Macrophase Separation Research Articles

Integrating theory with machine learning for predicting polymer solution phase behavior

Flory-Huggins (FH) theory is foundational to understanding macro-phase separation in polymer solutions; however, its predictions often quantitatively disagree with experiment. Recent machine-learning (ML) methods have generated predictive models of phase behavior across a broad range of chemistries and state variables with uncertainty comparable to experiment, but they lack interpretability. In this work, we develop several hybrid frameworks that combine Flory-Huggins theory with ML to (i) further improve interpolation and extrapolation with less experimental data, as well as (ii) provide interpretability of the ML model. Using the well-studied binodal of polystyrene-cyclohexane as a case study, we compare data-derived ML models to hybrid models where the prediction is confined by a theoretical expression (theory-constrained model), or the feature vector input incorporates theoretical expressions (theory-informed model). Even though Flory-Huggins theory is imperfect, its incorporation improves performance under data sparse situations, such as when only 2 or 3 molecular masses are in the training set. However, neither approach to integrate theory provides advantages in accuracy or computational efficiency when greater coverage of the parameter space or quantities of experimental data are available, indicating that the greatest impact on predictability occurs in data sparse situations. More important than impacting the accuracy of predictions though, these hybrid models provide physical relationships, such as the molecular mass dependence of the critical point or the coefficients within a FH expression. They also afford determination of scaling behavior of theoretical parameters from cloud point experiments instead of more complicated methods. This aspect of physics-incorporated ML models enhances trust in predictions, as well as providing a systematic means to identify anomalous behavior, assess experimental data quality, and reveal unanticipated correlations among factors.

Improved selectivity and anti-aging ability for 6FDA type carbon molecular sieve membranes by mixing silicon from macro-phase separation to molecule doping

Good gas separation performance and anti-aging ability are important for the applications of carbon molecular sieve membrane (CMSM). In this work, silicon atoms in the form of siloxane-Cl are introduced into 6FDA-DABA type polyimide (PI) precursor membrane, and benzimidazoles (BI) is copolymerized into PI to effectively improve the compatibility between PI and siloxane-Cl. By varying the content of siloxane-Cl, the composite membrane changes from macro-phase separation to molecule level miscibility, which leads to the formation of silicon-rich interface layer and silicon molecule doping after high temperature pyrolysis, respectively. The residual silicon content in CMSM could be as high as 1 wt%. The high content silicon doped CMSM exhibits much improved H2 permeability retention degree (3617 Barrer of H2 permeability, 62% higher) and H2/CH4 selectivity (138, 51% higher) as compared to control CMSM after 45 days of physical aging. This work proves that the incorporation of silicon in CMSMs in proper forms could significantly improve their molecular sieving and anti-aging performances; a higher content of residual silicon and molecule level doping are highly desired. The heteroatom doping is expected to pave a new way for finely tuning the micro-structures of CMSMs and improving gas separation performances.

Complex phase transitions and phase engineering in the aqueous solution of an isopolyoxometalate cluster

Inorganic salts usually demonstrate simple phasal behaviors in dilute aqueous solution mainly involving soluble (homogeneous) and insoluble (macrophase separation) scenarios. Herein, we report the discovery of complex phase behavior involving multiple phase transitions of clear solution – macrophase separation – gelation – solution – macrophase separation in the dilute aqueous solutions of a structurally well-defined molecular cluster [Mo7O24]6− macroanions with the continuous addition of Fe3+. No chemical reaction was involved. The transitions are closely related to the strong electrostatic interaction between [Mo7O24]6− and their Fe3+ counterions, the counterion-mediated attraction and the consequent charge inversion, leading to the formation of linear/branched supramolecular structures, as confirmed by experimental results and molecular dynamics simulations. The rich phase behavior demonstrated by the inorganic cluster [Mo7O24]6− expands our understanding of nanoscale ions in solution.

