Acrylic acid, hydrogels from

Table 16 Swelling values for poly(W-vinyl pyrrolidone/starch-g-acrylic acid) hydrogel in various pH media 7 ( °Co)-irradiation dose 50 kGy (dose rate 1.2 kGy.h" ). The data were taken from [08E1].

Gels can be made from a number of polymers, including poly[acrylamide-5 fflf-(acrylic acid)], poly(vinyl acetate), poly(dimethyl sUoxane), and polyiso-cyanurates. The poly[acrylamide-5 tor-(acrylic acid)] hydrogels can be made to swell up to 20,000 times, v/v. Thermoreversible gels can be prepared in organic solvents from polyethylene and i-polystyrene, both of which crystallize on cooling but go back in solution on heating. 

Figure 1.7 Working energy of polyfvinyl alcohol)/poly(acrylic acid) hydrogels, cross-linked under different conditions oftemperature/time, versus applied stress (Reprinted with permission from Arndt, K., Richter, A., Ludwig, S. et al. Poly(vinyl alcohol)/poly(acrylic acid) hydrogels FT-IR spectroscopic characterization of crosslinking reaction and work at transition point, Acta Polymerica, 50, 383-90, Copyright (1999) Wiley-VCH Verlag GmbH).

One-to-one random copolymers of acrylic acid with either hydroxyethyl acrylate (a hydrogel model) or methyl acrylate failed to protect insulin from release under gastric conditions (Figure 6). In the case of the hydrogel, the expected swelling due to exposure to water occurred, releasing insulin. The behavior of the ester copolymer led to the prediction that there should be no more than about four carbon atoms per carboxylic acid group in a repeat unit of the polymers. We have not been able to disprove this hypothesis thus far. 

Shen Z, Duan H, Frey H (2007) Water-soluble fluorescent ag nanoclusters obtained from multiarm star poly(acrylic acid) as molecular hydrogel templates. Adv Mater 19 349-352... 

An anesthetic drug, Richlocaine, developed jointly by scientists from Kazakhstan and Russia, and commercially available biologically active substances bovine serum albumin, lysozyme, and catalase were used. Hydrogels of acrylamide and acrylic acid copolymer(AA-AAc),poly(N-isopropylacrylamide)(PNIPA),N-isopropylacrylamide and acrylic acid copolymer (NlPA-AAc), N-isopropylacrylamide and 2-(acrylamido)-2-propanesulfonic acid copolymer (NIPA-APSA) were synthesized. Diffusion parameters of bioactive substances into hydrogel matrices were calculated using Eq. (19.1) ... 

Tatykhanova GS, Kudaibergenov SE. (2008) Controlled release of local anesthetic drug richlocaine from the pH- and thermosensitive hydrogels-copolymers of N-isopropylacrilamide and acrylic acid. New smart materials via metal mediated macromolecular engineering from complex to nanostructures. Antalya, Turkey, 1-12 September 2008. 

The preparation of monodisperse hydrogel microspheres, such as poly-acrylam-ide-co-acrylic acid, poly(N-isopropylacrylamide-co-acrylic acid), has been performed for drug devices thanks to their biocompatibility [77, 79]. The average diameters of the microspheres were dependent on the pore sizes (from 0.33 to 1.70pm) of SPG membranes used in the preparation procedure. 

Hydrogel valves were also created within microfluidic channels to provide fluid control (see Figure 3.28). The swelling and contraction provide valve-close and valve-open actuation, respectively, due to chemical stimuli (e.g., pH change). To increase the mechanical stability, the hydrogel was formed around prefabricated posts in the channel. Since the thickness of hydrogel is reduced, the response time to chemical stimuli was also reduced to 8 s (from 130 s). When acrylic acid... 

Ultrathin hydrogels are prepared from poly(vinyl amine-co-N-vinylformamide) and poly(acrylic acid) using EDC. Such soluble functionalized nanotube/PVA composites are used as an electrode for glucose sensing. ... 

Katime, L Novoa, R. Zuluaga, F. Swelling kinetics and release studies of theophylline and aminophylline from acrylic acid/n-alkyl methacrylate hydrogels. Eur. Polym. J. 2001, 37, 1465-1471. 

Fig. 5 Hydrogel-coated gold nanoparticles prepared by surfactant-free emulsion polymerization. After coating oleic acids on the gold nanoparticle, polymerization was carried out in the presence of A-isopropylacrylamide, acrylic acid, and ammonium persulfate (initiator). The size of resulting nanoparticles was in the range of 100-230 nm. (Modified from Ref l)...

Such a substrate effect is observed in a wide variety of hydrogels prepared from water-soluble vinyl monomers (e.g., the sodium salt of styrene sulfonate, acrylic acid, and acrlyamide), and on various hydrophobic substrates, such as Teflon, polyethylene, polypropylene, PVC, and polymethyl methylacrylate (PMMA) [52]. This template effect is due to retardation of the radical polymerization near the rough and hydrophobic substrates that trap oxygen at the solid surface [82]. 

Stoy and co-workers (2) reported an approach that used alternative materials and involved the partial hydrolysis of poly(acrylonitrile) to form a complex structure that was presumed to involve sequences of unhydrolyzed poly(acrylonitrile) interspersed with acrylamide and acrylic acid sequences that resulted from hydrolyzed nitrile groups. Crystallites of unhydrolyzed poly(acrylonitrile) provided the physical cross-link domains within a matrix of the water-swellable portions of the structure. The tensile properties for such materials were considerably enhanced in comparison to the conventional covalently cross-linked hydrogels, and the absence of cross-links allowed processing under certain conditions. 

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