Free radical copolymerization of N,N‐dimethylaminoethyl methacrylate with styrene and methyl methacrylate: monomer reactivity ratios and glass transition temperatures

Abstract

Abstract BACKGROUND: The properties of copolymers depend strongly on their composition; therefore in order to tailor some for specific applications, it is necessary to control their synthesis, and, in particular, to know the reactivity ratios of their constituent monomers. Free radical copolymerizations of N , N ‐dimethylaminoethyl methacrylate (DMAEM) with styrene (ST) and methyl methacrylate (MMA) in toluene solution using 1‐di( tert ‐butylperoxy)‐3,3,5‐trimethylcyclohexane as initiator at 70 °C were investigated. Monomer reactivity ratios were determined for low conversions using both linear and nonlinear methods. RESULTS: For the DMAEM/ST system the average values are r 1 = 0.43 and r 2 = 1.74; for the DMAEM/MMA system the average values are r 1 = 0.85 and r 2 = 0.86. The initial copolymerization rate, R p , for DMAEM/ST sharply decreases as the content of ST in the monomer mixture increases up to 30 mol% and then attains a steady value. For the DMAEM/MMA copolymerization system the composition of the feed does not have a significant influence on R p . The glass transition temperatures ( T g ) of the copolymers were determined calorimetrically and calculated using Johnston's sequence length method. A linear dependence of T g on copolymer composition for both systems is observed: T g increases with increasing ST or MMA content. CONCLUSION: Copolymerization reactivity ratios enable the design of high‐conversion processes for the production of copolymers of well‐defined properties for particular applications, such as the improvement of rheological properties of lubricating mineral oils. Copyright © 2009 Society of Chemical Industry