Immiscibility-driven folding: A new design strategy to control polymer chain conformation and morphology.

[Display omitted] • Periodically grafted amphiphilic polymers (PGAPs) leads to microphase separated lamellar morphologies with sub-10 nm domain sizes. • Installation of functional elements, such as mesogens, within the backbone or pendant segment leads to layering of the mesogens. • Zigzag folding of PGAPs can be induced by the addition of segment-selective solvent and could be utilized to generate single-chain crosslinked nanoparticles. Controlling chain conformation is a challenge that has drawn the attention of researchers for several decades; achieving control in solution is inspired by the remarkably elegant strategies seen in biological macromolecules, like proteins, RNA, DNA etc. On the other hand, controlling the chain conformation of polymers in the solid state is a more difficult task, but it is one that could have important ramifications, especially to elicit interesting properties that require distances between different function-imparting units to be precisely controlled. Most of the strategies examined for conformational control utilize intra-chain noncovalent interactions , such as H-bonding, π-stacking, charge-transfer, metal-ion coordination, etc. During the past decade, we have explored an alternate approach, wherein suitably designed periodically grafted amphiphilic polymers (PGAP) carrying long alkylene backbone segments and pendant PEG segments, were shown to adopt a folded zigzag conformation so as to collocate the alkylene segments at the center with PEG segments on either side; the crystallization of the central alkylene segments stabilize the folded conformation and leads to lamellar morphologies with fine tunable layer dimensions. This strategy was more recently exploited to precisely locate functional units, such as mesogens, within layered morphologies at well-defined distances in bulk samples. In this short perspective article, we shall discuss the genesis and design of periodically grafted amphiphilic polymers, and illustrate its utility to generate functional polymeric materials, wherein specific units are located at well-orchestrated distances in the bulk polymer; thus, revealing the power of design at the molecular level to impact properties in the bulk. [ABSTRACT FROM AUTHOR]