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Magnetic/hollow double-shelled imprinted polymers (MH-MIPs) were synthesized by Pickering emulsion polymerization. In this method, attapulgite (ATP) particles were used as stabilizers to establish a stable oil-in-water emulsion, and a few hydrophilic Fe3O4 nanoparticles were allowed to be magnetic separation carriers. The imprinting system was fabricated by radical polymerization in the presence of the functional and polymeric monomers in the oil phase. The results of characterization indicated that MH-MIPs exhibited magnetic sensitivity (Ms = 4.76 emu g(-1)), thermal stability (especially below 200 °C), and hollow structure and were composed of exterior ATP shells and interior imprinted polymers shells. Then MH-MIPs were evaluated as sorbents for the selective binding of λ-cyhalothrin as a result of their magnetism, enhanced mechanical strength, hydrophilic surface, and recognition ability. The kinetic properties of MH-MIPs were well described by the pseudo-second-order equation, indicating that the chemical process could be the rate-limiting step in the adsorption process for λ-cyhalothrin. The equilibrium adsorption capacity of MH-MIPs was 60.06 μmol g(-1) at 25 °C, and the Langmuir isotherm model gave a better fit to the experimental data, indicating the monolayer molecular adsorption for λ-cyhalothrin. The selective recognition experiments also demonstrated the high affinity and selectivity of MH-MIIPs toward λ-cyhalothrin over fenvalerate and diethyl phthalate.

Fe 3 O 4 /Halloysite nanotube magnetic composites (MHNTs) were firstly prepared via an effective polyol-medium solvothermal method, and then the surface of the MHNTs was endowed with reactive vinyl groups through modification with 3-(methacryloyloxy)propyl trimethoxysilane (MPS). Based on the MHNTs-MPS, temperature responsive and magnetic molecularly imprinted polymers (t-MMIPs) were further synthesized by adopting methacrylic acid (MAA) and N-isopropylacrylamide (NIPAM) as the functional monomer and temperature responsive monomer, respectively. The as-prepared t-MMIPs were characterized by FT-IR, TEM, TGA and VSM, which indicated that the t-MMIPs exhibit magnetic sensitivity (M s ¼ 2.026 emu g À1 ), magnetic stability (especially in the pH range of 4.0-8.0) and thermal stability and are composed of an imprinted layer. The molecular interaction between 2,4,5-trichlorophenol (TCP) and MAA was investigated by 1 H-NMR spectroscopy and ultraviolet absorption spectroscopy, which suggest that hydrogen bonding may be largely responsible for the recognition mechanism. The t-MMIPs were then applied to selectively recognise and release TCP molecules at 60 C and 20 C, respectively. The maximum amount of binding at 60 C was 197.8 mg g À1 and 122.6 mg g À1 for t-MMIPs and temperature responsive and magnetic non-imprinted polymers (t-MNIPs), respectively. At 20 C, about 32.3%-42.7% of TCP adsorbed by t-MMIPs was released, whereas 25.3%-39.9% of TCP was released by t-MNIPs. The selective recognition experiments demonstrated the high affinity and selectivity of t-MMIPs towards TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

CoFe 2 O 4 /halloysite nanotube magnetic composites (MHNTs) were firstly achieved via a wet impregnation technique, and then a thermal polymerization under (NH 4 ) 2 S 2 O 8 chain initiation in water was employed to obtain methacrylic acid-functionalized MHNTs (MAA-MHNTs). By decorating the MAA-MHNTs with the temperature responsive monomer N-isopropylacrylamide (NIPAM), a novel temperature responsive molecularly imprinted material based on the obtained NIPAM-MHNTs (TMMIPs) was synthesized by a surface imprinting technique. The results of characterization indicated that the TMMIPs exhibited magnetic sensitivity (M s ¼ 1.758 emu g À1 ), magnetic stability (in the pH range of 2.0-8.0), thermal stability (especially below 200 C) and contained a temperature responsive imprinted layer (the lower critical solution temperature was 33.96 C). Then the TMMIPs were applied to switched recognition and release of 2,4,5-trichlorophenol molecules (5-TCP) by changing the medium temperature. TMMIPs showed outstanding recognition ability towards the imprinted species under high temperature conditions (such as 60 C), due to the loss of hydration and a collapsed state of inter-poly(N-isopropylacrylamide), which resulted in the formation of a specific structure between 5-TCP and the polymer network. In contrast, at relatively low temperatures (such as 20 C), the captured 5-TCP was released from the swelled TMMIPs, which resulted from increasing the distance between 5-TCP and the polymer network. The selective analysis demonstrated the high affinity and selectivity of TMMIPs towards 5-TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional groups of the template molecules.

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