Poly(ethylene glycol) block poly(butyl acrylate) .1. Synthesis

Prepolymers of poly(ethylene oxide) (Pre-PEG) were synthesized by reacting azoisobutyronitrile (AIBN) with poly(ethylene glycol) (PEG), and their structures were characterized by IR and UV. The molecular weight of pre-PEG was related to the feed ratio and reaction time. These prepolymers can be used to prepare block copolymers - poly(ethylene oxide)-block-poly(butyl acrylate) (PEO-b-PBA) by radical polymerization in the presence of butyl acrylate (BA). Solution polymerization was a suitable technique for this step. The yield and the molecular weight of the product were related to the ratio of the prepolymer to BA, the reaction time, and temperature. GPC showed that the molecular weight increased with a higher ratio of BA to pre-PEO. The intrinsic viscosity of the copolymers was only slightly dependent on reaction time, but decreased at higher reaction temperatures, as did the amount of PEA homopolymer. (C) 1997 John Wiley & Sons, Inc.

Liquid crystalline polymer as a processing agent in blends of poly(ether-ketone)/LCP70

Blends of a liquid crystalline thermotropic copolyester (LCP70) and an amorphous phenolphthalein based poly(ether-ketone)(PEK-C) with two viscosities were prepared by melt blending. The blends' morphology, rheological and mechanical properties were investigated by DSC, SEM, mechanical and rheological tests. It was observed that the optimum composition of the PEK-C/LCP70 blend was 10 wt% LCP for both mechanical and rheological properties. When the LCP content was less than 10%, the LCP phase existed as finely dispersed fibrous domains with a diameter of about 1 mu m in the matrix, and both tensile and flexural properties were improved. In contrast, when the LCP content reached 20% or more, the LCP domains coalesced to ellipsoidal particles with a diameter of about 5 mu m, and the mechanical properties decreased as a result. It is demonstrated that pure PEK-C with a high viscosity which was difficult to process by melt extrusion, could be extruded conveniently when 10% LCP70 was incorporated. It is emphasized that LCP not only can be used as a reinforcing phase but also an effective processing agent for engineering thermoplastics, especially for those with high viscosity and narrow processing window. (C) 1997 Elsevier Science Ltd.

Determination of the standard heterogeneous rate constant in polyelectrolyte using steady state microdisk voltammograms

The steady state voltammogram at a microdisk electrode is used to measure the diffusion coefficient and standard heterogeneous rate constant (k(s)) of ferrocene in polyelectrolyte PEG + LiClO4. The k(s) obtained is smaller in polyelectrolyte than in liquid medium. It is proposed that the polymer solvent electron transfer dynamics are affected by the relaxation rates of the ether dipole sites on the polymer chains, which are in turn constrained by the rates of polymer chain segment, or local structure, relaxations. The dependence of k(s) on temperature is observed. The k(s) increases with increasing temperature.

Study of the miscibility and thermodynamics of cellulose diacetate-poly(vinyl pyrrolidone) blends

The miscibility of blends of cellulose diacetate (CDA) and poly(vinyl pyrrolidone) (PVP) was extensively studied by means of differential thermal analysis and dynamic mechanical thermal analysis, tensile test, measuring viscosity of diluted and concentrated solutions of blends in acetone-ethanol mixture and morphological observations. A single glass transition temperature is observed, which is intermediate between the glass transition temperatures associated with each component and depends on composition. A synergism in mechanical properties of blends was found. The absolute viscosity and the intrinsic viscosity of solutions of blends are much higher than the weight average values of solutions of CDA and PVP. Optically clear and thermodynamically stable films were formed in the composition range of CDA/PVP = 100/0 to 50/50w/w. Fourier transform infrared was used to investigate the nature of CDA-PVP interaction. Hydrogen bonds were formed between hydroxyl groups of CDA and carbonyl groups of PVP. Heats of solutions of CDA/PVP blends and their mechanical mixtures were measured by using a calorimeter. Mixing enthalpy obtained with Hess's law approach was used to quantify interaction parameters of this blending system. It was found that mixing enthalpies and interaction parameters were negative and composition dependent. (C) 1997 Elsevier Science Ltd.

