摘要:

AbstractSorption of several gases (He, N2, Ar, CH4, CO2, C2H6) was measured in an extended pressure range (up to 100 at m) in two glassy polyacetylenes: poly[1‐phenyl‐2‐(p‐tert‐butylphenyl)acetylene] and samples of poly[1‐(trimethylsilyl)‐1‐propyne](PTMSP), which were partly oxidized during long term storage in the ambient atmosphere. Sorption isotherms are concave to the pressure axis and can be described by the dual mode sorption model. Both polyacetylenes are distinguished by relatively large Langmuir sorption capacity parametersC′H. However, theC′Hvalues and solubility coefficients are significantly lower than t

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980601

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractIt has been recently reported that a simple chemical oxidation of 3‐alkoxy‐4‐methylthiophenes leads to highly regioregular polymers with enhanced electrical and optical properties. A joint experimental and theoretical study on different alkyl‐, alkylthio‐, and alkoxy‐substituted thiophenes and bithiophenes has revealed a strong correlation between the distribution of the unpaired electron π‐spin density in the oxidized starting compounds and the regionchemical structure of the resulting polymers. In particular, these calculations have clearly indicated that an asymmetric reactivity of the oxidized monomers or dimers at the 2‐ and 5‐positions can lead to polymers with a high head‐to‐tail content. This theoretical tool should be useful for the future design of regioregular and nonregioregular polymers from chemical or electrochemical oxidative po

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980602

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPolyacetylene can be solubilized by making copolymers with polyisoprene via anionic polymerization of isoprene using BuLi as the initiator, followed by Ziegler‐Natta copolymerization of acetylene onto the polyisoprenyllithium chains using either Ti(OBu)4or CoCl2. In the present study, the effects of temperature oncis‐transisomerization of the polyacetylene blocks and the phase behaviour of the PI‐PA copolymers in solution were investigated. We found that isomerization of thecis‐polyacetylene blocks in a solution of the PI‐PA copolymer is retarded by some intramolecular barriers, making thecis‐isomer rather stable. Reducing the temperature below about 12°C was found to cause a phase transformation from the worm‐like structure to spherical micell

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980603

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractDynamics in solution and photochromic properties of radical copolymers of (S)‐4‐[N‐(2‐methacryloyloxyethyl)‐N‐(2‐methylbutyl)]amino‐4′‐cyanoazobenzene with butyl methacrylate were investigated.13C NMR and 2D heteronuclear correlated (HETCOR) spectroscopy allowed assignment of13C NMR signals and evaluation of main chain tacticity.13C relaxation timesT1evidenced a rather limited mobility of azobenzene chromophores. Mobility increases with increasing content of butyl methacrylate units, that acts as an internal plasticizer. The limited mobility of the spacer between azobenzene and methacrylate groups is attributed to an interaction between carbonyl oxygen and aminic nitrogen stabilized by the internal charge transfer from the amino to the cyano group.Transtocisphotoisomerization rates turned out to be independent of molecular weight and chemical composition of the investigated photochromic polymers, whereascistotransthermal isomerization rates increase with the content of aromatic units. These data suggest that photo‐ and thermal isomerization processes imply an in‐plane inversion and an out‐of‐plane rotation of one of the phenyl rings of the azobenzene chromophores, respectively. Preliminary second harmonic generation measurements indicate that the investigated polymers are endowed with significant no

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980604

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractZn(II)L‐lactate (ZnLac2) was prepared either from ZnO and ethylL‐lactate or with slightly higher optical purity from ZnO andL‐lactide. Using water‐free ZnLac2L‐lactide was polymerized in bulk at 120°C or 150°C. Higher yields and higher molecular weights were found at 150°C. The highest number average molecular weights (M̄naround 70 000) were obtained at monomer/initiator (M/I) ratios of 4000. Despite the high reaction temperature the isolated poly(L‐lactide)s were 100% optically pure. Analogous polymerizations were also conducted with Zn(II)L‐mandelate or Zn(II) stearate with inferior results. Poor yields and molecular weights were found, when zinc glycolate salt was used as catalyst. Furthermore, numerous polymerizations were conducted with ZnCl2, ZnBr2or ZnI2as initiators. Again poly(L‐lactide)s with 100% optical purity were isolated, but most molecular weights were lower and never higher than those obtained with ZnLac2. Therefore, ZnLac2proved to be the most favorable and fully resorbable (biocompatible) initiator of this study. Finally, the combination of ZnLac2with a primary alcohol, which plays the role of a coinitiator, allows a broad variation of the molecular weight and the introduction and modification of an ester endgroup. This approach also allows the incorporation of bioactive alcohols such as α‐tocopherol, stigmasterol or testosteron in the form of covalently

