Copolymers—A refined way to tailor intrinsically conducting polymers

An overview is given on electrochemically prepared intrinsically conducting copolymers, their preparation, their properties, potential applications and significant differences from the respective homopolymers. Particular attention is paid to verification of the formation of true copolymers and their characteristic features in comparison to mixtures of homopolymers.     

The microwave processability of semicrystalline polymers

The overall objective of these studies was to investigate the relationship between polymer structure and microwave absorptivity. In this paper, the microwave processing of semicrystalline polymers such as poly(ether ether ketone) (PEEK), nylons, and poly(ethylene terephthalate) (PET), via a cylindrical resonance wave cavity and a rectangular standing wave applicator is described. These polymeric materials were irradiated in low power (< 50W) electric fields at 2.45 GHz. Silicone flexible molds were necessary for improved processing of nylons and PEEK at temperatures below their T_c Rapid heating rates were observed between the glass transition temperature, T_g, and the melting temperature, T_m, for all these polymers provided that T_c was exceeded. Both dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA) spectra were utilized to predict the heating phenomena between amorphous and semicrystalline materials and to explain the rapid crystallizing rate of PEEK. above its glass transition temperature. Correlations were drawn between (a) the apparent activation energy and the critical temperature (T_c) and (b) the shape of the dielectric spectra at 2.45 GHz and its shape in kHz region.     

The effect of ion-polymer binding on ionic diffusion in dicarbazole-based conducting polymers

An electrochemical polymerization and characterization is reported on a series of eight dicarbazole-type conducting polymers with different attached functional groups. The influence of the electronic character of the subgroup on the ionic conductivity properties of the polymers was examined. Impedance spectroscopy measurements were used to set the ionic chemical diffusion coefficients, D, in the polymer matrix at a variety of doping levels, for each of the polydicarbazoles. We relate D dependency with potential to morphological and electronic processes in the polymer occurring during oxidation. By combination of cyclic voltammetry and impedance spectroscopy for part of the series we reveal that the diffusion of ions in the matrix is easier in polymers were the functional group is highly electron-attracting.     

Synthesis and application of conducting graft copolymer with viable processability

A soluble and processable conducting copolymer, poly(acrylonitrile-co-vinyl acetate)-graft-polypyrrole, noted as P(AN-co-VA)-g-PPY, has been synthesized successfully by graft polymerization of pyrrole in a colloid of P(AN-co-VA) within DMF/HCl solution. FTIR, ¹HNMR, EPR, DSC, GPC and elemental analysis results confirm that the polypyrrole side chains have grown onto P(AN-co-VA) chain backbones and the maximum PPY content reached 15.46 wt% under the experimental conditions. The conducting P(AN-co-VA)-g-PPY copolymer can be dissolved in organic solvents and easily processed to the film with strong stretching strength as high as 30 MPa and high conductivity as high as 10^?1 S/cm. By control of the amounts of P(AN-co-VA) and pyrrole, the property adjustment between electronic conductivity and stretching strength of P(AN-co-VA)-g-PPY film can be achieved, which is of signality for different practice applications. As an example, the noble metal microstructures including tortuous Ag wire and hierarchically hedgehog-like Au sphere have been obtained via a reduction of silver nitrate or hydrogen tetrachloroaurate using the as-prepared conducting film without any additives, which may open up a thinking room for us to search new microstructures and new materials.     

噻吩类导电高聚物的研究进展

噻吩类聚合物是研究较为广泛的功能高分子材料。详述了通过化学氧化聚合法和电化学氧化聚合法所合成的噻吩类导电聚合物的性能和用途,常用的结构与性能表征方法以及噻吩类导电聚合物在光、电、磁等各种领域中的应用。     

The effect of mechanochemical degradation on processability and porperties of PVC

The morphology and mechanical properties of PVC after vibro- or jet-milling as well as the rheological behavior of the mechanochemically degraded PVC were studied. The effect of vibro or jet-milling on the crystalline structure of PVC was examined through the crystalline absorption bands of FTIR spectra. The intensity of the crystalline absorption bands becomes weaker and indistinct with milling time. The PVC after milling results in improved melting efficiency, lower melt viscosity, shorter plasticizing time and higher tensile strength in comparing with those of the undegraded PVC due to the destruction of the crystalline structure and the decrease of molecular weight.     

The effect of surface energy of boron nitride on polymer processability

Flow instabilities manifest themselves as distortions on the extrudate surface (melt fracture). They are usually observed at high production rates in many polymer processing operations. Certain fluoropolymers/fluoroelastomers have long been used as processing aids for surface melt fracture elimination. Recent developments have shown that a small amount of boron nitride (BN) powder may successfully eliminate surface melt fracture and also delay the onset of gross melt fracture to higher rates. It has also been reported that a combination of BN and fluoropolymer/fluoroelastomer enhances the effectiveness of the polymer processing even further. The main objective of the present work was to measure the surface properties of a number BN powders, mainly surface energy, in order to gain a better understanding of its performance as a processing aid. Based on this study, it can be concluded that surface energy plays an important role in deciding the possible interactions between the processing aid, polymer melt and the extruding surface. It is observed that the lubricious nature of BN along with an optimum balance of its polar (non‐dispersive) and non‐polar (dispersive) components of surface energy renders BN a successful processing aid in eliminating both sharkskin and gross melt fracture phenomena. Polym. Eng. Sci. 44:1543–1550, 2004. © 2004 Society of Plastics Engineers.     

The effect of long chain branching on the processability of polypropylene in thermoforming

Linear polypropylene was modified by reaction with peroxydicarbonates in a twin screw extruder to obtain varied degrees of long chain branching. The melt strength and the elasticity of the modified polymers were found to increase with the modification. The processability in foaming and thermoforming processes improved with branching and showed an optimum, beyond which higher degrees of long chain branching appeared not to help any further. The branched PP samples showed distinct strain hardening in the elongational viscosity, which was absent from the original linear melts. Melt strength, elasticity and strain hardening increased with the increase of the number of long chain branches on the main chain. The effect of molecular weight and molecular weight distribution of the precursor on the improvement of the processability of the polymer was examined. Polym. Eng. Sci. 44:973–982, 2004. © 2004 Society of Plastics Engineers.     

The morphology and structure of highly conducting polymers

A review on the morphology and structure of highly conducting polymers is presented. As a special case the inorganic polymer polysulfur nitride is mentioned in the introduction. The main part of the review is concerned with polyacetylene doped by diffusion of impurities or electrochemically. Applications for light weight batteries and low cost solar cells are briefly treated. The final section deals with doped polyparaphenylen polyparaphenylensulfide, and polypyrrol and the soliton type of conduction in lightly doped polyacetylene.     

终止剂对PVC树脂热稳定性和加工性能的影响

介绍了不同类型终止剂在105 m3聚合釜悬浮法生产SG5型PVC过程中对PVC树脂稳定性和后加工性能的影响.     

Evaluation of the processability of boron‐containing organosilazane polymers based on shear rheology

The shear rheology of boron‐containing organosilazane polymers has been investigated in detail with a double objective. The first objective was to evaluate their processability to form fibers by melt‐spinning, and the second objective was to predict their molecular structure. We focused on a representative type of boron‐containing organosilazane polymers called boron‐modified polysilazanes (BmPSs) with the ideal structure [B(C₂H₄SiCH₃NCH₃)₃]_n (C₂H₄ = CHCH₃, CH₂CH₂). Characterization tools showed that their viscous and elastic properties are strongly affected by molecular parameters fixed during synthesis and in particular by the methylamine (MA) : tris(dichlorosilylethyl)borane (TDSB) molar ratio imposed during their synthesis. In the spinning domain, the frequency dependences of the storage and loss moduli showed that the prerequisite conditions for obtaining polymer fibers are fulfilled with samples having 9.0 ≤ MA : TDSB molar ratios ≤ 9.7. However, the presence of thickening in the computed extensional viscosity function and the loss of cohesion of filament derived from samples with MA : TDSB ratio > 9.2 during drawing put in evidence the best potential of polymers with 9 ≤ MA : TDSB ratio ≤ 9.2 to generate fine‐diameter solid filaments in a stable process. Based on rheological tests, the molecular structure of BmPSs has been tentatively predicted in relation with the MA : TDSB ratio. The increase of the latter favored the disentanglement of the polymer framework, and we postulated that it lowered the molecular weight. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of shearing history on the rheological properties and processability of branched polymers. I

The influence of shearing history on the viscoelastic properties of low-density polyethylene (LDPE) is investigated. Swelling of extrudates from a melt indexer is measured for monitoring the variation in viscoelasticity. Continuous shearing of molten LDPE reduces the swelling ratio. The reduction is not due to molecular degradation, as evidenced by constancy of intrinsic viscosity. The rate of the reduction in the swelling ratio depends on the shearing conditions and characteristics of LDPE, but the swelling ratio finally attain a steady value. The swelling ratio reduced by the continuous shearing is completely recovered by solvent or heat treatment. The ratio of the completely reduced swelling ratio to the completely recovered one is defined as a new index representing the viscoelastic variation, the processing index (PI), and the relationship between PI and the primary molecular parameters of LDPE is investigated. It is concluded that the variation in the viscoelastic properties becomes more remarkable with increase in the weight-average molecular weight. The cause of the viscoelastic variation is also discussed from the rheological and thermodynamic points of view.     

