Interaction Between an Acidic Extractant and an Octadecylamino Group Introduced into a Grafted Polymer Chain

Abstract

Poly‐glycidyl methacrylate (GMA) was appended onto a porous membrane of a hollow‐fiber form with an epoxy group density of 14 mol per kg of the starting porous membrane. Octadecylamine was added to the epoxy group of the polymer brush at a maximum molar conversion of the epoxy group into the octadecylamino group of 59%. An acidic extractant, bis(2,4,4,‐trimethylpentyl)phosphinic acid (Cyanex 272), was impregnated on the octadecylamino group by immersion of the octadecylamine‐added porous membrane in Cyanex 272/ethanol solution. The amount of impregnated extractant was 1.4 mol per kg of the GMA‐grafted porous membrane at a molar conversion of 59%. The phosphinic acid moiety of Cyanex 272 was attracted by the amino part of the octadecylamino group of the polymer brush to swell the entire volume of the porous membrane. This swelling compensated for the pore volume reduction caused by grafting the charged polymer brush to the pore surfaces of the porous membrane. The impregnated Cyanex 272 was repositioned on the charged polymer brush in response to the properties of surrounding liquids. The hydrophobic interaction enables the hydrophobic moiety of Cyanex 272 to associate with the octadecyl part of the octadecylamino group of the polymer brush to capture zinc ions. The binding efficiency of the Cyanex 272‐impregnated polymer brush for zinc ion was as high as 93%.     

Surface functionalization of nanodiamond particles via atom transfer radical polymerization

Ultradispersed diamond (UDD)/polymer brushes having excellent solution dispersibilities are prepared by atom transfer radical polymerization (ATRP) using the “grafting-from” synthesis strategy. ATRP initiators, covalently attached to oxidized surface carbon atoms of UDD aggregates using esterification chemistry, initiate polymerization of methacrylate monomers to form hydrophobic UDD/poly(iso-butyl methacrylate) and UDD/poly(tert-butyl methacrylate) polymer brushes. Acid hydrolysis of a UDD/poly(tert-butyl methacrylate) polymer brush affords a hydrophilic UDD/poly(methacrylic acid) polymer brush. Based on surface area measurements and GPC data, the calculated surface density of a representative UDD/polymer brush material is ca. five polymer chains/100 nm². A wide variety of UDD/polymer brush materials having controlled dispersibility and functional group reactivity are now potentially available using this synthesis strategy.     

Magnetic Nanoparticle Polymer Brush Catalysts: Alternative Hybrid Organic/Inorganic Structures to Obtain High, Local Catalyst Loadings for Use in Organic Transformations

A new class of hybrid organic/inorganic molecular catalysts with high, local catalyst concentrations is demonstrated by supporting organic and organometallic catalysts on magnetic nanoparticle based polymer brushes (MPB). Poly(styrene) brushes containing Co(III)-salen or piperazine side chains are prepared via atom-transfer radical polymerization (ATRP) from Fe₃O₄ nanoparticles modified with appropriate initiator molecules. The polymer brush architecture promotes the cooperative interactions required for Co-salen catalyzed ring-opening of epoxides as demonstrated in the hydrolytic kinetic resolution of rac-epichlorohydrin. In addition, the piperazine functionalized MPB catalyst contains the high catalyst concentration that is required for promoting the Knoevenagel condensation of benzaldehyde and malononitrile with this type of amine catalyst. All the MPB catalysts were easily removed from solution via application of a magnetic field, allowing straightforward recovery and reuse. The versatile MPB architecture can be used to create a variety of recoverable supported organic or organometallic catalysts.     

