Flexible spacer conformation

Kobayashi, N., Studies on dimer liquid crystals having long flexible spacers conformation, phase structures, and thermodynamic properties [in Japanese], Master s thesis, Tokyo Polytechnic University, 2004. 

Flexible Spacer Conformation in DDA9 Compared to 9DDA9... 

Fig. 4. Schematic representation of template-assembled synthetic proteins. The conforma-tionally restricted template can be orthogonally protected and sequentially linked to helical segments to form a large variety of functionalized TASP proteins. Flexible spacers that connect the folded peptide segments and the template provide the necessary conformational freedom that will allow the hydrophobic residues to find their optimum orientations for packing the core...

The dynamic RIS formalism is used to calculate the rate of first passage from non-excimer-forming conformations to excimer-formlng conformations in seven aromatic polyesters with different flexible spacers between the aromatic rings. The equilibrium chain statistics provides a good description of the relative excimer population for these polyesters, even at times where the dynamic contribution is significant. 

The magnetic susceptibilities of dimer liquid crystals such as NC-Ph—Ph—O—(CH2>n—Ph—Ph—CN(n 9, 10) are measured by a SQUID magnetometer. The results obtained are interpreted within the framework of the RIS approximation, the effect arising from the conformational anisotropy of the flexible spacer being strictly taken into account. The order parameters of the mesogenic core axis thus estimated are found to be consistent with those directly observed at just below 7N) by the ZH NMR technique using mesogen-deuterated samples. 

The fluorescence In dilute solution is measured for five polyesters with terephthalate as the rigid aromatic unit and diols derived from cyclohexane as the flexible spacer, A conformational analysis concludes that the spacers most conducive to excimer formation are the 1,3-c/s-cyclohexanediol and 1,4-e/s-eyclohexanedimethanol. This result from calculations is compatible with experimental results. 

Schematically the arrangement of a macromolecule with side-chain mesogenic groups in the liquid crystalline state is shown in Fig. 13. Flexible spacers give the mesogenic group its mobility. It is of interest to note that in such liquid crystals all positional mobility of the mesogen is based on conformational motion of the flexible spacer and backbone. Restricting this mobility either prohibits ordering, or freezes the order into the glassy state.

The linkage of conventional low molar mass Lc s to a linear polymer main chain via a flexible spacer provides a method to realize systematically the liquid crystalline state in linear polymers. Above the glass transition temperature Tg the polymer main chain can be assumed to exhibit, at least in the nematic state, an almost free motion of the chain segments, causing a tendency towards a statistical chain conformation. Due to their mobility, the polymer main chains are able to diffuse past each other, which is a condition to obtain the liquid state. Therefore such polymers can be classified as liquids of high viscosity10O). 

Bis(crown ethers) connected by a flexible spacer are a source of intramolecular sandwich-type complexes with alkali metal ions <1992MI1>. A conformational analysis (based on a combination of semiempirical and ab initio methods) performed on 12-crown-3 38 and 12-crown-4 39 predicted that, in the case of sandwich-type complexation, the nucleophilic cavity of 12-crown-3 rather than that of 12-crown-4 is more prone to complexation with the Na+ ion. Accordingly, ion-selective electrodes based on bis(12-crown-3) derivatives with dialkylmalonate spacers displayed the highest selectivity for Na+ ions among the alkali and alkaline earths investigated, and superior to the Na+ selectivity reached with the bis( 12-crown-4) analogue <2003ANA(480)291>. 

We say that the polymer chain of this type forms a small globule if in the equilibrium conformation, due to the attraction of rods, the average spatial distance between the ends of the flexible spacer is much less than a. 

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