Aggregate Conformation and Rheological Properties of Didodecyldimethylammonium Bromide in Aqueous Solution

Aggregation behavior of didodecyldimethylammonium bromide (DDAB) in aqueous solution was investigated using negative-staining and freeze-fracture transmission electron microscopy (TEM) methods. With the concentration increase, the vesicle size enlarged from the range of 100–200 nm to 500–3000 nm and the structure transform from unilamella to multilamella. Rheological and viscosity measurement results indicated that the system exhibited a gel-like material characteristic and shearing thinning in property, as shown that the apparent viscosity decreased gradually during the shear rate ascended from 1 × 10^?4–1 × 10⁴ s^?1. Furthermore, the relationship between aggregate conformation and solution rheological properties was discussed.     

Studies on the electro-optical and the light-scattering properties of PDLC films with the size gradient of the LC droplets

Polymer dispersed liquid crystal (PDLC) films with the size gradient of the LC droplets were prepared based on the epoxy/acrylate hybrid polymer matrix. The ultraviolet (UV) intensity gradient was induced by the UV-absorbing dye over the thickness of the samples. Taking advantage of the difference between the epoxy monomers and acrylate monomers in polymerisation rates and the UV intensity gradient, the gradient distribution of the LC droplet size was formed in PDLC films. The effect of the size gradient of the LC droplets on the electro-optical and the light-scattering properties of PDLC films was investigated. The results showed that due to the size gradient distribution of the LC droplets, PDLC films could exhibit the strong light scattering in the UV-visible-near infrared (VIS-NIR) region. Consequently, it provides a potential approach for modulating NIR light transmittance.     

Dynamic relaying properties of a β-turn peptide in long-range electron transfer

The relay stations play a significant role in long-range charge hopping transfer in proteins. Although studies have clarified that many more protein structural motifs can function as relays in charge hopping transfers by acting as intermediate charge carriers, the relaying properties are still poorly understood. In this work, taking a β-turn oligopeptide as an example, we report a dynamic character of a relay with tunable relaying properties using the density functional theory calculations. Our main finding is that a β-turn peptide can serve as an effective electron relay in facilitating long-range electron migration and its relay properties is vibration-tunable. The vibration-induced structural transient distortions remarkably affect the lowest occupied molecular orbital (LUMO) energy, vertical electron affinity and electron-binding mode of the β-turn oligopeptide and the singly occupied molecular orbital (SOMO) energy of the corresponding electron adduct and thus the relaying properties. Different vibration modes lead to different structural distortions and thus have different effects on the relaying properties and ability of the β-turn peptide. For the relaying properties, there approximately is a linear negative correlation of electron affinity with the LUMO energy of the β-turn or the SOMO energy of its electron adduct. Besides, such relaying properties also vary in the vibration evolution process, and the electron-binding modes may be tunable. As an important addition to the known static charge relaying properties occurring in various protein structural motifs, this work reports the dynamic electron-relaying characteristics of a β-turn oligopeptide with variable relaying properties governed by molecular vibrations which can be applied to different proteins in mediating long-range charge transfers. Clearly, this work reveals molecular vibration effects on the electron relaying properties of protein structural motifs and provides new insights into the dynamics of long-range charge transfers in proteins. © 2018 Wiley Periodicals, Inc.     

Drug‐Loaded Elastin‐Like Polypeptide–Collagen Hydrogels with High Modulus for Bone Tissue Engineering

Emphasizing the role of hydrogel stiffness and cellular differentiation, this study develops collagen and elastin‐like polypeptide (ELP)–based bone regenerative hydrogels loaded with recombinant human bone morphogenetic protein‐2 (rhBMP‐2) and doxycycline with mechanical properties suitable for osteogenesis. The drug‐incorporated collagen–ELP hydrogels has significantly higher modulus of 35 ± 5 kPa compared to collagen‐only hydrogels. Doxycycline shows a bi‐phasic release with an initial burst release followed by a gradual release, while rhBMP‐2 exhibits a nearly linear release profile for all hydrogels. The released doxycycline shows anti‐microbial activity against Pseudomonas aeruginosa, Streptococcus sanguinis, and Escherichia coli. Microscopic observation of the hydrogels reveals their interconnected, macroporous, 3D open architecture with pore diameters between 160 and 400 µm. This architecture supports human adipose–derived stem cell attachment and proliferation from initial days of cell seeding, forming a thick cellular sheath by day 21. Interestingly, in collagen and collagen–ELP hydrogels, cell morphology is elongated with stretched slender lamellipodial formation, while cells assemble as spheroidal aggregates in crosslinked as well as drug‐loaded hydrogels. Osteogenic markers, alkaline phosphatase and osteocalcin, are expressed maximally for drug‐loaded hydrogels compared to those without drugs. The drug‐loaded collagen–ELP hydrogels are thus promising for combating bacterial infection and promoting guided bone regeneration.     