可逆失活自由基界面聚合

界面聚合通常指限定在液-液或液-固界面上进行的聚合反应,散见于少数高活性的缩聚反应体系。20世纪90年代,以RAFT聚合、ATRP等为代表的可逆失活自由基聚合（reversible deactivation radical polymerization,RDRP）因其兼具传统自由基聚合和活性阴离子聚合的优点,广泛用于聚合物链结构的可控制备。另一方面,RDRP已被用于构建更为普适的界面聚合反应,基于RDRP的界面聚合已发展成为一种可控制备具有精准纳米结构的功能性聚合物产品的新方法。本文以RAFT液-液界面聚合为主,阐述了RAFT法和ATRP法在液-液界面、液-固界面进行“活性”聚合的反应机理,总结了该领域的研究进展。在此基础上,重点介绍“活性”界面聚合在构建纳米（中空）胶囊、纳米界面工程与纳米分散以及纳米聚合物刷表面等方面的潜在应用前景。     

Poly(l-lactide) comb polymer brushes on the surface of clay layers

Poly(l-lactide) (PLLA) comb polymers on poly(hydroxyethyl methacrylate) (PHEMA) backbone were prepared on the surface of clay layers by a combination of in situ atom transfer radical polymerization (ATRP) and ring-opening polymerization. An ATRP initiator with a quaternary ammonium salt end group was intercalated into the interlayer spacing of clay. PHEMA polymer brushes on the surface of clay layers were prepared by in situ ATRP. PLLA comb polymers on PHEMA backbone were prepared by ring-opening polymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that with the increase of comb chain length more and more exfoliated structure was created. Aggregation of wormlike comb polymer brushes on the surface of clay layers was observed by TEM. Differential scanning calorimeter (DSC) results indicated that both the melting points and glass transition temperatures of the comb polymer brushes increase with the increase of comb chain length. The equilibrium melting temperature of the comb polymer brush on the surface of clay layers is lower than cleaved polymer. An atomic force microscopy (AFM) image proves the formation of wormlike structure by cleaved comb polymers.     

原子转移自由基聚合原理及应用

介绍了有关原子转移自由基聚合(ATRP)的聚合原理。最新研究表明:应用ATRP法进行聚合反应可以制备接枝聚合物、嵌段聚合物、超支化聚合物和其它有机/无机混合型聚合物等。ATRP在高分子聚合反应领域具有十分广阔的应用前景。     

可控/活性聚合在无机粒子表面接枝研究进展

介绍了一些主要的可控／活性自由基聚合法,包括氮氧调解自由基聚合法（NMRP）、原子转移自由基聚合法（ATRP）、可逆加成断裂链转移聚合法（RAFT）在粒子表面接枝聚合形成无机纳米粒子／聚合物的壳核结构,达到了对粒子改性的目的。并提出了一些目前研究中存在的问题,对可控／活性聚合应用的发展进行了展望。     

CdS/CdSe quantum dot co-sensitized graphene nanocomposites via polymer brush templated synthesis for potential photovoltaic applications

CdS/CdSe quantum dot (QDs) co-sensitized graphene sheets have been obtained via polymer brush templated synthesis. Firstly, the anionic functional polymer (polymethacrylate cadmium) was grafted via the surface initiated atomic transfer radical polymerization (ATRP) using a macromolecular initiator, which contains polymerized pyrene units for chemical anchoring on graphene surface and alkyl bromines to initiate ATRP. Then, the coordinated cadmium in the polymer chains can act as a source precursor for QDs. After reaction, polymer brushes can be recovered and act as the nanoreactor via the absorption of cadmium ions by carboxylate groups. So, high density QDs can be multiply uploaded onto the graphene surface by repeated steps. The as-prepared composite materials exhibited significantly enhanced visible light response compared to plain graphene, and have potential applications as the platform to build solar cell assembles.     

