Synthesis of Macrocyclic Poly(ethylene oxide) and Polystyrene via Glaser Coupling Reaction

Abstract

Glaser coupling reaction of alkynyl groups was used as a new ring-closure technique to synthesize monocyclic poly(ethylene oxide) (PEO) and polystyrene (PS) successfully. The linear PEO with hydroxyl groups at both ends was prepared by ring-opening polymerization (ROP) of ethylene oxide (EO) using 2,2-dimethyl-1,3-propanediol and diphenylmethylpotassium (DPMK) as co-initiators, terminated by anhydrous methanol. The linear PS with hydroxyl groups at both ends was prepared by anionic polymerization using lithium naphthalenide as initiator and terminated by EO. The propargyl-telechelic precursors (l-PEO and l-PS) were then obtained by the reaction between hydroxyl-telechelic polymers (HO-PEO-OH and HO-PS-OH) and propargyl bromide in the presence of sodium hydride. The intramolecular cyclizations of the latter were carried out in the presence of Cu(I)Br/N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) under mild conditions with oxygen in the air as oxidant and the efficiency was as high as nearly 100%. T...