Preparation of hierarchically structured PCL superhydrophobic membrane via alternate electrospinning/electrospraying techniques

Superhydrophobic polycaprolactone (PCL) membranes with hierarchical structure were fabricated via alternate electrospinning/electrospraying techniques. Electrospun PCL/methyl silicone oil (PCL/MSO) nanofibers were employed as substrate. PCL/MSO‐PCL microspheres (PCL/MSO‐PCL_MS) hierarchical membrane was prepared via electrosprayed PCL_MS as an additional layer on the substrate. Field emission scanning electron microscopy images showed the formation of hierarchical PCL/MSO‐PCL_MS membranes. Compared to pure PCL fibers substrate (120 ± 1.3°), the water contact angle (WCA) of MSO‐modified PCL membrane was 142 ± 0.7°. The most interesting observation was that the WCA of PCL_MS without any modification could be achieved to 146 ± 2.8°. On this basis, PCL/MSO‐PCL_MS hierarchical membrane possessed superhydrophobic surface with 150 ± 0.6° of WCA. The excellent surface roughness and air‐pocket capacity of hierarchical membranes would make the membranes more hydrophobic. The maximum oil (n‐hexane) adsorption capacity of PCL/MSO‐PCL_MS membrane was 32.53 g g^?1. Oil–water separation efficiencies of the superhydrophobic membranes were all higher than 99.93% after 10 cycles. The hierarchically structured PCL superhydrophobic membranes indicate the potential applications of environmentally friendly biopolymers as separation membranes. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 421–430     

Synthesis and characterization of hyperbranched amphiphilic block copolymers prepared via self‐condensing RAFT polymerization

Four families of hyperbranched amphiphilic block copolymers of styrene (Sty, less polar monomer) and 2‐vinylpyridine (2VPy, one of the two more polar monomers) or 4‐vinylpyridine (4VPy, the other polar monomer) were prepared via self‐condensing vinyl reversible addition‐fragmentation chain transfer polymerization (SCVP‐RAFT). Two families contained 4VPy as the more polar monomer, one of which possessing a Sty‐b‐4VPy architecture, and the other possessing the reverse block architecture. The other two families bore 2VPy as the more polar monomer and had either a 2VPy‐b‐Sty or a Sty‐b‐2VPy architecture. Characterization of the hyperbranched block copolymers in terms of their molecular weights and compositions indicated better control when the VPy monomers were polymerized first. Control over the molecular weights of the hyperbranched copolymers was also confirmed with the aminolysis of the dithioester moiety at the branching points to produce linear polymers with number‐average molecular weights slightly greater than the theoretically expected ones, due to recombination of the resulting thiol‐terminated linear polymers. The amphiphilicity of the hyperbranched copolymers led to their self‐assembly in selective solvents, which was probed using atomic force microscopy and dynamic light scattering, which indicated the formation of large spherical micelles of uniform diameter. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1310–1319     

Structure controlling and adsorption application of polyethersulfone porous microspheres prepared via electrospraying

The focus of this work is to control the structure of electrosprayed polymer microspheres and then study the effect of different structures on the microspheres＇ adsorption properties. Scanning electron microscopy （SEM） coupled with image analysis software was employed to evaluate the size distributions and the structure of microspheres. According to the observation and analysis results, two types of polyethersulfone （PES） porous microspheres （perfect sphere-shaped and collapsed） were prepared via electrospraying technology by adjusting the solvent and polymer molecular weight. The porous PES microspheres can remove bisphenol A （BPA） from its aqueous solution effectively. Compared with collapsed microspheres, the rough microspheres had much higher specific surface area and better mobility in the BPA aqueous solution, so it showed a better adsorption capacity than that of collapsed microspheres. The solvent evaporation rate and the occurrence rate of phase separation significantly affect the structure and morphology of microspheres.     

Surface patterned graft copolymerization of hydrophilic monomers onto hydrophobic polymer film upon UV irradiation

