Showing papers in "Macromolecular Rapid Communications in 2001"
TL;DR: In this article, the particular properties of soluble derivatives of polyfluorene homopolymers with respect to emission properties, control of color stability and efficiency in electroluminescence, alignment in thin layers and polarized emission are discussed.
Abstract: Since the first report on blue electroluminescence from a soluble poly(9,9-di-alkylfluorene), fluorene-based homo- and copolymers have evolved as a major class of polymeric emitters for highly efficient organic light-emitting diodes. This Review is concerned with the particular properties of soluble derivatives of polyfluorene homopolymers with respect to emission properties, control of color stability and efficiency in electroluminescence, alignment in thin layers and polarized emission. A major point of discussion is the origin of unwanted emission contributions in the photoluminescence and electroluminescence spectra of solid layers as well as concepts to avoid these contributions in order to ensure stable device performance. Further, the alignment of polyfluorenes and their use in polarized light-emitting diodes is addressed.
787 citations
TL;DR: Double-hydrophilic block copolymers are a new class of amphiphilic molecules of rapidly increasing importance with unique and fascinating properties connecting materials science, pharmacy, biochemistry and polymer science as mentioned in this paper.
Abstract: Double-hydrophilic block copolymers are a new class of amphiphilic molecules of rapidly increasing importance with unique and fascinating properties poten tially connecting materials science, pharmacy, biochemistry and polymer science. Characteristic of these polymers is their application in aqueous environments and that amphiphilicity is just induced in the presence of a subtrate or by temperature and pH changes, respectively, Their chemical structure may be turned for a wide range of applications covering as different aspects as stabilization of colloids, crystal growth modification, indnced micelle formation, polyelectrolyte complexing towards novel drug carrier systems. As the potential of this novel polymer class is relatively unexplored vet it can be expected that more applications will arise due to the possibility to adapt the chemical structure to either the desired substrate in contact with water or the stimulus for the induction of structural changes. This review describes the synthetic strategies to wards these AB block copolymers, as well as their applications.
556 citations
TL;DR: In this article, the main focus of the review is laid on a detailed description of the working principles of mini-emulsions, the examination of the kinetics during the polymerization process, and the generation of different particle structures by appropriate thermodynamic handling.
Abstract: The process of miniemulsification allows the generation of small, homogeneous, and stable droplets of monomer or polymer precursors, which are then transformed by (as many as possible) polymer reactions to the final polymer latexes, keeping their particular identity without serious exchange kinetics being involved The main focus of this Review is laid on a detailed description of the working principles of miniemulsions, the examination of the kinetics during the polymerization process, and the generation of different particle structures by appropriate thermodynamic handling It will be shown that the strength of miniemulsions is the formation of polymeric nanoparticles consisting of polymers or polymer structures, which are not accessible by other types of heterophase polymerization Non-radical polymerizations and the formation of hybrid materials by the encapsulation of resins, inorganic materials, or liquids are some examples showing the wide applicability of miniemulsions also for technologically relevant questions With the miniemulsification of molten inorganic materials followed by a reaction, miniemulsions cross the border of polymers and open new possibilities in the fabrication of solid particles for material science
436 citations
TL;DR: In this article, a pH-controlled encapsulation in and release of macromolecules from polyelectrolyte capsules of a few microns in diameter is demonstrated, where capsules were prepared via alternating adsorption of the oppositely charged polymers poly(allylamine hydrochloride) and poly(styrene sulfonate) onto decomposable melamin formaldehyde cores.
Abstract: pH-Controlled encapsulation in and release of macromolecules from polyelectrolyte capsules of a few microns in diameter is demonstrated. Capsules were prepared via alternating adsorption of the oppositely charged polymers poly(allylamine hydrochloride) and poly(styrene sulfonate) onto decomposable melamin formaldehyde cores. The capsules were open for macromolecules at pH values below 6 and closed at pH > 8.
