硅表面分子刷图案化及生长DNA纳米管

结合"自上而下"和"自下而上"技术构建微纳米器件是目前纳米科学和技术领域追逐的目标之一。本文首先采用硅氢化反应在硅表面共价偶联引发聚合的活性基团,接着实施表面原子转移自由基聚合(ATRP)反应形成高分子刷poly(PEGMA),采用"自上而下"的光刻技术在硅表面制备功能化的图案,最后利用"自下而上"的DNA自组装技术在图案部分原位生长DNA纳米管。上述组装过程通过多次透射反射红外光谱、凝胶电泳、透射电镜和扫描电镜进行了检测,证实了硅芯片表面定位生长DNA纳米管的可行性。     

在云母晶面上应用“自下而上”和“自上而下”两种途径制造胶原蛋白纳米线阵列

以云母晶体的（001）晶面为基质,以天然Ⅰ型鼠尾胶原蛋白单体溶液为原料,分别考察了蛋白单体受基质规导进行“自下而上”的自组装过程,以及原子力显微镜探针对吸附在基质表面的蛋白膜层进行“自上而下”加工过程：（1） 两种制备途径均能 加工出结构精确可控的胶原蛋白纳米线阵列;（2） “自下而上”制备途径利用了蛋白单体和基质晶体在界面上互相识别并规范的“反相生物矿化”原理;（3） “自上而下”的加工利用了原子力显微镜接触模式下探针的“分子扫帚”机理。     

DNA在氨基功能化偶氮苯自组装膜表面的固定

采用简单快速的方法制备出将DNA固定在其表面的单分子层敏感膜.首先采用表面自组装技术将硅氧烷基偶氮苯衍生物H2NAzoCONHC3Si(OCH3)3(APDA-N-TMSPBA)组装在硅表面,在详细考察单分子层薄膜的化学结构、表面浸润性和分子表面形貌之后,又通过紫外吸收光谱(UV)在位考察了硅氧烷基偶氮苯衍生物的光学异构特性.在DNA在自组装薄膜固定后,X光电子能谱仪(XPS)结果显示出现了明显的磷元素信号,表明DNA分子可以成功固定在自组装膜表面.     

规则结构钛酸盐自组装聚集体的制备

在水热条件下, 采用不同的钛源, 通过控制溶液碱度和冷却温度等反应条件, 利用无模板自组装技术, 在钛酸盐薄膜表面及溶液相中制备了鸟巢状和绒球状钛酸盐纳米带自组装聚集体以及海胆状钛酸盐纳米管自组装聚集体. 通过引入碳酸钠模板, 制备出形貌新颖的钛酸钠-碳酸钠香蒲状自组装聚集体复合材料. 初步研究了纳米自组装聚集体的形成机理, 认为其形成经历了一维纳米结构(纳米带或纳米管)的生长和一维纳米结构的自组装2个过程.     

甲基丙烯酸丁酯在纳米TiO2表面的原位接枝

利用分子自组装技术,对纳米TiO2粒子表面组装上有机单分子层,使其带上不饱和基团C=C,在自组装单分子层表面原位引发甲基丙烯酸丁酯（BMA）单体聚合反应,使纳米TiO2表面形成化学键合的聚合物层,达到对纳米TiO2粒子改性的目的。讨论了不同反应条件对接枝聚合率的影响,通过FTIR、TG-DTA等分析手段,研究聚合改性物质的结构和改性后纳米TiO2粒子的分散稳定性。实验发现聚合改性后的纳米TiO2在有机相中有良好的分散性。     

硫醇自组装膜对金电极上吡咯电化学聚合的影响

用电化学聚合法在多种烷基硫醇自组装膜修饰金电极上制备了聚吡咯.通过计时安培法、循环伏安法和交流阻抗技术研究了自组装膜的烷基链长和端基功能团对吡咯聚合过程和性质的影响.当自组装膜较完美时,聚吡咯沉积在自组装膜表面;而当自组装膜有一定缺陷时,吡咯在针孔处成核,然后继续生长并完全覆盖在自组装膜表面.研究结果表明,烷基硫醇的链越短,吡咯聚合越容易;疏水的烷基硫醇自组装膜有利于聚吡咯在电极表面的生长.     

