Quantitative analysis of sequence length distribution of 1,2 units in polybutadienes by ozonolysis-GPC method

The sequence distribution of 1,2 units in commercial and laboratory produce d polybutadienes, containing 1,2 units from 0.5 to 87%, was analyzed by an ozonolysis-GPC method. Ozonides from polybutadiene were converted to triflu oroacetates by reduction with LiAlH4, followed by esterification with trifl uoroacetic anhydride. The trifluoroacetates derived from 1,4-1,4 and 1,4-(1 ,2)(n)-1,4 sequences, from n = 1 to 7, were observed as respective GPC peak s using an refractive index detector. The relative intensities of these pea ks were converted to the concentration of each sequence by using correction factors determined with model compounds and by direct weighing of each pea k. Polybutadienes prepared by anionic polymerization showed a sequence dist ribution of 1,2 and 1,4 units corresponding to Bernoulian statistics, where as the 1,4-(1,2)(2)-1,4 sequence was significantly higher than the theoreti cal value for 1,2 units in cis-1,4 polybutadiene.