The copolymer composed with acrylamide (AM) and N,N-dimethylacrylamide (DMAA) was prepared by using inverse emulsion polymerization with sorbitan monooleate (SPAN-80) as emulsifier,white mineral oil as oil phase,and ammonium persulfate (APS) and tetramethylenediamine (TEMED) as redox initiation systems. The product was characterized by hydrogen nuclear magnetic resonance spectroscopy. Firstly,the relationship between polymerization rate (rp) and monomer feed molar ratio was studied in the range of n(DMAA):n(AM)=1:100 to 1:25. The results showed that the polymerization rate increased with increasing the DMAA in feed molar ratio and the amount of DMAA structural unit in the resultant copolymer was higher than that in the recipe. By comparing with conventional emulsion polymerization,there was no constant rate period ( i.e.,interval Ⅱ) according to the behavior of polymerization rate versus time,suggesting that the mechanism for particle nucleation (i.e.,formation of polymer particles) might be dominated by monomer droplet nucleation. Then a variety of hehaviors were studied for the polymerization rate versus monomer concentration (cM,14.42—16.00 mol/L),initiator concentration (cI,0.0043—0.0081 mol/L),and emulsifier concentration (cE,0.200—0.234 mol/L) at 296.15 K. The polymerization rate equation was rp=kcM1.74cI0.82cE0.77,indicating that monomer concentration had the greatest effect on the polymerization rate among the behaviors investigated. Finally,the apparent activation energy of 20.53 kJ/mol for the inverse emulsion polymerization of AM and DMAA was obtained by Arrhenius formula in the range of 288.15—301.15 K.
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