Super‐Elastic Magnetic Structural Color Hydrogels

Structural color hydrogels are promising candidates as scaffold materials for tissue engineering and for matrix cell culture and manipulation, while their super‐elastic features are still lacking due to the irreconcilable interfere of the precursor and the self‐assembly unit. This hinders many of their practical biomedical applications where elasticity is required. Herein, hydrophilic and size‐controllable Fe₃O₄@poly(4‐styrenesulfonic acid‐co‐maleic acid) (PSSMA)@SiO₂ magnetic response photonic crystals are fabricated as the assembly units of the structural color hydrogels by orderly packing of core–shell colloidal nanocrystal clusters via a two‐step facile synthesis approach. These units are capable of responding instantaneously to an external magnetic field with resistance to interference of ions, thus, by integrating super‐elastic hydrogels, super‐elastic magnetic structural color hydrogels can be achieved. The structural color arises from the dynamic ordering of the magnetic nanoparticles through the contactless control of external magnetic field, allowing regional polymerization of hydrogels via changing orientation and strength of external magnetic field. These regionally polymerized super‐elastic magnetic structural color hydrogels can work as anti‐counterfeiting labels with super‐elastic identification, which may be widely used in the future.     

古木硅化处理对其物化性能的影响

在田螺山遗址的挖掘过程中,出土了大量的木质文物。由于年代久远且长期处于潮湿环境,木质文物现已出现腐朽、开裂等问题,濒临毁灭。为对这些古木实施保护,我们受自然界硅化木的启发,将这些古木进行硅化处理。为在较短时间内实现长期有效的原位硅化加固目的,我们采用电渗法先对古木进行加速硅化处理,再进行钙化处理。在电子显微镜下可见,经处理后的古木内部由层片状硅酸钙大量填充,而表面则被细致的硅酸钙颗粒完整覆盖。在宏观性能上,经处理后古木抗压性能提升了150%左右,保水性能亦大幅提升,不易失水干缩,这种硅化处理对古木起到了强化保护作用。     

Polymer‐Mediated Nanoparticle Assembly: Structural Control and Applications

Nanoparticle–polymer composites are diverse and versatile functional materials, with applications ranging from electronic device fabrication to catalysis. This review focuses on the use of chemical design to control the structural attributes of polymer‐mediated assembly of nanoparticles. We will illustrate the use of designed particles and polymers to create nanocomposites featuring interesting and pragmatic structures and properties. We will also describe applications of these engineered materials.     

Influence of the Thermodynamic and Kinetic Control of Self‐Assembly on the Microstructure Evolution of Silk‐Elastin‐Like Recombinamer Hydrogels

Complex recombinant biomaterials that merge the self‐assembling properties of different (poly)peptides provide a powerful tool for the achievement of specific structures, such as hydrogel networks, by tuning the thermodynamics and kinetics of the system through a tailored molecular design. In this work, elastin‐like (EL) and silk‐like (SL) polypeptides are combined to obtain a silk‐elastin‐like recombinamer (SELR) with dual self‐assembly. First, EL domains force the molecule to undergo a phase transition above a precise temperature, which is driven by entropy and occurs very fast. Then, SL motifs interact through the slow formation of β‐sheets, stabilized by H‐bonds, creating an energy barrier that opposes phase separation. Both events lead to the development of a dynamic microstructure that evolves over time (until a pore size of 49.9 ± 12.7 µm) and to a delayed hydrogel formation (obtained after 2.6 h). Eventually, the network is arrested due to an increase in β‐sheet secondary structures (up to 71.8 ± 0.8%) within SL motifs. This gives a high bond strength that prevents the complete segregation of the SELR from water, which results in a fixed metastable microarchitecture. These porous hydrogels are preliminarily tested as biomimetic niches for the isolation of cells in 3D cultures.     

Solids Under Extreme Shear: Friction‐Mediated Subsurface Structural Transformations

Tribological contacts consume a significant amount of the world's primary energy due to friction and wear in different products from nanoelectromechanical systems to bearings, gears, and engines. The energy is largely dissipated in the material underneath the two surfaces sliding against each other. This subsurface material is thereby exposed to extreme amounts of shear deformation and often forms layered subsurface microstructures with reduced grain size. Herein, the elementary mechanisms for the formation of subsurface microstructures are elucidated by systematic model experiments and discrete dislocation dynamics simulations in dry frictional contacts. The simulations show how pre‐existing dislocations transform into prismatic dislocation structures under tribological loading. The stress field under a moving spherical contact and the crystallographic orientation are crucial for the formation of these prismatic structures. Experimentally, a localized dislocation structure at a depth of ≈100–150 nm is found already after the first loading pass. This dislocation structure is shown to be connected to the inhomogeneous stress field under the moving contact. The subsequent microstructural transformations and the mechanical properties of the surface layer are determined by this structure. These results hold promise at guiding material selection and alloy development for tribological loading, yielding materials tailored for specific tribological scenarios.     

