Porous multifunctional fluoropolymer composite foams prepared via humic acid modified Fe3O4 nanoparticles stabilized Pickering high internal phase emulsion using cationic fluorosurfactant as co-stabilizer

Fluoropolymers are very important owing to their excellent application performances, especially in extreme conditions. On the other hand, the preparation of porous fluoropolymers is a difficult task due to unavailability of suitable surfactants as well as tedious synthesis steps. Here we prepared multifunctional porous fluoropolymer composite foams with a simple process of “high internal phase emulsion (HIPE)” by using humic acid modified iron oxide nanoparticles (HA-Fe₃O₄ NPs) and cationic fluorosurfactant (CFS) (PDMAEMA-b-PHFBA) as co-stabilizer. The inclusion of HA-Fe₃O₄ NPs in the system made fluoro-HIPE more stable than the emulsion prepared using only CFS or other conventional stabilizers. Morphology of the prepared polyHIPE was easily controlled by altering the concentration of HA-Fe₃O₄ and/or CFS in the original formulation. Adjustment of the porous structure with open/close cells was performed and the average diameter of the pores tuned between 4.9 and 23 μm. With the increase in specific surface area by using nanoparticles (NPs) and CFS as co-surfactants, Pickering HIPE monoliths adsorbed double amount of oil compared to foams based solely on HIPE template. Multiple functional groups were bound onto Fe₃O₄ NPs through HA modification that made the fluoro-monolith capable of adsorbing dye, i.e. methylene blue, from water. A simple centrifugation enabled regeneration of the oil soaked foams and adsorption capacity was not decreased after 10 adsorption/regeneration cycles.     

Synthesis of thermo- and pH-sensitive polyelectrolyte brushes by combining thermo-controlled emulsion polymerization and photo-emulsion polymerization

Bifunctional spherical polyelectrolyte brushes(SPBs)with tunable thermo-and pH-sensitivity are synthesized by combining thermo-controlled emulsion polymerization and photo-emulsion polymerization.They consist of a spherical polystyrene core and a shell of mixed brushes of poly(N-isopropylacrylamide)(PNIPAM)and poly(acrylic acid)(PAA) whose composition can be easily modulated by the dose of monomers.The kinetics of SPB synthesis as well as their size change with temperature and pH is determined by dynamic light scattering(DLS).The scanning electron microscopy(SEM) images show that the bifunctional SPBs have a defined spherical morphology with a narrow size distribution.     

Novel Porous Monolithic Column Using Poly(high internal phase emulsion) Methacrylate as Materials for Immunoglobulin Separation Performance on HPLC

A novel porous polymeric monolithic column based on poly(high internal phase emulsion) methacrylate monolith was prepared and applied to fast separation of proteins. The block copolymer chemistry of high internal phase emulsions was used in the experiment. These unique properties, together with high porosity, good mechanical property, chemical modification of the surface make themselves superior in monolithic medium applications. Morphology of the monolithic material was studied by scanning electron microscopy. The stability of the emulsion and the load of hydroxyl groups–the active group of the monolithic column were investigated. Additionally, the capabilities of separation of this column in conjunction with high performance liquid chromatography (HPLC) were investigated. Immunoglobulin was separated from human plasma and chicken egg yolk with high resolution on the hydrophobic interaction chromatographic column in a short time. The effects of pH and concentration of mobile phase (buffer) on the elution of immunoglobulin were investigated. Moreover, fast separation of a two mode protein mixture (α‐amylase and lysozyme) on the monolith was achieved within 1.5 min at a velocity of 1445 cm·h^?1. As a result, good separation was achieved, and stable low back pressure drop was ensured at high throughput elution with an even longer column.     

