A new chemical modification of liquid polybutadiene by radical addition of model aldehydes (butanal and hexanal) onto pending vinyls of the polymer is described. The dibenzoyl peroxide/N,N-dimethylaniline redox system was shown to initiate the hydroacylation more efficiently than the thermal decomposition of 2,2'-azobis(2-methylpropanenitrile) because it gives higher conversions (content of hydroacylated monomer units, as determined by NMR) without forming crosslinks or microgels. Typically, the former source of radicals gives the content of modified units as high as 13% related to all monomer units, while the latter only 2-6%. Repeated introduction of the redox system into the reaction mixture resulted in an increased content of the acyl groups. (c) 2008 Wiley Periodicals, Inc.