Linping Zhang

Cellulose Sponge Supported Palladium Nanoparticles as Recyclable Cross-Coupling Catalysts

Robust and flexible cellulose sponges were prepared by dual-cross-linking cellulose nanofiber (CNF) with γ-glycidoxypropyltrimethoxysilane (GPTMS) and polydopamine (PDA) and used as carriers of metal nanoparticles (NPs), such as palladium (Pd). In situ growth of Pd NPs on the surface of CNF was achieved in the presence of polydopamine (PDA). The modified sponges were characterized with FT-IR, XRD, EDX, SEM, TEM, and TGA. XRD, EDX, and TEM results revealed that the Pd NPs were homogeneously dispersed on the surface of CNF with a narrow size distribution. The catalysts could be successfully applied to heterogeneous Suzuki and Heck cross-coupling reactions. Leaching of Pd was negligible and the catalysts could be conveniently separated from the products and reused.

Optimization of Conditions for Nanocrystal ZnO in-situ Growing on SiO2-Coated Cotton Fabric

Nano ZnO crystal in-situ growth on SiO2 nano sol-coated cotton fabric via a reaction between Zn(NO3)2 and (CH 2)6N4 through a low-temperature hydrothermal method was studied. The effects of hydrothermal reaction conditions and SiO 2 nano sol coating on the size and crystalline perfection of nano ZnO, and the UV protection property of the fabric were investigated. The optimal treatment conditions for the highest Zn content and the best ZnO crystalline perfection on the fabric surface were obtained. Under optimal conditions, the cotton fabric was covered with 25 to 30 nm diameter ZnO crystallites and had an excellent UV-blocking property.

Facile fabrication of redox/pH dual stimuli responsive cellulose hydrogel

A cellulose-based multi-responsive hydrogel was prepared by the facile incorporation of enamine and disulfide bonds in the same system at physiological pH. The cellulose hydrogel was obtained by simply mixing aqueous solutions of cellulose acetoacetate (CAA) and cystamine dihydrochloride (CYS) at room temperature. The internal morphology, structure, and mechanical properties of the cellulose hydrogel were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopies, nuclear magnetic resonance (NMR), and water retention, porosity, and rheology measurements. The cellulose hydrogel showed reversible sol-gel transitions in response to both pH and redox triggers. In addition, it displayed good stability under physiological conditions. Gels loaded with small molecules showed variable release properties in response to pH or redox stimuli. The preparation protocol presented here could be used to fabricate other multi-responsive polysaccharide hydrogels.

A novel low add-on technology of dyeing cotton fabric with reactive dyestuff:

A novel low add-on dyeing process of cotton fabric with C.I. Reactive Black 5 has been implemented successfully with the assistance of dye-jet ejector units to produce precise wet pick-up ranging from 20% to 50%. The steaming process of the low add-on technology was investigated through evaluating the effects of relative humidity, steaming temperature, steaming time and water ratio on the surface temperature of the wet fabric and their influence on the dye properties, as well as the effect of the wet pick-up on dye properties. The optimal dyeing process was also conducted, including build-up properties and the concentrations of the alkaline agent and the electrolyte via the evaluation of the color strength (K/S value) and dye fixation rate. A comparison was made between the novel low add-on dyeing process and conventional dyeing process by assessing the dye properties, color shade and color levelness. The results indicated that the fabric dyed with the low add-on process had excellent washing fastness, rubbing fastness, a similar color shade and superior levelness in comparison with conventional one-bath pad-steam dyeing.

Thiol–ene click reaction on cellulose sponge and its application for oil/water separation

Thiol–ene click reaction was employed to synthesize a flexible hydrophilic cellulose sponge. The reactive vinyl group was introduced by silanization treatment with vinyl-trimethoxysilicane (VTMO), and the resulting silylated cellulose sponge (SCS) can be subsequently functionalized with various thiol-containing compounds such as 3-mercaptopropionic acid, via temperature induced thiol–ene reactions. The hydrophilic cellulose sponge thus prepared displayed an excellent mechanical strength of 70 KPa at 80% compression strain. The prepared sponge features hydrophilic and underwater oleophobic properties and was used in gravity-driven removal of oil from oil-in-water emulsions and oil/water mixtures with a high separation efficiency. The separation efficiency remained 100% after 10 cycles for an oil/water mixture and 95% after 6 cycles for an oil-in-water emulsion.

Biodegradable regenerated cellulose-dispersed composites with improved properties via a pickering emulsion process

Reinforcement of biodegradable polymers with nanocellulose is attractive yet the effectiveness is often compromised by uneven dispersion. In this work, a general method of preparing reinforced biodegradable composites using regenerated cellulose (RC) was developed. From an oil-in-water Pickering emulsion of PLA/methylene chloride stabilized with RC, uniformly dispersed RC/PLA composites was obtained. The resulting RC/PLA composites showed enhanced crystallization and tensile strength of up to 34% compared with the native PLA, while the transmittance in the visible range remained above 70%. The Pickering emulsion-based composition procedure is simple, environment friendly and cost effectively, which could be applied to preparation of other RC-reinforced biodegradable composites.

