Shuwen Hu

Fabrication of dual-responsive cellulose-based membrane via simplified surface-initiated ATRP.

An independently temperature- and pH-responsive membrane was developed by simultaneously grafting poly(N-isopropylacryamide) (PNIPAAm) and poly[(2-(diethylamino)ethyl methacrylate] (PDEAEMA) from different sides of a crosslinked cellulose membrane. The synthesis was simplified by using surface-initiated activators regenerated by electron transfer for atom-transfer radical polymerization in a diffusion device. The grafted membrane was heterostructured. The grafted polymer layer thickness was linearly related to reaction time. The wettabilities of the double-membrane sides responded individually and reversibly to temperature and pH. The surface grafted with PNIPAAm shifted from hydrophilicity to hydrophobicity above the lower critical solution temperature. The PDEAEMA side was hydrophilic in acidic aqueous solution and hydrophobic under basic conditions. This dual-response cellulose membrane has potential applications in water treatment, separations, and other membrane applications.

Long-alkane-chain modified N-phthaloyl chitosan membranes with controlled permeability.

A series of N-phthaloyl acylated chitosan membranes with controlled permeability were synthesized by the regioselective protection of the chitosan amino groups as the corresponding phthalimides followed by reaction with the long-chain dodecanoyl chloride. Fourier transform infrared (FT-IR) and (1)H nuclear magnetic resonance ((1)H NMR) analysis suggested that the degree of substitution (DS) ranged from 2.8 to 3.6. Contact angles, water retention values and mechanical examinations demonstrated that the hydrophobicity and mechanical properties of the membranes were all improved significantly following the modifications, together with their solubility in many organic solvents. Thermal weight change analysis demonstrated that a higher DS provided enhanced thermal properties. The controlled permeability of the membranes was determined by measuring the diffusion of urea, and the amount of urea released decreased significantly with increasing DS. The comprehensive properties of the membranes could be tuned by regulating their DS values as required.

Enhancement of the Controlled-Release Properties of Chitosan Membranes by Crosslinking with Suberoyl Chloride

A novel crosslinking agent, suberoyl chloride, was used to crosslink N-phthaloyl acylated chitosan and improves the properties of chitosan membranes. Membranes with different crosslinking degrees were synthesized. The derivatives were characterized by Fourier transform infrared spectroscopy and 13C solid state nuclear magnetic resonance spectroscopy, which indicated that the crosslinking degrees ranged from 0 to 7.4%. The permeabilities of various plant nutrients, including macroelements (N, P, K), microelements (Zn2+ and Cu2+), and a plant growth regulator (naphthylacetic acid), were varied by moderate changes in crosslinking degree, indicating that the controlled-release properties can be regulated in this way. The film-forming ability of native chitosan was maintained, whilst mechanical properties, hydrophobicity and controlled permeability were improved. These dramatic improvements occurred with a small amount of added suberoyl chloride; excessive crosslinking led to membranes with unwanted poor permeability. Thus, both the mechanical properties and permeability of the crosslinked membrane can be optimized.

Preparation and characterization of a novel imidacloprid microcapsule via coating of polydopamine and polyurea

Encapsulation of pesticides with polymeric materials is a promising approach to improve the efficacy of pesticide application and reduce the potential risks of pesticides to the environment and humans. In this study, a novel imidacloprid microcapsule was prepared by depositing a polydopamine (PDA) layer on imidacloprid via oxidative self-polymerization followed by a polyurea (PU) layer on PDA via copolymerization. No organic solvent or surfactant was used in the preparation process. The entrapment rate of imidacloprid was determined to be 47.28 ± 0.87%, and the pesticide loading of microcapsule was 68.36 ± 1.13%. Several characterization assays, such as Fourier infrared transform analysis, thermogravimetric analysis and contact angle analysis, were conducted to confirm the encapsulation of imidacloprid. Dynamic light scattering showed that the microcapsule size ranged from hundreds of nm to several μm, which was similar to the results obtained by scanning electron microscopy. The microcapsule had a stable dispersion up to one month in the aqueous solution. Moreover, the microcapsule was able to release imidacloprid in a sustainable manner, as the release was much slower than the non-encapsulated imidacloprid.

Fluorescence turn-on of salicylaldimine ligands by co-ordination with magnesium and amines

A new fluorescence enhancement mechanism based on Schiff base ligand and magnesium complexation is established. The co-ordination number of the Schiff base ligand–magnesium complex (2 : 1) can be tuned to 1 : 1 in the presence of amines to induce significant fluorescence enhancement. Using this approach, a novel and easily available fluorescent chemosensor was designed, which showed highly selective recognition toward magnesium and amines in ethanol.

Synthesis of a fluorescent ethyl cellulose membrane with application in monitoring 1-naphthylacetic acid from controlled release formula

A triple-functional (chemical release properties, physical release properties, and monitoring 1-naphthylacetic acid (NAA) release) ethyl cellulose (EC) membrane, modified with fluorescein 1-naphthylacetic acid ester (FNE) and isophorone diisocyanate (IPDI), was prepared (designated as IECF membrane). Fourier transform infrared analysis was conducted to confirm the grafting of FNE to the EC backbone. The chemical and physical release properties of IECF membrane were investigated. The chemical release traits of NAA were related to the hydrolysis of FNE of IECF membrane which was influenced by the NAA concentration at pH 7.2. The physical release traits of NAA were determined by the permeation of NAA from IECF membrane. So IECF membrane has a considerable ability to form a controlled release formula for coating NAA. Furthermore, the hydrolysis of FNE was associated with the recovery of fluorescent intensity of IECF membrane, making the membrane have the ability to monitor low concentration of NAA.