表面引发接枝聚合法制备接枝微粒PHEMA/SiO2及其8-羟基喹啉功能化转变研究

通过用表面引发接枝聚合和高分子反应制备8-羟基喹啉型复合螯合微粒.首先使用γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行表面改性,制得改性微粒AMPS-SiO2;使改性微粒AMPS-SiO2表面的氨基与溶液中的过硫酸盐构成氧化-还原引发体系,实施了甲基丙烯酸羟乙酯(HEMA)在硅胶微粒表面的高效引发接枝聚合,制得了接枝微粒PHEMA/SiO2.又以5-氯甲基-8-羟基喹啉(CHQ)为试剂,使接枝的PHEMA发生大分子反应,实现了接枝微粒PHEMA/SiO2的8-羟基喹啉功能化转变,制得了复合微粒HQ-PHEMA/SiO2.采用多种手段对两种微粒进行了表征,重点研究了氨基-过硫酸盐表面引发接枝体系的接枝聚合机理,并研究了CHQ与接枝PHEMA的醇羟基之间取代反应的机理,还初步考察了功能微粒HQ-PHEMA/SiO2对重金属离子的螯合吸附性能.研究结果表明,氨基-过硫酸盐表面引发接枝聚合体系具有很高的引发活性,在室温(30℃)即可制得高接枝密度(40 g/100g)的接枝微粒PHEMA/SiO2;CHQ与接枝PHEMA的醇羟基之间的取代反应遵循SN1的反应历程,使用强极性溶剂有利于反应的进行.微粒HQ-PHEMA/SiO2对重金属离子呈现很强的螯合吸附能力,是一种功能复合微粒.     

193 nm激光引发PET表面的化学接枝

将聚对苯二甲酸乙二醇酯[Poly(ethylene terephthalate), PET]材料置于氨气气氛中, 利用激光光子同时激发材料表面及氨气形成自由基, 用激光引发反应并促进氨基在材料表面的接枝. 改性后的测试结果表明, 材料表面粗糙度没有显著变化, 但水接触角的减小表明表面化学结构发生了某种变化. 傅里叶变换红外光谱(FTIR/ATR)图谱在3352和1613 cm-1处出现了新的氨基吸收峰, 证实了表面接枝了氨基. 同时X射线光电子能谱(XPS)也证明了材料表面C—N键的存在, 其C1s结合能为285.5 eV, N1s为398.9 eV. 飞行时间二次离子质谱(Tof-SIMS)也检测到含氨基的分子碎片, 其碎片成像图显示接枝仅发生在激光辐照部位. 实验结果表明, 激光能在生物材料表面进行局部区域的选择性接枝.     

高亲水性聚四氟乙烯微粉的制备及其性能研究

通过预辐射接枝方法在聚四氟乙烯(PTFE)微粉上成功接枝丙烯酸(AAc)和2-丙烯酰胺-2-甲基丙磺酸(AMPS),制备了高亲水性的PTFE微粉.采用红外光谱(FTIR)、X射线光电子能谱(XPS)和接触角(CA)测试表征了改性PTFE微粉的化学结构和亲水性变化;采用扫描电子显微镜(SEM)观察改性PTFE微粉表面形貌;采用电泳法测试了改性PTFE微粉的zeta电位;通过热重分析(TGA)测试了辐射接枝对PTFE微粉热稳定性的影响.结果表明,改性PTFE微粉亲水性和分散稳定性随着接枝率的增加而增强;在单体浓度为20%,AAc与AMPS之比为2且反应温度为70℃时接枝率达到26.6%,此时改性样品PTFE-g-P(AAc-co-AMPS)在水溶液中的分散稳定性效果较好,并能够长期稳定存在.水接触角由改性前的148.8°下降到改性后的30.2°,对应的zeta电位从-4.3 m V降为-83.4 m V.     

有机硅弹性体表面生物相容性的研究进展

生物材料表面的生物相容性一直是生物材料研究领域倍受关注的问题.本文综述了对有机硅弹性体进行改性以提高其表面生物相容性的研究进展,介绍了各种常用的化学改性方法如本体接枝、等离子体处理、光化学诱导接枝、臭氧活化接枝以及硅氢加成反应、原子转移自由基聚合反应在有机硅弹性体表面改性中的应用.对改性后的有机硅弹性体表面抗非特异性蛋白质和血小板的能力等方面进行了评述,并进一步分析了有机硅弹性体表面化学改性的发展趋势和研究重点.     

