A study on phase morphology and surface properties of polyurethane/organoclay nanocomposite

In this study, polyurethane/organically modified layered silicate (organoclay) nanocomposites were prepared through in situ polymerization in the presence of organoclay. Phase morphology of the polyurethane/organoclay nanocomposite was investigated by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The results suggest that the inter-domain repeat distance decreased with the introduction of organoclay. The organoclay has a more significant effect on the inter-domain repeat distance at a low hard segment content. Also with the increase of the hard segment, the inter-domain repeat distance and domain size increased markedly. The size of hard domain of the polyurethane was found to be in the range of 12-32 nm in this case, and it keeps nearly unchanged with the clay content. It is suggested by AFM phase imaging technique that the hard domain can self-organize further to form spherical aggregates. The introduction of clay into the polyurethane matrix resulted in the decrease in the size of the spherical aggregates from ∼800 nm to ∼500 nm, indicating clay has an important effect on the aggregation behavior of hard domains. The effect of clay on the surface energy was examined by means of AFM and goniometry techniques. The results obtained by two methods are consistent, i.e., with the increase of clay content, the surface energy decreased due to the effect of organic modifier.     

Preparation and characterization of chitin whisker-reinforced silk fibroin nanocomposite sponges

For highly porous form such as sponges or scaffolds, the induction of the β-sheet formation of silk fibroin to make the water-stable materials usually results in their high shrinkage leading to a difficulty in controlling shape and size of materials. Thus, the objective of this study was to improve dimensional stability of silk fibroin sponge by incorporating chitin whiskers as nanofiller. Chitin whiskers exhibited the average length and width of 427 and 43 nm, respectively. Nanocomposite sponges at chitin whiskers to silk fibroin weight ratio (C/S ratio) of 0, 1/8, 2/8, or 4/8 were prepared by using a freeze-drying technique. The dispersion of chitin whiskers embedded in the silk fibroin matrix was found to be homogeneous. The presence of chitin whiskers embedded into silk fibroin sponge not only improved its dimensional stability but also enhanced its compression strength. Regardless of the chitin whisker content, SEM micrographs showed that all samples possessed an interconnected pore network with an average pore size of 150 μm. To investigate the feasibility of the nanocomposites for tissue engineering applications, L929 cells were seeded onto their surfaces, the results indicated that silk fibroin sponges both with and without chitin whiskers were cytocompatible. Moreover, when compared to the neat silk fibroin sponge, the incorporation of chitin whiskers into the silk fibroin matrix was found to promote cell spreading.     

Structure and properties of biodegradable wheat gluten/attapulgite nanocomposite sheets

Wheat gluten (WG) and Attapulgite (ATP) was mixed in acidic solution and freeze-dried, thermally compression-molded to form nanocomposite sheet. The influences of reduction and sonication on structure of wheat gluten were examined by Raman spectrum. The variation of disulfide bonding in wheat gluten show that the sonication is more effective than reduction on the breakage of disulfide bonds, whereas the content of disulfide bonds in the WG sheet molded by sonicated WG powder is the highest in the molded sheets. FT-IR analysis displays that the bands in the range of 1700-1600 cm⁻¹ shift to higher frequency after mixing WG and ATP powders and molding the nanocomposite. The tensile and bending properties of the WG sheet increase with addition of ATP powder, and the properties of the sheet molded by sonicated WG powder decrease for the reduction of the disulfide bonding, but the properties of the sheet can be improved by addition of ATP. The WG/ATP nanocomposite images observed by SEM and TEM show that rod-like ATP particles are evenly dispersed in WG matrix, but the crystal structure of ATP is impervious. The viscoelasticity of the WG sheet declines with addition of ATP particle, and that the α-relaxation of the WG sheet molded by sonicated WG powder shift to high temperature and become broad. Both mass and bending strength of 7 wt% WG/ATP nanocomposite sheet show a decline over a soil exposure time of 20 days.     

