End-chain flexibility and the nematic-isotropic transition in liquid crystals: A lattice model of hard particles with rigid, rodlike, central cores and semiflexible pendant segments
1974; American Institute of Physics; Volume: 61; Issue: 10 Linguagem: Inglês
10.1063/1.1681689
ISSN1520-9032
AutoresGöran I. Ågren, Daniel E. Martire,
Tópico(s)Plant Reproductive Biology
ResumoA simple cubic lattice model is utilized to develop the statistics of a system of hard particles with a rigid, rodlike, central core to each end of which is attached a semiflexible chain (tail). The core occupies L collinear sites on the lattice, whereas each of the tails occupies λ adjoining sites. An energy u (of order k T) is required for a tail segment to make a bend, i.e., to change direction. The partition function for the system is obtained by utilizing DiMarzio's counting method for the configurational partition function and an exact matrix method to determine the partition function for a tail. With L =5 (1≤λ≤6) and L =10 (1≤λ≤9), first order anisotropic (larger fraction of cores pointing in the preferred direction than in either of the two perpendicular directions) to isotropic phase transitions are found. The results of the model are compared with those for completely rigid rods, revealing that our transitions occur at higher densities and with smaller relative density changes. Our model is found to exhibit the same qualitative behavior, with increasing λ, in the transition temperature and transition entropy as has been observed for the nematic-isotropic transition in various homologous series.
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