(63a) The thermodynamics for tuning chirality in block copolymers and small oligomers

Uncovering the role that chirality plays and/or the lack thereof in biomolecules, oligomers, and polymers has exciting implications in tuning materials with hierarchical self-assembly. Recent advances in polymer synthesis and the sequence control of monomers can lead to better control of novel phenomena such as chirality transfer, sergeant-soldier effect, and majority-rules effect. Since these cooperative behaviors involve numerous length scales, the use of bottom-up and systematic coarse-graining can still be computationally prohibitive. In this work, we utilize bead-spring models for the polymers alongside a variety of torsional potentials to achieve thermodynamic and kinetic behaviors that can capture some of the novel phenomena reported in experimental work. The first set of torsional potentials comprise single-welled cosines, which works well to model coil-helix block copolymers. We show that the thermodynamics of coil-helix block copolymers is a complex interplay of chain stiffness, pitch, and anisotropy. Depending on the specific parameters, the effect of chirality on the effective Flory-Huggins parameter can be either positive or negative. In a self-assembled lamellar structure, at low pitch, nematic-like behavior can overpower the effects of chirality, but at higher pitch, the molecules do not exhibit nematic behavior. The second set of torsional potentials comprise double-welled potentials. For certain parameters, the neighboring residues can take left-handed and right-handed conformations with equal probability. However, for different sets of parameters, steric repulsions from nearby beads causes a chiral induction mechanism where neighboring residues must take conformations corresponding to the same handedness. This model can pave the way for examining how sequence-specific chirality affect the overall conformation, and for more complex phenomena such as the sergeant-soldier and majority-rules effects.