Addition of difluorocarbene to 1,4 - polybutadienes. Synthesis and characterization of novel copolymers.

Difluorocarbene, generated under mild neutral conditions, adds cleanly to 1,4 - cis- and trans-polybutadienes to give cyclopropanated materials with complete retention of the double bond configuration. The addition can be effected to any desired degree of conversion by controlling the molar ratio of carbene precursor to the double bond, thus providing a series of novel copolymers. These fluorine-containing materials were characterized by thermal analysis, gel-permeation chromatography and high-field H-1, C-13, and F-19 NMR spectroscopy. The olefinic carbon resonances give the most detailed fine structure, which has been fully assigned to monomer sequence pentads. The addition of difluorocarbene takes place randomly to give a perfectly Bernoullian monomer sequence distribution, as well as an atactic stereosequence distribution.