Kinetics and scale inhibition application studies towards bulk and RAFT copolymerization of maleic anhydride and acrylic acid

Poly(maleic anhydride) (PMA) is commonly reckoned as a better water scale inhibitor than poly(acrylic acid) (PAA) since each maleic anhydride unit can supply two carboxylic acid groups. However, pure PMA is difficult to achieve because the steric effect of its monomer MA. Herein, we synthesize copoly(MA-AA) copolymer by bulk polymerization method (bulk-copoly(MA-AA)), which avoids the use of any solvents which have to be removed afterwards. In addition, we also synthesize copoly(MA-AA) by reversible addition-fragmentation chain transfer (RAFT) polymerization method to afford RAFT-copoly(MA-AA) with low polydispersity index (PDI) less than 1.2, and the performance of RAFT-copoly(MA-AA) in water scale inhibition is more excellent relative to bulk-copoly(MA-AA). We also synthesize other copoly(MA-AA) copolymers by varying the molar ratio of MA to AA to study the polymerization mechanism. Through the static scale inhibition experiment, it is concluded that when the concentration of copoly(MA-AA) is 80 mg/L, the scale inhibition performance of RAFT-copoly(MA-AA) can reach 96.50 % which is the best among the control samples. It is also found that only 1:1 alternating copolymerization of MA and AA could be achieved as demonstrated by ¹H nuclear magnetic resonance spectra of the copolymers, evidencing the strong steric hindrance of MA for its homo-polymerization.