Chromophores side-chain, rigidity

II. Rigidity of side-chain chromophores as estimated from excimer formation, 200... 

The polypeptide chains are inherently rigid and have a propensity to take a well-defined structure, such as a-helix or -sheet. As a consequence, the side-chain chromophores incorporated into an a-helix, for example, will keep well-defined interchromophore distances and orientations. The spatial arrangement can be predicted from conformational calculations. 

To fully utilize these advantages, however, the side-chain chromophores must be rigidly linked to the polypeptide chain through the shortest spacer (a methylene unit) between the aromatic group and the main chain. If the chromophores are linked with long spacers, as in the case of aryl esters of... 

II. RIGIDITY OF SIDE-CHAIN CHROMOPHORES AS ESTIMATED FROM INTRAMOLECULAR EXCIMER FORMATION... 

It is very important to examine the rigidity and flexibility of the chromophoric polypeptides before discussing their photochemical processes. The rigidity of helical main-chain and side-chain chromophores was estimated from excimer formation between a pair of pyrenyl groups that are incorporated into helical poly(7-benzyl L-glutamate) (I-m, m = 0,2) in the form of L-l-pyrenylalanines [45]. 

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-... 

X is hexyl. The authors report that the typical tree-like macromolecular architecture of these molecules gives rise to a unique behavior in the glass transition temperature as well as in nonlinear optical properties. The nonlinear optical response shows a continuous increase in function depending on the chromophore content. In this way, the nonlinear optical properties can be increased in a way that is not possible with other chromophore-functionalized polymer materials.By attaching chromophores as side chains to the rigid non bendable backbone a treelike structure with flexible branches forms. 

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