Asymmetric Solvent-Annealed Triblock Terpolymer Thick Films Topped by a Hexagonal Perforated Lamellar Nanostructure.

Asymmetric and nanostructured polystyrene-block-poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO or SVEO, S:V:EO ≈ 56:34:10, 79.5 kg mol-1 ) thick films blended with 20 wt% of a short PS homopolymer (hPS, 10.5 kg mol-1 ) are achieved by combining the non-solvent induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment. Here, the NIPS step allows for the formation of a highly-permeable sponge-like substructure topped by a dense thin layer exhibiting poorly-ordered nanopores while the subsequent SVA treatment enables to reconstruct the material top surface into a porous monolayer of well-ordered hexagonal perforated lamellae (HPL). This optimized film architecture generated by NIPS-SVA shows a water permeability of 860 L h-1 m-2 bar-1 , which is roughly two times higher than the flux measured through NIPS made PS-b-P2VP-b-PEO/hPS materials having poorly-ordered nanopores. The post-SVA treatment is also revealed as a powerful tool to tailor the thickness of the nanostructure formed within the blended material because monoliths entirely composed of a HPL phase are produced by increasing the time of exposure to a chloroform stream. The water flux of such PS-b-P2VP-b-PEO/hPS monoliths is found to be an order of magnitude lower than that of their asymmetric film homologues.

Nanoscale Archimedean Tilings Formed by 3-Miktoarm Star Terpolymer Thin Films.

3-Miktoarm star terpolymer architecture (3µ-ABC), consisting of three dissimilar polymer chains, A, B, and C connected at a junction point, provides a unique opportunity in the design of complex nanoscale patterns such as Archimedean tilings that are not accessible from linear ABC terpolymers. In this work, the synthesis and the self-assembly of 3-miktoarm star terpolymers, namely, polystyrene-arm-poly(2-vinylpyridine)-arm-polyisoprene (3µ-SPI) into Archimedean tiling patterns is described. Several 3µ-SPI terpolymers are produced via a mid-functional PS-b-P2VP, synthesized by sequential anionic polymerization, using a 1,1-diphenylethylene bearing a tert-butyldimethylsilyl-protected hydroxyl functionality as a core molecule. PI arms with different sizes are then linked to the deprotected hydroxyl function of the core molecule via a Steglich esterification. Solvent-annealed 3µ-SPI thin films exhibit nanoscale prisms arranged into a (4.6.12) Archimedean tiling pattern. Depending on the size of the low etch-resistant PI arm and the solvent selected to promote the self-assembly of 3µ-SPI thin films, the voided columns occupy the square or decagonal sites of the (4.6.12) pattern. The use of this (4.6.12) tiling produced for the first time from self-assembled 3µ-ABC thin films can be a promising route to build 2D photonic crystals having complete photonic band gaps, where the light propagation is completely prohibited.

Metallic Nanodot Patterns with Unique Symmetries Templated from ABC Triblock Terpolymer Networks.

Nanotemplates derived from the self-assembly of AB-type block copolymers provide an elegant route to achieve well-defined metallic dot arrays, even if the variety of pattern symmetries is restricted due to the limited number of structures offered by microphase separated diblock copolymers. A strategy that relies on the use of complex network structures accessible through the self-assembly of linear ABC-type terpolymers is presented for the formation of metallic nanodots arrays with "outside-the-box" symmetries. Patterned templates formed by the cubic Q214 and orthorhombic O70 network structures are used as excellent platforms to build well-ordered gold nanodot arrays with unique p3m1 and p2 symmetries, respectively. A simple yet efficient blending strategy is used to tune the critical dimensions of the p3m1 pattern while laterally ordered gold nanodot arrays are also demonstrated through a directed self-assembly approach. Such highly ordered gold nanodots with tunable particle dimensions and array periods, enabling the control of their plasmonic responses, are attractive probes for biological imaging.

Core-Shell Double Gyroid Structure Formed by Linear ABC Terpolymer Thin Films.

