Poly hydrogel networks

Pharmaceutical grade poly(ethylene glycols) are poly(ethylene oxides) with terminal hydroxyl groups and have been approved by the E.D.A. and listed in both the United States Pharmacopoeia and Martindale under Macrogols for use as ointment and suppository bases (4J. Poly(ethylene glycol) can be chemically cross-linked retaining the hydrophilic nature of the PEO backbone in an infinite hydrogel network which will imbibe water and swell but not... 

CP composites of both poly(vinyl alcohol) (PVA) [83-88] and poly(ethylene glycol) (PEG) [87,89,90] have been fabricated by both chemical and electrochemical polymerization of either monomer solution loaded or dispersed into hydrogel networks. Li et al. reported that tetraethylammonium perchlorate (TEAP) doped PPy-PVA composite was more hydrophilic than PPy/TEAP film and showed less fibrinogen adsorption on the surface than the CP control film. The PPY-PVA composite maintained intrinsic conductivity of PPy/TEAP film (7 S cm ) and the porous structure of the composite promoted neural cell attachment and spreading in the model clonal line, PC 12 [86]. 

Chatteiji, P.R., Cross-link dimensions in gelatin-poly(acrylamide) interpenetrating hydrogel networks. Macromolecules. 24 (1991) 4214-4215. 

In the above cases, the CNTs were physically entrapped in the hydrogels. The covalent chemistry is an alternative method for obtaining a stable attachment between CNTs and the crosslinked hydrogel. Carboxyl-functionalized SWNTs were functionalized with poly (ethylene glycol) methacrylate (Saez-Martinez et al., 2011) or polyethyleneimine (PEI Homenick et al., 2010) to obtain reactive functionalities on the nanotube surface. Afterward, CNTs were covalently bound through their reactive moieties to a hydrogel network by copolymerization or condensation... 

Sahiner, N., 2006. In situ metal particle preparation in cross-linked poly(2-acrylamido-2-methyl-1-propansulfonic acid) hydrogel networks. Colloid Polymer Science 285, 283—292. 

Vimala, K., Samha Sivudu, K., Murali Mohan, Y., Sreedhar, B., Mohana Raju, K., 2009. Controlled silver nanoparticles synthesis in semi-hydrogel networks of poly(acrylamide) and carbohydrates a rational methodology for antibacterial application. Carbohydrates Polymer 75, 463-471. 

The same principles that used to form a crosslinking network can be applied to IPN systems. For instance, IPN can be prepared initiating polymerization of a monomer in an existing polymer network. The first hydrogel network was composed of crosslinked poly(oxyethylene). The secondary polymerization was taken place in a mixture of acrylic acid, crosslinker and initiator with the poly(oxyeth-ylene) soaked in it, resulting in interpenetrating pH-sensitive networks of poly(oxyethylene) and PA A [64]. IPN can also be formed simultaneously using two different polymerizations mechanisms such as condensation and free radical polymerizations [65]. If linear polymer penetrate on a molecular scale of cross-linked polymer network, a semi-lPN is formed [66]. 

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