413 citations
TL;DR: In this article, the thermal degradation behavior of poly(propylene)/organoclay, modified with protonated octadecyl amine (C18), was studied by thermogravimetry.
Abstract: The thermal degradation behaviour of nanocomposites based upon poly(propylene)/organoclay, modified with protonated octadecyl amine (C18) in comparison to that of non-exfoliated microcomposites based upon organoclay, modified with protonated butyl amine (C4), was studied by thermogravimetry. In the case of the nanocomposite, the temperature at which volatilisation occurs increases as compared of the microcomposite. Moreover, the thermal oxidation process of the polymer is strongly slowed down in the nanocomposite with high char yield both by a physical barrier effect, enhanced by ablative reassembling of the silicate, and by a chemical catalytic action due to the silicate and to the strongly acid sites created by thermal decomposition of the protonated amine silicate modifier.
353 citations
TL;DR: A detailed description of the experimental procedure, followed by an overview of the development, the success and the current challenges of this technique during the past five years, in which it has rapidly evolved from the first proof of principle to a highly active field of research as discussed by the authors.
Abstract: Recent progress in atomic force microscopy (AFM) technology has allowed the measurement of inter- and intramolecular forces at the level of individual molecules. The mechanical manipulation of single polymer chains immobilized on solid substrates has become possible in solution, as they are spanned and stretched between the tip of an AFM cantilever and the substrate surface. This investigation of polymer chains far from their maximum entropy configurations has stimulated the refinement of existing polymer theories. From the measured force-distance curves quantitative information can be obtained on the elasticity of single macromolecules in solution, on conformational transitions along the chains, about the mechanical stability of chemical bonds and on secondary structures, as well as on the desorption of individual polymer molecules from solid substrates. Recent applications of AFM single molecule force spectroscopy reach from the study of dynamic processes in complex biological systems and intermolecular forces in colloidal systems to the investigation of new functional materials capable of performing energy transductions on the level of individual macromolecules. In this article, we present a detailed description of the experimental procedure, followed by an overview of the development, the success and the current challenges of this technique during the past five years, in which it has rapidly evolved from the first proof of principle to a highly active field of research.
339 citations
TL;DR: In this paper, a poly(acrylic acid)/mica super absorbent composite was synthesized by graft polymerization reaction betwen partially neutralized acrylic acid and ultrafine mica mineral powder.
Abstract: A novel poly(acrylic acid)/mica super absorbent composite was synthesized by graft polymerization reaction betwen partially neutralized acrylic acid and ultrafine mica mineral powder. The water absorbency of the composite is higher than 1 100 g H2O/g. The influence of the neutralization degree of acrylic acid, as well as of the amounts of mica and crosslinker on the absorbing properties are discussed in this paper.
263 citations
TL;DR: In this article, the helix-property-functionality relationship between side chain structure, global and local main chain conformation, (chir)optical properties, electronic properties, several helical cooperative phenomena, the effects of temperature and solvent polarity, and molecular imaging is reviewed comprehensively.
Abstract: Controlled synthesis, chiroptical characterization, and manipulation of artificial helical polymers are challenging issues in modern polymer stereochemistry. Although many artificial polymers adopting a preferential screw-sense helical structure have been investigated, optically active polysilylenes bearing chiral side chains may be among the most suitable to elucidate the inherent nature of the helical structure, since these polymers offer powerful spectroscopic probes as a result of their ideal chromophoric and fluorophoric main chain properties around 300–330 nm. The present paper will review comprehensively the helix-property-functionality relationship between side chain structure, global and local main chain conformation, (chir)optical properties, electronic properties, several helical cooperative phenomena, the effects of temperature and solvent polarity, and molecular imaging. This knowledge and understanding of the nature of the polysilylene helix might constitute a bridge between artificial polymers and biopolymers and will assist in designing and controlling new types of helical polymers directed to diverse screw-sense-related properties and applications in the future.
