Preparation of aqueous two-phase systems composed of two pH-response polymers and liquid–liquid extraction of demeclocycline

Aqueous two-phase systems have potential applications for separation and purification of bioproducts in bio-industry. However, a key problem is the recovery of the polymers forming aqueous two-phase systems. In this study, two novel random copolymers (PADB and PADBA) were synthesized using acrylic acid, dimethylamino-ethyl methacrylate, butyl methacrylate and allyl alcohol as monomers and used to form pH response aqueous two-phase systems. The recoveries of PADB and PADBA are 97.18% and 98.87% and the pI of PADB and PADBA are 2.79 and 4.01, respectively. Demeclocycline was partitioned in the PADB/PADBA aqueous two-phase systems and the partition coefficient reached 0.085, in the presence of MgSO4 (60 mmol/L) at pH 5.28.