Monomer Sequence Distribution Monitoring in Living Carbanionic Copolymerization by Real-Time 1H NMR Spectroscopy

Abstract

Detailed understanding of the monomer sequence distribution in carbanionic copolymerization was achieved by direct online monitoring of copolymerizations in an NMR tube. Obtaining detailed knowledge of the changing monomer concentration in stock during the reaction, this technique permits to determine the incorporation probability for each monomer at every position of the polymer chain. An in situ kinetic study of two different carbanionic copolymerizations has been carried out. On the one hand, the copolymerization of the structurally similar, protected hydroxystyrene derivatives, p-(1-ethoxy ethoxy)styrene (pEES) and 4-tert-butoxystyrene (tBuOS), and on the other hand the copolymerization of the chemically different monomers, styrene (S) and pEES, have been studied. Whereas in the first case a slight deviation from an ideal random copolymerization was observed, the latter copolymerization leads to gradient copolymers. Real-time 1H NMR spectroscopy gave detailed insight into the reaction behavior at every stage of the copolymerization and leads to precise understanding of the resulting gradient structures.