具有高电催化活性的g-C3N4-ZnS-DNA纳米复合材料的制备及应用

g-C3N4作为丰富的可见光光催化剂,具有独特的二维结构,优异的化学稳定性和可调的电子结构;但因其激子结合能高和结晶度较低,导致其光催化过程量子效率偏低,限制了光催化剂的推广应用.根据g-C3N4独特的可调电子结构,将其与半导体材料进行耦合,形成异质结构,通过调控半导体的能带结构,优化其光吸收能力,促进光生电子-空穴对的快速分离,从而抑制光生载流子的复合,提高其光催化效率.目前,人们已发展了许多g-C3N4与窄禁带和宽禁带半导体耦合形成的二元纳米复合材料,广泛应用于光催化降解污染物、光催化水解产氢和光催化还原将温室气体CO2转换成有用的碳氢燃料等方面,但关于g-C3N4基的三元复合光催化剂,尤其与天然纳米材料DNA复合,研究其电催化性能的却鲜有报道.近年来,随着环境污染日益严重,被称为环境激素的五氯酚(PCP)、壬基酚(NP)等一系列环境激素在水体和土壤等环境介质中长期残留,难以降解,且容易聚集在生物体内,通过空气循环和食物链等方式进入人体,对环境和人体产生极大的危害,所以越来越多的人致力于环境激素的高效筛选和检测的研究.常规的分析方法已经很难满足人们对环境激素的高灵敏检测的要求,而电化学方法因其操作简单、成本低廉、选择性好、灵敏度高、样品前处理简单等特点而备受关注.本文成功设计和制备了g-C3N4-ZnS-DNA三元纳米复合材料.首先,采用水热法制备了ZnS半导体纳米片,采用热解法制备了g-C3N4纳米片,接着将它们与DNA复合,成功制备了g-C3N4-ZnS-DNA纳米复合材料,通过苯胺聚合法修饰到玻碳电极表面,成功构建了NP和PCP环境激素新型的电化学传感器.通过透射电镜、X射线衍射、紫外-可见漫反射光谱和X射线光电子能谱等对其形貌、结构及组分进行了表征.采用CHI660C仪器对新型的电化学传感器的电催化性能进行了系统研究.通过循环伏安法(CV)和示差脉冲伏安法(DPV)研究了NP和PCP在g-C3N4-ZnS-DNA-GCE修饰电极的上的电化学行为.电化学阻抗谱表明,g-C3N4-ZnS-DNA纳米复合材料大大促进了修饰电极的电子传递能力,与g-C3N4膜相比,ZnS和DNA共掺杂的g-C3N4膜对NP和PCP的电化学响应明显提高,峰电流是g-C3N4膜的2倍,电催化活性明显增强.在最优化条件下,NP和PCP检测的线性范围分别为2.0×10–5–1.0×10–8和1.0×10–5–1.0×10–8 mol L–1,检出限均为3.3×10–9 mol L–1.将g-C3N4-ZnS-DNA-GCE修饰电极用于湖水中NP和PCP的测定,其回收率均高于90%,证明g-C3N4-ZnS-DNA纳米复合材料修饰电极可应用实际水样中痕量环境激素的测定.同时,我们分析了电催化活性增强的原因:(1)DNA分子通过C-O-C键连接到g-C3N4表面,导致ZnS纳米片组装成线性超结构,形成稳定的g-C3N4-ZnS-DNA纳米复合材料;(2)由于DNA和PCP或NP之间的相互作用使得电极表面上的PCP和NP的浓度增加;(3)纳米复合材料聚苯胺膜可促进电子转移和加速PCP或NP向电极表面的扩散;并提出了Z型g-C3N4-ZnS-DNA纳米复合材料的电子转移路径,以及PCP和NP的可能的电催化氧化机理.     

Preparation and characterization of polyaniline/polysulfone nanocomposite ultrafiltration membrane

Novel nanocomposite membrane was prepared through the filtration of polyaniline (PANI) nanofiber aqueous dispersion with polysulfone (PS) ultrafiltration (UF) membrane. Scanning electron microscope (SEM) images showed that PANI nanofiber layer was formed on the PS membrane surface. Atomic force microscopy (AFM) analysis indicated that the nanocomposite membrane had rougher surface than the PS substrate membrane. Compared with the PS substrate membrane, the nanocomposite membrane had much better permeability for the good hydrophilicity of PANI nanofiber layer, and had almost the same rejection performance. In addition, the nanocomposite membrane had positive surface potential under acidic condition because PANI could be protonated easily by acid. During the filtration of BSA solution, the nanocomposite membrane showed much better antifouling performance than the substrate membrane for the hydrophilicity and steric hindrance effect of its nanofiber layer. Moreover, under acidic solution condition, strong electrostatic repulsion between PANI nanofibers and BSA existed and improved membrane antifouling performance further.     

