原子转移自由基聚合与“Click”反应相结合制备Fe3O4@SiO2-g-PDMAEMA及其性质研究

结合原子转移自由基聚合（ATRP）与点击反应（＂Click＂reaction）,在SiO2包裹的Fe3O4磁性纳米粒子（Fe3O4@SiO2）表面接枝聚[甲基丙烯酸-2-（N,N-二甲氨基）乙酯]（PDMAEMA）,得到了表面接枝PDMAEMA的磁性纳米粒子（Fe3O4@SiO2-g-PDMAEMA）.通过1H NMR...     

亚氨二乙酸型复合材料IDAA-PGMA/SiO2对重金属及稀土离子的吸附行为与吸附热力学

将甲基丙烯酸缩水甘油酯(GMA)接枝于硅胶微粒表面,制得了接枝微粒PGMA/SiO₂; 使亚氨二乙酸(IDAA)与接枝PGMA的环氧基团发生开环反应, 从而将亚氨二乙酸基团引入接枝微粒表面, 制得了复合螯合微粒材料IDAA-PGMA/SiO₂. 本文研究了IDAA-PGMA/SiO₂对重金属及稀土离子的螯合吸附行为, 深入地研究了吸附机理与吸附热力学. 研究结果表明: 凭借亚氨二乙酸基团与重金属离子之间的静电作用与配位螯合作用的协同, 复合微粒材料IDAA-PGMA/SiO₂对重金属离子可产生强的螯合吸附作用, 尤其对Pb²⁺离子表现出很强的螯合吸附能力, 常温下吸附容量可达0.235 g·g^-1; IDAA-PGMA/SiO₂对重金属离子的吸附过程为一放热过程, 且为焓驱动的过程, 升高温度, 吸附容量降低; 对稀土离子的吸附过程则为熵驱动的过程; 在可抑制金属离子水解的pH范围内, 介质的pH值越高, IDAA-PGMA/SiO₂的螯合吸附能力越强; IDAA-PGMA/SiO₂对重金属离子的吸附容量远高于对稀土离子的吸附容量.     

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-free hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate(MMA),butyl acrylate(BA), methacrylic acid(MAA),styrene(St)and ethylene glycol dimethacrylate(EGDMA)as monomers,and the influences of MMA content used in the core preparation on polymerization,particle size and morphology were investigated by transmission electron microscopy,dynamic light scattering and conductometric titration.The results showed that the seeded emulsion polymerization could be carried out smoothly using "starved monomer feeding process" when MAA content in the core preparation was equal to or less than 24 wt%,and the encapsulating efficiency of the hydrophilic P(MMA-BA-MAAEGDMA) core with the hydrophobic PSt shell decreased with the increase in MAA content.When an interlayer of P(MMAMAA -St)with moderate polarity was inserted between the P(MMA-BA-MAA-EGDMA)core and the PSt shell,well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt%MAA content in the core preparation were obtained.     

Constructing chiral caves and efficiently separating enantiomers of glutamic acid with novel surface-imprinting technique

Dimethylaminoethyl methacrylate (DMAEMA) was first graft-polymerized onto the surfaces of micron-sized silica gel particles in the manner of "grafting from" in a solution polymerization system, obtaining the grafted particles PDMAEMA/SiO(2). Then, the molecular imprinting towards the grafted PDMAEMA was conducted with one enantiomer of glutamic acid (Glu), L-Glu, as template molecule and with 2,2'-dichlorodiethylether (DCEE) as crosslinking agent by adopting the novel surface-molecular imprinting technique established by our research group, and the single enantiomer (L-Glu) molecule-imprinted material MIP-PDMAEMA/SiO(2) was obtained. With another enantiomer of glutamic acid, D-Glu, as the contrast compound, the recognition property of MIP-PDMAEMA/SiO(2) for L-Glu was investigated in depth with both static and dynamic methods, and its ability to separate L-Glu and D-Glu in the racemic solution was examined. The experiment results show that the surface-imprinted material MIP-PDMAEMA/SiO(2) has fine recognition selectivity and binding affinity for l-Glu, whereas its ability to combine D-Glu is poor. The selectivity coefficient of MIP-PDMAEMA/SiO(2) for L-Glu with respect to D-Glu is equal to 3.30, displaying an excellent chiral separation result. It is obvious that in this study, the substance separation at the molecular configuration level has been realized successfully.     

