Microdomain Morphology Research Articles

Compositional asymmetry in a crystalline-amorphous block copolymer influences the phase and crystallization behaviors of its blend with an amorphous block copolymer.

This study determined the phase and crystallization behaviors of blends composed of asymmetric polystyrene-block-poly(ethylene oxide) (PS-PEO) and symmetric polystyrene-block-poly(methyl methacrylate) (PS-PMMA). The PS blocks in the various binary block copolymers exhibited nearly identical molecular weights, whereas the molecular weight ratios of PEO and PMMA varied. The compatibility of the PEO and PMMA chains aided the binary block copolymers in co-ordering in a lamellar microdomain morphology, with the PEO and PMMA blocks sharing a common microdomain. Adding short tethered PMMA chains to long tethered PEO chains led to a decrease in the common microdomain spacing and an increase in the grafting density. These behaviors increased PEO chain stretching, causing macrophase separation. The mismatch in PEO and PMMA block lengths divided the common PEO/PMMA microdomain into two sections: the coexisting PEO/PMMA section close to the microdomain interface and the neat PEO section far away from it. The high-glass-transition-temperature PMMA reduced PEO chain mobility, inhibiting PEO crystallization in the coexisting PEO/PMMA section but not in the neat PEO section. When the block length ratio of PEO to PMMA decreased, the neat PEO section narrowed. The increase in the extent of PEO confinement led to a reduction in PEO crystallizability.

Reversible Morphology Locking via Metal Infiltration in a Block Copolymer.

Metal infiltration from an acid solution of a metal precursor into the poly(2-vinylpyridine) (P2VP) microdomains of a polystyrene-b-P2VP block copolymer is shown to reduce the uptake of solvent vapor during a subsequent solvent annealing process, locking the morphology of the self-assembled microdomains. The amount of metal, here Pt, incorporated into the P2VP increases with both metal precursor [PtCl4]2- and hydrochloric acid concentrations, reaching 0.83 Pt atom per pyridine unit. The metal is then exfiltrated using a KOH + ethylenediaminetetraacetic acid disodium salt dihydrate (Na2EDTA) complexing solution, which restores solvent uptake and unlocks the morphology. The reversibility of the metal infiltration and morphology locking is demonstrated in a multistage annealing process and is confirmed for Fe as well as Pt. Reversible locking and unlocking of block copolymer microdomain morphologies expand their utility for nanofabrication processes by allowing the morphology to be fixed during subsequent process steps.

Hydrogen Bonding-Induced Crystal Orientation Changes in Confined Microdomains Constructed by Block Copolymer Blends

This study examined crystal orientation confined within a lamellar microdomain morphology formed by the blends of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and polystyrene-block-poly(acrylic acid) (PS-b-PAA) through wide-angle X-ray diffraction. The hydrogen-bonding interaction between PEO and PAA molecules enabled block copolymers to co-organize into a microphase-separated morphology without inducing macrophase separation, but it hampered PEO crystallization. PEO crystallization that occurred at −20 °C resulted in the nucleation mechanism to be dominant, thus leading to the formation of small crystals. Small crystals allowed them to be free from spatial confinement, and they tended to be oriented with their c-axis parallel to the microdomain interface. By contrast, when PEO was crystallized at 40 °C, the high temperature facilitated PEO crystals to exhibit large crystallite sizes, which aligned perpendicularly to the microdomain interface. An increase in the PS-b-PAA concentration considerably reduced the crystallizability of PEO. The presence of a low amount of crystals and additional lateral confinement formed by hydrogen-bonded PEO/PAA reduced the degree of orientation regardless of the crystallization temperature.

