Study on diffusion of electroactive species in polyelectrolyte polyethylene glycol lithium perchlorate by chronoamperometry at a microdisk electrode

The mass transport dynamics of Ferrocene in polyelectrolyte polyethylene glycol lithium perchlorate (PEG . LiClO4) was studied by using chronoamperometry at a microdisk electrode. Chronoamperometry is a powerful method for the study of mass transport in polyelectrolyte, it has many advantages over the conventional methods at a microelectrode and the steady-state method at an ultramicroelectrode. By using this method the apparent diffusion coefficient D-app and concentration C-a of the electroactive species, can be estimated from a single experiment without previous knowledge of either one. We have estimated D-app and C-a of ferrocene in PEG . LiClO4 polyelectrolyte from 25 degrees C to 75 degrees C. The dependence on the concentration of electroactive species was observed. The diffusion coefficients decrease with increasing ferrocene concentration and decreasing temperature. The mass transport mechanism is explained, by using a free volume model.

AN INTEGRATED CALCIUM-FLUORIDE CRYSTAL IR THIN-LAYER CELL AND ITS APPLICATION TO IDENTIFICATION OF ELECTROCHEMICAL REDUCTION PRODUCT OF BILIRUBIN

An integrated CaF2 crystal optically transparent infrared (ir) thin-layer cell was designed and constructed without using any soluble adhesive materials. It is suitable for both aqueous and nonaqueous systems, and can be used not only in ir but also in uv-vis studies. Excellent electrochemical and spectroelectrochemical responses were obtained in evaluating this cell by cyclic voltammetry and steady-state potential step measurements for both ir and uv-vis spectrolectrochemistry with ferri/ferrocyanide in aqueous solution, and with ferrocene/ferrocenium in organic solvent as the testing species, respectively. The newly designed ir cell was applied to investigate the electrochemical reduction process of bilirubin in situ, which provided direct information for identifying the structure of the reduction product and proposing the reaction mechanism.

A NOVEL DESIGN OF LIGHT-TRANSPARENT GOLD-MINIGRID THIN-LAYER FTIR SPECTROELECTROCHEMICAL CELL WITH VERTICAL CONFIGURATION

A Teflon bridge/edge-eliminator is designed to connect a glass container and a light-transparent gold-minigrid NaCl thin-layer cell to form a vertically configured in-situ FTIR spectroelectrochemical cell. The bridge/edge-eliminator sets an internal reference point for accurate potential control. The size of the thin-layer chamber is 5 X 5 X 0.11mm. A 1900-omega formal resistance of the thin-layer cell was measured in CH2Cl2/0.1 M TBAP solution. Well defined thin-layer cyclic voltammograms and IR spectral changes for ferrocene oxidation were obtained.

微流体芯片表面化学修饰与键合

微全分析系统(μ-TAS)，即芯片实验室，在过去的十几年中发展迅速，通过微加工技术将芯片片基蚀刻成各种微米结构的微通道网络或点阵结构,再将其表面进行化学改性,使其表面生成羟基、氨基或醛基等生化活性的官能团，用于固定化酶，蛋白质，抗原抗体或无机催化剂，也可以修饰电极或色谱等，还是构建自组装的基础,其片基表面的氨基是重要的反应基团，能使成千上万个与生命相关的信息集成在一块厘米见方的芯片上，进行生命科学和医学中的各种生物化学反应,为此本论文主要就以下方面开展研究工作： 1 研究了用灵敏度较高9-蒽醛检测不同氨基硅氧烷在玻璃或石英片基表面的组装过程，氨丙基三乙氧基硅烷和氨丙基二乙氧基甲基硅烷随时间增长生成多层网状结构，而氨丙基二甲基乙氧基硅烷和氨丙基二甲基甲氧基硅烷则生成饱和单层膜。 2 研究了溶液中的可控自组装方法，通过在片基表面交替进行二醛和二胺的缩聚反应，生成共轭芳香亚胺聚合物；或交替进行二酐和二胺的交替组装，制备应用于各种电子器件的p-堆积、有序和取向多层膜，利用紫外可见光谱监测单体的组装过程，谱线形状随着单体的交替变化而变化，所得组装膜热稳定性很好。 3 提供了利用组装双官能团化合物或甲基丙烯酸缩水甘油酯的ATRP反应在300 ℃键合玻璃或石英片基的方法，剪切强度在15 kg/cm2以上，键合层清晰透明，厚度在30-60 nm，不会阻塞微流体的内部管道。 4 在氨基化片基表面组装2-甲酰吡啶、6-甲酰基-2,2’-联吡啶和6-甲酰基-2,2’: 6’,2”-三联吡啶及相应的钌络合物。

