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

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

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

Synthesis, Self-Assembly, and Thermal Caramelization of Maltoheptaose-Conjugated Polycaprolactones Leading to Spherical, Cylindrical, and Lamellar Morphologies

Three different self-assembled nanostructures, i.e., lamellar (Lam), hexagonally close-packed cylinder (Hex), and body-centered cubic (BCC), have been obtained from ABA triblock (MH-<i>b</i>-PCL-<i>b</i>-MH) and A₂B star-branched copolymers ((MH)₂-<i>b</i>-PCL) consisting of maltoheptaose (MH, as the A block) and polycaprolactone (PCL, as the B block). MH-<i>b</i>-PCL-<i>b</i>-MH and (MH)₂-<i>b</i>-PCL were synthesized by the click reaction of the α,ω-diazido and α,α-diazido end-functionalized PCLs with <i>N</i>-maltoheptaosyl-3-acetamido-1-propyne in high yields. The self-assembled nanostructures of the block copolymers (BCPs) in bulk were investigated as a function of temperature by time-resolved small-angle X-ray scattering using a synchrotron light source. The SAXS analysis revealed that the obtained BCPs exhibited microphase-separated structures with the domain-spacing of 10.4–21.0 nm. MH-<i>b</i>-PCL-<i>b</i>-MH (the MH volume fraction (ϕ_MH) of 0.28 and 0.15) exhibited a hexagonally close-packed cylinder (Hex) at below ca. 230 °C, and the self-assembling behavior of MH-<i>b</i>-PCL-<i>b</i>-MH was essentially the same as that of the diblock counterpart, MH-<i>b</i>-PCL, having comparable ϕ_MH values. The lamellar (Lam) morphology, which was unattainable from the corresponding linear counterparts, was observed from (MH)₂-<i>b</i>-PCL (ϕ_MH = 0.27 and 0.16). Furthermore, the microphase transitions from the Hex into the body-centered cubic sphere and the Lam into the Hex were observed upon the thermal caramelization of the MH block

Synthesis and Stereocomplex Formation of Star-Shaped Stereoblock Polylactides Consisting of Poly(l‑lactide) and Poly(d‑lactide) Arms

The synthesis of star-shaped polylactides (PLAs) having both poly­(l-lactide) (PLLA) and poly­(d-lactide) (PDLA) arms in one molecule, i.e., stereo-miktoarm star-shaped PLAs, is described. The azido-functionalized PDLAs and ethynyl-functionalized PLLA possessing linear and two- and three-branched structures were prepared by the ring-opening polymerization of d-lactide and l-lactide using azido- or ethynyl-functionalized initiators. The number-average molecular weights (<i>M</i>_n,NMRs) of the PLAs were ca. 5000 g mol^–1 with narrow molecular weight distributions (<i>M</i>_w/<i>M</i>_ns) of less than 1.18. The click reaction of the azido-functionalized PDLAs and the ethynyl-functionalized PLLAs using the copper­(I) bromide/<i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>″,<i>N</i>″-pentamethyldiethylenetriamine catalyst in a mixed solvent of dichloromethane/1,1,1,3,3,3-hexafluoro-2-propanol (14/1, v/v) gave a linear stereoblock PLA as well as 3-, 4-, 5-, and 6-armed stereo-miktoarm star-shaped PLAs with <i>M</i>_n,NMRs of ca. 10 000 g mol^–1 and <i>M</i>_w/<i>M</i>_ns of less than 1.16. The wide-angle X-ray scattering and differential scanning calorimetry measurements proved that these stereo-miktoarm star-shaped PLAs formed stereocomplex crystals without any trace of homochiral crystallization

Sub-10 nm Nano-Organization in AB₂- and AB₃‑Type Miktoarm Star Copolymers Consisting of Maltoheptaose and Polycaprolactone

The AB₂- and AB₃-type miktoarm star copolymers consisting of maltoheptaose (MH, as A block) and poly­(ε-caprolactone) (PCL, as B block), namely MH-<i>b</i>-(PCL)₂ and MH-<i>b</i>-(PCL)₃, were synthesized, and their nano-organization was characterized. The syntheses of MH-<i>b</i>-(PCL)₂ and MH-<i>b</i>-(PCL)₃ were carried out through two reaction steps: (1) preparation of linear and three-branched PCLs bearing an azido group on the chain center (N₃-(PCL)₂ and N₃-(PCL)₃) by the diphenyl phosphate-catalyzed ring-opening polymerization of ε-caprolactone (ε-CL) using azido-functionalized di- and triols (N₃-(OH)₂ and N₃-(OH)₃) as the initiators and (2) the copper-catalyzed azide–alkyne cycloaddition of N₃-(PCL)₂ and N₃-(PCL)₃ with the ethynyl-functionalized MH. The miktoarm star copolymers having <i>M</i>_n for the PCL block of ca. 5000 (MH-<i>b</i>-(PCL_2.5k)₂ and MH-<i>b</i>-(PCL_1.7k)₃) and 10 000 (MH-<i>b</i>-(PCL_5k)₂ and MH-<i>b</i>-(PCL_3.3k)₃) were obtained with a very narrow polydispersity index of less than 1.05. Bulk samples of the four types of miktoarm star copolymers exhibited body-centered cubic phases, as determined by small-angle X-ray diffraction experiments. The domain-spacing were determined to be 9.8 nm for MH-<i>b</i>-(PCL_2.5k)₂, 8.8 nm for MH-<i>b</i>-(PCL_1.7k)₃, 10.5 nm for MH-<i>b</i>-(PCL_5k)₂, and 9.8 nm for MH-<i>b</i>-(PCL_3.3k)₃, which were smaller than those of the corresponding linear diblock copolymers