DETECTION OF MICROSTRUCTURE VARIATIONS IN POLY ALPHA-METHYL STYRENE BY DENSITY GRADIENT ULTRACENTRIFUGATION

It has been demonstrated that the various tactic forms of poly α-methyl styrene can be distinguished by measurement of polymer density or partial specific volume. Density gradient ultracentrifugation has been shown to be a useful and sensitive technique for detecting such differences, but the results emphasize the necessity to use the method for comparative rather than absolute determination of the apparent specific volume ν2αa. Differences in ν2α of 0·0094 cm3/g between atactic and highly syndiotactic poly α-methyl styrene were observed in a benzene-bromoform gradient, but the use of a methyl cyclohexane-1-iodo-octane gradient was marred by excessive preferential adsorption. The variation of ν2α with molecular weight for atactic poly α-methyl styrene in toluene could be represented by ν2α = 0·880 + 40·1/M. © 1969.