Copolymers based on poly (vinyl alcohol) and acrylamide (original) (raw)
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Journal of Applied Polymer Science, 2020
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.
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. ᭧
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
Fibers and Polymers, 2004
A series of superabsorbents based on acrylic acid (AA), sodium acrylate, 2-acrylamido-2-methylpropane sulphonic acid, N,N′-methylene bis-acrylamide (MBA) were prepared by inverse suspension polymerization. These hydrogels were further crosslinked on the surface with polyethylene glycol-600 (PEG-600). The water absorbency or swelling behaviors for these xerogels in water and 0.9% saline solutions, both under free condition and under load were investigated. Absorption characteristics of these hydrogels were found to depend on nature and concentration of crosslinker in the system. It was also found that the saline absorption was significantly improved as the incorporation of AMPS in the polymer was increased. The surface crosslinking introduced in the polymers was found to improve the absorption under load characteristics without lowering the free water absorption capacities of the polymer to a considerable extent.
2002
Hyperbranched poly(ester amide) polymer (Hybrane™ S1200; M n 1200 g/mol) was functionalized with maleic anhydride (MA) and propylene sulfide, to obtain multifunctional crosslinkers with fumaric and thiol-end groups, S1200MA and S1200SH, respectively. The degree of substitution of maleic acid groups (DS) was controlled by varying the molar ratio of MA to S1200 in the reaction mixture. Hydrogels were obtained by UV crosslinking of functionalized S1200 and poly(ethyleneglycol) diacrylate (PEGDA) in aqueous solutions. Compressive modulus increased with decreasing the S1200/PEG ratio and also depended on the DS of the multifunctional crosslinker (S1200). Also, heparin-based macromonomers together with functionalized hyperbranched polymers were used to construct novel functional hydrogels. The multivalent hyperbranched polymers allowed high crosslinking densities in heparin modified gels while introducing biodegradation sites. Both heparin presence and acrylate/thiol ratio have an impact on degradation profiles and morphologies. Hyperbranched crosslinked hydrogels showed no evidence of cell toxicity. Overall, the multifunctional crosslinkers afford hydrogels with promising properties that suggest that these may be suitable for tissue engineering applications.
Colloid and Polymer Science, 2008
We synthesized, thermo-and pH-sensitive gels and tested them as skin extenders. Our aim is the development of copolymer and composite hydrogels that, when implanted under the human skin, swell osmotically and thereby induce skin growth. In the course of the polymerization reaction, we produced copolymers with variable compositions, starting from different acrylic compounds [N-isopropyl-acrylamide (NIPAAm), acrylamide (AAm), and acrylic acid (AAc)]. The mechanical strength and the swelling stability of the gels are enhanced by the addition of fillers [Na-montmorillonite and Namontmorillonites organophilized with alkylammonium ions (C n -m.), n=4, 12, 18]. With this method we synthesized composite hydrogels. We observed that in the case of composites synthesized with the addition of fillers, relatively low filler contents (1-5 wt.%) resulted in more extensive swelling and stronger gel structure. During the experiments, the monomer composition (0/100-100/0 mol% NIPAAm/ AAm or AAc) and the cross-link density (50-1500 mol%) of the gels (M/C ratio) and, in the case of composites, the quality and quantity of fillers are varied. The filler content of composites varies between 1 and 25 wt.%. The extent of swelling and the viscoelastic properties can be manipulated through the ratios of these parameters. In the case of certain copolymer and composite gels, values of desorption enthalpy (ΔH m ) corresponding to the actual water contents were also determined by thermoanalytical measurements (differential scanning calorimetry, DSC). Swelling values determined by gravimetry and enthalpies calculated from DSC measurements were found to be in good correlation. Even in the case of the relatively hydrophobic poly(NIPAAm)based gels, an enthalpy value of 98.41 kJ/mol was obtained, which is twice the value measured in pure water (41.74 kJ/ mol). Evaluation and comparison of the rheological and DSC results also allowed conclusions to be drawn concerning the types of interaction operating among the three components of the system, i.e., the polymer skeleton and the filler and water molecules.
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.
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.