A random copolymer [p(MMA/DMAB)] composed of methyl methacrylate (MMA) and 2,2‐dimethoxy‐1,2‐di(4‐methacryloyloxy)phenylethane‐1‐one (DMAB), which can simultaneously act as a photoradical initiator and crosslinkable monomer, was prepared by free radical random copolymerization. A hydrophobic film on quartz glass was prepared using p(MMA/DMAB) by a spin‐coating technique. Hydrophilic methacrylic acid (MA) and 2‐methacryloyloxyethyl phosphorylcholine (MPC) were graft‐copolymerized from the hydrophobic p(MMA/DMAB) film in water by photo‐cleavage of the DMAB unit. The graft copolymer of MA and MPC was characterized by infrared and X‐ray photoelectron spectroscopies and contact angle measurements. To confirm that MPC can be grafted onto the surface of the film selectively at only UV‐irradiated sites, photoinduced graft copolymerization of MPC using a photomask was performed to prepare a pMPC patterned p(MMA/DMAB) film. The film was stained using a rhodamine 6G dye that can absorb specifically to pMPC to confirm the pMPC pattern. The p(MMA/DMAB) film can be applied to various fields including photolithography and biomedical applications, because the film surface properties can be controlled using various vinyl monomers selectively on UV‐irradiated sites. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2822–2829     

Neutral hydrophilic coatings for capillary electrophoresis prepared by controlled radical polymerization

In the present study, porous silica particles as well as impervious fused-silica wafers and capillary tubes were modified with hydrophilic polymers (hydroxylated polyacrylamides and polyacrylates), using a surface-confined grafting procedure based on atom transfer radical polymerization (ATRP) which was also surface-initiated from α-bromoisobutyryl groups. Initiator immobilization was achieved by hydrosilylation of allyl alcohol on hydride silica followed by esterification of the resulting propanol-bonded surface with α-bromoisobutyryl bromide. Elemental analysis, IR and NMR spectroscopies on silica micro-particles, atomic force microscopy, ellipsometry and profilometry on fused-silica wafers, as well as CE on fused-silica tubes were used to characterize the chemically modified silica substrate at different stages. We studied the effect of monomer concentration as well as cross-linker on the ability of the polymer film to reduce electroosmosis and to prevent protein adsorption (i. e., its non-fouling capabilities) and found that the former was rather insensitive to both parameters. Surface deactivation towards adsorption was somewhat more susceptible to monomer concentration and appeared also to be favored by a low concentration of the cross-linker. The results show that hydrophilic polyacrylamide and polyacrylate coatings of controlled thickness can be prepared by ATRP under very mild polymerization conditions (aqueous solvent, room temperature and short reaction times) and that the coated capillary tubes exhibit high efficiencies for protein separations (0.3–0.6 million theoretical plates per meter) as well as long-term hydrolytic stability under the inherently harsh conditions of capillary isoelectric focusing. Additionally, there was no adsorption of lysozyme on the coated surface as indicated by a complete recovery of the basic enzyme. Furthermore, since polymerization is confined to the inner capillary surface, simple precautions (e.g., solution filtration) during the surface modification process are sufficient to prevent capillary clogging.     

Synthesis of amphiphilic linear‐hyperbranched graft‐copolymers via grafting based on linear polyethylene backbone

The synthesis of amphiphilic linear‐hyperbranched graft‐copolymers in a grafting‐from approach is reported. The linear polyethylene with terminated hydroxyls, prepared by copolymerization of ethylene and 10‐undecen‐1‐ol, was used as macroinitiator for ring‐opening multibranching polymerization of glycidol by a typical slow monomer addition approach. Successful attachment of the hyperbranched grafts to the linear polyethylene backbone was confirmed by ¹H/¹³C NMR, GPC, and TGA. The degree of polymerization and M_w/M_n of hyperbranched grafts were efficiently controlled by temperature, deprotonation ratio as well as the molar ratio of glycidol/hydroxyl (N_glycidol/N_OH). The complicated microstructures caused by unsymmetric glycidol structure were analyzed by DEPT and 2D HSQC spectra, the degree of branching of 0.63–0.66 were calculated, indicating the extent of branch is close to theoretical values. The thermal analysis of linear‐hyperbranched copolymers via TGA and DSC is also presented. To our knowledge, this is the first report of a linear‐hyperbranched graft‐copolymer with a crystalline and nonpolar linear‐polyethylene segment. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2146–2154     

Poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) Modification via Organocatalyzed Atom Transfer Radical Polymerization

To address the challenge of metal contamination, a “graft from” approach via organocatalyzed atom transfer radical polymerization (O‐ATRP) is developed to synthesize poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) (P(VDF‐co‐CTFE)) graft copolymers. N‐phenylphenothiazine is utilized as a model organic photoredox catalyst for catalyzing the (co)polymerization of methyl methacrylate (MMA), methacrylate (MA), and n‐butyl acrylate (BA). By employing this technique, high temporal control of polymerization and graft content are achieved. A series of P(VDF‐co‐CTFE)‐g‐PMMA, P(VDF‐co‐CTFE)‐g‐PMA, and P(VDF‐co‐CTFE)‐g‐PBA is prepared under mild conditions. The resultant graft copolymer can be used as macroinitiator to re‐initiate O‐ATRP to synthesize P(VDF‐co‐CTFE)‐g‐(PMMA‐b‐PMA), which might exhibit the potential application as novel dielectric material.     