氯甲基聚苯乙烯/硅胶复合微粒的制备与表征

采用"接出(grafting from)"方式,在溶液聚合体系中将苯乙烯(St)接枝聚合在微米级硅胶表面,制备了接枝微粒PSt/SiO2;使用新型氯甲基化试剂1,4-二氯甲氧基丁烷,对接枝在硅胶表面的聚苯乙烯进行了氯甲基化(CM)反应,制得了氯甲基聚苯乙烯/硅胶(CMPS/SiO2)复合微粒.采用热重分析(TG)测定了PSt/SiO2的接枝度,并使用扫描电子显微镜(SEM)观察了其形貌;通过红外光谱法(FTIR)与佛尔哈德分析法表征了CMPS/SiO2的化学结构与组成.重点考察了各种因素对PSt/SiO2氯甲基化反应过程的影响规律.研究结果表明,CMPS/SiO2的制备不仅具有绿色环保的特点,而且反应容易控制.反应时间、溶剂种类与用量、催化剂种类与用量及氯甲基化试剂的用量等因素均会对该复合微粒的制备产生影响,如影响CMPS/SiO2的氯甲基化程度;抑制或促进已接枝的PSt大分子链之间通过Friedel-Crafts反应发生交联.若选用SnCl4为催化剂,以CH2Cl2为溶剂,在室温下反应10 h左右,可制得氯含量接近16 wt%(以接枝的PSt为基准计算)的CMPS/SiO2.     

Double-responsive polymer brushes on the surface of colloid particles

Well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes were synthesized on the surface of polystyrene latex particles by atom transfer radical polymerization (ATRP). It was found that the surface-initiated polymerization of DMAEMA catalyzed by CuCl/CuCl(2)/bpy was under good control in the solvent of acetone/water at ambient temperature (35 degrees C). High-density PDMAEMA brushes with low polydispersity (PDI 1.21) were obtained. TEM results demonstrate that the PDMAEMA-grafted particles have core-shell structure. Dynamic light scattering studies indicate that the particles with PDMAEMA brushes are both pH and temperature responsive.     

Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Monodisperse polar gradient particles were synthesized via a three‐step emulsion polymerization using poly(butyl acrylate‐methyl methacrylate‐methacrylic acid‐ethylene glycol dimethacrylate) (P(BA‐MMA‐MAA‐EGDMA)) as core, poly(methyl methacrylate‐methacrylic acid‐styrene) (P(St‐MMA‐MAA)) as interlayer and polystyrene (PSt) as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two‐layer core/interlayer and three‐layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl‐containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage.     

刷状结构的阳离子性接枝微粒QPDMAEMA/SiO_2对牛血清白蛋白的吸附特性

以微米级硅胶微粒为基质,通过接枝聚合和大分子反应,制备了具有刷状结构的阳离子性接枝微粒,深入研究了其对牛血清白蛋白(BSA)的强吸附能力、吸附机理和吸附热力学.首先使含叔胺基团的单体甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面发生接枝聚合,制得接枝微粒PDMAEMA/SiO2,然后以氯乙胺为试剂,使接枝大分子PDMAEMA链中的叔胺基团发生季铵化反应,获得了具有刷状结构的阳离子聚电解质的功能接枝微粒QPDMAEMA/SiO2.测定了微粒QPDMAEMA/SiO2的zeta电位,实施了对BSA的等温吸附实验,考察了介质pH值、离子强度及温度对吸附作用的影响,研究了吸附热力学.研究结果表明,功能接枝微粒QPDMAEMA/SiO2比接枝微粒PDMAEMA/SiO2具有更高的zeta电位,在静电相互作用驱动下,微粒QPDMAEMA/SiO2对BSA具有很强的吸附能力.吸附容量随介质pH值的增大呈现先增大后减小的变化趋势,当pH值等于BSA的等电点(pI=4.7)时,具有最高的吸附容量(高达112 mg?g-1).以等电点为界,离子强度对吸附容量会产生完全相反的影响作用:当介质pH值小于BSA的等电点时,电解质浓度增大,吸附容量增高;当介质pH值等于BSA的等电点时,吸附容量几乎不随电解质的浓度发生变化.吸附过程熵值减小而且放出热量,是一个焓驱动的吸附过程.     

MICRON CORE-SHELL PARTICLES PREPARED BY GRAFTING POLYMERIZATION OF METHYL METHACRYLATE FROM NARROW DISPERSE SURFACE OF CHLOROMETHYLATED POLYDIVINYLBENZENE VIA ATRP

Grafting of poly(methyl methacrylate) from narrow disperse polymer particles by surface-initiated atom transfer radical polymerization (ATRP) was investigated. Polydivinylbenzene (PDVB) particles were prepared by dispersion polymerization with poly(N-vinyl pyrrolidone) (PVP) as the stabilizer. Chloromethylated PDVB was used as initiating core sites for subsequent ATRP of methyl methacrylate with CuBr/bpy as catalyst system. It was found that poly(methyl methacrylate) was grafted not only from the particle surfaces but also from within a thin shell layer, leading to particles size increases from 2.38-3.00μm with a core-shell structure particles. The grafted core-shell particles were characterized with FTIR, SEM, DSC.     

