Nucleophilic thiol-Michael chemistry and hyperbranched (co)polymers: synthesis and ring-opening metathesis (co)polymerization of novel difunctional exo-7-oxanorbornenes with in situ inimer formation

Nucleophile-initiated thiol-Michael chemistry was employed to prepare a series of mono- and di-functional exo-7-oxanorbornenes from the reaction between mono- or dithiols with 2-((3aR,7aS)-1,3-dioxo-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindol-2(3H)-yl)ethyl acrylate. Homopolymerization of the difunctional species, bis(2-((3aR,7aS)-1,3-dioxo-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindol-2(3H)-yl)ethyl)-3,3′-((1,4-phenylenebis(methylene))bis (sulfanediyl))dipropanoate (M1), with Grubbs' first generation catalyst, RuCl2(PCy3)2CHPh, yields a hyperbranched polymer with up to 90% of polymerizable CC bonds consumed as judged by 1H NMR spectroscopy. SEC analysis is consistent with the formation of a hyperbranched structure with an absolute weight average molecular weight (Mw), as measured by static light scattering in CH2Cl2, determined to be 381 000. Bis(2-((3aR,7aS)-1,3-dioxo-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindol-2(3H)-yl)ethyl)-3,3′-((thiobis(ethane-2,1-diyl))bis (sulfanediyl))dipropanoate (M2) could not be polymerized with the Grubbs' 1st generation catalyst but rapidly polymerized with 50% conversion of monomeric CC bonds with the Grubbs' 3rd generation species. Bis(2-((3aR,7aS)-1,3-dioxo-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindol-2(3H)-yl)ethyl)-7,10-dioxa-4,13-dithiahexadecane-1,16-dioate (M3), in a similar fashion to M1, could be readily homopolymerized to high conversion with the 1st generation species giving organosoluble material. The statistical copolymerization of M1 or M3 with a series of monofunctional monomers containing pyrrole, fluoro, POSS and fluorene functionality is demonstrated. Copolymers of variable composition are readily prepared with the Grubbs' 1st generation catalyst with, in general, CC bond conversions in excess of 90%. Finally, the preparation of novel linear-hyperbranched AB diblock copolymers is demonstrated via the sequential polymerization of a monofunctional sugar derivative, (2S,3S,4S,5R,6R)-6-((3-(2-((3aR,7aS)-1,3-dioxo-3a,4,7,7a-tetrahydro-1H-4,7-epoxyisoindol-2(3H)-yl)ethoxy)-3-oxopropyl)thio) tetrahydro-2H-pyran-2,3,4,5-tetrayl tetraacetate (M8) which yields a well-defined linear homopolymer, as judged by SEC, followed by chain extension with the difunctional substrate M3.