活性/可控聚合法合成旋光性聚甲基丙烯酸（上艹下孟）酯

本论文合成了旋光性甲基丙烯酸（上艹下孟）酯（MnMA）、并分别用阴离子聚合，基团转移聚合（GTP），自由基聚合及原子转移自由基聚合（ATRP）方法对其进行了聚合研究，考查了不同聚合方法对其聚合能力、聚合物微观结构及旋光性的影响，主要结论如下：1.在MnMA的阴离子聚合中，分别加人(+)DDB、（-）Sp, TMEDA等配体后，聚合能力明显增强。2.（-）一MAMA的阴离子聚合所得聚合物的比旋光值随其分子量的增加略有增加；手性与非手性引发体系及不同聚合方法对聚甲基丙烯酸莹醋的比旋光值影响均较小。2.不同聚合方法对聚甲基丙烯酸盏酷的立构规整性的影响程度不同，且所得聚合物的全同含量均较低。4.以甲基丙烯酸三苯基甲酷（TrMA）作为活性预聚物可以诱导MnMA、乙烯基三苯基磷(VTPP）等大位阻单体聚合，实现螺旋诱导不对称聚合。5.采用ATRP及反向ATRP对（-）-MnMA进行了聚合研究，结果表明：(1)（-）MriMA的非均相ATRP研究表明，不同引发剂及配体对其聚合影响程度不同，2一澳丙酸乙醋(2-EBP)/CuCl/2,2'-联毗陡(bipy)/THF体系的引发效率最高，体系所得聚合物的分子量分布最窄，可控性最好。(2)（-)MnMA的两均相ATRP体系2-BP/CuCl/(-)-Sp(or dHbpy)ffHF所得聚合物分子量随转化率的变化基本呈直线关系，分子量分布均控制在1.2以下。(3)对(-)MnMA反向ATRP研究表明，AIBN/CuC12/bipy(or (-)-Sp)fFBF体系的动力学曲线呈一级线性关系，分子量随转化率的变化基本呈直线增加，可控性较好。(4) ATRP及反向ATRP体系中所得聚合物的比旋光值绝对值随分子量的增加略有减小。

Surface Initiated Polymerization from Substrates of Low Initiator Density and Its Applications in Biosensors

Surface initiated polymerization (SIP) has become an attractive method for tailoring physical and chemical properties of surfaces for a broad range of applications. Most of those application relied on the merit of a high density coating. In this study we explored a long overlooked field of SIP. SIP from substrates of low initiator density. We combined ellipsometry with AFM to investigate the effect of initiatior density and polymerization time on the morphology of polymer coatings. In addition, we carefully adjusted the nanoscale separation of polymer chains to achieve a balance between nonfouling and immobilization capacities. We further tested the performance of those coating on various biosensors, such as quartz crystal microbalance, surface plasmon resonance, and protein microarrays. The optimized matrices enhanced the performance of those biosensors. This report shall encourage researches to explore new frontiers in SIP that go beyond polymer brushes.

A strategy for synthesis of ion-bonded supramolecular star polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization

We have developed a novel strategy for the preparation of ion-bonded supramolecular star polymers by RAFT polymerization. An ion-bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert-butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by H-1 NMR and GPC. The results show that the polymerization possesses the character of living free-radical polymerization and the ion-bonded supramolecular star polymers PSt, PtBA, and PSt-b-PtBA, with six well-defined arms, were successfully synthesized.

