Reactive processing of polymers: Structural characterisation of productsby~1H and~(13)CNMR spectroscopy for glycidyl methacrylate graftingonto EPR in the absence and presence of a reactive comonomer

摘要

Grafted GMA on EPR samples were prepared in a Thermo-Haake internal mixer by free radical meltgrafting reactions in the absence (conventional system; EPR-g-GMACONV) and presence of the reactivecomonomer divinyl benzene, DVB (EPR-g-GMADVB). The GMA-homopolymer (poly-GMA), a major sidereaction product in the conventional system, was almost completely absent in the DVB-containingsystem, the latter also resulted in a much higher level of GMA grafting. A comprehensive microstructureanalysis of the formed poly-GMA was performed based on one-dimensional 1H and 13C NMR spectros-copy and the complete spectral assignments were supported by two-dimensional NMR techniques basedon long range two and three bond order carbon-proton couplings from HMBC (Heteronuclear MultipleBond Coherence) and that of one bond carbon-proton couplings from HSQC (Heteronuclear SingleQuantum Coherence), as well as the use of Distortionless Enhancement by Polarization Transfer (DEPT)NMR spectroscopy. The unambiguous analysis of the stereochemical configuration of poly-GMA wasfurther used to help understand the microstructures of the GMA-grafts obtained in the two different freeradical melt grafting reactions, the conventional and comonomer-containing systems. In the graftedGMA, in the conventional system (EPR-g-GMACONV), the methylene protons of the GMA were found tobe sensitive to tetrad configurational sequences and the results showed that 56 of the GMA sequencein the graft is in atactic configuration and 42 is in syndiotactic configuration whereas the poly-GMAwas predominantly syndiotactic. The differences in the microstructures of the graft in the conventionalEPR-g-GMACONV and the DVB-containing (EPR-g-GMADVB) systems is also reported