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  • 1
    Electronic Resource
    Electronic Resource
    Hyperbranched Aliphatic Polyesters (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 1698-1703 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00109a049
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  • 2
    Electronic Resource
    Electronic Resource
    Nonlinear optical properties of a channel waveguide produced with crosslinkable ferroelectric liquid crystals (2000)
    Springer
    The European physical journal 3 (2000), S. 245-251 
    Details
    ISSN: 1292-895X
    Keywords: PACS. 61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order - 42.65.Ky Harmonic generation, frequency conversion - 42.82.Et Waveguides, couplers and arrays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability which did not show any sign of degradation within the monitored period of several months. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. The alignment led to an inherent channel waveguide for p-polarized light without additional preparation steps. The photopolymerization did not induce scattering sites in the waveguide and the normalized losses were less than 2 dB/cm. The material offers a great potential for the design of nonlinear optical devices such as frequency doublers of low-power laser diodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101890070016
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  • 3
    Electronic Resource
    Electronic Resource
    Miscibility assessment and thermal oxidative stability of blends of branched polyethylene and poly(1,2-butadiene) (1994)
    Springer
    Polymer bulletin 32 (1994), S. 687-692 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(1,2-butadiene) promotes crosslinking of branched polyethylene, which indeed indicates partial miscibility of the two polymers. Dynamic mechanical spectroscopy and transmission electron microscopy of blends of branched polyethylene and poly(1,2-butadiene) indicated that the polymers are partially immiscible even in the blend with only 3% of poly(1,2-butadiene). The thermal oxidative stability at temperatures above the melting point of samples stabilized with antioxidants was essentially unaffected by the percentage concentration of poly(1,2-butadiene), whereas the stability towards external partial discharges was lower in crosslinked polyethylene blends containing poly(1,2-butadiene) than in pure crosslinked polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973920
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  • 4
    Electronic Resource
    Electronic Resource
    Relaxation processes in hyperbranched polyesters (1994)
    Springer
    Polymer bulletin 32 (1994), S. 679-685 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Dielectric permittivity and loss have been measured over the frequency range 10-2 Hz-10 kHz between 100 K and 350 K for samples of 50/50 mixtures of each of two hyperbranched polyesters, one five-generation hydroxy functional (5G-OH) and one threegeneration alkyl-terminated polymer (3G), with dielectrically inactive linear polyethylene. The thermal transitions of the hyperbranched polymers were studied with differential scanning calorimetry. Three relaxation transitions were found in 5G-OH: α, the glass-rubber transition and two subglass processes denoted β and γ showing Arrhenius temperature dependence both with an activation energy of 96±2kJ mol-1. The low temperature process could be assigned to motions of the terminal hydroxyl groups whereas β is due to reorientation of the ester groups. Sample 3G showed only a glass transition and one subglass process being assigned to reorientation of the ester groups. The high activation energy (202 kJ mol-1) of this process indicates that the ester groups are highly constrained in this polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973919
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular engineering of liquid crystal polymers by living polymerization (1991)
    Springer
    Polymer bulletin 25 (1991), S. 115-121 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The synthesis of 11-[(4′-methoxy-4-biphenyl)oxy]undecanyl vinyl ether (4), 11-[(4′-nitro-4-biphenyl)oxy]undecanyl vinyl ether (13), 11-[p(4-cyanophenylbenzoate)oxy]undecanyl vinyl ether (17) and 3-[2-[1,2,2-trifluoroethoxy]-2-(4-methoxy-4-(α-methylstilbene)oxy]-1-(trifluoromethyl) trifluoroethoxy)-1-[2-(ethyloxy)ethoxy]-2,2,3,3-tetrafluoropropane (22) and their cationic polymerization with the initiating system H2O/AIEtCl2/(CH3)2S is described. All the functional groups available in these monomers, i.e., nucleophilic aromatic groups, nitro and cyano groups, aromatic esters, double bonds and acidic protons are tolerated by this polymerization technique. The resulting polymers exhibit narrow molecular weight distribution and display mesomorphic behavior. With the exception of poly(4) which exhibits a monotropic sA mesophase, all other polymers display an enantiotropic sA mesophase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338908
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetics of isotropic-smectic phase transitions in a liquid-crystalline polyether with a methylene spacer of 12 carbons (1991)
    Springer