Novel polyaryletherketones containing various pendant groups .1. Synthesis and characterization

Novel high glass transition temperature polyaryletherketones, containing pendant amido, alkyl, and carboxyl groups with reduced viscosity above 0.54 dL/g, were synthesized via solution nucleophilic polycondensation reaction of phenolphthalin, 2',2 ''-diisopropyl-5',5 ''-dimethylphenolphthalin, and 3,3'-bis(4-hydroxyphenyl)isobenzopyrrolidone with bis(4-nitrophenyl)ketone in the presence of potassium carbonate. By ion exchange with Na+ and K+, four ionomers were also prepared. A new monomer simultaneously containing carboxyl and algyl substituents was synthesized by reduction reaction of 2',2 ''-diisopropyl-5',5 ''-dimethyl-phenolphthalein. The resulting polymers were soluble in a few polar aprotic solvents; transparent, colorless, and tough films could easily be cast from DMF or DMSO solution. The mechanical properties of the films were excellent; and their tensile strength, elongation at break, and tensile moduli were in the range of 67.1-97.1 MPa, 7.8-165%, and 1.47-2.27 GPa, respectively. The prepared polymers showed fairly good thermal stability and resonably high glass transition temperatures above 210 degrees C. (C) 1997 John Wiley & Sons, Inc.

Rheological properties of phenophthalein poly(ether ether ketone)

The rheological properties of the novel engineering thermoplastic phenophthalein poly(ether ether ketone) (PEK-C) have been investigated using both a rotational and a capillary rheometer. The dependence of the viscosity on the shear rate and temperature was obtained. The activation energy was evaluated both from the Arrhenius and the Williams-Landel-Ferry (WLF) equation. An estimate for the proper E(eta) (dependent only on the chemical structure of the polymer) has been found from the WLF equation at temperatures about T-g + 200 degrees C. Measurements of the die swell have been performed. The first normal stress differences were evaluated from the die swell results and compared with the values obtained from the rotational rheometer at low shear rates.

The phase inversion and morphology of nylon 1010 polypropylene blends

Noncompatibilized and compatibilized blends of nylon 1010/PP blends having five different viscosity ratios were prepared by melt extrusion. Glycidyl methacrylate-grafted-polypropylene (PP-g-GMA) was used as the compatibilizer to enbance the adhesion between the two polymers and to stabilize the blend morphology. The effect of the viscosity ratio on the morphology of nylon 1010/polypropylene blends was investigated, with primary attention to the phase-inversion behavior and the average particle size of the dispersed phase. The relationship between the mechanical properties and the phase-inversion composition was investigated as well. Investigation of the morphology of the blends by microscopy indicated that the smaller the viscosity ratio (eta(PP)/eta(PA)) the smaller was the polypropylene concentration at which the phase inversion took place and polypropylene became the continuous phase. The compatibilizer induced a sharp reduction of particle size, but did not have a major effect on the phase-inversion point. An improvement :in the mechanical properties was found when nylon 1010 provided the matrix phase. (C) 1996 John Wiley & Sons, Inc.

The rheological properties of polyaniline solution

This paper presents our work on the rheological properties of the solution of polyaniline (PAn) in N-methyl-2-pyrrolidone (NMP). The results indicate that the solution's non-Newtonian property becomes more prominent with the increase in solution concentrations exhibiting the behavior of pseudo-plastic fluid. Besides, there is a critical concentration C-v (around 0.06 g/ml), beyond which the viscosity of the PAn/NMP solution takes a sudden increase. with temperature rising, both the viscosity and the thixotropy of the solution decrease, implying that there exist physical cross-linking interactions between the molecular chains in the solution.

Synthesis and characterization of thermotropic copolyesters and copoly(ester-amide)s containing oxyethylene-ether as the spacer

Flexible oxyethylene-ether was introduced into the aromatic copolyesters and copoly (ester-amide)s to reduce the melting point of resulting polymers. The melting point was greatly reduced to 200 degrees C or even lower in some cases, and the molecular weight was satisfactorily high as reflected by inherent viscosity. The polymers exhibited high thermal stability and good mechanical properties as determined by TGA and mechanical tests. The copolyester showed better crystallinity and liquid crystallinity than corresponding copoly (ester-amide)s with similar monomer composition as reflected by POM observation and WAXD study. The melting points for both copolyesters and copoly (ester-amide)s showed great dependence on the p-acetoxybenzoic acid (PAB) content in monomer composition and reached the lowest value when PAB was 29 mol%.

SYNTHESIS OF POLYBUTADIENE MACROINITIATOR AND POLYBUTADIENE/POLYACRYLAMIDE BLOCK-COPOLYMERS

An azo-group containing polybutadiene macroinitiator was prepared by Pinner synthesis and characterized by IR, NMR, GPC, viscosity and elemental measurements. The macroinitiator was further use to polymerize acrylamide (AAm) in benzene to form polybutadiene/polyacrylamide (PBD/PAAm) block copolymers. High conversion of AAm was obtained over a wide range of monomer/macroinitiator ratios. The PBD/PAAm block copolymers were found to have excellent solvent resistance.