硅表面有机单层膜 :微印章、微加工与微阵列

总结了作者的实验室在将有机物结合到硅表面方面的研究进展.发现并发展了将有机单层膜组装到硅、氧化硅和相关材料表面的新方法.这些方法简单、可重复，并可得到物理、化学性能良好的致密单层膜.这些单层膜在许多方面有令人鼓舞的应用，包括（a）应用于软印刷术，特别是微接触印章法; （b）用作硅的微加工（微机电系统，MEMS）的单层膜润滑剂; （c）用作DNA和蛋白质微阵列功能分子固定的基底.     

氮化钛纳米管作为钒电池负极对V(Ⅱ)/V(Ⅲ)的电化学性能

采用阳极氧化法在钛箔表面原位生长二氧化钛纳米管,随后在氨气氛围中氮化还原制备氮化钛纳米管,并将此电极直接作为钒电池的负极,研究其对V（Ⅱ）/V（Ⅲ）的电化学性能。通过X射线衍射（XRD）、扫描电镜（SEM）以及X射线光电子能谱（XPS）等材料测试手段对氮化钛纳米管的形貌、组成和结构进行表征。分析结果表明,氨气高温氮化后,前驱体TiO₂相转变为TiN和Ti₂N相,表面元素组成为Ti-N-O,Ti-N和Ti-O,且其形貌仍保持纳米管的微观结构。采用循环伏安,电化学阻抗和充放电测试表明,氮化钛纳米管对负极电解液中的V（Ⅱ）/V（Ⅲ）展现了优异的电催化活性和可逆性,这主要归因于氮化钛纳米管大的电化学真实表面积和快速的电子转移通道。     

单壁碳纳米管在金表面的图形化组装

利用湿法化学组装技术在金表面得到了图形化的单壁碳纳米管阵列.在混酸氧化条件下,初合成的交缠状态的单壁纳米管被截短成带有羧基等功能化末端的短管.这些功能化的短管在缩合剂DCC的作用下与氨基/甲基图形化表面进行缩合反应时,纳米管将选择性地结合到氨基区域从而形成规则的纳米管阵列.     

硅纳米管负载的钌基催化剂费-托合成催化性能研究

以模板法合成的硅纳米管（SNT）为载体,用浆态浸渍法制备了钌基催化剂,采用氮气物理吸附、透射电子显微镜（TEM）、X射线粉末衍射（XRD）和氢气程序升温还原（H₂-TPR）等手段对其进行了表征。在固定床反应器上（503K,1.0MPa）考察了该催化剂的费-托合成反应活性及产物选择性,并与用商业二氧化硅为载体制备的催化剂上的反应结果进行了比较。结果表明,SNT和SiO₂负载的氧化钌在623K可被H₂完全还原;SNT负载的钌基催化剂上,钌氧化物颗粒较小、分散性好,还原后钌颗粒被较好地分散在硅纳米管上,且几乎所有的钌颗粒都分布在管内。与以SiO₂为载体的催化剂相比,以硅纳米管为载体的钌基催化剂具有较高的费-托合成活性。     

NHS-ester functionalized poly(PEGMA) brushes on silicon surface for covalent protein immobilization

Poly(PEGMA) homopolymer brushes were developed by atom transfer radical polymerization (ATRP) on the initiator-modified silicon surface (Si-initiator). Through covalent binding, protein immobilization on the poly(PEGMA) films was enabled by further NHS-ester functionalization of the poly(PEGMA) chain ends. The formation of polymer brushes was confirmed by assessing the surface composition (XPS) and morphology (atomic force microscopy (AFM), scanning electronic microscopy (SEM)) of the modified silicon wafer. The binding performance of the NHS-ester functionalized surfaces with two proteins horseradish peroxidase (HRP) and chicken immunoglobulin (IgG) was monitored by direct observation. These results suggest that this method which incorporates the properties of polymer brush onto the binding surfaces may be a good strategy suitable for covalent protein immobilization.     