Functionalizing nano-montmorillonites by modified with intumescent flame retardant: Preparation and application in polyurethane

The 2-(2-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-ylamino)ethy-amino)-N,N,N-triethyl-2-oxoethanaminium chloride (compound c) containing phosphorus-nitrogen structure was synthesized and characterized. A novel intumescent flame retardant, namely montmorillonite (MMT) by modified with compound c (c-MMT), was prepared by ion exchanging of the nanometer Na⁺-montmorillonite (Na-MMT) with compound c. Both FTIR and X-ray diffraction (XRD) indicated that compound c had intercalated with Na-MMT and exfoliated c-MMT/PU nanocomposites have obtained by in-situ polymerization. TEM results further support the formation of the exfoliated nanocomposites. The thermal stability and flammability of c-MMT/PU composites were investigated by thermogravimetric analysis (TGA) and cone calorimeter test respectively. The results showed that the addition of flame retardant c-MMT enhanced the thermal stability and flame retardancy of PU significantly. SEM results indicated that c-MMT can achieve better dispersion in the chars after combustion and the compact and dense intumescent char is formed for c-MMT/PU composites after combustion. It is found that the char structure plays an important role for c-MMT in PU resin. The thermal stability and flame retardancy of PU resin were also significantly improved by an addition of c-MMT in PU resin.     

Preparation, characterization and electrochemical corrosion studies on environmentally friendly waterborne polyurethane/Na-MMT clay nanocomposite coatings

In this study, we present the first practical evaluation for the corrosion protection effect of waterborne polyurethane (WPU)/Na⁺-montmorillonite (Na⁺-MMT) clay nanocomposite coating. Typically, a series of waterborne polyurethane (WPU)/Na⁺-montmorillonite (Na⁺-MMT) clay nanocomposite materials have been successfully prepared by effectively dispersing the inorganic nanolayers of commercially purified Na⁺-MMT clay in WPU matrix through direct aqueous solution dispersion technique. First of all, WPU was prepared by polymerizing PCL, DMPA and H₁₂MDI, followed by characterized by nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). Subsequently, the as-prepared PU/Na⁺-MMT clay nanocomposite (Na⁺-PCN) materials were subsequently characterized by FTIR, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM).PCN materials in the form of coating at low Na⁺-MMT clay loading up to 3 wt% coated on the cold-rolled steel (CRS) coupons were found to exhibit superior corrosion protection effect over those of neat WPU based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current and impedance in 5 wt% aqueous NaCl electrolyte. Effects of the material composition on the gas permeability, thermal stability and optical clarity of neat WPU along with a series of Na⁺-PCN materials, in the form of coating and free-standing film, were also studies by gas permeability analyzer (GPA), thermogravimetric (TGA), differential scanning calorimetry (DSC) and ultraviolet UV-visible transmission spectroscopy, respectively. As control experiments, a series of PU/organo-MMT nanocomposite (denoted by organo-PCN) materials were also prepared for comparative studies.     

Preparation, characterization, and photocatalytic activity of polyaniline/ZnO nanocomposite

