Swelling temperature-sensitive

DC Harsh, SH Gehrke. Controlling the swelling characteristics of temperature-sensitive cellulose ether hydrogels. J Controlled Release 17 175-186, 1991. 

SH Gehrke, LH Lyu, MC Yang. Swelling, shrinking, and solute permeation of temperature-sensitive N-isopropylacrylamide gel. Polym Prepr 30 482-483, 1989. 

Another class of environmentally sensitive materials that are being targeted for use in drug delivery applications is thermally sensitive polymers. This type of hydrogel exhibits temperature-sensitive swelling behavior... 

Poly(A-isopropyl acrylamide) (PNIPAAm) is the most extensively studied temperature-sensitive polymer [10-20]. Crosslinked PNIPAAm exhibits drastic swelling transition at its lower critical solution temperature... 

Applications of responsive gels in biotechnology have also been examined. For example, Dong and Hoffman proposed the use of temperature sensitive hydrogels for the immobilization of enzymes in bioreactors [110]. Enzyme activity can be turned on and off by causing the gel to swell or shrink when shrunken, the enzyme activity is turned off, since the pores are blocked to the substrate. Different applications are possible for this system besides enhanced bioreactor performance, including bioassays. 

To identify the rate limiting steps, we carried out a series of parallel experiments one in which we determined the rate of thermal equilibration of cylindrical temperature-sensitive gels in response to different temperature driving forces and the other in which we determined the rate of swelling or shrinking of identical gel samples under identical conditions. 

Fig. 9. Plot of normalized approach to equilibrium mass against the square root of time for a temperature-sensitive 10 x 4 PNIPAAm gel sheet swelling and shrinking between 10 and 25 °C-Shown are the curve fits to the kinetic data of theory developed from Fick s law of diffusion in a polymer-fixed reference frame [149]. The equilibrium degree of swelling is 17.0 at 10 °C and 11.1 at 25 °C the diffusion coefficients obtained from the curve fits are 2.3 x 10 7 cm2/s for swelling and 3.6 x 10 7 cm2/s for shrinking [121]...

Beltran S, Hooper HH, Blanch HW, Prausnitz JM. Swelling equilibria for ionized temperature-sensitive gels in water and in aqueous salt solutions. J Chem Phys 1990 92 2061-2066. 

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