Various copolyesteramides were prepared by melt compounding at 220 degrees C involving reaction of poly(styrene-co-maleic anhydride), SMA, with 6, 17, and 28 wt % maleic anhydride content, and 1-dodecanol, C12OH, in the presence of 2-undecyl-1,3-oxazoline, C11OXA. Copolymer architectures were examined by means of H-1 NMR, FTIR, DSC, and TGA using model compounds prepared via solution reactions. While conversion of anhydride with alcohol was poor due to the thermodynamically favored anhydride ring formation, very high conversions were achieved when stoichiometric amounts of C11OXA were added. According to spectroscopic studies esteramide groups resulted from reaction of oxazoline with carboxylic acid intermediate. In the absence of alcohol, C11OXA reacted with anhydride to produce esterimides. Effective attachment of flexible n-alkyl side chains via simultaneous reaction of C12OH and C11OXA resulted in lower glass-transition temperatures of copolyesteramides.