Synthesis of Syndiotactic Polystyrene

Polymer Research Laboratory, Idemitsu Petrochemical Co., Ltd, Chiba, Japan 

Polystyrene was commercialized by I. G. Farben in 1931 and it has long been used as a commodity plastic. Although polystyrene is endowed with excellent properties not found in other commodity plastics such as polyolefins, its amorphous nature (relatively low heat and solvent resistance) limits its use in some application areas. 

Modern Styrenic Polymers Polystyrene and Styrenic Copolymers. Edited by J, Scheirs and D. B. Priddy r 2003 John Wiley Sons Ltd 

Since 1985, many different transition metal compounds have been examined for their ability to produce syndiotactic polystyrene in combination with counterions based on methylalumoxane, borane, borate and other chemicals. 

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Since the first report on the synthesis of syndiotactic polystyrene (sPS) by researchers at Idemitsu in the mid-1980s, a considerable amount of research has been directed toward the development of highly active,... 

Syndiotactic polystyrene was first obtained only recently by Ishihara et al. [5] in polymerisation with a homogeneous catalyst derived from a transition metal compound such as monocyclopentadienyltitanium trichloride and methylalu-minoxane in toluene. Since then, several authors have reported on the synthesis of syndiotactic polystyrene promoted by different catalysts based on metal hydrocarbyls such as benzyl compounds, half-sandwich metallocenes (e.g. monocyclopentadienyl, monopentamethylcyclopentadienyl and monoindenyl metal derivatives), metal alkoxides, metallocenes and some other compounds. These catalysts are commonly derived from titanium or zirconium compounds, either activated with methylaluminoxane or aluminium-free, such as those activated with tris(pentafluorophenyl)boron, and promote the syndiospecific polymerisation of styrene and substituted styrenes [5-10,21,48-70], Representative examples of the syndiospecific polymerisation of styrene using catalysts based on various titanium compounds and methylaluminoxane are shown in Table 4.2 [6,52,53,56,58],... 

Synthesis of Syndiotactic Polystyrene Using Metallocene/MAO Catalystsa... 

Table 24. Synthesis of syndiotactic polystyrene using metallocene/MAO catalysts...

Xu, G. Chung, T.C. Synthesis of syndiotactic polystyrene (s-PS) containing a terminal polar group and diblock copolymers containing s-PS and polar polymers. Macromolecules 1999,32, 8689. 

Figure 15. Catalyst precursors for the synthesis of syndiotactic polystyrene.

Single-site catalysts for the S5mthesis of isotactic polystryrene have been more difficult to develop than single-site catalysts for the synthesis of syndiotactic polystyrene. Only a few soluble, single-site catalysts are known that form highly isotactic forms of this polymer. 

In 1985, Ishihara et al. were successful in the synthesis of syndiotactic polystyrene (SPS) using cylopentadienyltitanium compounds with MAO [5]. This is the first known case of the syndiospecific polymerization of styrene. 

For comprehensive reviews, see (a) Po, R., Cardi, N. Synthesis of syndiotactic polystyrene Reaction mechanisms and catalysis. Prog. Polym. ScL, 21, 47-88 (1996). (b) Schellenberg, I, Tomotsu, N. Syndiotactic polystyrene catalysts and polymerization. Prog. Polym. Set, 27, 1925-1982 (2002). (c) Schellenberg, I. Recent transition metal catalysts for syndiotactic polystyrene. Progress Polym. Set, 34, 688-718 (2009). 

Po, R., Cardi, N. Synthesis of syndiotactic polystyrene Reaction mechanisms and catalysis. Prog. Polym. Set, 21,47-88 (1996). 

Xu, G., Chung, T. C. Synthesis of syndiotactic polystyrene derivatives containing amino groups. Macromolecules, 33,5803-5809 (2000). 

Half-metallocene complexes are included because they play an important role, particularly in the synthesis of syndiotactic polystyrene. Much interest in non-metallocene complexes of group 4 metals, Ni, Pd, Fe, and Co for polymerization catalysts has recently been shown. They will be described with regard to stereoregular polymerization. Ring-opening polymerization of lactones, lactams, and lactides is excluded in this chapter. Ring-opening metathesis polymerization (ROMP) has received much interest recently however, it is not discussed here because few metallocene complexes are used for ROMP. 

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