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  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1465-1471 
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This article describes the synthesis and second-order nonlinear optical (NLO) properties of polyamides containing an alternating arrangement of cholesteryl or menthyl moieties and an NLO-phore, i.e., N,N-dialkyl-4-nitroaniline, in the side chain. The polyamides were prepared by condensation polymerization of 5-[2-(N-methyl-4-nitroanilino)ethoxy]isophthaloyl chloride with cholesteryl (P1) or L-menthyl (P2) 3,5-diaminobenzoate. The resulting polymides P1 and P2 exhibit high glass transition temperatures (Tg) around 200°C and good solubilities in common organic polar solvents. Optical-quality films of P1 and P2 were obtained by spin-coating. The second harmonic generation (SHG) measurements of the spin-coated films of P1 and P2 were carried out by the Maker fringe method using a Q-switched Nd:YAG laser (1064 nm) as exciting beam after corona-poling; they indicate that P1 and P2 exhibit a second-order NLO coefficient, d33, of 10 pm/V. The orientational behavior of the NLO-phores in P1 is specific for the poling process. A noncentrosymmetric alignment of the NLO-phores in P1 was induced by corona-poling at a temperature lower than Tg, i.e. at 100°C. Additionally, it was found that the noncentrosymmetric alignment of NLO-phores in P1 is inhibited over 160°C due to the para-crystalline aggregation of cholesteryl moieties as deduced from the SHG measurements and X-ray diffraction analysis.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1857-1863 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Chemical structures of cellulose and chitosan dissolved in trifluoroacetic acid (TFA) and those of cellulose and chitosan films cast from their TFA solutions were studied by 13C-NMR and infrared (IR) spectroscopy. Cellulose is trifluoroacetylated selectively at the C6-hydroxyl groups in the TFA solution, and chitosan is dissolved in TFA by forming amine salts with TFA at the C2-amine groups. IR analyses of cellulose films cast from its TFA-acetic acid solutions showed that partly trifluoroacetylated cellulose in the solution state turns to partly acetylated cellulose in the solid state during evaporation of the solvents in air by the ester interchange. Chitosan films cast from its TFA-acetic acid solutions still have the amine salts with TFA. These acetyl groups in cellulose films and TFA in chitosan films are removable by soaking the films in 1N NaOH at room temperature for 1 day.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1873-1879 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Interactions between cellulose and chitosan molecules in cellulose-chitosan blend films, prepared using trifluoroacetic acid as a cosolvent for the two polysaccharides, were studied by X-ray diffraction and Raman analyses and by measurements of mechanical properties of the blend films. Crystallinity of cellulose in the blend films decreased with an increase in chitosan content. The blend films had tensile strengths of 45-100 MPa and Young's moduli of 2-7.5 GPa in dry states. These values had the maximum around 30% chitosan content in the blend films. These results suggested the presence of interactions between cellulose, chitosan, and water molecules in the films. However, Raman analysis suggested that cellulose and chitosan molecules in the blend films seemed to have the same secondary structures as those in 100% cellulose and 100% chitosan films, respectively. Thus, these results indicate the presence of interactions in the interfacial region between small domains of cellulose and chitosan. The presence of chitosan molecules may lead to decrease in the domain size of cellulose, and to increase in the interfacial region between cellulose and chitosan domains.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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