus were characterized for all of the resulting PVA hydrogels, and related to the network structure (i.e. M c through a modified Flory-Rehner equation and rubber elasticity theory. ᭧

Synthesis of full and semi Interpenetrating hydrogel from polyvinyl alcohol and poly (acrylic acid-co-hydroxyethylmethacrylate) copolymer: Study of swelling behavior, network parameters, and dye uptake properties

Journal of Applied Polymer Science, 2011

Semi and full interpenetrating network (IPN) hydrogels were synthesized by allowing free radical copolymerization of acrylic acid (AA) and hydroxyethyl methacrylate (HEMA) in the matrix of polyvinyl alcohol (PVOH). Accordingly, four different semi IPN hydrogels were prepared with PVOH: copolymer mass ratio of 1 : 1, 1 : 0.75, 1 : 0.5, and 1 : 0.25. These hydrogels were designated as SEMIIPN1, SEMIIPN2, SEMIIPN3, and SEMI-IPN4, respectively. In all of these SEMIIPN, after polymerization PVOH was crosslinked with 2 mass % glutaraldehyde to form the semi IPN structure. In a similar way, sequential full IPN were prepared from PVOH and copolymer of AA and HEMA (designated as PAA-HEMA) with same composition except in this case apart from crosslinking of PVOH by 2 mass % glutaraldehyde the PAAHEMA copolymer was further crosslinked with N,N 0-methylenebisacrylamide (NMBA) to produce four full IPN hydrogels designated as FULLIPN1, FULLIPN2, FULLIPN3, and FULLIPN4. All of these semi and full IPN type hydrogels were characterized by carboxylic %, FTIR, UV, DTA-TGA, XRD, SEM, and mechanical properties. The network parameters, swelling and diffusion characteristics of these hydrogels were also studied. The performance of these semi and full IPNs were compared in terms of their relative abilities for removing varied concentration of rhodamine B (RB) and methyl Violet (MV) dyes from water. V

Poly(vinyl alcohol) Hydrogels: The Old and New Functional Materials

International Journal of Polymer Science, 2021

Hydrogels have three-dimensional network structures, high water content, good flexibility, biocompatibility, and stimulation response, which have provided a unique role in many fields such as industry, agriculture, and medical treatment. Poly(vinyl alcohol) PVA hydrogel is one of the oldest composite hydrogels. It has been extensively explored due to its chemical stability, nontoxic, good biocompatibility, biological aging resistance, high water-absorbing capacity, and easy processing. PVA-based hydrogels have been widely investigated in drug carriers, articular cartilage, wound dressings, tissue engineering, and other intelligent materials, such as self-healing and shape-memory materials, supercapacitors, sensors, and other fields. In this paper, the discovery, development, preparation, modification methods, and applications of PVA functionalized hydrogels are reviewed, and their potential applications and future research trends are also prospected.

Formulation, Characterization, Study of Swelling Kinetics and Network Parameters of Poly (MA-co-VA-co-AA) Terpolymeric Hydrogels with Various Concentrations of Acrylic Acid

Journal of Research Updates in Polymer Science, 2013

The ter-polymeric hydrogels of vinylacetate (VA), methacrylate (MA) and acrylicacid (AA) were prepared using ethyleneglycoldimethacrylate (EGDMA) as a cross linker and benzoylperoxide (BPO) as an initiator. The effect of acrylic acid concentration on various swelling parameters was studied at different pHs (1.0, 4.0, 5.5, 7.4 and 8.0). A promising relationship was found to exist between media penetration velocity and equilibrium media content of hydrogels at all pH values for various concentration of acrylic acid. The fastest dynamic swelling was observed for the highest concentration of acrylic acid (40 mol % of AA) at pH 8.0. In the kinetic study, during the first hours, a first order kinetics (Fick Model) was observed at pH higher than the value of pKa (4.75) of acrylic acid, the hydrogels exhibiting non-Fickian diffusion mechanism. Whereas, for the acidic media pH, a second order kinetics was observed (Schott Model). Network parameters strongly support the swelling out comes. The relaxations of the ter-polymeric chain were observed after swelling at pH 8.0 via SEM pictures. Thermo gravimetric analysis and differential scanning calorimetric analysis also agree with the above conclusions. Well controlled swelling behavior, network properties, SEM out comings and thermogravimetric analysis support the idea to use these hydrogels for targeted drug delivery in the colon part of the digestive tract.