摘要:

AbstractThe polymerization of several monomers, such as styrene, α‐methylstyrene, lactones, isobutyl vinyl ether, and hexamethylcyclotrisiloxane, was carried out in H‐shaped cells equipped with sacrificial anodes. The solvents, dichloromethane or nitromethane, contained tetrabutylammonium perchlorate playing the role of supporting electrolyte. Among the different metals tested (Cu, Ag, Hg, Al, Pb, Sn), only mercury and aluminium anodes gave initiation. The conditions of the electrolysis, the nature of the monomers, and the results of special experiments carried out in the presence of a hindered pyridine demonstrate that the polymerization involves the electrophilic addition of the active species to the monomer followed by cationic chain gr

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890701

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA series of aliphatic polymaleates was prepared by polycondensation of potassium maleate with α,ω‐dibromoalkanes Br(CH2)nBr (n= 1, 2, 3, 4, 5, 6, 8 and 10) in 1‐methyl‐2‐pyrrolidone. In practically all cases the formation of high‐molecular‐weight polyesters is accompanied by the production of substantial amounts of cyclic oligomers. This polycondensation reaction, carried out at moderate temperature, allows to obtain configurationally pure polymaleates. The resulting unsaturated polyesters are highly viscous liquids with glass transition temperatures below roo

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890702

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractLactic acid andN‐tert‐butoxycarbonyl protected L‐alanine, L‐histidine and L‐serine were condensed with syndiotactic poly(methacrylohydrazide)(1)in aqueous solution in the presence ofN‐ethyl‐N′‐(3‐dimethylaminopropyl) carbodiimide. By incomplete conversion of(1)copolymers4a – dwere obtained containing methacrylohydrazide monomeric units. By complete conversion with L‐histidine and L‐serine simultaneously, copolymers5containing both amino acid moieties were obtained. TheN‐tert‐butoxycarbonyl protecting group was removed from the polymers by acidolysis. This reaction was followed by CD spectroscopy. All polymers were characterized

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890703

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractABA type block copolymers composed of poly(γ‐benzyl L‐glutamate) (PBLG) as the A component and poly(propylene glycol) as the B component were obtained by polymerization of γ‐benzyl L‐glutamateN‐carboxyanhydride, initiated by amine groups at both ends of poly(propylene glycol). From circular dichroism measurements in ethylene dichloride solution as well as from infrared spectra measurements in the solid state, it was found that the polypeptide block exists in the α‐helical conformation, as in PBLG homopolymer. Wide‐angle X‐ray diffraction patterns for the block copolymers depend on the casting solvent and show basically similar reflections as th

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890704

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA series of chiral nematic copolymers were prepared based on the new mesogenic unitcis‐1,5‐cyclooctylene bis(p‐hydroxybenzoate) (COHB). The copolymers were prepared by linking COHB coupled with (+)‐3‐methyladipic acid to COHB units combined with terephthalic acid and its bromo and nitro derivatives. A biphasic region was observed in most of the samples which made phase diagrams more difficult to establish. Mesophase stability could normally be sustained up to 50 mol‐% content of the methyladipic acid group in the copolymer. They were also sensitive to both temperature changes and shea

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890705

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe shear viscosity of a moderately concentrated solution of the triblock copolymer polystyrene‐block‐polybutadiene‐block‐polystyrene is studied in a common solvent (1,4‐dioxane) and in so‐called selective solvents (mixtures of 1,4‐dioxane with different alcohols). In the latter, which dissolve only the styrene blocks and precipitate the butadiene blocks, the block copolymer molecules aggregate and form micelles with the precipitated blocks as the core and the dissolved blocks as the cilia. The micelle solutions exhibit non‐Newtonian behaviour over certain concentration ranges. The viscosity of the micellar solutions in the dilute regime is found to be lower than that of their unimer solutions (i. e., the viscosity measured in 1,4‐dioxane) at the same concentration, whereas at higher concentrations the situation is opposite. The viscosity of micellar solutions is first increasing and then decreasing with temperature for all selective solvents used. These variations with concentration and temperature are explained in terms of micelle structure, intermicellar entanglement, swelling of the inner core and coiling of

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890706

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractPolyurethane cationomers from poly(oxytetramethylene) of molecular weight 2000 as soft segments, 2,2′‐methyliminodiethanol as chain extender, glycolic acid as quaternization agent, and 4,4′‐methylenedi(phenyl isocyanate) (MDI) and hexamethylene diisocyanate (HDI) as diisocyanates are synthesized and characterized by using wide‐angle X‐ray diffraction, dynamic mechanical analysis, differential scanning calorimetry and tensile‐elongation testing. It is found that, in the unionized and ionized cases, the hard segments exhibit a disorder and short‐ and long‐range order, but no crystallinity. The ordered hard segments in the hard domains aggregate so tightly as to act as crosslinks, such that crystallization of soft segments occurs during elongation. Such disorder and order are also found to exist in the solutions of ethyl methyl ketone as reflected in variations of conductivity and viscosity during addition of water at 20°C. Ionization by insertion of the acid can disrupt the order in MDI and HDI systems, but can increase the cohesion between the neighbouring hard segments, the latter being predominant over the former. Dispersion is apt to disrupt the long‐range order in HDI systems but has only an insignificant effect on the

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890707

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThree kinds of MgCl2‐supported TiCl4catalysts (ester‐free, ethyl benzoate (EB, monoester) and dibutyl phthalate (DNBP, diester) as internal donors) were prepared. Polymerization of propylene was carried out using these catalysts with and without phenyltriethoxysilane (PTES) as an external donor. Significant differences were observed in the kinetic behavior of polymerization among ester‐free, monoester, and diester systems. Addition of PTES, however, did not change the kinetic behavior. The polymers produced were separated into three fractions by extraction with boiling heptane and octane, and the molar mass distribution (MMD) curves were measured for these three fractions. The heptane‐insoluble, isotactic polymer obtained in the absence of PTES was found to consist of two fractions, octane‐soluble and ‐insoluble. The octane‐soluble polymer having lower molar mass contained appreciable amounts of syndiotactic stereoblocks in the chains, whereas the octane‐insoluble polymer did not contain such stereoblocks. Addition of PTES drastically increased the octane‐insoluble fraction without changing the average molar mass. On the other hand, the MMD curve for the heptane‐soluble, atactic polymer gradually shifted to the lower molar mass range with an increase in the concentration of PTES. From these results, the effects of internal and external donors on catalyst activity and stereospecificity were discussed putting emphasis on the differences between mono

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890708

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe temperature changes caused by adiabatic pressure changes were studied in a polymersolvent system at high pressures. It is shown that the temperature determination by means of light scattering measurements is in good agreement with thermodynamic calculations of the temperature change for adiabatic pressure changes. The directly measured temperature changes by use of a thermocouple are found to be far too small.

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890709

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractBile pigments covalently anchored to beads of a polystyrene‐based resin show in gel‐phase13C NMR spectroscopy hydrogen‐bond interactions between the anchored groups. Such interactions are similar to those observed in homogeneous solution: attached 5(1H)‐pyrromethenones in aprotic solvents show dimer formation analogously to what happens in homogeneous s

ISSN:0025-116X    

DOI:10.1002/macp.1988.021890710

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY