Application of ketenes to well‐defined polyester synthesis. III. Living anionic polymerization of ethyl(4‐methoxyphenyl)ketene—Development of polyester having masked phenol side chain

Abstract

A novel ketene, ethyl(4-methoxyphenyl)ketene (EMPK), was synthesized by the dehydrochlorination of 2-(4-methoxyphenyl)butanoyl chloride. The anionic polymerizations of EMPK by butyllithium in tetrahydrofuran at Ϫ20°C were carried out with a varying feed ratio to give the corresponding polyesters having predictable molecular weights and narrow molecular weight distributions, quantitatively. The selective formation of the polyester was confirmed by IR analysis, and the reductive degradation of the polymer was supported by lithium-aluminium hydride. The second feed of the monomer (after the first stage of polymerization) resulted in the formation of the polymer with the expectedly increased molecular weight and low polydispersity to strongly support the living mechanism of this polymerization.

Formation of a living anionic oligomer of ethylphenylketene on polystyrene beads and its application to the solid‐supported synthesis of poly(methyl methacrylate)

“…By a comparison of the intensity of the UV‐detected peak of 6 with that of 4 , the initiation efficiency for the polymerization of MMA was estimated to be 0.17. In our previous study, a similarly low efficiency was also observed in the solution‐phase block copolymerization of EPK with tert ‐butyl methacrylate 16. These low initiation efficiencies in polymerizations of methacrylates by oligo‐EPK and PEPK anions might be caused by the much greater rate of propagation of methacrylate compared with that of initiation under these conditions.…”

“…In our previous study, a similarly low efficiency was also observed in the solution-phase block copolymerization of EPK with tert-butyl methacrylate. 16 These low initi- ation efficiencies in polymerizations of methacrylates by oligo-EPK and PEPK anions might be caused by the much greater rate of propagation of methacrylate compared with that of initiation under these conditions. Although the block efficiency was still low and must be improved, 6 was easily separated from 4 by precipitation with diethyl ether.…”

“…In particular, such an application of living anionic polymerization has been reported only by us 12. Here we report a new system for the solid‐supported anionic synthesis of polymethacrylate based on our technique of living anionic polymerizations of ethylphenylketene (EPK)13, 14 and its related compounds (Scheme ) 15, 16. The system involves the anionic oligomerization of EPK on a crosslinked polystyrene resin by the solid‐supported lithium alkoxide 1 to afford the corresponding solid‐supported oligoester bearing lithium enolate at its terminal, which initiates the polymerization of methacrylate 15–17.…”

“…Here we report a new system for the solid‐supported anionic synthesis of polymethacrylate based on our technique of living anionic polymerizations of ethylphenylketene (EPK)13, 14 and its related compounds (Scheme ) 15, 16. The system involves the anionic oligomerization of EPK on a crosslinked polystyrene resin by the solid‐supported lithium alkoxide 1 to afford the corresponding solid‐supported oligoester bearing lithium enolate at its terminal, which initiates the polymerization of methacrylate 15–17. Furthermore, because the formed polymer is anchored on the resin with benzyl ester, its selective cleavage under acidic conditions releases the polymethacrylate from the resin without destroying its side‐chain methyl ester 12…”

The emerging utility of ketenes in polymer chemistry

“…(A)] . This methodology was extended to gain access to functional, phenyl substituted vinylester polymers through the polymerization of substituted ethylphenyl ketene derivatives . Further, changing the nature of both the nucleophilic initiating group or the electrophilic end‐capping group during the polymerization could access hetero‐bifunctional polymers .…”