Hydrophilic modification of P(VDF-co-CTFE) porous membranes

This paper describes fabrication of a poly(vinylidene difluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) porous membrane via non-solvent induced phase inversion and subsequent hydrophilic modification using high efficient surface initiated atom transfer radical polymerization (ATRP). The effect of viscosities of casting solutions on microstructures of the P(VDF-co-CTFE) membrane was investigated. The surface chemistry, thermal stability, morphological structure, and hydrophilicity of the modified membranes were evaluated by Fourier Transform Infrared Attenuated Total Reflection (FTIR-ATR), Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM), and contact angle measurements, respectively. The degree of grafting and the degree of swelling were measured to analyze the effect of polymerization time on the wettability. The mechanical strength of the membranes after modification was also investigated. The permeability and fouling resistance were evaluated according to pure water flux and protein solution filtration measurements. The results demonstrate that the hydrophobic P(VDF-co-CTFE) membrane can be feasibly modified by immobilization of hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) brushes via surface initiated ATRP.     

Robust grafting of PEG-methacrylate brushes from polymeric coatings

A study is presented of the grafting of poly(ethylene glycol)methyl ether methacrylate (PEGMA) from polymeric macroinitiator films to form well-defined polymer brushes, using activators generated/regenerated by electron transfer (AGET/ARGET) atom transfer radical polymerization (ATRP). Polymer brush coatings can potentially be obtained on surfaces of virtually any shape and composition, because of the ease of conformal casting of the anchoring macroinitiator film. Polymer brush coatings are synthesized in a robust way, as ARGET and AGET ATRP require little to no deoxygenation and make use of stable catalysts. The monomer, catalyst, ligand and reducing agent concentrations, the amount and type of initiating moiety in the anchoring films, and the choice of solvents are optimized, resulting in control over the rate of reaction, and the molecular weight of poly(PEGMA). The best conditions are determined for the formation of a poly(PEGMA) brush with high grafting density, controlled thickness and “living” ends available for post-functionalization.     

Modification of polysulfone membranes via surface‐initiated atom transfer radical polymerization and their antifouling properties

Surface‐initiated atom transfer radical polymerization (ATRP) was used to tailor the functionality of polysulfone (PSF) membranes. A simple one‐step method for the chloromethylation of PSF under mild conditions was used to introduce surface benzyl chloride groups as active ATRP initiators. Covalently tethered hydrophilic polymer brushes of poly(ethylene glycol)monomethacrylate and 2‐hydroxyethyl methacrylate and their block copolymer brushes were prepared via surface‐initiated ATRP from the chloromethylated PSF surfaces. A kinetic study revealed that the chain growth from the membranes was consistent with a controlled process. X‐ray photoelectron spectroscopy was used to characterize the surface‐modified membrane after each modification stage. Protein adsorption experiments revealed substantial antifouling properties of the grafted PSF membranes in comparison with the those of the pristine PSF surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of controlled thermoresponsive PET track‐etched membranes by ATRP method

Controlled thermoresponsive PET track‐etched membranes were synthesized by grafting N‐isopropylacrylamide (NIPAAm) onto the membrane surface via atom transfer radical polymerization (ATRP). The initial measurements were made to determine the anchoring of ATRP initiator on PET membrane surface. Thereafter, polymerization was carried out to control the mass of polymer by controlling reaction time grafted from the membrane surface and, ATR‐FTIR, grafting degree measurements, water contact angle measurements, TGA, and SEM were used to characterize changes in the chemical functionality, surface and pore morphology of membranes as a result of modification. Water flux measurements were used to evaluate the thermoresponsive capacity of grafted membranes. The results show the grafted PET track‐etched membranes exhibit rapid and reversible response of permeability to environmental temperature, and its permeability could be controlled by controlling polymerization time using ATRP method. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Direct Controlled Polymerization of Ionic Monomers by Surface-Initiated ATRP Using a Fluoroalcohol and Ionic Liquids

