Determination of molecular characteristics of cispolybutadiene rubbers by NMR spectroscopy

Abstract

With the use of nuclear magnetic resonance (NMR) spectroscopy (at an Larmor frequence of 600 MHz for proton resonance) and gel-permeation chromatography (GPC), the industrial polybutadiene rubbers with high cis-1,4-units content produced on neodymium and cobalt-containing catalytic systems were studied. An analysis has been made of the NMR spectra (both 1H and 13C) for different types of deuterated solvents and concentrations of solutions. As a result, the structure of terminal units and the equivalent weight (molecular weight per terminal group) of test butadiene rubbers were determined. From viscometry equipped GPC data — the branching parameter and from NMR data — the number-averaged molecular weights were also calculated. It is shown that in the package with viscometry equipped GPC data, modern 1H and 13C NMR spectroscopy offers scope for ascertainment of results for determining molecular-weight-distributions. Refs 15. Figs 3. Tables 2.