Structural and Physicochemical Properties of a Polymerizable Surfactant Synthesized from N-Methylol Acrylamide

Modification Mechanisms and Properties of Poplar Wood via Grafting with 2-Hydroxyethyl Methacrylate/N,N'-methylenebis(acrylamide) onto Cell Walls

As the only renewable resource among the four basic materials (steel, cement, plastic, wood), wood itself and wood products have a "low carbon" value and play an important role in storing carbon. The moisture absorption and expansion properties of wood limit its application scope and shorten its service life. To enhance the mechanical and physical properties of fast-growing poplars, an eco-friendly modification procedure has been used. This was accomplished by the in situ modification of wood cell walls by vacuum pressure impregnation with a reaction of water-soluble 2-hydroxyethyl methacrylate (HEMA) and N,N'-methylenebis(acrylamide) (MBA). The anti-swelling efficiency of HEMA/MBA-treated wood was improved (up to 61.13%), whereas HEMA/MBA-treated wood presented a lower weight-gain rate (WG) and water-absorption rate (WAR). It was observed that the modulus of elasticity, hardness, density, and other properties of modified wood had improved significantly, as indicated by XRD analysis. Modifiers diffuse primarily within cell walls and cell interstices of wood, causing crosslinks between the modifiers and the cell walls, reducing its hydroxyl content and blocking the channels for water movement, thereby enhancing its physical properties. This result can be obtained by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX), Nitrogen adsorption test imaging ATR-FTIR (Attenuated total reflection-Fourier-Transform Infrared) Spectroscopy, and nuclear magnetic resonance (NMR) and Nitrogen adsorption test. Overall, this straightforward, high-performance modification method is crucial for maximizing wood's efficiency and the sustainable development of human society.

Synthesis, surface activities and aggregation properties of asymmetric Gemini surfactants

A series of Gemini surfactants with an asymmetric structure (PKO 15-3(OH)-n; n = 12, 14 and 16) were synthesized through a simple two-step reaction consisting of a ring-opening reaction followed by a quaternization reaction. The surface tension measurements indicated that the surface activities of PKO 15-3(OH)-n were higher than those of traditional single-chain and symmetrical Gemini surfactants. The thermodynamic parameters obtained from electrical conductivity measurements showed that the micellization processes of PKO 15-3(OH)-n were spontaneous and entropy-driven. Transmission electron microscopy and dynamic light scattering measurements confirmed that PKO 15-3(OH)-n molecules with a higher asymmetric degree could form vesicles, in which surfactant molecules were interdigitated side-by-side in the vesicle membrane. The obtained results are not in accordance with those calculated from the critical packing theory, which can further complement the theory.