Side chain/group influence

The use of highly fluorinated side-chain groups that are insulated from reaction centers in order to exploit their unique influence upon the solubility properties of the molecule without affecting the chemistry of the functional groups has spawned a new subfield of fluorine chemistry... 

Table 15.6 Influence of acyl side chain group.

Although the side-chain groups R, R, R have only a weak influence on the acid dissociation constants and the reverse situation, namely a change in polarity due to an ionization event in the vicinity of R, R, R, can have a significant influence on retention. The capacity factor equation describing the sorption to a reversed phase of the above simple nonpolar peptide as a function of pH is given by... 

Peptoid helices are detected in structure-supporting solvents even in relatively short oligomers. Because intramolecular C=0- H-N H-bond formation cannot be the driving force for peptoid secondary structure, the steric influence of the bulky and chiral side chain is likely to provide the required constraint. Interactions between side-chain groups, and between side chains and the carbonyls of the main-chain amides, may add stability to the ordered secondary structure. However, for very short oligomers (34) or peptoids based on N-substituted a-amino acids with a small side chain (35), such as Nala (also termed sarcosine, Sar, 9), complex mixtures of conformers associated with either cis or trans tertiary amide groups have been detected. In addition to the classic CD technique, the contribution of other spectroscopies, such as pulsed ESR (36), may be of value for the 3-D structural validation of peptoid molecules. 

Supercritical or high pressure carbon dioxide can induce polymer crystallization and plasticize polymers. The systematic study on the interaction of carbon dioxide with twenty different crystalline and amorphous polymers has been performed and various influencing parameters have been determined. Through the examination, analysis and comparison of the yield strength, ultimate elongation and modulus both before and after treatments in supercritical carbon dioxide at 3000 psi and 70°C, it was found that two main factors, i.e., degree of crystallinity and the presence of a polar side chain group, e g., ester. 

As would be anticipated, the nature of substituent groups has a profound influence on the reactivity and polymerizability of an NCA. The rates of reaction between NCA and base molecules are affected by stereochemical and electronic factors further, in suitable circumstances, interactions between propagating species and side-chain groups may occur. 

Table 7, Influence of spacer in side chain group on op- tical properties of mesogenlc polymers ... 

Polymer 18 was synthesized in order to verify whether the molecular weight is influenced by side chain groups (it is not), but a notable difference in A, (da-da ) and was observed (17 and 18) despite the fact that the FWHM (2,3(X)-2,5(X)cm- ) were relatively constant all along this series. And similarly, the FWHM for the emission band varied only from 5,300 to 5,600 cm" going from 17 to 18. The loose bolt effect does not apply here because the photophysical parameters increase for... 

Tabrizian, M., Bunel, C., Vairon, J. P, Friedrich, C., and Noel, C., Liquid-crystalline polyacrylates containing biphenyl and chiral terminal groups in the side chain. 1. Influence of the spacer length on the liquid-crystal behaviour, Makromol. Chem., 194, 689-704 (1993). 

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