Phase Separation Of Block Copolymers Research Articles

Microstructure similarity analysis between synthetic phase-separated block copolymers and natural spider silk

This papers primary purpose is to explore why the microstructure of synthetic block copolymers and natural spider silk is similar at the nanoscale. This paper analyses the main chain segments and secondary structures of natural spider silk, clarifies the aggregation order, and introduces the contribution of secondary systems to the properties of natural block copolymers. Secondly, combined with the synthesis mechanism of natural spider silk, this paper summarizes and analyzes the general process of the synthesized block copolymer. Finally, the conditions of self-assembly of artificial fragments to form the structure are analyzed by employing mean-field theory and a phase diagram. Natural and ideal synthetic spider silk block copolymers have high similarity in performance. To achieve this, scientists can only start from the primary segment to understand their arrangement order in the secondary structure. Then the influence of each block on the properties of the silk fiber is analyzed. At the same time, the size and shape of self-assembled block copolymers are controlled at the micro-scale, thereby changing their properties. The mechanism above shows that the synthesized spider silk block copolymer is similar to natural spider silk in microscopic morphology.

Mixed-Polarity Copolymers Based on Ethylene Oxide and Cyclic Carbonate: Insights into Li-Ion Solvation and Conductivity

This study investigates the relationship between polarity and ionic conductivity in random and block copolymer electrolytes comprising highly flexible oligo(ethylene oxide) methyl ether methacrylate (OEM) and highly polar but glassy glycerol carbonate methacrylate (GCMA) monomers, blended with either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium triflate. Interestingly, the high polarity of GCMA did not significantly enhance ionic dissociation, and the random copolymers (POEM-r-PGCMA) showed similar or lower ionic conductivities than the POEM homopolymer. Further analysis revealed that Li+ only interacts with OEM and its counterion, not with GCMA. The less-intermixed and weakly phase-separated block copolymer (POEM-b-PGCMA) exhibited even lower conductivities than the random copolymer. Our results suggest that Li+ solvation occurs only in the POEM-rich phase and that the larger PGCMA regions, depleted of Li+, disrupt long-range ion transport. These findings provide valuable insights into the design of polymer electrolytes and how segmental mobility and functional groups with contrasting polarities affect ion transport.

Temperature-rate induced polymerization and phase separation of block copolymer toughened polymer composites

Understanding the genesis of polymer morphologies by phase separation is an indispensable pre-requirement to tailor the properties of polymers and composites thereof. In this work, we demonstrate the possibility to access and investigate phase separation processes of a block copolymer toughened epoxy resin under temperature-rate induced polymerization. By using (temperature-modulated optical) refractometry, the transition from a homogeneous, liquid and reactive system to the cured and demixed state is investigated. We show how different heating rates can affect the formation of particle-like domains (nodules) in terms of their composition and size, and the composition of the continuous phase (matrix). These effects are all governed by the underlying competition between a proceeding curing reaction and the mobility of the different macromolecular constituents on one hand, as well as the polymerization-induced demixing and the glass transition on the other.

Models for the solubility calculation of a CO2/polymer system: A review

Multiscale models are modeled at different time and spatial scales to achieve the spans among the micro-, meso-, and macroscales. The multiscale study of solubility is the most effective way to reveal its essence, which is widely used in the extraction, separation, material modification, and preparation of new materials. In this article, the progress of solubility-calculation models for CO2/polymer systems at the micro-, meso-, and macroscales is surveied. The research situation of the thermodynamic-calculation model and modern computer simulation at the macroscale is discussed, and the calculation model of molecular dynamics and particle dynamics at the micro- and mesoscales are analyzed. Focus is also given on the development trend of solubility-calculation models at different scales, particularly the mechanism and interpretability of solubility calculation at the macroscopic scale. The possible development directions of solubility big data, such as acquisition, storage, search, sharing, mining, and analysis under the background of big data, are proposed. The authors further describe the development directions of particle dynamics, coarse-grained method, and translink method on the basis of evolutionary algorithm at the micro- and mesoscales. The multiscale methods mentioned in this paper can serve as a reference in many fields, such as polymer self-assembly, phase rheological property, phase separation of block copolymers, amphiphilic molecular self-assembly into membranes, transformation and separation of vesicle morphology, and kinetic analysis. Multiscale research of solubility big data combined with deep learning and artificial intelligence may become important research directions in the future.

Order-of-Magnitude, Broadband-Enhanced Light Emission from Quantum Dots Assembled in Multiscale Phase-Separated Block Copolymers.