A strategy for synthesis of ion-bonded amphiphilic miktoarm star copolymers via supramolecular macro-RAFT agent

Amphiphilic supramolecular miktoarm star copolymers linked by ionic bonds with controlled molecular weight and low polydispersity have been successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using an ion-bonded macromolecular RAFT agent (macro-RAFT agent). Firstly, a new tetrafunctional initiator, dimethyl 4,6-bis(bromomethyl)-isophthalate, was synthesized and used as an initiator for atom transfer radical polymerization (ATRP) of styrene to form polystyrene (PSt) containing two ester groups at the middle of polymer chain. Then, the ester groups were converted into tertiary amino groups and the ion-bonded supramolecular macro-RAFT agent was obtained through the interaction between the tertiary amino group and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP). Finally, ion-bonded amphiphilic miktoarm star copolymer, (PSt)(2)-poly(N-isopropyl-acrylamide)(2), was prepared by RAFT polymerization of N-isopropylacrylamide (NIPAM) in the presence of the supramolecular macro-RAFT agent. The polymerization kinetics was investigated and the molecular weight and the architecture of the resulting star polymers were characterized by means of H-1-NMR, FTIR, and GPC techniques. (c) 2008 Wiley Periodicals, Inc.

Effect of block sequence and block length on the stimuli-responsive behavior of polyampholyte brushes: hydrogen bonding and electrostatic interaction as the driving force for surface rearrangement

Diblock polyampholyte brushes with different block sequences (Si/SiO2/poly(acrylic acid)-b-poly (2-vinylpyridine) (PAA-b-P2VP) brushes and Si/SiO2/P2VP-b-PAA brushes) and different block lengths were synthesized by sequent surface-initiated atom transfer radical polymerization (ATRP). The PAA block was obtained through hydrolysis from the corresponding poly(tert-butyl acrylate). The polyampholyte brushes demonstrated unique pH-responsive behavior. In the intermediate pH region, the brushes exhibited a less hydrophilic wetting behavior and a rougher surface morphology due to the formation of polyelectrolyte complex through electrostatic interaction between oppositely charged blocks. In the low pH and high pH regions, the rearrangement of polyampholyte brushes showed great dependence on the block sequence and block length. The polyampholyte brushes with P2VP-b-PAA sequence underwent rearrangement during alternative treatment by acidic aqueous solution (low pH value) and basic aqueous solution (high pH value).

Synthesis and self-assembly of poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate)

Poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate) (PEO-b-PHEMA) was synthesized by successive atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate(HEMA) monomer using PEO-Br macroinitiator as initiator, CuBr/CuBr2 and 2,2.-bipyridyl (bpy) as catalyst and ligand. IR, H-1 NMR, and GPC analysis indicate that PEO-b-PHEMA block copolymer with low polydispersity index (M-w/M-n approximate to 1.1) has been formed. Self-assembly of this double hydrophilic block copolymer in the selective solvent and water was also studied. Owing to the high hydrophilic nature of the PEO and PHEMA blocks, this double hydrophilic block copolymer cannot disperse well in water. So block copolymer was modified by part esterification of PEO-b-PHEMA with acetic anhydride, which increased the hydrophobic group of the PHEMA block. The TEM results show that this block copolymer spontaneously form well-defined micelles in water.

Macrocycle-Terminated Core-Cross-Linked Star Polymers: Synthesis and Characterization

We have synthesized macrocyclic polystyrene- (PS-) terminated PS star polymers via a core-cross-linking approach in this work. A tadpole-shaped macrocyclic PS-linear-PS copolymer was synthesized at first via click chemistry and ATRP polymerization method. The "living" ATRP initiating chain-ends of the tadpole-shaped copolymers were linked together via ATRP polymerization with divinylbenzene to form a core-cross-linked macrocyclic star polymer. The number of arms attached to the macrocyclic star polymers was measured with NMR. and absolute molecular weights with gel permeation chromatography (GPC) with multiangle laser light scattering detector. These macrocyclic star polymers had a highly cross-linked core and many radiating arms. The shorter tadpole-shaped precursors caused core-cross-linked star polymers with higher molecular weights and more arm numbers. The macrocycle-terminated core-cross-linked star polymers showed two glass transition temperatures, one arising from the linear branches and another from the macrocycles.

