Mechanochemical polymerization of solid-state monomers was first reported in 1959. The earlier investigations of mechanochemical solid-state polymerization were conducted in the presence of inorganic activators such as NaCI, BaSO₄, and quartz, and years later, it has been shown that polyacrylamide and polymethacrylamide can be obtained in the absence of an activator by vibratory milling in metallic vessels. Nevertheless, relatively little work has been done with mechanochemical polymerization in the solid-state. This may be because most conventional vinyl monomers are liquid at room temperature. Recently Kuzuya et al. reported the first in-depth study of mechanochemical polymerization of specially synthesized solid-state monomers, methacryloyl derivatives of bioactive compounds including the detailed mechanistic implications. It has been shown that there exists a monomer selectivity for efficiency of mechanochemical polymerization, although all the monomers studied undergo conventional solution polymerizations using radical initiators. The mechanochemically polymerizable monomer gave the corresponding polymeric prodrugs essentially quantitatively. Thus, this method eliminates the need for any work up of the reaction mixture, which is required in liquid state. It has also been shown that the mechanochemical polymerization involves a mechanoradical-initiated polymerization as a dominant process, and if one appropriately designs the vinyl monomers along the line of the structural criteria derived from the quantum chemical considerations presented by us, one can make a variety of solid-state monomers undergo the mechanochemical polymerizations essentially quantitatively. One of the most striking properties observed in the resulting polymers is that these polymeric prodrugs are of very low heterogeneity (narrow molecular weight distribution) represented by Mw/Mn (Mw, weight-average molecular weight; Mn, number-average molecular weight) which is of great value in pharmaceuticals for highly functionalized polymeric prodrugs. Thus, the present reaction provides a novel and simple methodology for syntheses of polymeric prodrugs through a totally dry process.