The effect of covalent surface immobilization on the bactericidal efficacy of a quaternary ammonium compound

This study investigates the effect of surface immobilization on the bactericidal function of a quaternary ammonium compound. Quaternary ammonium silane (QAS) coated planar surfaces did not produce any measurable mortality of Staphylococcus aureus, while 1 µm QAS‐coated microparticles did produce S. aureus mortality. The experiments using QAS‐coated microparticles indicate that the ability of QAS molecules to disrupt the cell wall is not hindered by covalent immobilization of QAS to a surface. These results provide evidence that S. aureus cells on a QAS‐coated planar surface are not exposed to a sufficient number of QAS molecules to produce significant mortality. This result has important implications for the development of self‐decontaminating coatings. Covalent immobilization is used to prevent leaching of the bactericidal compound. However, covalent immobilization may result in a significant tradeoff in bactericidal performance. Published in 2007 by John Wiley & Sons, Ltd.     

Coaxial electrospinning core-shell fibers for self-healing scratch on coatings

Polystyrene (PS) fibers with core-shell structure were prepared by coaxial electrostatic spinning using liquid epoxy or curing agent as the core and PS solution as the shell. Scratch self-healing coatings were realized by using the healant-loaded core-shell fibers in the matrix.     

Radiation formation of polymeric nanogels

An alternative method of synthesis of polymeric nanogels is proposed, based not on polymerization, but on intramolecular crosslinking of polymer chains, initiated by pulse irradiation in dilute aqueous solutions. Kinetic data show that for many water-soluble polymers irradiation under these conditions result in intramolecular crosslinking. Preliminary product studies on poly(vinyl alcohol) indicate that in fact internally crosslinked macromolecules can be obtained by this technique.     

Highly stretchable and self-healing hydrogels based on poly(acrylic acid) and functional POSS

Herein, we present a novel way for the production of self-healing hydrogels with stretch beyond 4200% than their initial length and relatively high tensile strength(0.1?0.25 MPa). Furthermore, the hydrogel was insensitive to notch. Even for the samples containing V-notches, a stretch of 2300% was demonstrated. The hydrogels were developed by in situ crosslinking of the self-assembled colloidal poly(acrylic acid)(PAA)/functionalized polyhedral oligomeric silsesquioxane(POSS) micelles. This was achieved by the addition of functionalized polyhedral oligomeric silsesquioxane with tertiary amines and hydroxyls(POSS-AH) into the PAA reaction solution. The POSS-AH led to micellar growth, then the dualcrosslinked network was constructed. One type of crosslink was formed by hydrogen-bonding and ionic interactions between PAA chains and POSS-AH, the other type of crosslink was formed by covalent bonds between PAA and bis(N,N'-methylenebis-acrylamide).     

Modulation of Self-healing of Polyion Complex Hydrogel by Ion-specific Effects

We have prepared polyion complex (PIC) hydrogel consisting of poly(3-(methacryloylami no) propyl-trimethylamonium chloride) and poly(sodium p-styrenesulfonate) polyelectrolytes via a two-step polymerization procedure and have investigated specific ion effects on the selfhealing of the PIC hydrogel. Our study demonstrates that the mechanical properties of the PIC hydrogel are strongly dependent on the type of the ions doped in the hydrogel. The ion-specific effects can be used to modulate the self-healing efficiency of the PIC hydrogel. As the doped anions change from kosmotrops to chaotropes, the self-healing efficiency of the PIC hydrogel increases. A more chaotropic anion has a stronger ability to break the ionic bonds formed within the hydrogel, leading to a higher efficiency during the healing.     

利用游戏化教学促进“微粒观”建构*——以“原子的结构”第一课时为例

分析了初中化学微粒观的教学内容和“原子的结构”的相关教学设计,针对学生“微粒观”建构存在的难题,提出利用反馈机制,采用“寓教于乐”的游戏化教学设计,并进行实践效果访谈。不仅完成了本课时的教学目标,也让学生对化学的兴趣更加浓厚。     

Wetting for self-healing and electrowetting for additive manufacturing

Advanced additive manufacturing actively widens its tool box of wettability-related phenomena to be used in production of new items. Novel self-healing engineering materials incorporate vascular networks with two types of nanochannels: the one containing a resin monomer, whereas another one — a curing agent. If such nanocomposites are damaged locally, both types of channels are locally broken, and they release resin monomer and curing agent droplets. These droplets spread by wettability over the nanotextured matrix, touch each other, and coalesce, which triggers polymerization reaction and crack stitching. Wettability-facilitated droplet spreading is accompanied by liquid imbibition in the pores in the nanofiber network. Such process peculiarities are in focus in the present review. An additional process relevant in direct writing and 3D printing is electrowetting (EW). It stems from the change in the contact angle in response to the electric polarization of dielectric substrates. EW allows movement of droplets on horizontal, vertical, and inverse surfaces, which can significantly facilitate the existing direct writing and 3D printing technologies. Accordingly, EW is also in focus in the present review.     

