The hydroxyalkylation of urea and N,N'-bis(2-hydroxypropyl)Urea (BHPU) with propylene carbonate (PC) was studied by spectral analysis of oligomeric products using H-1-NMR, IR and MALDI ToF methods. During the hydroxypropylation the carbonate groups in a product are partially preserved. Additionally, the hydroxypropyl groups of urea derivatives undergo partially dimerization to give carbamate groups. The obtained derivatives posses enhanced thermal stability. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3917-3925, 2008