Preparation and adhesive properties of colored Ti/Zr-based conversion coating on aluminum foil for lithium battery packaging

In this study, an aluminum (Al) foil used for lithium ion battery packaging film was treated with titanium (Ti)/zirconium (Zr) solution containing hexafluorotitanic acid and hexafluorozirconic acid using tannic acid as a colorant and metavanadate as an accelerator, respectively, and a golden conversion coating was successfully deposited on the surface of Al foil. The morphology and composition of the coating were characterized by scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, and the hydrophilicity was assessed by contact angle measurement. The effect of Ti/Zr treatment on the adhesion properties of Al foil was evaluated by T-peeling test and compared with that of traditional chromate-phosphate treatment. The results show that tannic acid contributes to the formation of the golden coating, and metavanadate accelerates the formation of the conversion coating. The results also indicate that the Ti/Zr-based conversion coating is mainly composed of Al₂O₃, Al (OH)₃, AlF₃, TiO₂/ZrO₂, NH₄VO₃, and V₂O₅. The Ti/Zr treatment cannot only improve the heat-sealing strength, but also the T-peeling strength by approximately 12 times compared with that of untreated Al foil. Thus, Ti/Zr treatment has the potential to replace the traditional chromate conversion treatment.     

基于5-甲基-3-吡唑甲酸为配体的钴(Ⅱ)、镍(Ⅱ)配合物的合成、晶体结构和电化学性质

利用5-甲基-3-吡唑甲酸、咪唑和相应醋酸盐在乙醇和水混合溶剂中反应,得到了配合物[M(MPA)2(Im)2].2H2O(1:M=Co;2:M=Ni)(HMPA=5-甲基-3-吡唑甲酸,Im=咪唑)。用元素分析、红外光谱、X-单晶衍射结构分析、热重分析、循环伏安等对其进行了表征。配合物1和2的晶体结构参数如下:配合物1和2的晶体都属于单斜晶系,空间群为P21/n。配合物1的晶胞参数为a=0.847 02(16)nm,b=1.461 5(3)nm,c=0.899 67(17)nm,β=101.759(6)°,V=1.090 3(4)nm3,Z=2;配合物2的晶胞参数为a=0.853 59(6)nm,b=1.451 77(9)nm,c=0.889 83(6)nm,β=102.382 0(10)°,V=1.077 04(12)nm3,Z=2。金属离子与来自2个5-甲基-3-吡唑甲酸配体中的2个氮原子及2个氧原子,2个咪唑分子中的2个氮原子配位,形成八面体配位构型。配合物中的独立结构单元[M(MPA)2(Im)2].2H2O通过2种分子间氢键(N-H…O和C-H…O)形成三维超分子。循环伏安性质测试表明配合物1和2的电解过程均为准可逆过程。     

s区金属离子对锰(Ⅱ)配位聚合物的结构构建及性质影响

本文通过在s区金属离子(Li+,Na+,K+,Mg2+,Ca2+)存在下,2,6-吡啶二羧酸(H2pda)或2-吡啶羧酸(picH)与Mn(Ac)2.4H2O的水热合成反应,系统探讨了s区金属离子的电荷和半径对Mn(Ⅱ)配位聚合物的结构构建以及热稳定性和溶解性能的影响。合成了2个混合金属配位聚合物[Na2Mn(pda)2]n(1)和[K2Mn(pda)2]n(2),并通过红外和X-单晶衍射进行了结构表征:1属于正交系,空间群Pnna;2属于单斜系,空间群P2/n。同时应用荧光光谱测试研究了配合物1水溶液的荧光性质。     

Synergistic effect between POSS and fumed silica on thermal stabilities and mechanical properties of room temperature vulcanized (RTV) silicone rubbers

In this paper, both divinyl-hexa[(trimethoxysilyl)ethyl]-POSS (DVPS) and fumed silica were firstly introduced into polydimethylsiloxane (PDMS) system using as the cross-linker and the reinforcing filler respectively. And a series of novel RTV silicone rubbers synergistically enhanced by DVPS and fumed silica were prepared. The cross-linked networks in the novel RTV silicone rubbers have been studied by attenuated total reflection infrared spectroscopy, and the dispersions of POSS and fumed silica in these novel RTV silicone rubbers have been observed by means of scanning electron microscope (SEM). And thermal stabilities, thermo-oxidative stabilities and mechanical properties of these novel RTV silicone rubbers were studied by means of thermal gravimetric analysis and universal tensile testing machine, respectively. From the obtained results, it was found that synergistic effect between POSS-rich areas and fumed silica on thermal stability and mechanical property of RTV silicone rubber indeed existed. And the experimental results also exhibited that the thermal stabilities and mechanical properties of the novel RTV silicone rubbers were far better than those of the reference materials (DVPR and MTFR). The striking enhancements in thermal properties and improvements on mechanical properties of novel RTV silicone rubbers were likely attributed to the synergistic effect between POSS-rich domains and fumed silica. Meanwhile, it was found that the mechanical properties of RTV silicone rubbers prepared with a given amount of POSS cross-linker were enhanced with the increment of the loading amount of fumed silica.     

Photophysical properties and photostability of novel unsymmetric polycyclicphenazine-type D-π-A fluorescent dyes and the dye-doped films

Structural isomers of unsymmetric polycyclicphenazine-type D-π-A fluorescent dyes have been newly synthesized and characterized in both solution and polymer films. The dyes exhibited two strong absorption bands at around 328-401 nm and 516-532 nm, and an intense fluorescence band at around 595-629 nm (Φ = 0.32-0.84) in 1,4-dioxane. The dye-doped polymer films showed good ability of wavelength conversion; the films can efficiently convert ultraviolet and green-yellow lights into red light (Φ = 0.43-0.86). Moreover, the photostability of the dyes-doped PS, PMMA, and PLA films has been investigated.