Vazo™ Free Radical Initiator: Benefits and Uses

Vazo FRS (Vazo free radical initiator ) is a Miller-Stephenson exclusive product line of diazo-compounds designed to be used as free radical initiators for a variety of polymerization, halogenations, addition, and crosslinking reactions.  Diazo-compounds decompose via photolysis or thermally to yield two free radicals per molecule and one equivalent of nitrogen gas. Vazo free radical initiators are cost-effective, efficient polymerization initiators and radical halogenation agents.

Diagram 1: Photolysis of VAZO 64 (AIBN)

The thermal decomposition temperature at which diazo-compounds will begin this process is dictated by the aliphatic chain and stability of the resultant nitrile-radical. Vazo FRS compounds which have a low thermal decomposition temperature will be more reactive and generate more free radicals at a given temperature than a variant with a higher thermal decomposition threshold.  For the compounds, Vazo 64 (AIBN) has a 10hr half-life at 64 degrees Celsius, while Vazo 88 has a 10hr half-life at 88 degrees Celsius and so on.  To ease our customers to distinguish which Vazo free radical initiator variant will work for their synthetic pathway, the number associated each FRS analogue indicates its 10hr half-life at that temperature.

Another widely used radical initiator are peroxides.  Peroxides can come as liquid or solid, depending on their chemical structure and, like diazo-compounds, will undergo thermal or light-induced decomposition to generate free radicals.  Peroxides are widely used for a variety of polymerization reactions, however they also have significant chemical and safety drawbacks, in comparison to Vazo. Peroxides are extremely shock sensitive and can detonate on impact, they also can induce free radical decomposition, and are extremely temperature sensitive.  In comparison to the equivalent peroxide (based on similar half-lives) initiator, Vazo does not exhibit any of these dangerous safety concerns.  From a synthetic perspective, peroxides facilitate higher polydispersion, increased crosslinking and branching, higher viscosity, increased by-product formation, lower control on monomer distribution and high oxidation potential versus the equivalent Vazo initiator.  Moreover peroxides are extremely sensitive to heavy metal contamination, pH variation, additives, and solvent choice.  Vazo initiators experience non of these drawbacks, and maintains predictable reactivity independent of solvent choice, pH, contamination, and pigments.  Also, unlike peroxides, FRS initiators are only mild oxidizing so polymerizations with oxidation-susceptible functionality can be performed.

Of interest to any chemical engineer is the cost effectiveness of each reagent chosen for their process. In addition to polymerization control benefits, many Vazo FRS grades have low molecular weights.  On a cost per mol (e.g. cost per pound) basis, Vazo FRS are frequently more cost effective than conventional organic peroxides.  Moreover variants come as safer, low-dust “noodle” forms. Vazo noodles present minimal risk of dust blow back during product addition, and are easier to handle than typical granular products.

From a reactivity, efficiency, cost-effectiveness, and most importantly safety aspect Vazo FRS ( Vazo free radical initiator ) is a clear improvement to any chemical process currently using peroxide-based initiators or engineers looking to use a safer and higher purity diazo-compound.

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The recommendation made here with and the information set forth with respect to the performance or use of our products are believed, but not warranted to be accurate. The products discussed are sold without warranty, as to fitness or performance, express or implied and upon condition that purchasers shall make their own test to determine suitability of such products for their particular purposes. Likewise, statements concerning the possible uses of our products are not intended as recommendations to use our products in the infringement of any patent.