    Polymer bulletin 27 (1991), S. 315-322 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The isotropic-smectic (sB or sG) mesophase transition in a thermotropic main chain polyether based on bis(4-hydroxyphenoxy)-p-xylene with a methylene spacer having 12 carbons has been studied by polarized light microscopy and differential scanning calorimetry. The apparently nucleation-controlled transition followed the general Avrami equation with an exponent value between 2.5 and 3.2. The smectic domains grow more rapidly along the chain axis than in the perpendicular direction. The growth rate exhibited the following temperature (T) dependence: $$G = G_0 \exp \left( {\frac{{ - Kg}}{{T(T^ \circ _i - T}}} \right)$$ where Go and Kg are constants and To i is the equilibrium clearing temperature. A second Arrhenius-activated process was evident at high temperatures. The data presented in this paper are critically compared with data previously reported for similar main-chain polyethers with methylene spacer groups having 9 and 11 carbons in order to reveal possible odd-even effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294538
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  • 7
    Electronic Resource
    Electronic Resource
    Cationic bulk polymerization of mesogenic vinyl ethers induced by thermal decomposition of sulfonium salts (1991)
    Springer
    Polymer bulletin 25 (1991), S. 649-656 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Liquid crystalline vinyl ethers have been bulk polymerized cationically in the mesophase using onium salts for thermal initiation. High molecular mass polymers (Mn≤83 000) with a narrow molecular mass distribution (around 2) were produced at very high temperatures (≤120°C). Apparently the polymerization system stabilizes the propagating cation and thus reduces chain transfer reactions that are determining the molecular mass. Possible reasons for this stabilization are e.g. influence of the mesophase of the formed polymer, interfacial polymerization, and nucleophilic stabilization by nucleophiles present in the monomer or produced by the initiators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032660
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of poly(11-(4′-cyano-trans-4-stilbenyloxy)undecanyl vinyl ether) (1992)
    Springer
    Polymer bulletin 28 (1992), S. 267-274 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymers based on 11-(4′-cyano-trans-4-stilbenyloxy)undecanyl vinyl ether have been synthesized by living cationic polymerization, photo-initiated cationic polymerization using onium salts and thermal initiated cationic polymerization using onium salts. The polymers have been characterized by size exclusion chromatography, nuclear magnetic resonance spectroscopy, differential scanning calorimetry and polarized light microscopy. Living cationic polymerization resulted in a polymer of low molecular mass Mn≤3 600, with a uniformity index (D) of 1.2 displaying a focal conic texture indicative of smectic A (sA) phase with preserved cyanogroup and trans-configuration. Photo-initiation using 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide and diphenyliodonium hexafluorophosphate resulted in an insoluble polymer exhibiting only vague liquid crystalline textures. Initiation with phenothiazine and phenacyltetramethylenesulfonium hexafluoroantimonate also yielded a partly insoluble polymer with a disturbed sA phase. It is suggested that the monomer and polymer are sensitive towards radicals leading to cross-linking and branching. The thermal initiation on systems with α-methylbenzyltetramethylenesulfonium hexafluorophosphate and p-methoxybenzyltetramethylenesulfonium hexafluorophosphate resulted in completely soluble mesomorphic polymers of Mn≤13 000, D=1.7 and Mn≤26 000, D=2.8 respectively, in both cases with a preserved cyanogroup and a transconfiguration. Polarized light microscopy revealed a distinct focal conic structure indicative of sA in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294821
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  • 9
    Electronic Resource
    Electronic Resource
    Photoinitiated cationic bulk polymerization of mesogenic vinyl ethers (1991)
    Springer
    Polymer bulletin 25 (1991), S. 641-648 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Mesogenic vinyl ethers have been bulk polymerized cationically in the liquid crystalline phase, using onium salt redox systems for photochemical initiation. High molecular mass polymers (Mn≤41 000) with a narrow molecular mass distribution (around 2) were obtained at high temperatures (≤80°C). Apparently the polymerization system stabilizes the propagating cation and thus reduces the tendency for chain transfer to occur. Highly ordered thin (30–50 μm) films were produced by the polymerization of monomers oriented in their nematic phase. Despite the fact that they were in the sA phase, the films were completely transparent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032659
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  • 10
    Electronic Resource
    Electronic Resource
    Smectic A organisation in copolymers of i-butyl vinyl ether and 11-[(4′-cyano-4-biphenyl)oxy]undecanyl vinyl ether as assessed by X-ray scattering (1995)
    Springer
    Polymer bulletin 35 (1995), S. 629-634 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Liquid crystalline copoly(vinyl ether)s based on i-butyl vinyl ether and 11-[(4′-cyano-4-biphenyl)oxy]undecanyl vinyl ether of various compositions were synthesized. The copolymers exhibited smectic A mesomorphism with a layer thickness strongly increasing with increasing i-butyl vinyl ether content. The intermesogenic distance remained unchanged. A model of the layer structures is given based on structural assessments from small-angle X-ray scattering data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324118
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