Highly Ordered Cylinder Morphologies with 10 nm Scale Periodicity in Biomass-Based Block Copolymers

Microphase-separated structures of block copolymers (BCPs) have attracted considerable attention for their potential application in the bottom-up fabrication of 10 nm scale nanostructured materials. To realize sustainable development within this field, the creation of novel BCP materials from renewable biomass resources is of fundamental interest. Thus, we herein focused on maltoheptaose-<i>b</i>-poly­(δ-decanolactone)-<i>b</i>-maltoheptaose (MH-<i>b</i>-PDL-<i>b</i>-MH) as a sustainable alternative for nanostructure-forming BCPs, in which both constitutional blocks can be derived from renewable biomass resources, in the case, δ-decanolactone and amylose. Well-defined MH-<i>b</i>-PDL-<i>b</i>-MHs with varying PDL lengths were synthesized through a combination of controlled/living ring-opening polymerization and the click reaction. The prepared MH-<i>b</i>-PDL-<i>b</i>-MHs successfully self-assembled into highly ordered hexagonal cylindrical structures with a domain-spacing of ∼12–14 nm in both the bulk and thin film states. Interestingly, the as-cast thin films of MH-<i>b</i>-PDL-<i>b</i>-MHs (with PDL lengths of 9K and 13K) form horizontal cylinders, with thermal annealing (180 °C, 30 min) resulting in a drastic change in the domain orientation from horizontal to vertical. Thus, the results presented herein demonstrated that the combination of oligosaccharides and biomass-derived hydrophobic polymers appears promising for the sustainable development of nanotechnology and related fields

Engineering of a Tyrosol-Producing Pathway, Utilizing Simple Sugar and the Central Metabolic Tyrosine, in Escherichia coli

Metabolic engineering was applied to the development of Escherichia coli capable of synthesizing tyrosol (2-(4-hydroxyphenyl)­ethanol), an attractive phenolic compound with great industrial value, from glucose, a renewable carbon source. In this strain, tyrosine, which was supplied not only from the culture medium but also from the central metabolism, was converted into tyrosol via three steps: decarboxylation, amine oxidation, and reduction. The engineered strain synthesized both tyrosol and 4-hydroxyphenylacetate (4HPA), but disruption of the endogenous phenylacetaldehyde dehydrogenase gene shut off 4HPA production and improved the production of tyrosol as a sole product. The engineered mutant strain was capable of producing 0.5 mM tyrosol from 1% (w/v) glucose during a 48 h shake flask cultivation

Synthesis of Well-Defined Three- and Four-Armed Cage-Shaped Polymers via “Topological Conversion” from Trefoil- and Quatrefoil-Shaped Polymers

This paper describes a novel synthetic approach for three- and four-armed cage-shaped polymers based on the topological conversion of the corresponding trefoil- and quatrefoil-shaped precursors. The trefoil- and quatrefoil-shaped polymers were synthesized by the following three reaction steps: (1) the <i>t</i>-Bu-P₄-catalyzed ring-opening polymerization of butylene oxide using multiple hydroxy- and azido-functionalized initiators to produce the three- or four-armed star-shaped polymers possessing three or four azido groups at the focal point, respectively, (2) the ω-end modification to install a propargyl group at each chain end, and (3) the intramolecular multiple click cyclization of the clickable star-shaped precursors. The topological conversion from the trefoil- and quatrefoil-shaped polymers to the cage-shaped polymers was achieved by the catalytic hydrogenolysis of the benzyl ether linkages that had been installed at the focal point. The amphiphilic cage-shaped block copolymers together with the corresponding trefoil- and quatrefoil-shaped counterparts were synthesized in a similar way using 2-(2-(2-methoxyethoxy)­ethoxy)­ethyl glycidyl ether as a hydrophilic monomer and decyl glycidyl ether as a hydrophobic monomer. Interestingly, significant changes in the critical micelle concentration and micellar morphology were observed for the amphiphilic block copolymers upon the topological conversion from the trefoil- and quatrefoil-shaped to cage-shaped architectures

