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Smectic ordering of homogeneous semiflexible polymers
Raul Cruz Hidalgo1, D E Sullivan, Jeff Z Y Chen
1Department of Physics, University of Guelph, Guelph, Ontario, Canada N1G2W1. raul@physics.uoguelph.ca
Summary
This study presents a new theory for wormlike polymers, revealing smectic-A phases and phase transitions. The findings detail how polymer rigidity influences nematic, smectic, and isotropic phases.
Area of Science:
- Polymer Physics
- Soft Matter Physics
- Theoretical Chemistry
Background:
- Understanding polymer phase behavior is crucial for materials science.
- Wormlike polymers exhibit complex structures due to their shape and excluded-volume interactions.
- Existing theories often simplify polymer interactions, limiting predictive power.
Purpose of the Study:
- To develop a self-consistent-field theory for homogeneous wormlike polymers with one-dimensional spatial variation.
- To investigate the influence of excluded-volume effects on polymer phase behavior.
- To explore the occurrence and characteristics of smectic-A, nematic, and isotropic phases.
Main Methods:
- Developed a self-consistent-field theory incorporating an effective interaction term for excluded-volume effects.
- Extended the theory to include wormlike cylindrical segments and terminal segments.
- Employed the second-virial (Onsager) approximation to calculate phase diagrams.
Main Results:
- Successfully predicted the formation of a smectic-A phase for homogeneous semiflexible polymers.
- Calculated phase diagrams for varying polymer rigidities (persistence lengths).
- Observed second-order nematic-smectic transitions for infinitely rigid molecules and first-order transitions for semiflexible molecules.
Conclusions:
- The theoretical framework accurately describes polymer phase transitions, including isotropic, nematic, and smectic-A phases.
- Polymer rigidity significantly impacts the nature and occurrence of phase transitions.
- The second-virial approximation shows limitations at high volume fractions, suggesting the need for more advanced theoretical treatments or simulations.