A non-reactive monomer mixture contains a monomer component and a diaryl carbonate dispersed in the mixture. The monomer component includes one or more monomer compounds having a melting point below the melting point of the diaryl carbonate. The monomer component has less than 600 ppb alkali metal, an acid stabilizer, or both less than 600 ppb alkali metal and an acid stabilizer. The monomer compounds of the monomer component and the diaryl carbonate are present in a mole ratio of from 0.9 to 1.1. The monomer mixture is at a temperature between the melting temperature of the lowest melting monomer compound and less than 5° C. above the melting point of the diaryl carbonate.