Multi-scale characterization of bamboo bonding interfaces with phenol-formaldehyde resin of different molecular weight to study the bonding mechanism.

Understanding the bonding mechanism of the interfacial region between bamboo and adhesives is essential for accelerating the development of improved adhesives for advanced bamboo-based materials. In this study, Br-labelled phenol-formaldehyde (PF) resins with four different molecular weights (MWs) were used to make bamboo-adhesive interfaces for tracing the adhesives in bamboo. Ultra-depth-of-field microscopy and scanning electron microscopy in conjunction with energy dispersion spectrometry were used to access the distribution and penetration of resin in the bamboo polymer. Fourier transform infrared images and solid-state cross-polarization/magic angle spinning nuclear magnetic resonance spectra were used to access the molecular-scale interactions between PF resins and bamboo cell walls. The results showed that the PF resins with high MW infiltrated into the lumina of damaged bamboo cells near the bondline to form glue nails, while those with low MW penetrated into the bamboo cell wall to form nanomechanical interlocking. Chemical bonds and secondary forces such as polar forces and hydrogen bonds were generated between bamboo and PF resin. Finally, the twice-adhesive dispensing method combining low-MW resins with high-MW resins was used to improve the bonding strength of the interface.

Synthesis of 1D Fe3O4/P(MBAAm-co-MAA) nanochains as stabilizers for Ag nanoparticles and templates for hollow mesoporous structure, and their applications in catalytic reaction and drug delivery.

One-dimensional (1D) magnetic Fe3O4/P(MBAAm-co-MAA) nanochains were prepared by distillation-precipitation polymerization of MBAAm and MAA in the presence of Fe3O4 nanoparticles as building blocks under a magnetic heating stirrer, which played two critical roles: serving as magnetic field to induce the self-assembly of Fe3O4 nanoparticles into 1D nanochains and providing thermal energy to induce the polymerization of MAA and MBAAm on the surface of the Fe3O4 nanoparticles. The thickness of the P(MBAAm-co-MAA) layer can be easily tuned by adjusting the successive polymerization steps. The polymer layer that contained carboxyl groups was used as stabilizers for loading Ag nanoparticles and the reaction locus for deposition of outer silica layer via a sol-gel method in presence of C18TMS as the pore directing agent for tri-layer nanochains. The corresponding hollow mesoporous silica nanochains with movable maghemite cores (γ-Fe2O3@mSiO2) were produced after removal of the polymer mid-layer and the alkyl groups of the pore directing agent via calcination of the tri-layer nanochains at high temperature. The Fe3O4/P(MBAAm-co-MAA)/Ag nanochains exhibited a highly catalytic efficiency and well reusable property toward the reduction of nitrophenol. Furthermore, the γ-Fe2O3@mSiO2 nanochains possessed hollow mesoporous structure and high specific surface area (197.2 m(2) g(-1)) were used as a drug carrier, which displayed a controlled release property.

Synthesis of poly(methacrylic acid)-manganese oxide dihydroxide/silica core-shell and the corresponding hollow microspheres.

Poly(methacrylic acid)-MnO(OH)2/SiO2 core-shell microspheres were prepared by sol-gel hydrolysis of tetraethylorthosilicate (TEOS) in the presence of poly(methacrylic acid)-Mn(II) (PMAA-Mn(2+)) as template with ammonium hydroxide anion as catalyst and n-octadecyltrimethoxysilane (C18TMS) as pore-directing reagent. The PMAA-Mn(2+) core was prepared by incubation of Mn(2+) cations with PMAA microspheres via the coordination between carboxylate anion group on PMAA microsphere and Mn(2+) cations. During this process, the Mn(II) species were formed as white Mn(OH)2 precipitates at first, which were subsequently oxidized into brown MnO(OH)2 in air. The Mn2O3/mesoporous silica (Mn2O3/m-SiO2) double-shelled hollow microspheres (DSHMs) were prepared through calcination of the PMAA-MnO(OH)2/SiO2 core-shell microspheres at 600 °C for the selective removal of PMAA template and pore-directing organic component from C18TMS, during which the crystalline structure of DSHM was developed into Braunite-1Q via the reaction between Mn2O3 inner-shell and silica outer-shell by annealing the DSHMs under higher temperatures of 800 and 900 °C. The Mn2O3 hollow microspheres (HMs) were prepared through the selective removal of the silica layer from the DSHMs by sodium hydroxide aqueous solution, which exhibited structure integrity and good ethanol dispersity due to the presence of mesoporous structure.