Polystyrene fractionation

The osmotic pressure of polystyrene fractions in toluene and methyl ethyl ketone was measuredt at 25°C and the following results were obtained ... 

Block copolymer chemistry and architecture is well described in polymer textbooks and monographs [40]. The block copolymers of PSA interest consist of anionically polymerized styrene-isoprene or styrene-butadiene diblocks usually terminating with a second styrene block to form an SIS or SBS triblock, or terminating at a central nucleus to form a radial or star polymer (SI) . Representative structures are shown in Fig. 5. For most PSA formulations the softer SIS is preferred over SBS. In many respects, SIS may be treated as a thermoplastic, thermoprocessible natural rubber with a somewhat higher modulus due to filler effect of the polystyrene fraction. Two longer reviews [41,42] of styrenic block copolymer PSAs have been published. 

Typical results of lightscattering measurements are shown in Figs. 47 and 48 for polystyrene fractions of medium and of very high molecular weight, respectively. The small dissymmetry correction for the former was calculated from the measured dissymmetry coefficient 45°( l-2) using Eqs. (31) and (32). 

Table XXVIII.—Comparison of Light Scattering with Osmotic Molecular Weights for Polystyrene Fractions (Brice, Halwer, and Speiser )...

Fig. 49.—Reciprocal of the sedimentation constant s plotted against concentration for two polystyrene fractions in chloroform. Molecular weights 13X10 and 5.5X10 for fractions 1 and 19, respectively. (Newman and Eirich. )...

Fig. 118.—Plot of log (RTA2) against log M for polystyrene fractions in toluene. Filled circles represent slopes of the curves shown in Fig. 116. Open circles are from the results of Frank and Mark. i Dashed line calculated as described in text. (Krigbaum.29)...

Fig. 122.—A plot of the reciprocal of the critical temperature against the molecular size function occurring in Eq. (7) for polystyrene fractions in cyclohexane (O) and for polyisobutylene fractions in diisobutyl ketone (0). (Shultz and Flory. )...

Fig. 126.—The ternary system consisting of cyclohexane and two polystyrene fractions (x2 — 770 and 0 3 = 11,000) at 28.2°C. Solid lines are drawn through the experimental points results of theoretical calculation are shown by the dotted lines. (Shultz and Flory.3)...

The final proof of the physical reality of our model of macromolecular adsorption was provided by simultaneous independent work, by an entirely different method, at the National Bureau of Standards (27). Stromberg et al., allowed polystyrene fractions, besides other polymers, to become adsorbed on ferrochrome plates and determined the thicknesses of the adsorbed layers... 

Table 3. Molecular weight M of a monodisperse polystyrene fraction in solvents of different refractive index no role of refractive index correction factor74)...

Fig. 22. KMHS relationships for the fractions of end-linked 3-arm star-branched polystyrene molecules and of linear polystyrene fractions. The data refer to three samples of different in the pregel state and one from the sol fraction of a gel. The curves for the branched macromolecules coincide within experimental error in the high molar mass region. The deviations at lowM result from a different amount of non-reacted end-functionalized stars. The exponents of the end-linked and linear PS chains are a =0.42 0.02 while that of linear chains is 0.70 0.01 [95,120,123,124]. Reprinted with permission from [95]. Copyright [1997] American Society...

Figure 4. GPC analysis of polystyrene fractions from 400 mg preparative run (one prep column).

Table II. Molecular Weight Averages of Polystyrene Fractions from...

Table III. Molecular Weight Averages i of Polystyrene Fractions ...

Alfrey, T., A. Bartovics, and H. Mark Comparative Osmotic and Viscosity Measurements with Polystyrene Fractions. J. Amer. chem. Soc. 65, 2319 (1943). 

The following intrinsic viscosity values of some high molecular weight polystyrene fractions have been reportedf ... 

For polystyrene fractions in diethyl phthalate solution (30000average value of 1.6 x 10 18 ( 50%). In dilute solution e/36M is 1.27 x 10 18 for polystyrene (21). No systematic variations with concentration, molecular weight or temperature were apparent, the scatter of the data being mainly attributable to the experimental difficulties of the diffusion measurements. The value of Drj/cRT for an undiluted tagged fraction of polyfn-butyl acrylate) m pure polymer was found to be 2.8 x 10 18. The value of dilute solution data for other acrylate polymers (34). Thus, transport behavior, like the scattering experiments, supports random coil configuration in concentrated systems, with perhaps some small expansion beyond 6-dimensions. 

