Microphase Separation In Bulk Research Articles

Polymerization-Induced Microphase Separation with Long-Range Order in Melts of Gradient Copolymers.

In this work, we studied the question of whether it is possible to develop a one-step approach for the creation of microphase-separated materials with long-range order with the help of spontaneous gradient copolymers, i.e., formed during controlled copolymerization solely due to the large difference in the reactivity ratios. To that end, we studied the polymerization-induced microphase separation in bulk on the example of a monomer pair with realistic parameters based on styrene (S) and vinylpirrolydone (VP) by means of computer simulation. We showed that for experimentally reasonable chain lengths, the structures with long-range order start to appear at the conversion degree as low as 76%; a full phase diagram in coordinates (fraction of VP—conversion degree) was constructed. Rather rich phase behavior was obtained; moreover, at some VP fractions, order–order transitions were observed. Finally, we studied how the conversion degree at which the order–disorder transition occurs changes upon varying the maximum average chain length in the system.

One-Step Approach to Polyester-Polyether Block Copolymers Using Highly Tunable Bicomponent Catalyst.

Phthalic anhydride and propylene/ethylene oxide are copolymerized at room temperature by a bicomponent metal-free catalyst comprising a mild phosphazene base and triethylborane. Provided with proper loadings of the two catalytic components, block copolymers with strict (AB)nBm type sequence structures and controlled molar mass (up to 60 kg mol-1) can be generated in one synthetic step, and the block architecture can be enriched by the use of mono-, di-, or tetrahydroxy initiators. The obtained polyester-polyether block copolymers readily undergo microphase-separation in bulk and nanoaggregation in selective (aqueous and alcoholic) solvents.

Self‐Assembly of Multiblock Copolymers

AbstractBlock copolymers (BCPs) are a subclass of soft matter extensively used in materials science and nanomedicine. They consist of two or more incompatible segments and are prone to self‐assemble into nanostructures with a characteristic size of 10–100 nm. BCPs thus naturally address the structural dimension between molecular and colloidal scales. This review gives a brief overview of recent developments in BCP self‐assembly under various conditions. Special emphasis is put on linear BCPs with three or more sequentially linked blocks, i. e. ABC triblock terpolymers, ABAC tetrablock terpolymers, and so on. We discuss their microphase separation in bulk, in the confinement of nanoemulsion droplets, and their hierarchical self‐assembly to multicompartment nanostructures in selective solvents. Regarding applications, block copolymers are widely used in templating and drug delivery, but their inherent asymmetry is also particularly useful for the synthesis of Janus nanoparticles.

Controlling morphology of polymer photoactive layer in photovoltaic elements: mesoscopic simulation

A concept of fabrication of well-organized conductive pathways in CP/NP blends in photovoltaic devices. It is assumed that to succeed in this task, one can use the property of AB diblock copolymers that, depending on the chemical structure of A and B blocks and the ratio between their lengths, these copolymers undergo microphase separation in bulk to form thermodynamically stable domains of cubic symmetry with 3D periodicity. Using a mesoscale simulation technique, we demonstrated that the morphology of the photoactive layer of photovoltaic devices can be controlled by selecting the surface NP modifier (responsible for the compatibility of NPs with the polymeric matrix), the chemical structure of the blocks of a conjugated copolymer, and their length.

Synthesis and antifouling activities of fluorinated polyurethanes

AbstractA series of fluorinated polyurethanes (FPUs) with various contents of fluorinated chain extender (EF) and the same amount of poly(oxytetramethylene glycol) and diphenylmethanediisocyanate were synthesized to explore the relationship between the surface physicochemical properties and bulk microphase separation structures of these FPUs and their antifouling activities against model bacteria and platelets. The bulk microphase separation of FPUs increased with the amount of incorporated EF. It was found that the surfaces of all FPUs were saturated by a layer of fluorocarbon chains which resulted in similar chemical composition and wetting activities for the three kinds of FPUs. The FPUs with lower or similar microphase separation compared with non‐fluorinated polyurethane chain‐extended with 1,4‐butanediol showed similar or even increased adhesion of bacteria and platelets. Notably, FPU with a higher degree of microphase separation than non‐fluorinated polyurethane displayed excellent antifouling activities against both model bacteria and blood platelets. It is therefore concluded that the increased microphase separation of the FPUs results in enhanced antifouling properties. © 2019 Society of Chemical Industry

