Acrylamide-HEMA copolymers

SCL Nonwater-containing SCL Water-containing SCL Water content < 40 % Water content 40-60 % Water content > 60 % Silicone-type elastomers Acrylic-type elastomers Homopolymers or copolymers of 2-hydroxyethyl methacrylate (HEMA) Copolymers of HEMA, N-vinyl pyrrolidone (NVP), methacrylic acid (MA) and MAA Copolymers mainly from MMA and glycerol methacrylate (GMA) Other Copolymers mainly from MMA, NVP, acrylamide (AAm)... 

Shukla SP, Devi S (2005) Covalent coupling of peroxidase to a copolymer of acrylamide (AAm)-2-hydroxyethyl methaacrylate (HEMA) and its use in phenol oxidation. Process Biochem 40 147-154... 

Most research into the study of dispersion polymerization involves common vinyl monomers such as styrene, (meth)acrylates, and their copolymers with stabilizers like polyvinylpyrrolidone (PVP) [33-40], poly(acrylic acid) (PAA) [18,41],poly(methacrylicacid) [42],or hydroxypropylcellulose (HPC) [43,44] in polar media (usually alcohols). However, dispersion polymerization is also used widely to prepare functional microspheres in different media [45, 46]. Some recent examples of these preparations include the (co-)polymerization of 2-hydroxyethyl methacrylate (HEMA) [47,48],4-vinylpyridine (4VP) [49], glycidyl methacrylate (GMA) [50-53], acrylamide (AAm) [54, 55], chloro-methylstyrene (CMS) [56, 57], vinylpyrrolidone (VPy) [58], Boc-p-amino-styrene (Boc-AMST) [59],andAT-vinylcarbazole (NVC) [60] (Table 1). Dispersion polymerization is usually carried out in organic liquids such as alcohols and cyclohexane, or mixed solvent-nonsolvents such as 2-butanol-toluene, alcohol-toluene, DMF-toluene, DMF-methanol, and ethanol-DMSO. In addition to conventional PVP, PAA, and PHC as dispersant, poly(vinyl methyl ether) (PVME) [54], partially hydrolyzed poly(vinyl alcohol) (hydrolysis=35%) [61], and poly(2-(dimethylamino)ethyl methacrylate-fo-butyl methacrylate)... 

Block copolymers with hydroxyl segments were prepared by various ways An example utilizes the copper-catalyzed sequential copolymerizations of nBA and 2-[(trimethylsilyl)oxy]ethyl acrylate by the macroinitiator method into B-31 to B-33. The copolymers were then hydrolyzed into amphiphilic forms by deprotection of the silyl groups.313 A direct chain-extension reaction of polystyrene and PMMA with HEMA also afforded similar block copolymers with hydroxyl segments (B-34 and B-35).241-243 In block polymer B-36, a hydroxy-functionalized acrylamide provides a hydrophilic segment.117 Block copolymers of styrene and p-acetoxystyrene (B-37 to B-39), prepared by iron... 

YNTHETIC HYDROGEL POLYMERS, first introduced in the early 1960s, made a major impact, initially in the soft contact lens field, and more recently in other biomedical or specialty applications. The first synthetic poly(2-hy-droxyethyl methacrylate) [poly(HEMA)] hydrogel developed by Wichterle (i) remains very important, as do its copolymers with monomers such as N-vinyl-2-pyrrolidinone, acrylic and methacrylic acids, glycerol methacrylate, various acrylamides, and alkoxyalkyl methacrylates. 

IPNs and gradient IPNs based on polyether-urethane-urea (PEUU) block copolymers and acrylamide, 2-hydroxyethyl methacrylate (HEMA), or N-vinyl-2-pyrrolidone. Intended for biomedical uses, such compositions created high-strength, water-absorbing hydrogel surfaces showing good blood compatibility. 

G. C. Berry and M. Dror, Modification of Polyurethanes by Interpenetrating Polymer Network Formation with Hydrogels, Am. Chem. Soc. Div. Org. Coat. Plast. Chem. Pap. 38(1), 465 (1978). Polyether-urethane-urea block copolymers with crosslinked HEMA, NVP, or acrylamide. IPNs and gradient IPNs for biomedical purposes. Strength, water swellability, and good blood compatibility. 

All SCL basically consist of hydrophilic polymers that maintain then-gel structure, with the ability to swell and not dissolve by intermolecular crosslinking. Therefore, natural polymers, such as agarose and gelatin, are potential candidates for its material. However, currently commercially available SCL are made only of copolymers of methacrylic acid derivatives, mainly PHEMA, and several other monomers because of stability and safety concerns. Lenses with a water content of 30-40 % are made mostly of PHEMA and those with water contents of70-80 % are made of copolymers ofN-vinyl pyrrolidone (NVP), acrylamide (AAm), HEMA, and methacrylic acid (MA). There are also poly(vinyl alcohol) derivatives. Table 2 shows the names and chemical structures of various SCL components [6]. 

Other biocompatible hydrogels include the polyacrylamides. These are chemically and physically related to PHEMA [57,58]. Copolymers of HEMA with acrylamide and methacrylamide have been evaluated for swelling and mechanical behavior by Dusek and Janacek [59]. Numerous acrylamides have been studied for bioapplicability [60,61], drug delivery systems [62,63], as well as fundamental behavior [64-67]. 

Fig. 5-2. Molecular structures of some of the most commonly used polymer systems. (A) Polystyrene, a copolymer of styrene and divinylbenzene, (B) polyacrylamide, a copolymer of acrylamide and methylenebisacrylamide, (C) HEMA, a copolymer of ethylene glycol methacrylate and bisethylene glycol methacrylate, (D) cross-linked dextran, (E) agarose, (F) cellulose.

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