Effect of Nonsolvent on the Formation of Polymer Nanomaterials in the Nanopores of Anodic Aluminum Oxide Templates

We study the effect of nonsolvent on the formation of polymer nanomaterials in the nanopores of porous templates. Water (nonsolvent) is added into a poly (methyl methacrylate) (PMMA) solution in dimethylformamide (DMF) confined in the nanopores of an anodic aluminum oxide (AAO) template. Water forms a wetting layer on the pore wall and causes the PMMA solution to be isolated in the center of the nanopore, resulting in the formation of PMMA nanospheres or nanorods after the solvent is evaporated. The formation of the polymer nanomaterials induced by nonsolvent is found to be driven by the Rayleigh‐instability‐type transformation. Without adding the nonsolvent, PMMA chains precipitate on the walls of the nanopores after the solvent is evaporated, and PMMA nanotubes are obtained.     

一步阳极氧化法制备超亲水氧化铝

本文应用一步阳极氧化法在铝表面制作纳米粗糙结构的超亲水表面.考察控槽压、控电流及氧化时间对氧化铝表面超亲水性的影响.测试表明,控电流法更有利于制作超亲水表面,增大电流密度可缩短氧化时间,该法可制作稳定性好、机械强度高的超亲水氧化铝表面,富有潜在的应用价值.     

强烈阳极氧化法快速制备多孔氧化铝模板

In the electrolyte of oxalic acid/alcohol/aqueous solution, highly-ordered porous anodic aluminum oxide(AAO) template was fabricated by hard anodization. The surface morphology and the structure of AAO template were characterized by Field-Emission Scanning Electron Microscope(FE-SEM) and XRD, respectively. The effects of different factors including alcohol type, ratio of alcohol to water, and oxalic acid concentration on the ordering degree and pore diameter of AAO template were investigated. Under the glycol to water ratio of 1∶1(by volume) with an oxalic acid concentration of 0.5 mol·L^-1, and voltage at 160 V, the obtained AAO template was hexangular arrangement with pore diameter of 80 nm and pores spacing of 120 nm, the growth rate was 51.9 μm·h^-1.     

Shaping the Light: The Key Factors Affecting the Photophysical Properties of Fluorescent Polymer Nanostructures

To manipulate the functions of nanomaterials more precisely for diverse applications, the controllability and critical influencing factors of their properties must be thoroughly investigated. In this work, the macroscopic and microscopic effects are studied on the photophysical properties of various pyrene‐ended poly(styrene‐block‐methyl methacrylate) nanostructures. Fluorescent polymer nanospheres, nanorods, and nanotubes are prepared by different template‐based methods using anodic aluminum oxide membranes. Chain arrangements and conformations are determined as the key factors affecting the photophysical properties of the fluorescent polymer nanostructures. This work not only gives a deeper understanding of the effects on the photophysical properties of polymer nanomaterials influenced by morphologies, chain arrangements, and chain conformations, but also provides a reference for designing proper fluorescent nanostructures for specific applications.

     

Three‐Dimensional Block Copolymer Nanostructures by the Solvent‐Annealing‐Induced Wetting in Anodic Aluminum Oxide Templates

Block copolymers have been extensively studied over the last few decades because they can self‐assemble into well‐ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this work, the fabrication and morphologies of three‐dimensional polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) nanostructures confined in the nanopores of anodic aluminum oxide (AAO) templates are studied. It is discovered that the block copolymers can wet the nanopores using a novel solvent‐annealing‐induced nanowetting in templates (SAINT) method. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS‐b‐PDMS nanostructures can be controlled by changing the wetting conditions. Different solvents are used as the annealing solvent, including toluene, hexane, and a co‐solvent of toluene and hexane. When the block copolymer wets the nanopores in toluene vapors, a perpendicular morphology is observed. When the block copolymer wets the nanopores in co‐solvent vapors (toluene/hexane = 3:2), unusual circular and helical morphologies are obtained. These three‐dimensional nanostructures can serve as naontemplates for refilling with other functional materials, such as Au, Ag, ZnO, and TiO₂.

