A new acid-labile polymer having acetal moieties in the main chain was synthesized by polycondensation of poly (ethylene glycol) (PEG) and lilial, an aldehyde widely used in fragrance applications. The hydrophobicity of the resulting acetal moiety and the hydrophilicity of the PEG chain allowed the polyacetal to exhibit amphiphilicity. The polyacetal derived from PEG having weight average molecular weight (M-w) of 1000 (PEG1000) was soluble in water and self-associated to form associates in water. The polyacetals were hydrolyzed in acidic aqueous solutions to release hydrophobic lilial from the systems. The release rate of aldehyde from the polyacetal derived from PEG1000 was higher than that from the polyacetal derived from PEG having M-w of 400 (PEG400). These results supported that the release rate of lilial can be controlled by the chain length of PEG, on which hydrophilicity of polyacetal depends. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 596-602, 2011