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Detailed understanding of the monomersequence distribution incarbanionic copolymerization was achieved by direct online monitoringof copolymerizations in an NMR tube. Obtaining detailed knowledgeof the changing monomer concentration in stock during the reaction,this technique permits to determine the incorporation probabilityfor each monomer at every position of the polymer chain. An in situkinetic study of two different carbanionic copolymerizations has beencarried out. On the one hand, the copolymerization of the structurallysimilar, protected hydroxystyrene derivatives, p-(1-ethoxy ethoxy)styrene (pEES) and 4-tert-butoxystyrene (tBuOS), and on the other hand thecopolymerization of the chemically different monomers, styrene (S)and pEES, have been studied. Whereas in the firstcase a slight deviation from an ideal random copolymerization wasobserved, the latter copolymerization leads to gradient copolymers.Real-time 1H NMR spectroscopy gave detailed insight intothe reaction behavior at every stage of the copolymerization and leadsto precise understanding of the resulting gradient structures. [ABSTRACT FROM AUTHOR]