Competitive Interactions of π–π Junctions and Their Role on Microphase Separation of Chiral Block Copolymers

Abstract

Herein, enantiomeric polylactide-containing chiral block copolymers (BCPs*) with aliphatic and aromatic junctions are designed and synthesized for investigating the impact of junction π–π interactions on the self-assembly of BCPs*. A profound effect on the microphase separation of the BCP* can be found by introducing the π–π interaction of junctions, resulting in reduced structural ordering due to the mixing of constituted blocks by the formation of junction π-stacking. An ordered microphase-separated structure of the BCP* can be obtained by decreasing the number of aromatic rings of the junction or increasing the total molecular weight of the BCP*. Accordingly, competitive interactions of π–π junctions and microphase separation of the BCP* can be manifested by tuning the thermodynamic driving force for self-organization through molecular design. Most interestingly, the self-assembled morphology can be amended by self-assembling the BCP* from solution through the kinetic control of solvent evaporation. Fast solvent evaporation limits the formation of junction stacking while slow solvent evaporation enhances the π–π stacking between junctions, and thus depresses the microphase separation of BCPs*. The self-assembled mechanisms are further evidenced by spectroscopic results and the corresponding induced circular dichroism (ICD) behaviors of the aromatic junctions. This work demonstrates a new approach to thermodynamically and kinetically regulate the self-assembled morphologies of BCP* by introducing the competitive interactions of π–π junctions on self-assembly.

Supramolecular Chirality Transfer toward Chiral Aggregation: Asymmetric Hierarchical Self‐Assembly

“…investigated the competitive interactions of π  π junctions between the chiral PLA and achiral PS blocks, and their roles on microphase‐separation behaviors. [ 38 ] They indicated that the formation of π  π stacking based on π  π junctions would reduce the structural ordering due to the mixing of constituent blocks. However, ordered morphologies were easily obtained in BCs containing alkyl junctions where no π  π stacking could occur, thus indicating the competitive interactions of π  π junctions and the microphase separation of chiral BCs.…”

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

“…[9][10][11][12] Mechanism insights indicate that the formation of chiral surperstructures are kinetically-dependent and affected by the complex interplays among multiple interactions including chirality, hydrophibic interaction, and crystallization; however, the details of which are still inadequately understood. [13][14][15] Physiological processes and biological reactions prefer to carry out in nanoconfinement space where the spatial confinement plays significant roles in the proceeding of sophisticated biochemical reactions. [16][17][18] For example, spatial DNA confinement in vivo promotes the formation of localized defects at mechanically weak sites which are vital for biological regulatory functions.…”

Influence of Salt Doping on the Entropy‐Driven Lower Disorder‐to‐Order Transition Behavior of Poly(ethylene oxide)‐b‐Poly(4‐vinylpyridine)

“…The phase behavior of BCPs can be affected by some specific intermolecular interactions, [ 22 ] such as H‐bonding, [ 23–26 ] π – π stacking, [ 27–30 ] metal/ion–dipole interactions, [ 31–34 ] and electrostatic interactions. [ 35–43 ] Among them, the BCPs possessing long‐range electrostatic forces achieved by the complexation between metal ions and polymer chains have received extensive attention due to the promising prospect in solid‐state electrolytes, and understanding the phase behavior of these charge‐containing BCPs has important implications for structure‐properties design.…”