Polystyrene star-shaped copolymers

QuasicrystaUine phases form at compositions close to the related crystalline phases. When solidified, the resultant strucmre has icosahedra threaded by a network of wedge disclinations, having resisted reconstruction into crystalline units with three-dimensional translational periodicity. The most well-known examples of quasicrystals are inorganic phases from the ternary intermetallic systems Al-Li-Cu, Al-Pd-Mn, Zn-Mg-Ln, Al-Ni-Co, Al-Cu-Co, and Al-Mn-Pd. In 2007, certain blends of polyisoprene, polystyrene, and poly(2-vinylpyridine) were found to form star-shaped copolymers that assemble into the first known organic quasicrystals (Hayashida et al., 2007). 

Transparent toughened polystyrene polymers are produced by blending polystyrene with SBS block copolymers (see Section 11.8). During the 1970s and 1980s most development was with block copolymers with a radial (or star) shape. Two types were developed block copolymers with a central butadiene block, and block copolymers with a central polystyrene block. 

In the first case, the arms are grown from a single core with a given number of potentially active sites or a well-defined multifunctional initiator. In contrast to anionic multifunctional initiators, weU-defined soluble multifunctional cationic initiators are readily available. These multifunctional initiators with 3-8 initiating sites have been successfully applied for the synthesis of 3-8 arm star homo- and block copolymers of vinyl ethers, styrene and styrene derivatives, and IB. For example, six-arm star polystyrenes were prepared using initiator with six phenylethylchloride-type functions emanating from a central hexa-substituted benzene ring [250]. By subsequent end functionalization, a variety of end-functionaUzed A or (AB) (see above) star-shaped structures can also be obtained. 

Francis, R., Taton, D., Logan, J.L. et al. (2003) Synthesis and surface properties of amphiphilic star-shaped and dendrimer-like copolymers based on polystyrene core and polyfethylene oxide) corona. Macromolecules, 36,8253-8259. 

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,... 

Another method for the synthesis of block copolymers is the sequential monomer addition method. In this method, the polymerization of TBA is initiated by the cationic living chain end of another cationic polymerization. This has been carried out with perchlorate-terminated polystyrene and with cationic living polyTHF as the initiating polymer. The polyTHF can be mono-, di-, or trifunctionally living leading to AB, BAB, and three-arm star-shaped block copolymers, respectively. ... 

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.)...

So far, there have been only few reports about the synthesis of amphipolar polymer brushes, i.e. with amphiphilic block copolymer side chains. Gna-nou et al. [115] first reported the ROMP of norbornenoyl-endfunctionalized polystyrene-f -poly(ethylene oxide) macromonomers. Due to the low degree of polymerization, the polymacromonomer adopted a star-like rather than a cylindrical shape. Schmidt et al. [123] synthesized amphipolar cylindrical brushes with poly(2-vinylpyridine)-block-polystyrene side chains via radical polymerization of the corresponding block macromonomer. A similar polymer brush with poly(a-methylstyrene)-Wocfc-poly(2-vinylpyridine) side chains was also synthesized by Ishizu et al. via radical polymerization [124]. Using the grafting from approach, Muller et al. [121, 125] synthesized... 

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