Crystallization of side chains in copolymers of ethylene and 1-alkenes

Abstract

The phase structure of random copolymers of ethylene and ethylene-d4 with 1-octadecene and other 1-alkenes has been investigated. CPMAS 13C NMR spectra show that a fraction of the central sections of C16H33 side chains in ethylene-d4 copolymers are in ordered environments at 298 K. They give rise to resonances from 32.9 ppm to 33.8 ppm, which show that they are in trans conformations; T1C values for this group of resonances range from 1 s to 7 s. The remaining side chains are in an amorphous environment, the internal methylenes having a chemical shift of 30.8 ppm and a T1C close to 0.4 s. A Raman band at 1062 cm−1 in the spectrum of an ethylene-d4-1-octadecene copolymer is consistent with partial crystallization of side chains. Some side-chain crystallization also occurs in a 1-tetradecene copolymer. X-ray diffraction studies suggest that smaller side chains do not crystallize to a significant extent at 298 K. © 1996 John Wiley & Sons, Inc.