Self-Assembly-Assisted Biomolecule-Enriched Surface and High Selectivity Performance of Simple Solution-Coatable Biomimicking Brush Copolymers

Poly­(oxy­(11-(biotinyl)­undecylthiomethyl)­ethylene-<i>co</i>-oxy­(11-phosphoryl-cholineundecylthiomethyl)­ethylene)­s (PECH-BT_<i>m</i>PC_<i>n</i>: <i>m</i> = 0–100 mol % biotin (BT)-containing bristle; <i>n</i> = 100–0 mol % phosphorylcholine (PC)-containing bristle) were newly synthesized. All polymers exhibited excellent solution processability. They favorably self-assembled horizontal multibilayer structures in thin films with BT- and PC-enriched surfaces, which were driven by the lateral ordering of the fully extended upright bristles and the partial interdigitation between the BT and PC end groups of the bristles. Both hydrophilicity and water sorption of the films increased with the PC content. The PECH-BT₁₀₀ films revealed remarkably distinctive sensitivity, selectivity, and adsorption ability for avidin against other proteins. Such remarkable performance was further significantly enhanced on the PECH-BT_<i>m</i>PC_<i>n</i> films in which PC moieties were incorporated to the BT-rich surface; in particular, the PECH-BT₇₅PC₂₅ films demonstrated the highest performance. Overall, the self-assembly brush copolymers of this study are very suitable for use in the high performance detection, adsorption, and separation of proteins and receptors, including avidin, which can reveal high affinity and selectivity to BT moiety

Well-Defined Biomimicking Brush-Polymer Self-Assemblies Revealing Cholesterol- and Phosphorylcholine-Enriched Surface

We have newly synthesized a series of well-defined brush polyethers bearing cholesterol (Chol) and phosphorylcholine (PC) moieties in various compositions which can mimic cell membrane. They were thermally stable up to at least 230 °C and soluble in common solvents, showing good solution processability. Excitingly, they all favorably self-assembled, forming multibilayer structures with 2₁ chain conformation; in comparison, the brush polyether bearing only PC-bristles formed orthorhombically packed cylinder (OPC) structure with 12₅ helical chain conformation. Such multibilayer structure formations could be driven by a strong self-assembling ability of the Chol-bristle in extended conformation; the multibilayer structure formation was further promoted by the presence of PC-bristles. The OPC structure formation could be driven by a lateral packing ability of the brush polymer chain in the helical confirmation resulted from the minimization of repulsive interactions in the neighbored zwitterionic PC-bristles. Because of such the self-assembling natures, all brush polymers always revealed Chol- and PC-enriched surface. Overall, all brush polyethers of this study successfully mimicked cell membrane features (Chol- and PC-surface based on self-assembling). They are very suitable for uses in the fields required cell membrane surface characteristics

Hierarchical Self-Assembly and Digital Memory Characteristics of Crystalline–Amorphous Brush Diblock Copolymers Bearing Electroactive Moieties

Two series of crystalline–amorphous brush diblock copolymers bearing electroactive moieties were newly synthesized by sequential anionic ring-opening copolymerizations of glycidyl derivatives and subsequent selective postfunctionalizations; their homopolymers and analogues were additionally synthesized. Self-assembly structural details and electrical memory behaviors of these polymers in nanoscale thin films were investigated. The diblock copolymers revealed complex hierarchical self-assembly structures depending on the compositions. The self-assembly structure and orientation of the crystalline block chains were severely affected by the geometrical confinement (i.e., size and shape) stemming from microphase separation. Such film morphologies were found to significantly influence the electrical properties; they exhibited electrical properties from p-type permanent memory behavior to dielectric-like behavior. The memory behaviors were governed by the trap-limited space charge limited conduction mechanism combined with ohmic conduction and the hopping paths composed of the electroactive moieties distributed locally

2,2′-Bis(1,3,4-thiadiazole)-Based π‑Conjugated Copolymers for Organic Photovoltaics with Exceeding 8% and Its Molecular Weight Dependence of Device Performance

A series of novel π-conjugated copolymers based on 2,2′-bis­(1,3,4-thiadiazole) (BTDz) have been developed. Among them, the BTDz-based donor–acceptor alternating copolymer with the (<i>E</i>)-1,2-di­(3-(2-ethyl­hexyl)­thiophene)­vinylene donor unit (PBTDzTV) exhibited a high solubility and high crystallinity. PBTDzTVs favorably self-assembled, forming face-on and edge-on multibilayer structures in thin nanoscale films. The relative volume fractions of these structures varied depending on the polymer’s molecular weight. The higher molecular weight polymer formed a higher volume fraction of the face-on structure; in particular, the polymer with a 26.6 kDa of number-average molecular weight made only the face-on structure. The device performance was improved as the polymer molecular weight and the volume fraction of the face-on structure increased. The bulk-heterojunction photovoltaic device based on PBTDzTV:PC₇₁BM demonstrated the high power conversion efficiency (PCE) of 8.04% when the device was fabricated with the highest molecular weight polymer having the face-on structure

