IPN hydrogels

In this work, we generated new PMAA/PNIPAAm IPN hydrogels with both pH and temperature sensitivities by the interpenetration of the pH-sensitive and temperature-sensitive polymer networks. 

The IPN hydrogels were cut into 10-mm-diameter disks and dried under vacuum at 37°C. The dried volumes were calculated using a buoyancy technique. Dry disks of each type were placed in 100 mL of buffer solutions... 

DSC were conducted on PMAA/PNIPAAm IPN hydrogels swollen at different pH values. The results show that the difference in pH has great influence on the LCST transitions of the IPN hydrogels, as shown in Figure 5. 

At pH 4.3, there is no significant transition detected around 32°C. Transition temperatures are detected and increase as pH increases. This is because, at low pH, the aggregation of PMAA decreases the mobility of the PNIPAAm network as well as the water uptake of the IPN, resulting in drastically lowering the temperature sensitivity of the IPN hydrogel. However, at higher pH value, the swollen PMAA allows the PNIPAAm to have a higher mobility, which makes the IPN more temperature sensitive. 

Qui, Y., and K. Park. 2003. Superporous IPN hydrogels having enhanced mechanical properties. AAPS Pharm Sci Technol 4 406... 

An interesting result with respect to applications obtained with the IPN hydrogels is that these are two- phase systems (two glass transition temperatures), with the hydrophilic domains behaving essentially like the pure hydrophilic component.6,7,9 Thus, the two basic functions of these IPN hydrogels with respect to applications, namely hydrophilicity and mechanical stability, are separately taken over by the two IPN components, the hydrophilic and hydrophobic domains, respectively. Figure 1 shows TSDC and DMA results for the water content dependence of the a relaxation (dynamic glass transition) of PHEA in sequential IPNS prepared from PHEA and poly(ethyl methacrylate) (PEMA) as the hydrophobic component.9 In these IPNs a porous PEMA network was prepared first, and PHEA was then polymerized in the pores. In addition to the... 

Chitin is known to be biodegradable, biocompatible, and nontoxic. It is used in dmg delivery and bio medical applications. It also used in the purification of water especially for the absorption of toxic dyes. Chitin has limited solubility in solvents but chitosan is readily soluble in acidic aqueous solutions and has more tendency to be chemically modified. Chitosan can readily be spun into fibers, cast into films, or precipitated in a variety of micromorphologies from acidic solutions. Min and Kim have reported on the adsorption of acid dyes from wastewater using composites of PAN/chitosan [52]. Shin et al. has reported on copolymers composed of PVA and poly dimethyl siloxanes cross-linked with chitosan to prepare semi IPN hydrogels for application as biomedical materials... 

FIGU RE 10.9 Schematic structures for preparing semi- and full-IPN hydrogels with alginate and PNIPAAm. 

Chivukula, P, Dusek, K., Wang, D. et al. 2006. Synthesis and characterization of novel aromatic azo hond-containing pH-sensitive and hydrolytically cleavable IPN hydrogels. Biomaterials. 27 1140-1151. 

Mohamadnia, Z., Zohuriaan-Mehr, A.J., Kabiri, K. et al. 2007. pH-sensitive IPN hydrogel beads of carrageenan-alginate controlled drug delivery. J Bioact Compat Polym. 22 342-356. 

Palapparambil, S. G., Debajyoti, R., Prafiilla Kumar, S. (2010). Designing of silver nanoparticles in gum arabic based semi-IPN hydrogel. 

Cellulose and its derivatives have also been used to prepare interpenetrating polymer network (IPN) hydrogels. In the case of using cellulose, both regenerated... 

Kim, S. Y, H. S. Shin, Y. M. Lee, and C. N. Jeong. 1999. Properties of electrorespon-sive polyfvinyl alcohol)/poly(acrylic acid) IPN hydrogels under an electric stimulus. Journal of Applied Polymer Science 73 1675-1683. 

Zhao, S., Cao, M., Li, H., Li, L., Xu, W. Synthesis and characterization of thermosensitive semi-ipn hydrogels based on poly(ethylene glycol)-co-poly(epsilon-caprolactone) macromer, n-isopropylacrylamide, and sodium alginate. Carbohydrate Research 345, 425 31 (2010)... 

FIGURE 10.8 Lipid microsphere release from gelatin/dextran IPN hydrogels in phosphate buffer at 37 °C open circle, 5 U/mL a-chymotrypsin -1- 0.5 U/mL dextranase open triangle, 5 U/mL a-chymotrypsin open square, 0.5 U/mL dextranase. Reproduced from Ref. [38] with permission. Copyright 1998 Elsevier. 

Ma, J.T., L.R. Liu, X.J. Yang and KD. Yao, Bending behavior of gelatin/poly(hydroxy ethyl methacrylate) IPN hydrogel under electric stimulus, Joimw/ of Applied Polymer Science, 56 (1995) 73-77. 

Z. Mohamadnia, M. J. Zohuriaan-Mehr, K. Kabiri, A. Jamshidi and H. Mobedi, pH-Sensitive IPN Hydrogel Beads of Carrageenan-Alginate for Controlled Drug Delivery /. Bioact. Compat. Polym. 22, 342-356 (2007). 

Pescosolido, L., Schuurman, W., Malda, J., Matricardi, P., AUiaique, F., Coviello, T., Van Weeren, P.R., Dhert, W.J.A., Hennink, W.E., Vermonden, T., 2011. Hyaluronic acid and dextran-based semi-IPN hydrogels as biomaterials for bioprinting. Biomacromolecules 12, 1831-1838. 

Journal of Applied Polymer Science 74, No.7, 14th Nov. 1999, p. 1752-61 DRUG RELEASE BEHAVIOR OF ELECTRICAL RESPONSIVE POLY(VINYL ALCOHOL)/ POLY(ACRYLIC ACID) IPN HYDROGELS UNDER AN ELECTRIC STIMULUS So Yeon Kim Young Moo Lee Hanyang,University... 

---