Syndiospecific polymerization of styrene. II. Monocyclopentadienyltributoxy titanium/methylaluminoxane catalyst

Abstract

SYNOPSIS Syndiospecific polymerization of styrene was catalyzed by monocyclopentadienyltributoxyThe atactic and syndiotactic polystyrenes were separated by extracting the former with refluxing 2-butanone. The activity and syndiospecificity of the catalyst were affected by changes in catalyst concentration and composition, polymerization temperature, and monomer concentration. Extremely high activity of 5 X lo7 g PS (mol T i mol S h ) -* with 99% yield of the syndiotactic product were achieved. The concentration of active species, [ C* 1, has been determined by radiolabeling. The amounts of the syndiospecific and nonspecific catalytic species, [ C: ] and [C:] respectively, correspond to 79 and 13% of the c p T i ( 0 B~)~. The rate constants of propagation for C: and C,* at 45OC are 10.8 and 2.0 ( M s)-', respectively, the corresponding rate constants for chain transfer to MA0 are 6.2 X 5 -l . There was no deactivation of the catalytic species during a batch polymerization. The rate constant of chain transfer with monomer is 6.7 X ( M s)-'; the spontaneous P-hydride transfer rate constant is 4.7 X lo-* s-'. The polymerization activity and stereospecificity of the catalyst are highest at 45"C, both decreasing with either higher or lower temperature. The stereoregular polymer have broad MW distributions, GW/M,, = 2.8-5.7, and up to three crystalline modifications. The T,,, of the s-PS polymerized at 0-90°C decreased from 261.8 to 241°C indicating thermally activated monomer insertion errors. The styrene polymerization behaviors were essentially insensitive to the dielectric constant of the medium.and 4.3 X ~~ * To whom a11 correspondence should be addressed. ' On leave from the Research Institute of Macromolecular Chemistry, BRNO, Czechoslovakia. EXPERIMENTALCpTi ( O B U )~ was synthesized by Wade's procedure' given for CpTi ( OPh)3. The methods for purification of materials, polymerization, active-site counting, and polymer characterizations were the same as detailed in Part I.' RESULTS Polymerization BehaviorsPolymerization of S (20 mL) in 40 mL of toluene at temperature (T,) of 60°C using 50 pmol of CpTi( O B U )~ and 0.29 g of MA0 ( [All / [ Ti] = 100) yielded 17.1 g of polymer for 94% conversion. The magnetic stirring bar ceased to function after just 5 min of polymerization time ( t p ) . In comparison, the Sci. Phys., B28,419 (1989). 20. V. Vittoria, F. de Candia, P. Iannelli, and A. Imminizi, Makromol. Chem. Rapid Commun., 9 , 765 ( 1988).

Syndiospecific living polymerization of 4-methylstyrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminium catalytic system

“…Since this discovery, several studies on syndiotactic polystyrene (SPS) have been carried out, focusing on the improvement of syndioselectivity and catalytic activity [7][8][9][10][11][12] as well as on the mechanistic studies on the syndiospecific propagation 13,14) . However, the living polymerization of syndiospecific polystyrene has never been demonstrated with such half-metallocene type catalysts.…”

Synthesis and characterization of elastoplastic poly(styrene-co-ethylene) using novel mono(?5-cyclopentadienyl) titanium and modified methylaluminoxane catalysts

“…Currently, mono( 5 -cyclopentadienyl)titanium complexes activated by MAO for syndiospecific polymerization of styrene are well known, [1][2][3][4][5] as well as for the polymerization of ethylene 6,7 and propylene. 8,9 The active species of mono( 5 -cyclopentadienyl)titanium/MAO catalyzing different monomers have been analyzed by various methods.…”

Multiple Injection Method for Bulk Syndiospecific Polymerization of Styrene with Homogeneous Metallocene Catalyst

“…Ishihara et al [1,2] first investigated the syndiospecific polymerization of styrene by organotitanium compounds with methylalumin -oxane(MAO) as a cocatalyst. Since then, many studies have been conducted on homogeneous catalysts producing sPS [3]. Several sPS polymerization methods have been introduced including solution polymerization [3], reaction injection molding [4,5], the bulk polymerization process [6,7], and slurry polymerization [8,9].…”

“…Since then, many studies have been conducted on homogeneous catalysts producing sPS [3]. Several sPS polymerization methods have been introduced including solution polymerization [3], reaction injection molding [4,5], the bulk polymerization process [6,7], and slurry polymerization [8,9]. Solution polymerization, generally performed in dilute media, is adequate for the study of intrinsic catalytic behavior in a homogeneous catalyst system.…”