A new variation of precipitation polymerization is described wherein C-H bond addition to a triallyl monomer contributes to molecular weight growth, thereby incorporating a significant amount of saturated hydrocarbon into the solid phase. The extent of monomer oligomerization relative to hydrocarbon addition is shown to increase with the concentration of allyl benzoate in cyclooctane. An extension to the trifunctional monomer, triallyl trimesate, results in phase separation of hydrocarbon-monomer adducts to give a dispersed phase whose continued reactivity leads to crosslinked microspheres. The relationships between reaction conditions and solid-phase composition and morphology are discussed. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6561-6570, 2009