Synthesis of Arm-6 polystyrene by atom transfer radical polymerization

A new initiator for atom transfer radical polymerization (ATRP), (Cl-2 HCCOO)(3) -C-6 H-3, (TrDCAP),has been designed and successfully synthesized. ATRP of styrene was carried out by using TrDCAP as hexafunctional initiator and the CuCl/bpy catalyst at 130 degrees C in 30% THF via core-first strategy. The Arm-6 PS-AAP was synthesized by etherealization of Arm-6 PS and 4-(4'-methoxyphenylazomethine) phenol (AAP). The initiator and the architectures of the Arm-6 PS were confirmed by H-1-NMR, FT-IR, UV-Vis and GPC.

Synthesis of a (sic)-shaped amphiphilic block copolymer by the combination of atom transfer radical polymerization and living anionic polymerization

The functionalization of monomer units in the form of macroinitiators in an orthogonal fashion yields more predictable macromolecular architectures and complex polymers. Therefore, a new there exists E-shaped amphiphilic block copolymer, (PMMA)(2)-PEO-(PS)(2)-PEO-(PMMA)(2) [where PMMA is poly(methyl methacrylate), PEO is poly (ethylene oxide), and PS is polystyrene], has been designed and successfully synthesized by the combination of atom transfer radical polymerization (ATRP) and living anionic polymerization. The synthesis of meso-2,3-dibromosuccinic acid acetate/diethylene glycol was used to initiate the polymerization of styrene via ATRP to yield linear (HO)(2)-PS2 with two active hydroxyl groups by living anionic polymerization via diphenylmethylpotassium to initiate the polymerization of ethylene oxide. Afterwards, the synthesized miktoarm-4 amphiphilic block copolymer, (HO-PEO)(2)-PS2, was esterified with 2,2-dichloroacetyl chloride to form a macroinitiator that initiated the polymerization of methyl methacrylate via ATRP to prepare the there exists E-shaped amphiphilic block copolymer.

Motion of integrated CdS nanoparticles by phase separation of block copolymer brushes

A new method of reversibly moving US nanoparticles in the perpendicular direction was developed on the basis of the phase separation of block copolymer brushes. Polystyrene-b-(poly(methyl methaerylate)-co-poly(cadmium dimethacrylate)) (PS-b-(PMMA-co-PCdMA)) brushes were grafted from the silicon wafer by surface-initiated atom transfer radical polymerization (ATRP). By exposing the polymer brushes to H2S gas, PS-b-(PMNlA-co-PCdNlA) brushes were converted to polystyrene-b-(poly(methyl methacrylate) -co-poly(methacrylic acid)(CdS)) (PS-b-(PMMA-co-PMAA(CdS))) brushes, in which US nanoparticles were chemically bonded by the carboxylic groups of PMAA segment. Alternating treatment of the PS-b-(PMMA-co-PMAA(CdS)) brushes by selective solvents for the outer block (a mixed solvent of acetone and ethanol) and the inner PS block (toluene) induced perpendicular phase separation of polymer brushes, which resulted in the reversible lifting and lowering of US nanoparticles in the perpendicular direction. The extent of movement can be adjusted by the relative thickness of two blocks of the polymer brushes.

Bonding quartz wafers by the atom transfer radical polymerization of the glycidyl methacrylate at mild temperature

In this paper, we presented a novel covalent bonding process between two quartz wafers at 300 degrees C. High-quality wafer bonding was formed by the hydroxylization, aminosilylation and atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA), respectively, on quartz wafer surfaces, followed by close contact of the GMA functional wafer and the aminosilylation wafer, the epoxy group opening ring reaction was catalyzed by the amino and solidified to form the covalent bonding of the quartz wafers. The shear force between two wafers in all bonding samples was higher than 1.5 MPa. Microfluidic chips bonded by the above procedures had high transparency and the present procedure avoided the adhesive to block or flow into the channel.