摘要:

AbstractThe formation process and morphology of polyethylene (PE) produced by the non‐porous catalyst species tufa‐ and kaoline‐supported Cr(C5H5)2, Zr(BH4)4and TiCl4were studied by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The PE morphology was found to depend upon the catalyst active component composition, the polymer yield and the morphology of the support. A quantitative estimation of the PE coverage of the catalyst particles w

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890801

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

Abstract1,3‐Di(2‐thienyl)benzene (T13B), 4,4′‐di(2‐thienyl)biphenyl (TBP), and 3,5‐di(2‐thienyl)‐pyridine (T35P) were prepared. Films were deposited on the electrode in the anodic oxidative polymerization of T13B, 1,4‐di(2‐thienyl)benzene (T14B) and TBP, but the oxidation product of T35P did not cover the entire surface of the electrode. The infrared spectra of the films indicated oxidative coupling to occur at the 5 and 5′ positions of the thiophene rings. While the cyclic voltammograms of poly‐T14B were well‐defined, those of poly‐T13B and poly‐TBP had complex shapes with two or three anodic peaks. When the absorption spectra were measured during electrochemical oxidation, new peaks appeared at 2,0 and 1,9 eV for poly‐T13B and poly‐TBP, respectively. The films looked green in the oxidized state and faintly yellow in the neutral state. The green colour was retained without applied voltage in the cell and in the dry state. It was concluded that conjugation along the main chain

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890802

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe polymerization of 2‐methoxy‐2‐oxo‐1,3,2‐dioxaphospholane (1), initiated with aluminium triisopropanolate in CH2Cl2as solvent, was studied. Under the chosen conditions one molecule of initiator produces one polymeric chain. At low conversion exclusively linear chains of poly[oxy(methoxyphosphoryl)oxyethylene] [poly(1)] are formed. Later, chain transfer to polymer leads to extensive branching. Kinetic studies strongly indicate propagation on covalent active species. Rate constants of initiation and propagation, found from non‐stationary kinetics at 25°C, are equal to 6,5 · 10−3mol−1· 1 · s−1and 4,5 · 10−1mol

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890803

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe reaction conditions influencing the carbonyl‐olefin exchange reaction were studied. It could be established that highest yields and molecular weights are obtained for a mole ratio catalyst/monomer of 1 : 1, the former being introduced in several portions. The observed slowdown of the reaction is explained by deactivation of WCI6, due to complex formation with the resulting polymer. Increase of solvent polarity, temperature and duration also leads to higher yields and molecular weight

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890804

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractChiral combined liquid‐crystalline polymers (i. e. polymers with the mesogenic groups in the main chain as well as in the side groups) with dipole moments perpendicular to the mesogenic groups were synthesized and characterized. These dipole moments were introduced by lateral substituents, which were located at different parts of the mesogen or directly at the chiral centre. The polymers, thus prepared, show crystalline or glassy phases at room temperature and smectic A, chiral smectic C*or cholesteric phases at higher temperatures. Since the lateral substituents decrease the melting temperature more strongly than the clearing temperature, the liquid‐crystalline phases are broadened compared to the unsubstituted polymers. Often glassy liquid‐crystalline phases are obtained. The dipole moments perpendicular to the mesogenic groups or at the chiral centre may help to obtain a high spontaneous polarisation in the chiral smectic C*phase (ferroelectri

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890805

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe possibility of preparing a polyoxyethylene derivative containing only one active group per chain, and with a narrow distribution of molecular size, was investigated. The aim of this investigation was to obtain a polymeric derivative of benzenehexacarboxylate (BHC) capable of interacting specifically inside the polyphosphate binding site of human hemoglobin (Hb) and which, after covalent coupling with this protein, could lead to conjugates with well‐defined oxygen‐binding properties. Such conjugates could be of interest in the field of blood substitutes. To minimize the percentage of high‐molecular‐weight products resulting from the fact that, on one hand, commercial monomethoxypolyoxyethylene (MPOE 5000) contained a considerable amount of difunctional and high‐molecular‐weight species, and on the other hand that several reactions were likely to lead to cross‐linked products, fractionation steps and/or chromatographic steps were carried out. The final compound obtained under these conditions (83,5% of BHC‐mono substituted polyoxyethylene, 8,5% of BHC disubstituted and 8% MPOE) was found to interact with the polyphosphate binding site of Hb, as it was capable of lowering its affinity for oxygen. After covalent coupling with deoxy‐Hb under defined conditions, this effect was strengthened, which means that the binding was probably formed with an amine of the Hb polyphosp

