Recent Developments in Polymeric Assemblies and Functional Materials by Halogen Bonding

Abstract

Polymers have long been known to us for their versatile utility in our daily lives. With many years of successful advancement in controlled polymer synthesis and supramolecular chemistry, currently an amalgamation of these two fields is becoming increasingly important for generating modern‐day emerging polymeric materials. Hydrogen bonding and other noncovalent interactions like π‐stacking, host‐guest interaction, electrostatic interaction, metal‐ligand coordination have been explored much to this context, unlike the recently emerged halogen bonding, which indeed shows advantageous features like superior hydrophobicity, directionality and polar solvent resistance compared to ubiquitous hydrogen bonding. Hence, rendering these properties of halogen bonding into polymeric domain for generating functional materials for application in advance nanotechnologies is highly desirable. In the recent years, substantial progress has been made in fulfilling this challenging goal. This is evident from the escalating number of scientific publications in this research area every year. In this minireview, we have summarized the most recent developments in the field of halogen bonded polymeric assemblies and supramolecular polymers and discussed them in the context of their emerging materials properties and functions. Emphasis is given on highlighting various design criteria adopted in crystal engineering, covalent and supramolecular polymers in the past five years for constructing diverse organic functional materials, viz. liquid crystals, photoresponsive and photochromic materials, biomaterials and gels, self‐healing materials and many others by virtue of this highly directional supramolecular tool. In conclusion, a brief perspective on the advantages, challenges and future prospects in this rapidly growing field of research is discussed.

Halogen Bonding Mediated Hierarchical Supramolecular Chirality

“…The intercalation of IFB interfered with the stacked cyanostilbene moieties to allow for an alternative supramolecular assembly modality. Halogen bonding complexation was also evidenced by 19 F NMR spectra (Figure 2j). With increasing molar ratio of CS 3 or CS 4 , shifts to higher fields were observed for CS 3 or CS 4 , respectively.…”

“…In this regard, Jiang reported the C–I···π and C–I···S supported folded oligopeptides. , Our group clarified the influence of halogenation and the halogen bond effect on the chiral assembly of N-terminal aromatic amino acids . In spite of a few reports, halogen bonding-directed chiral hierarchical coassemblies have yet been developed. − Incorporation of multicomponents by halogen bonds into coassemblies would facilitate the fabrication of functional chiral materials with tunable chiroptical activity and other features, which remain major challenges and rooms so far. − …”

The Distance between Minima of Electron Density and Electrostatic Potential as a Measure of Halogen Bond Strength

“…Among various types of σ -hole interactions, halogen bonds (XBs) are among the most known and widely investigated [ 1 , 2 , 3 , 4 ]. XBs were shown to play a significant role in organocatalysis [ 5 , 6 , 7 , 8 ], crystal engineering and supramolecular chemistry [ 9 , 10 , 11 , 12 , 13 ], materials science [ 14 , 15 , 16 , 17 ], stabilization of explosives [ 18 ], drug design [ 19 , 20 ], etc. XBs R–X⋯A (X—halogen) are formed between an electron-depleted region on the continuation of the R–X bond and an electron-rich region of another atom or molecule A ( Figure 1 , bottom).…”

Halogen bonding regulated functional nanomaterials

“…The development of halogen bonding containing polymers was introduced by Schubert's group. 48 Besides, Resnati's group 49 and Das' group 50 highlighted the design criteria in constructing various halogen-bonded functionalities by virtue of the unique features of halogen bonding.…”