231 citations
TL;DR: In this article, the BAB-type triblock copolymers composed of a central poly(ethyelene oxide) (PEO, M nPEO = 1000) block and two poly[(D,L-lactic acid)-co-(glycolic acid)] end blocks with molecular weights between 900 and 1 600 exhibited an intersting phase transition behavior.
Abstract: The BAB-type triblock copolymers composed of a central poly(ethyelene oxide) (PEO, M nPEO = 1000) block and two poly[(D,L-lactic acid)-co-(glycolic acid)] end blocks with molecular weights between 900 and 1 600 exhibited an intersting phase transition behavior. The copolymer aqueous solution can form micelles with PLGA loops in the core and a PEO shell and groups of micelles because of bridging between micelles caused by the PLGA blocks with raising temperature. A possible micellar gelation mechanism was suggested.
217 citations
TL;DR: The use of hydrogen bonding for the design of functional liquid crystalline materials has been shown to be a versatile approach toward the control of simple molecularly assembled structures and the induction of dynamic function.
Abstract: Liquid crystals are molecular materials that combine anisotropy with dynamic nature. Recently, the use of hydrogen bonding for the design of functional liquid crystalline materials has been shown to be a versatile approach toward the control of simple molecularly assembled structures and the induction of dynamic function. A variety of hydrogen-bonded liquid crystals has been prepared by molecular self-assembly processes via hydrogen bond formation. Rod-like and disk-like low-molecular weight complexes and polymers with side-chain, main-chain, network, and guest-host structures have been built by the complexation of complimentary and identical hydrogen-bonded molecules. These materials consist of closed-type hydrogen bondings. Another type of hydrogen-bonded liquid crystals consists of open-type hydrogen bonding. In this case, the introduction of hydrogen bonding moieties, such as hydroxyl groups, induces microphase segregation leading to liquid crystalline molecular order. Moreover, liquid crystalline physical gels have been prepared by the molecular aggregation of hydrogen-bonded molecules in non-hydrogen-bonded liquid crystals. They show significant electrooptical properties. An anisotropic gel is a new type of anisotropic materials forming heterogeneous structures.
216 citations
TL;DR: In this paper, the authors discuss some recent research areas which illustrate the broad scope of polyferrocenylsilane homopolymers and block copolymers with transition metals in the main chain.
Abstract: Polyferrocenylsilanes represent a recently established, readily accessible class of transition metal-containing macromolecules consisting of alternating ferrocene and organosilane units. High molecular weight, soluble samples of these materials were first prepared in the early 1990's by thermal ring-opening polymerization (ROP) of silicon-bridged [1]ferrocenophanes ([1]silaferrocenophanes). More recently living anionic and transition metal-catalyzed ROP methodologies have been developed, which permit unprecedented access to controlled polymer architectures (e.g. block copolymers) with transition metals in the main chain. Polyferrocenylsilane homopolymers and block copolymers offer exciting opportunities in materials and supramolecular science and for nanostructure applications. In this article some recent research areas are discussed which illustrate the broad scope of these interesting new materials.
TL;DR: In this paper, nanocomposites based on EVO copolymers and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading.
Abstract: (Nano)composites based on ethylene vinyl acetate copolymers (EVA) and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading. Polymer intercalation and filler exfoliation were evidenced by X-ray diffraction and transmission electron microscopy, respectively. Nanocomposites tensile properties showed that Young's modulus increases significantly even at very low content of the organo-modified filler while preserving high ultimate elongation and tensile stress. The matrix thermal stability in air was increased by 40°C and, interestingly, the obtained nanocomposites present flame retardant properties.
TL;DR: A full literature and patent account (about 100 references) is given on work describing vinyl polymerization of form the homopolymer poly(norbornene) as discussed by the authors, which is driven by its dielectric and mechanical properties for thte technical application as an interlevel dielectrics in microelectronics applications.
