Recycling aqueous two-phase systems (ATPS) are hopeful application techniques in bioseparation and biocatalysis engineering areas. In this study, two novel light-sensitive and reversible water-soluble copolymers were synthesized and used in recycling ATPS. Polymer P(NBAC) was polymerized by using N-isopropylacrylamide (NIPA), n-butylmethacrylate (BMA), acrylic acid (AA) and chlorophyllin sodium copper salt (CHL) as monomers. Copolymer P(NDBC) was synthesized by NIPA, 2-(dimethylamino) ethylmethacrylate (DMAEMA), BMA and CHL as monomers. The synthesis yields of two copolymers are 66.9% and 77.2%, respectively. It can be calculated from (1)H NMR graph that the molar ratios of monomers in P(NBAC) (NIPA:BMA:AA:CHL) and P(NDBC) (NIPA:DMAEMA:BMA:CHL) was 82:4:1:10 and 16:4:3:1, respectively. They could be precipitated by laser irradiation in 488 nm with the least light density of 1.70 x 10(5) W/m(2). The precipitate energy is 1.79 kJ and 3.52 kJ/g, respectively. Five batches of average recoveries of two copolymers in the ATPS are 96.6% and 97.4%. BSA and L-phenylalanine were partitioned in the novel P(NDBC) P(NBAC) ATPS, and their partition coefficients were 2.1 and 0.52. By applying this ATPS to partition of penicillin, the best partition coefficient K is 4.25. (C) 2010 Elsevier Ltd. All rights reserved.