Effect of the Polymer Backbone on the Thermotropic Behavior of Side-Chain Liquid Crystalline Polymers (original) (raw)
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Thermotropic liquid-crystalline polymers: A new type of mesomorphic macromolecular system
1980
A new approach to the synthesis of thermotropic liquid-crystalline (LC) polymers is described based on the polymerization of monomers containing various mesogenic groups attached to the backbone chain by flexible polymethylene spacer groups. Dozens of new LC polymers are described, including derivatives of polymethacryloyl L-lysine, cholesteric esters of long-chain aminocarboxylic acids, and other aromatic polymers. Phase transition temperatures, heats of fusion, and x-ray structural analysis were evaluated. Polymers exhibiting spontaneous optical anisotropy in the glasslike, elastic, and fluid states are described, and schemes of molecular packing in the LC phase are proposed. We show the possibility of realizing smectic, nematic, and cholesteric types of structures in these thermotropic LC polymers. A n LC structure for various comblike copolymers not having mesogenic groups at every monomeric unit was detected. The role of specific interactions in side groups and their mobility in allowing for the LC structure are discussed, and the necessity of having particular conformations of the macromolecules is shown to provide the LC structure in films made from various solutions.
Die Makromolekulare Chemie
The syntheses of a number of new comb-like polymers are described, which contain mesogenic groups as side branches presenting models of low-molecular liquid crystals of smectic type. The resulting polymers are capable to form an enantiotropic liquid crystalline phase, which may be defined as smectic, according to the terminology used for low-molecular liquid crystalline substances. The thermodynamic limits of the liquid crystalline state in these polymers were determined, which made it possible to define the liquid crystalline state as a thermodynamically stable phase with spontaneously appearing anisotropy of properties (in particular, the optical anisotropy). The characteristic feature of the structure of these polymers was found to be the layer order of side groups providingin combination with the packing of the mesogenic groupsthe possibility of liquid crystalline properties. Only the mesogenic groups take part in the formation of the crystalline packing in these polymers, whereas the methylene chains are in the amorphous phase together with the backbone chain. *) Part 2: V. P. Shibaev, R. V. Tal'rose, F. I. Karakhanova, N. A. Plate, J. Polym. Sci., Polym. Chem. Ed. 17, 1671 (1979).
Polymer, 2010
We have performed a dielectric spectroscopy study of four homologous cyanobiphenyl polyacrylates with long side chains. The aand d-relaxation times were found to be sensitive to the sequential transformations between mesophases. The s d in the isotropic phase exhibits the characteristics that obeys VFT relation and depend strongly on spacer length. The relaxation times, s d , for the crossover from short range intermolecular interactions to long range LC ordering, decreases with increasing side chain length, implying that the cooperative motions of mesogenic dipoles arrange long range order at shorter time scales, as the spacer length is increased. In the SmA mesophases of CBPAn compounds with n ¼ 8, 9
Molecular engineering of side-chain liquid crystalline polymers by living polymerizations
Progress in Polymer Science, 1997
Living" anionic, cationic, metalloporphyrin and ring-opening metathesis polymer izations have been used to prepare well-defined side-chain liquid crystalline homopolymers, block and graft copolymers and statistical copolymers. This paper analyzes their successes and failures by reviewing the mechanistic aspects and experimental conditions of each type of polymerization, and identifies other classes of mesogenic monomers that could be polymerized in a controlled manner in the future. The emerging structure/property relationships are then identified using well defined SCLCPs in which only one structural feature is varied while all others remain constant.
Die …, 1980
The IR spectra (in the region of 400-3600 cm-') of comb-like polymers in crystalline, liquid-crystalline, and fluid isotropic phases were studied, and the effect of the chemical structure of the long side chains on the crystalline and liquid-crystalline states were examined. The spectroscopic criteria of phase transitions in comb-like polymers were established and the fragments of the side chains involved in the formation of the liquid-crystalline phase, were determined. a) Part 3: V. P. Shibaev, V. M. Moiseenko, N. A. Platt, Makromol. Chem. 181,1381 (1980)
Thermal properties of a series of side-chain liquid crystalline poly(methacrylates)
Journal de Physique, 1988
2014 Le comportement thermique d'une série homologue de poly(méthacrylates) liquides cristallins à groupes mésogènes latéraux a été étudié par thermogravimétrie, analyse thermique différentielle, microscopie optique en lumière polarisée et dilatométrie. L'étude menée par DSC a permis de montrer que l'équilibre n'est atteint que lentement même au-dessus de la température de transition vitreuse. Le polymorphisme thermotrope des polymères a été analysé en fonction de la longueur de l'espaceur souple. Les transitions vitreuses mises en évidence ont été discutées. La dilatométrie a permis de calculer les volumes spécifiques partiels des espaceurs souples et de montrer que, dans l'état mésomorphe vitreux, ces espaceurs sont proches de l'état cristallin ; que, dans l'état isotrope, ils sont à l'etat liquide ; alors que, dans l'état mésomorphe normal, ils sont dans un état « intermédiaire » entre l'état cristallin et l'état liquide. Abstract. 2014 The thermal behaviour of a series of side-chain liquid crystalline poly(methacrylates) has been investigated by thermogravimetry, differential scanning calorimetry, polarizing optical microscopy, and dilatometry. The DSC study has shown that long times are required to reach equilibrium even at temperatures above the glass transition. The thermotropic polymorphism has been determined as a function of the length of the flexible spacer. Glass transitions in the mesomorphic state have been discussed. Dilatometry has shown that, for the « glassy » mesomorphic phases, the partial specific volume of the flexible spacer is close to that corresponding to the crystalline state ; that, for the normal liquid crystalline phases, it is intermediate between those corresponding to the crystal and the isotropic liquid ; and that, for the isotropic polymer, it is close to that of a liquid.
The Frozen State in the Liquid Phase of Side-Chain Liquid-Crystal Polymers
Physical Review Letters, 2006
Quenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that crosslinks or entanglements are not a necessary condition to provide elasticity in melts.
Pure and Applied Chemistry, 2000
A new field of physical chemistry of macromolecular compounds -physical chemistry of synthetic liquid-crys-. talline polymers, particularly, comb-.like polymers with mesogenic side..groups is considered. The classification of mesophase types of such polymers is given and the dependence of its structure on the chemical constitution of monomeric units is analized. The approaches to creation of liquid crystalline polymers with definite interval of existance and of mesophase type are demonstrated. Particular attention is paid to the structure and the optical properties (selective reflection of light) of cholesteric polymers. The formation of an intramo-. lecular liquid crystalline structure in solutions of polymers with mesogenic side groups is discussed.