Side-Chain Density Driven Morphology Transition in Brush–Linear Diblock Copolymers

We report the synthesis and self-assembly of brush-linear diblock copolymers with variable side-chain length and density. Poly(pentafluorophenyl acrylate-g-ethylene glycol)-b-polystyrene ((PPFPA-g-PEG)-b-PS) brush-linear diblock copolymers are prepared by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization of PPFPA and PS, followed by postpolymerization reaction between the precursor PPFPA-b-PS diblock copolymer and amine-functionalized PEG. By controlling the PEG chain length and the degree of substitution, we obtained brush-linear diblock copolymers with different side-chain lengths and densities. The solid-state morphologies of the diblocks are then examined by small-angle X-ray scattering (SAXS). At low PEG side-chain density, the segregation of PEG and PS away from PPFPA leads to the formation of PEG and PS lamellar domains with PPFPA in the interface. At high PEG side-chain density, the segregation is between the PPFPA-g-PEG brush block and the PS linear block, and the domain morphology is determined by the composition of the brush block. A partial experimental phase diagram is presented, and it illustrates the importance of both side-chain length and density on the microdomain morphology of brush-linear diblock copolymers.

Solubilization Behavior of Homopolymer in Its Blend with the Block Copolymer Displaying the Feature of Lower Critical Ordering Transition.

Blending with homopolymer offers a facile approach for tuning the microdomain morphology of block copolymer, provided that the homopolymer chains are uniformly solubilized in the corresponding microdomain to swell the junction point separation. Here we studied the solubilization behavior of poly(4-vinyl pyridine) homopolymer (h-P4VP) in the lamellar microdomain formed by its blends with a poly(ethylene oxide)-block-poly(4-vinyl pyridine) (PEO-b-P4VP) showing the feature of lower critical ordering transition (LCOT) in terms of weaker segregation strength at lower temperature. We revealed that, while the conventional criterion of homopolymer-to-block molecular weight ratio for attaining uniform solubilization was applicable to LCOT blend, there was an excess swelling of junction point separation upon the addition of homopolymer, leading to a decrease of interdomain distance with increasing homopolymer composition. This anomalous phenomenon was attributed to the reduction of interfacial free energy due to the incorporation of P4VP homopolymer into the microdomain interface.

Toughened PLA-b-PCL-b-PLA triblock copolymer based biomaterials: effect of self-assembled nanostructure and stereocomplexation on the mechanical properties

The current research unfolds the effect of block lengths, microdomain morphology and stereocomplexation on the mechanical properties of PLA-b-PCL-b-PLA triblock copolymers where PCL is involved to improve the poor extensibility of PLA.

Plasma Membrane Protein Nce102 Modulates Morphology and Function of the Yeast Vacuole.

Membrane proteins are targeted not only to specific membranes in the cell architecture, but also to distinct lateral microdomains within individual membranes to properly execute their biological functions. Yeast tetraspan protein Nce102 has been shown to migrate between such microdomains within the plasma membrane in response to an acute drop in sphingolipid levels. Combining microscopy and biochemistry methods, we show that upon gradual ageing of a yeast culture, when sphingolipid demand increases, Nce102 migrates from the plasma membrane to the vacuole. Instead of being targeted for degradation it localizes to V-ATPase-poor, i.e., ergosterol-enriched, domains of the vacuolar membrane, analogous to its plasma membrane localization. We discovered that, together with its homologue Fhn1, Nce102 modulates vacuolar morphology, dynamics, and physiology. Specifically, the fusing of vacuoles, accompanying a switch of fermenting yeast culture to respiration, is retarded in the strain missing both proteins. Furthermore, the absence of either causes an enlargement of ergosterol-rich vacuolar membrane domains, while the vacuoles themselves become smaller. Our results clearly show decreased stability of the V-ATPase in the absence of either Nce102 or Fhn1, a possible result of the disruption of normal microdomain morphology of the vacuolar membrane. Therefore, the functionality of the vacuole as a whole might be compromised in these cells.

Long-range lamellar formation in blends of divided-lamellar-forming liquid crystal block copolymers with liquid crystal homopolymers

Well-ordered long-range lamellar microdomain morphology is a characteristic of liquid crystal (LC) block copolymers comprising a middle main-chain type LC block connected to amorphous coil blocks at both ends. However, LC block copolymers at amorphous block volume fractions greater than 0.5 aggregate the LC blocks into laterally short lamellae divided by the amorphous blocks. In this study, it was proven that the divided lamellae can be transformed into long-range ordered lamellae by adding an LC homo-polymer into the divided-lamellar-forming LC block copolymer. The lamellar spacing was found to increase with the molecular weight of the coil block. These blends offer an easier method for preparing large-spaced long-range ordered lamellar structures using LC block copolymers.