Synthesis and self-assembly of high molecular weight polystyrene-block-poly[2-(N-morpholino)ethyl methacrylate]: A story about microphase separation, amphiphilicity, and stimuli-responsivity

The synthesis of polystyrene-block-poly[2-(N-morpholino)ethyl methacrylate] (PS-b-PMEMA) as a new highly amphiphilic and multiple stimuli-responsive block copolymer is presented. To achieve high molecular weights far beyond 100 kDa in a highly controlled manner (dispersities < 1.1), a synthetic route via sequential combination of anionic polymerization for the PS block and reversible addition–fragmentation chain transfer (RAFT) polymerization for the PMEMA block is used. The synthesized block copolymers are investigated regarding their microphase separation in bulk, which delivers well-ordered self-assembled bulk structures as evidenced by small-angle x-ray scattering (SAXS) and atomic force microscopy (AFM). In aqueous solution, the block copolymer self-assembles into narrowly size distributed micelles with a PMEMA corona. The stimuli-triggered micelle response towards temperature, pH, and kosmotropic as well as chaotropic salts is shown via various dynamic light scattering (DLS) experiments. Furthermore, a dependency of aggregate size on solvent composition in polymer/tetrahydrofuran/water mixtures is described. The reported findings deliver a feasible pathway to high molecular weight block copolymers with tailored chemical properties and show the potential of PS-b-PMEMA as material for mechanically demanding switchable devices.

Synthesis and morphology investigations of a novel alkyne‐functionalized diblock copolymer

AbstractWe reported the synthesis and morphology of a novel alkyne‐functionalized diblock copolymer (di‐BCP) poly(methyl methacrylate‐random‐propargyl methacrylate)‐block‐poly(4‐bromostyrene). The di‐BCPs were synthesized by atom transfer radical polymerization and postpolymerization deprotection, with good control over molecular weight and polydispersity index. Microphase separation in bulk di‐BCPs was confirmed by thermal analysis, small‐angle X‐ray scattering, and transmission electron microscopy. Microphase‐separated morphologies were also observed in thin films, and the orientation of the microdomains can be conveniently controlled by annealing under different solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Functionalization of shaped polymeric nanoobjects via bulk co-self-assembling gelable block copolymers with silane coupling agents

Hairy polymer nanoobjects (PNOs) of different shapes can be easily obtained by cross-linking the discontinuous microphases of bulk block copolymers followed by dispersing in a solvent. Herein we report a general approach to functionalize the shaped PNOs by bulk microphase separation of poly(3-(triethoxysilyl)propyl methacrylate)- block-polystyrene (PTEPM- b-PS) copolymers in the presence of functional silane coupling agents. The silanes like (3-mercaptopropyl)trimethoxysilane and (3-chloropropyl)trimethoxysilane were enriched into the PTEPM discontinuous microdomains selectively. The microphase structures were characterized by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) of microtomed slices. For the PTEPM 78- b-PS 348 which had a lamellar structure, its blending mixtures with MMS and CMS whose content reached up to 50 wt% still remained as a lamellar structure. When small amount of MMS or CMS was added, the PTEPM 71- b-PS 780 as hexagonally packed cylinders remained its structure. However, the morphology changed into lamellae at higher content of the silanes. For PTEPM 46- b-PS 1669, its spherical structure remained but the size distribution became broad gradually with increase of silanes. By inducing gelation and then dispersing in a good solvent of PS phases, hairy PNOs having lamellar, cylindrical or spherical shape with their cores being functionalized with the groups from co-gelated silanes were obtained.

