The formation of integral asymmetric membranes from ABC triblock terpolymers by non‐solvent‐induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐b‐P2VP‐b‐PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post‐functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements.
Summary: Binary symmetric diblock copolymer blends, that is, low‐molecular‐weight poly(styrene‐block‐methyl methacrylate) (PS‐b‐PMMA) and high‐molecular‐weight poly(styrene‐block‐methacrylate) (PS‐b‐PMA), self‐assemble on silicon substrates to form structures with highly ordered nanoholes in thin films. As a result of the chemically similar structure of the PMA and the PMMA block, the PMMA chain penetrates through the large PMA block that absorbs preferentially on the polar silicon substrate. This results in the formation of nanoholes in the PS continuous matrix.
An atomic force microscopy image of the thin film obtained from the blend of low‐molecular‐weight PS‐b‐PMMA and high‐molecular‐weight PS‐b‐PMA. The regular array of nanoholes in the films surface is clearly visible. 相似文献
This paper describes a new approach towards preparing self‐assembled hydrogen‐bonded complexes that have vesicle and patched spherical structures from two species of block copolymer in non‐selective solvents. The assembly of vesicles from the intermolecular complex formed after mixing polystyrene‐block‐poly(4‐vinyl phenol) (PS‐b‐PVPh) with poly(methyl methacrylate)‐block‐poly(4‐vinylpyridine) (PMMA‐b‐P4VP) in tetrahydrofuran (THF) is driven by strong hydrogen bonding between the complementary binding sites on the PVPh and P4VP blocks. In contrast, well‐defined patched spherical micelles form after blending PS‐b‐PVPh with PMMA‐b‐P4VP in N,N‐dimethylformamide (DMF): weaker hydrogen bonds form between the PVPh and P4VP blocks in DMF, relative to those in THF, which results in the formation of spherical micelles that have compartmentalized coronas that consist of PS and PMMA blocks.
A branched copolymer containing a degradable polyperoxide linkage at a branching point was synthesized by the radical copolymerization of dienyl‐functionalized polystyrene and polyisoprene macromonomers with molecular oxygen. The ternary mixture of the branched copolymer and the macromonomers showed phase‐separated structure after annealing at 45 and 90 °C. The adjacent spacing of the phase‐separated structure was in the order of submicron to micrometer, which is larger than that of general microphase separated structures, due to the presence of homopolymers (macromonomers). Annealing at 110 °C induced thermal decomposition of the polyperoxide followed by in‐situ collapse and a drastic morphology change in the phase‐separated structure.
Two well‐defined diblock copolymers with quadruple hydrogen‐bonding groups on one block, denoted PSUEA‐1 and PSUEA‐2 , have been synthesized, and novel snowflake‐shaped nanometer‐scale aggregates, self‐assembled by such diblock copolymers in non‐polar solvents, have been observed. The micellar dimensions were investigated by DLLS and SLLS. Their morphologies were studied by TEM. Since the degrees of polymerization of the Upy‐containing blocks of PSUEA‐1 and PSUEA‐2 are quite similar and the polystyrene block of the PSUEA‐1 is longer than that of the PSUEA‐2 , a subtle but identifiable difference between the sizes and structures of the PSUEA‐1 and PSUEA‐2 aggregates was noticed and characterized.
A simple and effective airflow method to prepare sandwich‐type block copolymer films is reported. The films are composed of three layers: vertically oriented nanocylinders align in both upper and bottom layers and irregular nanocylinders exist in the bulk of the film. The vertically oriented nanocylinders in both sides can provide high accessibility to ions and ensures the exchange of chemical species between the membrane and external environment, while the irregularly oriented nanocylinders in the middle part of the film can prolong the pathway of ions transportation and enhance ions selectivity.
Summary: Here, we have described a novel supramolecular complex (SMC) between poly(styrene)-b-poly(4-vinylpyridine) (PS-b-P4VP) and 1-pyrenebutyric acid (PBA) and studied of its self assembly in thin film. PBA will make supramolecular complex with the P4VP block due to strong hydrogen bonding between the carboxylic group of 1-pyrenebutyric acid and pyridine ring of P4VP. The formation of supramolecular complex between PS-P4VP and PBA through hydrogen bonding is investigated through FTIR study. The supramolecular complex of PS-b-P4VP and 1-pyrenebutyric acid changed the block copolymer morphology from cylindrical to lamella in thin film due to the increase of the volume fraction of P4VP (PBA). In both cases (parent block copolymer and SMC), the microdomains are oriented normal to the substrate after annealing in a selective solvent. Pure block copolymer shows cylindrical morphology with a periodicity of ∼26 nm, whereas the SMC shows lamellar morphology with a periodicity of ∼ 29 nm. After fabricating the thin film from SMC, 1-pyrenebutyric acid can be easily removed by dissolving the thin film in ethanol to transform the block copolymer thin film into nanotemplate or membrane. 相似文献
This paper describes the miscibility and self‐assembly, mediated by hydrogen‐bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(ε‐caprolactone)‐block‐(4‐vinyl pyridine)] (PCL‐b‐P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen‐bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP‐POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long‐range order, such as cylindrical and spherical structures, at relatively low OP‐POSS contents, and short‐range order or disordered structures at higher OP‐POSS contents. Analyses performed using differential scanning calorimetry, wide‐angle X‐ray diffraction, and FT‐IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen‐bond acceptors toward the OH group of OP‐POSS than are the CO groups of the PCL block, thereby resulting in excluded and confined PCL phases.
While network‐like assemblies are formed by amphiphilic polyphosphazenes with poly(N‐isopropylacrylamide) and ethyl tryptophan as side groups in aqueous solution, a significant morphology transformation is observed when small molecules that exhibit hydrogen‐bonding interactions with amphiphilic copolymers are introduced during the preparation of polymeric assemblies through a dialysis procedure. Depending on copolymer composition and the content of small molecules introduced, aggregates ranging from general vesicles, high‐genus vesicles, to well‐defined nanospheres can be prepared successfully as clearly evidenced by TEM observation, which suggests this procedure should be a novel approach to prepare composite vesicles.