Surface-initiated atom transfer radical polymerization (ATRP) of (2-methacryloyloxyethyl)trimethylammonium chloride (MTAC), 3-(N-2-methacryloyloxyethyl-N,N-dimethyl) ammonatopropanesulfonate) (MAPS), and 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out in 2,2,2-trifluoroethanol (TFE) containing a small amount of 1-hexyl-3-methylimidazolium chloride at 60 °C to produce well-defined ionic polymer brushes and the corresponding free polymers with predictable number-average molecular weight (M_n, 1×10⁴−3×10⁵ g mol⁻¹) and narrow molecular weight dispersity (M_w/M_n<1.2). A first-order kinetic plot for ATRP of MTAC and MAPS revealed a linear relationship between the monomer conversion index (ln([M]₀/[M])) and polymerization time. Reduction in polymerization rates was observed with an increase in ionic liquid concentration. The M_n of both poly(MTAC) and poly(MAPS) increased in proportion to the conversion. The sequential polymerization of MAPS initiated with the chain ends of poly(MAPS) produced the postpolymer with quantitative efficiency. The thickness of the polymer brush was controllable from 5 to 100 nm based on the M_n of the polymer. These results suggest the successful control of the polymerization of sulfobetaine-type methacrylates owing to the TFE and ionic liquids. In particular, the high affinity of TFE for the sulfobetaine monomers and polymers yielded a homogeneous polymerization media to improve surface-initiated polymerization generating the polymer brushes on the substrate surface as well as the free polymers formed in the solution. The effect on ATRP of the chemical structure of ionic liquids and ligands for copper catalyst was also investigated.     

丙烯酸酯改性水性聚氨酯的研究进展

介绍了聚氨酯/丙烯酸酯(PUA)复合乳液的制备方法,包括物理共混、交联共混、复合乳液共聚、核/壳结构乳液共聚法及互穿聚合物网络(IPN)法等,同时从无机纳米粒子改性、氟改性、有机硅改性和环氧树脂(EP)改性等方面对改性PUA复合乳液的研究进展进行了概述。     

Esterification of lauric acid using lipase immobilized in the micropores of a hollow-fiber membrane

A porous anion-exchange hollow-fiber membrane was prepared by radiation-induced graft polymerization and chemical modification to immobilize lipase for enzymatic reaction in an organic solvent. The amount of anion-exchange group introduced to the porous hollow-fiber membrane was 2.5 mol/kg_fiber. A lipase solution was allowed to permeate through the porous anion-exchange hollow-fiber membrane, and lipase molecules that adsorbed onto the grafted polymer brush were cross-linked with glutaraldehyde. The lipase was immobilized at a density of 0.14 kg_lipase/kg_fiber, which was equivalent to a degree of multilayer binding of 20. Esterification was carried out by passing a solution of lauric acid and benzyl alcohol in anhydrous issoctane through the lipase-immobilized membrane, and lipase activity was determined. A reaction percentage of 50% was achieved at space velocity 68 h⁻¹. The maximum immobilized lipase and native lipase activities were 8.9 and 0.38 mol/(h·kg_lipase), respectively. Thus, the activity of the immobilized lipase was 23.4 times higher than that of the native lipase.     

Stimuli response of cationic polymer brush prepared by ATRP: Application in peptide fractionation

Random cationic copolymer brushes composed of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and N-isopropylacrylamide (NIPAAm) were synthesized using the atom transfer radical polymerization (ATRP) method. The effects of varying the monomer feed ratios (30:70 and 70:30 DMAEMA:NIPAAm) and polymerization times on the film height, morphology and stimuli response to pH of the brush were evaluated. While the polymerization time was found to have little influence on the properties of the brushes, the monomer feed ratios had a great impact. The 70% DMAEMA polymer brush had similar height as the 30% DMAEMA brush after 45 min; however, it had a greater response to pH and morphological change compared to the 30% DMAEMA. The 70% DMAEMA brush was used to demonstrate an efficient approach to alleviate the ion suppression effect in MALDI analysis of complex mixtures by effectively fractionating a binary mixture of peptides prior to MALDI-MS analysis.     

