Effect of the structure of titanium–magnesium catalysts on the morphology of polyethylene produced

The structure and formation of polyethylene (PE) particles on supported titanium–magnesium catalysts having different structural characteristics (sizes of microcrystallites, mesopores, and subparticles) were studied for the first time. Scanning electron microscopy was used to identify structural elements of the polymer particles formed over such catalysts and to reveal morphological changes in the growing polymer particles when the yield was increased from approximately 0.2 g PE/g catalyst to approximately 13 kg PE/g catalyst. A relationship was found between structural characteristics of the porous catalyst particles, morphology of the nascent polymer particles, and bulk density of the polymer powder. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2298–2308     

Tuning the conformation of synthetic co‐polypeptides of serine and glutamic acid through control over polymer composition

Ring opening polymerization (ROP) of N‐carboxy anhydride (NCA) amino acids presents a rapid way to synthesize high molecular weight polypeptides with different amino acid compositions. The compositional and functional versatility of polypeptides make these materials an attractive choice for biomaterials. The functional performance of polypeptide materials is equally linked to their conformation which is determined by the amino acid sequence in the polymer chains. Here, the interplay between composition and conformation of synthetic polypeptides obtained by NCA polymerization was explored. Various copolypeptides from Glu(Bzl) and Ser(Bzl) were prepared to investigate how polypeptide composition affected the conformation of the resulting copolymer. Polymerization kinetics indicated that the copolymerization of Glu(Bzl) and Ser(Bzl) preferentially yielded alternating copolymers. Both the polydispersity and the conformation of the polypeptides were dependent on the Ser(Bzl) content in the polymer, demonstrating that polypeptide functionalities could be tuned directly by altering the relative amounts of amino acids in the chain. This work presents the first step toward an improved understanding and control over polypeptide conformation through modulating the amino acid composition of the material. Understanding this sequence–functionality relationship is essential to advancing the use of ROP as a technique to design smart polypeptide based materials with specific functions. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2331–2336     

Semicontinuous heterophase copolymerization of styrene and acrylonitrile

The synthesis of styrene‐acrylonitrile copolymers by semicontinuous heterophase polymerization is reported here. The effect of feed composition at a fixed addition rate of monomer mixture on kinetics, particle size, polymer content, and molar masses, was studied. This process permits the synthesis of nanolatexes containing narrow size‐distribution particles with number‐average diameter (D_n) of about 18 nm, polymer content as high as 23 wt %, and copolymer‐to‐surfactant weight ratios between 23 and 25, depending on monomer feeding rate, which are larger than those reported for microemulsion copolymerization of several comonomers. Copolymers with homogeneous composition similar to the feeding monomers composition were obtained thorough the reaction, which is difficult to achieve by batch polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of conducting poly(aniline‐co‐o‐aminophenethyl alcohol)s

Poly(o‐aminophenethyl alcohol) and its copolymers containing the aniline unit were synthesized in aqueous hydrochloric acid medium by chemical oxidative polymerization. The chemical composition of these novel polymers was determined spectroscopically, and their viscosities were measured. These polymers exhibit good solubility in organic solvents that is attributed mainly to the polar hydroxyethyl side groups. Their structures (chain conformation and morphological structure) and properties (conductivity, electrochemical characteristics, glass transition, and degradation behavior) were characterized and then interpreted on the basis of the chemical composition along with the electronic and steric hindrance effects associated with the hydroxyethyl side group. Overall, the side group has a significant effect on the polymerization and influences the structure, chain conformation, and properties of the resultant polymer. The poly(aniline‐co‐o‐aminophenethyl alcohol)s containing 20–40 mol % o‐aminophenethyl alcohol units are potential conducting materials for microelectronic and electromagnetic shielding applications because they are easier to process than polyaniline but retain its beneficial properties. These polymers can also be used as a functional conducting polymer intermediate owing to the reactivity of the side group. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 983–994, 2002     

Noncontinuum effects on the mobility of nanoparticles in unentangled polymer solutions

The results for the diffusivity of nanoparticles in unentangled semidilute polymer solutions obtained using coarse‐grained simulations are presented. The results indicate that for particle sizes smaller than the polymer radius of gyration, the nanoparticle diffusivities deviate from Stokes–Einstein predictions and depend explicitly on the polymer radius of gyration and the polymer solution correlation lengths. Scaling ideas proposed are invoked for rationalizing such noncontinuum effects and demonstrate that the simulation results could be collapsed onto a single universal function of the depletion thickness, the polymer radius of gyration, and the particle radius. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2145–2150.     

