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

Synthesis and Characterization of Solvent-Invertible Amphiphilic Hollow Particles

Previous researches on solvent-dependent polymer systems mainly focus on amphiphilic invertible polymers (AIPs), which are capable of forming solvent-dependent micellar or inverse micellar assemblies. However, polymer particles that are invertible in response to solvent polarity are almost unexplored. In this paper, we report a new type of invertible hollow polymer (IHP) particle that is comprised of polyethylenimine-<i>g</i>-poly­(methyl methacrylate) (PEI-<i>g</i>-PMMA) copolymer. The amphiphilic PEI-<i>g</i>-PMMA hollow particles were first prepared through synthesis of well-defined PEI/PMMA core–shell particles, followed by removal of PMMA homopolymer from the core. The resulting IHP particles can be stably dispersed in both nonpolar solvent and water. We have investigated the morphology and surface property of the particles in both dichloromethane (DCM) and water using transmission electron microscopy, water contact angle measurement, and X-ray photoelectron spectroscopy analysis to gain insight into this unique particle dispersibility. Sustainability of the solvent-invertible property was carefully studied through repeated treatment of the IHP particles in DCM or water for up to six cycles. Solvent-dependent property of the dry films formed by IHP particles was also investigated through water contact angle measurement. Increasing water content on the DCM-treated IHP particle film could reduce the water contact angle from 94° to 51°. Our results demonstrate that the amphiphilic hollow particles are a new type of polymer design for smart materials that are invertible in response to nonpolar and aqueous media in both dispersed and solid states

Self-Assembly of Maltoheptaose-<i>block</i>-Polystyrene into Micellar Nanoparticles and Encapsulation of Gold Nanoparticles

The present paper discusses the controlled self-assembly of sugar-containing block copolymer, maltoheptaose-<i>block</i>-polystyrene (MH_1.2k-<i>b</i>-PS_4.5k), into micellar nanoparticles of ca. 30 nm radius in aqueous media and their possibility of gold encapsulation. Micellar association of MH_1.2k-<i>b</i>-PS_4.5k into nanoparticles was demonstrated by mixing a large amount of water (MH-selective solvent) with a solution of MH_1.2k-<i>b</i>-PS_4.5k in a mixture of tetrahydrofuran (THF) (PS-selective solvent) and water with a certain weight fraction [4:1 (w/w) THF/water], where MH_1.2k-<i>b</i>-PS_4.5k exists as well-swollen single chains, followed by evaporation of THF. The mean hydrodynamic radii (<i>R</i>_h) of the nanoparticles were determined by dynamic light scattering (DLS) to be ca. 30 and 80 nm depending upon the method of preparation. The resulting nanoparticles were clearly visualized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and field emission gun–scanning electron microscopy (FEG−SEM) imaging and complemented by nanoparticle tracking analysis (NTA) using a NanoSight instrument. The preliminary study of the self-assembly of MH_1.2k-<i>b</i>-PS_4.5k in the presence of gold nanoparticles functionalized with PS chains grafted on their surface indicated potential possibilities of encapsulation of gold nanoparticles into the block copolymer nanoparticles in aqueous media

Self-Assembly of Maltoheptaose-<i>block</i>-Polystyrene into Micellar Nanoparticles and Encapsulation of Gold Nanoparticles

The present paper discusses the controlled self-assembly of sugar-containing block copolymer, maltoheptaose-<i>block</i>-polystyrene (MH_1.2k-<i>b</i>-PS_4.5k), into micellar nanoparticles of ca. 30 nm radius in aqueous media and their possibility of gold encapsulation. Micellar association of MH_1.2k-<i>b</i>-PS_4.5k into nanoparticles was demonstrated by mixing a large amount of water (MH-selective solvent) with a solution of MH_1.2k-<i>b</i>-PS_4.5k in a mixture of tetrahydrofuran (THF) (PS-selective solvent) and water with a certain weight fraction [4:1 (w/w) THF/water], where MH_1.2k-<i>b</i>-PS_4.5k exists as well-swollen single chains, followed by evaporation of THF. The mean hydrodynamic radii (<i>R</i>_h) of the nanoparticles were determined by dynamic light scattering (DLS) to be ca. 30 and 80 nm depending upon the method of preparation. The resulting nanoparticles were clearly visualized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and field emission gun–scanning electron microscopy (FEG−SEM) imaging and complemented by nanoparticle tracking analysis (NTA) using a NanoSight instrument. The preliminary study of the self-assembly of MH_1.2k-<i>b</i>-PS_4.5k in the presence of gold nanoparticles functionalized with PS chains grafted on their surface indicated potential possibilities of encapsulation of gold nanoparticles into the block copolymer nanoparticles in aqueous media

Self-Assembly of Maltoheptaose-<i>block</i>-Polystyrene into Micellar Nanoparticles and Encapsulation of Gold Nanoparticles

