摘要:

AbstractMolecular information expressed through molecular recognition events provides means for directing the spontaneous formation of supramolecular species from complementary components. It may allow the design and engineering of supramolecular materials, in particular of liquid crystalline and of polymeric nature. Thus, supramolecular mesophases have been obtained from molecular recognition‐induced association of suitable subunits. The self‐assembly of complementary ditopic components generates liquid crystalline “polymers” of supramolecular nature; it takes place by a progressive growth revealed by electron microscopy: from nuclei, to filaments, to tree‐like species, to strings and fibers that present helicity induced by the chirality of the subunits. A rich variety of structures and properties may be expected to result from the blending of supramolecular chemistry with polymer chemistry and material

ISSN:0258-0322    

DOI:10.1002/masy.19930690103

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

ISSN:0258-0322    

DOI:10.1002/masy.19930690104

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe relationship between electronic structure and chemical stability is discussed for three different classes of low band‐gap oligomers and polymers. In oligo‐ and poly[n]acenes as well as in poly‐(arylenemethide)s, the low band‐gap character is connected with a high chemical reactivity due to an energetically favored rearomatization of olefinic or quinonoid substructures, respectively. For double‐stranded oligo‐ and poly(rylene)s, the stability is dramatically increased. Therefore, rylenes appear especially promising in the field of low band‐

ISSN:0258-0322    

DOI:10.1002/masy.19930690105

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

ISSN:0258-0322    

DOI:10.1002/masy.19930690106

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe mesophase to crystal phase transition observed upon heating the monotropic liquid crystal polyurethane (2,6‐LCPU‐6), based on the mesogenic biphenol 4,4′‐bis(6‐hydroxyhexoxy)biphenyl (BHHBP) and 2,6‐toluenediisocyanate (2,6‐TDI), has been investigated by differential scanning calorimetry (DSC), wide angle x‐ray scattering (WAXS) and infrared (IR) spectroscopy. Hexafluoroisopropanol (HFIP) fast solvent‐evaporation casting resulted in 2,6‐LCPU‐6 thin films with a glassy mesophase morphology. The mesophase to crystal exothermic transition has been observed by DSC between 130 and 140°C, depending on sample preparation. It is accompanied by a substantial increase of H‐bonding between urethane C=O and N‐H, as observed by IR. Curve fitting analysis of the conformationally sensitive amide I region revealed three bands; ordered H‐bonded carbonyl groups, disordered H‐bonded carbonyl groups, and “free” carbonyl groups. The prime feature of the 130°C transition is the substantial increase of ordered H‐bonded carbonyl groups at the expense of disordered H‐bonded carbonyl groups. Crystal melting occurs between 180 and 210°C and is accompanied by the complete disappearance of the ordered H‐bonded peak along with substantial changes in the frequency and width at

ISSN:0258-0322    

DOI:10.1002/masy.19930690107

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe syntheses and structures of chiral liquid crystalline polymers (LCPs) are briefly reviewed with emphasis on the established structure‐property correlations. The most recent advances and future trends in their potential applications in optics and electrooptics are also outlined, with particular reference to the ferroelectric, electroclinic, piezoelectric, and nonlinear optical properties of chiral LCP

ISSN:0258-0322    

DOI:10.1002/masy.19930690108

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractRecent advances in the development of liquid‐crystalline polymers for fibres are reviewed. The discussion of lyotropic systems concentrates upon poly(p‐phenylene terephthalamide) and its copolymer with 3,4′‐oxydiphenylene terephalamide units. The discussion of thermotropic systems identifies specific problems restricting the development of fibres and suggests some possible means of impr

ISSN:0258-0322    

DOI:10.1002/masy.19930690109

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA review is presented of research on oriented thermotropic liquid crystalline polymers undertaken at Leeds University. A range of main‐chain polyesters has been studied based on 1,4‐hydroxybenzoic acid and 2,6‐hydroxynaphthoic acid as the primary monomers. By using a combination of dynamic mechanical, dielectric and NMR measurements insight has been gained into the molecular motions associated with the three principal relaxation processes. The behaviour in tension, for stresses parallel and perpendicular to the principal orientation direction, has been related to that in shear by use of mechanical m

ISSN:0258-0322    

DOI:10.1002/masy.19930690110

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe principles of ferroelectricity, especially in liquid crystals (FLC) and polymers, are briefly presented. In a liquid‐crystalline side chain polyacrylate electro‐optical switching with response times of 200–400 μs was measured. Besides the ferroelectric switching an even shorter electroclinic switching process was detected.The influence of the spacer length and the molecular weight on the ferroelectric properties is discussed. The kind and number of chiral centers and their location in the side group strongly affects the electrooptical properties. In one polymer a change of the optical contrast caused by a sign reversal of the spontaneous polarization was found. In another FLC polymer three switching states (antiferroelectric behaviour) were detected. With coloured and fluorescent FLC polymers, obtained by mixing or by copolymerization new promising applications in electrooptical devices are ex

ISSN:0258-0322    

DOI:10.1002/masy.19930690111

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractIn blends of immiscible polymers, amphiphilic species are needed for both morphological stabilization and improvement of the mechanical properties throughout successive processing steps. In order to obtain the required concentration of amphiphilic copolymer at the interface, it seemed of interest to test the possibility of creating these species by in situ reactivity at the interface, for instance by condensation reactions occurring between functionalized polymers. There is another possibility based on the fact that most of the polymers are hydrocarbon compounds, so they are subjected to free‐radical reactivity by hydrogen abstraction on the different hydrocarbon sites. The created free‐radical polymeric species may react together leading to the well known reactions of crosslinking, grafting and/or chain degradation. Therefore, this work deals with reciprocal free‐radical reactivity of two kinds of semi‐crystalline polymers, namely one polyolefin (LDPE, HDPE, PP or EPR) associated with a polyamide (PA‐11 or PA‐6). The reaction has to occur mainly at the interface, where the resulting grafted copolymers have to be anchored for final stabilization of the biphasic system. The level of interfacial grafting and the resulting properties of the reacted blends were characterized carefully, confirming the efficiency of the interpolymer

ISSN:0258-0322    

DOI:10.1002/masy.19930690112

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY