Helical conformation polymer backbone-controlled helicity

Many isotactic forms of polymers or simple linear chains, such as polytetra-fluoroethylene and poly(vinylidene chloride), have helical conformations. The pitch of the helix is determined by the influence of the nonbonding short-range interactions between adjacent atoms on the polymer backbone. Helical structures are frequently observed and reflect the subtle effects of these interactions. The controlling factor is the enthalpy of the melt process and Table 5.1 summarizes values for some common polymer systems. 

Farmer et al. evaluated the conformations and dynamics of poly(di- -hexylsilane). " - " The lowest energy conformer for a polymer containing eight silicon atoms was a helical arrangement with 30° torsional angles in the silane backbone. The authors also monitored different backbone and side chain torsions during dynamics simulations and concluded that the conformation present in the crystalline solid is controlled by intermolecular effects. 

Methods based on the formation of complexes of CDAs with metal cations seem especially interesting for testing using PPAs, due both to the possibility of controlling the conformational equilibria at the pendants that will transmit further effects to the backbone, and to the potential role that metal ions could play in the establishment of supramolecular networks between the polymer chains (interchain bonding), giving birth to new types of nanostructures (i.e. helical polymer-metal complexes, HPMCs). 

The use of the N -LC as an asymmetric solvent enabled us to synthesize polymers having a hierarchical structure with a helical conformation of the molecular backbone primary structure. We can expect that this approach can be used to freely control the helical stracture of various products to further progress in the field of polymer synthesis. 

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