Achieving high emission efficiency in solid-state quantum dots (QDs) is an essential requirement for high-performance QD optoelectronics. However, most QD films suffer from insufficient excitation and light extraction efficiencies, along with nonradiative energy transfer between closely adjacent QDs. Herein, we suggest a highly effective strategy to enhance the photoluminescence (PL) of QD composite films through an assembly of QDs and poly(styrene-b-4-vinylpyridine)) (PS-b-P4VP) block copolymer (BCP). A BCP matrix casted under controlled humidity provides multiscale phase-separation features based on (1) submicrometer-scale spinodal decomposition between polymer-rich and water-rich phases and (2) sub-10 nm-scale microphase separation between polymer blocks. The BCP-QD composite containing bicontinuous random pores achieves significant enhancement of both light absorption and extraction efficiencies via effective random light scattering. Moreover, the microphase-separated morphology substantially reduces the Förster resonance energy transfer efficiency from 53% (pure QD film) to 22% (BCP-QD composite), collectively achieving an unprecedented 21-fold enhanced PL over a broad spectral range.

Scattering patterns and stress-strain relations on phase-separated ABA block copolymers under uniaxial elongating simulations.

To develop molecularly based interpretations of the two-dimensional scattering patterns (2DSPs) of phase-separated block copolymers (BCPs), we performed coarse-grained molecular dynamics simulations of ABA tri-BCPs under uniaxial stretching for block-fractions where the A-segment (glassy domain) is smaller than the B-segment (rubbery domain), and estimated the behaviour of their 2DSPs. In BCP stretching experiments, mechanical properties are generally evaluated using a stress-strain curve. We obtained 2DSPs with different contrasts for the A- and B-segments, which are indicative of the differences between X-ray and neutron scattering experiments. The small- and wide-angle behaviours of the 2DSPs originate from the morphologies of the phase-separated domains and local bond orientations, respectively. When the block-fractions are changed for a constant stress value on the stress-strain (SS) curve, the brightness of the spots in the wide-angle region of the A- and B-segment-dominant 2DSPs decreases and increases with increasing strain, respectively. We can regard the systematic changes in the small-angle 2DSPs of the glassy domain and the wide-angle 2DSPs of the rubbery domain with changes in the SS-curve as a structure-property relationship.

Dramatic differences in the fluorescence of AIEgen-doped micro- and macrophase separated systems

A phase separated block copolymer and a polymer blend containing AIEgens with different polarities exhibit dramatically different fluorescence properties.

Can single molecule localization microscopy be used to map closely spaced RGD nanodomains?

Cells sense and respond to nanoscale variations in the distribution of ligands to adhesion receptors. This makes single molecule localization microscopy (SMLM) an attractive tool to map the distribution of ligands on nanopatterned surfaces. We explore the use of SMLM spatial cluster analysis to detect nanodomains of the cell adhesion-stimulating tripeptide arginine-glycine-aspartic acid (RGD). These domains were formed by the phase separation of block copolymers with controllable spacing on the scale of tens of nanometers. We first determined the topology of the block copolymer with atomic force microscopy (AFM) and then imaged the localization of individual RGD peptides with direct stochastic optical reconstruction microscopy (dSTORM). To compare the data, we analyzed the dSTORM data with DBSCAN (density-based spatial clustering application with noise). The ligand distribution and polymer topology are not necessary identical since peptides may attach to the polymer outside the nanodomains and/or coupling and detection of peptides within the nanodomains is incomplete. We therefore performed simulations to explore the extent to which nanodomains could be mapped with dSTORM. We found that successful detection of nanodomains by dSTORM was influenced by the inter-domain spacing and the localization precision of individual fluorophores, and less by non-specific absorption of ligands to the substratum. For example, under our imaging conditions, DBSCAN identification of nanodomains spaced further than 50 nm apart was largely independent of background localisations, while nanodomains spaced closer than 50 nm required a localization precision of ~11 nm to correctly estimate the modal nearest neighbor distance (NDD) between nanodomains. We therefore conclude that SMLM is a promising technique to directly map the distribution and nanoscale organization of ligands and would benefit from an improved localization precision.

Nanoscale simultaneous chemical and mechanical imaging via peak force infrared microscopy.

