Polystyrene/cyclohexanol

Using the above-mentioned methods to measure phase curves, the following results are obtained for binary systems of interest. Figure 1.1.4 shows the result for polystyrene/cyclohexanol system, which has been a subject of early phase separation kinetics studies. 

Fig. 1.1.4 Phase diagram-related results for polystyrene/cyclohexanol system...

Phase separation phenomena of polymer solutions have been studied, and they were found to be relevant to membrane formation and to the study of the FRRPP process. Phase separation has been effected by removal of thermal energy from the homogeneous polymer solution. The polystyrene/cyclohexanol system is investigated. The final structure of these phase separated systems has been found to be a strong function of the quenching time. As processing time increases a shift from a highly interconnected open cell stmcture to a closed cell structure has been... 

The polymer used in the thermal inversion process of making membranes was initially dissolved and maintained at a temperature above the critical point of the binary system under consideration. Solutions of 10wt% polystyrene in cyclohexanol were prepared at 90°C and then placed in an oven at a temperature of 115-120°C. Note that the upper critical solution temperature of polystyrene/cyclohexanol system is about 82°C (Shultz and Flory, 1953). Also, the critical composition is at a polymer volume fraction of about 0.03, while the polymer-rich binodal composition is at a volume fraction of about 0.20. Thus, the cast solutions are expected to coagulate inside the spinodal curve, as we have verified using a diode-array time-resolved light scattering system similar to that used by Hashimoto and his coworkers (Inaba et al., 1986). Solid membranes were then made within 24 h, after the solutions were prepared. These membranes were then sputter-coated with gold-palladium and observed under the microscope. 

With a great deal of certainty the observed evolution of sttucture in polystyrene/ cyclohexanol system can be applied to other amorphous polymer systems undergoing thermally induced spinodal decomposition, which is the nonreactive analog of the FRRPP process for polymer/small-molecule systems. 

For the polystyrene/cyclohexanol system, = 1-0. This means that the polymer-rich domains will have to travel a composition distance that is equal to that of the solvent-rich domains in order to reach its binodal composition (symmetric case in Fig. 1.4.4). However, if the polymer composition asymmetry ratio is equal to about 2 (such as in Fig. 1.4.5), then half of the polymer-rich domains is believed to migrate to adjacent domains in order for the rest of the polymer-rich domains to continue to approach the binodal composition (Cahn, 1961). Since there is equal competition for polymer-rich material from every domain, then the position of the resulting holes (or cells) will be in a regular lattice position. Continued growth of structure should be based on the belief that the domains that are eaten up are those that are contiguous to the most number of polymer-rich domains. Also, as implied by the presence of distinct dominant frequencies for spinodal decomposition mechanism, the disappearance of contiguous polymer-rich domains should occur uniformly in space. 

SON Song, S.-W. and Torkelson, J.M., Coarsening effects on the formation of microporous membranes produced via thermally induced phase separation of polystyrene-cyclohexanol solutions, J. Membrane Sci., 98, 209, 1995. 

RUD Rudder, J. de, Berghmans, H., and Amauts, J., Phase behavionr and stmcture formation in the system syndiotactic polystyrene/cyclohexanol, Polymer, 40, 5919, 1999. 

By combining Eqs. (8.42), (8.49), and (8.60), show that Vi°(52 - 5i) = (l/2)RTj., where T. is the critical temperature for phase separation. For polystyrene with M = 3 X 10, Shultz and Floryf observed T. values of 68 and 84°C, respectively, for cyclohexanone and cyclohexanol. Values of Vi° for these solvents are abut 108 and 106 cm mol", respectively, and 5i values are listed in Table 8.2. Use each of these T. values to form separate estimates of 62 for polystyrene and compare the calculated values with each other and with the value for 62 from Table 8.2. Briefly comment on the agreement or lack thereof for the calculated and accepted 5 s in terms of the assumptions inherent in this method. Criticize or defend the following proposition for systems where use of the above relationship is justified Polymer will be miscible in all proportions in low molecular weight solvents from which they differ in 5 value by about 3 or less. 

The structure of atactic polystyrene gels was studied by Keller et al. [276,287, 288]. The results will be demonstrated on the basis of Fig. 86, where the upper region of the atactic polystyrene (M = 2750 kg/mol)/cyclohexanol phase Vagram is shown. 

Simulation results in binary amorphous polymer/solvent systems have been obtained for a poly(methyl methacrylate) (PMMA)/sulfolane system (Caneba and Soong, 1985b), which has a UCST of 51°C. For a polystyrene (PS)/cyclohexanol system with a UCST of 82°C, simulation results are presented by Caneba and Saxena (1996). Table 1.4.1 shows parameter values used in these systems. 

Polystyrene used in the experiments was a primary standard (mol. wt. = 400,000 Da), purchased from Pressure Chemical Company. The solvent used was cyclohexanol obtained from Aldrich and was fractionally distilled before use. 

Figure 1.4.33 shows scanning electron micrographs of the cross-section of a polystyrene membrane that was coagulated at 80°C from a 10 wt% polystyrene solution in cyclohexanol. The left of Fig. 1.4.33(a) corresponds to the thermal conductor side (the side in contact with the aluminum foil of the coagulation cell shown... 

Fig. 1.4.33(a) Scanning electron micrograph of thermal conductor side of a polystyrene membrane that was cast at 80°C from a solution of 10 wt% polystyrene in cyclohexanol. For this quenching time of 5 min, pores are 0.4-1.2 xm, while cells are 1.2. 0 xm... 

Theta solvents have been established for poly(A -vinylcarbazole) in single solvents and for polystyrene in single and binary mixtures of 1-chlorodecane-3-methyl cyclohexanol. This has allowed Bazuaye and Huglin to determine the unperturbed dimensions as a function of solvent and temperature for polystyrene, from which it was observed that these were always higher in mixed solvent systems compared with the single theta solvent, and that preferential adsorption was not responsible. Friedrich and Prochazka carried this one step further and examined polystyrene in toluene-MEK—2-methylpropan-l-ol mixtures, i.e., two solvents and one precipitant. They showed that the composition at which the second virial coefficient was zero and at which [ /] attained the values comparable to a theta solvent, were not identical, but in this case preferential adsorption was used as an explanation. 

Reports have appeared on the rates of decomposition of cyclohexyl hydroperoxide (an intermediate in the industrial oxidation of cyclohexaneto cyclohexanol and cyclohexanone catalyzed by Ru(porp)CO and Ru(porp)(0)i systems (porp = rCPP, mCrPP, TDCPP, TMCPP, TMP, TPP) either in solution or anchored to polystyrene or silica . The systems were studied in 20 1 cyclohexane/CH2Cl2 at 25°C, when decompositions in the 28-66% range were observed after 2 h, and close to 100% after 48 Several, plausible reaction pathways were... 

GAR Garcia Sakai, V., Higgins, J.S., and Trasler, J.P.M., Cloud curves of polystyrene or poly(methyl methacrylate) or poly(styrene-co-methyl methacrylate) in cyclohexanol determined with a thermo-optical apparatus, J. Chem. Eng. Data, 51, 743, 2006. 

New supramolecular structure of syndio-tactic polystyrene showing a bird s-nest-like structure, obtained from a cyclohexanol solution by thermally induced phase separation (scanning electron microscope image by M. van Heeringen, Dow Terneuzen) (Van Heeringen, M., Vastenhout, B., Koopmans, R., Aerts, L. e-Polymers [2005], no. 048.)... 

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