Highly Swellable Hydrogels from Waterborne Poly(Vinylamine-co-Acetamide)
Macromolecular Chemistry and Physics, 2018
primary amines, their polarity, and reactivity render PVAm an attractive candidate for various post polymerization modification and hydrogel formation. In spite of this, there are only few papers on PVAm hydrogels. Kobayashi et al. used a bifunctional epoxide-based crosslinker for the formation of a hydrogel investigating the pH-dependent swelling behavior with swelling ratios up to 2500%; nonetheless, the complete gelation process took 48 h and is not well investigated. [7] In another work Wang et al. showed synthesis of thermo-and pH-responsive microgels with a poly(N-isopropylacrylamide) core and a PVAm shell crosslinked by N, N′-methylenebisacrylamide via emulsion polymerization. [8] In a further study primary amine groups of the PVAm on the surface were exploited to graft a copolymer of acrylic acid, acryloyloxyethyl trimethyl ammonium chloride, and acrylamide onto microgels obtaining thermo-and pH-responsive hydrogels. [9] In another study by this group PVAm was crosslinked with aldehyde functionalized starch to form hydrogel via Schiff base reaction. [10] Furthermore Han et al. produced a hydrogel starting with PNVF. In a concerted reaction the formamide was hydrolyzed with sodium hydroxide solution and the formed amine groups crosslinked with glutaraldehyde. [11] In all these papers the PVAm-based polymers have not been exploited for synthesis of superabsorbent hydrogels (SHs). In general superabsorbent gels are loosely crosslinked 3D polymeric networks mainly of acrylic acid (AA) and/or acrylamide (AM)-based monomers. [12] Typically, free radical polymerization is used for the synthesis of these gels. Depending on the type of crosslinker and crosslinking density a water uptake of 8000 to 80 000% was obtained. [13] Addition of inorganic fillers or further introduction of physical crosslinks could enhance the water uptake to 280 000%. [13a,b,d] SHs used in commercial diapers show a water uptake of 23 800%. Free radical polymerization is a very convenient and handy approach for preparing SHs. However, it is very difficult to control the formation of network structure and the products are inhomogeneous which leads to a decrease in the swelling ability. In this work hydrogels are obtained by polycondensation of two prepolymers-an amine functional linear polymer with a PC-PEG-PC. To adjust the number of amine groups in the polymer chain in the present study NVF was copolymerized with N-vinylacetamide (NVA) in different ratios with subsequent selective hydrolysis of the formamide groups. The presence of amine Superabsorbants Hydrogels consisting of a hydrophilic polymer backbone are attractive candidates for the formation of superabsorbent hydrogels (SHs). Mainly, such hydrogels are prepared via free radical polymerization. Herein, poly(Nvinylamine-coN -vinylacetamide) [P(VAm-co-NVA)] with different amine-toamide ratios are crosslinked with phenyl carbonate telechelic poly(ethylene glycol) (PC-PEG-PC) to form a hydrogel in the presence of a base. The structure property relationship in terms of the amide-to-amine ratio, the carbonate-to-amine ratio, and the base-to-amine ratio is investigated by swelling experiments and rheology. 13 C NMR is used to determine the degree of crosslinking which can further influence the swelling behavior and the mechanical properties of the gels. The maximum swelling ratio of the hydrogels is found to be 97 000% with respect to the dry gel, with a storage modulus of 4 kPa of the as-prepared gel. This swelling behavior of the obtained gels is above the state of the art and has a possibility to be tuned further.
Industrial & Engineering Chemistry Research, 2005
A useful hydrogel for supporting and/or entrapping living microorganisms has been developed by the syntheses of graft copolymers based on vinyl alcohol and styrene, PVOH-g-PS, and through the formation of macro-and microporous structures formed under the slow evaporation of a toluene/dimethyl sulfoxide, DMSO, mixture of solvents. The PVOH-g-PS copolymer was obtained by the methanolysis of the vinyl acetate part of a previously bulk-polymerized poly(vinyl acetate)g-poly(styrene) copolymer, PVAc-g-PS. To produce the so-called PVOH-g-PS hydrogel, polymer films formed by the evaporation of a toluene/DMSO mixture were subjected to different freeze/ thaw cycles in order to crystallize the PVOH part of the copolymer. Calorimetric studies carried out on these types of hydrogels show melting endothermic transitions that correspond to fusion of the PVOH, and the crystallization areas increase with the number of freeze/thaw cycles. The low-vacuum scanning electron microscopy and atomic force microscopy images reveal that the PVOH-g-PS copolymer can form films with homogeneous macro-and micropore size distributions interconnected by a cheese-like structure where the microorganisms can be supported and/or entrapped.