Chain structure of homogeneous ethylene-propylene copolymers showing inversion, described on the basis of 13C-NMR data. II. Application

✍ Scribed by V. B. F. Mathot; Ch. C. M. Fabrie; G. P. J. M. Tiemersma-Thoone; G. P. M. Van Der Velden

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 808 KB
• Volume: 28
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/polb.1990.090281305

✦ Synopsis

Abstract

For a series of homogeneous ethylene‐propylene copolymers with mole fraction ethylene (x~1~) ranging between 0.40 and 0.85, the inversion (I) independent propagation probabilities (P~ij~s) and reactivity ratios ( r~ij~s) and the methylene, ethylene, and propylene sequence length distributions have been determined from ^13^C nuclear magnetic resonance (NMR) data, using a first‐order Markovian terpolymer [ethylene (1), inverted propylene (2), and normal propylene (3)] model. For each sample, the limiting values of I (I~min~, I~max~) are given. Calculations of the common parameters for 19 samples show that the polymerization direction characterized by the r set and I is statistically more probable than the opposite direction, which is characterized by the r′ set and I′. Further, I = I~min~ appears to be close to the most probable value of I. The resulting r set is r~12~ = 119, r~13~ = 19.7 and, for I = I~min~, r~21~ = 0, r~31~ = 0.034, r~32~ = 2.98. In the limited range 0.60 < x~1~ < 0.85, there appears to be no preference for either polymerization direction, so that the solutions characterized by the r set and I = I~min~ and by the r′‐set and I = I′~max~, respectively, are about equally probable. If the copolymer reactivity ratios r~e~ and r~p~ are defined in the usual manner, it follows that for the limited range r~e~ = 17. In the model used here, r~p~ is found to be dependent on the ethylene‐propylene ratio in the reactor. Nevertheless, it can be stated that r~p~ ≅ 0.029 and r~e~ r~p~ ≅ 0.50.