Orthogonal Polymer Recognition Based on Semiartificial Helical Polysaccharide

Abstract

Two kinds of polymeric nanoarchitectures, i.e., one-dimensional polymer composites and two-dimensional sheet-like structures, can be created using a semiartificial helical polysaccharide with one-dimensional cavities and peripheral molecular-recognition sites.The creation of precise polymer assemblies at the nanometer scale, which could lead to novel chemical and physical properties, depending on their assembly modes, is of great concern because of their potential applications as fundamental nanomaterials. In particular, much effort has been expended on controlling the alignment of ³-conjugated polymers, expecting the creation of nanowires, circuits, and conductive films. Manipulation of functional polymer chains in a bottom-up manner, however, is still a challenging research subject because of the lack of established strategies. 1Natural polysaccharides have captured intense attention as an abundant material source, applicable for recyclable plastics as well as for biomaterials. We have, so far, demonstrated that helical polysaccharides, ¢-1,3-glucans, have a unique wrapping ability toward hydrophobic polymers to form one-dimensional nanocomposites, where the ¢-1,3-glucans act as manipulators for various guest polymers.2 To further extend this unique wrapping ability of ¢-1,3-glucans, we herein report a novel semiartificial ¢-1,3-glucan (Chl-CUR) that has external molecular-recognition sites based on chlorophyll molecules in addition to the inherent one-dimensional spaces inside the helix (Figure 1). Amphiphilic chlorophyll molecules with dendritic tetra(ethylene glycol) (TEG) units are introduced into the 6-OH groups of curdlan, a type of ¢-1,3-glucan, through selective azidation of the 6-OH groups followed by Cu(I)-catalyzed coupling between the azide groups and terminal alkyne attached to the 3¤-position of chlorophyll. It is expected that the attached chlorophyll molecules would be arranged on the curdlan surface in a regular fashion, thereby providing unique ³ spaces for precise polymer recognition.It is already known that natural ¢-1,3-glucans adopt a triplehelical structure in water but dissociates into single chains in DMSO. To investigate whether Chl-CUR also undergoes similar interpolymer transformations as a result of changing water/ DMSO compositions, distilled water was gradually added to a DMSO solution containing Chl-CUR (0.046 mg mL ¹1). Chl-CUR shows characteristic sharp peaks in DMSO at 429 and 654 nm assignable to the Soret and Q y bands of the chlorophyll moiety, suggesting that Chl-CUR dissociates into single chains in DMSO. Upon addition of water, a significant hypochromic effect and slight red shifts, as shown in Figure 2a, were observed in the UVvis spectra, which is indicative of aggregation of chlorophyll units through strong ³³ stacking interactions. On the basis of our previous papers, the CD intensity of Chl-CUR is expected to increase when it adopts a triple-helical structure in water.3 However, as revealed in Figure 2b, the CD intensity gradually decreased with increasing water co...

Nickel-Catalyzed Coordination Polymerization-Induced Self-Assembly of Helical Poly(aryl isocyanide)s

“…This chirality gives the helix an obvious role in recognition, which is well demonstrated by the α-helices present in the Zinc finger motif for its binding to DNA double helix or proteins. [2][3][4] Taking the polyvalence of the helical structure as inspiration, chemists have applied synthetic helices to different areas [5][6][7] such as nanomaterials, [8][9][10] chiral recognition, [11][12][13][14] and catalysis. [15][16][17][18][19] In the field of nanomaterials, using nature's building blocks, Lecommandoux and coworkers investigated the synthesis and self-assembly of polypeptide-based diblock copolymers into different nanostructures and studied their possible application as stimuli-responsive materials.…”

“…Taking the polyvalence of the helical structure as inspiration, chemists have applied synthetic helices to different areas − such as nanomaterials, − chiral recognition, − and catalysis. − In the field of nanomaterials, using nature’s building blocks, Lecommandoux and co-workers investigated the synthesis and self-assembly of polypeptide-based diblock copolymers into different nanostructures and studied their possible application as stimuli-responsive materials. − To replicate the properties of cell-penetrating peptides (CPPs), which have excellent membrane permeability in part as a consequence of their helical shape, Wu and co-workers reported that rapid cellular internalization was observed for PEGylated left-handed helical poly­(phenyl isocyanide) corona micelles. , However, such assemblies are usually prepared by methods that are time- and resource-consuming and give solutions with a relatively low content of polymer.…”