新型室温酯化法接枝聚合物改性SiO_2纳米微粒

提出了一种在室温、大气环境等温和条件下通过酯化反应将端羧基聚合物链接枝到纳米SiO2微球表面从而制备有机/无机复合纳米微粒的新方法.该方法通过以下两个步骤得以实现,即第一,用3-环氧丙基三甲氧基硅烷对纳米SiO2微球表面进行改性处理,接着将引入到纳米SiO2表面的环氧基团转化为烷羟基基团;第二,通过引入到纳米SiO2微球表面的烷羟基与聚合物中的端羧基在室温下发生酯化反应,从而将聚合物接枝到纳米SiO2表面制得复合微球.利用XPS、FTIR、TEM和TGA等测试手段对纳米SiO2的改性过程以及聚合物接枝后得到的复合微球进行了表征.研究结果表明,该室温酯化接枝方法具有较高的接枝率,接枝到无机纳米微粒表面的聚合物占复合微球质量的55wt%～70wt%;接枝聚合物后,纳米SiO2微球的粒径从40nm增加到64～75nm,从而得到了以SiO2为核、以聚合物为壳的有机-无机复合微球.     

环氧天然橡胶接枝高分散白炭黑增强天然橡胶复合材料的制备及表征

基于白炭黑表面硅羟基与环氧基团的可反应性,利用Haake流变仪的高温高剪切作用,在170℃下,实现了环氧天然橡胶(ENR)对白炭黑的固态原位接枝,制备出一种高分散疏水型白炭黑.探讨了白炭黑和ENR的反应配比对增强性能的影响,确定合适的反应比例为3∶1.FTIR、TGA和TEM的分析结果证实了ENR被接枝到白炭黑表面上.对比研究了接枝前、后白炭黑对增强天然橡胶(NR)复合材料性能的影响,测试结果表明接枝白炭黑在天然橡胶中具有良好的分散性并能明显改善对天然橡胶的增强效果;接枝于白炭黑表面上的环氧天然橡胶分子玻璃化转变向高温偏移,使该复合材料在常温下具备优异力学性能的同时也体现出了高动态滞后的特点.     

Functionalization of nanodiamond with epoxy monomer

A novel nanodiamond-epoxy derivative(ND-EP) was synthesized by grafting epoxy monomers onto the surface of nanodiamond(ND),and characterized by FTIR and TGA.The ratio of grafted epoxy groups was determined to be 32.5 wt% by TGA.The developed methodology provides an efficient method for the functionalization of nanodiamond material,which enables a variety of advanced engineering and biomedical applications of ND.     

Facile Fabrication of Polymeric Ionic Liquid Grafted Porous Polymer Monolith for Mixed‐Mode High Performance Liquid Chromatography

A novel polymeric ionic liquid grafted porous polymer monolith has been facilely fabricated for mixed‐mode chromatography. The column is prepared from poly (glycidyl methacrylate‐co‐ethylene dimethacrylate) monolith through hydrolyzation of the epoxy moieties into hydroxyl groups, followed by "grafting from" polymerization of ionic liquid of 1‐vinyl‐3‐butylimidazolium chloride. Successful modification is characterized by scanning electron microscope, infrared spectroscopy, elemental analysis and mercury intrusion porosimetry. The HPLC performance of developed column is evaluated by separating acidic vitamin B analytes, neutral steroids and basic aromatic amines in mixed‐mode chromatography on a single column, respectively. The ionic liquid affords the monolith with both enhanced separation ability and improved column efficiency.     

