Frank-Olaf Mähling

Dimerization of acrylic acid and of methacrylic acid in supercritical ethylene

The dimerization of acrylic and of methacrylic acid in dilute solutions of supercritical ethylene was investigated via FTIR-spectroscopy in the region of the CO stretching fundamentals. Concentrations of monomers and of hydrogen bonded dimers at temperatures up to 175 °C and pressures to 2500 bar were derived by deconvoluting the measured absorbance spectra with a band simulation program. For methacrylic acid, the carbonyl absorption spectra were decomposed into a monomer and a dimer component from which the pressure-dependent enthalpy of dimerization ΔHo = −(46.7 − 2.49 • p/kbar) kJ mol−1 and the temperature-dependent dimerization volume ΔVo = (5.7 − 0.069 • T/°C) cm3 mol-1 were calculated. For acrylic acid additional absorption components occur as a consequence of s-cis-/s-trans-iso-merism. The pressure-dependent enthalpy of dimerization is found to be: ΔHo = −(44.5 − 1.85 p/kbar) kJ mol-1.

Quantitative IR spectroscopic analysis of ethylene-acrylate copolymers

Abstract An IR spectroscopic technique for the quantitative analysis of composition of three ethylene (E)-acrylate copolymer systems (poly(ethylene- co -methyl acrylate), poly(ethylene- co -butyl acrylate), poly(ethylene- co -2-ethylhexyl acrylate)) is presented. Based on a simple model which explicitly considers vibrational band intensities characteristic for CH and for C O, copolymer composition may be derived from the ratio of C and CH integrated absorbances with a precision of ± 3 mol %. The optical path length of the copolymer samples which are subjected to IR analysis as pressed films need not be known.