Synthesis, Thermal Properties, and Morphologies of Amphiphilic Brush Block Copolymers with Tacticity-Controlled Polyether Main Chain

A series of brush block copolymers (BBCPs) consisting of poly­(decyl glycidyl ether) (PDGE) and poly­(10-hydroxyldecyl glycidyl ether) (PHDGE) blocks, having four different types of chain tacticities, i.e., [<i>at</i>-PDGE]-<i>b</i>-[<i>at</i>-PDEGE], [<i>at</i>-PDGE]-<i>b</i>-[<i>it</i>-PDEGE], [<i>it</i>-PDGE]-<i>b</i>-[<i>at</i>-PDEGE], and [<i>it</i>-PDGE]-<i>b</i>-[<i>it</i>-PDEGE], where the <i>it</i> and <i>at</i> represent the isotactic and atactic chains, respectively, were prepared by <i>t</i>-Bu-P₄-catalyzed sequential anionic ring-opening polymerization of glycidyl ethers followed by side-chain modification. The corresponding homopolymers, i.e., <i>at</i>-PDGE, <i>it</i>-PDGE, <i>at</i>-PHDGE, and <i>it</i>-PHDGE, were also prepared for comparison with the BBCPs. The PDGE homopolymers were significantly promoted in the phase transitions and morphological structure formation by the isotacticity formation. In particular, <i>it</i>-PDGE was found to form only a horizontal multibilayer structure with a monoclinic lattice in thin films, which was driven by the bristles’ self-assembling ability and enhanced by the isotacticity. However, the PHDGE homopolymers were found to reveal somewhat different behaviors in the phase transitions and morphological structure formation by the tacticity control due to the additional presence of a hydroxyl group in the bristle end as an H-bonding interaction site. The H-bonding interaction could be enhanced by the isotacticity formation. The <i>it</i>-PHDGE homopolymer formed only the horizontal multibilayer structure, which was different from the formation of a mixture of horizontal and tilted multibilayer structures in <i>at</i>-PHDGE. The structural characteristics were further significantly influenced by the diblock formation and the tacticity of the counterpart block. Because of the strong self-assembling characteristics of the individual block components, all the BBCPs formed separate crystals rather than cocrystals. The isotacticity always promoted the formation of better quality morphological structures in terms of their lateral ordering and orientation

New Fullerene-Based Polymers and Their Electrical Memory Characteristics

Covalent incorporations into polymers of fullerene were achieved via the Cu­(I)-catalyzed azide–alkyne click polymerizations of a fullerene derivative monomer functionalized with 5-(trimethylsilyl)­pent-4-yn-1-yl groups and a comonomer functionalized with azidomethyl groups, producing the novel fullerene polymers P1-<i>C</i>₆₀ and P2-<i>C</i>₆₀. Despite their extremely high fullerene loading levels, the polymers were soluble in common organic solvents and exhibited no aggregation of fullerene units in films. Moreover, devices containing these fullerene polymers were easily fabricated with common coating processes that exhibit excellent unipolar and bipolar flash memory characteristics as well as unipolar permanent memory characteristics, with high ON/OFF current ratios, long retention times, and low power consumption. These electrical switching behaviors were favorably operated by electron injection. Overall, these devices are the first n-type bipolar and unipolar digital polymer memory devices which can be operated in flash and write-once-read-many-times modes

Structural Characteristics of Amphiphilic Cyclic and Linear Block Copolymer Micelles in Aqueous Solutions

The structural characteristics of aqueous micelles composed of amphiphilic cyclic poly­(<i>n</i>-butyl acrylate-<i>b</i>-ethylene oxide) (cyclic PBA-<i>b</i>-PEO) or a linear analogue (i.e., linear poly­(<i>n</i>-butyl acrylate-<i>b</i>-ethylene oxide-<i>b</i>-<i>n</i>-butyl acrylate) (linear PBA-<i>b</i>-PEO-<i>b</i>-PBA)) were examined for the first time using synchrotron X-ray scattering techniques and quantitative data analysis. The scattering data were analyzed using a variety of methodologies in a comprehensive complementary manner. These analyses provided details of the structural information about the micelles. Both micelles were found to consist of a core and a fuzzy shell; however, the cyclic block copolymer had a strong tendency to form micelles with core and shell parts that were more compact and dense than the corresponding parts of the linear block copolymer micelles. The PBA block of the cyclic copolymer was found to form a hydrophobic core with a density that exceeded the density of the homopolymer in the bulk state. The structural differences originated primarily from the topological difference between the cyclic and linear block copolymers. The elimination of the chain end groups (which introduced entropy and increased the excess excluded volume) from the amphiphilic block copolymer yielded more stable dense micelles in solution

Complex Self-Assembled Morphologies of Thin Films of an Asymmetric A₃B₃C₃ Star Polymer