Adsorption of As(III) from aqueous solution based on porous magnetic/chitosan/ferric hydroxide microspheres prepared via electrospraying

Porous chitosan(CS)/magnetic(Fe3O4 )/ferric hydroxide(Fe(OH)3 ) microsphere as novel and low-cost adsorbents for the removal of As(Ⅲ) have been synthesized via the electrospraying technology by a simple process of two steps. Characterization of the obtained adsorbents was studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The adsorption kinetics and equilibrium isotherms were investigated in batch experiments. The Langmuir, Freundlich isotherm and pseudo-second order kinetic models agree well with the experimental data. The adsorption of As(Ⅲ) onto CS/Fe3O4 /Fe(OH)3 microspheres occurred rapidly and reached adsorption equilibrium after about 45 min. The maximum adsorption capacity of CS/Fe3O4 /Fe(OH)3 microspheres, calculated by the Langmuir isotherm model, was 8.47 mg g-1 , which is higher than that of CS/Fe3O4 /Fe(OH) 3 prepared by the conventional method (4.72 mg g-1 ). The results showed that the microspheres had a high adsorption capacity for As(Ⅲ) and a high separation efficiency due to their microporous structure and superparamagnetic characteristics. Present research may eventually lead to a simple and low cost method for fabricating microporous materials and application for removal of arsenic from aqueous solution.     

Amphiphilic and hydrophobic surface patterns generated from hyperbranched fluoropolymer/linear polymer networks: Minimally adhesive coatings via the crosslinking of hyperbranched fluoropolymers

Hyperbranched fluoropolymers (HBFPs), based on benzyl ether linkages and having a large number of pentafluorophenyl chain ends, were crosslinked by a reaction with diamino-terminated poly(ethylene glycol) (PEG) or diamino-terminated poly(dimethyl siloxane) (PDMS) to form hyperbranched–linear copolymer networks of different compositions, structures, and properties. The crosslinking reactions involved the nucleophilic aromatic substitution of the pentafluorophenyl para-fluorines of HBFP by the amine functionalities of the respective telechelic linear segments. The contact angles, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, and atomic force microscopy (AFM) were used to characterize the resulting network film samples. The surface wettability of the crosslinked materials was affected by the nature and amount of the linear polymer crosslinking agent employed. Amphiphilic polymer networks were formed by the incorporation of diamino-terminated PEG as a crosslinker, whereas diamino-terminated PDMS produced polymer networks of a hydrophobic character. The mechanical properties improved upon crosslinking, as measured by tensile testing. The mechanical integrity of the films was also found to improve upon crosslinking, as measured by AFM machining protocols. The AFM images revealed topographical morphologies that appeared to be the result of phase segregation of HBFP from PEG or PDMS; the dimensions of the phase-segregated domains were dependent on the stoichiometry of HBFP to the linear polymer and the thickness of the coating. As the content of PEG increased, fouling by human fibrinogen, used as a model protein, decreased. Further studies are in progress to determine the effects of the surface composition, morphology, and topography on the biofouling characteristics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3531–3540, 2003     

Synthesis of hybrid dendritic‐linear block copolymers with dendritic initiators prepared by convergent living anionic polymerization

Hybrid dendritic‐linear block copolymers were made in one‐pot by convergent living anionic polymerization. Dendritic polystyrene macroinitiators were synthesized by slowly adding a mixture of either vinylbenzyl chloride (VBC) or 4‐(chlorodimethylsilyl)styrene (CDMSS) and styrene (1 : 10 molar ratio of coupling agent to styrene) to a solution of living polystyryllithium. The addition was ceased prior to the addition of a stoichiometric amount of coupling agent to retain a living chain end. To the living dendritically branched polystyrene was then added either styrene or isoprene to polymerize a linear block from the dendritic polystyrene. The resulting copolymers were characterized by gel permeation chromatography coupled with multiangle laser light scattering (GPC‐MALLS), which clearly demonstrated the formation of diblock copolymers. The diblock copolymers were further characterized by ¹H NMR, which showed the presence of the two blocks in the case of dendritic polystyrene‐block‐linear polyisoprene. The measurement of intrinsic viscosity showed that the dilute solution properties of the block copolymers are greatly influenced by the dendritic portion. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 152–161, 2001     