The present paper discusses the controlled self-assembly of sugar-containing block copolymer, maltoheptaose-<i>block</i>-polystyrene (MH_1.2k-<i>b</i>-PS_4.5k), into micellar nanoparticles of ca. 30 nm radius in aqueous media and their possibility of gold encapsulation. Micellar association of MH_1.2k-<i>b</i>-PS_4.5k into nanoparticles was demonstrated by mixing a large amount of water (MH-selective solvent) with a solution of MH_1.2k-<i>b</i>-PS_4.5k in a mixture of tetrahydrofuran (THF) (PS-selective solvent) and water with a certain weight fraction [4:1 (w/w) THF/water], where MH_1.2k-<i>b</i>-PS_4.5k exists as well-swollen single chains, followed by evaporation of THF. The mean hydrodynamic radii (<i>R</i>_h) of the nanoparticles were determined by dynamic light scattering (DLS) to be ca. 30 and 80 nm depending upon the method of preparation. The resulting nanoparticles were clearly visualized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and field emission gun–scanning electron microscopy (FEG−SEM) imaging and complemented by nanoparticle tracking analysis (NTA) using a NanoSight instrument. The preliminary study of the self-assembly of MH_1.2k-<i>b</i>-PS_4.5k in the presence of gold nanoparticles functionalized with PS chains grafted on their surface indicated potential possibilities of encapsulation of gold nanoparticles into the block copolymer nanoparticles in aqueous media

Self-Assembly of Carbohydrate-<i>block</i>-Poly(3-hexylthiophene) Diblock Copolymers into Sub-10 nm Scale Lamellar Structures

We here report the synthesis of a new class of carbohydrate-based block copolymers, poly­(3-hexylthiophene)-<i>block</i>-peracetylated maltoheptaose (P3HT-<i>b</i>-AcMal₇) and poly­(3-hexylthiophene)-<i>block</i>-maltoheptaose (P3HT-<i>b</i>-Mal₇), and their bulk and self-assembled thin films morphological characterizations by atomic force microscopy, transmission electron microscopy, and small-angle X-ray scattering. The block copolymers were synthesized via copper­(I)-catalyzed 1,3-dipolar azide–alkyne cycloaddition of azido-functionalized AcMal₇ and end-functionalized P3HT with alkyne group prepared by modified Grignard metathesis polymerization, followed by deacetylation of the AcMal₇ block. The half-pitch of sub-10 nm scale lamellar structures, one of the smallest domain sizes of microphase separated block copolymers reported to date, was self-organized in the bulk and thin films of P3HT-<i>b</i>-AcMal₇ by thermal annealing above the melting temperature of the P3HT segment. Meanwhile, thermodynamic microphase separation of P3HT-<i>b</i>-Mal₇ was restricted due to strong inter- and intrachain hydrogen bonding among the hydroxyl groups of the Mal₇ block, which was confirmed by an <i>in situ</i> stepwise heating and cooling Fourier transform infrared spectroscopy study

Sub-10 nm Scale Nanostructures in Self-Organized Linear Di- and Triblock Copolymers and Miktoarm Star Copolymers Consisting of Maltoheptaose and Polystyrene

The present paper describes the sub-10 nm scale self-assembly of AB-type diblock, ABA-type triblock, and A₂B-type miktoarm star copolymers consisting of maltoheptaose (MH: A block) and polystyrene (PS: B block). These block copolymers (BCPs) were synthesized through coupling of end-functionalized MH and PS moieties. Small-angle X-ray scattering and atomic force microscope investigations indicated self-organized cylindrical and lamellar structures in the BCP bulks and thin films with domain spacing (<i>d</i>) ranging from 7.65 to 10.6 nm depending on the volume fraction of MH block (ϕ_MH), Flory–Huggins interaction parameter (χ), and degree of polymerization (<i>N</i>). The BCP architecture also governed the morphology of the BCPs, e.g. the AB-type diblock copolymer (ϕ_MH = 0.42), the ABA-type triblock copolymer (ϕ_MH = 0.40), and the A₂B-type miktoarm star copolymer (ϕ_MH = 0.45) self-organized into cylinder (<i>d</i> = 7.65 nm), lamellar (<i>d</i> = 8.41 nm), and lamellar (<i>d</i> = 9.21 nm) structures, respectively

Glyco-Nanoparticles Made from Self-Assembly of Maltoheptaose-<i>block</i>-Poly(methyl methacrylate): Micelle, Reverse Micelle, and Encapsulation

The synthesis and the solution-state self-assembly of the “hybrid” diblock copolymers, maltoheptaose-<i>block</i>-poly­(methyl methacrylate) (MH-<i>b</i>-PMMA), into large compound micelles (LCMs) and reverve micelle-type nanoparticles, are reported in this paper. The copolymers were self-assembled in water and acetone by direct dissolution method, and the morphologies of the nanoparticles were investigated by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), atomic force microscopy (AFM), proton nuclear magnetic resonance (¹H NMR), and fluorescence spectroscopy as a function of the volume fraction of the copolymer hydrophobic block, copolymer concentration, stirring speed, and solvent polarity. The DLS measurements and TEM images showed that the hydrodynamic radius (<i>R</i>_h) of the LCMs obtained in water increases with the copolymer concentration. Apart from that, increasing the stirring speed leads to polydispersed aggregations of the LCMs. On the other hand, in acetone, the copolymers self-assembled into reverse micelle-type nanoparticles having <i>R</i>_h values of about 6 nm and micellar aggregates, as revealed the results obtained from DLS, AFM, and ¹H NMR analyses. The variation in micellar structure, that is, conformational inversion from LCMs to reverse micelle-type structures in response to polarity of the solvent, was investigated by apparent water contact angle (WCA) and ¹H NMR analyses. This conformational inversion of the nanoparticles was further confirmed by encapsulation and release of hydrophobic guest molecule, Nile red, characterized by fluorescence spectroscopy