2种羧基化纤维素衍生物对聚丙烯酰胺复合水凝胶力学性能的影响

为了深入理解羧基化纤维素衍生物聚集态结构和羧基含量对金属络合型复合水凝胶的增强增韧作用,文中分别在2种羧基化纤维素衍生物——聚阴离子纤维素(PAC)和TEMPO氧化纤维素纳米纤维(CNF)水体系中,进行了丙烯酰胺(AM)的自由基水溶液聚合,制备了PAM基复合水凝胶,进而经0.1 mol/L ZrOCl2水溶液处理,获得...     

温度对结构陶瓷弯曲性能的影响

通过四点弯曲还试验方法，初步讨论了Ａｌ２Ｏ３和Ｓｉ３Ｎ４两种陶瓷材料高温下弯曲性能与温度的关系。试验发现，Ａｌ２Ｏ３材料在１０００℃以下，强度变化不明显，但随温度进一步升高，强度明显下降，Ｓｉ３Ｎ４材料在高温下具有明显的塑性变形能力。     

Controlling Mechanical Properties of Cell‐Laden Hydrogels by Covalent Incorporation of Graphene Oxide

Graphene‐based materials are useful reinforcing agents to modify the mechanical properties of hydrogels. Here, an approach is presented to covalently incorporate graphene oxide (GO) into hydrogels via radical copolymerization to enhance the dispersion and conjugation of GO sheets within the hydrogels. GO is chemically modified to present surface‐grafted methacrylate groups (MeGO). In comparison to GO, higher concentrations of MeGO can be stably dispersed in a pre‐gel solution containing methacrylated gelatin (GelMA) without aggregation or significant increase in viscosity. In addition, the resulting MeGO‐GelMA hydrogels demonstrate a significant increase in fracture strength with increasing MeGO concentration. Interestingly, the rigidity of the hydrogels is not significantly affected by the covalently incorporated GO. Therefore, this approach can be used to enhance the structural integrity and resistance to fracture of the hydrogels without inadvertently affecting their rigidity, which is known to affect the behavior of encapsulated cells. The biocompatibility of MeGO‐GelMA hydrogels is confirmed by measuring the viability and proliferation of the encapsulated fibroblasts. Overall, this study highlights the advantage of covalently incorporating GO into a hydrogel system, and improves the quality of cell‐laden hydrogels.     

Physicochemical and Biological Properties of Biomimetic Mineralo‐Protein Nanoparticles Formed Spontaneously in Biological Fluids

Recent studies indicate that mineral nanoparticles (NPs) form spontaneously in human body fluids. These biological NPs represent mineral precursors that are associated with ectopic calcifications seen in various human diseases. However, the parameters that control the formation of mineral NPs and their possible effects on human cells remain poorly understood. Here a nanomaterial approach to study the formation of biomimetic calcium phosphate NPs comparable to their physiological counterparts is described. Particle sizing using dynamic light scattering reveals that serum and ion concentrations within the physiological range yield NPs below 100 nm in diameter. While the particles are phagocytosed by macrophages in a size‐independent manner, only large particles or NP aggregates in the micrometer range induce cellular responses that include production of mitochondrial reactive oxygen species, caspase‐1 activation, and secretion of interleukin‐1β (IL‐1β). A comprehensive proteomic analysis reveals that the particle‐bound proteins are similar in terms of their identity and number, regardless of particle size, suggesting that protein adsorption is independent of particle size and curvature. In conclusion, the conditions underlying the formation of mineralo‐protein particles are similar to the ones that form in vivo. While mineral NPs do not activate immune cells, they may become pro‐inflammatory and contribute to pathological processes once they aggregate and form larger mineral particles.     

Influence of Structural Defects on the Thermophysical and Magnetic Properties of Polyaniline

The temperature dependences of the thermophysical and paramagnetic properties of polyaniline that contains variously structured impurity centers have been investigated. The results obtained have been explained on the basis of the theory of phase transitions of second order.     

Structural Characterization and Magnetic Properties of Iron Oxides Biological Polymers

Iron oxide nanoparticles (IONs) coated with different biological (dextran, sucrose) polymers have been synthesized by the coprecipitation method. Biological polymers coated iron oxide nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM). Zero field cooled and field cooled magnetizations measurements are also reported. We present a preliminary study of the influence of biological polymer on the interaction effects in powders. The temperature, T _max, of the maximum, increased from 25 K (dextran) to 52 K (sucrose). These values are due to the decrease of interparticle interactions, mainly as a result of the interparticle distance increase.