Grafting of hyperbranched poly(amidoamine) onto waste tire rubber powder and its potential application as the curing agent for epoxy resin

To realize the high‐valued application of waste tire rubber (WTR), hyperbranched poly(amidoamine) (PAMAM) were synthesized from the surface of WTR powders to endow its chemical reactivity. The hyperbranched PAMAM‐grafted WTR powders containing a large amount of amine groups on their surface were obtained through “divergent procedure.” First, methyl methacrylate‐grafted WTR powders (MMA‐g‐WTR) were prepared by ozone‐induced grafting polymerization. Afterwards, Michael reaction and subsequent amidation reactions were carried out repetitively to obtain hyperbranched PAMAM chains grafted from the surface of the MMA‐g‐WTR powders. The resulting hyperbranched PAMAM‐grafted WTR powders exhibit good dispersibility in water. Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and thermogravimetric analysis demonstrate the successful grafting of hyperbranched PAMAM on WTR surface. The hyperbranched PAMAM‐grafted WTR powder could be utilize as curing agent and potential toughener for epoxy resin due to abundant amine groups and elastomeric feature of WTR. Differential scanning calorimetry shows that the hyperbranched PAMAM‐grafted WTR powders can be used as effective curing agent for epoxy resin. Copyright © 2011 John Wiley & Sons, Ltd.     

Surface modification of polymeric microspheres using glycopolymers for biorecognition

We report the synthesis and characterization of sugar-containing microspheres consisting of poly(divinylbenzene) (PDVB) cores onto which chains of galactose- or mannose-bearing polymers have been grafted. PDVB particles prepared by distillation polymerization with a diameter of 2.4 μm containing residual surface vinyl groups were used as starting material. “Grafting from”, “grafting through” and “grafting to” techniques were performed and special interest was laid towards the resulting grafting densities. The surface modification via “grafting from” was conducted by reversible addition fragmentation chain transfer (RAFT) polymerization directly from the surface, whereas thiol-ene chemistry was used to affix glycopolymer chains onto the particle surface. The resulting sugar-covered microspheres were analyzed towards their protein recognition activity with a series of lectins.     

Electrochemical properties of polyethylene membrane modified with carboxylic acid group

Two cation-exchange membranes modified with the carboxylic acid group for battery separator were prepared by radiation-induced grafting of acrylic acid (AA) and methacrylic acid (MA) onto a polyethylene (PE) film. The surface area, thickness, volume, water uptake, ion-exchange capacity, specific electric resistance, and electrolyte flux were evaluated after PE film was grafted with AA and MA. It was found that KOH diffusion flux of AA-grafted PE membrane and MA-grafted PE membrane increased with an increase in the degree of grafting. AA-grafted PE membrane had a higher diffusion flux than MA-grafted PE membrane. Electrical resistance of two cation-exchange membranes modified with AA and MA decreased rapidly with an increase in the degree of grafting.     

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.     

Monolithic column with double mixed-modes of hydrophilic interaction/cation-exchange and reverse-phase/cation-exchange stationary phase for pressurized capillary electrochromatography

A monolithic capillary column with double mixed-modes of hydrophilic interaction/cation-exchange and RP/cation-exchange stationary phase was prepared by in situ thermal polymerization and then hydrolyzed with hydrochloric acid. The polymerization solution containing glycidyl methacrylate (GMA), 3-sulfopropyl methacrylate potassium salt (SPMA), and ethylene dimethacrylate (EDMA) in a binary porogenic solvent consisting of dimethylformamide (DMF) and 1,4-butanediol was polymerized in a fused-silica capillary pretreated with 3-(trimetoxysilyl) propyl methacrylate. The epoxy groups on the surface were hydrolyzed to diol groups with hydrochloric acid to enhance the polarity of the stationary phase. By simply altering the ACN content in the mobile phase, two mixed-mode mechanisms could be achieved on the same monolithic column in different mobile phase condition. Hydrophilic interaction (or hydrophilic interaction/cation-exchange) was observed at high ACN content, as well as RP (or RP/cation-exchange) was observed at low ACN content. The monolithic column provided good selectivity and high efficiency for separation of neutral polar analytes and basic compounds. Phenols, anilines, alkaloids, nucleic acid bases, and narcotic pharmaceuticals have been successfully separated. Effects of salt concentration and ACN content on the separation have also been investigated. High column efficiencies of up to 352 000 plates/meter were obtained by the separation of narcotic pharmaceuticals.     