Architecture of rod–brush block copolymers synthesized by a combination of coordination polymerization and atom transfer radical polymerization

A combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod–brush block copolymers. The procedure included the following steps: (1) the monoesterification reaction of ethylene glycol with 2-bromoisobutyryl bromide (BIBB) yielded the bifunctional initiator monobromobutyryloxy ethylene glycol and (2) a trichlorocyclopentadienyl titanium (CpTiCl₃; bifunctional initiator) catalyst was prepared from a mixture of CpTiCl₃ and bifunctional initiator. The coordination polymerization of n-butyl isocyanate initiated by such a catalyst provided a well-defined macroinitiator, poly(n-butyl isocyanate)–bromine (PBIC–Br). (3) The ATRP method of 2-hydroxyethyl methacrylate initiated by PBIC–Br provided rod [poly(n-butyl isocyanate) (PBIC)]–coil [poly(2-hydroxyethyl methacrylate) (PHEMA)] block copolymers with a CuCl/CuCl₂/2,2′-bipyridyl catalyst. (4) The esterfication of PBIC-block-PHEMA with BIBB yielded a block-type macroinitiator, and (5) ATRP of methyl methacrylate with a block-type macroinitiator provided rod–brush block copolymers. We found from the solution properties that such rod–brush block copolymers formed nanostructured macromolecules in solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of binary mixed homopolymer brushes by combining atom transfer radical polymerization and nitroxide-mediated radical polymerization

This communication describes a novel strategy to synthesize binary mixed homopolymer brushes from mixed self-assembled monolayers (SAMs) on silica substrates by combining atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP). Mixed SAMs terminated by ATRP and NMRP initiators were prepared by coadsorption of two corresponding organotrichlorosilanes from toluene solutions. Mixed poly(methyl methacrylate) (PMMA)/polystyrene (PS) brushes were synthesized by ATRP of MMA at 80 °C followed by NMRP of styrene at 115 °C. Corresponding ‘free’ initiators were added into the solutions to control the polymerizations. We have found that the brush thickness increases with molecular weight in a nearly linear fashion. For a series of binary brushes consisting of PMMA of molecular weight of 26,200 and PS of various molecular weights, we have observed a transition in water contact angles with increasing PS molecular weight after CH₂Cl₂ treatment. Moreover, binary mixed polymer brushes with comparable molecular weights for two grafted polymers undergo reorganization in response to environmental changes, exhibiting different wettabilities.     

活性自由基聚合的新进展--原子转移自由基聚合

活性自由基聚合是目前高分子科学中最为活跃的研究领域之一，原子转移自由基聚合(ATRP)反应是实现活性聚合的一种颇为有效的途径．也是高分子化学领域的最新研究进展之一。ATRP的独特之处在于使用了卤代烷作引发剂，并用过渡金属催化剂或退化转移的方式，有效地抑制了自由基双基终止的反应。ATRP可以同时适用于非极性和极性单体，可以制备多种结构形式的、结构清晰的高分子化合物。可实现众多单体的活性／可控自由基聚合。介绍了ATRP的研究进展，包括ATRP反应的特点、聚合反应机理、应用、研究现状及前景展望。     

Modification of carbon nanotubes with a nanothin polydopamine layer and polydimethylamino-ethyl methacrylate brushes

The work reports on a nondestructive pathway to produce polymer brush modified carbon nanotubes (CNTs) through surface-initiated polymerization followed by nanoparticle uploading. First, polydopamine layers with high surface coverage were formed on CNTs by spontaneous oxidative polymerization of dopamine. These were then used as the reactive layer for subsequent initiator attachment and brush grafting. Atom transfer radical polymerization of dimethylamino-ethyl methacrylate was initiated from the initiator layer, resulting in the formation of uniform polydimethylamino-ethyl methacrylate (PDMAEMA) brushes on the CNT surface. These were further quaternized by the reaction with CH₃I to form cationic Quaternized-PDMAEMA brushes (Q-PDMAEMA). The reversible solubilities of PDMAEMA- and Q-PDMAEMA-modified CNTs were achieved by switching between different solutions. Palladium nanoparticles were attached onto the CNTs using Q-PDMAEMA mediated anion exchange followed by in situ reduction using NaBH₄. The electrocatalytic behavior of the material was studied using an electrochemical method.