生物碱分子表面印迹聚合物材料的设计与制备及其分子识别特性

采用巯基/偶氮二异丁腈(AIBN)表面引发体系,实现了甲基丙烯酸缩水甘油酯(GMA)在微米级硅胶微粒表面的引发接枝聚合,制得接枝微粒PGMA/SiO2;然后使接枝大分子PGMA的环氧基团与间二氨基苯磺酸钠(SAS)分子中的对位氨基发生开环反应,将苯磺酸钠基团键合在接枝大分子侧链,制得苯磺酸盐功能化的接枝微粒SAS-PGMA/SiO2。 在对功能微粒SAS-PGMA/SiO2与苦参碱分子间的相互作用进行考察研究的基础上,以戊二醛为交联剂,实施了苦参碱分子的表面印迹,制备了苦参碱分子表面印迹材料MIP-SASP/SiO2。 实验结果表明,在近中性溶液中,功能接枝微粒SAS-PGMA/SiO2与苦参碱分子间存在静电相互作用,以此为基础所设计与制备的表面印迹材料MIP-SASP/SiO2对苦参碱分子具有特异的识别选择性与优良的结合亲和性。 相对于对照物金雀化碱而言,该印迹材料对苦参碱的识别选择性系数为10.7。     

种子表面改性法制备核壳结构PSt/SiO_2复合微球

首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360nm的单分散聚苯乙烯(PSt)种子乳液,并以EtOH/H2O混合物为分散介质,利用γ-氨丙基三乙氧基硅烷(KH-550)在25℃下对PSt微球表面进行改性,得到了表面硅烷化并带有正电荷的改性PSt种子乳液,然后在碱性条件下加入原硅酸乙酯(TEOS)使其和微球进行共水解与共缩聚,制备出了核壳结构PSt/SiO2复合微球,并利用电镜对复合微球的结构形态进行了表征.研究表明,PSt种子乳液改性时体系的zeta电位随着KH-550用量的增加而升高,当KH-550用量为PSt种子重量的1/3时,体系的zeta电位从原来的-34.5mV升高到了38mV,达到对PSt微球表面改性的最佳值;在制备PSt/SiO2复合微球时,TEOS水解缩聚形成的SiO2包覆到改性微球上的量随着反应时间的延长而增加,反应24h时达到97.9%的最大值;随介质中水含量的增加,吸附到复合微球表面上的SiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比降低到60/28.5时,得到结构均一、壳层厚度为35nm的核壳结构PSt/SiO2复合微球。     

Synthesis of miktoarm star and miktoarm star block copolymers via a combination of atom transfer radical polymerization and stable free‐radical polymerization

A trifunctional initiator, 2‐phenyl‐2‐[(2,2,6,6‐tetramethyl)‐1‐piperidinyloxy] ethyl 2,2‐bis[methyl(2‐bromopropionato)] propionate, was synthesized and used for the synthesis of miktoarm star AB₂ and miktoarm star block AB₂C₂ copolymers via a combination of stable free‐radical polymerization (SFRP) and atom transfer radical polymerization (ATRP) in a two‐step or three‐step reaction sequence, respectively. In the first step, a polystyrene (PSt) macroinitiator with dual ω‐bromo functionality was obtained by SFRP of styrene (St) in bulk at 125 °C. Next, this PSt precursor was used as a macroinitiator for ATRP of tert‐butyl acrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C, affording miktoarm star (PSt)(PtBA)₂ [where PtBA is poly(tert‐butyl acrylate)]. In the third step, the obtained St(tBA)₂ macroinitiator with two terminal bromine groups was further polymerized with methyl methacrylate by ATRP, and this resulted in (PSt)(PtBA)₂(PMMA)₂‐type miktoarm star block copolymer [where PMMA is poly(methyl methacrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.38). All polymers were characterized by gel permeation chromatography and ¹H NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2542–2548, 2003     

Fabrication and Characterization of Sulfonate‐containing Polystyrene/CaCO3 Core‐shell Nanoparticles