具有电活性苯胺四聚体接枝聚谷氨酸的合成与表征

以N-羟基琥珀酰亚胺(NHS)活化聚L-谷氨酸的羧基并与苯胺四聚体的氨基缩合,得到了以可生物降解的聚谷氨酸为主链,具有电活性的苯胺四聚体为侧链的新型接枝聚合物.用1H-NMR、质谱分析、光谱分析的方法确定了化合物的结构.侧链羧基的存在使聚合物可以溶解于碱性的缓冲溶液中.对聚合物的电化学性质进行了紫外及循环伏安的表征,研究结果表明,接枝后的聚合物具有与苯胺低聚体相似的可逆的氧化还原过程并可被质子酸掺杂,表现出良好的电化学活性.同时,以定量紫外吸收及元素分析的方法分别测定了聚合物的接枝率.实验中通过控制反应的投料比可以使苯胺四聚体的接枝率达到40%以上,并对聚合物的自掺杂现象进行了讨论.     

辐射接枝聚四氟乙烯的形态结构与结晶性质

<正> 辐射接枝是高聚物改性的重要方法,它特别适用于一般的化学方法难以实现改性的高聚物,如聚四氟乙烯(PTFE)利用辐射接枝改进粘附性取得较好的效益。 不久以前,Yamakowa等人曾对辐射接枝聚乙烯的结构作了讨论。本文用光学显微镜和X-射线等方法对PTFE辐射接枝苯乙烯(St)-丙烯酸(AA)接枝共聚物的超分子     

聚氨酯接枝多壁碳纳米管的制备及表征

采用两步法成功地将聚氨酯分子链以共价键连接到碳纳米管表面. 首先将聚丙烯酰氯通过与强酸氧化后多壁碳纳米管表面产生的羟基及少量羧基之间的化学反应共价接枝到碳纳米管表面; 然后将接枝到碳纳米管表面的聚丙烯酰氯与端羟基聚氨酯发生酯化反应, 实现了聚氨酯对碳纳米管的表面共价接枝. 采用傅里叶变换红外光谱(FTIR)、透射电镜(TEM)、扫描电镜(SEM) 和热重分析(TGA)等对接枝后的产物进行了表征, 结果表明, 聚氨酯已共价接枝到碳纳米管表面, 被接枝的聚合物的含量接近90%.     

CMC-g-DNA接枝共聚物的合成与表征

在磷酸盐缓冲溶液中用1-(3-二甲氨基丙基)-3-乙基碳二亚胺(EDC)与N-羟基琥珀酰亚胺(NHS)活化羧甲基纤维素钠(CMC)侧链上的羧基; 在室温下再将活化的CMC与5'端经氨基修饰的单链脱氧核糖核酸(DNA)齐聚物(ODNs)反应, 获得CMC上接枝ODNs的共聚物(CMC-g-ODNs), 以Lambda DNA为模板, 通过聚合酶链式反应(PCR), 将接枝的ODNs扩增为长度为1300个碱基对的双链DNA, 从而制得CMC侧链上接枝DNA的共聚物CMC-g-DNA. 采用傅里叶红外光谱仪测定CMC与NHS形成的中间体; 用水平式琼脂糖凝胶电泳和垂直板变性聚丙烯酰胺凝胶电泳对CMC-g-DNA接枝共聚物进行表征. 结果表明, 合成了CMC-g-DNA接枝共聚物, 且在酸性条件下CMC的活化效果更好; 同时, 接枝在CMC上的DNA在琼脂糖凝胶电泳中迁移速率加快, 而在聚丙烯酰胺凝胶电泳中迁移速率减慢.     