Stabilization of complex morphologies in highly disperse AB diblock copolymers

Block copolymers have the unique property to self-assemble into ordered microstructures with well-defined periodicity. Among the various attainable microdomain morphologies, complex morphologies with inherent structural connectivity are highly desirable. While such structures are difficult to obtain in monodisperse block copolymers, they may be stabilized by increasing block dispersity. In this study, we prepare poly (styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers where dispersity of both PS and PMMA blocks are varied independently. Morphology examination of the diblocks reveals that at fixed block composition, dispersity dictated phase transition is observed. In particular, in the case where dispersity of both blocks are high, the polymers are found to exhibit perforated lamellae and disordered bicontinuous morphologies. Dissipative particle dynamics (DPD) simulations are also carried out to confirm the stability of the observed morphologies. These results show that control of block dispersity can effectively stabilize energetically disfavored complex morphologies in block copolymers.

Anion exchange membrane electrolyte preserving inverse Ia[formula omitted]d bicontinuous cubic phase: Effect of microdomain morphology on selective ion transport

The understanding of structure-morphology-property relationships is pivotal in the rational design of ion-exchange membranes with well-balanced properties. Prior observations have led to the general perception that well-defined hydrophilic/hydrophobic phase-segregated morphologies are relevant for efficient ion transport. On this basis, herein, the membrane microdomain morphology, along with its ion transport mechanisms, are discussed with respect to permselectivity. We propose and demonstrate a simple approach to construct liquid-crystalline anion-exchange membrane preserving inverse bicontinuous cubic structure. The resulting membrane exhibits improved hydroxide conductivity, superior water management ability, and enhanced alkaline stability. More importantly, the preserved 3D-interconnected ion channels selectively transport hydroxide via a reduced migration barrier, while inhibiting crossover of hydrated ions and organic solutes. These results highlight the outstanding potential of cubic liquid crystal mesophases as an attractive material for designing membranes with well-defined ion channels, while offering mechanistic insights into the structure-morphology-property relationships of membrane electrolytes for advanced energy applications.

Integrating X-Ray Computed Tomography With Chemical Imaging to Quantify Mineral Re-crystallization From Granulite to Eclogite Metamorphism in the Western Italian Alps (Sesia-Lanzo Zone)

Metamorphic transformations and fabric evolution are the consequence of thermo-dynamic processes, lasting from thousands to millions of years. Relative mineral percentages, their grain size distribution, grain orientation, and grain boundary geometries are first-order parameters for dynamic modeling of metamorphic processes. To quantify these parameters, we propose a multidisciplinary approach integrating X-ray computed microtomography (µ-CT) with X-ray chemical mapping obtained from an Electron MicroProbe Analyzer (EMPA). We used a metapelitic granulite sample collected from the Alpine HP-LT metamorphic rocks of the Mt. Mucrone (Eclogitic Micaschists Complex, Sesia-Lanzo Zone, Western Alps, Italy). The heterogeneous Alpine deformation and metamorphism allowed the preservation of pre-Alpine structural and mineralogical features developed under granulite-facies conditions. The inferred granulitic mineral association is Grt + Bt + Sil + Pl + Qtz ± Ilm ± Kfs ± Wm. The subsequent pervasive static eclogite-facies re-equilibration occurred during the Alpine evolution. The inferred alpine mineral association is Wm + Omp ± Ky + Qtz+ Grt though local differences may occur, strongly controlled by chemistry of microdomains. X-ray µ-CT data extracted from on centimeter-sized samples have been analyzed to quantify the volumetric percentage and shape preferred orientation for each mineral phase. By combining tomographic phase separation with chemical variation and microstructures (i.e., different grain-size classes for the same phase and morphology of different pre-Alpine microdomains) the pre-Alpine mineralogical phases from the Alpine overprint have been distinguished and quantified. Moreover, the sample preserves 100% of the pre-Alpine granulite fabric, which surprisingly corresponds to less than 22% of the corresponding pre-Alpine metamorphic assemblages, while the Alpine eclogitic static assemblage corresponds to 78% though no new fabric is developed. This contribution demonstrates that the combined use of EMPA X-ray chemical mapping with the X-ray µ-CT shape analysis permits a dynamic approach to constrain the chemistry of the mineral phases linked to the development of metamorphic-related static and dynamic fabrics.

