Main observation and conclusion Phenols,instead of conventional alcoholic compounds,are used to initiate ring-opening polymerization (ROP) of ethylene oxide and propylene oxide in bulk at room temperature in cooperation with the recently prevailing bicomponent metal-free catalyst comprising an organobase and triethylborane.Experimental and DFT calculation results both point out that due to the lower nucleophilicity of the initiating (phenolate) species than the propagating (alcoholate) species,chain initiation is distinctly slower than propagation and the difference becomes even larger as the acidity of the phenolic initiator increases.Nevertheless,well-defined polyethers with ex-pected molar mass,low dispersity,and high end-group fidelity are afforded substantiating that the ROP is living/controlled in spite of the slow initiation.Evolution of product composition indicates that the reaction on alcoholates (i.e.,propagation) is effectively inhib-ited by the unreacted phenols during the initiation step because of the adequately large acidity difference,which is key to the success of the slow-initiation living/controlled polymerization.The acidity difference between phenol and alcohol also facilitates the fulfill-ment of highly selective phenolysis of epoxides,a "1 + 1" type addition reaction between phenol and epoxide (in excess) rather than the "1 + n" type ROP reaction,by use of a milder organobase and decreased Lewis acid/base ratio.
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