AbstractRenewable resources have been utilized to control the degree of crosslinking during ring‐opening metathesis polymerizations (ROMP). In this regard, the addition of monoterpenes to thermosets created a sustainable method for adjusting the physical properties and thermal stability. A number of monoterpenes with alkenes were examined as monofunctional reactants. The presence of these monoterpenes, such as β‐pinene, during the ROMP of dicyclopentadiene altered the degree of crosslinking and plasticized the thermoset. The resulting physical properties were tailored to obtain desired modulus and glass transition (Tg) temperatures. The influence of time, temperature, weight percent β‐pinene, and different metathesis catalysts was examined by dynamic mechanical analysis, thermogravimetric analysis, and FTIR spectroscopy. A comparison of β‐pinene with other monoterpenes, such as carvone, limonene oxide, myrcene, and d‐limonene, resulted in a reactivity profile for this general method. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011