Nondestructive chemical and mechanical measurements of materials with ~10-nm spatial resolution together with topography provide rich information on the compositions and organizations of heterogeneous materials and nanoscale objects. However, multimodal nanoscale correlations are difficult to achieve because of the limitation on spatial resolution of optical microscopy and constraints from instrumental complexities. We report a novel noninvasive spectroscopic scanning probe microscopy method-peak force infrared (PFIR) microscopy-that allows chemical imaging, collection of broadband infrared spectra, and mechanical mapping at a spatial resolution of 10 nm. In our technique, chemical absorption information is directly encoded in the withdraw curve of the peak force tapping cycle after illumination with synchronized infrared laser pulses in a simple apparatus. Nanoscale phase separation in block copolymers and inhomogeneity in CH3NH3PbBr3 perovskite crystals are studied with correlative infrared/mechanical nanoimaging. Furthermore, we show that the PFIR method is sensitive to the presence of surface phonon polaritons in boron nitride nanotubes. PFIR microscopy will provide a powerful analytical tool for explorations at the nanoscale across wide disciplines.

Dynamic behavior in self-assembly process of cylindrical phase PS-b-PMMA block copolymer

Self-assembly through phase separation in block copolymers (BCPs) thin films represents an attractive route to create spontaneously ordered patterns at the sublithographic range. The cost effectiveness, the fast parallel processing time as well as the compatibility with the standard microelectronics technologies make it among the most promising techniques to meet the ever challenging feature size requirements in nanotechnologies. In the present work, we investigate the behavior of cylinder forming poly (styrene-b-Methyl-Methacrylate) PS-b-PMMA self-assembly on a chemically neutralized 300mm Silicon wafer. The effects of the process parameters such as the annealing temperature and time, the film thickness, and the BCPs periodicity on the holes formation after PMMA removal were studied in systematic fashion using statistical analysis of the Critical Dimension- Scanning Electron Microscope (CD-SEM) images,focusing mainly on the Critical Diameter (CD) and circularity of holes. In particular, it was found that both (CD) in the narrow range of 10–15nm and a hole circularity of (0.8–0.9) in excess of 96% can be achieved on the whole wafer under appropriate processing conditions. The obtained results were correlated to the self-assembly process and shed some light on the dynamic of the phase separation process of BCPs. The level of reproducibility and control achieved on a 300mm silicon wafer, hold a promise for future applications in nanotechnology.

Enhanced Charge Carrier Mobility and Tailored Luminescence of n‐Type Organic Semiconductor through Block Copolymer Supramolecular Assembly

Herein, a novel and viable strategy to fabricate fully solution processable nanostructured n‐type organic semiconducting material through block copolymer supramolecular assembly consisting of polystyrene‐b‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) and an asymmetric perylenebisimide (PBI) has been demonstrated. The block copolymer supramolecular assemblies show hierarchical structure formation in two length scales (lamella within lamella) from synergistic phase separation of block copolymer and PBI molecule inside the comb block. The optical and luminescent studies clearly evidence that the nature of aggregation of the PBI molecules inside the P4VP domain through facial π–π stacking is modified with tailored luminescent properties compared to its pure state. The block copolymer supramolecular assembly with 1:1 mole ratio (4‐vinyl pyridine:PBI) shows almost three‐order enhancement of charge carrier mobility compared to pristine PBI though it has only (0.571) of PBI weight fraction. It is believed that the organic semiconductor polymeric system described here will be useful for preparing luminescent materials, organic electronic and optoelectronic devices. image

Orientation Control and Crystallization in a Soft Confined Phase Separated Block Copolymer

Microdomain orientation and crystallization were examined in a crystalline–amorphous diblock copolymer, hydrogenated poly(high-1,4-butadiene)-b-poly(high-3,4-isoprene) (E/MB), which forms cylinders of the crystallizable block (polyethylene, E). Atomic force microscopy (AFM) was used to locally control the orientation of the E cylinders. The orientation process and subsequent crystallization behavior were investigated in situ as a function of temperature by AFM. Fully confined crystallization was observed within the range 25–50 °C, with templated and breakout crystallization observed at higher crystallization temperature. The growth rate of templated crystallization along and perpendicular to the existing microdomain structure was measured, and the ratio between these rates was found to increase rapidly with decreasing temperature with a change from ∼4.8 at 100 °C to ∼8 at 97 °C. Two maxima in the degree of orientation of the crystallized regions were found: one at relatively small supercoolings (e.g., 95 ...