Dispersible Shaped Nanoobjects from Bulk Microphase Separation of HighTgBlock Copolymers without Chemical Cross-linking

This work presents a facile procedure to fabricate the nanoobjects of block copolymers with lamellar, cylindrical, and spherical morphology via bulk microphase separation and dispersing in selective solvents without chemical cross-linking. The morphologies of these nanoobjects in solution were stabilized by their cores in a glassy state. First the bulk microphase separation of a series of poly(tert-butyl acrylate)-block-polystyrene (PtBA-b-PS) block copolymers was conducted to generate the ordered materials with lamellar, cylindrical and spherical morphology with the PS domains as the discontinuous phases as characterized by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Then by direct dispersing these microphase separated materials into methanol that is a selective solvent of the PtBA segments, the nanoobjects, lamellae, cylinders and spheres, inherited from their bulk structures were obtained. As a contrast, micellization of these block copolymers directly in methanol al...

Organic/inorganic nanoobjects with controlled shapes from gelable triblock copolymers

A functional gelable triblock copolymer, poly(2-vinylpyridine)- block-poly(3-(triethoxysilyl)propyl methacrylate)- block-polystyrene (P2VP- b-PTEPM- b-PS), was prepared by the combination of reversible addition-fragmentation chain transfer (RAFT) mediated radical polymerization and copper catalyzed click chemistry. Bulk microphase separation of P2VP 310- b-PTEPM 58- b-PS 322 under different conditions was studied in order to prepare organic/inorganic nanoobjects by a procedure of crosslinking PTEPM phases and dispersing in a solvent. The conditions included using different annealing solvents and adding stearic acids to form supramolecular complexes with P2VP blocks respectively. Then the packed cylinders with P2VP cores and PTEPM shells dispersed in the PS matrix, lamella with alternating PS, PTEPM and P2VP layers, and the inverse cylindrical morphology with PS cores and PTEPM shells dispersed in the matrix of P2VP/stearic acid complex were obtained respectively just from the same triblock copolymer sample. After crosslinking PTEPM microdomains by sol-gel process and dispersing in solvents, a series of organic/inorganic polymeric nanoobjects, including two types of nanofibers with inverse internal structure and one novel kind of nanoplates, were produced. Further modification of the fibers with P2VP cores has been studied.

Organic−Inorganic Hybrid Materials by Self-Gelation of Block Copolymer Assembly and Nanoobjects with Controlled Shapes Thereof

Radical polymerization of a gelable monomer 3-(triethoxysilyl)propyl methacrylate (TEPM) mediated by a chain transfer agent (CTA), cumyl dithiobenzoate (CDB), i.e., reversible addition−fragmentation chain transfer (RAFT) polymerization, has been studied. A series of well-defined PTEPM-block-polystyrene (PTEPM-b-PS) diblock copolymers were synthesized via sequential RAFT polymerization of styrene mediated by the PTEPM macromolecular CTA. Both formations of PTEPM homopolymers and the PTEPM-b-PS diblock copolymers exhibited first-order kinetics, and the molecular weights increased linearly with monomer conversion. The bulk microphase separation behaviors of PTEPM-b-PS diblock copolymers were studied by a combination of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). With change of the block composition, three different morphologies of microphase separation, i.e., lamellae, hexagonally packed cylinders, and spheres, were obtained. Afterward, self-gelation of the PTEPM phases was carried out in-situ to cross-link the PTEPM phase, and novel organic−inorganic hybrid bulk materials with ordered domain structures of three morphologies were obtained. Furthermore, when the gelated materials were dispersed in a good solvent for the PS matrix, the isolated organic−inorganic hybrid nanoobjects with controlled shapes including plates, cylinders, and spheres with PS hairs were prepared from the respective bulk materials. This self-gelation process of block copolymer aggregates in bulk can be universal and may be extended to prepare various ordered hybrid materials and isolated hybrid nanoobjects with tailored shapes and functionality.