Semicontinuous seeded cationic emulsion polymerization of styrene: The effects of the concentration and type of cationic surfactant

The objective of this work was to analyze the effects of the concentration and type of cationic surfactant on the kinetic features (instantaneous and overall conversions) and colloidal characteristics [mean particle diameter, particle size distribution (PSD), and surface charge density] in the semicontinuous seeded cationic emulsion polymerization of styrene. 2,2′‐Azobis(N,N′‐dimethyleneisobutyramidine)dihydrochloride was used as an initiator. The surfactants were dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (HDTAB). So that the evolution of some polymeric and colloidal characteristics of the synthesized latices could be followed, the overall and instantaneous conversions were defined and determined gravimetrically. The PSDs and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The surface charge density was determined by conductimetric titration. The evolution of the instantaneous conversions, the total number of particles, and the PSDs of the different reactions were related to the nucleation, growth, and coagulation processes taking place in the semicontinuous seeded emulsion polymerizations. The PSDs obtained from the reactions carried out with the emulsifier DTAB, at a concentration equal to its critical micelle concentration (cmc) and at a concentration twice its cmc, presented more and smaller particles than those obtained by the addition of HDTAB to the polymerization recipe. At lower emulsifier concentrations equal to half of the cmc, the system had lower colloidal stability with DTAB. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2322–2334, 2003     

Polymeric and colloidal features of latex particles with surface amino groups obtained by semicontinuous seeded cationic emulsion polymerization*

Monodisperse latex particles with different amounts of surface amino and amidine groups were synthesized by means of a semicontinuous seeded cationic emulsion polymerization of styrene and a cationic monomer. High partial overall conversions for styrene and limited ones for the cationic monomer were achieved. A reliable method for the quantification of surface amidine and amino groups was developed. It was found that the amount of surface amidine groups provided by the cationic initiator was higher when the amount of cationic monomer added increased. The value for the partition coefficient of the cationic monomer indicated that this polymerizes with the same probability in the water phase as in the particle. The colloidal stability, in terms of critical coagulation concentration, shows that the latexes would be useful as polymeric supports in immunoassays. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3878–3886, 2005     

Living cationic polymerization of dihydrofuran and its derivatives

Cationic polymerization of 2,3‐dihydrofuran (DHF) and its derivatives was examined using base‐stabilized initiating systems with various Lewis acids. Living cationic polymerization of DHF was achieved using Et_1.5AlCl_1.5 in toluene in the presence of THF at 0 °C, whereas it has been reported that only less controlled reactions occurred at 0 °C. Monomer‐addition experiments of DHF and the block copolymerization with isobutyl vinyl ether demonstrated the livingness of the DHF polymerization: the number–average molecular weight of the polymers shifted higher with low polydispersity as the polymerization proceeded after the monomer addition. Furthermore, this base‐stabilized cationic polymerization system allowed living polymerization of ethyl 1‐propenyl ether and 4,5‐dihydro‐2‐methylfuran at ?30 and ?78 °C, respectively. In the polymerization of 2,3‐benzofuran, the long‐lived growing species were produced at ?78 °C. The obtained polymers have higher glass transition temperatures compared to poly(acyclic alkyl vinyl ether)s. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4495–4504, 2008     

The cationic polymerization of N-vinyl-2-pyrrolidone initiated electrochemically by anodic polarization on a Pt surface

The electroinitiated polymerization of N-vinyl-2-pyrrolidone has been investigated. After electrolysis at controlled potential, a thin, covering, and homogeneous film of poly(N-vinyl-2-pyrrolidone) appears on the electrode. The insolubility of the polymer in its classical solvents implies the existence of a true chemical grafting of macromolecules on the platinum surface. Chain propagation occurs by a cationic mechanism initiated by a direct electron transfer leading to grafted cations on the surface, followed by the nucleophilic attack of neutral molecules. The molecular weight of the polymer was estimated by gel permeation chromatography after having mechanically removed the film from the electrode. A molecular weight distribution curve showing an average value of 16,000 was observed. © 1994 John Wiley & Sons, Inc.     

Synthesis and characteristics of the poly(carboxybetaine)s and the corresponding cationic polymers

Two types of carboxybetaines and their corresponding cationic monomers and polymers are synthesized in this study. Comparing the chemical shifts of the methylene groups in the cationic monomers and carboxybetaines in both ¹H- and ¹³C-NMR spectra reveal that the respective methylene groups are clearly distinguished from their chemical shifts in ¹H- and ¹³C-NMR spectra. The solubilities, moisture regain properties, and solution properties of the poly(carboxybetaine)s and cationic polymers are investigated in relation to their molecular structures. Because the cationic polymers were ionized in an aqueous solution, the cationic polymers were more soluble than the poly(carboxybetaine). For the various functional groups of poly(carboxybetaine)s and cationic polymers, the order of tendency for moisture regain is  COO >  CONH . Results obtained from the reduced viscosity for cationic poly(TMMPAMS) are reversed from that for zwitterionic poly(DMAEAPL). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3527–3536, 1997     

