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

摘要

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 and group; these knots gradually disintegrate with increasing temperarue and above 100 deg 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 intramolecualr interaction between an Oh end group and the adjacent C=C 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 of large clusters in bulk; these supramolecular structures are bound together not only by hydrogen bonds but also by interactions between the aliphatic chians. With increasing temperature, intermolecualr hydrophobic domains dissociate only for unsaturated polymers.