Polyaniline (PANI)/zinc oxide (ZnO) nanocomposite was synthesized by in-situ polymerization. X-ray diffraction patterns, UV?Cvisible spectroscopy, SEM, and TEM were used to characterize the composition and structure of the nanocomposite. Nanostructured PANI/ZnO composite was used as photocatalyst in the photodegradation of methylene blue dye molecules in aqueous solution. The photocatalytic activity of PANI/ZnO nanocomposite under UV and visible light irradiation was evaluated and was compared with that of ZnO nanoparticles. ZnO/PANI core?Cshell nanocomposite had greater photocatalytic activity than ZnO nanoparticles and pristine PANI under visible light irradiation. According to these results, application of PANI as a shell on the surface of ZnO nanoparticles causes the enhanced photocatalytic activity of the PANI/ZnO nanocomposite. Also UV?Cvisible spectroscopy studies showed that the absorption peak for PANI/ZnO nanocomposite has a red shift toward visible wavelengths compared with the ZnO nanoparticles and pristine PANI. The effect of different operating conditions on the photocatalytic performance of PANI/ZnO nanocomposite in the photodegradation of methylene blue dye molecules was investigated in a bath experimental setup.     

Synergism between flame retardant and modified layered silicate on thermal stability and fire behaviour of polyurethane nanocomposite foams

Synergy in flame retardancy of polyurethane foams between phosphorus-based flame retardant (aluminium phosphinate) and layered silicates has been investigated. We used pristine montmorillonite as well as ammonium modified clay (commercially available) and diphosphonium modified clay, which were synthesised by the intercalation of the quaternary diphosphonium salt according to a procedure reported here. The morphology of the foams was characterised through X-ray diffraction (XRD), while thermal properties were characterised by oxygen index test, cone calorimeter and thermogravimetric analysis (TGA). The morphological characterisation showed that pristine and diphosphonium modified clays are almost slightly intercalated, while ammonium modified one is very well dispersed. The results of thermal characterisation showed that in the presence of phosphinate enhancements of oxygen index, fire behaviour, measured by cone calorimeter, and thermal stability have been achieved. Phosphinate is therefore an efficient flame retardant for polyurethane foams and its flame retardancy action takes place in both condensed and gas phases. Pristine and ammonium modified layered silicate bring some enhancements of thermal stability while having no important effect in decreasing peak heat release rate (PHRR) and total heat evolved (THE) when used in conjunction with phosphinate; their main advantage is related to the enhancement of compactness of the char layer formed. Diphosphonium clay is instead effective in further improving the fire behaviour of the foams because of the flame retardancy action of phosphonium: both PHRR and THE were decreased. The analysis of cone calorimeter data showed that clays act through physical effect constituting a barrier at the surface which is effective in preventing or slowing the diffusion of volatiles and oxygen, while phosphinate and phosphonium are more effective owing to their combined action in both condensed and gas phases.     

螺旋纳米碳纤维的制备与表征

利用氢电弧等离子体法制备了纳米铜-镍合金作为催化剂,通过乙炔的催化热解制备了对称生长的螺旋纳米碳纤维.并用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和红外(IR)对其进行表征,发现在单个纳米铜-镍合金粒子上对称生长出两根螺旋纳米碳纤维,它们的旋向相反,但是具有相同的螺旋直径、螺旋长度和碳纤维直径,而且纳米铜-镍合金粒子也有各种不同的形状.此外,这两根对称生长的螺旋纳米碳纤维之间的夹角也不同,分别为60°,90°,110°和160°.IR结果表明,螺旋纳米碳纤维分子结构中既含有不饱和的CC双键,又含有饱和的-CH₂-和-CH₃-基团.然而,利用氢电弧等离子体法制备的纳米铜和纳米镍作为催化剂,催化热解乙炔,得到的产物均是直线型碳纤维.     

具有光学活性的两亲性聚炔-聚乙二醇单甲醚接枝共聚物的合成与表征

设计并合成了含手性侧基和含亲水性大分子侧基的接枝聚炔共聚物[聚(丙炔酸薄荷醇酯-co-丙炔酸聚乙二醇单甲醚酯)(poly(a-co-b),(a:propiolic acid L-menthol ester;b:propiolic acid polyethylene glycol monomethyl ether est...     

甲基取代的手性环酯化合物的螺旋结构与旋光性分析

利用螺旋片段判定规则,结合X射线衍射结构图及模型结构,对4个大环酯类化合物及甲基取代产物的螺旋结构与旋光性进行了定量分析,检测结果证明了理论分析的正确性;对旋光值变化规律给予了合理解释.     