Compatibilization of Polymer Blends by Ionic Bonding

Chemically dissimilar polymers are rarely miscible due to a specific entropy of mixing that scales as 1/N, where N is the degree of polymerization. As a consequence, the compatibilization of immiscible polymer blends presents a major challenge to plastics recycling efforts. We demonstrate that when the chain ends of two highly immiscible polymers are functionalized with reacting acid and base groups, ionic junctions form in situ by proton transfer, leading to the stabilization of interfaces and the suppression of macroscopic phase separation. Due to the dynamic nature of proton transfer, the microstructure can be tuned via ionic bond energy (h) and segregation strength (χN). In this work, a library of ionically end-functionalized polystyrene (PS) and polydimethylsiloxane (PDMS) is used to demonstrate the importance of end-group acidity/basicity and molecular weight on compatibilization. Well-ordered lamellae result from blending polymers with strong acid and base units, while less ordered, more swollen microphases occur in systems with weak acid and base end groups or larger molar mass. Heating the ionic blends results in reverse proton transfer and destruction of the close-contact ion pairs. As a result, domains are swollen with the resulting unbonded homopolymers, which in sufficient amounts, leads to macrophase separation. Moreover, external salt ions screen the electrostatic attractions and disturb ionic compatibilization. The self-consistent field theory (SCFT) of this system reveals that the ionic interactions can be tuned to create a broad range of morphologies, from microphases to macrophases.

Poly(dimethylsiloxane)-block-PM6 Polymer Donors for High-Performance and Mechanically Robust Polymer Solar Cells.

High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive films are mechanically brittle. In this work, highly efficient (PCE = 18%) and mechanically robust (crack-onset strain (COS) = 18%) PSCs are acheived by designing block copolymer (BCP) donors, PM6-b-PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable poly(dimethylsiloxane) (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability. The stretchability of the BCP donors increases with a longer PDMS block, and PM6-b-PDMS19k :L8-BO PSC exhibits a high PCE (18%) and 9-times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8-BO-based PSC. However, the PM6:L8-BO:PDMS12k ternary blend shows inferior PCE (5%) and COS (1%) due to the macrophase separation between PDMS and active components. In the intrinsically stretchable PSC, the PM6-b-PDMS19k :L8-BO blend exhibits significantly greater mechanical stability PCE80% ((80% of the initial PCE) at 36% strain) than those of the PM6:L8-BO blend (PCE80% at 12% strain) and the PM6:L8-BO:PDMS ternary blend (PCE80% at 4% strain). This study suggests an effective design strategy of BCP PD to achieve stretchable and efficient PSCs.

Photoinduced Fluorescence Switching in Molecular Aggregates by Topological [2+2] Cycloaddition

AbstractThe optical modulation of fluorescence characteristics in molecular aggregates, which mainly involves diverse molecular stacking and the consequent intermolecular interactions, remains a significant challenge for potential applications in optical anticounterfeiting, data storage, and imaging. Here we successfully realize in situ fluorescence switching in molecular aggregates of thianaphthene‐dioxide derivatives by topological [2+2] photocycloaddition, which represents a promising way to regulate the molecular stacking and alter photophysical processes. Notably, 2‐(3,5‐bis‐trifluoromethylphenyl)benzo[b]thiophene‐dioxide (BTO‐TF) in both crystal and powder forms exhibits a unique switching from an initial nonfluorescent state to a highly fluorescent state (ΦPL=0.46) upon UV irradiation, because of the destruction of the [2+2] cycloaddition process by volume expansion of the photodimer. Furthermore, we demonstrate such a [2+2] photocycloaddition can occur when 2‐(4‐carboxypheny)benzo[b]thiophene‐dioxide (BTO‐OH) is doped within selective polymer matrixes, and can be utilized for the visualization of macrophase separation in polymer blends.

Photoinduced Fluorescence Switching in Molecular Aggregates by Topological [2+2] Cycloaddition.

The optical modulation of fluorescence characteristics in molecular aggregates, which mainly involves diverse molecular stacking and the consequent intermolecular interactions, remains a significant challenge for potential applications in optical anticounterfeiting, data storage, and imaging. Here we successfully realize in situ fluorescence switching in molecular aggregates of thianaphthene-dioxide derivatives by topological [2+2] photocycloaddition, which represents a promising way to regulate the molecular stacking and alter photophysical processes. Notably, 2-(3,5-bis-trifluoromethylphenyl)benzo[b]thiophene-dioxide (BTO-TF) in both crystal and powder forms exhibits a unique switching from an initial nonfluorescent state to a highly fluorescent state (ΦPL =0.46) upon UV irradiation, because of the destruction of the [2+2] cycloaddition process by volume expansion of the photodimer. Furthermore, we demonstrate such a [2+2] photocycloaddition can occur when 2-(4-carboxypheny)benzo[b]thiophene-dioxide (BTO-OH) is doped within selective polymer matrixes, and can be utilized for the visualization of macrophase separation in polymer blends.

Bilayer Hydrogels by Reactive-Induced Macrophase Separation.

Bilayer hydrogels encoded with smart functions have emerged as promising soft materials for engineered biological tissues and human-machine interfaces, due to the versatility and flexibility in designing their mechanical and chemical properties. However, conventional fabrication strategies often require multiple complicated steps to create an anisotropic bilayer structure with poor interfaces, which significantly limit the scope of bilayer hydrogel applications. Here, we reported a general, one-pot, macrophase separation strategy to fabricate a family of bilayer hydrogels made of vinyl and styryl monomers with a seamless interface and a controllable layer separation efficiency (20-99%). The working principle of a macrophase separation strategy allows for the decoupling of the two gelation processes to form distinct vinyl- and styryl-enriched layers by manipulating competitive polymerization reactions between vinyl and styryl monomers. This work presents a straightforward approach and a diverse range of radical monomers, which can be utilized to create next-generation bilayer hydrogels, beyond a few available today.

Structure and Phase Behavior of Bottlebrush Diblock Copolymer-Linear Homopolymer Ternary Blends

In this work, we systematically investigated the structure and phase behavior of ternary mixtures containing an AB bottlebrush diblock copolymer and A and B linear homopolymers, where A is polystyrene and B is poly(ethylene oxide), using a combination of small-angle X-ray scattering and cloud point measurements. We found that the overall phase behavior of such mixtures closely resembles the linear counterparts, with lamellae occurring in the copolymer-rich region, macrophase separation in the homopolymer-rich region, and a bicontinuous microemulsion in between. However, the increase in lamellar and microemulsion domain spacing with increasing homopolymer content is significantly weaker than that found with ternary mixtures containing linear diblock copolymers and depends on the relative size of the homopolymers and bottlebrush side chains. We attribute this behavior to an unconventional spatial distribution of the homopolymer within the bottlebrush architecture of the diblock copolymer. These ternary mixtures offer a promising platform for the design of cocontinuous materials with an expanded parameter space made possible by the application of bottlebrush polymers.

On the origins of spontaneous spherical symmetry-breaking in open-shell atoms through polymer self-consistent field theory.

An alternative approach to density functional theory based on self-consistent field theory for ring polymers is applied to neutral atoms hydrogen to neon in their ground-states. The spontaneous emergence of an atomic shell structure and spherical symmetry-breaking of the total electron density are predicted by the model using the ideas of polymer excluded-volume between pairs of electrons to enforce the Pauli-exclusion principle and an exact electron self-interaction correction. The Pauli potential is approximated by neglecting inter-atomic correlations along with other types of correlations, and comparisons to Hartree-Fock theory are made, which also ignores correlations. The model shows excellent agreement with Hartree-Fock theory to within the standards of orbital-free density functional theory for the atomic binding energies and density profiles of the first six elements, providing exact matches for the elements hydrogen and helium. The predicted shell structure starts to deviate significantly past the element neon, and spherical symmetry-breaking is first predicted to occur at carbon instead of boron. The self-consistent field theory energy functional that describes the model is decomposed into thermodynamic components to trace the origin of spherical symmetry-breaking. It is found to arise from the electron density approaching closer to the nucleus in non-spherical distributions, which lowers the energy despite resulting in frustration between the quantum kinetic energy, electron-electron interaction, and the Pauli exclusion interaction. The symmetry-breaking effect is found to have a minimal impact on the binding energies, which suggests that the spherical-averaging approximation used in previous work is physically reasonable when investigating atomic systems. The pair density contour plots display behavior similar to polymer macro-phase separation, where individual electron pairs occupy single lobe structures that together form a dumbbell shape analogous to the 2p orbital shape. It is further shown that the predicted densities satisfy known constraints and produce the same total electronic density profile that is predicted by other formulations of quantum mechanics.

