Poly(malic acid) copolymers as degradable rheology modifiers in aqueous formulations

Polymeric rheological modifiers help tailor formulations to specific applications but many current technologies are poorly bio- or hydrolytically-degradable. This paper investigates the polycondensation of malic acid as an acid-rich branching monomer with lactic and glycolic acids to synthesise hydrophilic branched polyesters as potential formulation modifiers. The branching of the copolymers was characterised using quantitative 2D NMR spectroscopy and Mark-Houwink plots measured by gel permeation chromatography. The viscoelastic properties of the copolymers in solution were assessed within a shampoo formulation and showed increased viscosity and elastic behaviour compared to control samples. The formulations are hydrolytically degradable, with the performance of the shampoo formulations deteriorating over time.