Infrared spectra and sequence length distribution in free radical styrene/methacrolein copolymers

• DOI: 10.1002/macp.1973.021640123
• Publication Date: 2003-04-15T23:10:17Z
• Authors: Jaroslav Kálal; Milan Houska; Otakar Seyček; Petr Adámek
• Keywords: 01 natural sciences; 0104 chemical sciences

AbstractThe method of azoisobutyronitrile (AIBN)‐initiated bulk copolymerization of styrene (S) and methacrolein (M) was employed to determine the monomer reactivity ratios rS = 0.15 and rM = 0.55 (QM = 1.50, eM = 0.78). Quantitative IR spectroscopy in the region of 4000–450 cm−1 was used to elucidate the structure of copolymers. In addition to methacrolein units containing aldehyde groups, the copolymers may also contain cyclic hemiacetal structures formed by the reaction of the carbonyls of the neighboring methacrolein units. The carbonyl absorption at 1722 cm−1 showed that, up to 30 mole‐% methacrolein in the copolymer, almost all methacrolein units have free aldehyde groups. The number of cyclic structures increases with the concentration of methacrolein in the copolymer. The experimental data are in agreement with the statistical theory on the sequence length distribution. The shift of the styrene band at 540 cm−1 to higher wavenumber was investigated and related to the shortening of sequence length of the styrene units. The intensity of the styrene band at 760 cm−1 was related with the distribution of the MSM triads and the copolymer structure.