Hydrobromination of residual vinyl groups on divinylbenzene polymer particles followed by atom transfer radical surface graft polymerization

Rigid and monodisperse spherical polymer particles with 2.36 ± 0.18 μm diameter containing residual surface vinyl groups were prepared by photoinitiated precipitation polymerization of divinylbenzene. Anti‐Markovnikov addition of HBr to the surface vinyl groups yielded a 2‐bromoethyl functionality that was used as macroinitiator for atom transfer radical polymerization (ATRP), providing the possibility for further functionalization by controlled “grafting from” processes. This was demonstrated by grafting of glycidyl methacrylate brushes from the particle surface, using an ATRP system based on CuBr and pentamethyl diethylenetriamine. Existence of a methacrylic overlayer was verified by FTIR and XPS measurements, and the grafted particles were easily dispersed in water, confirming conversion of the particle surface from hydrophobic to hydrophilic. Hydrobromination of residual vinyl groups yields a macroinitiator that can be used for grafting of glycidyl methacrylate by ATRP. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1259–1265, 2009     

Characterisation of grafted weak anion-exchange methacrylate monoliths

A weak ion-exchange grafted methacrylate monolith was prepared by grafting a methacrylate monolith with glycidyl methacrylate and subsequently modifying the epoxy groups with diethylamine. The thickness of the grafted layer was determined by measuring permeability and found to be approximately 90nm. The effects of different buffer solutions on the pressure drop were examined and indicated the influence of pH on the permeability of the grafted monolith. Protein separation and binding capacity (BC) were found to be flow-unaffected up to a linear velocity of 280cm/h. A comparison of the BC for the non-grafted and grafted monolith was performed using beta-lactoglobulin, bovine serum albumin (BSA), thyroglobulin, and plasmid DNA (pDNA). It was found that the grafted monolith exhibited 2- to 3.5-fold higher capacities (as compared to non-grafted monoliths) in all cases reaching values of 105, 80, 71, and 17mg/ml, respectively. It was determined that the maximum pDNA capacity was reached using 0.1M NaCl in the loading buffer. Recovery was comparable and no degradation of the supercoiled pDNA form was detected. Protein z-factors were equal for the non-grafted and grafted monolith indicating that the same number of binding sites are available although elution from the grafted monolith occurred at higher ionic strengths. The grafted monolith exhibited lower efficiency than the non-grafted ones. However, the baseline separation of pDNA from RNA and other impurities was achieved from a real sample.     

High strength toughened epoxy nanocomposite based on poly(ether sulfone)‐grafted multi‐walled carbon nanotube

Hydroxyl terminated poly(ether sulfone) (PES) has been grafted on multi‐walled carbon nanotube (MWCNT). The grafting reaction was confirmed by different characterization techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The extent of the grafting was found to be around 58 wt%. Hybrid nanocomposite of epoxy with the modified MWCNT was also prepared. Effect of grafting on the mechanical, thermal, and viscoelastic properties was studied. Dynamic mechanical studies show an increase in the storage modulus for the nanocomposite prepared using PES‐grafted MWCNT compared with neat epoxy system. PES‐grafted MWCNT–epoxy nanocomposite induces a significant increase in both tensile strength (26%) and fracture toughness (125%) of the epoxy matrix. Field emission scanning electron micrographs of fractured surfaces were examined to understand the toughening mechanism. Copyright © 2015 John Wiley & Sons, Ltd.     

