Nematic polymers

We present a primitive model that describes a cooperative helix‐coil liquid–crystal phase transition. Consider a solution of macromolecules that individually undergo a helix‐coil “transition” as a function of some external parameter such as temperature or pH. At some given value of the parameter, the chain is composed of a statistical distribution of rigid (helical) segments and flexible coiled segments. We then suppose that there exists an intermolecular Maier‐Saupe type of quadrupole‐quadrupole interaction between the rigid sections that derives from excluded volume and van der Waals forces. In terms of a mean‐field approximation, we investigate the possible phase transitions as a function of polymer concentration. In particular, we show that the intermolecular coupling may lead to a first‐order transition in which the macromolecules make a transition from a nearly coiled to a nearly rigid conformation accompanied by the simultaneous development of a long‐range nematic type of liquid‐crystalline orientational order.