Graft copolymers from star‐shaped and hyperbranched polystyrene macromonomers

Branched polystyrene macromonomers were synthesized by the slow addition of a stoichiometric amount of either 4‐(chlorodimethylsilyl)styrene or vinylbenzyl chloride as a coupling agent to living polystyryllithium. Star‐shaped macromonomers were produced by the addition of the coupling agent alone, and hyperbranched macromonomers resulted from the addition of the coupling agent along with styrene monomer. Star and hyperbranched graft copolymers were produced by the copolymerization of the macromonomers with styrene and methyl methacrylate. The copolymers were characterized by gel permeation chromatography coupled with multi‐angle laser light scattering, ¹H NMR spectroscopy, and Soxhlet extraction to determine that the macromonomers were incorporated in high yields into the copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3547–3555, 2001     

SEC‐MALDI‐TOF mass spectral characterization of a hyperbranched polyether prepared via melt transetherification

An AB₂ monomer, 1‐(2‐hydroxyethoxy)‐3,5‐bis‐(methoxymethyl)‐2,4,6‐trimethylbenzene, was synthesized from mesitol and melt‐polycondensed in the presence of an acid catalyst via a transetherification process at 145–150 °C to yield a soluble, moderately high molecular weight hyperbranched polyether. The degree of branching in the polymer was calculated to be 0.78 by a comparison of its NMR spectrum with that of an appropriately designed model compound. The weight‐average molecular weight of the hyperbranched polymer was determined to be 64,600 (weight‐average molecular weight/number‐average molecular weight = 5.2) by size exclusion chromatography (SEC) in CHCl₃ with polystyrene standards. The origin of the broad molecular weight distribution, which could either be intrinsic to such hyperbranched structures or be due to structural heterogeneity, was further probed by the fractionation of the samples by SEC and by the subjection of each fraction to matrix‐assisted laser desorption/ionization time‐of‐flight mass spectral analysis. The mass spectral analysis suggested the presence of two primary types of species: one corresponding to the simple branched structure and the other to macrocyclics. Interestingly, from the relative intensities of the two peaks, it was apparent that cyclization became favorable at higher conversions in the melt transetherification process. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4463–4476, 2002     

Visible light-induced synthesis of polysulfone-based graft copolymers by a grafting from approach

The synthesis of polysulfone (PSU) graft copolymers by a two-step “grafting from” approach is described. First, a chlorofunctional PSU (PSU-Cl) is formed via chloromethylation of a commercial PSU. The formed polymers are used macroinitiator for the dimanganese decacarbonyl assisted free-radical polymerization of tert-butyl acrylate, methyl methacrylate, and styrene to give the desired graft copolymers. Moreover, amphiphilic graft copolymers are also formed via posthydrolyzation of poly(tert-butyl acrylate) containing graft copolymers. The intermediates at various stages and the ultimate graft copolymers are characterized by various analysis techniques. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 412–416     

Star and Hyperbranched Polyisobutylenes via Terminally Reactive Polyisobutylene-Polystyrene Block Copolymers

Unique, highly branched polyisobutylenes (PIB) were prepared via quasiliving carbocationic copolymerization of isobutylene and styrene (St) monomers. The junction points were formed by Friedel-Crafts self alkylation of PSt segments by the carbocationic chain ends. First, linear PIB was prepared with reactive chain ends. This was reacted with St monomer to form PIB-b-PSt AB, and PSt-b-PIB-b-PSt ABA type triblock copolymers with reactive carbocationic chain ends. The terminal carbonations react with the phenyl group of the polystyrene end-segments of the block copolymers leading to chain coupling, and thus PIB star polymers in the case of AB and hyperbranched PIB from ABA block copolymers. The resulting branched polymers were characterized and the branch formation was confirmed by gel permeation chromatography (GPC) and proton nuclear magnetic resonance spectroscopy (¹H NMR).     

Nanofibers prepared by electrospinning from solutions of biobased polyamide 4

A successful preparation of polyamide 4 nanofibers via electrostatic spinning with diameters close to 100 nm is described. Polyamide 4 was prepared by the anionic ring‐opening polymerization of 2‐pyrrolidone and characterized. The effect of the system parameters (i.e., molar mass of the polymer, the solvent system) and the process parameters (i.e., the electrode‐to‐collector distance) during the electrostatic spinning have been studied. The morphology of the polyamide 4 fiber layers is given except molar mass of the polymer and the concentration of its solution primarily by the conformation of polyamide chains due to polyelectrolyte effect which was confirmed by viscosity measurements. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2203–2210     

Facile preparation of core‐crosslinked micelles from azide‐containing thermoresponsive double hydrophilic diblock copolymer via click chemistry