The synthesis and self-assembly in thin-film configuration of linear ABC triblock terpolymer chains consisting of polystyrene (PS), poly(2-vinylpyridine) (P2VP), and polyisoprene (PI) are described. For that purpose, a hydroxyl-terminated PS-b-P2VP (45 kg mol-1 ) building block and a carboxyl-terminated PI (9 kg mol-1 ) are first separately prepared by anionic polymerization, and then are coupled via a Steglich esterification reaction. This quantitative and metal-free catalyst synthesis route reveals to be very interesting since functionalization and purification steps are straightforward, and well-defined terpolymers are produced. A solvent vapor annealing (SVA) process is used to promote the self-assembly of frustrated PS-b-P2VP-b-PI chains into a thin-film core-shell double gyroid (Q230 , space group: Ia3¯d) structure. As terraces are formed within PS-b-P2VP-b-PI thin films during the SVA process under a CHCl3 vapor, different plane orientations of the Q230 structure ((211), (110), (111), and (100)) are observed at the polymer-air interface depending on the film thickness.

Highly Ordered Nanoring Arrays Formed by Templated Si-Containing Triblock Terpolymer Thin Films.

Laterally ordered nanorings with a periodicity of 38 nm are produced from the directed self-assembly of poly(1,1-dimethylsilacyclobutane)-block-polystyrene-block-poly(methyl methacrylate) thin films on topographically patterned substrates. Such nanoscale arrays with vertically oriented rings are highly desired in technological applications including memory using magnetic recording, metamaterial, waveguide, etc.

Templated Sub-100-nm-Thick Double-Gyroid Structure from Si-Containing Block Copolymer Thin Films.

The directed self-assembly of diblock copolymer chains (poly(1,1-dimethyl silacyclobutane)-block-polystyrene, PDMSB-b-PS) into a thin film double gyroid structure is described. A decrease of the kinetics of a typical double-wave pattern formation is reported within the 3D-nanostructure when the film thickness on mesas is lower than the gyroid unit cell. However, optimization of the solvent-vapor annealing process results in very large grains (over 10 µm²) with specific orientation (i.e., parallel to the air substrate) and direction (i.e., along the groove direction) of the characteristic (211) plane, demonstrated by templating sub-100-nm-thick PDMSB-b-PS films.

Anisotropic Lithium Ion Conductivity in Single-Ion Diblock Copolymer Electrolyte Thin Films.

Well-defined single-ion diblock copolymers consisting of a Li-ion conductive poly(styrenesulfonyllithium(trifluoromethylsulfonyl)imide) (PSLiTFSI) block associated with a glassy polystyrene (PS) block have been synthesized via reversible addition fragmentation chain transfer polymerization. Conductivity anisotropy ratio up to 1000 has been achieved from PS-b-PSLiTFSI thin films by comparing Li-ion conductivities of out-of-plane (aligned) and in-plane (antialigned) cylinder morphologies at 40 °C. Blending of PS-b-PSLiTFSI thin films with poly(ethylene oxide) homopolymer (hPEO) enables a substantial improvement of Li-ion transport within aligned cylindrical domains, since hPEO, preferentially located in PSLiTFSI domains, is an excellent lithium-solvating material. Results are also compared with unblended and blended PSLiTFSI homopolymer (hPSLiTFSI) homologues, which reveals that ionic conductivity is improved when thin films are nanostructured.

Laterally Ordered Sub-10 nm Features Obtained From Directed Self-Assembly of Si-Containing Block Copolymer Thin Films.

Laterally ordered sub-10 nm features are produced from the directed self-assembly of poly(1,1-dimethyl silacyclo-butane)-block-poly(methyl methacrylate) (PDMSB-b-PMMA) thin films on sinusoidal azobenzene-containing patterns. The use of sinusoidal surface relief grating enables the formation of very large grain areas (over several µm(2) ) consisting of out-of-plane PMMA cylinders.

Optimization of Magnetic Inks Made of L1(0)-Ordered FePt Nanoparticles and Polystyrene-block-Poly(ethylene oxide) Copolymers.

The preparation of magnetic inks stable over time made of L10-ordered FePt nanoparticles, thiol-ended poly(ethylene glycol) methyl ether (mPEO-SH) compatibilizing macromolecules and asymmetric polystyrene-block-poly(ethylene oxide) copolymers (BCP) as a subsequent self-organizing medium was optimized. It was demonstrated that the use of sacrificial MgO shells as physical barriers during the annealing stage for getting the L10-ordered state makes easier and more efficient the anchoring of compatibilizing PEO macromolecules onto the nanoparticles surface. L10-FePt grafted nanoparticles have shown a good colloidal stability and affinity with the PEO domains of the BCP leading to L10-FePt/BCP composite thin layers with individual magnetic dots dispersed in the BCP matrix.

