摘要:

AbstractPolymerization of methyl methacrylate initiated by ceric ammonium nitrate‐maltose has been investigated in aqueous nitric acid under nitrogen in the temperature range 20.5‐35°C. The dependence of the initial rate of polymerization and the initial rate of ceric ion consumption on maltose, Ce(IV), and monomer concentrations has been determined. The reaction orders were found to depend on ceric ion concentration. At a moderately high Ce(IV) concentration (1 × 10−3mol litre−1) the orders were 1/2 and 3/2 with respect to maltose and monomer concentration, respectively, and independent of Ce(IV) concentration. But at a low Ce(IV) concentration (4 × 10−4mol litre−1) the orders with respect to monomer and Ce(IV) changed to 1 and 1/2, respectively. The effect of temperature was also examined. The average molecular weight, as determined by size‐exclusion chromacography, was found to depend on maltose, Ce(IV), and monomer concentrations, as well a

ISSN:0007-1641    

DOI:10.1002/pi.4980220102

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe intrinsic viscosities of blends of bisphenol‐A polycarbonate and poly(hexamethylene sebacate) have been measured in chloroform as a function of blend composition for a variety of molecular weight species. The compatibility of the polymer blend mixtures is characterized by the parameter δb, from the Krigbaum and Wall theory. UsingTgof the blend as a measure of bulk solid‐state compatibility, a correlation is obtained with the Krigbaum and Wall parameter δbfor each of the molecular weight pairs studied. Slopes of the correlation are invariant, as expected, as the chemical composition is the same for the different molecular weight pairs st

ISSN:0007-1641    

DOI:10.1002/pi.4980220103

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe kinetics of photo‐oxidative degradation and stabilization of poly(2,6‐dimethyl‐1,4‐phenylene oxide) have been studied in the temperature range 313‐363 K using monochromatic light of 365 nm with a constant intensity flux of 8.7 × 10−9einstein s−1cm−2in the absence and presence of Ni(II) O,O′‐diisopropyldithiophosphate. The course of degradation and stabilization was determined by means of light scattering and spectroscopic techniques. The extent of photodegradation was followed by carbonyl formation, gel content and activation energy. The incorporation of 1.2 wt% stabilizer in the matrix of the polymer films exercises the maximum protective influence on the photodegrad

ISSN:0007-1641    

DOI:10.1002/pi.4980220104

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractReaction conditions for the preparation of poly(1,4‐phenylene sulphide) (PPS) directly from bis(4‐bromophenyl) disulphide (BBD) have been established. Reactions were performed in a boiling quinoline/pyridine solvent mixture (91% by vol. quinoline) in the presence and absence of copper powder. Reaction products were fractionated and the fractions characterised using elemental analysis, IR and NMR spectroscopy, viscometry, hot‐stage microscopy, differential scanning calorimetry, thermogravimetry and curing studies. The yields and properties of the polymeric fractions are compared to those of similar fractions obtained from preparation of PPS by solution polymerisation of copper(I) 4‐bromobenzenethiolate under conditions which correspond to those employed in this work.PPS was not produced, and BBD was almost quantitatively recovered when copper was absent from the reactants.Reactions performed using an equimolar ratio of copper to BBD produced PPS of molar mass approximately 2–4 × 103gmol−1in 76% yield after 8h reaction. However, this PPS was contaminated with an insoluble infusible material which had a deleterious effect on the physical properties of derived cured PPS materials. The yield of PPS decreased and the quantity of contaminant increased as reaction time increased.PPS of molar mass approximately 104g mol−1was obtained in 50–60% yield, free from insoluble infusible material, when the molar ratio of copper: BBD was increased to 2:1; it exhibited normal prop

ISSN:0007-1641    

DOI:10.1002/pi.4980220105

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe electrical conductivity and current‐voltage characteristics of pure and Fe3+‐doped polyvinyl acetate films have been studied for various temperatures and bias field strengths. The activation energy for conduction showed an increasing trend with increasing dopant concentration. This has been attributed to the formation of molecular aggregates. The variation of electrical conductivity for doped films with temperature showed three regions with different activation energies. This behaviour has been explained in terms of the type of conduction mechanism operating in the material. It has been suggested that at low temperatures the conduction is electronic while at high temperatures it appears to be ionic. As the dopant concentration increases ionic conduction tends to dominate the electronic conduction even at low temperatures. From the current‐voltage measurements it has been concluded that the conduction mechanism tends towards Schottky type with increasing dopant concentr

ISSN:0007-1641    

DOI:10.1002/pi.4980220106

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA method for the analysis of epichlorohydrin‐dimethylamine flocculants is presented. The method is applicable to concentrations of flocculant of between 2 and 60 parts per million. These concentrations are used in coal and other mineral processing operations. An extension of the method may be used to give semiquantitative estimations of higher concentration