Abstract: A full literature and patent account (about 100 references) is given on work describing vinyl polymerization of form the homopolymer poly(norbornene). The interest in vinyl-poly(norbornene) is driven by its dielectric and mechanical properties for thte technical application as an interlevel dielectric in microelectronics applications. For comparison, the norbornene/olefin copolymerization is discussed also. The metal catalysts are introduced and important polymer product properties are emphasized. The six possible isomers for stereoregular poly(norbornene) are presented.
TL;DR: In this paper, double hydrophilic block copolymers were synthesized in aqueous medium using the MADIX process, starting from an either monofunctional or difunctional xanthate, and the resulting AB and ABA-type Double Hydrophilic Block Copolymers (DHBC) exhibited molar masses predetermined by the initial monomer/xanthate precursor molar ratio and polydispersity indices in the range 1.2-1.5.
Abstract: Double hydrophilic statistical, diblock and triblock copolymers comprised of acrylamide and acrylic acid units have been synthesized in aqueous medium using the MADIX process. Starting from an either monofunctional or difunctional xanthate, the resulting AB and ABA-type double hydrophilic block copolymers (DHBC) exhibited molar masses predetermined by the initial monomer/xanthate precursor molar ratio and polydispersity indices in the range 1.2–1.5. Batch copolymerizations yielded well-defined statistical copolymers that were chain-extended for the synthesis of novel poly- (acrylic acid-stat-acrylamide)-block-polyacrylamide DHBC.
TL;DR: PBT/organic montmorillonite (MMT) nanocomposites were prepared via melt intercalation and their nanostructure was characterized by means of X-ray diffraction and transmission electron microscopy.
Abstract: PBT/organic montmorillonite (MMT) nanocomposites were prepared via melt intercalation and their nanostructure was characterized by means of X-ray diffraction and transmission electron microscopy. Nanocomposite formation requires sufficiently hydrophobic organically modified layered silicates, as well as the presence of polar interactions between silicate and polymer. Three different alkylammonium surfactants were used to modify MMT. In addition, epoxy resin was added as a third component, and the effects on the intercalation and exfoliation behavior of the PBT nanocomposites were investigated.
TL;DR: In this article, a modification of hemicellulose was performed with 2-[(1-imidazolyl)formyloxy]ethyl methacrylate as a modifying agent and triethylamine as the catalyst.
Abstract: Communication: Hemicellulose/poly(2-hydroxyethyl methacrylate) (PHEMA)-based hydrogels were prepared by the radical polymerization of HEMA with hemicellulose purposely modified with well-defined amounts of methacrylic functions using a redox initiator system. Oligomeric hydrosolube hemicelluloses produced from spruce chips were used for modification studies. The chemical modification of hemicellulose was performed with 2-[(1-imidazolyl)formyloxy]ethyl methacrylate as a modifying agent and triethylamine as the catalyst. The kinetics of the modification reaction was monitored by means of H-1 NMR spectroscopy. The resulting hydrogels obtained after a 30 min reaction were homogeneous, elastic, and transparent materials.
TL;DR: In this article, organophilic montmorillonite clay and poly(ethylene oxide) (PEO) nanocomposites were intercalated by a solvent casting method using chloroform as the cosolvent.
Abstract: The organophilic montmorillonite clay and poly(ethylene oxide) (PEO) nanocomposites were intercalated by a solvent casting method using chloroform as the cosolvent. The prepared nanocomposites were characterized by an X-ray diffraction method to examine their microstructure. Rheological properties of both the PEO/clay nanocomposites and the immiscible PEO/clay blends were investigated via a rotational rheometer in steady shear mode with a parallel plate geometry. The shear thinning viscosity data were fitted with the Carreau model, which showed that steady shear viscosity increases with increasing clay loading. The hysteresis phenomenon is observed to be enhanced with clay loading. PEO/clay nanocomposites exhibit higher zero-shear-rate viscosity and sharper shear thinning behaviors than immiscible PEO/clay blends.
