Hybrid acrylic/urethane colloidal dispersions were prepared by incorporation of a novel multifunctional urethane castor vinyl ether (UCVE) macromonomer derived from castor oil in acrylic latexes. Single-stage and two-stage semi-continuous emulsion polymerization processes were utilized to control placement of UCVE in colloidal dispersions with core/shell and spherical particle morphologies. While the single-stage process resulted in optically clear and chemically homogeneous films, the two-stage process led to heterogeneous film formation. Internal reflection infrared imaging (IRIRI) spectroscopic analysis of the film-air (F-A) interfaces revealed phase-separated urethane- and urea-rich domains ranging in size from approximately 4-40 mum. Based on these measurements, a model of film formation is proposed which incorporates the effect of exceedingly high shear conditions to achieve fine dispersions of UCVE. These experiments indicate that features of the single-stage process facilitate uniform dispersion of UCVE and efficient grafting between UCVE and the acrylic polymer matrix resulting in intimately mixed networks and homogeneous films. (C) 2004 Elsevier Ltd. All rights reserved.