Chiroptical Properties of Oligomers of m-Methylphenyl Isocyanate Bearing an Optically Active End-Group

Abstract

Oligomerization of m-methylphenyl isocyanate (mMePI) with lithium amide of (S)-(−)-2-(methoxymethyl)pyrrolidine (MMP) was carried out to obtain oligomers containing a chiral residue at the initial chain end (α-end). The oligomers of degree of polymerization (DP) less than eighteen were separated in terms of DP and the specific rotation of each oligomer was estimated. The oligomers showed the high optical rotation which is ascribed to the structure prevailing in one-screw sense. The specific rotation of the oligomers increased up to DP of twelve and then decreased with an increase in DP. This suggests that the DP corresponding to the average persistence length of single handed helix may be larger than twelve. The specific rotation of the polymers was inversely proportional to the molecular weight. The optical activity of the polymer greatly increased with a decrease in temperature, whereas that of the trimer was not influenced by temperature.