构建芳叔胺-BPO氧化还原引发体系实现苯乙烯在硅胶微粒表面的高效接枝聚合

首先使用偶联剂γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行了表面改性,制得表面带有伯胺基的改性微粒SiO2-AMPS,接着使4-(二乙氨基)水杨醛(DEAS)与微球SiO2-AMPS发生席夫碱反应,制得表面含有芳叔胺基的改性微粒SiO2-DEAS.使改性微粒SiO2-DEAS表面的芳叔胺基团与溶液中的BPO构成氧化-还原引发体系,实现了油溶性单体苯乙烯(St)在硅胶微粒表面的引发接枝聚合,制得了高接枝度(27 g/100g)的接枝微粒SiO2-DEAS-g-PSt.采用红外光谱(FTIR)、扫描电镜(SEM)及热重分析(TGA)等方法对接枝微粒SiO2-DEAS-g-PSt进行了表征.在此基础上,重点研究了主要因素对芳叔胺-BPO体系引发St接枝聚合的影响.研究结果表明,与在固体微粒表面引入可聚合双键的"穿过接枝"(grafting through)法相比,芳叔胺-BPO体系引发的接枝聚合,由于活性位点位于载体表面,故具有高的接枝度,是油溶性单体的一种高效率的表面引发接枝法.为制得高接枝度的接枝微粒SiO2-DEAS-g-PSt,适宜的温度为50℃,适宜的BPO用量为单体的3 wt%左右,适宜的单体浓度为10 wt%.     

Heterogeneous grafting on polymers containing chlorine: Grafting of amide groups in water suspension and the reactivity of the new polymer towards epoxy resins

Heterogeneous grafting on polyvinylchloride suspended in water was carried out using N-butyl-3-mercaptopropionamide as nucleophile. Over 50% graft was obtained by using a small amount of solvent as a swelling agent and tricapryl methyl ammonium chloride as a phase transfer catalyst. Elemental analysis of the grafted polymer shows that the chlorine displaced from the polymers is replaced by the thio-amide group. The above conclusion is supported by NMR and IR analysis. The kinetics of the chlorine displacement from PVC by the thio amide group obeys the Shell progressive mechanism. The rate at which an individual spherical particle reacts depends on the diffusion through the reacted layer. The grafted polymer is soluble in tetrahydrofuran or nitrobenzene. The films obtained from the grafted material are brittle due to excessive internal hydrogen bonding. The electrostatic charge which is a characteristic surface phenomena in PVC is diminished in the grafted polymer which may be due to the existence of the amide group near the surface. The amide groups attached to the side chains on the polymer may participate in various reactions, e.g., with epoxy resins. IR analysis of the cured film indicates the disappearance of the oxiran band at 913 cm^?1 and an increase in the hydroxyl band around 3300 cm^?1. Thus, grafting of amide groups on PVC enables us to further modify PVC by epoxy resins.     

Surface modification of polymers. II. Grafting with glycidyl acrylates and the reactions of the grafted surfaces with amines

The surface of low density polyethylene has been grafted with glycidyl acrylate and glycidyl methacrylate by photoinitiation. ESCA measurements on the grafted surface showed a 72% coverage for glycidyl acrylate and 52% for glycidyl methacrylate after 10 min of grafting with UV irradiation. ATR–IR showed a 10 times more extensive grafting for glycidyl acrylate than for glycidyl methacrylate after 10 min of grafting, indicating reaction to deeper layers. Acetone and ethanol were used as solvents: acetone yielded slightly more grafting at the surface. The grafted surfaces were reacted with 2M solutions of aniline and propylamine in ethanol. After 4 h reaction at 60°C, with aniline 52% of the epoxy groups while for propylamine 96% of the groups were consumed, as measured with ATR–IR.     

Enhanced binding by dextran‐grafting to Protein A affinity chromatographic media

Dextran‐grafted Protein A affinity chromatographic medium was prepared by grafting dextran to agarose‐based matrix, followed by epoxy‐activation and Protein A coupling site‐directed to sulfhydryl groups of cysteine molecules. An enhancement of both the binding performance and the stability was achieved for this dextran‐grafted Protein A chromatographic medium. Its dynamic binding capacity was 61 mg immunoglobulin G/mL suction‐dried gel, increased by 24% compared with that of the non‐grafted medium. The binding capacity of dextran‐grafted medium decreased about 7% after 40 cleaning‐in‐place cycles, much lower than that of the non‐grafted medium as decreased about 15%. Confocal laser scanning microscopy results showed that immunoglobulin G was bound to both the outside and the inside of dextran‐grafted medium faster than that of non‐grafted one. Atomic force microscopy showed that this dextran‐grafted Protein A medium had much rougher surface with a vertical coordinate range of ±80 nm, while that of non‐grafted one was ±10 nm. Grafted dextran provided a more stereo surface morphology and immunoglobulin G molecules were more easily to be bound. This high‐performance dextran‐grafted Protein A affinity chromatographic medium has promising applications in large‐scale antibody purification.     

