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Separation of Stereoisomers of Poly(methyl methacrylate) by High Performance Liquid Chromatography

Poly(methyl methacrylate) (PMMA) was separated by stereoisomerism using high performance liquid chromatography (HPLC). Using a cross-linked polyacrylonitrile gel as the stationary phase and a mixture of dichloromethane and n-hexane, ethyl ether, or benzene as the eluent, isotactic PMMA eluted faster than syndiotactic PMMA. With a cross-linked polystyrene gel and a mixture of dichloromethane and nitromethane, syndiotactic PMMA eluted earlier. With some eluent forming stereocomplex of PMMA after injecting a mixture of isotactic and syndiotactic polymers, the sample did not elute or eluted at a different elution time from that expected from an experiment of a separate injection. From the cloud point it was found that the separation was done by an adsorption mechanism rather than phase separation.