低密度聚乙烯/聚丙烯 聚乙烯共聚物共混体系混溶性的研究

通过在溶液中混和，然后采用将溶液冷冻干燥的方法，获得低密度聚乙烯与聚丙烯 聚乙烯共聚物的共混物，用ＤＳＣ及洗提技术对其进行了表征，讨论了配比及淬火条件对此共混体系混溶性的影响，证明了通过冷冻干燥的方法可显著提高共混体系的混溶性．     

Porous membranes of PLLA-PCL blend for tissue engineering applications

Porous membranes of polycaprolactone-poly(l-lactic acid) blends were prepared by a freeze-extraction process. This procedure was able to disperse homogeneously both components despite their amorphous phases being immiscible (as proven by the fact that the glass transition temperature of PCL in the blend is independent of blend composition) and both polymers crystallize. Thus, the porous membrane consists of amorphous and crystalline phases of both components. DSC and AFM were used to characterize the microstructure of the blends, whereas SEM and gravimetric methods enabled the porosity (around 70%) and pore architecture to be determined. Compression stress-strain experiments show the characteristic behaviour of porous materials with a yield stress that rapidly drops when the PCL content increases - whereas the deformation plateau zone enlarges.     

SDBS／正辛烷／正丁醇／盐水体系中相微乳液微观结构的研究

利用冷冻蚀刻电镜、ＦＴ－ＩＲ、ＥＳＲ和ＮＭＲ方法研究了ＳＤＢＳ／ｎ－Ｃ４Ｈ９ＯＨ／ｎ－Ｃ８Ｈ１８盐水体系中相微乳液微观结构。四种方法均表现随着体系含盐度的增加，中相微乳液微观结构经历了从Ｏ／Ｗ型到Ｂ．Ｃ型，再到Ｗ／Ｏ型的转变。     

Freeze fracture TEM investigations in liquid crystals

This review describes the results obtained in the determination of the nanometric structures of liquid crystal systems using the technique of freeze fracture transmission electron microscopy (FF-TEM). I focus the review on two types of major results that were obtained with this technique in respectively lyotropic and thermotropic liquid crystals systems.     

Nanofibrillar cellulose aerogels

Highly porous aerogels consisting of cellulose nanofibrils were prepared by dissolution/regeneration of cellulose in aq. calcium thiocyanate followed by regeneration and carefully controlled drying. The influence of drying method (regular freeze drying, rapid freeze drying, and solvent exchange drying) on resulting porosity was studied by electron microscopy and nitrogen adsorption. While regular freeze drying caused significant coalescence of microfibrillar units, solvent exchange drying gave highly porous aerogel composed of approx. 50 nm-wide cellulose microfibrils. Correspondingly, specific surface area of the solvent-exchange-dried aerogels ranged 160–190 m²/g, in contrast to 70–120 m²/g of regular freeze-dried materials. Rapid freeze technique using liquid nitrogen-cooled metal plate gave aerogel sheets with asymmetrical porosity, with the face contacted by copper having porous structure similar to those of solvent-exchange dried material.     

Synthesis of new molybdenum-tungsten, vanadium-tungsten and vanadium-molybdenum-tungsten oxynitrides from freeze-dried precursors

Interstitial molybdenum-tungsten, vanadium-tungsten and vanadium-molybdenum-tungsten oxynitrides in the solid solution series Mo_1−zW_z(O_xN_y) and V_1−zW_z(O_xN_y) (z=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1), and V_1−u−zMo_uW_z(O_xN_y) (u, z=0.2, 0.33, 0.4, 0.6; u+z<1), have been obtained by ammonolysis of precursors resulting from the freeze-drying of aqueous solutions of the metal salts (NH₄VO₃, (NH₄)₆Mo₇O₂₄·4H₂O and (NH₄)₆W₁₂O₃₉·18H₂O). A study of the influence of the preparative variables on the outcomes of this procedure is presented. Compounds in the Mo_1−zW_z(O_xN_y) series are prepared as single phases by ammonolysis of the respective freeze-dried precursors (during 2 h) at different temperatures between 973 and 1023 K, optimised for each composition, followed by slow cooling of the samples (except for the Mo-only containing phase, in which fast cooling has been used). Compounds in the V_1−zW_z(O_xN_y) and V_1−u−zMo_uW_z(O_xN_y) series are prepared as single phases by ammonolysis (during 2 h) of crystalline precursors (as resulting from thermal treatment in air at 873 K, during 12 h, of the freeze-dried precursors) at 1073 K, followed by slow cooling of the samples. All the compounds in these series have the rock-salt crystal structure, in which the metal atoms are in an fcc arrangement, with non-metal atoms occupying octahedral interstitial positions. The materials have been characterized by X-ray powder diffraction, elemental analysis, scanning electron microscopy and magnetic measurements.     