ISSN:0007-1641    

DOI:10.1002/pi.4980220107

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe ylide‐initiated radical copolymerization of 4‐vinylpyridine (4‐VP) with methyl methacrylate (MMA) at 60°C using carbon tetrachloride as inert solvent yields non‐alternating copolymers. The kinetic parameters, average rate of polymerization (Rp) and orders of reaction with respect to monomers and initiator, have been evaluated and the kinetic equation is found to beRpα[ylide]0.94[MMA]1.0[4‐VP]1.5. The values of the energy of activation andkp2/ktare 48 kJ mol−1and 6.6 × 10−5litre mol−1s−1, respectively. The copolymers have been characterized by IR

ISSN:0007-1641    

DOI:10.1002/pi.4980220108

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo methods have been developed for the preparation of biaxially oriented poly(phenylene vinylene) from its poly(sulfonium salt) precursor. A two‐stage stretching process permits non‐equibiaxial stretching over a wide range of deformation ratios and a bubble expansion technique allows equibiaxial planar extension. The resulting films were examined using X‐ray diffraction prior to chemical doping with SbF5vapor. Biaxial orientation was shown to exert considerable influence over the attainable electrical conduct

ISSN:0007-1641    

DOI:10.1002/pi.4980220109

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTribromophenol copper(II) complexes with ligands such as pyridine and ethylenediamine are known to polymerize thermally. Generally, high temperature is required for thermal polymerization of such complexes. Thermal polymerization of trihalophenol copper(II) complexes in toluene has an induction period ofc.30 min. Electroinitiated polymerization of trihalophenol copper(II) complexes has also been accomplished recently using pyridine or ethylenediamine as ligands. However, the above mentioned copper(II) complexes cannot be polymerized electro‐chemically in acetonitrile. When pyridine and ethylenediamine are used as ligands, such complexes rapidly polymerize in acetonitrile without the passage of any current even at room temperature. Therefore, the electrochemical polymerization of trihalophenol copper(II) complexes with pyridine and ethylenediamine ligands must be carried out in dimethylformamide.In the present work, electroinitiated polymerization of bis(2,4,6‐tribromo‐phenoxo)‐N,N,N′,N′‐tetramethylethylenediamine copper(II) complex (TBPTD) was accomplished for the first time in acetonitrile. WhenN,N,N′,N′‐tetramethylethylene diamine is used as the ligand in the preparation of tribromophenol copper(II) complex it is found that acetonitrile can be used as solvent. This complex does not polymerize in acetonitrile without the application of potential.Electroinitiated polymerization of TBPTD was carried out by constant potential electrolysis, at each anodic peak potential of the complex. These potentials of TBPTD were measured, in advance, by cyclic voltammetry in acetonitrile.Electrolysis of TBPTD yielded polymers in the anode compartment only. Electroinitated polymerization of this monomer exhibited no induction period in contrast to the case of thermal polymerization.The reacted monomer concentration was simultaneously followed by cyclic voltammetry, in the same electrolysis cell. This process was accomplished by a specially designed H‐type cell equipped with six electrodes. Use of cyclic voltammetry for simultaneous in‐situ monitoring of reacted monomer concentrations was found to be more accurate, quicker and more reproducible than gas chromatography or spectroscopy.Polymers were characterized by FTIR,1HNMR, and13CNMR spectral analyses as well as measurement of molecular weight b

ISSN:0007-1641    

DOI:10.1002/pi.4980220110

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSteam explosion treatment was carried out on almost pure natural celluloses (wood pulps and purified cotton linter) to obtain alkali‐soluble cellulose and to clarify the effect of cellulose resources on the changes in morphology, viscosity‐average degree of polymerisationPv, solubility towards aqueous alkali solutionSa, and supermolecular structure of the celluloses. Soft wood pulp was most effectively treated in view of the changes in morphology andPv, but cotton linter was found to be resistant to the treatment. The degree of breakdown of intramolecular hydrogen bonding atC3andC6(Xam(C3) andXam(C6), respectively), as determined by solid‐state cross‐polarisation/magic angle sample spinning (CP/MAS) NMR, had a tendency to increase for soft wood pulp by the steam treatment employed here. Contrary to this, the crystallinity and the average crystal size estimated by X‐ray diffraction increased. Solubility of the treated wood pulps towards aqueous alkali solution can be improved to 100% when suitable conditions for the steam explosion are chosen to givePvless than 400 andXam(C3) greater than 44% andXam(C6) greater than 33%. Solid‐state NMR analysis may suggest that hydrogen bond formation at the C2hydroxyl group may first take place in the structural change of cellulose during the stea

ISSN:0007-1641    

DOI:10.1002/pi.4980220111

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY