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Quantitative NMR Spectroscopy and Determination of Polymer Microstructure of Ethylene‐Styrene and Ethylene‐Isobutylene Co ‐Polymers
Author(s) -
Kasalo Ruzica,
Busch Markus
Publication year - 2013
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201200070
Subject(s) - isobutylene , ethylene , polymer chemistry , styrene , monomer , polymerization , chain transfer , polymer , materials science , branching (polymer chemistry) , chemistry , copolymer , organic chemistry , radical polymerization , catalysis
Summary: Quantitative 13 C NMR spectroscopy is used to determine reactivity ratios and end group and branching frequency of ethylene‐styrene and ethylene‐isobutylene co ‐polymers synthesized at a temperature T = 205 °C and pressure p = 1650 bar at different levels of co ‐monomer fraction. In the forefront of the studies quantitative 13 C NMR conditions have to be investigated. Optimum conditions are achieved using a relaxation agent Chromium(III) acetylacetonate (Cr(acac) 3 ) at measurement temperature T = 100 °C and a delay time d 1 = 7 s with a 90° pulse and inverse‐gated decoupling. The analysis of conversion dependence of co ‐monomer content shows an increase in conversion with increasing co ‐monomer content for the ethylene‐styrene co ‐polymerization, whereas conversion decreases with rising isobutene fraction in the co ‐polymer. Reactivity ratios for ethylene‐styrene as well as for ethylene‐isobutylene co ‐polymerization system are determined with values r ES = 0.09 ± 0.007 and r SE = 2.3 ± 7.0 and r EIB = 3.3 ± 0.6 and r IBE = 6.3 ± 4.2. Frequency on methyl end groups, end‐of‐chain contributions caused by transfer to propionic aldehyde and butyl branches are gained. For the ethylene‐styrene co‐ polymer system a decrease in frequency is observed, whereas for the ethylene‐isobutylene co ‐polymer system the opposite occurs. Influence of the co ‐monomers on the polymerization reaction steps as transfer to chain transfer agent and backbiting reaction is discussed.