碳纳米管的羟甲基化及其马来酸酐接枝研究

利用甲醛的亲电性能, 对化学气相沉积法(CVD)制备的多壁碳纳米管(MWCNTs)进行羟甲基化, 并在此基础上酯化接枝马来酸酐, 运用透射电子显微镜(TEM)、红外光谱和Zeta电位仪表征了改性后的MWCNTs的表面结构. TEM结果显示, 酯化后的MWCNTs明显增粗, 说明表面已附有物质. 红外结果表明, 羟甲基后的MWCNTs的表面有了羟基和亚甲基, 而马来酸酐酯化接枝后的MWCNTs有亚甲基和酯基官能团. 光学图像分析表明, 经甲醛处理后的MWCNTs在水溶液中的分散性明显提高, 而马来酸酐酯化接枝后的MWCNTs在二甲苯中的分散性明显增强. Zeta电位的测试结果表明, 甲醛处理过的MWCNTs颗粒在水中, 负电荷增多, 增强了其在悬浮液在溶液中的稳定性.     

硅藻土表面酸性质的研究

研究了几种硅藻土的表面羟基结构、表面酸性质及其孔结构，发现除浙江白土表面具有双生的硅羟基外，其他只有连生与孤立的硅羟基；硅藻土中均存在少量的Ｂ酸和Ｌ酸；硅藻土酸性质及经ＮＨ４Ｃｌ或ＨＣｌ活化后的酸性质变化与硅藻土孔结构、表面结构有关。焙烧温度升高，硅藻土酸强度增加，酸量减少。     

Surface modification of magnetic nanoparticles capped by oleic acids: characterization and colloidal stability in polar solvents

The lyophobic surface of monodisperse magnetic nanoparticles capped by oleic acid was made to be more lyophilic by ozonolysis to increase the stability of the suspension in polar solvents like ethanol. The ozone oxidatively cleaved the double bond of oleic acid to form carbonyl and carboxyl groups on the surface of the nanoparticles. Additionally, interfacial ligand exchange of the capping molecules was applied to make the hydrophobic particle surface more hydrophilic. The magnetic particles showed enhanced miscibility and short-term stability in water after interfacial ligand exchange. The structure changes of the capping molecules on the nanoparticle surfaces were investigated using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From these spectroscopy studies, the cleavage of the oleic acid and the formations of the carboxyl and carbonyl groups on the particle surface were confirmed. The shape and the magnetic properties of the nanoparticles were maintained after the surface modification. Ozonolysis is an effective method in modifying the lyophobic surface of the magnetic nanoparticles.     

Surface grafting of polymers onto inorganic ultrafine particles: Reaction of functional polymers with acid anhydride groups introduced onto inorganic ultrafine particles

The surface grafting onto inorganic ultrafine particles, such as silica, titanium oxide, and ferrite, by the reaction of acid anhydride groups on the surfaces with functional polymers having hydroxyl and amino groups was examined. The introduction of acid anhydride groups onto inorganic ultrafine particle was achieved by the reaction of hydroxyl groups on these surfaces with 4-trimethoxysilyltetrahydrophthalic anhydride in toluene. The amount of acid anhydride groups introduced onto the surface of ultrafine silica, titanium oxide, and ferrite was determined to be 0.96, 0.47, and 0.31 mmol/g, respectively, by elemental analysis. Functional polymers having terminal hydroxyl or amino groups, such as diol-type poly(propylene glycol) (PPG), and diamine-type polydimethylsiloxane (SDA), reacted with acid anhydride groups on these ultrafine particles to give polymer-grafted ultrafine particles: PPG and SDA were considered to be grafted onto these surfaces with ester and amide bond, respectively. The percentage of grafting increased with increasing acid anhydride group content of the surface: the percentage of grafting of SDA (M_n = 3.9 × 10³) onto silica, titanium oxide, and ferrite reaching 64.7, 33.7, and 24.1%, respectively. These polymer-grafted ultrafine particles gave a stable colloidal dispersion in organic solvents.     

Phosphonic acid monolayers for binding of bioactive molecules to titanium surfaces

Two different phosphonic acid monolayer films for immobilization of bioactive molecules such as the protein BMP-2 on titanium surfaces have been prepared. Monolayers of (11-hydroxyundecyl)phosphonic acid and (12-carboxydodecyl)phosphonic acid molecules were produced by a simple dipping process (the T-BAG method). The terminal functional groups on these monolayers were activated (carbonyldiimidazole for hydroxyl groups and N-hydroxysuccinimide for carboxyl groups) to bind amine-containing molecules. The reactivity of the surfaces was investigated using trifluoroethylamine hydrochloride and BMP-2. Each step of the surface modification procedure was characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry.     

