Microstructure of Styrene Methyl Methacrylate Copolymers Grafted ontoPolybutadiene Seeds

摘要

An investigation aimed at a better understanding of the emulsion copolymerizationof styrene and methyl methacrylate onto polybutadiene seed particles is described. Major relevant aspects of emulsion graft copolymerization are discussed. The determination of the intramolecular microstructure by proton Nuclear Magnetic Resonance (NMR) is described. The new peak assignment of the methoxy protons of styrene methyl methacrylate copolymers developed is confirmed by two dimensional NOESY (Nuclear Overhauser Effect Spectroscopy) NMR measurements. Due to the limited application of proton NMR to determine the intramolecular microstructure of styrene methyl methacrylate copolymers, the assignments of the carbon-13 NMR spectra are discussed. The free radical copolymerization models are critically examined and verified by measuring triad sequences by carbon-13 NMR. Experimental results and theoretical verification of the monomer partitioning experiments are discussed. The composition drift of grafted and free copolymer is studied in batch polymerizations. The copolymer composition, copolymer compositional distribution, the molecular weight, the degree of grafting, and grafting efficiency are obtained. The batch and semicontinuous graft polymerizations are investigated. The results comprise crucial information in terms of the degree of grafting, copolymer composition and compositional distribution and morphology, as a function of variation in the process conditions.