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

Background: 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 non-linear methods. Results: For the system DMAEM / ST the average values were as follows: r1 = 0.43 and r2 = 1.74, and for the system DMAEM / MMA: r1 = 0.85 and r2 = 0.86. The initial copolymerization rate, Rp, 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. In the DMAEM / MMA copolymerization system the composition of the feed did not have a significant influence on Rp. The glass transition temperatures (Tg) of the copolymers were determined calorimetrically and calculated by Johnston’ s sequence length method. The linear dependence of Tg on copolymer composition for both systems has been observed, where Tg is increasing with ST or MMA content increase. Conclusion: Copolymerization reactivity ratios enable design of high conversion processes for the production of copolymers of well-defined properties for particular application, such as improvement of rheological properties of lubricating mineral oils.

N, N-dimethylaminoethyl methacrylate ; free radical copolymerization ; reactivity ratios ; glass transition temperature

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