Polystyrene-solvent systems

Schuster, R. H. Grater, H. Cantow, H.-J., "Thermodynamic Studies on Polystyrene-Solvent Systems by Gas Chromatography," Macromolecules, 17, 619 (1984). 

For the polystyrene/solvent systems listed (Caneba, 1992a, b), careful selection of the solvent(s) permitted the FRRPP process to be carried out at a relatively low temperature, which made this new polymerization method more promising. For high LCST systems, specially designed reactors can be used to carry out the FRRPP process. However the limitation is, the higher the temperature, the more likely the incipience of thermal degradation in the system. Additionally, running the free-radical... 

SC2 Schuster, R.H., Grater, H., and Cantow, H.J., Thermodynamic studies on polystyrene-solvent systems by gas chromatography, Macro/wo/ecw/es, 17, 619, 1984. 

Kobayashi, M., Yoshioka, T., Kozasa, T., Tashiro, K., Suzuki, J.-I., Funahashi, S., Izumi, Y. Structure of physical gels formed in syndiotactic polystyrene/solvent systems studied by smaU-angle neutron scattering. Macromolecules, 27,1349-1354 (1994). 

Roels, T., Deberdt, E, Berghmans, H. Thermoreversible gelation in syndiotactic polystyrene solvent systems. Progr. Colloid Polym. Sci., 102,82-85 (1996). 

Reciprocals of the critical temperatures, i.e., the maxima in curves such as those in Fig. 121, are plotted in Fig. 122 against the function l/x +l/2x, which is very nearly 1/x when x is large. The upper line represents polystyrene in cyclohexane and the lower one polyisobutylene in diisobutyl ketone. Both are accurately linear within experimental error. This is typical of polymer-solvent systems exhibiting limited miscibility. The intercepts represent 0. Values obtained in this manner agree within experimental error (<1°) with those derived from osmotic measurements, taking 0 to be the temperature at which A2 is zero (see Chap. XII). Precipitation measurements carried out on a series of fractions offer a relatively simple method for accurate determination of this critical temperature, which occupies an important role in the treatment of various polymer solution properties. 

The results of intrinsic viscosity measurements for four polymer-solvent systems made at the -temperature of each are shown in Fig. 141. The four systems and their -temperatures are polyisobutylene in benzene at 24°C, polystyrene in cyclohexane at 34°C, poly-(di-methylsiloxane) in methyl ethyl ketone at 20°C, and cellulose tricapry-late in 7-phenylpropyl alcohol at 48°C. In each case a series of poly-... 

Fig. 6. Specific viscosity, r sp, as a function of the product c- [q] for narrowly distributed polystyrene in toluene (good solvent) (A) and frans-decalin (poor solvent) ( ) at 25 °C. Experimental data for the polystyrene/toluene system at 30 °C (taken from [65]) are represented by (O). 

The solvent system 70/30 methylene chloride/ hexafluorolsopropanol has been In use In our laboratory since 1977 as a solvent for poly(ethylene terephthalate) (PET) and other semlcrystalllne polar polymers. Some advantages of this solvent are It provides rapid room temperature solubilization It Is transparent at 254 nm (U.V.) It Is a solvent for polystyrene and It Is a minimum boiling azeotrope. Disadvantages are Its low boiling point (36 C) and the potential safety hazard It represents. The combination of appropriate HPGPC equipment and this solvent system reveals heretofore unrecognized features of the molecular weight distributions of polyesters ... 

In a kinetic sense, the system is a better solvent than HFIP alone. We postulate that MeCl2 swells the amorphous regions of PET thereby providing HFIP with an easy access to the crystalline regions. This swelling action does not occur with HFIP alone, and the dissolution process takes much longer. At room temperature, amorphous PET is Instantaneously solubilized by this solvent system. PET that has been annealed for >24 hr at 220 C to yield maximum crystallinity dissolves in <4 hr at room temperature. PET annealed in this manner does not dissolve in pure HFIP after 14 days at room temperature. Poly(butylene terephthalate) and aliphatic polyamides are soluble in this solvent system. Polystyrene is also soluble, which permits conventional calibration and the use of the universal calibration approach. We have determined the Mark-Houwlnk relationships for PET and polystyrene in 70/30 MeCl2/HFIP to be... 

These manipulations may appear to add little except for needless complication to an interpretation of the second virial coefficient for random coils. Recall, however, that Equation (81) allows the variation of solvent goodness caused by temperature changes to be described quantitatively. Thus the interaction parameter x is used to describe how B changes when a polymer is dissolved in different solvents. By contrast, 9 is used to describe the variation in B when a given polymer-solvent system is examined at different temperatures. This has been done for the polystyrene-cyclohexane system at three different temperatures the results are discussed in Example 3.4. 