EFFECT OF ETHYLENE-PROPYLENE COPOLYMER WITH RESIDUAL PE CRYSTALLINITY ON MECHANICAL-PROPERTIES AND MORPHOLOGY OF PP/HDPE BLENDS

Morphology and mechanical properties of polypropylene (PP)/high density polyethylene (HDPE) blends modified by ethylene-propylene copolymers (EPC) with residual PE crystallinity were investigated. The EPC showed different interfacial behavior in PP/HDPE blends of different compositions. A 25/75 blend of PP/HDPE (weight ratio) showed improved tensile strength and elongation at break at low EPC content (5 wt %). For the PP/HDPE = 50/50 blend, the presence of the EPC component tended to make the PP dispersed phase structure transform into a cocontinuous one, probably caused by improved viscosity matching of the two components. Both tensile strength and elongation at break were improved at EPC content of 5 wt %. For PP/HDPE 75/25 blends, the much smaller dispersed HDPE phase and significantly improved elongation at break resulted from compatibilization by EPC copolymers. (C) 1995 John Wiley & Sons, Inc.

IN-SITU COMPOSITE - PHENOLPHTHALEIN POLYETHERSULFONE-THERMOTROPIC LIQUID-CRYSTALLINE POLYMER BLENDS

Phase behavior, thermal, theological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES-C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET). It was found that these two polymers form optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES-C/PHB-PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES-C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES-C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing < 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processing conditions.

PENDANT FUNCTIONAL-GROUP COPOLYETHER SULFONES .1. SYNTHESIS AND CHARACTERIZATION OF NEW COPOLYETHER SULFONES WITH PENDANT ALDEHYDE GROUPS MODIFIED INTO PHENOLIC AZOMETHINE GROUPS

New functional copolyether sulfones with pendant aldehyde groups were synthesized by the classical polycondensation reaction between 4,4' -dichlorodiphenyl sulfone (I) and various bisphenols such as 5,5'-methylene bis-salicylaldehyde (II-2), 2,2-bis( 4-hydroxyphenyl)propane (III), and 2,6-bis(4-hydroxybenzylidene)cyclohexanone (IV). Condensation reaction with 4-aminophenol led to pendant phenolic azomethine groups containing copolyether sulfones. The structures of the resulting polymers were confirmed by IR, H-1-NMR spectra, and elemental analyses. The polymers were characterized by reduced viscosity, solubility, thermal stability, DSC, and x-ray diffraction measurements.

CRITERION OF POLYMER POLYMER MISCIBILITY DETERMINED BY VISCOMETRY

The criteria of polymer-polymer miscibility determined by viscometry are reviewed, and a new criterion is proposed based on the classical Huggins equation and the Huggins coefficient K(m) in the blends. It was found that, in a ternary (polymer-A)-(polymer-B)-solvent system, [GRAPHICS] In the absence of strong specific interaction forces between molecules that would encourage aggregation and at sufficiently low concentration, the above equation can be written thus: [GRAPHICS] This equation can be used to determine the miscibility of polymer blends, when: alpha greater-than-or-equal-to 0 miscible, alpha < 0 immiscible. It is found that the new criterion is reasonable and suitable to predict polymer-polymer miscibility by the viscometry method.

STRUCTURE AND PROPERTIES OF SEQUENTIALLY POLYMERIZED PROPYLENE-B-[ETHYLENE-CO-PROPYLENE]-B-PROPYLENE COPOLYMERS

The structure and properties of presumed block copolymers of polypropylene (PP) with ethylene-propylene random copolymers (EPR), i.e., PP-EPR and PP-EPR-PP, have been investigated by viscometry, transmission electron microscopy, dynamic mechanical analysis, differential scanning calorimetry, gel permeation chromatography, wide-angle x-ray diffraction, and other techniques testing various mechanical properties. PP-EPR and PP-EPR-PP were synthesized using delta-TiCl3-Et2AlCl as a catalyst system. The results indicate that the intrinsic viscosity of these polymers increases with each block-building step, whereas the intrinsic viscosity of those prepared by chain transfer reaction (strong chain-transfer reagent hydrogen was introduced between block-building steps during polymerization) hardly changes with the reaction time. Compared with PP / EPR blends, PP-EPR-PP block copolymers have lower PP and polyethylene crystallinity, and lower melting and crystallization temperatures of crystalline EPR. Two relaxation peaks of PP and EPR appear in the dynamic spectra of blends. They merge into a very broad relaxation peak with block sequence products of the same composition, indicating good compatibility between PP and EPR in the presence of block copolymers. Varying the PP and EPR content affects the crystallinity, density, and morphological structure of the products, which in turn affects the tensile strength and elongation at break. Because of their superior mechanical properties, sequential polymerization products containing PP-EPR and PP-EPR-PP block copolymers may have potential as compatibilizing agents for isotactic polypropylene and polyethylene blends or as potential heat-resistant thermoplastic elastomers.