Tuning the mechanical properties of weakly phase-separated olefin block copolymer by establishing co-crystallization structure with the aid of linear polyethylene: the dependence on molecular chain length

Olefin block copolymer (OBC) is a novel thermoplastic elastomer possessing multiblock features but has limited mechanical property due to a partial-branched hard segment. In this study, olefin block copolymer was blended with linear polyethylene (PE) with varying molecular chain lengths in order to investigate the influence of linear polyethylene on the mechanical performance, crystallization behavior and crystalline morphology of OBCs. It was found that the addition of PE is in favor of enhancing the mechanical properties of OBC. The long PE chains are more effective for reinforcing, and thus a rubber-to-plastic transition occurs when a large amount of ultra-long PE chains is introduced. At the same time, a small addition of PEs can be fully miscible with OBC and induces co-crystallization behavior. In this way, the tie effect from the PE chains was gradually enhanced particularly for OBC/PE samples blended with ultra-long chains. In addition, crystal orientation can be further enhanced in OBC/PE blends when shear flow is applied. More interestingly, shish–kebab structure is achieved where ultra-long PE chains act as the shish, while hard segments of OBC grow epitaxially on the shish to form kebabs. Our study shows a highly effective self-reinforcing mechanism through the regulation of crystalline morphologies for OBC multiblock copolymers, in which the unique shish–kebab structure was successfully established based on an entangled system.

Silver Nanoparticle Arrays Prepared by In Situ Automatic Reduction of Silver Ions in Mussel‐Inspired Block Copolymer Films

Block copolymer phase separation has been employed to form templates for the fabrication of nanoscale patterns of metals due to their characteristic size scales that range from several nanometers to tens of nanometers. In the present work, poly(vinyl catechol‐block‐styrene) PVCa‐b‐PSt synthesized with various compositions forms unique microphase‐separated structures. Silver nanoparticles are spontaneously formed inside of the PVCa phases due to the reductive properties of the catechol moieties. The alignment and formation of silver nanoparticle arrays is successfully achieved without the need for high‐temperature thermal treatment or chemical reduction processes. The present system can be applied to the formation of nanoparticle arrays with a wide variety of metals by control of their arrangement. image

Phase Separated Block Copolymer Particles with Tuneable Morphologies: Striped, Onion, and Patchy Particles

The aqueous solution self-assembly of a series of poly(2-vinyl pyridine)-block-poly(dimethylsiloxane) (P2VP-b-PDMS) diblock copolymers is reported. The particles show a phase separated interior morphology which can be tuned from onion-like sphere to axially stacked lamella with dimensions in the nanoscale. The key to this transition is the control of the interfacial properties using a mixture of two surfactants with preferential wetting to the respective blocks (P2VP or PDMS). Influence of block weights on particle morphology was investigated with results showing that the volume fraction of PDMS plays a crucial role in self-assembly, and a non-conventional structure of a prolate spheroid nanoparticle with a unique phase separated interior morphology can be synthesised.

Enhanced Block Copolymer Phase Separation Using Click Chemistry and Ionic Junctions.

In addition to the traditional parameters of chi (χ) and degree of polymerization (N), we demonstrate that the segregation strength of a diblock copolymer can be increased by introduction of an ionic unit at the junction of the two blocks. Compared to neutral linking groups, the electrostatic interactions between counterions of adjacent domain junctions leads to increased enthalpy, segregation strength, and phase separation. As a result, the order disorder transition temperatures of block copolymers with a 1,2,3-triazolium ionic junction were observed to be significantly higher than the corresponding neutral block copolymers. To demonstrate the potential of block copolymers with ionic junctions for nanopatterning, block copolymers were prepared by click coupling of homopolymers and then used to fabricate well-defined sub-10 nm line features. We believe that the concept of improved thin-film assembly through the introduction of ionic junctions is a powerful tool for block copolymer lithography and complements chi (χ) and degree of polymerization (N) in the design of macromolecular systems with enhanced phase separation.

Conjugated polymer/fullerene nanostructures through cooperative non-covalent interactions for organic solar cells

We have previously reported the formation of polymer/fullerene core–shell composite nanofibers (NFs) through self-assembly of functionalized conjugated block copolymers and fullerene derivatives, by cooperation of orthogonal non-covalent interactions including block copolymer phase separation, fullerene aggregation, poly(3-hexylthiophene) (P3HT) crystallization and complementary hydrogen bonding. These NFs displayed improved solar cell performances and the core–shell type structures are generally insensitive to polymer/fullerene weight ratios. In order to better understand the self-assembly mechanisms of such complex systems, we have prepared a new block copolymer (P3) having a different block length ratio and studied its solution and thin film morphologies in the presence of fullerene derivatives at different weight ratios. Worm-like micelles are observed for P3 in mixed-solvent solutions, distinctly different from the well-defined NFs observed previously. Upon fullerene additions, the solution morphologies gradually change into hierarchically complex nanostructures with varying fullerene contents. Thin film morphologies are studied by atomic force microscopy (AFM) and the blends are applied in organic solar cell (OSC) devices. Our present studies provide detailed information on the self-assembly behaviors of conjugated block copolymers and fullerenes under cooperative orthogonal non-covalent interactions.

