Solutions concentrated polystyrene

In HOPC, a concentrated solution of polymer is injected. The concentration needs to be sufficiently higher than the overlap concentration c at which congestion of polymer chains occurs. The c is approximately equal to the reciprocal of the intrinsic viscosity of the polymer. In terms of mass concentration, c is quite low. For monodisperse polystyrene, c is given as (4)... 

The temperature variations within the solution were increased from Test 1 ( Tn which the initial polystyrene concentration was 0%) to Test 2 (in which it was 15 ) and to Test 3 (in which it was 30 ) respectively. The maximum temperature differences between T2 and T were only 10° in Test 1, and 15° in Test 2 but 78° in Test 3. The greater the temperature differences, the greater the error of calculating T. Hence, the computations for T were decreasingly accurate in Test 1, 2 and 3 respectively. 

For concentrated solutions of polystyrene in n-butylbenzene, Graessley [40] has shown that the reduced viscosity r red Cnred=(r ( y)- rls)/(rlo rls)) can be represented on a master curve if it is plotted versus the reduced shear rate (3 ((3= y/ ycnt= y-A0). For semi-dilute solutions a perfect master curve is obtained if (3 is plotted versus a slope corrected for reduced viscosity, T corp as shown in Fig. 16. 

Figure 3. Intrinsic viscosity of polystyrene samples, irradiated in benzene solution in the presence of initiator I-III. Polystyrene concentration 7.69x10 2 M, photoinitiator concentration 2.31 x 10-3 Ml p Pure polystyrene initiator I initiator II A initiator III. (Reproduced with permission from Polym. Deg. Stability Ref. 21).

Figure 4. Intrinsic viscosity of polystyrene samples irradiated in benzene solution under various conditions. Polystyrene concentration 7.69x 10-2 M and initiator I concentration 3.12x 10-3 M. vacuum nitrogen saturated air saturated V oxygen saturated 3.12 3 / 3-tert-butyl-4-hydroxyanisole 3.12x 10-3 M 1.4-diazobicyclo(2.2.2)-octane (DABCO).

Tager and co-workers (51) have invoked bundle structures to explain correlations between the viscosities of concentrated polymer solutions and the thermodynamic interactions between polymer and solvent. They note, for example, that solutions of polystyrene in decalin (a poor solvent) have higher viscosities than in ethyl benzene (a good solvent) at the same concentration, and quote a number of other examples. Such results are attributed to the ability of good solvents to break up the bundle structure the bundles presumably persist in poor solvents and give rise to a higher viscosity. It seems possible that such behavior could also be explained, at least in part, by the effects of solvent on free volume (see Section 5). Berry and Fox have found, for example, that concentrated solution data on polyvinyl acetate in solvents erf quite different thermodynamic interaction could be reduced satisfactorily by free volume considerations alone (16). Differences due to solvent which remain after correction for free volume... 

Fig. 8.15. Viscosity vs shear rate in concentrated solutions of narrow distribution polystyrene The solvent in n-butyl benzene, the concentration is 0.300 gm/ml and the temperature is 30° C. The symbols are O for M = 860000 and for M = 411000 at low shear rates (155) and at high shear rates (346). The solid line for M= 860000 is the master curve for monodisperse systems from Graessley (227). The solid line for M=411000 is the master curve from Ree-Eyring (341). Either master curve fits data for both molecular weights...

Dreval.V.Ye., Tager,A.A., Fomina,A.S. Concentrated solutions of polymers. IV. Viscosity of solutions of polystyrene in various solvents. Polymer Sci. USSR 5,495-507 (1964) [Vysokomolekul. Soyedin. 5,1404 (1963). 

Graessley, W.W., Hazleton,R.L., Lindeman,L.R, The shear-rate dependence of viscosity in concentrated solutions of narrow-distribution polystyrene. Trans. Soc. Rheol. 11,267-285 (1967). 

Gupta,D., Forsman,W.C. Newtonian viscosity-molecular weight relationship for concentrated solutions of monodisperse polystyrene. Macromolecules 2, 304-306... 

Wolkowicz,R.I., Foreman, W.C. Entanglement in concentrated solutions of polystyrene with narrow distributions of molecular weight Macromolecules 4, 184-192 (1971). 

J. O. Park and G. C. Berry, Moderately concentrated solutions of polystyrene. III. Viscoelastic properties at the Flory theta temperature , Macromolecules, 22, 3022 (1989). 

Fox TG, Flory PJ (1948) Viscosity-molecular weight and viscosity-temperature relationships for polystyrene and polyisobutylene. J Am Chem Soc 70(7) 2384-2395 Freed KF, Edwards SF (1974) Polymer viscosity in concentrated solutions. J Chem Phys 61(9) 3626-3633... 

The study by low-angle X-ray diffraction and electron microscopy of concentrated solutions of the copolymers in preferential solvents for polybutadiene (iso-prene, butadiene) or for poly(a-methyl styrene) (styrene, a-methylstyrene, methyl methacrylate, methylethyl ketone) and of copolymers in the dry state obtained by slow evaporation of the solvent from the mesophases have shown the existence of three types of structure hexagonal, lamellar, and inverse hexagonal depending upon the copolymer composition84,85. The factors governing the structural type and the structural parameters are the same as in the case of polystyrene-polybutadiene copolymers85. ... 

When using polystyrene solutions for the impregnation of the composite-matrix, one must use concentrated solutions (PS concentration 5.0 g/100 mL), from which aggregates of macromolecules can penetrate into the composite pore space. After carbonization, carbon structures were obtained, which were tubes of up to 320 nm diameter or aggregates of up to 100 nm particles. 

Most studies of magnetic relaxation in polymers have dealt with solid or melted polymers (73)] however, Odajima (20) has studied proton relaxation in solutions of polystyrene and polyisobutylene. It is desirable to extend and refine such measurements. In concentrated solution, some insight into the motional effects of polymer-solvent interactions should be obtainable and if, despite low sensitivity, reliable 7 values can be obtained for polymers in dilute solutions, valuable information concerning the detailed motional behavior of isolated polymer molecules may be provided. 

Fig. 16.9 shows the low frequency slopes of 2 and 1, respectively, as expected for viscoelastic liquids and the high frequency slopes Vi and 2/3 for Rouse s and Zimm s models, respectively. Experimentally it appears that in general Zimm s model is in agreement with very dilute polymer solutions, and Rouse s model at moderately concentrated polymer solutions to polymer melts. An example is presented in Fig. 16.10. The solution of the high molecular weight polystyrene (III) behaves Rouse-like (free-draining), whereas the low molecular weight polystyrene with approximately the same concentration behaves Zimm-like (non-draining). The higher concentrated solution of this polymer illustrates a transition from Zimm-like to Rouse-like behaviour (non-draining nor free-draining, hence with intermediate hydrodynamic interaction).

These conclusions are in agreement with results reported by Janeschitz-Kriegl (1969), who measured the shear compliance JeR of highly concentrated to very dilute solutions of a series of polystyrenes with narrow molecular weight distributions. For the melt down to moderately concentrated solutions JeR appeared to be equal to 0.4, which is the value to be expected for free-draining solutions. In very dilute solutions JeR tended to decrease to the non-draining case, where /eR=0.205. 

The separation of polymers due to thermal diffusion may be quite large. For example, the thermal diffusion ratio for dilute solutions of polystyrene in tetrahydrofuran is around 0.6 K1. This indicates that the change of polystyrene concentration per degree is 60%. The type of solvent and polymer pair may have a considerable effect on both the thermal diffusion ratio and the thermal diffusion coefficient. 

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