Initiator/Stabilizer FAQs

Determination of monomer reactivity is not always obvious or straightforward. Researchers rely on their experience and published data on individual monomers. In general, extent of conjugation in the molecular structure can be viewed as indicative of its tendency to form the initial free radical required for propagating a freeradical polymerization. Usually, a more conjugated system is more likely to undergo free-radical polymerization.

To inhibit polymerization during storage, many monomers are provided with a stabilizer as indicated by the label. Usually, it is not necessary to remove stabilizers. They are typically present in ppm level, and the use of a free radical initiator at the polymerization temperature will overwhelm the effect of the stabilizer. In worstcase scenarios, one may need to add extra amounts of initiator to sustain an acceptable polymerization rate. In most cases, once a polymerization initiates, the rate can be sustained without much difficulty. If, however, it is absolutely necessary to remove the stabilizer, column chromatography is the preferred method (for inhibitor removal columns, see products 306312, 311332, 306320).

It is a common practice to dissolve the polymers in a solvent prior to end use, followed by precipitating the polymer using a cosolvent. Usually, the residual initiators and stabilizers will remain in solution and the polymers will separate out as a solid (powder, gum, or fibers). This process may be repeated until desirable polymer characteristics are obtained. This fractional precipitation is also effective in removing lower molecular weight polymers, resulting in narrower molecular weight distribution—of course accompanied with a loss of yield. Typical solvent/cosolvent pairs could be toluene/hexane, toluene/methanol, THF/water, etc., determined by the relative solubilities of the polymer versus the small-molecule component.

For initiator solubilities and decomposition temperatures, visit our website.