Supramolecular Structures of Low-Molecular-Weight Polybutadienes, as Studied by Dynamic Light Scattering, NMR and Infrared Spectroscopy

Abstract

Three types of low-molecular-weight polybutadienes (bearing no or primary or secondary hydroxy groups on both chain ends), as well as their hydrogenated analogues, were studied by 1H NMR and IR spectroscopies and by dynamic light scattering. In bulk and at room temperature, hydroxylated polymers form hydrophilic microdomains (knots) based on hydrogen bonds between two or more OH end groups; these knots gradually disintegrate with increasing temperature and above 100 °C, only OH/OH pairs can be present, as is seen from IR spectra. Fixation of more than two chain ends in a single knot leads to the spatial restriction of the segmental motion of the chain links which manifests itself by the broadening of 1H NMR bands. With unsaturated, hydroxylated polymers, an intramolecular interaction between an OH end group and the adjacent CC bond of the terminal monomer unit is possible which makes the formation of the intermolecular OH/OH bonding less probable. The dynamic light scattering method revealed the presence ...