Structural order parameters terminology

According to the value of S relative to the exciton bandwidth B, the relaxed form of the exciton will be delocalized or localized for — B < — S or — S < — B, respectively. Adopting Toyozawa s terminology,53 we can say that for S < gcB the exciton-phonon coupling is weak and for S > g(B it is strong, where gc is a characteristic parameter of the lattice structure of the order of unity (gc = 0.87 for the square lattice53). 

The classification of polymer mesophases have been considered in many reports (P-70). On analyzing the published data there arises much controversy in the identification. In order to avoid confusion in terminology it is necessary to define the basic terms relating to polymer columnar mesophases before further discussion. Columnar polymer systems have both a correlation of the centers of gravity and molecular orientation, but have mesomorphic properties due to the conformational disorder both of the polymer back-bone and side chains. The structural unit of the polymeric columnar mesophase is a macromolecule. In columnar phases macromolecules form regular 2D-periodic arrays. The two-dimensional symmetry of the column packing and the parameters of two-dimensional lattice are strongly dependent on the form and dimensions of the cross-section of a polymer molecule. 

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