Liquid-liquid phase separation of polymeric microdomains with tunable inner morphology: Mechanistic insights and applications

HypothesisLiquid-liquid phase separation (LLPS) can provide micron-sized liquid compartments dispersed in an aqueous medium. This phenomenon is increasingly appreciated in natural systems, e.g., in the formation of intracellular membraneless organelles, as well as in synthetic counterparts, such as complex coacervates and vesicles. However, the stability of these synthetic phase-separated microstructures versus coalescence is generally challenged by the presence of salts and/or surfactants, which narrows the range of possible applications. We propose a new strategy to obtain micron-sized liquid domains via LLPS, by mixing an amphiphilic copolymer with surfactants and sodium citrate in water at room temperature. ExperimentsCombining Confocal Laser Scanning Microscopy (CLSM) and Differential Scanning Calorimetry (DSC) with Dissipative Particle Dynamics (DPD) simulations, we map the phase diagram to detect LLPS and address the presence and morphology of these microscopic domains. This mapping in turn provides a first mechanistic hypothesis for the formation of such confined polymer-rich microenvironments. FindingsLLPS is driven by the phase behavior of the copolymer in water and by its associative interactions with surfactants, combined with the water-sequestering ability of salting-out electrolytes. The key factor for LLPS and formation of microdomains is the entropy-driven dehydration of the copolymer head groups, which can be quantified through the Free Water Content (FWC). Interestingly, the internal morphology of the LLPS microdomains is finely controlled by the ratio between nonionic and anionic surfactants. Beside its applicative potential, this approach represents a tool for designing synthetic mimics that improve our understanding of the occurrence of LLPS in cells.

Lamellar structures in blends of amorphous–block–main-chain liquid crystal–block–amorphous copolymers and amorphous homopolymers: Effects of the amorphous homopolymer molecular weight

T(x-y-x) block copolymers comprising of a main-chain liquid crystal (LC) BB-5(3-Me) polyester with a number-average molecular weight (Mn) of y kDa connected to poly(ethyl methacrylate) (PEMA) with a Mn of x kDa at both ends form long-range lamellar microdomains with the blocks segregated from one another over a wide-range of compositions. In this study, the lamellar forming T(5.5-39-5.5) and T(11-39-11) copolymers were blended with homoPEMA (Hz) with Mn of z kDa at a concentration of 20 wt% to give the two series of blends T(5.5-39-5.5)/Hz and T(11-39-11)/Hz. These blends were examined for microdomain morphology as a function of the molecular weight ratio of z/x. T(5.5-39-5.5)/Hz formed lamellar microdomains over the investigated z/x range of 0.8–4.1, whereas T(11-39-11)/Hz formed lamellae over a narrower range of 0.9–2.3. The lamellar spacing and the PEMA and LC lamellar thicknesses (dam and dLC) were constant over z/x and dam was greater than dam of the neat copolymer. However, the values of dLC for these two blends were different; T(5.5-39-5.5)/Hz had the same dLC as T(5.5-39-5.5), whereas T(11-39-11)/Hz had a smaller dLC than T(11-39-11). These lamellar thicknesses variations in the blends are discussed in view of the conformations of the copolymer blocks and the accommodation fashion of the Hz additives.

Morphological Evolution of Poly(solketal methacrylate)-block-polystyrene Copolymers in Thin Films

