ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    New polymer syntheses. XCVII. Hyperbranched LC-polyesters based on β-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1397-1405 
    Details
    ISSN: 0887-624X
    Keywords: hyperbranched polyesters ; nematic phase ; phloritic acid ; vectra ; melt rheology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two classes of liquid crystalline hyperbranched copolyesters were prepared by the copolycondensation of silylated 3,5-bis(acetoxy)benzoic acid with mixtures of mesogenic difunctional monomers. The first class of LC-copolyesters was obtained from 1 : 1 mixtures (molar ratio) of silylated β-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid (poly(HPPA/HBA)). The second class of LC-copolyesters was obtained by additional copolycondensation of silylated 6-acetoxy-2-naphthoic acid. The hyperbranched copolyesters of this ternary system poly(HPPA/HBA/HNA) proved to be less crystalline in contrast to the binary system. In both classes of LC-copolyesters the degree of branching was varied via the feed ratio of 3,5-dihydroxybenzoic acid. A minimum segment length of 6 difunctional monomer units between the branching points is required to establish a nematic phase. However, a greater segment length is needed to obtain a homogeneous LC-phase. The poly(HPPA/HBA) copolyesters were also characterized by melt rheology. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1397-1405, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    New polymer syntheses. XC. A-B-A triblock copolymers with hyperbranched polyester A-blocks (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 31-38 
    Details
    ISSN: 0887-624X
    Keywords: triblock copolymers ; polycondensations ; telechelic character ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Telechelic oligo(ether-ketone)s containing two trimethylsiloxy end groups and one methyl group per repeating unit were prepared by polycondensation of 4-fluoro-2′-methyl-4′-(trimethylsiloxy)benzophenone. The telechelic character was achieved by cocondensation of a small amount of silylated bisphenol-P. The end groups of the silylated oligo(ether-ketone)s were acetylated by means of acetyl chloride. On the basis of 1H-NMR end group analyses two samples of α,ω-bis(acetoxy) oligo(ether-ketone)s with DP = 14 and DP ∼ 28 were obtained. These oligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5-bis(acetoxy)benzoic acid were polycondensed at 270°C in bulk. The resulting A-B-A triblock copolymers were fractionated by dissolution in tetrahydrofuran. In three out of four experiments a small fraction of precipitated material rich in oligo(ether-ketone) was isolated. The purified triblock copolymers were characterized by inherent viscosities and NMR spectra. For those samples containing the long oligo(ether-ketone) block a low degree of crystallinity was observed after annealing. Four additional polycondensations were conducted with an initial reaction temperature of 290°C. In this way a completely soluble and amorphous triblock copolymer was obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 31-38, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    New polymer syntheses. XCVI. Star-shaped LC-polyesters derived from β-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1387-1395 
    Details
    ISSN: 0887-624X
    Keywords: star-shaped polyesters ; nematic phase ; phloritic acid ; spirobis indane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Star-shaped polyesters were prepared by polycondensation of tetraacetoxyspirobis(indane) and a 1 : 1 mixture of silylated β-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid. The lengths of the star arms were systematically varied, and the influence of the star center on the stability of the nematic phase was studied. It was found that on the average more than 10 monomer units per star arm are required to stabilize a homogeneous LC-phase. Furthermore, a second class of star-shaped polyesters consisting of β-(4-hydroxyphenyl)propionic acid (HPPA), 4-hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) was prepared. This ternary copolyester proved to reduce the crystallinity but to stabilize the LC-character. A homogeneous nematic melt was obtained with 6 monomer units per star arm. This interpretation is based on optical microscopy which provides a static picture of the biphasic situation. Therefore, a preliminary study of the melt rheology was included, which proved that the typical LC-character of the melt was detectable ateven shorter star arms due to the shear orientation. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1387-1395, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    New polymer syntheses XCIII. Hyperbranched homo- and copolyesters derived from gallic acid and β-(4-hydroxyphenyl)-propionic acid (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2347-2357 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hyperbranched homopolyester of gallic acid (GA) was prepared by polycondensation of acetylated gallic acid in bulk. Copolyesters of gallic acid and 3-hydroxybenzoic acid (3-HBA) or β-(4-hydroxyphenyl)propionic acid (HPPA) were prepared via the silylated monomers. The degree of branching was varied in both series via the molar fraction of gallic acid. A model reaction with silylated 4-methoxybenzoic acid suggests that all three acetoxy groups of gallic acid can react by ester interchange reactions under the chosen reaction conditions. Furthermore, highly branched copolyesters derived from equimolar ratios of HPPA and 2-, 3-, or 4-hydroxybenzoic acid, vanillic acid, or 4-hydroxycinnamic acid were synthesized. All these copolyesters were found to be amorphous with glass transition temperatures (Tg's) far below that of the hyperbranched poly(gallic acid). © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2347-2357, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    New polymer syntheses, 91Part 90: H. R. Kricheldorf, T. Stukenbrock, J. Polym. Sci., Part A: Polym. Chem. in print.. Hyperbranched poly(ester-amide)s derived from 3,5-dihydroxybenzoic acid and 3,5-diaminobenzoic acid (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2651-2666 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new pentafunctional monomer (3a) was prepared by acylation of silylated 3,5-diaminobenzoic acid (DABA) with 3,5-bisacetoxybenzoyl chloride. The polycondensation of this monomer or its trimethylsilyl ester yielded a hyperbranched poly(ester-amide) having a nearly alternating sequence of one DABA and two 3,5-dihydroxybenzoic acid (DHBA) units. However, due to ester-amide interchange reactions, ca. 15-25% of the DABA units lose their role as branching units. When 3,5-bisacetoxybenzoic acid and 3,5-bisacetamidobenzoic acid were copolycondensed in a 2:1 ratio, the resulting polymer and endgroup structures were different. Furthermore, hyperbranched copoly(ester-amide)s with a variable DHBA/DABA ratio from 10:0 down to 3:7 were prepared. The glass transition temperature (Tg) increased by approx. 90°C (up to 250°C) at higher molar fractions of DABA. Furthermore, monomer 3a was copolycondensed with 3-acetoxybenzoic acid or its trimethylsilyl ester. The resulting copoly(ester-amide)s were again amorphous, showing a continuous decrease of the Tg down to the value of the poly(3-hydroxybenzoic acid) (poly(3-HBA)) around 136-140°C.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980902
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    New polymer syntheses, 92.Part 91: cf. ref.19 Biodegradable, thermotropic copolyesters derived from β-(4-hydroxyphenyl)propionic acid (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 3753-3767 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Binary copolyesters were prepared by polycondensation of the trimethylsilylester of acetylated β-(4-hydroxyphenyl)propionic acid (HPPA) with acetylated 4-hydroxybenzoic acid (HBA), vanillic acid (VA), 6-hydroxy-2-naphthoic acid (HNA), 4-hydroxycinnamic acid (HCA) or 4′-hydroxybiphenyl-4-carboxylic acid (HBCA). Only the binary copolyester derived from 4-hydroxybenzoic acid proved to be enantiotropic nematic, whereas all other binary copolyesters were more or less crystalline and infusible. Furthermore eight ternary copolyesters were prepared, which all proved to be soluble and thermotropic. 13C NMR spectroscopy proved a random nature of the sequences of the copolyesters, which were only obtained when transesterification catalysts such as Ti(OiPr)4 or MgO were used for the polycondensations. Optical microscopy revealed that five of the eight copolyesters form a homogeneous nematic phase above 220 or 250°C. However, in three cases the nematic melt contained crystalline particles which did not melt below 400°C. According to the WAXS powder patterns and DSC measurements most binary and ternary copolyesters are semicrystalline and form an imperfect orthorhombic crystal lattice. In three cases, the solid phase is best described as a hexagonal columnar mesophase.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021981134
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...