Physics of low complexity polymers: patterning, polymer collapse and bulk microphases

Polymer physics has arisen as a pillar of understanding behavior of intrinsically disordered proteins. Behavior of polymers can be understood in terms of generic behavior. Specifically, phase behavior can be understood in terms of solvent quality and chain length. The theory is well established for homopolymers, and specific heteropolymer structures, in particular random and co-block polymers. However, protein sequiences are neither of these. Nevertheless, there is a clear link between sequence and properties, which has given rise to the concept of molecular grammar.

In this article, we establish a framework to understand the behavior of Sturmian polymers, which provide a reasonable non-random polymer model for disordered proteins. Specifically, we show that molecular grammar arises as a non-linear critical susceptibility near the θ transition of single chains. We demonstrate that molecular grammar exists in polymer melts, where is determines a length scale under which chains are compressed, and above which chains are expanded.