Star-branched polystyrene

Application to Randomly End Linked Star-Branched Polystyrenes. 169... 

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 16 shows the viscometer and DRI traces of another star-branched polystyrene. This sample contained about 12% of the starting linear arm precursor which eluted at retention volume ca. 52 ml. The kinetic molecular weight of the linear precursor was 260,000. The results obtained for the individual peak through the SEC/Viscosity methodology are summarized in Table 7. It is seen that the measured of the linear arm is very closed to the kinetic value. The average functionality of this star polymer is calculated to be f = 10. 

In 1965, Milkovich (. ) reported that divinylbenzene could be utilized for the formation of star-branched macromolecules. Later, Rempp and coworkers (2, 3, 4) successfully applied this method for the synthesis of star-branched polystyrenes. Moreover, Fetters and coworkers (54 ) used this procedure for the synthesis of multi-arm star-branched polyisoprene homopolymers and poly-... 

Utracki, L.A. Roovers, J.E.L. Viscosity and normal stresses of linear and star branched polystyrene solution. I. Application of corresponding states principle to zero-shear viscosities. Macromolecules 1973, 6 (3), 366-372. 

K. Yasuda, R.C. Armstrong, R.E. Cohen, Shear flow properties of concentrated solutions of linear and star branched polystyrene. Rheol. Acta 20, 163-178 (1981)... 

The size of the cell walls (as studied by AFM) was influenced by the length of the polystyrene block in the copolymer for molecular masses larger than 50.000 the regularity in the structure gradually disappeared. The authors related the mechanism of formation of this structure to the classical phase inversion process for the production of polymeric membranes [139]. In a later work the authors reported on the possibility to monitor this honeycomb structure in different polymeric systems including polystyrene-block-poly(p-phenylene), star branched polystyrenes, polystyrene-block-poly-3-hexylthiophene, and polystyrenes with polar endgroups and polymer blends [140]. Possible applications for such fascinating structures are in the area of polymeric membranes and optical devices. 

Table 2. Experimentally determined values of g, g of regular star>branched polystyrene...

Fig. S. Ini of star-branched polystyrene of a common arm length. Effect of increase in the...

Table 3. temperatures for regular star-branched polystyrenes in cyclohexane ... 

Viscosity enhancement in branched polystyrenes would be expected to be considerably smaller than in branched diene polymers. A smaller Z factor and a higher Me for this polymer combine to reduce the V value. The star-branched polymers shown in Fig. 11 would not therefore be expected to show viscosity enhancement at a concentration of 0.25 g/ml. Experiments reported on melt viscosities of star-branched polystyrenes having f 3 on the other hand would have been expected to have shown some enhancement at least at the h est molecular weight. None was in fact foimd, the viscosities beii approximately predictable from the Bueche theory i. e. were all lower than their linear counterparts. Viscosity enhancements have been reported for multibranch star polystyrenes (f = 7 to 13) in melt flow experiments. These are of comparable magnitude to the values found for four-brandi star pedybutadienes at the same value of M /Mc. Specific effects of multiple brandling were not considered in the model described above but there is evidence that the major enhancement effect is produced at f = 3. Increase of the branch nuniber to four at constant increases the enhancement by about a factor of two but subsequent increases in f have only small effect . ... 

COW Cowie, J.M.G., Horta, A., McEwen, I.J., and Prochazka, K., Upper and lower critical solution temperatures for star branched polystyrene in cyclohexane, Polym. Bull., 1, 329, 1979. 

FIG. 9-15. Logarithmic plots of [C ] and [G"] against frequency (unreduced) calculated from Zimm-Kilb theory for star-branched polystyrenes with molecular weight 10 in a solvent with viscosity 0.01 poise at 25 C, with large N and h = 0.25 or 0.05, and different degrees of branching from/= 2 (linear) to/= 13,... 

The (o,a), (o"-trilithiumpolystyrene (96) was also functionalized with carbon dioxide to form the corresponding (o,a), a)"-tricarboxypolystyrene (98) as shown in Scheme 32. Although significant amounts of dimer (11-12%) were observed when carbonation was effected in the presence of THF [241] or after end-capping the styryllithium chain ends with 1,1-diphenylethylene [141], procedures that were previously shown to be effective for quantitative carboxylation of poly(styryl)lithium, less than 2% dimer formation and formation of a tricarboxylated, three-arm, star-branched polystyrene with a functionality of 2.9s were obtained upon carboxylation of a freeze-dried [141] sample of 96. Previous studies indicate that dimer and trimer formation during carboxylation are enhanced by chain-end association [141, 241]. 

In order to investigate the best conditions for synthesis of heteroarm star-branched polymers using MDDPE, the preparation of four-armed, star-branched polystyrenes was examined in detail as illustrated in Scheme 34 [203, 207]. 

Hancock and Synovec " have carried out rapid characterization of linear and star branched polystyrene by gradient detection using methylene dichloride solutions of the polymers. This technique measures weight average molecular weights and is more specific than results obtained using a refractive index detector. 

Stewart, D. D. Peters, E. N. Beard, C. D. Dunks, G. B. Hadaya, E. Kwiatkowski, G. T. Mofifitt, R. B. Bohan, J. J. 1973. Viscosity and normal stresses of linear and star branched polystyrene solutions. II. Shear-dependent properties. Macromolecules, 12 373-7. 

Deffieux, A., Schappacher, M., Hirao, A., and Watanabe, T. (2008) Synthesis and AIM structural imaging of dendrimer-like star-branched polystyrenes. Journal ofthe American Chemical Society, 130,5670-5672. 

Yoo, H.-S., Watanabe, T., and Hirao, A. (2009) Precise synthesis of dendrimer-like star-branched polystyrenes and block copolymers composed of polystyrene and poly(methyl methacrylate) segments by an iterative methodology using hving anionic polymerization. Macromolecules, 42,4558 570. 

K. Huber, S. Bantle, W. Burchard and L. Fetters, "Semidilute Solutions of Star Branched Polystyrene A Light and Neutron Scattering Study, Macromolecules. 12, 1404-1411 (1986). 

T. Neidhoefer, S. Sioula, N. Hadjichristidis, and M. Wilhelm. Distinguishing linear from star-branched polystyrene solutions with Fourier-transform rheology. Macromol. Rapid Communications, 25 (2004), 1921-1926. 

Figure 6.39 Log G versus log G" plots at 170 for four 4-arm star-branched polystyrenes ...

Quirk, R. R, Tsai, Y. Trifimctional organolithium initiator. Synthesis of three-armed, star-branched polystyrenes. Macromol. (1998) 31, pp. 8016-8025... 

Osaki, K., Takatori, E., Kurata, M., Watanabe, H., Yoshida, H. Kotaka T. viscoelastic properties of solutions of star-branched polystyrene. Macromol. (1990) 23, pp. 4392-4396... 

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