Ring-Opening Metathesis Polymerization Using Alkenyl Sulfides as Chain-Transfer Agents: Efficient Routes to Unsymmetrical Poly(norbornene)-Based Macroinitiators Bearing a Terminal Hydroxy Group

Convenient routes to hydroxy-terminated poly(norbornene)s (PNBEs) have been developed. Hydroboration of PNBEs bearing a terminal vinyl group with 9-BBN followed by oxidation with H 2 O 2 /NaOH forms hydroxy-terminated PNBEs in high yields. The parent PNBEs are prepared by ring-opening metathesis polymerization (ROMP) of norbornene using vinylic sulfides as chain-transfer agents (CTAs). On the other hand, ROMP of norbornene using ( Z )-1-phenylthio-1-propen-3-ol as a CTA causes one-step synthesis of ω-hydroxy-terminated PNBE, where the molecular weight of polymer depends linearly on the initial feed ratio of CTA to monomer. Similarly, ROMP reactions using ( Z )-1-phenylthio-1-propen-3-ols having bromo, amino, and 4-(chloromethyl)benzamido substituents at the para position of the phenyl group as CTAs afford the corresponding α,ω-heterodifunctionalized (heterotelechelic) PNBEs. The resulting PNBEs serve as macroinitiators for anionic ring-opening polymerization (AROP) of ε-caprolactone and atom-transfer radical polymerization (ATRP) of styrene, giving AB- and ABC-type block copolymers.