Structure-property relationship chain rigidity

Rigid and semi-rigid main chain systems, historically the first synthetic PLCs studied, are treated with emphasis on structural, morphological, and mechanical properties. More recent flexible main chain systems are discussed, focusing mainly on structure-property relationships. 

In the synthesis of the thermally stable aromatic polymers, chains with varying degrees of rigidity were obtained, and some interesting structure property relationships evolved, particularly as observed through solution viscosity and glass transition temperatures. ... 

Tatiana A. Shantalii - Senior researcher, Department of Polymer Thermophysics (DePTh), Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine. She graduated in Organic Chemistry from the Kuban State University (Krasnodar) and got her PhD (Polymer Chemistry) in the Institute of Macro-molecular Chemistry, National Academy of Sciences of Ukraine (1994). Area of research synthesis and structure-property relationships for semi-rigid chain polymers reinforced with the sol-gel derived inorganic nanophase. Publications over 30 papers in refereed journals. 

Examination of Table 15.4 shows that rigid groups present in the backbone of the chains are required for the cohesion of the corresponding polymers. The investigation of this structure-property relationship led to the discovery of an important family of polymeric materials by Dickinson and Whinfield (ICI) in 1942. 

The new lubricants exhibited a good CSS friction properties for the rigid disks compared to the PFPE (Z-DOL) as shown in Fig. 7. The relationship between the CSS durability and the molecular structure of the lubricant in terms of the polar group, chain length, and chain symmetry was investigated. 

Figure 16 shows relationships between the number of introduced side chains and relaxation rigidity (G,) at 900 s for carboxymethylated wood binding various metal ions [341. Wood specimens were prepared from Japanese linden Tilia japonica Smik.). Carboxymethylation and the introduction of metal ions was the same procedure as mentioned in the previous section [32,33]. Stress relaxation measurements were carried out in an aqueous solution at 30°C. The relaxational property of carboxymethylated wood without metal ions is first discussed. For carboxymethylated wood (a broken line in Fig. 16), Gf (900) decreases with an increase in the number of introduced side chain. This rapid decrease appears to be caused by two factors. One is the effect of sodium hydroxide (NaOH). Young s modulus of wood treated with an aqueous solution of NaOH decreases remarkably under wet conditions, especially at concentrations above 10% NaOH [35]. The other factor is the electrostatic repulsion of ionized carboxymethyl groups in carboxymethylated wood, as mentioned in the above section [291. For example, conformation of polypeptide is influenced by the ionization of the side chains, and the structural change of the helix-coil transition has been interpreted as a reversible transformation. Theoretical treatment of the transformation has been reported to explain the mechanism [23-25, 36-43]. The conformation of component molecules in wood, however, cannot change markedly by ionization in comparison with soluble polyelectrolytes in water, because carboxymethylated wood is not dissolved in water. Only space among the main chains is expanded by the electrostatic repulsion due to negatively charged side chains. For these reasons, G (900) of carboxymethylated wood decreases with an increase in the number of introduced side chains.

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