Facile synthesis of cellulose derivatives based on cellulose acetoacetate

In the present work, cellulose acetoacetates (CAA) was used as a precursor for preparing diversely functionalized cellulose derivatives. Four amino-bearing compounds, namely hexylamine (HA), l-glutamic acid (Glu), cysteine (Cys), and tyramine (TA) were reacted with acetoacetyl groups providing alkyl-, carboxyl-, thiol-, or phenolic functionalized cellulose. The reaction was conducted under mild conditions without catalysts and UV light. The products were characterized with FT-IR, NMR and solubility measurement. 1H NMR measurement demonstrated the conversion of acetoacetyl groups were ideal, and all the cellulose derivatives demonstrated good solubility in certain solvent. Besides, CAA held a good stability under room temperature. This approach offers broad possibilities for developing new cellulose based materials. Moreover, this protocol can also be applied to fabricate other polysaccharide derivatives.

Infrared stealth property study of mesoporous carbon-aluminum doped zinc oxide coated cotton fabrics:

Low-emitting cotton fabric with low infrared emissivity near to 0.795 at the wavebands of 8–14 µm was prepared using mesoporous carbon-aluminum doped zinc oxide (C-AZO) coatings. The effects of binders, the content of C-AZO composites, coating thickness and roughness of fabrics on the infrared emissivity were investigated. Results showed that the emissivity firstly decreased, and then gradually reached a stable and lowest value as the content of C-AZO composites and coating thickness increased. The lowest infrared emissivity of coated fabric was obtained when the content of C-AZO composites was around 40 wt% with coating thickness over 300 µm. Moreover, infrared transparent binders and a smooth surface were found to reduce the infrared emissivity. The coated fabric with infrared emissivity of 0.795 could be matched in the surroundings of withered grass or rock under the condition of no sunshine.

Preparation and characterization of thermal protective aluminum hydroxide aerogel/PSA fabric composites

In this work, aluminum hydroxide aerogel was successfully assembled on polysulfonamide fabrics by sol–gel forming method to improve the thermal insulation and flame resistance properties. The presence of aluminum hydroxide aerogels assembled on the surface of polysulfonamide fabrics was verified by the scanning electron microscopy. The aerogel was crystalized in γ-AlOOH boehmite form characterized by X-ray powder diffraction. The heat insulation and flame resistance of polysulfonamide fabrics were improved by coating aluminum hydroxide aerogels. When the molar ratio of propylene oxide to aluminum chloride hexahydrate was 4:1, the prepared aluminum hydroxide aerogel marked as SAl-2 had the largest pore volume with the value of 2.33 cm3/g, the corresponding apparent density was 0.172 g/cm3, the specific surface area was 392 m2/g, the average pore diameter was 18.6 nm, and it gave the best thermal insulation property. Compared with the original polysulfonamide fabric, the thermal conductivity of the composite fabric was decreased from 0.0513 to 0.0301 W/(m·K). When the molar ratio of propylene oxide to aluminum chloride hexahydrate was 3:1, the prepared aluminum hydroxide aerogel marked as SAl-1 had the smallest pore volume with the value of 0.72 cm3/g, the corresponding apparent density was 0.645 g/cm3, the specific surface area was 293 m2/g, the average pore diameter was 10.9 nm, and it gave the best flame resistance property. Compared with the original polysulfonamide fabric, the vertical burning damage length was shorted from 4.90 to 1.30 cm.Graphical abstract

Copper-loaded nanocellulose sponge as a sustainable catalyst for regioselective hydroboration of alkynes

It is desirable for catalyst supports to be biodegradable, easily-modifiable, and possessing high surface area. In this work, thiolated nanocellulose sponge was prepared from hydrolytic silane condensation of cellulose nanofibrils (CNF) and used as a green support to immobilize copper cations via in situ CuII to CuI reduction and complexation. The sponge featured high porosity (90.5%) and low density (29.4 mg/cm3) with regular morphology. The sponge easily recovered 94% of its original shape in water after experiencing 80% deformation under stress of 95 kPa. When used in catalyzing hydroboration of alkynes, excellent conversion and up to 99% regioselectivity were achieved with the copper-loaded sponge. The sponge-supported catalysts worked well in the absence of additional ligands, had a broad substrate scope, and retained 93% of their activity after six catalytic cycles. This simple and scalable strategy offers an efficient route for immobilizing metal catalysts on porous supports.