TL;DR: The atom transfer radical polymerization of acrylates in 1-butyl-3-methylimidazolium hexafluorophosphate was investigated in this paper.
Abstract: The atom-transfer radical polymerization (ATRP) of acrylates in 1-butyl-3-methylimidazolium hexafluorophosphate was investigated. The solubility of the acrylates in the ionic liquid depends on the substituent. The homogeneous polymerization of methyl acrylate gives polymers with Mn close to the calculated value and relatively narrow polydispersity. In heterogeneous polymerizations of higher acrylates, with the catalyst present in the ionic liquid phase, deviations from ideal behavior are observed although the polymerization of butyl acrylate approaches the conditions of a controlled polymerization.
TL;DR: In this paper, various synthetic and structural aspects of methylaluminoxane and the elementary processes involved in olefin polymerization, as identified by various spectroscopic techniques, are detailed.
Abstract: In this review, various synthetic and structural aspects of methylaluminoxane and the elementary processes involved in olefin polymerization, as identified by various spectroscopic techniques, are detailed. Various boron-based counterions and their interactions with metallocenium cations are discussed. A comparison between MAO and boron-based activators in terms of catalytic activity and polymer characteristics is made. Finally, the use of the above system in the polymerization of cationically polymerizable monomers and acrylates is discussed.
TL;DR: In this article, the influence of maleic anhydride-grafted poly(propylene) (PP-g-MA) as a compatibilizer on morphology development and rheological properties was investigated.
Abstract: Poly(propylene) compounds containing organophilic layered nanosilicates were prepared by means of melt extrusion at 210°C in order to investigate the influence of maleic anhydride-grafted poly(propylene) (PP-g-MA) as a compatibilizer on morphology development and rheological properties. It was found that the addition of PP-g-MA leads to the strong exfolliation of silicate layers within the matrix as investigated by WAXS. This process is associated with the build up of an unstable morphology as probed by dynamic rheology and with the violation of the time-temperature superposition principle. Annealing of the samples at extrusion temperature level leads to a coarsening of the silicate superstructure and further improvement of the exfoliation at the same time. This process results in a stable morphology with unique rheological properties indicating network-like superstructure of silicate layers.
TL;DR: In this paper, the dielectric relaxtion behavior of flexible polymer chains having the so-called type A dipoles parallel along yhe chain backbone is described, and some detailled dynamic features such as changes in the eigenfunction f p of a local correlation function with the chain concentration in solutions are disscussed in relation to motional coupling.
Abstract: This article describes the dielectric relaxtion behavior of flexible polymer chains having the so-called type A dipoles parallel along yhe chain back-bone. This behavior reflects the global chain notion. Viscoelastiicaly well known features of this notion, such as the power-law relationship between the relaxtion time and molecular weight of entengled linear chains (τ 1 ∼M 3.5 ), are also observed dielectrically. More importantly, the dielectric behavior of linear chains having once-inverted type-A dipoles enables us to find some detailled dynamic features such as changes in the eigenfunction f p of a local correlation function with the chain concentration in solutions. These change are disscussed in relation to motional coupling of concentraded chains. The dielectric properties delect the orientational correlation of two submolecules in the chain at two separate times, while the viscoelastic properties reflect the isochronal orientational anisotropy of individual submolecules. Thus the chain motion is differently averaged in the dielectric and viscoelastic properties, and comparison of these properties enables us to find novel dynamic features. Specifically, this comparision reveals the validity of the tube dilation molecular picture for entangled linear chains and weakening of the schort-time coherence of the submolecule motion due to the constraint release mechanism. Moreover, the dielectric method enables us to investigate the chain dynamics under strong flow and/or in a molecularly narrow space. In particular, the retarded dielectric relaxation found for homopolymers and block copolymers in such narrow space (in the microdomains for the latter) indicates important effects of the spatial and thermodynamic constraints on the global chain motion. All the above results in turn demonstrate the importance of the dielectric method in investigations of the polymer dynamics.
