Poly rigid-chain

Plastomers. The production of resins (polyfvinyl chloride], polystyrene, and poly [styrene-co-acrylonitrile]) with relatively high toughness has been one of the most important aims of industry. This can be achieved by modifying a rigid chain with small amounts of elastomers. The best results have been obtained by the use of block and graft copolymers. 

A major impetus was given to work, both academic and industrial, in the field of lyotropic systems by the development by duPont of commercial fibres having exceptionally high tensile strength and modulus through use of nematic anisotropic solutions of relatively rigid-chain aromatic polyamides. The earliest product to appear, Fibre B, was based upon poly (p-benzamide) (I)10), but was replaced by the fully commercial product, Kevlar, based upon poly (p-phenylene terephthalamide) (II) U). Arenka, from Akzo, also has the latter chemical repeating unit. 

The influence of the rigidity of the backbone on the mesophases of p-nitro-stilbene-containing polymers was the subject of a study by Maughon et al. [64]. The rigid poly(norbornene) backbone was compared with the flexible poly-(butadiene) chain. For this purpose, p-nitrostilbene was linked by an ester group to the norbornene bicycle, IX-n (n=6,8,10,12), and to the cyclobutene, X-n, n=6y 8,10,12, respectively (Fig. 10). Polymers were synthesized with initiator 6 SEC and DSC data of the resulting polymers are summarized in Table 8. 

The conformations of rigid chains will not be much different in the amorphous state near Tm than they are in the crystal lattice. This means that the melting process confers relatively little additional disorder on the system A5m is low and Tm is increased correspondingly. For example, ether units in polyfethylene oxide) (1-42) make this structure more flexible than polyethylene, and Tm of high-molecular-weight versions of the former species is only 66"C. By contrast, poly(/ -xylene) (11-1) is composed of stiff chains and its crystal melting point is 375°C. 

It should be taken into account that in very rigid chains, such as those of poly-(alkyl isocyanate)s and para-aromatic polyamides, apart from rotation about valence bonds another mechanism can contribute to flexibility the deformation of valence angles and bonds during thermal chain motion just as it should occur in ladder structures (p. 100). When several flexibility mechanisms exist, the resulting rigidity of the homopolymer chain can be evaluated if the flexibilities, resulting from different mechanisms, are considered to be additive and the following equations are used ... 

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 ... 

B. Jingsheng, Y. Anji, Z. Shengqing, Z. Shufan and R Chang, Studies on the semi-rigid chain polyamide - poly(l,4-phenylene terephthalamide), J. Appl. Polym. Sci., 26 (1981) 1211-1220. 

Later, the same methodology was applied by Wallow and Novak for the synthesis of water-soluble poly(p-phenylene) derivatives via the poly-Suzuki reaction of 4,4 -biphenylylene bis(boronic acid) with 4,4 -dibromodiphenic acid in aqueous di-methylformamide [26]. These aromatic, rigid-chain polymers exhibit outstanding thermal stability (decomposition above 500 °C) and play an important role in high-performance engineering materials [27] conducting polymers [28] and nonlinear optical materials [29]. 

It can be easily extended to disc-like molecules (de Gennes, 1973) that form a liquid crystal phase because of their anisotropic shape. The Onsager theory has also been extended to treat the poly-disperse polymer system (Parsons, 1979) and semi-rigid chain systems (Lekkerkeker et al, 1984). 

For conductivity we need poly-radical ionic salts that are conjugated conjugation results in straight, rigid chains in which angles only occur at points of defect. 

Structure of which is identical to their corresponding low molecular weight disk-like counterparts. Rigid chain polymers, such as nucleic acids and polypeptides [5b, 66], are also well known to produce lyotropic columnar mesophases with appropriate solvents. The poly(di-n-alkylsilanes) and poly(di-n-alkylsiloxanes). Fig. 12, with only alkyl side groups and deprived of any mesogen [67] are examples of polymers showing thermotropic columnar mesophases which need to be analyzed in more detail. 

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