Synthesis of polymeric nanocapsules by radical UV‐activated interface‐emulsion polymerization

A new methodology is reported that allows a better control of the synthesis of polymeric core–shell nanocapsules. These nanocapsules were made of biocompatible polymers, obtained from poly(ethylene glycol)diacrylate and poly(ethylene glycol) methyl ether methacrylate, and were used as carrier for curcumin as therapeutic agent. The impact of manufacturing factors (time of sonication, time of UV irradiation, and type of monomer) was investigated in relation to the average size of nanocapsules, their distribution, shape, composition, stability, and their capability to deliver curcumin. We successfully synthesized core–shell nanocapsules in various sizes, ranging from 80 nm to 300 nm, by acting either on the process conditions or on the composition of the monomer mixture. This wide range of sizes makes the method here proposed very promising for the production of nanocarriers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3357–3369     

Propylene polymerization reactions with supported Ziegler–Natta catalysts: Observing polymer material produced by a single active center

Medium‐ and high‐resolution SEM analysis of several Ti‐based MgCl₂‐supported Ziegler–Natta catalysts and isotactic polypropylene produced with them is carried out. Each catalyst particle, 35–55 μ in size, produces one polymer particle with an average size of 1.5–2 mm, which replicates the shape of the catalyst particle. Polymer particles contain two distinct morphological features. The larger of them are globules with D_av ～400 nm; from 1 to 2 × 10¹¹ globules per particle. Each globule represents the combined polymer output of a single active center. The globules consist of ～2500 microglobules with an average size of ～20 nm. The microglobules contain several folded polymer molecules; they are the smallest thermodynamically stable macromolecular ensembles in propylene polymerization reactions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3832–3841     

Influence of the particle size of the MgCl2 support on the performance of Ziegler catalysts in the polymerization of ethylene to ultra‐high molecular weight polyethylene and the resulting polymer properties

A highly systematic size series of Ziegler catalysts with similar porosities and surface textures are synthesized by varying the stirring speed during the MgCl₂ support synthesis. Besides the mean particle size, the only substantial difference observed between the various catalysts is the size and number of nodules per particle. Varying the mean diameter of the catalyst particles between 1.5 and 11.9 µm, leads to a pronounced impact on the activity in ultra‐high molecular weight polyethylene (UHMWPE) polymerization, while the M_w capabilities are only affected to a limited extend. In addition, it is observed that both the M_ws as the polymer bulk density (BD) increases during the course of the polymerization. This particularity allows to optimize the M_w and/or BD at a set polymer size, by tuning the catalyst particle size. This is particularly interesting in UHMWPE production, as control of the morphological and structural properties of the UHMWPE reactor powders are critical for efficient processing as well as the performance of the final product. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2679–2690     

Synthesis of polyethers with unsymmetrical structures by the polyaddition of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane with diacyl chlorides

Polyethers with unsymmetrical structures in the main chains and pendant chloromethyl groups were synthesized by the polyaddition of 3‐ethyl‐3‐(glycidyloxymethyl)oxetane (EGMO) with certain diacyl chlorides with quaternary onium salts or pyridine as catalysts. The unsymmetrical polyaddition of EGMO containing two different cyclic ether moieties such as oxirane and oxetane groups with terephthaloyl chloride proceeded smoothly in toluene at 90 °C for 6 h to give polymer 1 with a number‐average molecular weight (M_n) of 51,700 in a 93% yield when tetrabutylammonium bromide (TBAB) was used as a catalyst. The polyaddition also proceeded smoothly under the same conditions when other quaternary onium salts, such as tetrabutylammonium chloride, tetrabutylammonium iodide, tetrabutylphosphonium chloride, and tetrabutylphosphonium bromide, and pyridine were used as catalysts. However, without a catalyst no reaction occurred under the same reaction conditions. Polyadditions of EGMO with isophthaloyl chloride and adipoyl chloride gave polymer 2 (M_n = 28,700) and polymer 3 (M_n = 25,400) in 99 and 65% yields, respectively, under the same conditions. The chemical modification of the resulting polymer, polymer 1 , which contained reactive pendant chloromethyl groups, was also attempted with potassium 3‐phenyl‐2,5‐norbornadiene‐2‐carboxylate with TBAB as a phase‐transfer catalyst, and a polymer with 65 mol % pendant norbornadiene moieties was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 368–375, 2001     