多壁碳纳米管-炭复合泡沫材料的制备和吸附性能

通过在聚氨酯泡沫模板中沉积多壁碳纳米管，用炭的预制体酚醛树酯将碳纳米管粘接固定在一起，经过高温碳化过程制备了碳纳米管-炭复合泡沫材料。红外光谱结果表明利用浓硫酸和浓硝酸的混合溶液处理可以使复合泡沫表面活化形成羧基和羟基，从而使复合泡沫具备较强的分子吸附能力。扫描电镜和氮吸附实验表明这种复合泡沫同时具备大孔和介孔，大孔能够满足流体自由流动的通畅性，介孔可以满足中分子的吸附需要。对标定物维生素B12的吸附实验证明这种复合泡沫对中分子量的生化分子具有有效的吸附能力。这种宏观尺寸的泡沫材料与传统的颗粒状活性炭相比具有简化工艺，提高吸附效率的应用潜力。     

Protein immobilization on the surface of poly-L-lactic acid films for improvement of cellular interactions

To covalently immobilize gelatin or collagen type I on poly-L-lactic acid (PLLA) film surfaces poly(hydroxyethyl methacrylate) (PHEMA) or poly(methacrylic acid) (PMAA) was grafted via photooxidization and subsequent UV-induced polymerization [Makromol. Chem. 186 (1985) 1533.1]. For films grafted with PHEMA, methyl sulfonyl chloride was used to activate the hydroxyl groups and for films grafted with PMAA 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide was used to activate the carboxyl groups. Gelatin and collagen were finally reacted with the activated hydroxyl or carboxyl groups to obtain covalently immobilized protein layers. Grafting of PHEMA, PMAA and protein on the surfaces was confirmed using ATR-IR and XPS. Surface wettability of the modified films was improved. The protein immobilized PLLA may be widely used as a biocompatible material.     

Functionalization of Silicon Nanoparticles via Silanization: Alkyl, Halide and Ester

The feasibility of using silanization as a general tool to functionalize the surface of silicon nanoparticles (NPs) has been investigated in detail. Silicon NPs were prepared from reduction of silicon tetrachloride with sodium naphthalide. The terminal chloride on the surface of as-synthesized particles was substituted by methanol and water, in sequence. The particles were then silanized by octyltrichlorosilane, 11-bromoundecyltrichlorosilane, or 2-(carbomethoxy)ethyltrichlorosilane. These treatments yielded alkyl-, bromo-, or ester-termini on NP surfaces, respectively. The NPs were characterized by TEM, NMR, FTIR, UV–Vis, and PL spectroscopy. Changes of termination groups brought various functionalities to the NPs, without loss of the photophysics of the original NPs.     

Surface structures of fluoropolymer,polyolefin and polyester films after modification by graft polymerization

Pristine and argon plasma pretreated polytetrafluoroethylene (PTFE), polystyrene (PS), high-density polyethylene (HDPE) and poly(ethylene terrephthalate) (PET) films have been subjected to near-UV light-induced graft polymerization with water-soluble acrylamide (AAm), the sodium salt of styrene sulfonic acid (NaSS), acrylic acid (AAc) and N,N-dimethylaminoethylmethylacrylate (DMAEMA) monomers. The structure and composition at the substrate surface with grafted polymer were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). In most cases, the density of surface grafting is enhanced by plasma pretreatment. For each polymer substrate with a substantial amount of grafting, the hydrophilic graft penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains. This stratified microstructure is consistent with the static secondary ion mass spectroscopy (SIMS) and Ar⁺ beam depth profiling results. The two latter techniques also suggest that when the grafted polymer has a bulky substituent, there is less efficient penetration of the grafted polymer below the surface.     