Phase Coherence and Microphase Separation Transitions in Diblock Copolymer Thin Films

In thin films of diblock copolymers it was found that microphase separation and the establishment of phase coherence can occur as two distinct events in diblock copolymer thin films, at widely separated temperatures. At temperatures far removed from the bulk microphase separation transition temperature increasing overlap of the decaying concentration profiles from the substrate and air interfaces leads to a sharp onset of phase coherence throughout a thin film and the discretization of the film thickness, despite only weak microphase separation in the center of the film. A further transition to a fully microphase separated state occurs at temperatures close to the microphase separation transition temperature, but this transition becomes broader and less distinct with decreasing film thickness. In thicker films, on the other hand, phase coherence is not established until the ordering transition temperature is reached, due to the first-order nature of the transition and the finite coherence length in the disordered state. In thick films, phase coherence throughout the film is established either simultaneously or after complete microphase separation has occurred.

The greatest fossilist the world ever knew: Mary Anning (1799–1847)

The synthesis of polystyrene-block-poly[2-(N-morpholino)ethyl methacrylate] (PS-b-PMEMA) as a new highly amphiphilic and multiple stimuli-responsive block copolymer is presented. To achieve high molecular weights far beyond 100 kDa in a highly controlled manner (dispersities < 1.1), a synthetic route via sequential combination of anionic polymerization for the PS block and reversible addition–fragmentation chain transfer (RAFT) polymerization for the PMEMA block is used. The synthesized block copolymers are investigated regarding their microphase separation in bulk, which delivers well-ordered self-assembled bulk structures as evidenced by small-angle x-ray scattering (SAXS) and atomic force microscopy (AFM). In aqueous solution, the block copolymer self-assembles into narrowly size distributed micelles with a PMEMA corona. The stimuli-triggered micelle response towards temperature, pH, and kosmotropic as well as chaotropic salts is shown via various dynamic light scattering (DLS) experiments. Furthermore, a dependency of aggregate size on solvent composition in polymer/tetrahydrofuran/water mixtures is described. The reported findings deliver a feasible pathway to high molecular weight block copolymers with tailored chemical properties and show the potential of PS-b-PMEMA as material for mechanically demanding switchable devices.

Microphase separation in bulk and surface-adsorbed binary alkane systems

Microphase separation in bulk and surface-adsorbed binary alkane systems

ADXPS/STEM studies of surface and bulk microphase behavior in block- and graft-copolymers and their blends

This study of surface and bulk microphase separation compares different block chemistries and topologies. The molecular weight and percentage of the siloxane block dominated the phase behavior, which showed coincident transitions at surfaces and in the bulk. Conditions were found where periodic arrays of spheres, lamellae or cylinders formed in the bulk, and spheres were observed at some of the surfaces. Thus quantitative interpretation of ADXPS depth profiles is questionable. Blends of copolymers with homopolymer show pronounced surface segregation with a critical concentration at ≈1 wt% siloxane in the bulk that saturates the surface. The extent of surface and bulk phase separation is strongly effected by the kinetics of solvent evaporation or thermoforming.

Diblock Copolymers at Surfaces

ABSTRACTThe surface properties of symmetric microphase separated diblock copolymers of polystyrene (PS) and polymethylmethacrylate (PMMA) were investigated using X-ray photoelectron spectroscopy (XPS), the specular reflectivity of neutrons and secondary ion mass spectrometry (SIMS). PS, the lower surface energy component, exhibited a preferential affinity for the free surface. For copolymers that are far from the bulk microphase separation transition (MST), the surface consists of a layer of pure PS. When the system is close to the MST the surface is a mixture of PS and PMMA. The PS surface excess can be described bya N-1/2 dependence, where N is the number of segments that comprise the copolymer chain. It is shown that the surface undergoes an ordering transition at a temperature T2 that is above that of the bulk MST. The ordering of the bulk lamellar morphology is induced by an ordering at the surface. This is analogous to the ferromagnetic order observed in systems such as Gd at temperatures above the bulk Curie temperature. The results here are discussed in light of previous work on copolymer surfaces and in light of mean field theory.