邻苯二甲酸L-(+)-2,3-O-亚异丙基苏力糖酯的两种构象式的螺旋结构与旋光性

在晶 (固 )态下 ,化合物邻苯二甲酸 L-( +) -2 ,3 -O-亚异丙基苏力糖酯存在两种不同的构象形式 ,利用螺旋片段判定规则及ω值 ,结合 X射线衍射数据及扭转角数据 ,对这两种构象形式的所有螺旋片段进行了分析 ,尽管两种构象形式的净值螺旋性相反 ,但仍然得出总净值螺旋性与旋光方向一致的结论     

Preparation of porous nanocomposite scaffolds with honeycomb monolith structure by one phase solution freezedrying method

Biodegradable porous nanocomposite scaffolds of poly（lactide-co-glycolide）（PLGA） and L-lactic acid（LAc） oligomer surface-grafted hydroxyapatite nanoparticles（op-HA） with a honeycomb monolith structure were fabricated with the single-phase solution freeze-drying method.The effects of different freezing temperatures on the properties of the scaffolds,such as microstructures,compressive strength,cell penetration and cell proliferation were studied.The highly porous and well interconnected scaffolds with a tunable pore structure were obtained.The effect of different freezing temperature（4℃,-20℃,-80℃and -196℃） was investigated in relation to the scaffold morphology,the porosity varied from 91.2%to 83.0%and the average pore diameter varied from（167.2±62.6）μm to（11.9±4.2）μm while theσ₁₀ increased significantly.The cell proliferation were decreased and associated with the above-mentioned properties.Uniform distribution of op-HA particles and homogeneous roughness of pore wall surfaces were found in the 4℃frozen scaffold.The 4℃frozen scaffold exhibited better cell penetration and increased cell proliferation because of its larger pore size,higher porosity and interconnection.The microstructures described here provide a new approach for the design and fabrication of op-HA/PLGA based scaffold materials with potentially broad applicability for replacement of bone defects.     

四氧化三铁中空/螺旋纤维的制备及形成机理

以柠檬酸铁为原料, 利用有机凝胶热分解法在低升温速率下热处理并还原制备了Fe3O4中空/螺旋纤维. 通过TG/DTA, XRD和SEM对前驱体纤维热分解过程、产物物相和形貌进行了表征. 结果表明, 产物主要由80%的中空纤维和20%的螺旋纤维组成, 其中中空纤维的直径为6 μm左右, 壁厚为500 nm. 螺旋纤维的直径为6~10 μm, 螺旋纤维是由具有不同旋向的宽度为4~6 μm的带状纤维卷曲而成, 带状纤维的外表面壳层均匀密实, 其厚度为600 nm左右, 而内层疏松且不规则. Fe3O4中空/螺旋纤维是由晶粒尺寸为60 nm左右的纳米颗粒构成, 并有少量的介孔. 分析了中空纤维和螺旋纤维的形成机理, 直径较小的前驱体纤维在热处理过程中内部凝胶向表层迁移收缩形成中空纤维; 螺旋纤维是由直径较大的前驱体纤维在热处理过程中产生的强大的热应力导致纤维产生螺旋破裂形成的.     

Synthesis,characterization and microwave absorption properties of polyaniline/Sm-doped strontium ferrite nanocomposite

Sm-doped strontium ferrite nanopowders (SrSm_0.3Fe_11.7O₁₉) and their composites of polyaniline (PANI)/SrSm_0.3Fe_11.7O₁₉ with 10 wt% and 20 wt% ferrite were prepared by a sol–gel method and an in-situ polymerization process, respectively. The structure, magnetic properties and microwave absorption properties of the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The particle size of SrSm_0.3Fe_11.7O₁₉ was about 35 nm by using XRD. The ferrite successfully packed by PANI. PANI/SrSm_0.3Fe_11.7O₁₉ possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2–18 GHz. The value of the maximum reflection loss (RL) were −26.0 dB at 14.2 GHz with the 6.5 GHz bandwidth and −24.0 dB at 13.8 GHz with the 7.9 GHz bandwidth for the samples with 10 wt% and 20 wt% ferrite, respectively.     