Functionalization of hydrogen-terminated silicon via surface-initiated atom-transfer radical polymerization and derivatization of the polymer brushes

Surface-initiated atom-transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethacrylate (PEGMA) was carried out on the hydrogen-terminated Si(100) substrates with surface-tethered alpha-bromoester initiator. Kinetic studies confirmed an approximately linear increase in polymer film thickness with reaction time, indicating that chain growth from the surface was a controlled "living" process. The "living" character of the surface-grafted PEGMA chains was further ascertained by the subsequent extension of these graft chains, and thus the graft layer. Well-defined polymer brushes of near 100 nm in thickness were grafted on the Si(100) surface in 8 h under ambient temperature in an aqueous medium. The hydroxyl end groups of the poly(ethylene glycol) (PEG) side chains of the grafted PEGMA polymer were derivatized into various functional groups, including chloride, amine, aldehyde, and carboxylic acid groups. The surface-functionalized silicon substrates were characterized by reflectance FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). Covalent attachment and derivatization of the well-defined PEGMA polymer brushes can broaden considerably the functionality of single-crystal silicon surfaces.     

Atom transfer radical polymerization directly from poly(vinylidene fluoride): Surface and antifouling properties

The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface‐initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) with the reaction time, indicating that the chain growth from the surface was consistent with a controlled or living process. The living chain ends were used as macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA‐grafted PVDF films and PDMAEMA‐grafted PVDF films in comparison with the pristine PVDF surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3434–3443, 2006     

Functionalization of nylon membranes via surface-initiated atom-transfer radical polymerization

The ability to manipulate and control the surface properties of nylons is of crucial importance to their widespread applications. In this work, surface-initiated atom-transfer radical polymerization (ATRP) is employed to tailor the functionality of the nylon membrane and pore surfaces in a well-controlled manner. A simple two-step method, involving the activation of surface amide groups with formaldehyde and the reaction of the resulting N-methylol polyamide with 2-bromoisobutyryl bromide, was first developed for the covalent immobilization of ATRP initiators on the nylon membrane and its pore surfaces. Functional polymer brushes of 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol)monomethacrylate (PEGMA) were prepared via surface-initiated ATRP from the nylon membranes. A kinetics study revealed that the chain growth from the membranes was consistent with a "controlled" process. The dormant chain ends of the grafted HEMA polymer (P(HEMA)) and PEGMA polymer (P(PEGMA)) on the nylon membranes could be reactivated for the consecutive surface-initiated ATRP to produce the corresponding nylon membranes functionalized by P(HEMA)-b-P(PEGMA) and P(PEGMA)-b-P(HEMA) diblock copolymer brushes. In addition, membranes with grafted P(HEMA) and P(PEGMA) brushes exhibited good resistance to protein adsorption and fouling under continuous-flow conditions.     

Branched fluoropolymer-Si hybrids via surface-initiated ATRP of pentafluorostyrene on hydrogen-terminated Si(100) surfaces

Linear, branched, and arborescent fluoropolymer-Si hybrids were prepared via surface-initiated atom transfer radical polymerization (ATRP) from the 4-vinylbenzyl chloride (VBC) inimer and ClSO(3)H-modified VBC that were immobilized on hydrogen-terminated Si(100), or Si-H, surfaces. The simple approach of UV-induced coupling of VBC with the Si-H surface provided a stable, Si-C bonded monolayer of "monofunctional" ATRP initiators (the Si-VBC surface). The aromatic rings of the Si-VBC surface were then sulfonated by ClSO(3)H to introduce sulfonyl chloride (-SO(2)Cl) groups and to give rise to a monolayer of "bifunctional" ATRP initiators. Kinetics study indicated that the chain growth of poly(pentafluorostyrene) from the functionalized silicon surfaces was consistent with a "controlled" or "living" process. The chemical composition and functionality of the silicon surface were tailored by the well-defined linear and branched fluoropolymer brushes. Atomic force microscopy images revealed that the surface-initiated ATRP of pentafluorostyrene (PFS) had proceeded uniformly on the Si-VBC surface to give rise to a dense and molecularly flat surface coverage of the linear brushes. The uniformity of surfaces with branched brushes was controlled by varying the feed ratio of the monomer and inimer (VBC in the present case). The living chain ends on the functionalized silicon surfaces were used as the macroinitiators for the synthesis of diblock copolymer brushes, consisting of the PFS and methyl methacrylate polymer blocks.     