Surface grafting onto SiC nanoparticles with glycidyl methacrylate in emulsion

To improve the tribological performance of nano‐SiC particles filled epoxy composites, surface modification of the fillers is necessary. By means of soapless emulsion polymerization method, graft polymerization of glycidyl methacrylate (GMA) onto the surface of alkyl nano‐SiC was carried out, resulting in composite particles with SiC core and polymeric shell in which polyglycidyl methacrylate (PGMA) is chemically attached to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. By analyzing the reaction mechanism, the emulsion polymerization loci were found to be situated at the SiC surface. Also, the factors affecting the grafting yielding of PGMA on the particles were investigated, including monomer concentration, initiator consumption, reaction temperature, reaction time, etc. Accordingly, an optimum grafting reaction condition was determined. It was shown that the grafted nanoparticles exhibit greatly improved dispersibility in good solvent for the grafting polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3842–3852, 2004     

氧化铝-g-聚丙烯酰胺复合磨粒的制备及表征

为提高α-Al₂O₃磨粒在水基介质中的分散稳定性，采用接枝聚合方法制备了Al₂O₃-g-聚丙烯酰胺复合粒子。采用FTIR、XPS、TOF-SIMS、激光粒度仪、SEM、沉降试验等对氧化铝复合粒子结构及分散性能等进行了表征。结果表明，聚丙烯酰胺以化学键形式接枝到Al₂O₃粒子表面，形成聚丙烯酰胺为壳，Al₂O₃为核的复合磨粒;接枝改性后的Al₂O₃粒子分散性明显提高，并且其分散性与Al₂O₃表面接枝量密切相关。     

Gas-phase and liquid-phase pre-irradiation grafting of AAc onto LDPE and HDPE films for pervaporation membranes

A study has been made on gas-phase and liquid-phase pre-irradiation grafting of acrylic acid onto LDPE and HDPE films for pervaporation membranes of ethanol-water mixtures. It was found that the degree of grafting, percent volume change of grafted membranes and length of grafting chains depend on the methods of grafting, crystal state of substrate films and diffusion rate of the monomer in the films. The pervaporation characteristics of grafted membranes is influenced directly by the surface hydrophilicity of grafted membranes, temperature of the feed, degree of grafting, crosslinking of grafted chains and alkaline metal ions in the functional groups. The potassium ion exchange membrane of HDPE synthesized by gas-phase grafting has better pervaporation efficiency. At 80 wt% ethanol in the feed, 25°C feed temperature and 70% degree of grafting a grafted membrane has a 0.65 kg/m²h flux and a separation factor of 20.     

Hydrophilic Modification of Microporous Polysulfone Membrane via Surface‐Initiated Atom Transfer Radical Polymerization and Hydrolysis of Poly(glycidylmethacrylate)

Poly(glycidylmethacrylate) (PGMA) brushes were grafted from chloromethylated polysulfone (CMPSF) membrane surface by surface‐initiated atom transfer radical polymerization (SI‐ATRP), and the grafting was followed by hydrolysis of epoxy groups in the grafting chains to improve the membrane's hydrophilic property. Fourier transform infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) measurements confirmed the successful grafting and hydrolysis of PGMA. The grafting degree of the monomer, measured by periodic acid titration and gravimetric analysis, increased linearly with the polymerization time, while the static water contact angle of the membrane grafted with PGMA or hydrolyzed PGMA linearly decreased. In comparison with the PGMA‐grafted membranes, the hydrolyzed PGMA‐grafted membranes possess stronger hydrophilicity as indicated by their contact angle and hydration capacity, and as a result they have an improved antifouling property. Therefore, the control of the hydrophilicity of PSF membrane could be realized through adjusting the polymerization time and transforming the functional groups in the grafting chain.