Maltopentaose-Conjugated CTA for RAFT Polymerization Generating Nanostructured Bioresource-Block Copolymer

We now describe the synthesis of a new family of oligosaccharide-conjugated functional molecules, which act as chain transfer agents (CTAs) for the reversible addition–fragmentation chain transfer (RAFT) polymerization. The synthesis was started from the catalyst-free direct <i>N</i>-glycosyl reaction of 5-azidopentylamine onto maltopentaose (Mal₅) in dry methanol at room temperature and subsequent <i>N</i>-protected reaction with acetic anhydride, producing a stable oligosaccharide-building block, such as Mal₅ with an azidopentyl group (Mal₅-N₃). The azido group was hydrogenated using platinum dioxide (PtO₂) as a catalyst to give Mal₅ with aminopentyl group (Mal₅-NH₂), which was then reacted with CTA molecules bearing activated ester moieties. These reactions produced Mal₅-modified macro-CTAs (Mal₅-CTAs, <b>1</b>), which were used for the RAFT polymerizations of styrene (St) and methyl methacrylate (MMA) in DMF. The polymerizations were performed using the [M]₀/[<b>1</b>]₀ values ranging from 50 to 600, affording the Mal₅-hybrid amphiphilic block copolymers (BCPs), such as Mal₅-polystyrene (<b>2</b>) and Mal₅-poly­(methyl methacrylate) (<b>3</b>), with a quantitative end-functionality and the controlled molecular weights between 4310 and 20 300 g mol^–1. The small-angle X-ray scattering (SAXS) measurements were accomplished for <b>2</b> and <b>3</b> to ensure their abilities to form phase separated structures in their bulk states with the increasing temperatures from 30 to 190 °C. The featured results were observed for <b>2</b> (ϕ_Mal5 = 0.14) and <b>3</b> (ϕ_Mal5 = 0.16) at temperatures above 100 °C, where ϕ_Mal5 denotes the volume fraction of the Mal₅ unit in the BCP sample. For both BCP samples, the primary scattering peaks <i>q</i>* were clearly observed together with the higher-ordered scattering peaks √2<i>q</i>* and √3<i>q</i>*. Thus, these Mal₅-hybrid amphiphilic BCP samples have a body centered cubic (BCC) phase morphology. The domain spacing (<i>d</i>) values of the BCC morphology for <b>2</b> (ϕ_Mal5 = 0.14) and <b>3</b> (ϕ_Mal5 = 0.16) were 10.4 and 9.55 nm, respectively, which were determined using Bragg’s relation (<i>d</i> = 2π/<i>q</i>*). The present RAFT agents were shown to eventually provide the phase separated structural polymeric materials in which 5.4 nm bioresource-spherical domains were periodically arrayed at the interval of about 10 nm

Redox-Active Carbohydrate-Coated Nanoparticles: Self-Assembly of a Cyclodextrin–Polystyrene Glycopolymer with Tetrazine–Naphthalimide

The controlled self-assembly of precise and well-defined photochemically and electrochemically active carbohydrate-coated nanoparticles offers the exciting prospect of biocompatible catalysts for energy storage/conversion and biolabeling applications. Here an aqueous nanoparticle system has been developed with a versatile outer layer for host–guest molecule encapsulation via β-cyclodextrin inclusion complexes. A β-cyclodextrin-modified polystyrene polymer was first obtained by copper nanopowder click chemistry. The glycopolymer enables self-assembly and controlled encapsulation of tetrazine-naphthalimide, as a model redox-active agent, into nanoparticles via nanoprecipitation. Cyclodextrin host–guest interactions permit encapsulation and internanoparticle cross-linking for the formation of fluorescent compound and clustered self-assemblies with chemically reversible electroactivity in aqueous solution. Light scattering experiments revealed stable particles with hydrodynamic diameters of 138 and 654 nm for nanoparticles prepared with tetrazine, of which 95% of the nanoparticles represent the smaller objects by number. Dynamic light scattering revealed differences as a function of preparation method in terms of size, 3-month stability, polydispersity, radius of gyration, and shape factor. Individual self-assemblies were visualized by atomic force microscopy and fluorescence microscopy and monitored in real-time by nanoparticle tracking analysis. UV–vis and fluorescence spectra provided insight into the optical properties and critical evidence for host–guest encapsulation as evidenced by solvachromatism and enhanced tetrazine uptake. Cyclic voltammetry was used to investigate the electrochemical properties and provided further support for encapsulation and an estimate of the tetrazine loading capacity in tandem with light scattering data