An asymmetric nine-arm star polymer, (polystyrene)₃-(poly­(4-methoxystyrene))₃-(polyisoprene)₃ (PS₃-PMOS₃-PI₃) was synthesized, and the details of the structures of its thin films were successfully investigated for the first time by using in situ grazing incidence X-ray scattering (GIXS) with a synchrotron radiation source. Our quantitative GIXS analysis showed that thin films of the star polymer molecules have very complex but highly ordered and preferentially in-plane oriented hexagonal (HEX) structures consisting of truncated PS cylinders and PMOS triangular prisms in a PI matrix. This HEX structure undergoes a partial rotational transformation process at temperatures above 190 °C that produces a 30°-rotated HEX structure; this structural isomer forms with a volume fraction of 23% during heating up to 220 °C and persists during subsequent cooling. These interesting and complex self-assembled nanostructures are discussed in terms of phase separation, arm number, volume ratio, and confinement effects

Self-Assembly Characteristics of a Crystalline–Amorphous Diblock Copolymer in Nanoscale Thin Films

A diblock copolymer of crystalline polyethylene (PE) and amorphous poly­(methyl methacrylate) (PMMA), PE₆₉-<i>b</i>-PMMA₉₂, was synthesized; this polymer is thermally stable up to 270 °C. The morphological structures of thermally annealed nanoscale thin films of the copolymer were investigated in detail at various temperatures by using in-situ grazing incidence X-ray scattering (GIXS) with a synchrotron radiation source. Quantitative GIXS analysis found that the PE and PMMA blocks undergo phase separation to produce a vertically oriented hexagonal PE cylinder structure in the PMMA matrix that is very stable up to around 100 °C (which is the onset temperature of PE crystal melting and PMMA glass transition); over the range 100–200 °C, slight variations with temperature in the cylinders’ dimensions and orientation were observed. Furthermore, the PE block chains of the cylinder phase crystallize and undergo crystal growth along the cylinders’ long axes; however, these lamellar crystals do not stack properly because of the limited space along the cylinders’ short axes. As a result, the overall crystallinity is very low. The crystallization of the PE block chains in the diblock copolymer thin film is severely restricted in the diblock architecture by the confinement effects of the limited cylinder space and the anchoring of one end of the PE chain to the cylindrical wall interface. Surprisingly, however, in a nanoscale thin film the PE homopolymer forms a highly ordered lamellar structure; the lamellae are well stacked along the out-of-plane of the film, even though the crystallization is confined by the air and substrate interfaces. This well-ordered and oriented lamellar structural morphology does not arise in melt-crystallized PE bulk specimens

Complex Thin Film Morphologies of Poly(<i>n</i>‑hexyl isocyanate)(5k,10k)–Poly(ε-caprolactone)_1–3(10k,17k) Miktoarm Star Polymers

Two series of crystalline–crystalline miktoarm star polymers were prepared and their thin film morphologies were investigated in detail by synchrotron grazing incidence X-ray scattering (GIXS): poly­(<i>n</i>-hexyl isocyanate)(5000)–poly­(ε-caprolactone)_1–3(17000) (PHIC­(5k)–PCL_1–3(17k)) and poly­(<i>n</i>-hexyl isocyanate)(10000)–poly­(ε-caprolactone)_1–3(10000) (PHIC­(10k)–PCL_1–3(10k)). In addition, their thermal properties were examined. All miktoarm star polymers revealed a two-step thermal degradation behavior where the PHIC arm was degraded first, followed by the PCL arm underwent degradation. Interestingly, all miktoarms were found to show a highly enhanced thermal stability, regardless of their molecular weight over 3k to 17k, which might be attributed to their one-end group capped with the counterpart arm(s) via arm-joint formation. Surprisingly, all miktoarm star polymers always developed only lamellar structure in toluene- and chloroform-annealed films via phase-separation, regardless of the length of PHIC arm as well as the length and number of PCL arm. Despite having highly imbalanced volume fractions, lamellar structure was constructed in the films of miktoarm star polymers through the override of volume fraction rule based on the rigid chain properties, self-assembling characteristics, conformational asymmetry, and compressibilities of PHIC and PCL arms. Furthermore, the orientation of such lamellar structures was controlled by the selection of either toluene or chloroform in the solvent-annealing process. The PHIC arm phases in the lamellar structures favorably formed a mixture of edge-on and face-on structures with fully extended backbone and bristle conformations even under the confined lamellar geometry and arm-joint. The PCL arm phases still crystallized, forming fringed-micelle like structures in which orthorhombic crystals were laterally grown along the in-plane direction of lamellae although their crystallization was somewhat suppressed by the confined lamellar geometry and arm-joint. Overall, crystalline–crystalline PHIC–PCL_1–3 miktoarm polymers demonstrated very interesting but unusual, very complex hierarchical structures in the solvent-annealed thin films