Preparation of non‐spherical particles from amphiphilic block copolymers

Simple self‐assembly techniques to fabricate non‐spherical polymer particles, where surface composition and shape can be tuned through temperature and the choice of non‐solvents was developed. A series of amphiphilic polystyrene‐b‐poly(2‐ethyl‐2‐oxazoline) block copolymers were prepared and through solvent exchange techniques using varying non‐solvent composition a range of non‐spherical particles were formed. Faceted phase separated particles approximately 300 nm in diameter were obtained when self‐assembled from tetrahydrofuran (THF) into water compared with unique large multivesicular particles of 1200 nm size being obtained when assembled from THF into ethanol (EtOH). A range of intermediate structures were also prepared from a three part solvent system THF/water/EtOH. These techniques present new tools to engineer the self‐assembly of non‐spherical polymer particles. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 750–757     

Efficient fabrication of polymer nanoparticles via sonogashira cross‐linking of linear polymers in dilute solution

The synthesis of single‐chain nanoparticles by palladium‐catalyzed Sonogashira coupling between a terminal alkyne and a di‐halo aryl cross‐linker is reported. Statistical copolymers with trimethylsilyl protected alkyne groups pendent to the linear methacrylate back bones were synthesized using reversible addition‐fragmentation chain transfer polymerization post polymerization de‐protection providing terminal alkyne functionalized linear polymer chains. These linear polymer chains were intramolecularly cross‐linked via bifunctional cross‐linkers. The resulting well‐defined covalently bonded nanoparticles were characterized via triple‐detection size exclusion chromatography where MALS detector provided molecular weight information and viscometric detection characterizes particle size and conformations. The particle size could be readily tuned through polymer molecular weight and by degree of cross‐linking. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 209–217     

Chitosan/Ce(IV) redox polymerization‐based amplification for detection of DNA point mutation

Polymerization‐based signal amplification, a technique developed for use in rapid diagnostic tests, hinges on the ability to localize initiators as a function of interfacial binding events. We report here a new DNA detection method in which polymer growth in redox‐polymerization is used as a means to amplify detection signals. The introduction of biotin‐labeled chitosan (biotin‐CS) with highly dense amino groups into the polymerization amplification as macromolecular reducing agent, beneficially simplifies amplification operation, as well as, provides a large amount of initiation points to improve the sensitivity of detection. DNA hybridization, SA and biotin binding reactions led to the attachment of CS on a solid surface where specific DNA sequences were located. With the addition of the mixture containing monomer AM, crosslinker PEGDA and oxidant CAN onto the CS location, the growth of polymer films was triggered to render the corresponding spots readily distinguishable to the naked eye. Direct visualization of 0.21 fmol target DNA molecules of interest was demonstrated. Non‐small cell lung cancer p53 sequence was further selected as a proof‐of‐principle to detect DNA point mutation. The proposed method exhibited an efficient amplification performance for molecule detection, and paved a new way for visual diagnosis of biomolecules. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1929–1937     

Surface and interfacial segregation of polyethersulfone deuterated chain ends determined by neutron reflectivity

The surface localization of polymer chain ends has been shown to be an effective method for surface composition control in amorphous polymer films. This work determines chain end distribution in thin polyethersulfone (PESU) films end‐capped with deuterated compounds of varying size and composition. Neutron reflectivity revealed the preferential localization of chain ends to the PESU‐air interface, independent of chain end identity. The length scale of the chain end concentration gradient was determined to differ from that predicted for flexible chain polymers. Atomic force microscopy and contact angle analysis demonstrated that chain end localization allows for improved control of nanoscale and macroscale surface properties of PESU films. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 293–301     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1?xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1−xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.     

Development of solution‐dispersible hyperbranched conjugated polymer nanoparticles for Fe3+ fluorescent detection and their application in logic gate

Solution‐dispersible hyperbranched conjugated polymer nanoparticles (FT‐HBCPNs) consist of an intrinsic crosslinked rigid skeleton structure of both 9,9‐dihexyl‐fluorene and triphenylamine repeating units, and are synthesized via the miniemulsion Suzuki polymerization, and FT‐HBCPNs for highly selective and sensitive Fe³⁺ fluorescent detection and their application in logic gate at molecular level are successfully developed. FT‐HBCPNs with an average particle size of 10.6 nm can disperse in common organic solvents. FT‐HBCPNs show high selectivity and sensitivity for Fe³⁺ over other commonly co‐existent metal ions in THF solution with a detection limit of 3.65 × 10^?8 mol L^?1. Furthermore, homogeneous transparent thin films of FT‐HBCPNs developed by a simple spin‐coating method can be reversibly quenched by Fe³⁺ with a detection limit of 3.09 × 10^?7 mol L^?1. Using Fe³⁺ and EDTA as chemical inputs and the fluorescence intensity signal as outputs, FT‐HBCPNs films can be utilized as a logic gate at molecular level. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3694–3700     

