Rigid chain polymers properties

Schaefgen JP, Bair TI, Ballou JW, Kwolek SL, Morgan PW, Panar M, Zimmermann J (1979) In Cifferti A, Ward IM (eds) Rigid chain polymers, properties of solution and fibers. Banking, England, p. 173... 

Schaefgen, J.R., Bair, T.I., Ballou, J.W., Kwolek, S.L., Morgan, P.W., Panar, M. and Zimmerman, J. (1979) Rigid chain polymers properties of solutions and fibres. In Ultra-High-Modulus Polymers, Chapter 6, A. Ciferri and I.M. Ward (Eds.). Applied Science Publishers, London. 

Two approaches to the attainment of the oriented states of polymer solutions and melts can be distinguished. The first one consists in the orientational crystallization of flexible-chain polymers based on the fixation by subsequent crystallization of the chains obtained as a result of melt extension. This procedure ensures the formation of a highly oriented supramolecular structure in the crystallized material. The second approach is based on the use of solutions of rigid-chain polymers in which the transition to the liquid crystalline state occurs, due to a high anisometry of the macromolecules. This state is characterized by high one-dimensional chain orientation and, as a result, by the anisotropy of the main physical properties of the material. Only slight extensions are required to obtain highly oriented films and fibers from such solutions. 

These two different approaches for attaining an oriented state in flexible-chain and rigid-chain polymers indicate that the fundamental property of macromolecules - their flexibility - is of great importance to the orientation processes. However, the mechanism of the transition into the oriented state and the properties of highly oriented systems exhibit many features characteristic of both rigid- and flexible-chain polymers. 

G. C. Berry and C. E. Sroog, Rigid Chain Polymers Synthesis and Properties, Wiley, New York (1979). 

Polymer science is underdeveloped in terms of descriptions of the structure and properties of stiff-chain polymers. The conducting polymers fall mostly within this blind spot. They also present a number of novel possibilities such as the conversion from a flexible-chain precursor to a rigid-chain polymer, and the conversion between doped and undoped states in the soluble polythiophenes. Likewise, solid-state physics has yet really to tackle the transport of electrons in, and between, disordered, twisted chains. For each of the disciplines involved, the explosion of interest in conducting polymers has brouht a host of new question and new ideas. The process is far from over. 

In order to give a general idea about the appearance of liquid crystalline state and about the properties of the systems containing these polymers, some examples of linear rigid-chain polymers follow ... 

In recent years much attention in the field of polymer science and technology has been devoted to rigid-chain polymers. This is due to the fact that many currently used polymer materials with very valuable thermomechanical properties are based on macromolecular compounds characterized by limited chain flexibility usually, these compounds are called rigid-chain polymers. 

We will also deal with sohm features of the behaviour of rigid-chain polymer molecules in dilute solutions with emphasis on their dinamooptical and electroop-tical properties. 

Hydrodynamic Properties of Rigid-Chain Polymer Molecules... 

A high segment length value A of rigid chain polymers leads to many characteristic hydrodynamic properties of their solutions differing from those of flexible polymers. 

For most rigid-chain polymers the ratio A/d is much h er than that for flexible chain pol3miiers. Hence, the molecular coil of a rigidchain length L (or M) in solution is large, is much more loose than a flexible-chain pol3tmer (F 3). As a result, these polymers exhibit two important properties. 

Equations (4) and (5) show that when the parameter x = 2 L/A changes from 0 to the hydrodynamic properties of a worm-like chain change from those of a thin straight tod to those of an undrained Gaussian coil. In accordance with this the dependence of intrinsic viscosity (nl and diffusion coefficient D on molecular weight M of a rigid-chain polymer cannot be described by the usual Mark-Kuhn dependence... 

Studying molecular properties of rigid-chain polymers by hydrodynamic methods, specific difficulties sometimes arise. Thus, many polymers with aromatic chains that are of great practical importance are molecularly soluble only in very aggressive media such as concentrated sulfuric acid. Hence, experiments in these systems require specific instruments ... 

Tables 1—3 give the values of molecular parameters characterizing the equilibrium rigidity and hydrodynamic properties of molecules of some rigid-chain polymers obtained from viscometric and diffusion-sedimentation measurements of their dilute solutions.

The situation is more favourable for the study of EB in solutions of flexible-chain polyelectrolytes for which the value of K may be higher by several orders of msg-nitude than for molecules bearing no charge This seems plausible since the uncoiling of a flexible-chain polyion by electrostatic repulsion of ionc enic groups increases the persistent length of the chain and the optical and hydrodynamic properties of the molecule approach those of a rigid-chain polymer ... 

As already indicated, (p. 170) the dispersion of the Kerr effect in the range of radio frequencies is a characteristic property of rigid-chain polymer solutions. This can be seen in Figs. 59-61 which show frequency dependences of EB for solutions of polj chlorohexyl isocyanate)s, cellulose earbanilate and ladder polychlorophenylsiloxane. Similar dependences have been obtained for poly(butyl isocyanate) various cellulose ethers and esters and ladder polysiloxanes ... 

Equation (85) represents a general relationship between the Kerr constant K and the dipolar and optical properties of a kinetically rigid particle. To establish the quantitative dependence of K on the conformation and structure of a rigid-chain polymer molecule, the molecular model describing its electro-optical properties should be specified. For this purpose, we use a kinetically rigid worm-like chain, just as for the study of the FB problem. 

The values of S obtained in this manner (Table 14) and those obtained by other methods (Tables 1 and 9) are close to each other within experimental error whereas the values of mo (Table 14) and the values that could be expected taking into account the structure of the main chain of tl se polymers are in reasonable agreement This means that equilibrium dielectric properties of rigid-chain polymer solutions can be adequately described in terms of the model of a worm-like chain according to Eqs. (86) and (87). 

The material considered in this review show that the molecules of r id-chain polymers exhibit a number of characteristic (sometimes even unique) propertfes many of which cannot be observed in flexible-chain polymers. The FB and EB of rigid-chain polymer solutions can serve as effective methods of studying these properties. 

Papkov, S. P The evaluation of Kuhn segment value of rigid-chain polymers according to the viscosimetric properties of (hinted solutions. High-Molecular Compoimds. B, 1982, 24(11), 869-873. 

Tsvetkov, V. N. Rigid-Chain Polymer Molecules. Leningrad, Chemistry, 1986, 328 p. Gel mont, M. M. Braverman, L. R Smirnova, V. N. Kulichikhin, V. G. Efros L. S. The influence of different-linking coimected with asymmetry of one from monomers, on polyamidobenzimidazoles properties. High-Molecular Compounds. A, 1987, 29(3), 537-543. 

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