Polystyrene (PSt) seed latex was first prepared via soap‐free emulsion polymerization in the presence of a small amount of methacrylic acid using ammonium persulfate as initiator, and then seeded emulsion polymerization of sodium 4‐styrenesulfonate (NaSS) and St was carried out to synthesize P(St‐NaSS) core latex using 2,2′‐azobisisobutyronitrile as initiator. After that, P(St‐NaSS)/CaCO₃ core‐shell nanoparticles were fabricated by sequentially introducing Ca(OH)₂ aqueous solution and CO₂ gas into the core latex. The morphology of the core and core‐shell nanoparticles was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and the state of CaCO₃ shell was confirmed with high‐resolution scanning transmission electron microscope (HR‐STEM) and selected area electron diffraction (SAED). Results showed that PNaSS chains were successfully grafted onto the PSt seed surface, and length of the PNaSS "hairs" could be modulated by adjusting NaSS amount. Sulfonic groups of the PNaSS hairs served as additives in the formation and stabilization of amorphous CaCO₃(ACC) and prevented ACC from sequent transformation into crystalline states. The amount of the anchored CaCO₃ increased with the growth of PNaSS hair length, and reached 51 wt% (by thermalgravimetric analysis) under the optimal encapsulating temperature of 45°C. Moreover, the forming mechanism of P(St‐NaSS)/CaCO₃ core‐shell nanoparticles was proposed.     

Synthesis of membrane adsorbers via surface initiated ATRP of 2-dimethylaminoethyl methacrylate from microporous PVDF membranes

Surface-initiated atom transfer radical polymerization(SI-ATRP) was used to tether poly(2-dimethylaminoethyl methacrylate)(PDMAEMA) onto microporous PVDF membranes in order to synthesize membrane adsorbers for protein adsorption. The alkaline treatment and bromine addition reaction were used to anchor ATRP initiators on membrane surface. Then PDMAEMA was grafted from the membrane surface via SI-ATRP. Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM) revealed the chemical composition and surface topography of the PVDF-g-PDMAEMA membrane surfaces. These results showed that PDMAEMA was grafted from the membrane surface successfully and a grafting yield as high as 1500 μg/cm2 was achieved. The effects of the grafting time and the density of initiators on the static and dynamic binding capacity of bovine serum albumin(BSA) were systematically investigated. Both the static and dynamic binding capacities increase with the bromination and polymerization time. However, the benefits of the initiator density on binding capacities are limited by the graft density of PDMAEMA chains.     

单分散聚合物微球稳定Pickering乳液法制备大粒径微胶囊相变材料

采用二步加料的分散聚合法制备单分散聚甲基丙烯酸缩水甘油酯(PGMA)微球, 并使其水解, 得到水包油(O/W)型Pickering乳液稳定剂. 在Pickering乳液聚合过程中, 利用相分离机制, 形成了聚苯乙烯(PSt)和 PGMA复合为整体囊壳的微胶囊相变材料. 微胶囊平均粒径达76 μm, 囊芯含量高达83%, 相变焓达到174 J/g, 具有很高的储热容量.     

SYNTHESIS AND CHARACTERIZATION OF STRUCTURALLY WELL-DEFINED POLYMER-INORGANIC HYBRID NANOPARTICLES VIA ATRP*

Atom transfer radical polymerization (ATRP) using cuprous chloride/2,2'-bipyridine (bipy) was applied to graftpolymerization of styrene on the surface of silica nanoparticles to synthesize polymer-inorganic hybrid nanoparticles. 2-(4-Chloromethylphenyl) ethyltriethoxysilane (CTES) was immobilized on the surface of silica nanoparticles throughcondensation reaction of the silanol groups on silica with triethoxysilane group of CTES. Then ATRP of St was initiated bythis surface-modified silica nanoparticles bearing benzyl chloride groups, and formed PSt graft chains on the surface of silicananoparticles. The thickness of the graft chains increased with reaction time. End group analysis confirmed the occurrence ofATRP. Thermal analysis indicated that thermal stabilization of these resulting hybrid nanoparticles also increases withpolymerization conversion. The results above show that this "grafting from" reaction could be used for the preparation ofpolymer-inorganic hybrid nanoparticles with controlled structure of the polymer's end groups.     

SYNTHESIS AND CHARACTERIZATION OF FOUR-ARMED BLOCK POLY(STYRENE-b-p-NITROPHENYL METHACRYLATE)PREPARED BY THE ATRP METHOD*

A novel tetrafunctional initiator, C [CH_2O (CH_2)_3 OOCCH(Br)CH_3]_4 (1), was synthesized through the reaction oftetraol with α-bromopropionyl chloride, and then was used as initiator of atom transfer radical polymerization (ATRP) in thepreparation of 4-armed polystyrene (PSt) with narrow polydispersity. The structure, molecular weight and molecular weightdistribution (MWD) of each arm were studied by ~1H-NMR and GPC data of hydrolyzed products of the 4-armed PSt. TheATRP of St using 1/CuBr/bpy as initiator system is of "living" character based on the following evidence: narrow MWD,constant concentration of chain radical during the polymerization, control of molecular weight by the molar ratio of monomerconsumed to 1. The 4-armed poly(St-b-p-nitrophenyl methacrylate) [poly(St-b-NPMA)] was prepared by the ATRP ofNPMA using 4-armed PSt with terminal bromine as the initiator, and characterized by FT-IR, ~1H-NMR spectra and GPCcurves. The micelles with PSt as core, and PNPMA as shell were formed by dropping DMSO into a solution of 4-armedpoly(St-b-NPMA) in DMF, as proved by laser light scatter (LLS) method.     

Surface modification of polymer latex particles by AGET ATRP of a styrene derivative bearing a lactose residue

Grafting of a styrene derivative bearing a lactose residue, i.e., N-2-4-(vinylbenzenesulfonamido)ethyl lactobionamide (VBSAELA), onto polymer latex particles was carried out in aqueous media by activator generated electron transfer atom transfer radical polymerization (AGET ATRP). The core polymer latex particles having α-chloroester groups as ATRP-initiating groups were prepared by miniemulsion polymerization of styrene and 2-chloropropionyloxyethyl methacrylate (CPEM) in the presence of a polymerizable surfactant, i.e., N,N-dimethyl-N-dodecyl-N-2-methacryloyloxyethylammonium bromide (C₁₂Br). AGET ATRP was initiated with tris[(2-pyridylmethyl)amine] copper (II) dichloride and l-ascorbic acid. Dynamic light scattering (DLS) revealed that the P(St-CPEM)-g-P(VBSAELA) particles possess graft layers of 10 nm in thickness on the core particles of 91 nm in diameter. Critical coagulation concentration measurement revealed that the dispersion stability of the particles in water increased due to hydrated P(VBSAELA) shell layers. Adsorption of bovine serum albumin (BSA) onto the particles was considerably suppressed by the hydrated shell layers.     

Fuzzy ternary particle systems by surface-initiated atom transfer radical polymerization from layer-by-layer colloidal core-shell macroinitiator particles

We report the synthesis of ternary polymer particle material systems composed of (a) a spherical colloidal particle core, coated with (b) a polyelectrolyte intermediate shell, and followed by (c) a grafted polymer brush prepared by surface-initiated polymerization as the outer shell. The layer-by-layer (LbL) deposition process was utilized to create a functional intermediate shell of poly(diallyl-dimethylammonium chloride)/poly(acrylic acid) multilayers on the colloid template with the final layer containing an atom transfer radical polymerization (ATRP) macroinitiator polyelectrolyte. The intermediate core-shell architecture was analyzed with FT-IR, electrophoretic mobililty (zeta-potential) measurements, atomic force microscopy, and transmission electron microscopy (TEM) techniques. The particles were then utilized as macroinitiators for the surface-initiated ATRP grafting process for poly(methyl methacrylate) polymer brush. The polymer grafting was confirmed with thermo gravimetric analysis, FT-IR, and TEM. The polymer brush formed the outermost shell for a ternary colloidal particle system. By combining the LbL and surface-initiated ATRP methods to produce controllable multidomain core-shell architectures, interesting functional properties should be obtainable based on independent polyelectrolyte and polymer brush behavior.     

Synthesis of composite particles through emulsion polymerization based on silica/fluoroacrylate-siloxane using anionic reactive and nonionic surfactants

The composite particles with core/shell structure resulting from the combination of silica seed and hydrophobic copolymer (dodecafluoroheptyl methacrylate (DFMA), gamma-methacryloxypropyltriisopropoxidesilane (MAPTIPS), methyl methacrylate, butyl acrylate) were synthesized by emulsion polymerization. The amount of the silica seeds, concentration of reactive surfactant, as well as the addition of DFMA and MAPTIPS, have strong influences on the morphology of composite particles. It has been shown that it would be possible to produce stable organic/inorganic composite particles with inhomogeneous core/shell structure encapsulated by hydrophobic fluorinated acrylate even though using unmodified silica particles and admixture of anionic and nonionic surfactants. However, there was an obvious difference on the morphologies of core-shell structure whether the DFMA and MAPTIPS were added or not. It was concluded that two kinds of polymerization approaches might coexist in the presence of DFMA and MAPTIPS for raw silica. One clear advantage of this process is that there is only one silica bead for each composite particle. This kind of stable core-shell structural hybrid latex is useful for preparing high performance hydrophobic coating.