Chemically Recyclable Unnatural (1→6)-Polysaccharides from Cellulose-Derived Levoglucosenone and Dihydrolevoglucosenone

Unnatural polysaccharide analogs and their biological activities and material properties have attracted considerable research interest. However, these efforts often encounter challenges, especially those related to synthetic complexity and scalability. Here, we report the chemical synthesis of unnatural (1→6)-polysaccharides using levoglucosenone (LGO) and dihydrolevoglucosenone (Cyrene), which are derived from cellulose. Using a versatile monomer synthesis from LGO and Cyrene and cationic ring-opening polymerization, (1→6)-polysaccharides with various tailored substituent patterns are obtained. Additionally, environmentally benign and easy-to-handle organic Brønsted acid catalysts are investigated. This study demonstrates well-controlled first-order polymerization kinetics for the reactive (1S,5R)-6,8-dioxabicyclo[3,2,1]octane (DBO) monomer. The synthesized (1→6)-polysaccharides exhibit high thermal stability and form amorphous solids under ambient conditions, which could be processed into highly transparent self-standing films. Additionally, these polymers exhibit excellent closed-loop chemical recyclability. This study provides an important approach to explore the chemical spaces of unnatural polysaccharides and contributes to the development of sustainable polymer materials from abundant biomass resources

Multicyclic Polymer Synthesis through Controlled/Living Cyclopolymerization of α,ω-Dinorbornenyl-Functionalized Macromonomers

A novel synthesis of multicyclic polymers that feature ultradense arrays of cyclic polymer units has been developed by exploiting the cyclopolymerization of α,ω-norbornenyl end-functionalized macromonomers mediated by the Grubbs third-generation catalyst (G3). Owing to the living polymerization nature, the number of cyclic repeating units in these multicyclic polymers was controlled to be between 1 and approximately 70 by varying the initial macromonomer-to-G3 ratio. The ring size was also tuned by choosing the molecular weight of the macromonomer; in this way we successfully prepared multicyclic polymers that possess cyclic repeating units composed of up to about 500 atoms, which by far exceeds those prepared to date by cyclopolymerization. Specifically, cyclopolymerizations of α,ω-norbornenyl end-functionalized poly­(l-lactide)­s (PLLAs) proceeded homogeneously under highly dilute conditions (∼0.1 mM in CH₂Cl₂) to give multicyclic polymers that feature cyclic PLLA repeating units on the polynorbornene backbone. The cyclic product architectures were confirmed not only by structural characterization based on NMR, MALDI-TOF MS, and SEC analyses but also by comparing their glass transition temperatures, viscosities, and hydrodynamic radii with their acyclic counterparts. The cyclopolymerization strategy was applicable to a variety of α,ω-norbornenyl end-functionalized macromonomers, such as poly­(ε-caprolactone), poly­(ethylene glycol) (PEG), poly­(tetrahydrofuran), and PLLA-<i>b</i>-PEG-<i>b</i>-PLLA. The successful statistical and block cyclocopolymerizations of the PLLA and PEG macromonomers gave amphiphilic multicyclic copolymers

One-Step Production of Amphiphilic Nanofibrillated Cellulose Using a Cellulose-Producing Bacterium

Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium (Gluconacetobacter intermedius NEDO-01) with rotation or agitation in medium supplemented with carboxymethylcellulose (CMC). Despite a high yield and dispersibility in water, the product immediately aggregates in organic solvents. To broaden its applicability, we prepared amphiphilic NFBC by culturing strain NEDO-01 in medium supplemented with hydroxyethylcellulose or hydroxypropylcellulose instead of CMC. Transmission electron microscopy analysis revealed that the resultant materials (HE-NFBC and HP-NFBC, respectively) comprised relatively uniform fibers with diameters of 33 ± 7 and 42 ± 8 nm, respectively. HP-NFBC was dispersible in polar organic solvents such as methanol, acetone, isopropyl alcohol, acetonitrile, tetrahydrofuran (THF), and dimethylformamide, and was also dispersible in poly­(methyl methacrylate) (PMMA) by solvent mixing using THF. HP-NFBC/PMMA composite films were highly transparent and had a higher tensile strength than neat PMMA film. Thus, HP-NFBC has a broad range of applications, including as a filler material

