Polymer mesophase

Polymers mesophase pitch polyacrylonitrile carbons" mesocarbon microbeads, carbon fibers PAN-based carbon fibers ... 

In view of this disagreement, as well as of evidence from polymer mesophases and MD simulations, we also propose an alternative model, based on the concept that the attractive interactions are so short-lived as to be effectively delocalized. As a consequence, bridges separating consecutive bundles are also taken into account in the evaluation of the average stem length of the growing crystal, in addition to the crystalline stems and to the loops... 

Both our bundle model and MMP s may also be useful approaches to represent the first stage of a polymer mesophase formation from an amorphous system, a process which can be considered a specific mode of polymer crys-... 

Frosini, V. Mechanical relaxation in polymer mesophases. Proc. 28th Macromol. Symp. IUPAC, U. Mass., Amherst, MA, p. 806, 1982... 

In the past few years, there have been important developments in the field of polymer mesophases. One of the essential problems is to understand the relationship between the molecular structure and the properties of mesophases and their solids. 

For the synthesis of side chain liquid crystal polyphosphazenes, the most important examples in Figure 2 are the alkoxy- and aryloxy-polymers. Mesophase behavior has been noted with simple side chains, such as trifluoroethoxy and aryloxy side chains (9). This mesophase behavior is not conventional liquid crystal order, but polymers which exist in a conformationally disordered state (10). 

Complex polymers, mesophase polymers, high-strength polymers, high-temperature polymers conductivity in polymers, micro- and nanophase... 

In our own work, carried out under an extensive collaboration with Professor George Gray, F.R.S., and Drs David Lacey and Peter Gemmell of Hull University (UK), we have studied a number of nematic, cholesteric and smectic polymer mesophases with a view to exploiting their electro-optical properties. Some of the typical structures studied are given in Fig. 3. These are only a few of the structures now available and the reader is referred to ref. 14 for a more complete range of polysiloxane systems as well as to the recent reviews" which also cover the acrylate and methacrylate backbone systems. 

The symmetry requirements necessary for ferroelectricity in low-molecular mass compounds, which were discussed in Section 1.1.3, are valid for polymer mesophases too. If a tilted chiral smectic phase is stable after a polymerization process it must be ferroelectric. Following this idea, the first polymer liquid crystalline ferroelectric has been synthesized by Shibayev et al. [160]. Its spontaneous polarization did not differ very much from the precursor monomer [161]. After polyvinylidene fiuoride (PVF2)... 

This book was conceived as a renewed version of the earlier published original book, Electro-Optical and Magneto-Optical Properties of Liquid Crystals (Wiley, Chichester, 1983) written by one of us (L.M. Blinov). That book was first published in Russian (Nauka, Moscow, 1978) and then was modified slightly for the English translation. Since then new information on electrooptical effects in liquid crystals has been published. Novel effects have been discovered in nematics and cholesterics (such as the supertwist effect), and new classes of liquid crystalline materials, such as ferroelectric liquid crystals, appear. Recently, polymer liquid crystals attracted much attention and new electrooptical effects, both in pure polymer mesophases and polymer dispersed liquid crystals, were studied. An important contribution was also made in the understanding of surface properties and related phenomena (surface anchoring and bistability, flexoelectricity, etc.). 

Distortions and disclinations of the director field are particularly important in commercial polymer mesophases because the density of such defects is thought to play a significant role both in the LCP s rheological properties (ease of processing) and in the ultimate mechanical properties of polymeric solids derived from mesophases. 

Four principal theories describing the transformation of the isotropic fluid into a spontaneously organized nematic fluid, the I N transition, have been developed (1) Onsager s density expansion of the free energy of anisometric particles, (2) Rory s estimate of the insertion probability for a rod-like (multisite) solute into a lattice, (3) Maier and Saupe s construction of apotential of mean torque experienced by mesogens (or solutes) in a nematic environment, and (4) de Gennes transposition of Landau theory to the I N transition. We briefly examine each of these in reverse chronological order because each is relevant to more-recent theoretical descriptions of polymer mesophases. 

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