Polymeric nanocomposite materials: Preparation and characterization of star-shaped PbS nanocrystals and their influence on the thermal stability of acrylonitrile-butadiene-styrene (ABS) copolymer

Star-shaped PbS nanocrystals were synthesized via a simple hydrothermal reaction between Pb(NO₃)₂·4H₂O and thioglycolic acid at a relatively low temperature. The PbS nanostructures were then combined in a acrylonitrile-butadiene-styrene copolymer. The effect of the PbS nanostructures on the thermal stability of the nanocomposite products has been investigated. The nanostructures and nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectra, thermogravimetric-differential thermal analysis and atomic force microscopy. Cone calorimeter measurements showed that the heat release rate significantly decreased in the presence of PbS.     

Preparation and properties of inhalable nanocomposite particles: effects of the size, weight ratio of the primary nanoparticles in nanocomposite particles and temperature at a spray-dryer inlet upon properties of nanocomposite particles

Nanoparticles are expected to be applicable to inhalation as carrier but there exist disadvantages because of their size. Their deposition dose to the lung will be small. To overcome this problem and utilize nanoparticles for inhalation, we have prepared nanocomposite particles as drug carriers targeting lungs. The nanocomposite particles are prepared as drug-loaded nanoparticles–additive complex to reach deep in the lungs and to be decomposed into nanoparticles when they deposit into lung. In this study, we examined the effect of preparation condition – inlet temperature, size of primary nanoparticles and weight ratio of primary nanoparticles – on the property of nanocomposite particles.

When the size of primary nanoparticles was 400 nm and inlet temperature was 90 °C, only the nanocomposite particles containing between 45 and 55% of primary nanoparticles could be decomposed into nanoparticles in water. On the other hand, when the inlet temperature was 80 °C, nanocomposite particles were decomposed into nanoparticles independent of the weight ratio of primary nanoparticles. Also, the aerodynamic diameter of the nanocomposite particles was between 1.5 and 2.5 μm, independent of the weight ratio of primary nanoparticles.

When the size of primary nanoparticles was 200 nm and inlet temperature was 70 °C, nanocomposite particles were decomposed into nanoparticles independent of the weight ratio of primary nanoparticles. Also, the aerodynamic diameters of them were almost 2.0 μm independent of the weight ratio of primary nanoparticles. When the nanocomposite particles containing nanoparticles with the size of 200 nm are prepared at 80 °C, no decomposition into nanoparticles was observed in water.

Fine particle values, FPF, of the nanocomposite particles were not affected by the weight ratio of primary nanoparticles when they were prepared at optimum inlet temperature.     

Preparation and Flame Retardancy of Polyurethane/POSS Nanocomposites

Polyurethane/polyhedral oligomeric sisesquioxane (PU/POSS) nanocomposites were syn-thesized via polymerization utilizing the compatibility between POSS nanoparticles and 4,4'-diphenyl methylene diisocyanate. Scanning electron microscope images and Fouriertransform infrared spectra revealed that POSS nanoparticles were dispersed in PU matrix.Thermal gravimetric analysis was employed to investigate the thermal decomposition be-havior of PU/POSS nanocomposites at elevated temperatures. Then fire performance wasevaluated by limiting oxygen index, underwriters laboratories 94 testing and char residue morphology. These results showed that the addition of POSS promoted the formation of char residues which were covered on the surface of polymer composites, leading to the im-provement of thermal stability and flame retardancy.     

Preparation and characterization of nanocomposite polyurethane

Polyurethane/nanosilica composites were prepared using polyester polyol/nanosilica composite resins obtained from in situ polymerization or blending methods and investigated by Fourier transform infrared spectra (FTIR), dynamical mechanical analysis (DMA), transmittance electron microscopy (TEM), contact angle measurement, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), respectively. It was found that more polyester segments had chemically bonded with silica particles during in situ polymerization than during blending, introducing nanosilica increased the Tgs of polyurethanes, and different preparation methods and different particle sizes caused various impact on Tg. Contact angle measurement and XPS analyses indicated that nanosilica tended to move towards the surfaces and interfaces of polyurethane coats, decreasing the free energies of the surfaces and interfaces, but the nanosilica particles were just observed at interfaces not surfaces by AFM.