Star-shaped polystyrenes

The randomly branched polystyrene and two star-shaped polystyrenes were obtained from the Polymer Science Department at the University of Akron, Akron, OH. 

Figure 16. DRI and Viscometer Traces of an Unfractionated Star-shaped Polystyrene.

When a tetra-chain, star-shaped polystyrene is prepared by a coupling reaction between living polymer and coupler (e.g 1,2,4,5-tetrachloromethyl benzene), the reaction is often carried out with the polystyryl anion in slight excess in order to avoid by-production of types of branched polystyrene other than the tetra-chain. 

Fig. 9. GPC elution curve for a reaction product of tetra-chain star-shaped polystyrene, coded S-A. For details, see text...

The foregoing section dealt with TLC separation of linear and branched polymers, from the standpoint of resolutions with respect to molecular weight. In this section we summarize TLC results of chromatographic distinguishment of linear and star-shaped polystyrenes on the same molecular-weight level. It is now well known that... 

Miyamoto ef a/.96 examined the possibility using tetra-chain, star-shaped polystyrene samples whose characteristics have already been given in Table 7 (see Section IV.4.). A gradient development was performed with a binary acetone + chloroform (50 9 by vol.) and chloroform as the initial and second solvents, respectively. 

A method for preparing star-shaped polystyrene by either the incremental or single addition of divinyl benzene to a living polystyryl anion is described. Star-shaped polymers containing up to 34 arms were prepared with polydispersities of less than 1.1. 

The thermodynamic affinity of cyclohexane to polystyrene is known to increase with temperature and, naturally, increasing the temperature must further raise the volume of the polystyrene networks in cyclohexane. There is, however, an additional point we should consider. The plot of Q vs. temperature exhibits a steplike discontinuity at around 30°C (Fig. 1.14). This discontinuity, resemhling very much a -transition, is located 3-5°C below the -temperature for linear polystyrene in cyclohexane and about 8°C above the -point for star-shaped polystyrene macromolecules. This phenomenon is outside the scope of the questions discussed here, but, naturally, the first assumption of the authors [143] seems to be very logical, according to which the discontinuity reflects a transition from Gaussian coil to a supercoiled compact structure on cooling the swollen gel below that temperature zone. 

Interaction chromatography can also be used to fractionate model polymers according to long-chain branching. An application for star-shaped polystyrenes was presented by Chang and co-workers (79). 

Figure 11.10 Synthesis of three-arm star-shaped polystyrene by TEMPO-mediated living radical polymerization and hydrolysis to TEMPO-capped linear polystyrene. (Drawn following the synthesis method of Hawker, 1995.)...

Kukula H, Schlaad H, Tauer K (2002) Linear and star-shaped polystyrene-block-poly(sodium glutamate)s as emulsifiers in the heterophase polymerization of styrene. Macromolecules 35 2538-2544... 

Xia, J., Zhang, X., and Matyjaszewski, K. (1999). Synthesis of star-shaped polystyrene by atom transfer radical polymerization using an arm first approach. Macromolecules, 52(13) 4482 1484. 

YOK Yokoyama, H., Takano, A., Okada, M., and Nose, T., Phase diagram of star-shaped polystyrene/cyclohexane system location of critical point and profile of coexistence... 

Lee HC, Lee W, Chang T, Yoon JS, Prater DJ, Mays JW. Linking reaction kinetics of star shaped polystyrene by temperature gradient interaction chromatography. Macromol 1998 31 4114. 

Knauss, D.M. and Huang, T. (2003) ((PS)nPS)n, star-shaped polystyrene with star-shaped branches at the terminal chain ends by convergent living anionic polymerization. Macromolecules, 36,6036-6042. 

Cloutet, E., Fillaut, J.-L., Astruc, D., and Gnanou, Y. (1999) Star block copolymers and hexafuUerene stars via derivatization of star-shaped polystyrenes. Macromolecules, 32,1043 1054. 

Abraham, S., Ha, C.-S., and Kim, I. (2006) Self-assembly of star-shaped polystyrene-WocA -polypeptide copolymers synthesized by the combination of atom transfer radical polymerization and ring-opening living polymerization of a-amino acid-N-carboxyanhydrides. Journal of Polymer Science Part A Polymer Chemistry,... 

Narumi A, Satoh T, Kaga H, Kakuchi T (2002) Glycoconjugated polymer. 3. Synthesis and amphiphilic property of core-glycoconjugated star-shaped polystyrene. Macromolecules 35(3) 699-705... 

Pasquale, A. J., Long, T. E., Synthesis of star-shaped polystyrenes via nitrogen-mediated stable free-radical polymerization /. Polym. Sci. A, Polym Chem. (2000) 39, pp. 216-223... 

Figure 29 Schematic cross section of a regular microporous film prepared by evaporation of CS2 solutions of star-shaped polystyrene or block copolymer. (From Ref 90.)...

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