Fig. 5.1. Flow birefringence An vs. shear rate q for solutions of a polystyrene fraction of high molecular weight (ikf = 1.7 X 10 ) in dioxane according to Frisman and Syto Mao (139). Concentrations in g/100 cm3 are given near the curves...

A universal calibration curve was established by plotting the product of the limiting viscosity numbers and molecular weight, Mw[iy], vs. the elution volume, EV, for a variety of characterized polymers. The major usefulness of the universal calibration curve was to validate individual molecular-weight values and to provide extended molecular-weight calibration at the ends of the calibration curve where fractions of narrow dispersion of the polymer being analyzed are not available. The calibration curve was monitored daily with polystyrene fractions certified by Pressure Chemicals. The relationship between the polyethylene fractions and polystyrene fractions was determined using the universal calibration curve. 

Table II. Basis-Generating Chromatograms of Narrow Polystyrene Fractions Peak Position,6 ...

A relationship has been developed by means of which more valid values are obtained by GPC for the average degrees of polymerization for cellulose. This can be extended to other polymers. With automation of data acquisition and computer processing of data, a differential molecular weight distribution and complete information on DP of the sample are available in very short order with a low degree of error. The ready availability of narrow, well characterized polystyrene fractions for calibration makes this procedure highly attractive in view of the lack of similar standards of cellulose. 

K 17 Kurosaki, S., T. Sudo and S. Watanabe Sedimentation, diffusion and viscosity of polystyrene fractions in benzene solutions. J. Chem. Soc. Japan, Pure Chem. Sect. 73, 789 (1952). 

Figure 6, illustrating some data from the analytical column, shows chromatograms of two 0.5% solutions of unfractionated BBB samples with [77] equal to 2.6 and 0.2 dl./gram Figure 7 shows chromatograms of three of the fractions of the unfractionated sample with [77] = 2.6 that were obtained from the preparative column. The product [77] M for these three fractions correlates satisfactorily with the function relating [77] M with Ve/Vy found for the polystyrene fraction. 

The values of Mw recorded in Table I have been used to plot M[vf vs. Ve/VT on Figure 5 for the fractions of BBB studied (after correlation of [772] in methanesulfonic acid to [771] in 96% sulfuric acid by the relation [771] = 0.67 [772]). The results are in reasonable agreement with the empirical relation between [77] M and Ve/VT found with the polystyrene fractions. 

Firstly, it has been shown that there may be many experimental problems in a direct determination of the experimental fimction. In shear, damping functions obtained from step strain and from step strain rate experiments do not match each other. This poses an important question on the validity of the separability assumption in the short time rai e. Significant departures from this factorization have already been observed in the case of narrow polystyrene fractions by Takahashi et al. [54]. These authors found that time-strain superposition of the linear and nonlinear relaxation moduli was only possible above a cert2un characteristic time. It is interesting to note that this is predicted by the Doi-Edwards theory [10] and according to this theory, this phenomena is attributed to an additional decrease of the modulus connected to a tube contraction process and time-strain separability may hold after this equilibration process has been completed. Other examples of non-separability were also reported by Einaga et al. [55] and more recently by Venerus et al. [56] for solutions. 

Figure 9.8 Double logarithmic plot of the retardation spectrum versus the retardation time for a polystyrene fraction of molecular weight 3400 with a narrow molecular weight distribution. (From Ref. 8.)...

The molecvilar weight dependence of A and K for short chains is uncertain in part because of the difficulty of obtaining reliable estimates for these parameters near Tg. For example, the data for a polystyrene fraction with — 10.5 can be correlated by a Vogel expression, and yield d = 0 (i.e., Tq — Tg), if considerable weight is placed on data... 

Polystyrene fractions. Numerical data for the PS reference fractions are summarized in Table III Cp(T) curves are not shown, as they resemble the conventional glass behavior illustrated on Figure 2. 

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