     

阳极氧化物纳米孔道和TiO2纳米管形成机理的研究进展

自组织有序的TiO2纳米管和多孔型阳极氧化膜(PAO)因其潜在的应用价值而倍受关注.阀金属的阳极氧化研究了80多年,但是六棱柱元胞结构和多孔纳米管的形成机理至今尚不清楚.本文不是简单地综述PAO的形成机理,而是从更宽的视角综述了致密型阳极氧化膜与PAO的本质联系和形貌差异.对比两种膜的形貌差异和生长过程有助于孔洞形成本质的认识.简要综述了PAO的传统"场致助溶(FAD)"理论和局限性,重点综述了PAO形成机理的最新研究进展,包括粘性流动模型、阻挡层击穿模型、氧气气泡成孔模型、等电场强度模型等.在充分对比分析最新成果的基础上,对PAO机理研究的发展趋势进行了展望:采用超声氧化、真空或高压条件下氧化以及对电解液中添加碳酸钠或还原剂等方法,对揭示孔洞形成和自组织的本质将会有很大帮助;从电流和阳极氧化效率角度入手,是探究传统FAD理论的物理本质的有效途径.     

铝基阳极氧化铝模板水热法制备TiO2纳米管阵列

在(NH4)2TiF6的水溶液中,以铝基阳极氧化铝为模板,采用水热法制备了TiO2纳米管阵列. 使用场发射扫描电镜和X射线衍射对水热合成产物进行了表征. 实验结果表明,水热处理所得TiO2纳米管阵列具有特殊的形貌,其表面为连续的多孔状,断面为不连续、相互分离的管状;管口和管壁分别由平均粒度约45和25 nm的微细TiO2颗粒紧密堆积而成. 采用本方法制备的TiO2纳米管阵列无需热处理便已具有明显的锐钛矿型晶相特征.     

阳极氧化铝模板法可控制备金属纳米线和纳米管阵列的生长机制

利用阳极氧化铝模板(AAO)进行Ni的电化学沉积, 通过在溶液中引入螯合剂控制电解质的有效浓度和电沉积的过电位, 实现了Ni纳米线和纳米管阵列的可控制备. 通过分析电沉积过程中纳米线和纳米管在不同位置生长速率(侧壁(Vw)和底端(Vb))的控制因素, 我们提出了纳米线和纳米管生长的可能机制. 当电解质浓度高而还原电位更负(如-1.5 V)时, 或者当电解质浓度低而还原电位较负(如-0.5 V)时, Vw>Vb, 可以获得Ni纳米管阵列; 当电解质浓度高而还原电位较负(如-0.5 V)时, 或者当电解质浓度低而还原电位更负(如-1.5 V)时, Vw≈Vb, 可以获得Ni纳米线阵列. 这种生长机制适用于多种金属纳米管或者纳米线阵列的可控制备.     

Preparation of Polyelectrolyte Nanotubes by a Pressure filter-template Technique Using Microporous Anodic Aluminum Oxide (AAO) as the Template

Polyelectrolyte nanotubes of poly(sodium 4‐styrene‐sulfonate) (PSS) with cationic poly(diallyl dimethyl ammonium chloride) (PDDA) (PSS/PDDA) were fabricated by a pressure‐filter‐template technique using microporous anodic aluminum oxide (AAO) as the template. UV‐Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and infrared spectroscopy (FT‐IR) were applied to characterize the obtained PSS/PDDA nanotubes. The results have shown that the PSS/PDDA nanotubes exhibit an amorphous structure and have the outer diameter of 200 nm and length of 25 µm respectively, which are in good agreement with the dimensions of the AAO template pores. The wall thickness of the nanotubes may be controlled by the number of the self‐assembled layers. Formation of the nanotubes follows a layer‐by‐layer (LbL) mechanism due to the electrostatic interactions, where the SO^?₃ groups of PSS are first adsorbed on the Lewis acid sites of AAO template pores.     

大长径比有序多孔阳极氧化铝模板的制备及用于镍纳米线阵列

报道一种恒电流二次氧化制备大长径比(>1000)阳极氧化铝(AAO)模板的方法,研究氧化时间和氧化电流密度分别对制备的AAO模板的表面形貌、孔径大小、厚度等的影响.结果表明,AAO模板的表面形貌及厚度n受m氧、厚化度电约流为密2度00及μ氧m、化长时径间比的为影10响0;-当13氧00化的电高流质密量度A为AO8模m板A·.c采m用-2电时化,氧学化沉1积8方h能法在制制备备出的孔A径A为O模15板0-的20孔0中成功制备了Ni纳米线阵列,分别用扫描电镜(SEM)、高分辨透射电镜(HRTEM)、X射线衍射(XRD)和X射线能量散射光谱(EDS)对其进行了表征;结果显示,制备的Ni纳米线排列整齐有序,每根Ni纳米线直径几乎相同,约150nm,长度约为180-200μm,长径比为1200-1300,与AAO模板的参数一致.研究了Ni纳米线阵列的长径比对其磁性能的影响,发现大长径比的Ni纳米线阵列具有明显的磁各向异性,而长径比约为200的Ni纳米线阵列未表现出明显的磁各向异性.本文结果表明,恒电流二次氧化方法能制备大长径比的AAO模板,并能用于制备大长径比的一维纳米材料阵列,可望在制备具有特殊光学、磁学等性能材料方面得到应用.     