Precision synthesis of poly(ionic liquid)-based block copolymers by cobalt-mediated radical polymerization and preliminary study of their self-assembling properties.

A poly(ionic liquid)-based block copolymer (PIL BCP), namely, poly(vinyl acetate)-b-poly(N-vinyl-3-butylimidazolium bromide), PVAc-b-PVBuImBr, is synthesized by sequential cobalt-mediated radical polymerization (CMRP). A PVAc precursor is first prepared at 30 °C in bulk by CMRP of VAc, using bis(acetylacetonato)cobalt(II), Co(acac)2, and a radical source (V-70). Growth of PVBuImBr from PVAc-Co(acac)2 is accomplished by CMRP in DMF/MeOH (2:1, v/v). This PIL BCP self-assembles in the sub-micron size range into aggregated core-shell micelles in THF, whereas polymeric vesicles are observed in water, as evidenced by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Thin-solid sample cut from raw materials analyzed by TEM shows an ordered lamellar organization by temperature-dependent synchrotron small-angle X-ray scattering (SAXS). Anion exchange can be accomplished to achieve the corresponding PIL BCP with bis(trifluorosulfonyl)imide (Tf2 N(-)) anions, which also gives rise to an ordered lamellar phase in bulk samples. A complete suppression of SAXS second-order reflection suggests that this compound has a symmetric volume fraction (f ≈ 0.5). SAXS characterization of both di- and triblock PIL BCP analogues previously reported also shows a lamellar phase of very similar behavior, with only an increase of the period by about 8% at 60 °C.

Ordered nanoscale Archimedean tilings of a templated 3-miktoarm star terpolymer.

The directed self-assembly of 3-miktoarm star terpolymer chains (polyisoprene-arm-polystyrene-arm-polyferrocenylethylmethylsilane (3 µ-ISF)) into 2D Archimedean tilings is described. A morphological change from (4.8(2)) to (6(3)) tiling is reported in the 3 µ-ISF thin film blended with PS homopolymer when a greater swelling of PI is achieved during the solvent annealing process. Highly oriented (4.8(2)) tilings were produced by templating the self-assembled three colored structures in blended thin films. The use of (4.8(2)) and (6(3)) tilings as nanolithographic masks to transfer square and triangular hole arrays into the substrate is also demonstrated.

Square and rectangular symmetry tiles from bulk and thin film 3-miktoarm star terpolymers.

The directed self assembly of a 3-miktoarm star terpolymer (polyisoprene-arm-polystyrene-arm-polyferrocenylethylmethylsilane (3µ-ISF)) into a (4.8²) square symmetry Archimedean tiling pattern is described. Bulk samples of 3µ-ISF generate equilibrium columnar (4.8²) tile patterns (symmetry p 4 mm) on annealing, which is preceded by a metastable c 2 mm centered rectangular structure. In contrast, in thin films of 3µ-ISF blended with PS homopolymer, the c 2 mm phase is stable with columns oriented out of plane when the film thickness is below 50 nm. However, the 3µ-ISF/homopolymer blend rapidly forms a p 4 mm symmetry when the film thickness is ∼80 nm, with grain sizes of several µm and excellent order. Defects in the p 4 mm structure are described.

A facile approach to modify cellulose nanocrystal for the adsorption of perfluorooctanoic acid.

Cellulose-based materials are a sustainable alternative to polymers derived from petroleum. Cellulose nanocrystal (CNC) is a biopolymer belonging to this family; it is commonly known for its important physical and chemical properties and ability to form a film. Modifying CNC via electrostatic interaction provided by cationic polymers is a facile and promising technique to enlarge the application of CNC. Herein, we report the preparation of films, from blends of negatively charged CNC and positively charged poly (trimethyl aminoethyl methacrylate) (PTMAEMA). The interaction between CNC and PTMAEMA was verified by using a quartz crystal microbalance with dissipation monitoring (QCM-D), as well as by measuring the particle size and ζ-potential of the casting mixture. To favor the application of the nanocomposite film in water treatment, the film was supported on Whatman™ paper, and adsorption tests were conducted using perfluorooctanoic acid (PFOA) as a model compound for the family of persistent fluorinated pollutants known as PFAS (per- and polyfluoroalkyl substances).

