Novel polyurethanes (PUs) grafted with methoxypolyethyleneglycol (mPEG) and lauric acid (LA) were synthesized by solution polymerization using dibutyl tin dilaurate as a catalyst, taking different molar ratios of LA-trimethylol propane (LA-TMP) with respect to mPEG.trimethylol propane (mPEG-TMP). The polymers obtained were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography to confirm, respectively, the PU formation and molecular weight. Moderate molecular-weight PUs were obtained, and nifedipine (NFD)-loaded microspheres were prepared by solvent evaporation method. The size of the microspheres as measured by laser light scattering technique ranged between 10 and 50 mu m. An increase in the size of particles was observed with an increasing molar ratio of mPEG-TMP with respect to LA-TMP. The % encapsulation efficiency was found to vary between 65 and 92. The surface morphology of microspheres as studied by scanning electron microscopy revealed the spherical nature of the particles with wrinkles on their surfaces. Crystalline nature of the drug in the microspheres after loading was studied by X-ray diffraction technique. The release of NFD through the matrix microspheres was investigated in pH-7.4 phosphate buffer. An increase in release rate was observed with increasing molar ratio of mPEG-TMP with respect to LA-TMP. (c) 2007 Wiley Periodicals, Inc.