Living cationic polymerization of α‐methyl vinyl ethers using SnCl4

Cationic polymerization of α‐methyl vinyl ethers was examined using an IBEA‐Et_1.5AlCl_1.5/SnCl₄ initiating system in toluene in the presence of ethyl acetate at 0 ～ ?78 °C. 2‐Ethylhexyl 2‐propenyl ether (EHPE) had a higher reactivity, compared to corresponding vinyl ethers. But the resulting polymers had low molecular weights at 0 or ?50 °C. In contrast, the polymerization of EHPE at ?78 °C almost quantitatively proceeded, and the number‐average molecular weight (M_n) of the obtained polymers increased in direct proportion to the EHPE conversion with quite narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.05). In monomer‐addition experiments, the M_n of the polymers shifted higher with low polydispersity as the polymerization proceeded, indicative of living polymerization. In the polymerization of methyl 2‐propenyl ether (MPE), the living‐like propagation also occurred under the reaction conditions similar to those for EHPE, but the elimination of the pendant methoxy groups was observed. The introduction of a more stable terminal group, quenched with sodium diethyl malonate, suppressed this decomposition, and the living polymerization proceeded. The glass transition temperature of the obtained poly(MPE) was 34 °C, which is much higher than that of the corresponding poly(vinyl ether). This poly(MPE) had solubility characteristics that differed from those of poly(vinyl ethers). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2202–2211, 2008     

Thermoresponsive NIPAM block copolymers containing densely grafted poly(vinyl ether) brushes synthesized by a combination of living cationic polymerization and RAFT polymerization

Diblock copolymers consisting of a multibranched polymethacrylate segment with densely grafted poly[2‐(2‐methoxyethoxy)ethyl vinyl ether] pendants and a poly(N‐isopropylacrylamide) segment were synthesized by a combination of living cationic polymerization and RAFT polymerization. A macromonomer having both a poly[2‐(2‐methoxyethoxy)ethyl vinyl ether] backbone and a terminal methacryloyl group was synthesized by living cationic polymerization. The sequential RAFT copolymerizations of the macromonomer and N‐isopropylacrylamide in this order were performed in aqueous media employing 4‐cyanopentanoic acid dithiobenzoate as a chain transfer agent and 4,4′‐azobis(4‐cyanopentanoic acid) as an initiator. The obtained diblock copolymers possessed relatively narrow molecular weight distributions and controlled molecular weights. The thermoresponsive properties of these polymers were investigated. Upon heating, the aqueous solutions of the diblock copolymers exhibited two‐stage thermoresponsive properties denoted by the appearance of two cloud points, indicating that the densely grafted poly[2‐(2‐methoxyethoxy)ethyl vinyl ether] pendants and the poly(N‐isopropylacrylamide) segments independently responded to temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Control of cationic nanogel PEGylation in heterogeneous ARGET ATRP emulsion polymerization with PEG macromonomers

Crosslinked cationic nanoscale networks with hydrophobic cores are an environmentally robust alternative to self‐assembled polymeric drug delivery carriers with respect to therapeutic encapsulation and stability to dilution. However, the ability to tune the degree of PEG incorporated into nanogels during synthesis is more challenging. In this work, biodegradable cationic nanogels were synthesized by ARGET ATRP emulsion polymerization in a single step. The density of PEG in the final nanogels ranged from zero to 40 wt % and was dependent on the feed concentration of PEG monomer, surfactant concentration, surfactant hydrophilic–lipophilic balance, and the ratio of cationic to nonionic surfactant. A comprehensive analysis of nanogel material properties as a function of PEG graft density is presented including analysis of composition, monomer conversion, thermal properties, size, surface charge, and degradation. This study provides a robust analysis for the synthesis of degradable cationic nanogels via a controlled radical polymerization with predictable degrees of PEGylation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1536–1544     

Metallocene-mediated cationic polymerization of vinyl ethers: Kinetics of polymerization and synthesis and characterization of statistical copolymers