TL;DR: In this paper, in-situ ATR-FT-IR spectroscopy of consecutively deposited polyelectrolyte multilayer systems terminated either with poly(ethyleneimine) (PEI) or polyanions, such as poly-(acrylic acid) (PAC), poly(maleic acid-co-propylene) (PMA-P), or poly(vinyl sulfate), was investigated.
Abstract: Protein adsorption was studied by in-situ ATR-FT-IR spectroscopy of consecutively deposited polyelectrolyte multilayer systems terminated either with poly(ethyleneimine) (PEI) or polyanions, such as poly-(acrylic acid) (PAC), poly(maleic acid-co-propylene) (PMA-P) or poly(vinyl sulfate) (PVS). The influence of the polyanion type, pH and ionic strength was investigated. Negatively charged human serum albumin (HSA) was strongly repelled by multilayers terminated with weak polyanions (PAC, PMA-P), whereas moderate attraction was observed for those terminated with the strong polyanion PVS. Changing the pH from 7.4 to 5 resulted in enhanced HSA adsorption onto PAC-terminated multilayers. An increase in ionic strength diminished the attractive HSA adsorption onto PEI-terminated multilayers. For the PEI/PAC system, the biomedically relevant adsorption of human fibrinogen (FGN) is determined via its isoelectric point in accordance with three other proteins.
TL;DR: In this paper, the influence of chemical modifications on the crossover region of dynamic glass transition, where the relaxation times of a relaxation and Johari Goldstein mode β approach each other, is discussed.
Abstract: Relaxations in a poly(alkyl methacrylate) series are systematically influenced by chemical modifications like the variation of side-chain length, random copolymerization, or molecular weight. Recent results concerning the influence of chemical modifications on special parts of the relaxation chart are reviewed. The discussion is focused on two points: (i) The influence of chemical modifications on the crossover region of dynamic glass transition, where the relaxation times of a relaxation and Johari Goldstein mode β approach each other, is discussed. A general crossover scenario with a separate onset of cooperative a relaxation is observed for all lower members of this series. High temperature, process a above and cooperalive, a relaxation below the crossover are shown to be distinct processes. Chemical modifications related to an increase in free volume shift this scenario mainly to lower frequency and temperature. Further details depend on the specific modification. (ii) The nanophase separation of incompatible main- and side-chain parts in all higher members of the poly(alkyl methacrylate) series is discussed. This effect is concluded from the coexistence of two dynamic glass transitions in these homopolymers, the conventional a (or α) process and an additional low temperature glass transition α PE . It is shown that the low T g process is related to cooperative motions in the polyethylene-like side-chain parts. The existence of static nanodomains in the range 0.5 to 1.5 nm is confirmed by means of wide and small angle X-ray scattering data. The estimated nanodomain size is compared with the size of dynamic heterogeneities estimated independently from calorimetric data for the polyethylene-like glass transition using the fluctuation approach.
TL;DR: In this article, two component polymer brushes (polystyrene and poly(2-vinylpyridine)) were synthesized by grafting from the surface of Si-wafers.
Abstract: Two component polymer brushes (polystyrene and poly(2-vinylpyridine)) were synthesized by grafting from the surface of Si-wafers. The brushes are sensitive to the surrounding medium, and their morphology and composition of the top of a brush can be switched upon exposure to different solvents. Thus surface energetic states and roughness of the film can be precisely tuned.
TL;DR: In this paper, a living poly(propylene) was synthesized at 25°C using a bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of 13C NMR spectroscopy.
