Preparation of ''sugar-coated'' homopolymers and multiblock ROMP copolymers

Ring-opened homopolymers of 5-norbornene-2-carboxylates or 5-norbornene-2,3-dicarboxylates that contain acetal-protected sugars (1: 1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranos-6-O-yl 5-norbornene-2-carboxylate; 2: bis(1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranos-6-O-yl) 5-norbornene-trans-2,3-dicarboxylate; 3: 5-norbornene-2-carboxylic acid ester containing 2,3-O-isopropylidene-D-ribonic gamma-lactone; 4: 3,4:5,6-di-O-isopropylidene-alpha-D-mannofuranos-1-O-yl 5-norbornene-2-carboxylate) were prepared in toluene using Mo(CHCMe(2)Ph)(N-2,6-i-Pr2C6H3)(O-t-Bu)(2) as the initiator. These homopolymers showed narrow molecular weight distributions (PDI = 1.02-1.25) and a molecular weight dependent on the number of monomers added. Di-, tri-, and tetrablock copolymers containing 1-4, methyltetracyclododecene (MTD, 5), or trans-2,3-bis(((trimethylsilyl)oxy)methyl)-norborn-5-ene (6) were also prepared and found to have low polydispersities (M(w)/M(n) = 1.03-1.25). The cyclic acetal in polymers containing 1 or 2 could be removed using CF3CO2H/H2O (9/1 v/v, 15 min, 22 degrees C) to afford the corresponding water-soluble polymers containing the parent sugar.