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890806

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe steady state of reversible polymer‐analogous reactions was simulated by Monte Carlo calculations. The length of the simulated copolymer chains was chosen large enough to yield data with an acceptable degree of statistical fluctuation. Two types of sets of relative rate constantsKwere investigated, firstK1=K2=K3, and secondK1≠K2,K1≠K3,K2≠K3, withK1·K3=K22. The relative rate constantsKare defined asK1=k(AAA)/k(ABA),K2=k(AAB+)/k(ABB+), andK3=k(BAB)/k(BBB), wherekis the ordinary rate constant pertaining to the reaction of the central monomeric unit in the triad given in parentheses, with two different types of monomeric units A and B in the binary copolymer. For both types of sets of relative rate constants the simulation showed a detailed balance to prevail for the kinetics in the steady state. It was also shown that the same kinetics and statistics were obtained in the steady state when starting the simulation first from a homopolymer consisting of A‐monomeric units, and then from a homopolymer of B‐monomeric units. Based on the finding of a detailed balance and on the definition ofK, it could be shown by analysis that the first type of the sets ofKleads to a Bernoullian statistics of the copolymers in the steady state, while the second type leads to a first‐order Markov statistics. Correspondingly, equations are given which allow to calculate the relative rate constants from statistics and vice versa. The equations have also been confirmed by Monte Carlo simulation. In addition, the equations for the interrelations between the standard Gibbs free energies of the individual reactions for the central units in the tr

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890807

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractCyclopolymerizations ofN‐allylmethacrylamide(1a)andN‐allylacrylamide(1b)are conducted over the temperature range below and above the ceiling temperature (Tc) ofN‐propylmethacrylamide(2a),one of the monofunctional counterparts of1a. Increasing the polymerization temperature extensively enhances the cyclopolymerizability of1aat temperatures in the vicinity of theTcof2a,while the cyclopolymerizability of1bincreases slightly with temperature. The polymerization tendency ofN‐propylacrylamide(2b),one of the monofunctional counterparts of1b,is lying high above the temperature range investigated and both monoallyl counterparts of1aand1bshowed similar polymerizabilities. The differences between the cyclopolymerizabilities of1aand1bare interpreted by applying the hypothesis that the lower the polymerizability of the corresponding monofunctional counterparts of the unconjugated dienes, the higher their cyclopolymerizabilities. Another point focused on the reversibility of intramolecular cyclization, because polymerization of1awas carried out in the vicinity of theTcof2a. It appears that the cyclic structure of poly(1a)consists exclusively of a 5‐membered ring whereas poly(1b)contains 5‐ and 6‐membered rings. The polymerization temperature does not affect the proportion of these two cyclic structures for both polymers. These results suggest that reversibility of intramolecular cyclization need not be taken into consideration to explain the cyclopolymerization behav

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890808

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe 125 MHz13C NMR spectra of some poly(dialkyl fumarates) (PDAF) and poly(dicycloalkyl fumarates) (PDCF) prepared by radical polymerization are measured in CDCl3solution at 60°C. The multiplet resonances of the main‐chain carbon atoms and the ester carbonyl carbon atoms are assigned to stereochemical triad and pentad sequences, respectively, using model compounds as well as computer simulation. From these results it is found that PDAF and PDCF exhibit essentially atactic structures with meso addition favoured over racemic addition, and that the ratio of meso to racemic content varies with different kinds of alkyl and cycloalkyl groups. The tactic sequence proportions of the polymers cannot be explained by one‐parameter Bernoullian statistics, but can be successfully explained by modified Bernoullian t

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890809

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractInverse gas chromatography technique was applied to the study of the miscibility of the system polystyrene/poly(methyl vinyl ether) (PS/PMVE) over a temperature range (75 – 155°C) including the phase separation temperature. This temperature was measured taking into account the retention diagrams of the PS/PMVE system with several probes, the comparison of the probe retention volumes in the blend with the algebraic average retention volumes of the pure homopolymers, and the variation of interaction parameter χ′23with temperature within the temperature range investigated. According to these criteria, the phase separation temperature of the PS/PMVE (50/50 by wt.) system is within the temperature range of 115

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890810

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY