Poly(ε‐caprolactone) Single Crystals with Different Aspect Ratios Mediated by Counterion Exchange on the Basis of Hofmeister Series

Abstract

Although polymeric single crystals fabricated from self‐assembly of block copolymers are reported, preparation of single crystals with different aspect ratios still remains a major challenge. In this work, a facile way is demonstrated to prepare poly(ε‐caprolactone) based single crystals with tunable aspect ratios through simple counterion exchange on the basis of the Hofmeister series. Briefly, after ion exchange from Brˉ (an ion‐containing triblock copolymer, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)‐b‐poly(quaternized 2‐(dimethylamino)ethyl methacrylate)/ethyl bromide (PEO‐b‐PCL‐b‐qPDM‐Br)) to more hydrophobic anions, Iˉ, SCNˉ, PF6ˉ and OTfˉ, respectively, morphological transitions from spheres to wormlike micelles and sphere to 2D platelet structure with an increasing aspect ratio are observed. The morphological transition depends on the essential hydrophilicity of the qPDM‐X segment and increasing crystallinity of the PCL core caused by ion exchange. These findings provide a facile approach to the preparation of polymeric single crystals with tunable aspect ratios.

Single crystals and two‐dimensional crystalline assemblies of block copolymers

“…51 Through counterion exchange, various counterions with different hydrophilicity, such as Br À , I À , SCN À , PF 6 À and OTf À , were introduced into the amorphous block, thus the aspect ratio of BCPSCs could be easily controlled. 51 They also prepared lozenge BCPSCs of PCL-b-qPDM containing liquid crystal (LC) AOT anions in the corona. 52,53 The soluble qPDM chains prefer to arrange parallel due to the directional arrangement of the LC AOT.…”

“…25,[44][45][46][47][48][49][50] Tong et al prepared BCPSCs of PEO-b-PCL-b-qPDM. 51 Through counterion exchange, various counterions with different hydrophilicity, such as Br À , I À , SCN À , PF 6 À and OTf À , were introduced into the amorphous block, thus the aspect ratio of BCPSCs could be easily controlled. 51 They also prepared lozenge BCPSCs of PCL-b-qPDM containing liquid crystal (LC) AOT anions in the corona.…”

Tailoring Self-Assembly of Alternating Copolymers for Ordered and Crystalline 2D Nanostructures via Diverse Strategies

“…In recent years, breakthroughs have been achieved by introducing uniform assembly units, specific crystallizable blocks, or directional noncovalent interactions. − For instance, the self-assembly of quasi-monodisperse polymers or nanoparticles has been utilized to generate 2D nanosheets with ordered structures . Crystallization-driven self-assembly (CDSA) has facilitated arrangements in crystallizable segments, − resulting in uniform 2D structures. − Among directional noncovalent interactions, π–π stacking has proven effective for constructing 2D structures. − In addition to traditional block copolymers, emerging alternating copolymers show promising potential for constructing materials with an ultrasmall or thin dimension, leveraging their consistently small and uniformly distributed repeating subunits. − These advancements have promoted the development of ordered 2D nanomaterials with improved properties and functionalities.…”