Upper critical solution temperature polystyrene

The system with which we have begun our investigations is the styrene-dimethylsiloxane system. The dimethylsiloxane blocks should be considerably less compatible with polystyrene blocks than either polybutadiene or polyisoprene since the solubility parameter of dimethylsiloxane is much farther from that of polystyrene than are the solubility parameters of polybutadienes or of polyisoprenes (17), no matter what their microstructure. Furthermore, even hexamers of polystyrene and of polydimethylsiloxane are immiscible at room temperature and have an upper critical-solution temperature above 35°C (18). In addition, the microphases in this system can be observed without staining and with no ambiguity about the identity of the phases in the transmission electron microscope (TEM) silicon has a much higher atomic number than carbon or oxygen, making the polydimethylsiloxane microphases the dark phases in TEM (19,20). 

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). 

This figure clearly shows the temperature and composition windows where it is either a two-phase system or a single-phase system. The characteristic features of an upper critical solution temperature (UCST) and a lower critical solution temperature (LCST) corresponding to the phase transition are identified. For a particular composition of two immiscible polymers, if the temperature is increased, the UCST is the highest temperature at which two phases may co-exist in the blend. There is then a window of miscibility as the temperature is increased further, followed by phase separation again at the LCST. This type of diagram is often seen for polymer solutions, e.g. polystyrene in cyclohexane. Often polymer blends show... 

Ougizawa, T. and Walsh, D.J. 1993. Upper critical solution temperature behavior in polystyrene/polyfmethyl... 

Only a few sterns are available which meet these conditions. The first degradation studies investigating the interrelation of thermodynamics and chain scission were done using polystyrene (PS) in various solvents The system studied most extensively so far is given by trons-decalin/PS (TD/PS) It exhibits upper critical solution temperature and a theta temperature of 21 °C Figure 5 shows the corresponding cloud point curves determined for narrowly distributed PS samples. 

Fig. 5. Cloud point curves for narrowly distributed polystyrenes in tra/u-decalin The dashed line connects the respective upper critical solution temperatures...

SAE Saeki, S., Kuwahara, N., Nakata, M., and Kaneko, M., Pressure dependence of upper critical solutions temperatures in the polystyrene-cyclohexane system. Polymer, 16, 445, 1975. 

KOA Koak, N., Loos, Th.W. de, and Heidemann, R.A., Upper-critical-solution-temperature behavior of the system polystyrene + methylcyclohexane. Influence of CO2 on the liquid-liqttideqttilibria, / / / //., 145, 311, 1998. 

Surface-directed spinodal decomposition was first observed in an isotopic polymer blend (Jones et al. 1991) thin films of a mixture of poly(ethylene-propylene) and its deuterated analogue were annealed below the upper critical solution temperature and the depth profiles measured using forward recoil spectrometry, to reveal oscillatory profiles similar to those sketched in figure 5.30. Similar results have now been obtained for a number of other polymer blends, including polystyrene with partially brominated polyst)u-ene (Bruder and Brenn 1992), polystyrene with poly(a-methyl styrene) (Geoghegan et al. 1995) and polystyrene with tetramethylbisphenol-A polycarbonate (Kim et al. 1994), suggesting that the phenomenon is rather general. 

CAN Can, A., Hoppener, S., Guillet, P., Gohy, J.-F., Hoogenboom, R., and Schubert, U.S., Upper critical solution temperature switchable micelles based on polystyrene-6/oc -poly(methyl acrylate) block copolymers, J. Polym. Sci. Part A Polym. Chem., 49, 3681,2011. 

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. 

Experimental phase diagrams for amorphous block copolymers were explored by Khandpur and co-workers (29). First, low-frequency isochronal shear modulus-temperature curves were developed on a series of polyiso-prene-h/ocA -polystyrene polymers to guide the selection of temperatures for the transmission electron microscopy and SAXS experiments to follow see Figure 13.14 (29). Both order-order (OOT) and ODT transitions were iden-tihed. The OOT are marked by open arrows, while the ODT are shown by hlled arrows. Since the ODT occurs as the temperature is raised, an upper critical solution temperature is indicated, much more frequent with block copolymers than with polymer blends. The regions marked A, B, C, and D denote lamellar, bi-continuous, cylindrical, and perforated layered microstructures, respectively. The changes in morphology are driven by the temperature dependence of Xn,... 

HAY Hayduk, W. and Bromfiled, H.A., 0-cosolvent solutions for poly(vinyl chloride) by cloud point and osmotic pressure measurements, J. Appl. Polym. Sci., 22, 149, 1978. 1978ISH Ishizawa, M., Kuwahara, N., Nakata, M., Nagayama, W., and Kaneko, M. Pressure dependence of upper critical solution temperatures in the system polystyrene-... 

Schwahn et al [175] were the first to report a transition from mean-field to non-mean-field behavior in polymer mixtures on the basis of SANS results obtained from a PS-poly(vinyl methyl ether) (PVME) mixture. Subsequently, Bates et al. [176] quantitatively verified these conclusions using a model polyisoprene-poly(ethylene-propylene) mixture above the upper critical solution temperature (Tc = 38 °C), which revealed a transition from y = 2v = 1 (mean-field behavior) toy = 1.26 (non-mean-field behavior) approximately 30 °C above the critical temperature. These SANS crossover studies established the limitations of mean-field theory, which has been used extensively for evaluating polymer-qx)lymer thermodynamics, and similar crossover phenomena have been investigated via SANS for polymers in small-molecule solvents (e.g. polystyrene in cyclohexane) and supercritical media (e.g. polydimethylsiloxane in CO2), as described in Section 7.6.4... 

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. 

Example 9.2 Listed in Table 9.1 are data for the upper critical solution temperature of six polystyrene (PS)-in-dioctylphthalate (DOP) solutions as a function of molecular weight [10]. Also given is the corresponding ratio of molar volumes. Determine the temperature dependence of the interaction parameter. 

What is the value of m, the ratio of the molar volume of polymer to the molar volume of solvent, for polystyrene of 250,000 molecular weight dissolved in toluene Thus, determine %c lii polymer volume fraction corresponding to the upper critical solution temperature. Assume that the density of polystyrene is 1.1 g/cm and that of toluene is 0.86 g/cm. ... 

Saeki, S. Kuwahara, N. Konno, S. Kaneko, M., "Upper and Lower Critical Solution Temperatures in Polystyrene Solutions. II," Macromolecules, 6, 589 (1973b). 

---