Abstract: Highly syndiotactic “living” poly(propylene)s were synthesized at 25°C using a bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of 13C NMR spectroscopy. The syndiotactic poly(propylene) contains isobutyl, isopentyl and propyl end groups, suggesting that the living polymerization of propylene was initiated via 1,2-insertion, followed by 2,1-insertion as the principal mode of polymerization. Pentad distribution analysis revealed that the syndiospecific polymerization proceeds under chain-end control.
TL;DR: In this paper, it was demonstrated that the length per monomer also depends on the solvent quality, i.e., the cylinders are shorter in a poor solvent as compared to a good solvent.
Abstract: Communication: Polymacromonomers with a main chain much larger than the side-chain length adopt the form of cylindrical brush polymers the contour length per mainchain monomer of which depends on the side-chain length. In the present investigation it is demonstrated that the length per monomer also depends on the solvent quality, i.e., the cylinders are shorter in a poor solvent as compared to a good solvent. It is argued that the repulsion of the side chains represents the extension force, which acts against the entropic contraction force of the main chain. Thus, cylindrical brushes may be suitable as responsive materials for sensors, actuators or soft machines.
TL;DR: In this article, the properties of the materials are discussed: conductivity and photoconductivity, electrical charge/dis charge, electrocatalytic reductions, photocatalytic reduc tions/oxidations of and at thin film electrodes, catalytic and oxidations, photoinduced electron transfer.
Abstract: Phthalocyamines (Pc) and related macrocycles in combination with organic or inorganic macromolecules are reviewed. From the structural point of view, the macrocyclic compounds in macromolecular phases are subdivided into five types. Syntheses are described in detail, and characteristic experimental procedures are given. The properties of the materials are discussed: conductivity and photoconductivity, electrical charge/dis charge, electrocatalytic reductions, photocatalytic reduc tions/oxidations of and at thin film electrodes, catalytic and photocatalytic oxidations, photoinduced electron transfer.
TL;DR: The free-radical polymerization of vinyl monomers in the presence of dibenzyl trithiocarbonate (DBTTC) and under 60 Co γ-irradiation is of living character as mentioned in this paper.
Abstract: The free-radical polymerization of vinyl monomers in the presence of dibenzyl trithiocarbonate (DBTTC) and under 60 Co γ-irradiation is of living character. Under 60 Co irradiation, the bonds between benzyl group and sulfur were cleaved, benzyl radicals initiate the polymerization. The propagating radical together with trithiocarbonate radicals form a dormant polymer chain. The fast equilibrium between propagation radical and dormant polymer chain controls the polymerization.
TL;DR: In this paper, a polymeric divinylbenzene microspheres (MS) of narrow size distributions were prepared by microchannel emulsification and subsequent polymerization, where the MS diameter can be controlled by the size of the MC.
Abstract: Polymeric divinylbenzene microspheres (MS) of narrow size distributions were prepared by microchannel (MC) emulsification and subsequent polymerization. Using two types of MC plates, large MS with 9.2 μm diameter on average and 5.7% coefficient of variation, as well as small MS with 3.4 μm diameter on average and 7.4% coefficient of variation were prepared. The MS diameter can be controlled by the size of the MC. This method is advantageous for synthesizing polymeric MS of narrow size distributions because of its simplicity.
TL;DR: In this paper, a novel organic/inorganic nanocomposites of polyethylene (PE) was prepared via in-situ coordination polymerization, where the Ziegler-Natta catalyst was first supported on the surface of silicate nanowhiskers to initiate the polymerization of ethylene on the surfaces of these nanowiskers.
Abstract: A novel organic/inorganic nanocomposites of polyethylene (PE) was prepared via in-situ coordination polymerization. The Ziegler-Natta catalyst was first supported on the surface of silicate nanowhiskers to subsequently initiate the polymerization of ethylene on the surface of these nanowhiskers. The nanowhiskers were encapsulated by polyethylene and became reinforcement fibers of the composite. The strong interaction between the uniformly dispersed nanowhiskers and the resin matrix resulted in the formation of a kind of organic/inorganic network providing good mechanical properties.