The effect of the plasticizer system on the processability of poly(vinyl chloride) compounds

To conserve energy and process time, the judicious use of benzyl phthalate as a partial substitution for dialkyl phthalate is suggested. Data is presented from laboratory and pilot plant tests. Confirmation and correlation with factory trials is shown.     

基于本征导电聚合物的分离膜体系的研究进展

综述了新一代利用本征导电聚合物独特电活性制得的智能分离膜体系的研究进展.这种分离膜可通过电化学控制来改变其物理和化学特性,从而可就地调整膜的迁移特性和选择特性;可制成独立式膜、复合膜以及基于培养基的薄膜等以适合不同的应用.为了提高体系的电化学效率,得到更好的迁移效果,需要改进其分离装置及相关的系统配置.最后介绍了这种分离膜在矿物质的分离和蛋白质的分离等特殊场合的应用状况.     

The effect of backbone fluorination on the carrier mobility in alkoxy and alkyl substituted conducting polymers of the poly(phenylenevinylene) type

Summary We report the synthesis of some new backbone fluorinated polymers of the poly(phenylenevinylene) type. The new polymers were characterised by NMR, SEC and X-ray powder diffraction. The charge carrier mobilities were determined using pulse radiolysis time resolved microwave conductivity (PR-TRMC) and the carrier mobilities were compared to the similar non-fluorinated analogues. The changes in charge carrier mobilities as a function of molecular substitution pattern is discussed in terms of other materials properties such as electronic structure and absorption properties. The major result is that it was found possible for this type of material to alter the electronic energy levels by molecular substitution without imparting significant changes in the magnitude of the charge carrier mobilities and the optical properties.     

The synergistic effect of boron nitride particle and die on the capillary extrusion processability of mLDPE

The synergistic effects of boron nitride (BN) powder and die on the rheology and processability of metallocene‐catalyzed low density polyethylene (mLDPE) were investigated. The processability in the extrusion process is closely related to the interfacial properties between the polymer melts and the die wall. BN powder was added to mLDPE to reduce the friction coefficient and surface energy. Adding 0.5 wt% BN powder to mLDPE was very effective in improving the processability and the extrudate appearance. To study the effect of die surface property, three different dies were applied in capillary extrusion. One was conventional tungsten carbide (TC) die, and the others were hot‐pressed BN (hpBN) die and hot‐pressed BN composite (hpBNC) die. The applications of these BN dies were quite effective in delaying surface melt fracture (sharkskin) and postponing gross melt fracture to higher shear rate compared to the TC die. These improvements result from the fact that BN dies reduce the wall shear stress significantly and promote slip. The synergistic effect of processability could be obtained when both BN powder and hpBN die were used together.     

Functionalization of conducting polymers for biointerface applications

As the field of biomedical engineering grows, there is increasing demand for materials that can interface with biological materials – notably for use as biosensors, medical implants, neural interfaces and tissue engineering scaffolds. Conducting polymers are promising candidates for these purposes, owing to good biocompatibility and intrinsic conductivity with superior mechanical properties compared to traditional metal-based materials. Functionalization of the conducting polymers can further enhance these advantages, imparting properties such as improved solubility, antifouling behavior, stimuli-responsive switchability and the ability to modulate cell growth and differentiation. This review briefly discusses the incorporation of biodopants and direct attachment of (bio)molecules to the conducting polymers, before focussing on the rapidly-growing field of polymer grafting – with the aim of tailoring these materials towards a range of bioapplications.     

Doping-induced broadening of the hole density-of-states in conducting polymers

The density-of-states distribution in conducting polymers reflects the energy disorder caused by electrostatic and steric interactions resulting from the different environment in which each molecule is placed. In case of p-doping (oxidation), the highest occupied molecular orbital (HOMO) manifold spreads in energy following a distribution as a result of long-range electrostatic (dipolar) interactions with the surrounding disordered host. In this paper the repercussion of the dipolar disorder on electrochemical signals of standard polypyrrole films is explored. The analysis is based on the chemical capacitance variation with the applied potential in experiments performed in quasi-equilibrium conditions. In addition to the Gaussian shape of cyclic voltammograms at low-doping levels, the model is able to qualitatively account for the current plateau usually observed at high oxidation potentials. This approach allows to estimating the dipolar moment associated to the polymer/dopant complex.