A thin matrix network structure of poly (vinyl chloride), poly(P.-caprolactone), and in situ formed poly(methyl methacrylate) (PMMA) was synthesized. The structure was observed with scanning electron microscopy. The dissolution test suggested that a simple method to generate high rates of crosslinking at a lower temperature was obtained. The relationship of the phase morphology and mechanical properties of the blends was studied, and a reinforced material of PMMA was obtained. The obvious increase in the mechanical properties and the reinforcing effect were attributed to the formation of crosslinking and the network structure in the blend. The glass-transition temperatures, obtained by DSC, suggested confined thermal behavior of PMMA chains restricted by a crosslinking system. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 108:1044-1048, 2008.