Poly(methyl methacrylate) (PMMA) was prepared through free-radical polymerization using BPO as the initiator. Size-exclusion chromatography and several NMR analysis methods
including
1
H-NMR
13
CNMR
DEPT135-NMR
heteronuclear multiple-bond correlation
and heteronuclear single quantum correlation NMR were used to analyze the structure of the end vinyl group from disproportionation termination to disclose the mechanism.
1
H-NMR measurement indicates that there are two NMR proton resonances at
δ
=6.20 and 5.47 ppm
the other NMR methods confirm that there is only one type of vinyl group formed from disproportionation and the transferred hydrogen radical comes from the side methyl group at the chain end. The polymerization behavior of the end vinyl group in PMMA provides further evidence to support the conclusion from NMR measurements. In addition
there is also marked primary termination besides disproportionation in the polymerization.