不同结晶度聚乙烯醇水凝胶中水氢键缺损的拉曼光谱学研究

聚乙烯醇 (ＰＶＡ)是一种水溶性高分子 ,它在一定条件下可以部分结晶形成水凝胶 ,其结晶度必然影响其机械性能及水在水凝胶中的状态 .部分结晶交联所得的ＰＶＡ水凝胶 ,由于无毒、机械性能好常用来作为生物医用材料 ,如接触眼镜、人工关节润滑软骨等[1,2 ] .水凝胶是轻度交联的高分子网络 ,其内含有大量的水 ,高分子交联网络与水之间的相互作用决定着水凝胶的物理性质和化学性质[3 ,4 ] .一般认为 ,水凝胶中的水以三种状态存在 ,即键合水 (Ｂｏｕｎｄｗａｔｅｒ)、自由水 (Ｆｒｅｅｗａｔｅｒ)和间隙水 (Ｉｎｔｅｒｓｔｉｔｉａｌｗａｔｅｒ…     

Bicellar systems as modifiers of skin lipid structure

The characterization of different bicellar aggregates and the effects of these systems on the stratum corneum (SC) microstructure have been studied. Dynamic light scattering (DLS) and freeze fracture electron microscopy (FFEM) techniques showed that both of the systems studied, dimyristoyl-phosphatidylcholine/dihexanoyl-phosphocholine (DMPC/DHPC) and dipalmitoyl-phosphocholine (DPPC)/DHPC, were formed by small discoidal aggregates at room temperature (20°C). Treating skin with DMPC/DHPC bicelles does not affect the SC lipid microstructure, whereas bicellar systems formed by DPPC and DHPC can promote the formation of new structures in the SC lipid domains. This indicates the passage of lipids from bicelles through the SC layers and also a possible interaction of these lipids with the SC lipids. Given the absence of surfactant in the bicellar composition and the small size of these structures, the use of these smart nano-systems offers great advantages over other lipid systems for dermatological purposes. Bicelles could be promising applications as drug carriers through the skin. This contribution, based on the new biological use of bicelles, may be useful to scientists engaged in colloid science and offers a new tool for different applications in skin and cosmetic research.     

减少再堆叠改性的石墨烯薄膜在锂离子电池中的应用

对溶剂化的石墨烯薄膜进行冷冻干燥处理得到改性的石墨烯薄膜,这种处理可以降低干燥过程中石墨烯片层之间严重的再堆叠.结果表明改性的石墨烯薄膜具有更多的折皱和更大的层间距,并提高了电化学性能.在电流密度为50 mA·g^-1时,该电池首次循环的放电和充电比容量分别为1189.3和645.2 mAh·g^-1,400次循环后充电比容量仍然超过305 mAh·g^-1,显著高于使用传统真空过滤得到的石墨烯薄膜的电化学性能.此外,相对于传统的石墨电极（包括活性物质、聚合物粘结剂和导电集流体）,石墨烯薄膜电极的质量和成本有明显的下降.     

A Robust Wood-inspired Catalytic System for Highly Efficient Reduction of 4-Nitrophenol

Porous solid scaffolds play key roles in preventing nanocatalysts from agglomeration, greatly maintaining the catalytic efficiency and stability of nanocatalysts. However, facile preparation of robust scaffolds with high mass transfer efficiency for loading nanocatalysts remains a major challenge. Here, we fabricate a wood-inspired shape-memory chitosan scaffold for loading Au nanoparticles to reduce 4-nitrophenol via a simple “freeze-casting and dip-adsorption” approach. The obtained catalytic scaffold highly resembles the unidirectional microchannel structure of natural wood, resulting in robust mechanical properties and outstanding water absorption capacity. Additionally, Au nanoparticles can be firmly and uniformly anchored on the inner surface of these microchannels via electrostatic interaction, forming numerous microreactors. This catalytic system exhibits a high 4-nitrophenol conversion rate of 99% in 5 s and impressive catalytic stability even after continuously treating with more than 3 L of highly concentrated 4-nitrophenol solution(1 mmol/L). Therefore, the wood-like catalytic system presented here demonstrates the potential to be applied in the field of water treatment and environmental protection.