A GEL-PERMEATION CHROMATOGRAPHY METHOD TO DETERMINE GRAFTING EFFICIENCY DURING GRAFT-COPOLYMERIZATION

A new method of measuring the efficiencies of free radical grafting re actions is presented. This technique utilizes the compositional analys is capability of dual-detector (ultraviolet and refractive index) gel permeation chromatography (g.p.c.) in which the mixture of polymers re sulting from the graft copolymerization reaction is also subjected to separation by molecular size. Samples of the reaction mass drawn from a reactor are diluted with g.p.c. eluent and injected directly into th e chromatograph without any other preparative step. Grafting efficienc y, graft ratio, molecular weight distributions and the frequency of gr aft chains along the backbone polymer are simultaneously determined. L ow molecular weight diluents (residual monomer, solvent, initiator, et c.) are readily separated from the polymer within the chromatograph, a llowing for the determination of the fractional conversion of graft mo nomer (to grafted and ungrafted polymer) from the same analysis. This simple technique overcomes the need to separate or purify the polymer mixture prior to analysis, as required for most other methods. Experim ental results are presented for the grafting of styrene onto cis-polyb utadiene. Gelled samples cannot be analysed by this new technique.