Swelling curve temperature

Fig. 5. Theoretical swelling curves of gels. The reduced temperature, x, is plotted as a function of the degree of swelling, V/V . f denotes the number of counter ions per sub-polymer chain between two neighboring crosslinks...

Fig. 24a-c. a. Equilibrium radius of a NIPA gel sphere as a function of temperature. At lower temperatures the gel is swollen and at higher temperatures it is shrunken. At about 34 °C the swelling curve becomes infinitely sharp, which corresponds to the critical point, b. Relaxation time of gel volume change in response to a temperature jump, as a function of temperature, c. Thermal expansion coefficient, the relative radius change per temperature increment, also diverges at the critical point... 

Fig. 1. Equilibrium swelling curves of NIPA gel in a DMSO/water mixture plotted as a function of temperature. The concentrations of DMSO are O 0% 3% A 5% A7%...

Swelling curves of two neutral NIPA gels with different initial polymer concentration crosslinking density Nc/V0 are shown in Fig. 3 [20], One sample (call it gel A) had 0 = 0.075 and Nc/V0 = 1.02 x 1022, which undergoes a slightly discontinuous transition as shown in Fig. 3a, while the other (gel B) had <))0 = 0.114 and Nc/V0 = 2.40 x 1022, which undergoes a continuous transition as shown in Fig. 3b. In the former sample, the coexistence of the swollen and the shrunken phases was observed within 0.05 °C of the transition temperature, which is concrete evidence that the transition is discontinuous. On the other hand, the latter sample was homogeneous, at least by visual inspection,... 

Below, I will first describe the observation on thin cylinders because the phase coexistence can most clearly be observed in these samples and, moreover, samples of this shape are most frequently used in various experiments. The results of the observation are depicted schematically in Fig. 12. As the temperature was increased from the swollen phase, the sample gradually shrunk following the swelling curve (Fig. 7) and the onset of the transition region was manifested by the appearance of a nucleus of the high-temperature (shrunken) phase at the end of the cylinder. We denote this temperature as Tt. As long as... 

The swelling behavior of poly(N-isopropylacrylamide) has been studied extensively [18,19]. It has been shown that this gel has a lower critical point due to the hydrophobic interaction. Such a swelling curve is schematically illustrated in Fig. 9. The gel is swollen at a lower temperature and collapses at a higher temperature if the sample gel is allowed to swell freely in water. The volume of the gel changes discontinuously at 33.6°C. The swelling curves obtained in this way correspond to the isobar at zero osmotic pressure. On the other hand, the friction coefficient is measured along the isochore, which is given in Fig. 9,... 

Fig. 9. Volume changes of a PNIPAM gel containing pendant triphenyknethane leuconitrile groups as a function of temperature. Filled circles show the swelling of the gel without UV irradiation. Open circles denote the swelling curve on U V irradiation when raising the temperature. Half filled circles are for the curve on UV irradiation when lowering the temperature...

Fig.3a,b. Diameter of N-isopropylacrylamide-chlorophyllin copolymer gel as a function of temperature. (a) IBIS system, (b) SBIS system. Effect of the CH concentration on the swelling curves depends strongly on the BIS concentration... 

Fig. 19. Swelling curves of a 1 BIS gel the transition temperature of which is higher than that shown in Fig. 17(a), and their calculated curves for low stress values...

Typical examples of the molality dependence of the swelling curves are shown in Fig. 25 where the swelling curves of NIP A gels immersed in four simple aqueous inorganic salt solutions are demonstrated for various molalities. In each case, with increasing salt molality, the transition temperature shifts to the lower... 

Fig. 28. Classification of salt effects on the swelling curve. Until now four types of effect have been observed, each of which has different combination of increment or decrement of the transition temperature, induction or reduction of the transition discontinuity, and their combinations...

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