A xanthate derived photoinitiator, S-methacryloyl O-ethyl xanthate (MAX) bearing an electron-deficient polymerizable double bond has been found to be capable of distinguishing MMA and styrene, thereby dictating their polymerization pathways in distinctly different and controlled fashion. The structure, molecular weight, and the polydispersity of each polymer have been determined by spectral analysis and size-exclusion chromatography (SEC).