STUDY OF THE PROPAGATION CENTER IN THE ANIONIC-POLYMERIZATION OF (METH)ACRYLIC MONOMERS - NMR AND MNDO STUDY OF THE COMPLEXES OF DI-TERT-BUTYL 2-LITHIO-2,4,4-TRIMETHYLGLUTARATE AND OF THE LIVING POLY(TERT-BUTYL METHACRYLATE) OLIGOMERS WITH LITHIUM-CHLORIDE

Interactions of living oligomers of tert-butyl methacrylate (tBuMA) wi th a Li counterion land of the model living dimer di-tert-butyl 2-lith io-2,4,4-trimethylglutarate (A) with LiCl (B) were studied in tetrahyd rofuran-d(delta) (THF-d(delta)) solution by Li-7, Li-6, H-1, and C-13, 1D and 2D, NMR spectroscopy. Di-tert-butyl 2-lithio-2,4,4-trimethylgl utarate is shown to form a 1:1 complex with lithium chloride in THF. 1 H, Li-7 NMR results suggest that a rapid equilibrium between free LiCl and the mixed complex takes place when the molar ratio LiCl:lithiated dimer is higher than 1. From C-13 relaxation times, a dimeric aggrega tion (i.e. A(2)B(2)) of the complex is deduced, in full accord with MN DO calculations. Preliminary results are presented for living tBuMA ol igomers prepared by initiation with diphenylhexyllithium in the presen ce of various amounts of lithium chloride. Fast-acquired C-13 NMR spec tra of the living ends were recorded using C-13-enriched monomer added at the end of the polymerization. Their structure is shown to be affe cted by the amount of LiCl added and to correspond to an equilibrium b etween free lithium chloride and a complexed end group. A higher exces s of LiCl apparently does not change the nature of the complexed livin g end. The oligomers exhibit marked self-termination in THF at 273 K. Finally, a correlation of the structure of the living chain ends with the macromolecular parameters of the resulting polymer is attempted.