Hierarchical Self-Assembly of Halogen-Bonded Block Copolymer Complexes into Upright Cylindrical Domains

Abstract

SummarySelf-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabrication.

Halogen‐Bond‐Mediated Self‐Assembly of Polymer–Resorcinarene Complexes

“…Raman spectroscopy was employed to monitor the vibrational changes upon XB interaction. As in many previous studies, XB‐sensitive CI stretching frequency is interrogated, and upon complex formation, the band at approximately 202 cm −1 is expected to shift to lower energies. As seen in Figure a, already at 1:1 acceptor:donor ratio for the P1‐R1 complex, a redshift from the original peak (203.0 ± 0.3 cm −1 ) to lower energies was clear.…”

“…Here, we demonstrate that the XB acceptor can be replaced with a macrocyclic compound having an anionic XB acceptor site. Unlike in the many previous polymeric XB system, we have used an anionic XB acceptor as they are generally considered to have enhanced halogen bonding in comparison to the neutral XB acceptor species. Overall, macrocycles are interesting compounds for supramolecular chemistry as besides having a large structural variation, they are capable of molecular recognition and complex formation .…”

“…As seen in Figure c, multiple transitions at 700–1600 cm −1 region can be observed. Peaks at 1000–1250 cm −1 region are related to the CF stretching vibrations, and peak shifts and intensity increases around this area are generally considered as an indication of halogen bonding . When spectra of the pure P1 is compared to the spectra of P1‐R1 mixture (1:1 binding group ratio), one can observe such changes at P1 peaks 1035 and 1265 cm −1 , which both shift to lower wavelengths and higher intensities.…”

Efficient Encapsulation of Fluorinated Drugs in the Confined Space of Water‐Dispersible Fluorous Supraparticles

“…[14] On the other hand, fluorination reduces water solubility,and the greater the number of fluorine atoms in amolecule,the higher the tendency of fluorinated residues to avoid unfavorable interactions with other elementsap henomenon known as the fluorophobic effect. [18,19] However,tothe best of our knowledge,i th as seldom been exploited to obtain fluorous SPs. [18,19] However,tothe best of our knowledge,i th as seldom been exploited to obtain fluorous SPs.…”

“…[15] The fluorophobic effect has recently been exploited to drive hostguest recognition in water, [16] self-assembly of ionic liquid crystals, [17] as well as for aligning polymer self-assemblies up to the millimeter length scale. [18,19] However,tothe best of our knowledge,i th as seldom been exploited to obtain fluorous SPs. [20,21] In this context, we reasoned that decorating the inner pockets of such NP assemblies with perfluorocarbon chains (that is,f luorous SPs) should increase affinity toward fluorinated drugs because of the fluorophobic effect, thus providing efficient nanocontainers for drug delivery.…”