Double hydrophilic diblock copolymer, poly(N,N‐dimethylacrylamide)‐b‐poly(N‐isopropylacrylamide‐co‐3‐azidopropylacrylamide) (PDMA‐b‐P(NIPAM‐co‐AzPAM), containing azide moieties in one of the blocks was synthesized via consecutive reversible addition‐fragmentation chain transfer polymerization. The obtained diblock copolymer molecularly dissolves in aqueous solution at room temperature, and can further supramolecularly self‐assemble into core‐shell nanoparticles consisting of thermoresponsive P(NIPAM‐co‐AzPAM) cores and water‐soluble PDMA coronas above the lower critical solution temperature of P(NIPAM‐co‐AzPAM) block. As the micelle cores contain reactive azide residues, core crosslinking can be facilely achieved upon addition of difunctional propargyl ether via click chemistry. In an alternate approach in which the PDMA‐b‐P(NIPAM‐co‐AzPAM) diblock copolymer was dissolved in a common organic solvent (DMF), the core‐crosslinked (CCL) micelles can be fabricated via “click” crosslinking upon addition of propargyl ether and subsequent dialysis against water. CCL micelles prepared by the latter approach typically possess larger sizes and broader size distributions, compared with that obtained by the former one. In both cases, the obtained (CCL) micelles possess thermoresponsive cores, and the swelling/shrinking of which can be finely tuned with temperature, rendering them as excellent candidates as intelligent drug nanocarriers. Because of the high efficiency and quite mild conditions of click reactions, we expect that this strategy can be generalized for the structural fixation of other self‐assembled nanostructures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 860–871, 2008     

Hierarchical structure microspheres of PCL block copolymers via electrospraying as coatings for fabric with mechanical durability and self‐cleaning ability

The various morphology and structure microspheres were fabricated via one‐step single‐solvent electrospraying of hydrophilic and hydrophobic block modified copolymer of polycaprolactone (PCL). A honeycomb‐like hierarchical structure microspheres of PCL‐b‐PTFOA(4h) and abundant nanometer pores of PCL‐b‐PEG400 microspheres were obtained due to the solvent evaporation, thermally and polymer diffusion‐induced phase separation effect. Furthermore, a superhydrophobic coatings and robust superhydrophobic‐coated cotton woven fabric surfaces were prepared by using PCL‐b‐PTFOA(4h) microspheres with hierarchical structure and low surface energy. The contact angle (CA) and sliding angle (SA) of PCL‐b‐PTFOA(4h) microspheres‐coated cotton woven fabric surfaces reached 164.4 ± 5.5° and 6.8 ± 0.5°, respectively, which allows for self‐cleaning. The self‐cleaning test demonstrated that the coated superhydrophobic surface could shed aqueous dyes and dust without any trace. The superhydrophobic‐coated fabric shows good soaping fastness against mechanical abrasion without significant reduction of CA. This electrospraying coating of block copolymers can provide a simple, facile, and promising technique for producing multifunctional textiles.     

Polyelectrolyte complex nanoparticles from N‐carboxyethylchitosan and polycationic double hydrophilic diblock copolymers

For the first time, the polyelectrolyte complex (PEC) formation tool was used for preparation of core‐shell nanoparticles form the natural polyampholyte N‐carboxyethylchitosan (CECh) and weak polycationic (protonated) polyoxyethylene‐b‐poly[2‐(dimethyl‐amino)ethyl methacrylate] (POE‐b‐PDMAEMA) diblock copolymers. The performed dynamic light scattering analyses revealed that nanoparticles with a PEC core and a POE shell could be formed at mixing ratio between the oppositely charged groups equal to 1/1 depending on CECh molar mass, polymerization degree of PDMAEMA block and ionic strength. The results were confirmed by the performed AFM and cryo‐TEM analyses. When high molar mass CECh was used, core‐shell nanoparticles were obtained with the diblock copolymer of the shortest PDMAEMA block at ionic strength (I) of 0.01. At ionic strength value close to the physiological one (I = 0.1) secondary aggregation occurred. Spherical nanoparticles at I = 0.1 were obtained upon lowering the CECh molar mass. Depending on the polymer partners and medium parameters the size of the obtained particles varied from 60 to 600 nm. The X‐ray photoelectron spectra evidenced the hydrophilic POE‐block shell—coacervate CECh/PDMAEMA‐block core structure. The nanoparticles are stable in a rather narrow pH range around 7.0, thus revealing the high pH‐sensitivity of the obtained core‐shell particles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2105–2117, 2009