Synthesis and Characterization of Poly(acrylic acid) Produced by RAFT Polymerization. Application as a Very Efficient Dispersant of CaCO₃, Kaolin, and TiO₂

Abstract

Poly(acrylic acid), PAA, was prepared by controlled radical polymerization with reversible addition−fragmentation chain transfer. Using trithiocarbonic acid dibenzyl ester, 1, and trithiocarbonic acid bis(1-phenylethyl) ester, 2, as chain transfer agents (CTA), the polymerization is controlled for low ratios [AA]:[CTA]. At higher ratios, the polymerization is plagued by transfer to solvent. Transfer to polymer is also detected at high conversion, as shown by the presence of branches in NMR spectroscopy. In its neutralized form, PAA chains are not all terminated by a thiol end group, as shown by elemental analysis, thiol titration, and MALDI TOF MS. Finally, dispersion of CaCO3, kaolin, and TiO2 using these PAA reveals that the dispersion characteristics are significantly improved using low-polydispersity PAA.