Rational Design of Carboxyl Groups Perpendicularly Attached to a Graphene Sheet: A Platform for Enhanced Biosensing Applications

Graphene oxide (GO)‐based materials offer great potential for biofunctionalization with applications ranging from biosensing to drug delivery. Such biofunctionalization utilizes specific functional groups, typically a carboxyl moiety, as anchoring points for biomolecule. However, due to the fact that the exact chemical structure of GO is still largely unknown and poorly defined (it was postulated to consist of various oxygen‐containing groups, such as epoxy, hydroxyl, carboxyl, carbonyl, and peroxy in varying ratios), it is challenging to fabricate highly biofunctionalized GO surfaces. The predominant anchoring sites (i.e., carboxyl groups) are mainly present as terminal groups on the edges of GO sheets and thus account for only a fraction of the oxygen‐containing groups on GO. Herein, we suggest a direct solution to the long‐standing problem of limited abundance of carboxyl groups on GO; GO was first reduced to graphene and consequently modified with only carboxyl groups grafted perpendicularly to its surface by a rational synthesis using free‐radical addition of isobutyronitrile with subsequent hydrolysis. Such grafted graphene oxide can contain a high amount of carboxyl groups for consequent biofunctionalization, at which the extent of grafting is limited only by the number of carbon atoms in the graphene plane; in contrast, the abundance of carboxyl groups on “classical” GO is limited by the amount of terminal carbon atoms. Such a graphene platform embedded with perpendicularly grafted carboxyl groups was characterized in detail by X‐ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy, and its application was exemplified with single‐nucleotide polymorphism detection. It was found that the removal of oxygen functionalities after the chemical reduction enhanced the electron‐transfer rate of the graphene. More importantly, the introduction of carboxyl groups promoted a more efficient immobilization of DNA probes on the electrode surface and improved the performance of graphene as a biosensor in comparison to GO. The proposed material can be used as a universal platform for biomolecule immobilization to facilitate rapid and sensitive detection of DNA or proteins for point‐of‐care investigations. Such reactive carboxyl groups grafted perpendicularly on GO holds promise for a highly efficient tailored biofunctionalization for applications in biosensing or drug delivery.     

Surface ATRP of hydrophilic monomers from ultrafine aqueous silica sols using anionic polyelectrolytic macroinitiators

A convenient two-step route was developed to prepare new anionic ATRP macroinitiators from near-monodisperse poly(2-hydroxyethyl methacrylate) precursors by partial esterification with 2-bromoisobutyryl bromide, followed by esterification of the remaining hydroxyl groups using excess 2-sulfobenzoic acid cyclic anhydride. These new macroinitiators can be electrostatically adsorbed onto ultrafine cationic Ludox CL silica sols; subsequent surface polymerization of various hydrophilic monomers in aqueous solution at room temperature afforded a range of polymer-grafted ultrafine silica sols. The resulting sterically stabilized particles were characterized by dynamic light scattering, transmission electron microscopy, aqueous electrophoresis, FTIR spectroscopy, and elemental microanalyses.     

Grafting of amino functional monomer onto initiator-modified polystyrene particles

Polystyrene nanoparticles with grafted chains of an amino functionalized polymer were prepared by a two-step polymerization process. In the first step, the polystyrene seed particles were synthesized by the conventional batch emulsion polymerization using terpolymer HAS (hydroperoxide monomer, acrylic acid, and styrene) as a surface-active initiator. The surface of the obtained particles contains carboxyl groups, which are responsible for the latex stability, and residual undecomposed hydroperoxide groups. Therefore, in the second step, an amino functional monomer was grafted onto the hydroperoxide modified polystyrene particles by a "grafting from" approach. X-ray photoelectron spectroscopy, NMR, and scanning electron microscopy were used to examine the surface of the amino functionalized particles. The amount of incorporated amino groups onto the particles was determined by fluorescenometric titration. In general, the number of amino groups on the particle surface increased with the increase of the functional monomer content in the reaction mixture. The incorporation of the functional monomer was also confirmed by electrophoretic measurements. Final particles possess amphoteric character due to the presence of amino and carboxyl groups on the surface. Adsorption of human immunoglobulins G onto the amino functionalized particles was studied as a function of pH and ionic strength. The covalent binding of human IgG was performed using the glutaraldehyde preactivation method. The immunoreactivity of the latex-IgG complex was examined by the latex agglutination test.