In:
Die Makromolekulare Chemie, Wiley, Vol. 191, No. 8 ( 1990-08), p. 1765-1774
Abstract:
Restriction of β‐elimination in polystyrene‐lithium (PSLi) in the block copolymerization of polystyrene with poly(ethylene‐ co ‐propene) catalyzed with PSLi/TiCl 4 (resulting in sample A‐2) by adding a spacer of a few monomeric units of isoprene (I) (PS‐I n Li/TiCl 4 ( n ≤ 3)); resulting in sample A‐3), was evidenced by a M̄ w / M̄ n ‐value of 2,67 lower than that of sample A‐2, and a crystallinity (χ) of 7,4% in the poly(ethylene‐ co ‐propene) (EPR) block in sample A‐3. These, together with shorter ethylene (E)‐sequences EEE n≥1 , 27,6%) and a higher content of inverted propylene units ( P ) make the EPR‐block in A‐3 look like a polymer obtained with a soluble vanadium catalyst. This is due to the solubilization of the active centers by the PS chains. Higher M̄ w / M̄ n ‐values (4,23) and crystallinity of the EPR block (18,3%) and longer EEE n≥1 sequences (55,4%) in the case of sample A‐2 make it to look like a typical polymer as obtained with a heterogeneous Ti‐catalyst. Comparison of sample A‐3 with that obtained by E‐P copolymerization with BuLi/TiCl 4 (sample A‐1) corroborates the solubilization effect of PS in A‐3 and the effects of the typical heterogeneous catalyst used for the preparation of A‐1, showing up in EEE n ≥1 (A‐1: 63,4% A‐3: 27,6%), M̄ w / M̄ n (A‐1: 35,7; A‐3: 2,67) and P̄ (A‐1: nil; A‐3: 4%).
Type of Medium:
Online Resource
ISSN:
0025-116X
,
0025-116X
DOI:
10.1002/macp.02.v191:8
DOI:
10.1002/macp.1990.021910803
Language:
English
Publisher:
Wiley
Publication Date:
1990
detail.hit.zdb_id:
1475026-0
Bookmarklink