Nano-organization of amylose-b-polystyrene block copolymer films doped with bipyridine.

This paper discusses the self-assembly of rod-coil amylose-b-polystyrene (Mal-b-PS) block copolymer thick and thin films. The nano-organization falls in an interdomain spacing d of about 10 nm, much smaller than flexible-flexible petrol block copolymer systems. Additionally, hydrogen-bonding interactions between carbohydrate rods (amylose) and 4',4-bipyridine (bipy) molecules induces phase transitions. Indeed, adding bipy in maltooctadecaose-block-polystyrene (Mal18-b-PS) copolymers results, at room temperature, in the formation of a lamellar phase having Mal18 bipy-rich nanodomains instead of hexagonal close-packed (HCP) of cylinders made of Mal18, whereas a coexistence of Mal7bipy-rich cylindrical and spherical nanodomains are formed from maltoheptaose-b-polystyrene (Mal7-b-PS) copolymers instead of a poorly organized array of Mal7-based cylinders. On heating, the Mal7bipy-b-PS system shows more rich phase behavior as compared to the Mal7-b-PS one due to weakening of hydrogen bonding with temperature. Such a system is of great interest in developing active layers in light-emitting diodes (LEDs) or in photovoltaic cells to realize devices with an optimal structure, that is, having large interface area and domain size with similar exciton diffusion length (10 nm).

Hexagonal-to-cubic phase transformation in composite thin films induced by FePt nanoparticles located at PS/PEO interfaces.

The organization process of asymmetric poly(styrene-block-ethylene oxide) (PS-b-PEO) copolymer thin films blended with FePt nanoparticles is studied. In a first step, it is shown that FePt nanoparticles stabilized by oleic acid ligands are distributed within the PS matrix phase, whereas the same particles partially covered with short dopamine-terminated-methoxy poly(ethylene oxide) (mPEO-Dopa) are located at PS/PEO interfaces. The swelling of PS domains, induced by FePt_oleic acid nanoparticles during the solvent annealing process, results in formation of a disordered microstructure in comparison to the well-organized hexagonally close-packed (HCP) cylinder phase formed in the neat PS-b-PEO copolymer. The evolution of the microstructure of PS-b-PEO/FePt_mPEO-Dopa composite has been investigated for different solvent annealing treatments. Under high-humidity conditions during the vapor annealing process, the addition of FePt nanoparticles results in formation of spheres in the film split into terraces. The upper and lower terraces are occupied by spheres organized in an unusual square and HCP phases, respectively. Under low-humidity conditions, undulated PEO cylinders oriented parallel to substrate are formed in the presence of FePt nanoparticles. In this case, we observe that most of the nanoparticles accumulate within the core of topological defects, which induces a low nanoparticle concentration at the PS/PEO interfaces and so stabilizes an intermediate undulated cylinder phase.

Fluorescent vesicles consisting of galactose-based amphiphilic copolymers with a π-conjugated sequence self-assembled in water.

Fluorescent vesicles considered as a mimic of natural primitive cells are prepared from poly(3-hexylthiophene)-block-poly(3-O-methacryloyl-D-galactopyranose) P3HT-b-PMAGP copolymers. The unique characteristic of such vesicular nanostructures is their architecture, which comprises a hydrophobic π-conjugated P3HT wall stabilized by a hydrophilic PMAGP interface featuring glucose units. The results of this work offer a very efficient and straightforward method for engineering well-controlled fluorescent nanoparticles (without the addition of dyes), which provide an excellent support to the study of carbohydrate-protein interactions.

Block copolymer systems: from single chain to self-assembled nanostructures.

