Hydrogels polyelectrolyte

In most cases, the swelling of polyelectrolyte hydrogels depends only on ionic strength of the solution but not on the size and nature of the ions [101]. Therefore, the ionic suppression curves similar to those of Fig. 2 and 3 are to some extent universal and allow to predict quantitatively the swelling of hydrogels for practically any ionic situation. 

In contrast to polyelectrolyte hydrogels, nonionic ones are almost insensitive to the ionic composition of the medium. In particular, the equilibrium swelling degree of a charge-free PAAm gel practically does not depend on the Cu2 + concentration (Fig. 4, curve 0) nor on the concentration of several other ions or on the pH value [101]. 

The effect of the network density on the polyelectrolyte hydrogel elasticity can be understood taking into account the fact that the elastic modulus is closely connected with the swelling pressure (see, for example, Refs. [20, 115]) ... 

Responsive polyelectrolyte hydrogels that have been used for controlled release systems include gels which are hydrophobic in their neutral state... 

Electrical Polyelectrolyte hydrogel Apply electric field, membrane charging, electrophoresis of charged drug, change in swelling, release of drug... 

Varshosaz, J. Falamarzian, M. Drug diffusion mechanisms through pH-sensitive hydrophobic/polyelectrolyte hydrogel membranes. Eur. J. Pharm. Biopharm. 2001, 51, 235-240. 

Inoue T., Chen G., Nakamae K., Hoffman A. S. A hydrophobically modified bioadhesive polyelectrolyte hydrogel for drug delivery. J. Controlled Release 1997 49 167-176. 

Flory PJ (1953) Principles of polymer chemistry. Cornell University Press, Ithaca, NY Ciinther M, Cerlach C, Wallmersperger T (2007) Modeling of nonlinear effects in pH-sensors based on polyelectrolytic hydrogels. In Bar-Cohen Y (ed) Proceedings of the SPIE Electroactive Polymer Actuators and Devices, vol. 6524. p 652416f... 

Keywords Piezoresistive sensor Biochemical sensor Polyelectrolytic hydrogel pH-sensitive Temperature sensitive Swelling behaviour... 

Andreeva AS, Philippova OE, Khokhlov AR, Islamov AK, Kuklin AI (2005) Effect of the mobility of charged units on the microphase separation in amphiphilic polyelectrolyte hydrogels. Langmuir 21 1216-1222. doi 10.1021/la0478999... 

Due to their sensitivity to electric stimulus, polyelectrolyte hydrogels have been investigated for their potential applications for electrically controlled drug delivery systems, electro-chemical actuators and sensors, as well as muscular actuators (Kaewpirom and Boonsang 2006). The set up for electrostimulation of... 

Polyelectrolyte hydrogels contain fixed, ionizable pendant groups, which interact electrostatically with each other and with microions in the interstitial... 

Certain polyelectrolyte hydrogels display first-order volume phase transitions, with hysteresis, in response to external stimuli 2,7). Hydrophobic polyelectrolyte hydrogels, in particular, may undergo discrete transitions in response to changes in external pH. Such hydrogels have been considered as chemically-sensitive mechanical switches 8). 

Various polyelectrolyte hydrogels have been prepared with natural polyanions such as xanthan [250], hyaluronic acid [251], alginate [252], collagen [253], pectin [254], and gelatin [255]. 

Shang J, Shao Z, Chtm X (2008) Electrical behavior of a natural polyelectrolyte hydrogel chitosan/carboxymethylcellulose hydrogel. Biomacromolecules 9 1208-1213... 

Lowe, T. L., Virtanen, J. and Tenhu, H., Interactions of drugs and spin probes with hydrophobically modified polyelectrolyte hydrogels based on N-isopropylacrylamide. Polymer, 40, 2595-2603 (1999). 

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