Fig, 5.3. Viscosity at various concentrations and molecular weights in the low to moderate concentration range. Polystyrene-decalin and polymethyl methacrylate-xylene are theta or near-theta systems the remainder are good solvent systems (121,177). Note that the c[i/] reduction is somewhat better in theta solvents, and that the Martin equation [Eq. (5.9)], which would give a straight line in the figure, is a somewhat better representation for... 

The existence of a true graft copolymer was concluded from the weight increase not extractable by polystyrene solvents and by the eventual leveling off of the weight increase while homopolymerization continued. Moreover, the graft of cellulose acetate and styrene after dissolution and precipitation with various solvents and precipitants still showed the infrared absorption of both substituents. In addition to this, the results fitted well with the kinetic theoiy of grafting proved on other systems. 

K and a in the expression, [17] = KM , are 3.7 x 10-5 m3 kg-1 and 0.62, respectively, for this polymer-solvent system. Assuming a constant density for the solutions, calculate an average relative molecular mass for the polystyrene sample. How would this relative molecular mass be expected to compare with the relative molecular mass of the same sample of polystyrene in toluene determined from a) osmotic pressure and (b) light-scattering measurements ... 

Table 5.6 The number a of solvent molecules sorbed per phenyl group and the limiting Flory -Huggins parameter x0 for polystyrene-divinylbenzene copolymers- solvent systems (Errede 1989)...

The character of the polymethyl methacrylate data is essentially similar to that found for systems atactic polystyrene-benzene at 25°, 35°, and 50° C. [Kishimoto, Fujita, Odani, Kurata and Tamura (1960) Odani, Kida, Kurata and Tamura (1961)] and also atactic polystyrene-methyl ethyl ketone at 25° C. [Odani, Hayashi and Tamura (1961)], and appears to be fairly general for amorphous polymer-solvent systems in the glassy state. On the other hand, the cellulose nitrate data shown in Fig. 8 appear to manifest features characteristic of crystalline polymer-solvent systems. For example, the earlier data of Newns (1956) on the system regenerated cellulose-water (in this case, water is not the solvent but merely a swelling-agent) and recent studies for several crystalline polymers all show essentially similar characters [see Kishimoto, Fujita, Odani, Kurata and Tamura (I960)]. To arrive at a more definite conclusion, however, more extensive experimental data are needed. 

Phase Relationships. The first systematic investigation of the two-phase behavior of polymer/polymer/solvent systems was probably made by Dobry and Boyer-Kawenoki (2) for a variety of polymer pairs, and more recently this work was extended by Kern and Slocombe (3) and Paxton (35) to a number of other systems including several vinyl polymers. Typically, the three-component phase behavior is as shown in Figure 19 for the polystyrene/polybutadiene/benzene system (2), where a one-phase (polystyrene/polybutadiene/benzene) region is separated by a phase boundary from a two-phase (polystyrene-rich/benzene and polybutadiene-rich/benzene) mixture. As with any three-component system of this type, a critical point exists somewhere near the maximum of the phase boundary, and appropriate tie lines give the compositions and amounts of the respective phases in the two-phase region. 

Kambour et al. performed extensive studies on the mechanisms of plasticization [18-25]. The correlation observed between the critical strain to craze and the extent of the glass-transition temperature (Tg) depression speaks strongly in favor of a mechanism of easier chain motion and hence easier void formation. In various studies on polycarbonate [19,24], polyphenylene oxide [20], polysulfone [21], polystyrene [22], and polyetherimide [25], Kambour and coauthors showed that the absorption of solvent and accompanying reduction in the polymer s glass-transition temperature could be correlated with a propensity for stress cracking. The experiments, performed over a wide range of polymer-solvent systems, allowed Kambour to observe that the critical strain to craze or crack was least in those systems where the polymer and the solvent had similar solubility values. The Hildebrand solubility parameter S [26] is defined as... 

For ternary polymer-polymer-solvent systems, the compositions of the equilibrium phases may be determined using a variety of microanalytical methods depending upon the chemical nature of the polymers (Dobry and Boyer-Kawenoki, 1947). Each of the phases is sampled, weighed, and dried to determine the solvent concentration. If the two polymers are sufficiently different chemically, microanalytical determination of carbon and hydrogen may be used. In systems containing polystyrene, the proportion of polystyrene may be determined by precipitating it with acetic acid and weighing the precipitate. Other microanalytical methods have also been used to determine phase compositions. 

Allen et al. (1960) used ultraviolet spectrometry to determine phase compositions in a polymer-polymer-solvent system containing polystyrene and polyisobutylene. At a wavelength of 250-260 nm, polystyrene has a strong adsorption band, which is linearly related to concentration, while polyisobutylene is transparent. Similarly, for a system containing polydimethylsiloxane and polyisobutylene, they used infrared spectrometry because poly-dimethylsiloxane absorbs at 1261 cm 1 and polyisobutylene is transparent at this wavelength. UVS and IRS have been used with other systems which contain only one polymer which has a strong adsorption band. 

---