Kinetic analysis of RAFT and free radical copolymerization

Fluence Analytics and its academic research partner Tulane PolyRMC collaborated on a peer review article for Polymer Journal which describes the kinetic analysis of continuous reaction data for RAFT and free radical copolymerization with acrylic and styrenic monomers. Free radical and RAFT copolymerization rates for styrenic monomers in bulk and aqueous reactions were accelerated by acrylic comonomers, whose own rates were both delayed and decreased. The effect was found with styrenics as low as 0.6% by mole and is directly observable from ACOMP data. Rapid radical transfer from acrylic to styrenic comonomer, through lower energy radical resonance stabilization in styrenics, was the suspected cause. FR and RAFT rates were equal, suggesting that FR termination controlled radical concentrations and rates. While rates were identical, molecular weights showed the characteristic increase with conversion for RAFT and decrease for FR. A new, generalized method for reactivity ratio determination was found and acceleration/deceleration behavior was consistently interpreted.

As a real-time online technique for continuous polymer characterization during a reaction, ACOMP relies on continuous extraction of small amounts of reactor content that go through dilution and other appropriate conditioning to reach analytical grade before flowing through the detector train, which is customizable and can include a variety of detectors. Characteristics of the reaction and polymer can be gathered during synthesis; monomer conversion and average and instantaneous copolymer composition with data from UV absorption, Mw and instantaneous Mw from a multi angle static light scattering (MALS), and intrinsic viscosity (IV) and reduced viscosity (RV) from capillary viscometry. More recently, a control interface (CI) was developed, and by using a semi-batch approach, the ACOMP/CI enables fully automatic feedback control of polymerization reactions. One of the main aims of this work is to explore RAFT copolymerization so that the ACOMP/CI composition controller can be used to create any desired composition gradient for RAFT and other ‘living type’ copolymerizations.

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