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980605

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractCommercial FeCl2and Fe(II) glycolate, Fe(II)L‐lactate or Fe(II)L‐mandelate were used as initiators for the polymerization ofL‐lactide. All polymerizations were conducted in bulk at 150°C, because no conversion was observed in bulk at 120°C. The Fe(II) lactate was found to be more reactive than FeCl2, and it yielded slightly higher molecular weights than all other initiators. Under the optimum conditions, viscosity average molecular weights (M̄v) around 50 000 and yields above 90% were obtained. However, slight racemization (2–5%) of the isolated poly(L‐lactide) was also observed under most circumstances. Characterization of unreacted monomer proved that the racemization mainly involves the monomeric lactide due to its higher

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980606

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe reaction of the potassium salt of acrylic acid with the potassium salt of a dicarboxylic acid and 1,4‐dibromobutane was applied to the synthesis of three series of acrylate‐terminated copolyesters: poly(tetramethylene maleate‐co‐tetramethylene phthalate) (BMPA), poly(tetramethylene fumarate‐co‐tetramethylenephthalate) (BFPA) and poly(tetramethylene phthalate‐co‐tetramethylene succinate) (BPSA). The monofunctional monomer, the potassium salt of acrylic acid, was used for the introduction of double bonds at the end of the chains and for the regulation of the molecular weight of the polyesters. The telechelic copolyesters were characterized by1H and13C NMR spectroscopy, in almost all cases providing an acrylate funct

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980607

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractTwo new ethylene ionomers were synthesized, poly[ethylene‐co‐(5.4‐mol‐% 2‐(4‐carboxyphenoxy)ethyl methacrylate)] partially neutralized with Zn(II) (EMAA‐BZnX), and poly[ethylene‐co‐(5.4 mol‐% 2‐(3‐carboxypyridin‐6‐yloxy)ethyl methacrylate)] (EMAA‐N) and its hydrochloride (EMAA‐NHCl). Differential scanning calorimetric (DSC), X‐ray diffraction, and dielectric and dynamic mechanical relaxation studies were made for the two ionomers to investigate the formation and structure of ionic aggregates. In EMAA‐BZnX, DSC, dielectric and dynamic mechanical data suggest the formation of ionic aggregates in the neutralization range above 40%; X‐ray diffraction data, however, did not show any ionic peak, while the ionic groups were not aggregated at all in EMAA‐NHCl. From these results, the ion‐aggregation in ionomers is discussed with respect to chemical

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980608

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractSix 1,3,4‐oxadiazole‐containing polyethers with reduced viscosities of 0,65–1,17 dL · g−1were synthesized by high‐temperature solution polycondensation of an activated difluoride, 2,5‐bis(4‐fluorophenyl)‐1,3,4‐oxadiazole, with aromatic diols possessing a variety of ring structures. The expected chemical structures were confirmed by IR and1H NMR spectroscopy and elemental analysis. Of all the polymers, two polyethers were highly crystalline and soluble only in limited solvents such aso‐chlorophenol and conc. sulfuric acid. The other polyethers were amorphous and dissolved readily in a variety of organic media including polar aprotic solvents, phenols and chlorinated hydrocarbons. Colorless to slightly yellow‐colored, transparent and tough films could be cast from theN‐methyl‐2‐pyrrolidone oro‐chlorophenol solutions. The mechanical properties were excellent and their tensile strength, elongation at break and tensile moduli were in the ranges of 53–80 MPa, 4–12% and 1,3–2,0 GPa, respectively. The amorphous polyethers had high glass transition temperatures of 195–259°C. All the polyethers were highly thermally and thermooxidatively stable and exhibited no weight loss up to 400°C, with 10% weight

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980609

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractBioanalogous organic polyphosphates (PP) and polymer ion‐exchange membranes (IEM) were used to arrange a membrane system for the transportation of Zn(II), Mn(II), Cu(II), Co(II) and Ni(II) ions. The system consists of three membranes separating a feed and a strip solution with metal sulfates and sulfuric acid, respectively:\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm MSO}_4 \left| {{\rm IEM}} \right|{\rm Liquid\; membrane \;with \;PP}\left| {{\rm IEM}} \right|{\rm H}_{\rm 2} {\rm SO}_{\rm 4} $\end{document}Poly(trimethylene phosphate), α‐hydroxy‐ω‐(2‐ethylhexyl)poly(trimethylene phosphate), poly(1,2‐glycerol phosphate) and poly(2,3‐acetoxyglycerol phosphate) were used as ionic carriers for mimicking some transport functions of natural teichoic acids. These polyelectrolytes were found to facilitate the exchange‐diffusion process of heavy metal ions and to exhibit fluxes in the range 3,5 · 10−9– 6 · 10−9mol M(II)/(cm2· s). The specific stationary fluxes typically change in the orderJCu>JCo>JNi>JMn>JZn. The observed transport preference is consistent with the affinity order of teichoic acids or the bacteria cell wall toward

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980610

出版商:Wiley‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY