A Luminescent Poly(phenylenevinylene)–Amylose Composite with Supramolecular Liquid Crystallinity

Fabrication of Nanostructured Supramolecules through Helical Inclusion of Amylose toward Hydrophobic Polyester Guests, Biomimetically through Vine-Twining Polymerization Process

This review article presents the biomimetic helical inclusion of amylose toward hydrophobic polyesters as guests through a vine-twining polymerization process, which has been performed in the glucan phosphorylase (GP)-catalyzed enzymatic polymerization field to fabricate supramolecules and other nanostructured materials. Amylose, which is a representative abundant glucose polymer (polysaccharide) with left-handed helical conformation, is well known to include a number of hydrophobic guest molecules with suitable geometry and size in its cavity to construct helical inclusion complexes. Pure amylose is prepared through enzymatic polymerization of α-d-glucose 1-phosphate as a monomer using a maltooligosaccharide as a primer, catalyzed by GP. It is reported that the elongated amylosic chain at the nonreducing end in enzymatic polymerization twines around guest polymers with suitable structures and moderate hydrophobicity, which is dispersed in aqueous polymerization media, to form amylosic nanostructured inclusion complexes. As the image of this system is similar to how vines of a plant grow around a support rod, this polymerization has been named 'vine-twining polymerization'. In particular, the helical inclusion behavior of the enzymatically produced amylose toward hydrophobic polyesters depending on their structures, e.g., chain lengths and substituents, has been systematically investigated in the vine-twining polymerization field. Furthermore, amylosic supramolecular network materials, such as hydrogels, are fabricated through vine-twining polymerization by using copolymers, where hydrophobic polyester guests or maltooligosaccharide primers are covalently modified on hydrophilic main-chain polymers. The vine-twining polymerization using such copolymers in the appropriate systems induces the formation of amylosic nanostructured inclusion complexes among them, which act as cross-linking points, giving rise to supramolecular networks at the nanoscale. The resulting materials form supramolecular hydrogels, films, and microparticles.

Helix-Sense-Selective Encapsulation of Helical Poly(lactic acid)s within a Helical Cavity of Syndiotactic Poly(methyl methacrylate) with Helicity Memory

We report a highly enantio- and helix-sense-selective encapsulation of helical poly(lactic acid)s (PLAs) through a unique "helix-in-helix" superstructure formation within the helical cavity of syndiotactic poly(methyl methacrylate) (st-PMMA) with a one-handed helicity memory, which enables the separation of the enantiomeric helices of the left (M)- and right (P)-handed-PLAs. The M- and P-helical PLAs with different molar masses and a narrow molar mass distribution were prepared by the ring-opening living polymerization of the optically pure l- and d-lactides, respectively, followed by end-capping of the terminal residues of the PLAs with a 4-halobenzoate and then a C₆₀ unit, giving the C₆₀-free and C₆₀-bound M- and P-PLAs. The C₆₀-free and C₆₀-bound M- and P-PLAs formed crystalline inclusion complexes with achiral st-PMMA accompanied by a preferred-handed helix induction in the st-PMMA backbone, thereby producing helix-in-helix superstructures with the same-handedness to each other. The induced helical st-PMMAs were retained after replacement with the achiral C₆₀, indicating the memory of the induced helicity of the st-PMMAs. Both the C₆₀-free and C₆₀-bound helical PLAs were enantio- and helix-sense selectively encapsulated into the helical hollow space of the optically active M- and P-st-PMMAs with the helicity memory prepared using chiral amines. The M- and P-PLAs are preferentially encapsulated within the M- and P-st-PMMA helical cavity with the same-handedness to each other, respectively, independent of the terminal units. The C₆₀-bound PLAs were more efficiently and enantioselectively trapped in the st-PMMA compared to the C₆₀-free PLAs. The enantioselectivities were highly dependent on the molar mass of the C₆₀-bound and C₆₀-free PLAs and significantly increased as the molar mass of the PLAs increased.

Formation of microparticles from amylose-grafted poly(γ-glutamic acid) networks obtained by thermostable phosphorylase-catalyzed enzymatic polymerization

Amylose is a natural polysaccharide with helical conformation, which spontaneously forms water-insoluble assemblies, such as double helixes and inclusion complexes, at ambient temperatures in aqueous media, whereas it is synthesized as a water-soluble single chain by thermostable phosphorylase-catalyzed enzymatic polymerization at elevated temperatures in aqueous buffer solvents. In this study, we investigated the enzymatic polymerization at 80 °C using a primer-grafted poly(γ-glutamic acid) (PGA) in the presence or absence of poly(l-lactic acid) (PLLA) as a guest polymer for inclusion by amylose. Consequently, the produced amylose-grafted PGAs formed microparticles by cooling the mixtures at room temperature after the enzymatic polymerization in either the presence or the absence of PLLA. The particle sizes, which were evaluated by SEM measurement, were dependent on the feed ratios of PLLA. Based on the characterization results by the powder X-ray diffraction, IR, and dynamic light scattering measurements, a mechanism for the formation of the microparticles in the present system is proposed.

Formation of Supramolecular Soft Materials from Amylosic Inclusion Complexes with Designed Guest Polymers Obtained by Vine-Twining Polymerization

Amylose forms supramolecular inclusion complexes with polymeric guests in the phosphorylase-catalyzed enzymatic polymerization field, so-called "vine-twining polymerization". However, such inclusion complexes have not exhibited specific properties and processability as functional supramolecular materials. In this study, we found that amylosic inclusion complexes, which were obtained by vine-twining polymerization using a designed guest polymer, that is, an amphiphilic triblock copolymer poly(2-methyl-2-oxazoline-block-tetrahydrofuran-block-2-methyl-2-oxazoline), exhibited gel and film formation properties. The characterization results of the products suggested that enzymatically elongated amylose chains complexed with the polytetrahydrofuran block in the triblock copolymer. Accordingly, the outer poly(2-methyl-2-oxazoline) blocks constructed hydrophilic spaces among the inclusion complex segments. Furthermore, the presence of such outer blocks affected the lower regularity of crystalline alignment among the inclusion complex segments in the products. Such higher-order structures probably induced the formation of supramolecular soft materials, such as gels and films.

Preparation and Material Application of Amylose-Polymer Inclusion Complexes by Enzymatic Polymerization Approach

This review presents our researches on the preparation and material application of inclusion complexes that comprises an amylose host and polymeric guests through phosphorylase-catalyzed enzymatic polymerization. Amylose is a well-known polysaccharide and forms inclusion complexes with various hydrophobic small molecules. Pure amylose is produced by enzymatic polymerization by using α-d-glucose 1-phosphate as a monomer and maltooligosaccharide as a primer catalyzed by phosphorylase. We determined that a propagating chain of amylose during enzymatic polymerization wraps around hydrophobic polymers present in the reaction system to form inclusion complexes. We termed this polymerization “vine-twining polymerization” because it is similar to the way vines of a plant grow around a rod. Hierarchical structured amylosic materials, such as hydrogels and films, were fabricated by inclusion complexation through vine-twining polymerization by using copolymers covalently grafted with hydrophobic guest polymers. The enzymatically produced amyloses induced complexation with the guest polymers in the intermolecular graft copolymers, which acted as cross-linking points to form supramolecular hydrogels. By including a film-formable main-chain in the graft copolymer, a supramolecular film was obtained through hydrogelation. Supramolecular polymeric materials were successfully fabricated through vine-twining polymerization by using primer-guest conjugates. The products of vine-twining polymerization form polymeric continuums of inclusion complexes, where the enzymatically produced amylose chains elongate from the conjugates included in the guest segments of the other conjugates.

Evaluation of Stability of Amylose Inclusion Complexes Depending on Guest Polymers and Their Application to Supramolecular Polymeric Materials

This paper describes the evaluation of the stability of amylose-polymer inclusion complexes under solution state in dimethyl sulfoxide (DMSO) depending on guest polymers. The three complexes were prepared by the vine-twining polymerization method using polytetrahydrofuran (PTHF), poly(ε-caprolactone) (PCL), and poly(l-lactide) (PLLA) as guest polymers. The stability investigation was conducted at desired temperatures (25, 30, 40, 60 °C) in DMSO solutions of the complexes. Consequently, the amylose-PTHF inclusion complex was dissociated at 25 °C, while the other complexes were stable under the same conditions. When the temperatures were elevated, the amylose-PCL and amylose-PLLA complexes were dissociated at 40 and 60 °C, respectively. We also found that amylose inclusion supramolecular polymers which were prepared by the vine-twining polymerization using primer-guest conjugates formed films by the acetylation of amylose segments. The film from acetylated amylose-PLLA supramolecular polymer had higher storage modulus than that from acetylated amylose-PTHF supramolecular polymer, as a function of temperature.

"Helix-in-Helix" Superstructure Formation through Encapsulation of Fullerene-Bound Helical Peptides within a Helical Poly(methyl methacrylate) Cavity

A one-handed 310 -helical hexapeptide is efficiently encapsulated within the helical cavity of st-PMMA when a fullerene (C60 ) derivative is introduced at the C-terminal end of the peptide. The encapsulation is accompanied by induction of a preferred-handed helical conformation in the st-PMMA backbone with the same-handedness as that of the hexapeptide to form a crystalline st-PMMA/peptide-C60 inclusion complex with a unique optically active helix-in-helix structure. Although the st-PMMA is unable to encapsulate the 310 -helical peptide without the terminal C60 unit, the helical hollow space of the st-PMMA is almost filled by the C60 -bound peptides. This result suggests that the C60 moiety can serve as a versatile molecular carrier of specific molecules and polymers in the helical cavity of the st-PMMA for the formation of an inclusion complex, thus producing unique supramolecular soft materials that cannot be prepared by other methods.

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

Precision Synthesis of Functional Polysaccharide Materials by Phosphorylase-Catalyzed Enzymatic Reactions

In this review article, the precise synthesis of functional polysaccharide materials using phosphorylase-catalyzed enzymatic reactions is presented. This particular enzymatic approach has been identified as a powerful tool in preparing well-defined polysaccharide materials. Phosphorylase is an enzyme that has been employed in the synthesis of pure amylose with a precisely controlled structure. Similarly, using a phosphorylase-catalyzed enzymatic polymerization, the chemoenzymatic synthesis of amylose-grafted heteropolysaccharides containing different main-chain polysaccharide structures (e.g., chitin/chitosan, cellulose, alginate, xanthan gum, and carboxymethyl cellulose) was achieved. Amylose-based block, star, and branched polymeric materials have also been prepared using this enzymatic polymerization. Since phosphorylase shows a loose specificity for the recognition of substrates, different sugar residues have been introduced to the non-reducing ends of maltooligosaccharides by phosphorylase-catalyzed glycosylations using analog substrates such as α-d-glucuronic acid and α-d-glucosamine 1-phosphates. By means of such reactions, an amphoteric glycogen and its corresponding hydrogel were successfully prepared. Thermostable phosphorylase was able to tolerate a greater variance in the substrate structures with respect to recognition than potato phosphorylase, and as a result, the enzymatic polymerization of α-d-glucosamine 1-phosphate to produce a chitosan stereoisomer was carried out using this enzyme catalyst, which was then subsequently converted to the chitin stereoisomer by N-acetylation. Amylose supramolecular inclusion complexes with polymeric guests were obtained when the phosphorylase-catalyzed enzymatic polymerization was conducted in the presence of the guest polymers. Since the structure of this polymeric system is similar to the way that a plant vine twines around a rod, this polymerization system has been named "vine-twining polymerization". Through this approach, amylose supramolecular network materials were fabricated using designed graft copolymers. Furthermore, supramolecular inclusion polymers were formed by vine-twining polymerization using primer⁻guest conjugates.

Enzymes as Green Catalysts for Precision Macromolecular Synthesis

The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.

Oligoamylose-entwined porphyrin: excited-state induced-fit for chirality induction

An oligoamylose-strapped porphyrin displayed circularly polarized luminescence (CPL) in the S₁ state despite being silent in circular dichroism (CD) in the ground state, suggesting chirality induction in the photoexcited porphyrin moiety from the oligoamylose-strap in the photoexcited state.

Electrostatically promoted dynamic hybridization of glucans with cationic polythiophene

A hetero-triplex composed of a glucan and a cationic polythiophene was dynamic and disassembled into a hetero-duplex in basic solutions.

Preparation of multiformable supramolecular gels through helical complexation by amylose in vine-twining polymerization

Supramolecular hydrogels with macroscopic interfacial healing behavior were obtained through helical complexation by amylose in vine-twining polymerization using poly(γ-glutamic acid-graft-ε-caprolactone), which were further converted into cryo- and ion gels.

Light-harvesting nanorods based on pheophorbide-appending cellulose

In contrast to the success in artificial DNA- and peptide-based nanostructures, the ability of polysaccharides to self-assemble into one-, two-, and three-dimensional nanostructures are limited. Here, we describe a strategy for designing and fabricating nanorods using a regioselectively functionalized cellulose derivative at the air-water interface in a stepwise manner. A semisynthetic chlorophyll derivative, pyro-pheophorbide a, was partially introduced into the C-6 position of the cellulose backbone for the design of materials with specific optical properties. Remarkably, controlled formation of cellulose nanorods can be achieved, producing light-harvesting nanorods that display a larger bathochromic shift than their solution counterparts. The results presented here demonstrate that the self-assembly of functionalized polysaccharides on surfaces could lead the nanostructures mimicking the naturally occurring chloroplasts.

Architecture of amylose supramolecules in form of inclusion complexes by phosphorylase-catalyzed enzymatic polymerization

This paper reviews the architecture of amylose supramolecules in form of inclusion complexes with synthetic polymers by phosphorylase-catalyzed enzymatic polymerization. Amylose is known to be synthesized by enzymatic polymerization using α-d-glucose 1-phosphate as a monomer, by phosphorylase catalysis. When the phosphorylase-catalyzed enzymatic polymerization was conducted in the presence of various hydrophobic polymers, such as polyethers, polyesters, poly(ester-ether), and polycarbonates as a guest polymer, such inclusion supramolecules were formed by the hydrophobic interaction in the progress of polymerization. Because the representation of propagation in the polymerization is similar to the way that a vine of a plant grows, twining around a rod, this polymerization method for the formation of amylose-polymer inclusion complexes was proposed to be named "vine-twining polymerization". To yield an inclusion complex from a strongly hydrophobic polyester, the parallel enzymatic polymerization system was extensively developed. The author found that amylose selectively included one side of the guest polymer from a mixture of two resemblant guest polymers, as well as a specific range in molecular weights of the guest polymers poly(tetrahydrofuran) (PTHF) in the vine-twining polymerization. Selective inclusion behavior of amylose toward stereoisomers of chiral polyesters, poly(lactide)s, also appeared in the vine-twining polymerization.

Preparation of polysaccharide supramolecular films by vine-twining polymerization approach

In this study, we investigated the preparation of polysaccharide supramolecular films through the formation of inclusion complexes by amylose in vine-twining polymerization using carboxymethyl cellulose-graft-poly(ε-caprolactone) (CMC-g-PCL) as a new guest polymer. First, hydrogels were prepared by phosphorylase-catalyzed enzymatic polymerization in the presence of CMC-g-PCL according to the vine-twining polymerization manner. The XRD result of a powdered sample obtained by lyophilization of the resulting hydrogel indicated the presence of inclusion complexes of amylose with the PCL graft-chains between intermolecular (CMC-g-PCL)s, which acted as supramolecular cross-linking points for the hydrogelation. Then, the supramolecular films were obtained by adding water to the powdered samples, followed by drying. The mechanical properties of the selected films examined by tensile testing were superior to those of a CMC film. The effect of the supramolecular cross-linking structures on the mechanical properties of the films was evaluated further by several investigations.

Amylose's recognition of chirality in polylactides on formation of inclusion complexes in vine-twining polymerization

Amylose selectively includes poly(L-lactide) (PLLA) among the poly(lactide)s (PLAs) to produce an inclusion complex when the phosphorylase-catalyzed polymerization of α-D-glucose 1-phosphate is performed in the presence of PLLA, poly(D-lactide) (PDLA), or poly(DL-lactide) (PDLLA) (vine-twining polymerization). This result indicates that amylose recognizes the chirality in PLAs on the formation of an inclusion complex in vine-twining polymerization. Modeling calculations support the amylose's chiral recognition in favor of PLLA and the atomistic details of the inclusion complex which involved the preferred orientation of the constituent molecular chains with respect to their fiber axis is proposed.

Colorimetric sensing method for polyamines utilising an inclusion complex of stimuli-responsive amylose

Incorporation of carboxyl groups into amylose led to a unique stimuli-responsive supramolecular system that shows distinct colour change in response to biologically important polyamines. When spermine was added to an aqueous solution containing iodine and amylose modified with carboxyl groups, the solution clearly changed from colourless to bluish purple. This colour change was attributed to the encapsulation of iodine into the helical cavity of amylose, which was triggered by the electrostatic association between the amylose and spermine.

'Supramolecular wrapping chemistry' by helix-forming polysaccharides: a powerful strategy for generating diverse polymeric nano-architectures

We have exploited novel supramolecular wrapping techniques by helix-forming polysaccharides, β-1,3-glucans, which have strong tendency to form regular helical structures on versatile nanomaterials in an induced-fit manner. This approach is totally different from that using the conventional interpolymer interactions seen in both natural and synthetic polymeric architectures, and therefore has potential to create novel polymeric architectures with diverse and unexpected functionalities. The wrapping by β-1,3-glucans enforces the entrapped guest polymer to adopt helical or twisted conformations through the convergent interpolymer interactions. On the contrary, the wrapping by chemically modified semi-artificial β-1,3-glucans can bestow the divergent self-assembling abilities on the entrapped guest polymer to create hierarchical polymeric architectures, where the polymer/β-1,3-glucan composite acts as a huge one-dimensional building block. Based on the established wrapping strategy, we have further extended the wrapping techniques toward the creation of three-dimensional polymeric architectures, in which the polymer/β-1,3-glucan composite behaves as a sort of amphiphilic block copolymers. The present wrapping system would open several paths to accelerate the development of the polymeric supramolecular assembly systems, giving the strong stimuli to the frontier of polysaccharide-based functional chemistry.