Disubstituted polyacetylene brushes grown via surface-directed tungsten-catalyzed polymerization

Disubstituted polyacetylene brushes were grown from modified silicon and quartz surfaces using a transition metal-catalyzed polymerization technique employing tungsten hexachloride/tetraphenyl tin (WCl6/Ph4Sn). The substrate surfaces were initially functionalized with terminal alkyne functional groups by using an alkyne-functionalized silane, O-(propagyloxy)-N-(triethoxysilylpropyl) urethane, as a surface coupling agent. Surface polymerization of 5-decyne under microwave irradiation at 150 degrees C for 30 min was performed on the functional surfaces to produce surfaces consisting of grafted poly(1,2-dibutylacetylene) brushes. The alkyne-functionalized and polymer-coated surfaces were characterized using surface contact angle measurements, film thickness measurements, atomic force microscopy, and X-ray photoelectron spectroscopy, and fluorescence spectrometer measurements were performed to analyze the surfaces at each step of the modification process. This simple technique demonstrates a novel way of synthesizing a poly(1,2-dibutylacetylene) brush layer on silicon substrate, and it has future potential in the fabrication of selectively functionalized surfaces on the nanoscale via this new synthetic approach.     

Tethering hydrophilic polymer brushes onto PPESK membranes via surface-initiated atom transfer radical polymerization

Surface-initiated atom transfer radical polymerization (ATRP) was used to graft hydrophilic comb-like poly((poly(ethylene glycol) methyl ether methacrylate), or P(PEGMA), brushes from chloromethylated poly(phthalazinone ether sulfone ketone) (CMPPESK) membrane surfaces. Prior to ATRP, chloromethylation of PPESK was beforehand performed and the obtained CMPPESK was prepared into porous membranes by phase inversion process. It was demonstrated that the benzyl chloride groups on the CMPPESK membrane surface afforded effective macroinitiators to graft the well-defined polymer brushes. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) chains. Water contact angle measurements indicated that the introduction of P(PEGMA) graft chains promoted remarkably the surface hydrophilicity of PPESK membranes. The effects of P(PEGMA) immobilization on membrane morphology, permeability and fouling resistance were investigated. It was found that the comb-like P(PEGMA) grafts brought smaller pore diameters and higher solute rejections to PPESK membranes. The results of dynamic anti-fouling experiments showed the anti-fouling ability of the membranes was significantly improved after the grafting of P(PEGMA) brushes.     

Controlled grafting from poly(vinylidene fluoride) films by surface‐initiated reversible addition–fragmentation chain transfer polymerization

A reversible addition–fragmentation chain transfer (RAFT) polymerization technique was applied to graft polymerize brushes of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) surfaces. PVDF surfaces were exposed to aqueous LiOH, followed by successive reductions with NaBH₄ and DIBAL‐H to obtain hydroxyl functionality. Azo‐functionalities, as surface initiators for grafting, were immobilized on the PVDF surfaces by esterification of 4,4′‐azobis(4‐cyanopentanoic acid) and the surface hydroxyl groups. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance‐FTIR spectroscopy, and atomic force microscopy. Kinetics studies revealed a linear increase in the graft concentration of PMMA and PPEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The living chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3071–3082, 2006     

Stimuli‐responsive diblock copolymer brushes via combination of “click chemistry” and living radical polymerization

pH‐ and temperature‐responsive poly(N‐isopropylacrylamide‐block?4‐vinylbenzoic acid) (poly(NIPAAm‐b‐VBA)) diblock copolymer brushes on silicon wafers have been successfully prepared by combining click reaction, single‐electron transfer‐living radical polymerization (SET‐LRP), and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. Azide‐terminated poly(NIPAAm) brushes were obtained by SET‐LRP followed by reaction with sodium azide. A click reaction was utilized to exchange the azide end group of a poly(NIPAAm) brushes to form a surface‐immobilized macro‐RAFT agent, which was successfully chain extended via RAFT polymerization to produce poly(NIPAAm‐b‐VBA) brushes. The addition of sacrificial initiator and/or chain‐transfer agent permitted the formation of well‐defined diblock copolymer brushes and free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. Ellipsometry, contact angle measurements, grazing angle‐Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy were used to characterize the immobilization of initiator on the silicon wafer, poly(NIPAAm) brush formation via SET‐LRP, click reaction, and poly(NIPAAm‐b‐VBA) brush formation via RAFT polymerization. The poly(NIPAAm‐b‐VBA) brushes demonstrate stimuli‐responsive behavior with respect to pH and temperature. The swollen brush thickness of poly(NIPAAm‐b‐VBA) brush increases with increasing pH, and decreases with increasing temperature. These results can provide guidance for the design of smart materials based on copolymer brushes. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2677–2685