Stereoblock-like Brush Copolymers Consisting of Poly(l‑lactide) and Poly(d‑lactide) Side Chains along Poly(norbornene) Backbone: Synthesis, Stereocomplex Formation, and Structure–Property Relationship

Random and block copolymerizations of poly­(l-lactide) (PLLA) and poly­(d-lactide) (PDLA) macromonomers having an <i>exo</i>-norbornene group at the α- or ω-chain end (D/L ratio = 1/1, <i>M</i>_n = ca. 5000 g mol^–1) were performed via ring-opening metathesis polymerization to produce the brush random and block copolymers consisting of parallel or antiparallel aligned PLLA and PDLA side chains on a poly­(norbornene) backbone. The molecular weight and polydispersity index of the brush copolymers were in the range of 40 300–458 000 g mol^–1 and 1.03–1.14, respectively. Despite such high molecular weights, these brush copolymers formed a stereocomplex without homochiral crystallization. The melting temperature (<i>T</i>_m) and crystallinity (<i>X</i>) of the resulting stereocomplex varied depending on the backbone length, relative chain direction, and distribution of the PLLA/PDLA side chains. The parallel brush copolymers showed significantly higher <i>T</i>_m and <i>X</i> values than the antiparallel ones

Self-Assembly of Maltoheptaose-<i>block</i>-polycaprolactone Copolymers: Carbohydrate-Decorated Nanoparticles with Tunable Morphology and Size in Aqueous Media

This paper describes the systematic investigation into the aqueous self-assembly of a series of block copolymers (BCPs) consisting of maltoheptaose (MH; as the A block) and poly­(ε-caprolactone) (PCL; as the B block), i.e., linear AB-type diblock copolymers with varied PCL molecular weights (MH-<i>b</i>-PCL_{(2.5k,3.3k,5k,10k)}), AB_<i>y</i>-type (<i>y</i> = 2, MH-<i>b</i>-(PCL_5k)₂; <i>y</i> = 3, MH-<i>b</i>-(PCL_3.3k)₃), A₂B₂-type ((MH)₂-<i>b</i>-(PCL_5k)₂), and A_<i>x</i>B-type miktoarm star polymers (<i>x</i> = 2, (MH)₂-<i>b</i>-PCL_10k; <i>x</i> = 3, (MH)₃-<i>b</i>-PCL_10k), which had been precisely synthesized via the combination of the living ring-opening polymerization and click reaction. Under similar conditions, the nanoprecipitation method was employed to self-assemble them in an aqueous medium. Imaging and dynamic light scattering techniques indicated the successful formation of the carbohydrate-decorated nanoparticles via self-assembly. The MH-<i>b</i>-PCLs formed regular core–shell micellar nanoparticles with the hydrodynamic radius (<i>R</i>_h) of 17–43 nm. MH-<i>b</i>-(PCL_5k)₂ and MH-<i>b</i>-(PCL_3.3k)₃, which have an <i>N</i>_PCL comparable to MH-<i>b</i>-PCL_10k, were found to form large compound micelles with relatively large radii (<i>R</i>_h of 49 and 56 nm, respectively). On the other hand, (MH)₂-<i>b</i>-(PCL_5k)₂, (MH)₂-<i>b</i>-PCL_10k, and (MH)₃-<i>b</i>-PCL_10k predominantly formed the regular core–shell micellar nanoparticles (<i>R</i>_h = 29–39 nm) with a size smaller than that of MH-<i>b</i>-PCL_10k (<i>R</i>_h = 43 nm)