Polystyrene in cyclopentane

Experimental support for the suggestion that depleted surface layers result in attractive forces (at T 0) has come from recent experiments (J.K. and Y.A., submitted) where mica surfaces partially covered by polystyrene in cyclopentane above the 0-temper-ature show a clear mutual attraction, which disappears when full surface coverage by the polymer is attained. 

For polystyrene in cyclopentane, one predicts that there should be two theta-temperatures, at 22 and 150 respectively. In the intermediate temperature range, cyclopentane should be a good solvent for PS. 

Note that, as reported in Table 6.2, latices stabilized either by poly(a-methyl styrene) in -butyl chloride or by polystyrene in cyclopentane flocculated both on heating and on cooling. Moreover, the UCFT in nonaqueous systems tends to occur as the critical temperature of-the dispersion medium is approached. In aqueous systems, the UCFT can occur well below the critical temperature. 

Figure 5. of [top to bottom] 262, 657, and 861 kDa polystyrenes in cyclopentane near the theta temperature, as obtained with FRS by Deschamps and Leger [79], and fits to stretched exponentials. 

Liquid-liquid equilibrium data of polystyrene in cyclopentane and cyclohexane Data extract from Landolt-Bornstein VIII/6D3 Polymers, Polymer Solutions, Physical Properties and their Relations I (Thermodynamic Properties Equilibria of Ternary Polymer Solutions) ... 

Figure 4.24 Interaction energy between mica surfaces in the presence of a solution of polystyrene in cyclopentane. In the absence of polymer molecules (a), there is a simple van der Waals attraction. At low surface coverage bridging (lower inset) dominates. As more polymer adsorbs (b) and (c), the steric repulsion counteracts the attraction until at high surface coverage (d), the interaction is repulsive at all separations. (From Ref. 43.)...

Cited by (15) as B. Nystrom, J. Roots, and R. Bergman. Sedimentation velocity measurements close to the upper critical solution temperature and at Theta-conditions polystyrene in cyclopentane over a large concentration interval. Polymer, 20 (1979), 157-161. 

W. Brown. Dynamical properties of high molecular weight polystyrene in cyclopentane at the temperature. Macromolecules, 19 (1986), 3006-3008. 

Cogan and Gast [61] presented dynamic light scattering (DLS) data of polystyrene-polyoxyethylene diblock copolymers in cyclopentane in the presence... 

Fig. 18. Interaction potential energy (converted to a potential between planes) vs. separation between two mica surfaces bearing adsorbed polystyrene (2 x 106 g/mol) in cyclopentane, a good solvent (Almog and Klein, 1985). Full circles, open circles, triangles, and squares correspond to increasing adsorbed amounts achieved by incubating the surfaces at close separation for increasing intervals of time.

Experimental observation of selective flocculation. Croucher and Hair (1980a) have demonstrated the phenomenon of selective flocculation in mixtures of heterosterically stabilized dispersions. They prepared particles of poly(vinyl acetate) stabilized by polystyrene and polyacrylonitrile particles stabilized by polyisobutylene, both in cyclopentane. The value of X23 for polystyrene and polyisobutylene is known to be positive (Hyde and Tanner, 1968), corresponding to mutually incompatible polymers. The poly(vinyl acetate) particles stabilized by polystyrene exhibited both upper and lower critical flocculation temperatures whereas the polyisobutylene stabilized particles only flocculated on heating. 

When a mixture of the two different types of particles dispersed in cyclopentane was cooled to the lower critical flocculation temperature (280 K) of the poly(vinyl acetate) particles stabilized by polystyrene, those... 

Already in Figure 6-2 we have shown the data of Vidakovic et al. [28] for s c) of polystyrene in cyclohexane at 9. Interestingly, they do not agree with the data of Roots and Nystrom [29] for polystyrene in another 9 solvent cyclopentane... 

Figure 3.36. Normal and shear forces for brush layers (in toluene) and adsorbed layers (in cyclopentane) of polystyrene. The solid line is the shear force for an adsorbed layer the shear force for a brush was zero. The long dashed line is the normal force for an adsorbed layer and the short dashed line is the normal force for a brush. After Klein etal. (1995).

Determine for polystyrene molecules in cyclopentane given that the degree of polymerization of polystyrene is 2 x 10. ... 

For short chains, peu ticularly in cyclopentane, where the 4kik-i term in eq 7 is significant, lN(t) decays as a sum of two exponential terms. Under these circumstances, values of ks and k>i can also be determined. For Py-polystyrene-Py at 34.6 these values are 3.6 x 10 sec"i and 1.8 x 10 sec , respectively, independent of chain length, within experimental error. The former is very sensitive to temperature (Ea = 11 kcal/mol) whereas ke depends only weakly upon t nperature (Ea = 1.6 kcal/mol). From this data, an apparent binding energy of -AHo = 8 kcal/mol can be calculated for the intramolecular pyrene excimer. This compares to a value of 8 kcal/mol reported by Birks (22) for bimolecular excimer formation from pyrene itself in cyclohexane. 

Figure 8. A plot of the critical exponent from the expression - for DMA-polystyrene-Py samples of M = 3000 to 28000 measured in cyclopentane at various temperatures. The error bars represent one standard deviation.

Figure 3 Temperature dependence of A 2 in the vicinity of the theta temperatures u and l for four polystyrenes (M X 10 = 0.16,0.41,0.86 and 1.97) in cyclopentane. The initial slopes of the plots give By (left) and Bl (right) (reproduced by permission of Wiley, from J. Polym, ScL, Part B Polym. Phys. 1987, 25, 681)...

Figure 5 Bilogarithmic plot of (JTcM/R(0,c) - 1) vs. Me for two polystyrenes (A = 0.86x 10 filled circles M, = 2-20 X 10, open circles) in cyclopentane at 0u (pips up) and 0l (pips down). Squares represent osmotic data for polystyrene (A n = 84 X 10 ) in benzene at 0 (24.5 °C). The lines in the plot have a slope of two in conformity with the quadratic form of...

Figure 11 Relative viscosity tjj. = rj/rj as a function of 02 w for polystyrene solutions. Open circles are for solutions in cyclopentane at l = 8.62 x 10 (pips right), 2.0 x 10 (pips down). Triangles indicate solutions (M = 2.0 x 10 ) in...

Figure 11.10 Approaching force versus distance curves between curved mica surfaces in 15 mg polystyrene dissolved in cyclopentane. Curves were recorded 12, 15, and 31 h after immersing the mica surfaces in the solution. (Adapted from Ref [1398].)...

The styrene monomer first may be polymerized to about 65% conversion in the absence of water, and then the blowing agent (cyclopentane) may be added with additional peroxide. This solution is suspended in water in the presence of potato starch, and the polymerization is finished (74). By another modification a styrene solution of waste polystyrene and peroxide is suspended by poly (vinyl alcohol) in water, and pentane is added to the suspension after the solids content of the oil phase is greater than 70% (133). Polystyrene particles may also be suspended in water by a mixture of poly (vinyl alcohol) and a phenyl sulfonate and then a mixture of equal parts of pentane and catalyzed styrene (8% each on polymer) is diffused into the polymer. The temperature is elevated, and the polymerization is completed (23). 

Ishizawa, M. Kuwahara, N. Nakata, M. Nagayama, W. Kaneko, M., "Pressure Dependence of Upper Critical Solution Temperatures in the System Polystyrene-Cyclopentane," Macromolecules, 11, 871 (1978). 

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