Mussel-mimicking sulfobetaine-based copolymer with metal tunable gelation,self-healing and antibacterial capability

In the present study, the sulfobetaine-based copolymer bearing a dopamine functionality showed gel formation adjusted by the application of metal salts for gelation and various values of pH. Normally, the liquid-like solution of the sulfobetaine-based copolymer and metal cross-linkers is transformed to a gel-like state upon increasing the pH values in the presence of Fe³⁺ and Ti³⁺. Metal-induced coordination is reversible by means of the application of EDTA as a chelating agent. In the case of Ag⁺ ions, the gel is formed through a redox process accompanied with the oxidative coupling of the dopamine moieties and Ag⁰ particle formation. Mussel-mimicking and metal-dependent viscoelastic properties were observed for Fe³⁺, Ti³⁺, and Ag⁺ cross-linking agents, with additionally enhanced self-healing behavior in comparison with the covalently cross-linked IO₄⁻ analogues. Antibacterial properties can be achieved both in solution and on the surface using the proper concentration of Ag⁺ ions used for gelation; thus, a tunable amount of the Ag⁰ particles are formed in the hydrogel. The cytotoxicity was elucidated by the both MTT assay on the NIH/3T3 fibroblast cell line and direct contact method using human dermal fibroblast cell (F121) and shows the non-toxic character of the synthesized copolymer.     

纳米木质素/二氧化硅基微胶囊的制备及在自愈合涂层中的应用

利用磷酸化改性木质素/二氧化硅复合纳米颗粒(PAL/SiO₂)作为壁材包埋活性组分异佛尔酮二异氰酸酯(IPDI)制备微胶囊(PAL/SiO₂-IPDI). 通过加入少量反应活性更高的聚合多甲基多二异氰酸酯(PMDI), 与水反应形成聚脲, 以增加微胶囊的壁厚. 采用光学显微镜、 扫描电子显微镜(SEM)和激光粒度分析仪(DLS)研究了PAL/SiO₂复合纳米粒子掺杂量, 水油比和剪切速率对微胶囊表面形貌、 粒径和壁厚的影响. 结果表明, 所制备的微胶囊呈现规整球形, 壁厚为2.36~3.50 μm, 平均粒径为40.3~201.5 μm. IPDI作为芯材包埋在微胶囊中, 芯材含量约为82.8%. 将制备的PAL/SiO₂-IPDI微胶囊添加到环氧树脂中得到自愈合环氧树脂涂层. 其在高盐浓度溶液中的抗侵蚀测试结果显示, 添加质量分数4%的PAL/SiO₂-IPDI微胶囊的环氧树脂涂层在划破后能够快速愈合, 显著降低基底的腐蚀电流和腐蚀速率. 纳米压痕实验表明, 环氧涂层的硬度为249.99 MPa, 而添加PAL/SiO₂-IPDI微胶囊后硬度增加到302.98 MPa, 弹性模量也有提高.     

Polydopamine-assisted co-deposition of polyacrylic acid inducing dentin biomimetic mineralization for tooth-like structure repair in vitro

The aging of the global population has caused dentin exposure and root caries to become significant patient-management issues in clinical dentistry. Biomimetic remineralization, as a non-invasive therapeutic method, is of great significance to solve the problem. Herein, a novel biomimetic-mineralizing strategy to induce the self-healing of dentin defects with similar tooth structure was developed through the easy one-step polydopamine (PDA)-assisted co-deposition of polyacrylic acid (PAA) (denoted as PDA@PAA) in vitro. Immersing demineralized dentin into PAA and dopamine (DA) mixed solutions. Hereafter, the modified demineralized dentin was immersed in the supersaturated solution of calcium and phosphate at 37 °C at designated time. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflection fourier transform infrared (ATR-FTIR) were performed to analyze the interaction and co-deposition between PDA and PAA. The remineralization of demineralized dentin was characterized by field emission scanning electron microscope (FE-SEM), TEM, X-ray diffraction (XRD), friction and wear test, nanoindentation, acid resistance. And the cytocompatibility of PDA@PAA was evaluated by cell counting kit-8 (CCK-8) and cell morphology observation. The results that PAA inhibited further PDA polymerization and aggregation, PDA@PAA were co-deposited onto the surface of demineralized dentin matrix. SEM and TEM showed that the demineralized-dentin modified with PDA@PAA was completely remineralized at 12 h, not only the dentin tubules were occluded, but more importantly, the demineralized dentin collagen matrix was remineralized. Moreover, after mineralization for 24 h, a dense mineral layer similar to enamel structure was regenerated on the surface of dentin and closely combined with dentin. The results of mechanical properties and acid resistance suggested that the mechanical properties of the regenerated enamel-like structure are close to that of enamel, and its acid resistance is better than that of enamel. This study demonstrated that the PDA-assisted co-deposition of PAA can offer an inexpensive, rapid, and efficient strategy for the management of illnesses related to exposed and demineralized dentin.