摘要:

AbstractDielectric time domain spectroscopy measurements were performed on vinyl chloride/vinylidene chloride copolymers in solution over a frequency range of 1 to 104MHz. The dielectric absorption and dispersion have been studied at temperatures from −20°C to +20°C. The data were analyzed by using the Havriliak‐Negami equation and related to the motional behaviour. The dielectric correlation function was compared with those from different motional models used in NMR experi

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430501

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe supermolecular structure of uncoloured and mass coloured polyamide‐6 fibres has been investigated by means of SAXS and WAXS methods. Three different kinds of organic pigments have been used for the study. During fibre formation a crystalline lamellar structure is formed. The crystalline phase contains the α and γ modification. The pigment Copper Phthalocyanine Blue causes an increase of the content of the α‐form. During drawing of the fibres a recrystallization process occurs leading to changes of the structural parameters. These changes are independent of the presence of pi

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430502

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal decomposition of polypropylene fibres has been investigated on the basis of determining the TGA and DTGA curves at various heating‐up speeds in the temperature range from 100 to 600°C. The activation energyEas a kinetic parameter of the decomposition has been defined by means of theFlynn‐WallandFreeman‐Carrollmethods, respectively. It has been established that the activation energy necessarily grows with growth of the conversion

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430503

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractCellulose nitrate fibres of different degrees of substitution were analyzed by micro‐FTIR technique. A suspension of the fibres in Nujol resulted in improved recording conditions. An approach to quantification of the degree of substitution was reached by applying a deconvolution function to the absorbance range of the OH valency vibrations. The relative band height at 3500 to 3535 cm−1was found to be a measure of the nitration degree of cellulose fibres. The influences of the original cellulose as well as the kind of nitration and pretreatment on the spectra of individual fibres were stud

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430504

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractSulphation of cellulose was performed in an homogeneous aprotic system with SO3or CISO3H, resp., via O‐trimethylsilyl celluloses as reactive intermediates. Na‐cellulose sulphates completely soluble in water and showing small chain degradation could be obtained at DSs≥ 0.25. The DSsin the range between 0.2 and 2.5 as well as the distribution of the sulphate half‐ester groups within the AGU were regulated via the DSsiat one hand, the type and amount of sulphating agent at the other. Sulphation was performed either with the isolated and redissolved trimethylsilyl cellulose in N,N‐dimethylformamide or tetrahydrofurane, or starting with an activated cellulose suspension, by achieving silylation and subsequent sulphation in one system of reaction. Obviously, the silyl group acts as a reactive group in subsequent sulphation, and the sites previously silylated are preferentially sulphated in the subsequent step of reaction, and the DSsis limited by the degree of silylation (DSsi) previously obtained. The homogeneous sulphation of trimethysilyl cellulose indicates a reactivity of silyl ether groups in the order of C‐

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430505

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe structural changes during enzymatic hydrolysis of cellulose substrates were studied by SAXS, WAXS, water retention values, and degree of polymerization. LODP cellulose samples in original (cellulose I) and mercerized (cellulose II) form were hydrolyzed using a commercial cellulase preparation produced by the fungusTrichoderma reesei. The mercerization of the LODP‐cellulose I powder results in a remarkable increase in degradability due to a more finely dispersed void structure with a distinct higher specific inner surface of the cellulose II. Based on the course of the degree of crystallinity, lateral and longitudinal crystallite sizes, and the DP at different stages of degradation a supermolecular mechanism of the “all or nothing” type was found for the chains in LOPD‐cellulose I, whereas for cellulose II an endwise degradation of ordered regions has been co

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430506

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractHigh molecular weight (Mn>20000) phenylsubstituted poly(phenylene vinylenes) were prepared via the dehydrohalogenation route, starting from unsymmetrically substituted p‐xylene dichlorides. The detailed synthetic procedures are given for poly(1,4‐phenylene‐1,2‐diphenylvinylene)Tg= 250°C, poly[1,4‐phenylene‐1(4‐chlorophenyl)‐2‐phenylvinylene]Tg= 253°C, and poly[1,4‐phenylene‐1(4‐benzoylphenyl)‐2‐phenylvinylene]Tg= 223°C. All of these are thermostable polymers, which are soluble in common organic solvents and can be pro

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430507

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractDielectric relaxation measurements have been carried out in the frequency range from 1 Hz to 100 kHz on copolymers with different molar ratios of two liquid crystalline parts. Two dielectric relaxation ranges were detected which are related to the two respective parts. The copolymers show an increasing molecular mobility with respect to the homopolymers. The results are discussed in relation to the phase diagram and to dielectric data on low molecular liquid crystals.

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430508

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe influence of three aromatic rings in the azobenzene mesogenic moities on the LC character of side chain polymethacrylates is described. The three‐ring azobenzene groups exhibit some retardation and inhibition effect during the radical methacrylate polymerization. Therefore the polymerization conditions had to be modified. Dimethylformamide was found to be a solvent realizing high polymer yields and satisfactory molar masses. The phase behaviour of the obtained SCLC polymethacrylates and of their monomers is characterized by X‐ray, DSC and polarizing microscopy in dependence of spacer length. The polymethacrylates with three‐ring azobenzene mesogens show significant higher glass transition and clearing temperatures than two‐ring analogues. The change in the liquid crystalline phase arrangement from smectic C to smectic B with increasing spacer length is explained by the better movability of the m

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430509

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractDifferent types of latices were synthesized by emulsion copolymerization that differ in particle size, polymer hydrophilicity and surface coverage with functional groups. All of these particles were equipped with intensive fluorescence by inclusion polymerization, covalent bonding during particle formation and growth or surface modification of pre‐fabricated latices, respectively. Concentrated particle suspensions were injected into the brain tissue of mice. The filling of glial cells by phagocytosis and the retrograde labelling of neurons with two kinds of beads could be shown in brain section

ISSN:0323-7648    

DOI:10.1002/actp.1992.010430510

出版商:Akademie Verlag GmbH    

年代:1992

数据来源: WILEY