Rigid rod-like polymer

Some polypeptides and para-linked synthetic aromatic polymers take up elongated forms, forming rodlike structures (rather than flexible coils). Their solution viscosity displays a strong dependence on the polymer molecular weight according to Eq. (24), where I and R are the length ( M) and the radius, and pi, is the bulk density of the rodlike molecules [64], 

At higher concentrations (number concentration l/I ), the motion of rodlike polymers is highly hindered in the directions perpendicular to the rod axis, and the viscosity increases spectacularly with mass concentration p) and molecular weight [Eq. (25)] [64]. 

Another concept, in its early stages of exploration, for obtaining large values of through the poling process as well as longterm stability, is rigid rod-like aromatic 

IV Behavior and Properties of Side Group Thermotropic Liquid Crystal Polymers 

Three rigid-rod polymers with chromophores in the main chain (51, 52, and 53) 

A number of rigid rod copolymers, 54 and 55, with chromophores in the side chains were synthesized. According to the X-ray diffraction results, these polymers exhibit- 

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The structures of polymers containing benzobisthiazole and benzobisoxazole have been determined. These form rigid rod-like polymers with high specific strength <81MM935>. For some bis-selenadiazolo analogues of tetracyanoquinodimethane x-ray methods established the presence of extensive intermolecular interactions <87CL2285>. 

A molecular theory for the effect of flow on the orientation of ideal monodisperse rigid rod-like polymers has been developed by Doi (1980) and by Hess (1976). In this theory, a Smoluchowski equation is derived for the probability (u) that a rod-like molecule is oriented parallel to a unit vector u ... 

Electronic Materials The Oligomer Approach Substituted Rigid Rod-Like Polymers-Bulldlng Blocks for Photonic Devices Oligo- and Polyaiylenes, Ollgo- and Polyarylene-vinylenes... 

Monomers of the group 4 metallophthalocyanines are prepared with two hydroxy groups coordinated to the metal on the fifth and sixth sites. Condensation polymerisation produces robust, highly crystalline, and rigid rod-like polymers, in which the number of subunits in the polymer (which are connected by x-oxo bridges) typically varies from about 50 to 200. The polymers can be chemically or electrochemically doped. The conductivity... 

B. Immirzi, G. Lauria, M. Mahnconico, and E. Martuscelli, Thermogravimetric studies of rigid rod-like polymers Influence of solid phase structure and crystallinity on the degradation behavior, Makromol. Chem., Rapid Commun., 12, 563 (1991). 

Despite these extremely promising properties, PPPs consist of very rigid rod-like polymers and are therefore insoluble in all organic or mineral solvents, a characteristic that renders the processing of this... 

Of all the chemical processes which were reviewed and described in references [1-3], it should be noted that up to now only the Kovacic and Yamamoto reactions and, to a lesser extent, the thermal dehydrogenation of poly(l,3-cyclohexadiene) have been used to synthesize polyphenylenes for usual or special applications. Only recently, a new impulse has been given to the synthesis of linear functionalized high molecular-weight PPPs with the adaptation of the Suzuki reaction, and this is currently one of the best possible ways of synthesizing soluble, functionalized PPPs for specific applications with, in particular, the realization of rigid rod-like polymers for mechanical applications, as will be shown in Section 2.1.3. 

T is a constant depending upon the type of polymers, solvent and temperature. The slope, a, of the log[/j] vs. log Mn plot depends on the type of polymer a = 0 for spheric particles, a = 0.5-1.0 for flexible linear polymers and a = 1.0-2.0 for rigid rod-like polymers. As indicated in Figure 12-17, a is 0.75 for the solution with r = 1 and 0.64 for the solution with r = 2, meaning that these two solutions contain flexible linear siloxane polymers. On the other hand, a ranges from 0.2 to 0.5 for the other two solutions with r = 5 and 20. This means these two solutions contain spherically grown particles. Actually, however, those conclusions have to be checked by other techniques, in addition to viscosity measurements. 

Addition of flexible side chains to the stiff 7r-conjugated polymer backbone of the host polymer has proven to be an extremely effective procedure for obtaining tractable and fusible materials. This approach is not limited to conducting polymers but has also attracted considerable attention in more conventional rigid-rod-like polymers [96-99] including various polyimides and polyamides and in other novel polymers such as the polysilanes [100]. Not only does this modification enable the utilization of conventional polymer processing methods, it can also, in some cases, create new materials that exhibit enhanced electronic properties in comparison to the linearly unsubstituted parent polymer. These side-chain-substituted conducting polymers also exhibit properties that do not exist in the unsubstituted hosts discussed in... 

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