ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Polymerization of α-methylstyrene was carried out in the presence of AlEt3-TiCl4 at -78°C. The activity of the catalyst and the degree of polymerization were affected by the AlR3/TiCl4 molar ratio, the mixing and the aging conditions of catalyst, and the kinds of solvent. The advantageous AlR3/TiCl4 molar ratio was found to be between 1.0 and 1.2; at ratios higher than 2.0 the polymerization did not proceed. For this catalyst to have enough activity, the mixing and the aging of catalyst must be carried out below room temperature, and the valence state of titanium must be kept between IV and III after the reaction between AlEt3 and TiCl4. From comparison of the present results with other catalyst systems it is speculated that the polymerization reaction by this catalyst system is cationic, and that its active species are the intermediate complex [(TiCl3)+-(AlEt3Cl)-] and the reaction product AlEt2Cl. This speculation is confirmed by the molecular weight distribution curves of the poly-α-methylstyrene obtained, measured by a column fractionation method. The distribution curves have two maxima, at molecular weights of about 5 × 104 and 65 × 104. This suggests that two kinds of active species are present, in agreement with the above hypothesis. The resultant poly-α-methylstyrene shows superior stereoregularity, compared with that prepared with other catalyst systems.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1963.100010718