Filler size effects on the conductivity of polymer nanocomposites: Semiconductive phthalocyanine nanoparticles in epoxy matrices

Three Cobalt(III) phthalocyanine (Phthalcon) powders with different particle sizes and chemical compositions, but almost equal XRD spectra and powder conductivity were synthesized and used as conductive fillers in crosslinked epoxy matrices. Two of these Phthalcons are new compounds. The relation between the conductivity of the composites and the type and amount of filler used was determined. The influence of particle size and chemical composition on this relation appeared to be minimal. These composites had a percolation threshold of 0.9 vol % and a maximum volume conductivity of 10^?7 S/cm. Detailed analysis showed that the particle networks have very similar fractal structures and that they are likely to be formed by diffusion limited cluster‐cluster aggregation during processing. Evidence is presented that these particle networks are formed at an early stage of crosslinking and that the charge transfer between particles in the networks is neither limited by the Phthalcon particle size, nor by the presence of polymer matrix between the particles. The maximum volume conductivity of these composites is likely to be limited by the amount of filler used, the crystal structure defects on the particle surface, and the fractality and the imperfection of the particle networks. The impact of these findings on the conductivity of other polymer nanocomposites is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1079–1093, 2008     

Monodisperse superparamagnetic pH‐sensitive single‐layer chitosan hollow microspheres with controllable structure

Facile strategy was developed for the fabrication of the monodisperse superparamagnetic pH‐sensitive single‐layer chitosan (CS) hollow microspheres with controllable structure. The carboxyl group‐functionalized polystyrene microspheres prepared by soap‐free emulsion polymerization were used as the templates. After the Fe₃O₄ nanoparticles were in situ formed onto the surface of the templates, the single‐layer CS was self‐assembled and cross‐linked with glutaraldehyde subsequently. Then, the magnetic single‐layer CS hollow microspheres were obtained after the templates were removed. It was found that the feeding ratio of the monomer acrylic acid in the soap‐free emulsion polymerization had played an important role on the particle size and surface carboxyl group content of the templates, which determined the particle size and shell thickness of the magnetic single‐layer CS hollow microspheres in the proposed strategy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis,characterization, and influence of synthesis parameters on particle sizes of a new microgel family

Poly(p‐nitrophenylacrylate‐co‐methacrylamide) and poly(p‐Nitrophenylacrylate‐co‐N,N′‐isopropylacrylamide) reactive microgels were synthesized by precipitation polymerization. The process was followed qualitatively by infrared spectroscopy (ATR‐FTIR) and microgels composition was determined by nuclear magnetic resonance (¹H NMR). Scanning electron microscopy of obtained colloidal particles showed strictly spherical morphologies with a moderate polydispersity. The average hydrodynamic particle diameter and particle size distributions were measured by quasi‐elastic light scattering and the particle size distributions obtained ranged from 100 to 600 nm. Several synthetic parameters affect the particle size of these materials and thus, indirectly, their properties and future applications. In this article, we report the influence of different polymerization reaction conditions in the final microgel dimensions. For example, we observed that the different solvent‐comonomer affinity induced a significant change in swollen particle size of the copolymeric microgels. On the other hand, the crosslinking density limited the particle sizes, but an excess of crosslinker content in the reaction mixture resulted in the opposite effect. Finally, we also studied the influence of initiator content in the mean particle size. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3833–3842, 2007     

Further insight into the mechanism of poly(styrene‐co‐methyl methacrylate) microsphere formation

Polymeric microspheres have been used in a broad range of applications from chromatographic separation techniques to analysis of air flow over aerodynamic surfaces. The preparation of microspheres from many polymer families has consequently been extensively studied using a variety of synthetic approaches. Although there are a myriad of polymeric microsphere synthesis methods, free‐radical initiated emulsion polymerization is one of the most common techniques. In this work, poly(styrene‐co‐methyl methacrylate) microspheres were synthesized via surfactant‐free emulsion polymerization. The effects of co‐monomer composition and addition time on particle size distribution, particle formation, and particle morphology were investigated. Particles were characterized using dynamic light scattering and scanning electron microscopy to gain further insight into particle size and size distributions. Reaction kinetics were analyzed through consideration of characterization results. A particle formation mechanism for poly(styrene‐co‐methyl methacrylate) microspheres was proposed based on characterization results and known reaction kinetics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2249–2259