Biodegradable aliphaticaromatic copolyester nanohybrids, with polyhedral oligomeric silsesquioxane (POSS) moieties tethered between poly(lactic acid) (PLA) and poly(butylene terephthalate) segments, is designed and prepared. First, (bis(2-hydroxyethyl) dipropionate POSS, BH-POSS) is synthesized under mild conditions, then in situ polycondensation is carried out in the presence of terephthalic acid, PLA oligomer, 1,4-butanediol, and BH-POSS.1 H-NMR and Fourier transfer infrared spectroscopy confirm that Michael addition reaction of amino-POSS and hydroxyethyl acrylate takes place efficiently and forms BH-POSS in high yield at room temperature. Owing to similar functional groups, BH-POSS could be easily incorporated into the macromolecular chains and obtain final copolyester nanohybrids. Moreover, X-ray diffractometry and transmission electron microscopy observations demonstrate that POSS moieties occur self-assembly behaviors and form nanoaggregates with the diameter of 50100 nm. The thermal stability and mechanical properties of the copolyester nanohybrids containing BH-POSS are substantially improved. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012