Fig. 2

a Magnetization curves at 300 K of Fe₃O₄ NPs and P₁, P₂, P₃ and P₄ hybrid copolymers with various PAA and PMAEFC chain lengths; b change in zeta potentials of hybrid copolymers with pH; and c and d CV curves of c various hybrid copolymers at a scanning rate of 0.01 V s⁻¹ and d typical P₃ hybrid copolymer at different scan rates from 0.01 to 0.05 V s⁻¹ in THF solution of 0.1 M (CH₃CH₂CH₂CH₂)₄N(PF₆) at 25 °C (the inset shows plots of peak currents i _p vs the square root υ^1/2 of the scan rates). For b–d the concentration of the copolymer is 2 mg ml⁻¹