A-Isopropylacrylamide gel

Coexistence of Phases and the Nature of First-Order Phase Transition in Poly-A-isopropylacrylamide Gels... 

Fig. 5. Poly(A-isopropylacrylamide) gel swelling vs temperature. Circles are data points amt the solid fine is the lattice model prediction with one fitted parameter. (Reprinted with permission from [12], 1990 American Chemical Society)...

Cussler EL (1989) Isolation process using swellable poly(A-isopropylacrylamide) gels. U.S. Pat. 4,863,613... 

Xulu, P.M. Filipcsei, G. Zrinyi, M. Preparation and responsive properties of magnetically soft poly(A-isopropylacrylamide) gels. Macromolecules 2000, 33, 1716-1719. 

Hirotsu S (1993) Coexistence of phases and the nature of l -order phase-transition in poly (A-isopropylacrylamide) gels. Adv Polym Sci 110 1-26 Hoffman AS (1981) A review of the use of radiation plus chemical and biochemical processing treatments to prepare novel biomaterials. Radiat Phys Chem 18 323 Hong Y, Krsko P, Libera M (2004) Protein surface patterning using nanoscale PEG hydrogels. Langmuir 20 11123-11126... 

L.C. Dong and A.S. Hoffman, Thermally reversible hydrogels III. Immobilization of enzymes for feedback reaction control, J. Control. Release, 1986, 4, 223 M. Bayhan and A. Tuncel, Uniform poly(A-isopropylacrylamide) gel beads for immobilization of a-chymotrypsin, J. Appl. Polym. Sci., 1998, 67, 1127. 

INO Inomata, H., Goto, S., Otake, K., and Saito, S., Effect of additives on phase transition of A-isopropylacrylamide gels, Langmuir, 8, 687, 1992. 

Hirotsu, S. (1988). Critical points of the volume phase transition in A-isopropylacrylamide gels. The Journal of Chemical Physics, 88, 427-431. 

Otake K, Inomata H, Konno M, Saito S (1990) Thermal analysis of the volume phase transition with A-isopropylacrylamide gels. Macromolecules 23(l) 283-289 Paschew G (2006) Entwicklung eines hoch aufgeldsten taktilen Displays. Diploma thesis, TU Dresden... 

Takeoka, T. and Watanabe, M. 2003. Template synthesis and optical properties of chameleonic poly (A-isopropylacrylamide) gels using closest-packed self-assembled colloidal silica crystals. Adv. Mater. 

Table 6 Properties of IV-Isopropylacrylamide Gels as a Function of Reaction Timea...

Note 3 An example of covalent polymer gels is nei-poly(A-isopropylacrylamide) swollen in water, which shows volume phase transition during heating. 

The sample used to study the relationship between the volume phase transition and the frictional property is poly( /V-isopropylacrylamide) gel which shows a small discontinuous volume phase transition at 33.6 °C. The sample gel is prepared by free radical polymerization 7.8 g of re-crystallized N-iso-propylacrylamide (main constituent, Kodak), 0.133 g lV,iV -methylenebis-acrylamide (cross-linker, Bio-Rad), 240 ml tetramethylenediamine (accelerator, Bio-Rad), and 40 mg ammonium persulfate (initiator, Mallinckrodt) are dissolved in distilled water (100 ml) at 0°C. The gel mold is immersed in the pre-gel solution and then degassed for 40 min at 0°C. The temperature is raised to 20.0 °C after this treatment to initiate the gelation reaction. The sample gel thus obtained is homogeneous and transparent, at least by visual inspection. 

In spite of the constant density of the gel, the friction of the poly(N-isopropylacrylamide) gel reversibly decreases by three orders of magnitude and appears to diminish as the gel approaches a certain temperature. This phenomenon should be universal and may be observed in any gel under optimal experimental conditions of the solvent composition and the temperature because the unique parameter describing the friction is the correlation length which tends to diverge in the vicinity of the volume phase transition point of gels. The exponent v for the correlation length obtained from the frictional experiment is far from the theoretical value. It will, therefore, be important to study a poly(N-isopropylacrylamide) gel prepared at the critical isochore where the frictional property of gel may be governed by the critical density fluctuations of the gel. 

Several attempts have been made to construct stimuli-responsive polymer solution and gel systems which undergo isothermal phase transitions by external stimulation, such as photons or chemicals. Aqueous solutions of poly(A -isopropylacrylamide) having photoisomerizable chromophores or host molecules in the pendant groups showed reversible phase separations by photoirradiation or by the addition of specific metal or ammonium ions. The gels made of the polymers also underwent photostimulated or chemical-induced volume phase transitions. 

Our alternative soy protein isolate process utilizing the swellable gel technology is shown in Fig. 9. Instead of precipitating the protein, we subject the mother liquor to a series of five poly(N-isopropylacrylamide) gel treatments to concentrate and purify the protein stream. In the first gel stage, the mother liquor is contacted with collapsed gel at 5 °C. Approximately 40% of the water in the mother liquor is absorbed by the gel as it swells. The swollen gel is then separated from the retentate in a centrifuge. This retentate is diluted with water... 

This function increases monotonically with network density < ) and has a large Maxwell s loop for the large ionization parameter f. The swelling curves of N-isopropylacrylamide gels at low ionization were essentially well described by this equation [10]. 

H. Kawasaki, S. Sasaki, and H. Maeda, Effects of the gel size on the volume phase transition of poly(N-isopropylacrylamide) gels A calorimetric study, Langmuir 14(4), 773-776 (1998). 

Y. Suzuki, N. Suzuki, Y. Takasu, and I. Nishio, A study on the structure of water in an aqueous solution by solvent effect on a volume phase transition of N-isopropylacrylamide gel and low-frequency Raman spectroscopy, J. Chem. Phys. 107(15), 5890-5897 (1997). 

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