The morphological evolution of the lamellar microdomains in the thin films of symmetric poly(solketal methacrylate-b-styrene) (PSM-b-PS) copolymers that can be converted into poly(glycerol monomethacrylate-b-styrene) (PGM-b-PS) copolymers through acid hydrolysis reaction was investigated. This simple chemical transformation was performed in the solid state using trifluoroacetic acid vapor, markedly increasing the segmental interaction parameter (χ) from 0.035 to 0.438 at 25 °C and a 118 Å3 reference volume by changing the hydrophobic PSM block to the hydrophilic PGM block. To control the orientation of the lamellar microdomains using this responsive block copolymer (BCP), a protected random copolymer (PSM-r-PS) with 31 mol % SM, which was concurrently transformed into PGM-r-PS with the BCP, was used to tune the interfacial energies at the substrate. Atomic force microscopy and grazing-incidence small-angle X-ray scattering measurements as a function of exposure time to an acid vapor were performed to characterize the transition from the disordered state into the ordered state and to assess the orientation of the microdomains. As a result, a 9.4 nm full pitch lamellar microdomain morphology in the thin films was achieved after full conversion and thermal annealing, indicating that the modified substrate exhibited the surface neutrality toward the two blocks and successfully induced vertical orientation without any additional layers.

Electrostatically Tuned Microdomain Morphology and Phase-Dependent Ion Transport Anisotropy in Single-Ion Conducting Block Copolyelectrolytes

Block copolyelectrolytes are solid-state single-ion conductors which phase separate into ubiquitous microdomains to enable both high ion transference number and structural integrity. Ion transport in these charged block copolymers highly depends on the nanoscale microdomain morphology; however, the influence of electrostatic interactions on morphology and ion diffusion pathways in block copolyelectrolytes remains an obscure feature. In this paper, we systematically predict the phase diagram and morphology of diblock copolyelectrolytes using a modified dissipative particle dynamics simulation framework, considering both explicit electrostatic interactions and ion diffusion dynamics. Various experimentally controllable conditions are considered here, including block volume fraction, Flory–Huggins parameter, block charge fraction or ion concentration, and dielectric constant. Boundaries for microphase transitions are identified based on the computed structure factors, mimicking small-angle X-ray scattering p...

Binary Nanoparticles Coassembly in Bioinspired Block Copolymer Films: A Stepwise Synthesis Approach Using Multifunctional Catechol Groups and Magneto-Optical Properties

The development of hybrid films containing binary nanoparticles is one of the current key objectives in nanotechnology. Different nanoparticles dispersed in a polymer matrix exhibit diverse functions, and their properties are influenced by the interplay between the nanoparticles. The poly(vinyl catechol)-block-polystyrene (PVCa-b-PSt) block copolymer containing a catechol group, which is inspired by the adhesive protein found in the mussel foot, is an attractive platform for the coassembly of binary nanoparticles because the catechol group has various desirable properties, including the ability to coordinate metal oxides and reduce metal ions. In the fabrication of hybrid materials based on PVCa-b-PSt thin films, it is challenging to control the microdomain morphologies and the nanoparticle assembly process. In this work, we investigate the impact of solvent vapor annealing on microphase-separated nanostructures in lamellae-forming PVCa-b-PSt. We show that a fast solvent vapor annealing in a tetrahydrofur...

Morphological Behavior of A2B Block Copolymers in Thin Films

Copolymer composed of two poly(2-vinylpyridine) blocks and one polystyrene block ((P2VP)2–PS) with a PS volume fraction (ΦPS) of 0.44 was synthesized, and their morphologies in bulk and thin films were compared to linear block copolymers (BCPs) having a similar ΦPS (PS-b-P2VP). For the symmetric diblock copolymer, a lamellar morphology was observed after thermal annealing, as was expected. However, (P2VP)2–PS in the bulk showed a hexagonally packed cylindrical microdomain morphology with PS forming the cylindrical microdomains in a P2VP matrix. In thin films, after solvent annealing in the vapors of a chloroform/ethanol mixture, the cylindrical microdomain morphology was retained and the microdomains were oriented parallel to the substrate surface. With the addition of ethanol into the annealing solvent, the morphology of (P2VP)2–PS was transformed from a bicontinuous morphology to one with cylindrical microdomains of PS oriented parallel to the substrate. The lamellar microdomain of the PS-b-P2VP copolym...

Versatile Controls of Microdomain Morphologies and Temperature Dependencies in Lamellar Spacing by Blending Diblock Copolymers Bearing Antisymmetric Compositions.