多孔质铝阳极氧化膜表面与界面研究

铝质材料阳极氧化作为铝质材料最重要的表面改性技术已有几十年历程，并在现代工业中获得了广泛应用［1，’］．前人对铝阳极氧化股的结构、组成及生成机理等进行了大量的研究工作［3－6］，研究结果表明铝阳极氧化膜具有多孔型和壁垒型二种，其中多孔型铝阳极氧化膜是由非晶态     

Preparation of Latexes with Poly(Methyl Methacrylate) Cores and Hydrophilic Polymer Shells Containing Amino Groups

Abstract

Functional latexes with poly(methyl methacrylate) (PMMA) cores and amino‐containing, water‐soluble polymer shells were synthesized via direct graft copolymerization of methyl methacrylate from water‐soluble polymers induced by a small amount of tert‐butyl hydroperoxide (TBHP) at 80°C for 2 h. Amphiphilic graft copolymers and PMMA homopolymers were generated concurrently to form highly monodispersed latexes. The effects of water‐soluble polymer containing different amino group, reaction temperature, TBHP concentration, molecular weight of the polymer and pH of the solution on conversion and grafting efficiency of the monomer and particle size were investigated. Transmission electron microscopic images of the PMMA/poly(ethyleneimine) (PEI) and PMMA/poly(allylamine) (PAA) particles clearly show well‐defined core‐shell morphologies, where PMMA cores are coated with either PEI or PAA shell. The amino‐containing polymer shells were also confirmed with zeta‐potential measurements. Furthermore, the amino‐containing latexes can be produced with a solids content up to 22 wt.%. Thus, this method provides a commercially viable route to functional latexes.     

Synthesis and Characterizations of Copolymers Containing Both Phosphatidylcholine Analogues and Poly(Ethylene Glycol) in the Side Chains

Abstract

New phospholipid analogous polymers were prepared by radical copolymerizations of 2-(methacryloyloxy)ethyl-2-(trimethylammonio)-ethyl phosphate and poly(ethylene glycol)monomethylether methacrylates (PEGMM) at room temperature, using (NH₄)₂S₂O₈ as the initiator and pure water as the solvent. The copolymers obtained were characterized based on their IR, ¹H-, and ¹³C-NMR spectral data and melting point measurements. The molecular weights of these copolymers decrease as the length of the PEGMM side chain increases. These new polymers, which contain phosphatidylcholine analogous groups in their side chains, show viscosity properties similar to typical polyelectrolytes.     

Linear Azo Polymer Containing Conjugated 5,5′‐Azodisalicylic Acid Segments in the Main Chain: Synthesis,Characterization, and Degradation

Summary: Copolymers of poly(ethylene oxide) (PEO) and 5,5′‐azodisalicylic acid (Olsalazine, OLZ) were synthesized and evaluated by hydrolysis and in‐vitro biodegradation with azoreductase. It was found that changing the molecular weight of the PEO blocks affected the loading ratio of OLZ, and resulted in significant differences in the hydration and degradability of the copolymers. These novel azo‐containing copolymers can be used in colon‐specific drug delivery.

Release of 5‐ASA from OLZ and PEO‐OLZ copolymers incubated with rat cecum content in the presence of benzyl viologen and α‐D ‐glucose.     

Hybrid Materials from Carbon Nanotubes,Nickel Tetrasulfonated Phthalocyanine and Thin Polymer Layers for the Selective Electrochemical Activation of Nitric Oxide in Solution

The elaboration of hybrid materials from single‐wall carbon nanotubes (SWCNT) and tetrasulfonated nickel phthalocyanine (NiTSPc) was electrochemically performed to obtain chemically modified electrodes with improved electrocatalytic activity towards the electrooxidation of nitric oxide (NO). The characterization of these hybrid electrodes was achieved by cyclic voltammetry and AFM. The electrochemical performances of the electrodes towards the oxidation of NO were then analyzed by chronoamperometry and the obtained results show that the presence of SWCNT greatly enhances the electrocatalytic performances in terms of current intensity. Additional coatings were then electrodeposited over the hybrid electrodes to act as selective membranes against four major interfering analytes: nitrite, ascorbate, hydrogen peroxide and L ‐arginine. Several polymer coatings were tested to achieve the best balance between sensitivity to NO and selectivity against interferents.