The cationic polymerization of ethyl, n-butyl and iso-butyl vinyl ether, EVE, BVE and iBVE, respectively, was efficiently conducted using bis(η⁵-cyclopentadienyl)dimethyl hafnium, Cp₂HfMe₂, or bis(η⁵-cyclopentadienyl)dimethyl zirconium, Cp₂ZrMe₂ in combination with either tris(pentafluorophenyl)borate, B(C₆F₅)₃, or tetrakis(pentafluorophenyl)borate dimethylanilinum salt, [B(C₆F₅)₄]^?[Me₂NHPh]⁺, as initiation systems. The evolution of polymer yield, molecular weight and molecular weight distribution with time was examined. In addition, the influence of the initiating system, the monomer and the reaction conditions on the control of the polymerization was studied. Furthermore, statistical copolymers of EVE with BVE were prepared employing Cp₂HfMe₂ and [B(C₆F₅)₄]^?[Me₂NHPh]⁺ as the initiation system. The reactivity ratios were estimated using both linear graphical and non-linear methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The glass transition temperatures, Tg, of the copolymers were measured by Differential Scanning Calorimetry, DSC, and the results were compared with predictions based on several theoretical models. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies.     

高内相乳液法制备整体柱及其分离性能研究

建立了高内相乳液(HIPE)法制备以甲基丙烯酸十二烷酯为功能单体(LMA),二乙烯基苯(DVB)为交联剂的新型毛细管电色谱整体柱。polyHIPE整体柱利用扫描电镜与BET进行了表征,表明了制备的整体柱具有较大的孔径与较好的比表面积,更好的通透性,可更好地满足高效快速分离分析的需要。实验中K2S2O8不仅可以作为引发剂,同时加热后残基能为固定相提供电渗流。优化表面活性剂span80含量、W/O比例对整体柱制备的影响,以硫脲与苯系物为目标化合物考察了整体柱的分离性能与效果。该方法用实际水样品苯系物分析,取得良好的效果。     

Synthesis of high molecular weight polymer nanoparticles by [Cp2ZrCl2] catalyzed emulsion polymerization

An early transition metal metallocene compound, Cp₂ZrCl₂, with an anionic surfactant, sodium n‐dodecyl sulfate (SDS) as emulsifier and NaBPh₄ as cocatalyst has been found to be an effective catalytic system for polymerization and copolymerization of monomers like styrene and methyl methacrylate in aqueous medium. The diameters of the latex particles were found to be in between 20 and 40 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Conjugated polyelectrolyte with pendant carboxylate groups: Synthesis,photophysics, and pH responses in the presence of surfactants

This article reports the synthesis, optical properties, and pH responses of a water‐soluble poly(phenylene ethynylene) with pendant carboxylate groups. This conjugated polyelectrolyte, PPE‐OBS, was prepared via a facile synthetic route, using 1,4‐di(ethyl 4‐oxy‐butyrate)‐2,5‐diiodo‐benzene as polymeric monomer and followed by the alkali induced saponification. PPE‐OBS absorbs strongly in the blue region and emits a moderately intense fluorescence. However, it subjects to unstable emission in neutral aqueous media, which is believed to arise because the polymer tends to become more hydrophobic via protonation and to form much heavier aggregates (clusters). Subsequent studies on the interaction and stabilization of PPE‐OBS with various surfactants indicate that its fluorescence stability can be largely improved in the presence of a small amount of surfactant. More interestingly, even at low pH, the surfactant‐stabilized polyelectrolyte with its pendant groups being ? COOH rather than ? COO^? remains water‐soluble and emits efficiently, which is expected of great significance for the covalent linkage to bio‐molecules. In addition, the sensitive pH response in emission spectrum of PPE‐OBS/surfactant complex over a relatively wide range suggests surely a potential access to the fluorescent sensing of pH variation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3056–3065, 2009     

A benign initiating system for cationic polymerization of isobutyl vinyl ether: Silver salt/aryl(alkyl) halide/lewis base

Aryl(alkyl) halides and silver salts were studied as environmentally benign initiating systems for cationic polymerization of isobutyl vinyl ether (IBVE). The reactivity of the benzyl cations could be effectively controlled by using dimethyl sulfide (Me₂S) as an additive, which was shown to be an effective Lewis base (LB), and diethyl ether as a reaction solvent. Detailed study of various benzyl cations and the order of addition of the reagents revealed that the reaction was controlled by the electronic and steric features of aryl(alkyl) halides, LBs, and IBVE, and a plausible reaction mechanism was presented. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2050–2058