Recent advances in the field of macromolecular engineering applied to the fabrication of nanostructured materials using block copolymer chains as elementary building blocks are described in this feature article. By highlighting some of our work in the area and accounting for the contribution of other groups, we discuss the relationship between the physical-chemical properties of copolymer chains and the characteristics of nano-objects originating from their self-assembly in solution and in bulk, with emphasis on convenient strategies that allow for the control of composition, functionality, and topology at different levels of sophistication. In the case of micellar nanoparticles in solution, in particular, we present approaches leading to morphology selection via macromolecular architectural design, the functionalization of external solvent-philic shells with biomolecules (polysaccharides and proteins), and the maximization of micelle loading capacity by the suitable choice of solvent-phobic polymer segments. The fabrication of nanomaterials mediated by thin block copolymer films is also discussed. In this case, we emphasize the development of novel polymer chain manipulation strategies that ultimately allow for the preparation of precisely positioned nanodomains with a reduced number of defects via block-selective chemical reactivity. The challenges facing the soft matter community, the urgent demand to convert huge public and private investments into consumer products, and future possible directions in the field are also considered herein.

Thermoresponsive vesicular morphologies obtained by self-assemblies of hybrid oligosaccharide-block-poly(N-isopropylacrylamide) copolymer systems.

This work discusses the self-assembly properties of thermoresponsive hybrid oligosaccharide-block-poly(N-isopropylacrylamide) copolymer systems: maltoheptaose-block-poly(N-isopropylacrylamide) (Mal(7)-b-PNIPAM(n)) copolymers. Those systems at different molar masses and volume fractions were synthesized using Cu(I)-catalyzed 1,3-dipolar azide/alkyne cycloaddition, so-called "click" chemistry, between an alkynyl-functionalized maltoheptaose (1) and poly(N-isopropylacrylamide) having a terminal azido group (N(3)-PNIPAM(n)) prepared by atom transfer radical polymerization (ATRP). While the cloud point (T(cp)) of the N(3)-PNIPAM(n) ranged from 36.4 to 51.5 degrees C depending on the degree of polymerization, those obtained of the diblock copolymers ranged from 39.4 to 73.9 degrees C. The self-assembly of such systems is favored due to the hydrophobicity of the PNIPAM in water above the T(cp). While the N(3)-PNIPAM(n) present polydisperse globular shape with a mean diameter of 500 nm, well-defined vesicular morphologies with an approximate diameter of 300 nm are obtained in diblock copolymer systems. These results were obtained and confirmed using static and dynamic light scattering as well as imaging techniques such as transmission electron microscope experiments.

Self-assembling study of a cylinder-forming block copolymer via a nucleation-growth mechanism.

Block copolymer materials form self-assembling structures at a nanometric scale, of interest in nanotechnology. The organization process of asymmetric poly(styrene-block-methyl methacrylate) (PS-b-PMMA) copolymer thin films is studied. In a first step it is demonstrated that two consecutive mechanisms lead to the formation of a well-ordered phase. The first mechanism is the local segregation of blocks, which leads to a metastable disordered cylinder phase (C(d)). The second mechanism is a transformation of the C(d) phase to a vertical cylinder phase via a nucleation-growth mechanism. The influence of film thickness and surface tension on the organization is also studied. Above the natural cylinder monolayer height, h(1), the kinetics of the cylinder organization strongly depends on the initial film thickness, and below h(1) the film splits into terraces. By varying the interactions between the substrate surface and the different blocks, a disordered phase can be formed instead of terraces.

Periodic Bicontinuous Structures Formed on the Top Surface of Asymmetric Triblock Terpolymer Thick Films.

The combination of the nonsolvent-induced phase separation (NIPS) process with a solvent vapor annealing (SVA) treatment is used to produce asymmetric and hydrophobic thick films having different long-range ordered network nanostructures, which are inaccessible via currently available membrane fabrication methods. We show that the disordered phase generated by NIPS on the material top surface can be transformed into a highly ordered bicontinuous network nanostructure during the SVA process without disrupting the substructure morphology. For instance, by using a straightforward blending approach, either a triply periodic alternating diamond (DA) structure or a core-shell perforated lamellar (PL) phase was demonstrated on the skin layer of fully hydrophobic poly(1,1-dimethyl silacyclobutane)-block-polystyrene-block-poly(methyl methacrylate) (PDMSB-b-PS-b-PMMA) thick films. Such a material fabrication method, enabling the formation of a sponge-like substructure topped by a network phase having an excellent long-range order, provides an appealing strategy to facilitate the manufacture of next-generation membranes at large scale since these bicontinuous morphologies obviate the need of the nanochannel alignment.