Single-Molecule Investigations of Morphology and Mass Transport Dynamics in Nanostructured Materials.

Nanostructured materials such as mesoporous metal oxides and phase-separated block copolymers form the basis for new monolith, membrane, and thin film technologies having applications in energy storage, chemical catalysis, and separations. Mass transport plays an integral role in governing the application-specific performance characteristics of many such materials. The majority of methods employed in their characterization provide only ensemble data, often masking the nanoscale, molecular-level details of materials morphology and mass transport. Single-molecule fluorescence methods offer direct routes to probing these characteristics on a single-molecule/single-nanostructure basis. This article provides a review of single-molecule studies focused on measurements of anisotropic diffusion, adsorption, partitioning, and confinement in nanostructured materials. Experimental methods covered include confocal and wide-field fluorescence microscopy. The results obtained promise to deepen our understanding of mass transport mechanisms in nanostructures, thus aiding in the realization of advanced materials systems.

Volume shrinkage and rheological studies of epoxidised and unepoxidised poly(styrene-block-butadiene-block-styrene) triblock copolymer modified epoxy resin-diamino diphenyl methane nanostructured blend systems.

Styrene-block-butadiene-block-styrene (SBS) copolymers epoxidised at different epoxidation degrees were used as modifiers for diglycidyl ether of the bisphenol A-diamino diphenyl methane (DGEBA-DDM) system. Epoxy systems containing modified epoxidised styrene-block-butadiene-block-styrene (eSBS) triblock copolymer with compositions ranging from 0 to 30 wt% were prepared and the curing reaction was monitored in situ using rheometry and pressure-volume-temperature (PVT) analysis. By controlling the mole percent of epoxidation, we could generate vesicles, worm-like micelles and core-shell nanodomains. At the highest mole percent of epoxidation, the fraction of the epoxy miscible component in the triblock copolymer (epoxidised polybutadiene (PB)) was maximum. This gave rise to core-shell nanodomains having a size of 10-15 nm, in which the incompatible polystyrene (PS) becomes the core, the unepoxidised PB becomes the shell and the epoxidised PB interpenetrates with the epoxy phase. On the other hand, the low level of epoxidation gave rise to bigger domains having a size of ∼1 μm and the intermediate epoxidation level resulted in a worm-like structure. This investigation specifically focused on the importance of cure rheology on nanostructure formation, using rheometry. The reaction induced phase separation of the PS phase in the epoxy matrix was carefully explored through rheological measurements. PVT measurements during curing were carried out to understand the volume shrinkage of the blend, confirming that shrinkage behaviour is related to the block copolymer phase separation process during curing. The volume shrinkage was found to be maximum in the case of blends with unmodified SBS, where a heterogeneous morphology was observed, while a decrease in the shrinkage was evidenced in the case of SBS epoxidation. It could be explained by two effects: (1) solubility of the epoxidised block copolymer in the DGEBA leads to the formation of nanoscopic domains upon reaction induced phase separation and (2) the plasticisation effect of the epoxidised block copolymer in the epoxy resin.

Combination of temperature and saturated vapor annealing for phase separation of block copolymer

ABSTRACTPhase separation of block copolymer films is a perspective technique for the creation of nanostructured templates. The phase separation can be induced by thermal or vapor solvent annealing. However, a standardized and reproducible technique of the phase separation is still missing, even though many papers describing various experimental conditions. In this article we have tried to develop standardized and reproducible technique of the phase separation, which can be easily scaled up. For this purpose we used the combination of the thermal and vapor annealing of poly(styrene‐b‐4‐vinylpyridine) copolymer films on a glass substrate under static conditions. The technique was tailored by the choice of optimal solvent for the vapor annealing, based on the solvent–polymer interaction. Finally, the films were reconstructed by immersing in methanol or ethanol and stretching of the P4VP component during the reconstruction was investigated by the angle‐resolved X‐ray photoelectron spectroscopy. Morphology of the films was investigated by the atomic force microscopy and confocal microscopy. The kinetics of the phase separation was also studied. The presented combined technique of the thermal and vapor annealing can be easily temperature‐controlled for reproducibly obtaining the films of a desired morphology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41853.