The morphologies of the microphase-separated structures in the binary blends of diblock copolymers (AB/AB) have been studied intensively for the case of diblock copolymers bearing antisymmetric compositions with similar molecular weights. Here, the two diblock copolymers 1 and 2, of which compositions are 0.5 – x and 0.5 + x (0 < x < 0.5), respectively, were blended, and the morphology diagram was constructed in the plot of χZ vs the average composition of the A component, where χ is the interaction parameter between A and B segments and Z is the average degree of polymerization of the two AB diblock copolymers. The temperature-dependent morphologies were analyzed by synchrotron small-angle X-ray scattering (SAXS) measurements. It was found that the morphology diagram agrees in principle with the theoretical one for the neat AB diblocks by Matsen and Bates (Macromolecules1996, 29, 1091–1098), although the disordered phase was a bit expanded in the experimentally determined morphology diagram. Anomalous temperature dependencies in the lamellar spacing have been also comprehensively studied for the binary blends of antisymmetric diblock copolymers as a function of the degree of compositional asymmetry by closely adjusting the average composition in the blend specimen at 0.50. For this purpose, more than 20 neat diblock copolymers have been synthesized with a wide range of compositions from 0.20 to 0.87 and a range of molecular weight of 12 000–33 800. The temperature dependencies of the lamellar spacing were also analyzed by synchrotron SAXS measurements. As a result, the following things were found. The scaling exponent α in D ∼ Tα was still negative but slightly larger than the usual value (i.e., α = −0.33) for the smaller degree of asymmetry in the composition (i.e., x is small), while α became positive for the higher degree of asymmetry. The latter result is very anomalous because the temperature dependence is opposite (i.e., the lamellar spacing increases with an increase of temperature). The value of α was found to be linearly rationalized with the degree of asymmetry τ (which is especially introduced in the current paper for this purpose), for the binary blends with the average composition of 0.50. Based on this result, one can prepare lamellar microdomains, of which spacing does not change with temperature, by blending two diblock copolymers with τ = 1.33 (corresponding to 0.3 and 0.7 of compositions) having similar molecular weights. This would be important for manufacturing materials with properties (for instance, the optical property) independent of temperature. From the current study, the binary blends of the antisymmetric diblock copolymers are concluded to be versatile such that the precise controls of the morphologies and the temperature dependencies of the lamellar microdomains are plausible.

Morphology Reentry with a Change in Degree of Chain Asymmetry in Neat Asymmetric Linear A1BA2 Triblock Copolymers

We report experimental results on relationship between polymer chain architecture and morphology of microdomains of asymmetric linear triblock copolymers, S1BS2 (S: polystyrene; B: polybutadiene). For this purpose, we synthesized various asymmetric triblock copolymers having different lengths of two end-blocks. The morphology was examined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Although total molecular weight, composition, and thermal annealing temperature were kept constant, the morphology was found to change with a degree of chain asymmetry. One typical example exhibits a morphological change as cylinder → lamella → cylinder with a decrease in length of the shorter S2 end-block chains, while keeping the total molecular weight and the total polystyrene composition constant. This curious morphological behavior exhibiting a re-entrant type change is qualitatively in accord with the self-consistent field theory (SCFT) results by Matsen [J. Chem. Phys. 2000, 113, 55...

Realizing 5.4 nm Full Pitch Lamellar Microdomains by a Solid-State Transformation

A simple method was developed to realize a self-assembled block copolymer (BCP) lamellar microdomain morphology with a full pitch of 5.4 nm through an acid hydrolysis of poly(solketal methacrylate-b-styrene) (PSM-b-PS). The acid hydrolysis transforms PSM-b-PS, having two hydrophobic blocks, into poly(glycerol monomethacrylate-b-styrene) (PGM-b-PS), having one hydrophilic and one hydrophobic block. This transformation markedly increases the segmental interaction parameter such that a phase-mixed PSM-b-PS can be transformed in the solid state into a microphase-separated BCP without the use of any additives. Correlation hole scattering of the PSM-b-PS in the phase mixed state yields a segmental interaction parameter (χ) given by χ = 0.0196 + 4.694/T, where T is the absolute temperature. With the symmetric BCPs used in this study, the ordered lamellar microdomain pitch was determined by small-angle X-ray scattering (SAXS) as a function of the degree of polymerization (16 ≤ N ≤ 1246). For the lamellar microdom...