Microstructure determined the gel properties of gelatin/dextran more than the macrophase separation

Hydrogels are important in foods. Although the hydrogel microstructure has been commonly reported, the effect of the microstructure before and after gelation on gel properties was rarely investigated. This work aims to explore the effects of micro- and macro-phase separation of type-A gelatin-dextran (GE A /DE) aqueous solutions on the rheological, texture, and hydration properties of GE A /DE hydrogels. Three types of phase separation microstructures at both pH 5.0 and 7.0, e.g., DE-in-GE A emulsion, bicontinuous microstructure, and GE A -in-DE emulsion, were designed by adding different DE concentrations. GE A /DE mixtures showed macro-stability at pH 5.0, but macroscopic phase separation at pH 7.0, in which the phase separation time increased with the increasing DE concentration. During cooling-gelation, microstructures of mixtures were almost unchanged at pH 5.0, but significantly changed at pH 7.0. Interestingly, the microstructure determined the gel properties of phase-separated gels more than the macrophase separation. Microstructures of continuous phase with the gelling ability, e.g., DE-in-GE A and bicontinuous phase, hardly changed the moduli ( G′ and G″ ) and hardness of GE A /DE mixed gels, while the microstructure of GE A -in-DE without the gelling ability for continuous phase greatly reduced the moduli and hardness. This might be due to the different GE A volume fractions in GE A /DE mixed gels with different microstructures, and the mixed gel strength decreased with decreasing GE A volume fractions. Water holding capacity and swelling ratio of GE A /DE mixed gels reduced with the increasing DE concentration. This work provides some new information on how microstructure and macro-stability affect the physical properties of mixed gels. Effect of microstructure of GE A /DE before and after gelation on G′ and G″ at pH 5.0 and 7.0. • Three microstructures were designed based on gelatin/dextran phase separation. • Microstructures of macro-stable gelatin/dextran at pH 5.0 unchanged after gelation. • Microstructure determined gel properties more than the macrophase separation. • GE A volume fraction in the mixed gel might explain the effect of microstructures. • The gel strength of gelatin/dextran decreased with decreasing GE A volume fraction.

Influenza A Virus M1 Protein Non-Specifically Deforms Charged Lipid Membranes and Specifically Interacts with the Raft Boundary.

Topological rearrangements of biological membranes, such as fusion and fission, often require a sophisticated interplay between different proteins and cellular membranes. However, in the case of fusion proteins of enveloped viruses, even one molecule can execute membrane restructurings. Growing evidence indicates that matrix proteins of enveloped viruses can solely trigger the membrane bending required for another crucial step in virogenesis, the budding of progeny virions. For the case of the influenza A virus matrix protein M1, different studies report both in favor and against M1 being able to produce virus-like particles without other viral proteins. Here, we investigated the physicochemical mechanisms of M1 membrane activity on giant unilamellar vesicles of different lipid compositions using fluorescent confocal microscopy. We confirmed that M1 predominantly interacts electrostatically with the membrane, and its ability to deform the lipid bilayer is non-specific and typical for membrane-binding proteins and polypeptides. However, in the case of phase-separating membranes, M1 demonstrates a unique ability to induce macro-phase separation, probably due to the high affinity of M1's amphipathic helices to the raft boundary. Thus, we suggest that M1 is tailored to deform charged membranes with a specific activity in the case of phase-separating membranes.

The pH-dependent phase separation kinetics of type-A gelatin and dextran with different initial microstructures

The phase separation kinetics of type A gelatin and dextran (GE/DE) with different microstructures were investigated to get information on the relation between technofunctional properties and structures using static multiple light scattering (S-MLS), fluorescence microscopy, and macroscopic observations. GE/DE mixtures of 5.0 wt%/2.0 wt% and 5.0 wt%/3.0 wt% at pH = 5.50–9.00 were selected as the typical samples with the DE-in-GE and bicontinuous microstructures, respectively. Macrophase separation was found to occur in both the two mixtures at pH = 5.50–9.00 with the upper phase rich in GE and the lower phase rich in DE. However, the effect of pH on the phase separation rates of the two mixtures was different: pH-independent in DE-in-GE mixtures, while pH-dependent in bicontinuous mixtures. Specifically, the order of phase separation rates for the bicontinuous mixtures at pH = 5.50–9.00 was pH5.50 > pH6.00 > pH9.00 > pH7.00 ≈ pH8.00. Changes in the electrostatic interaction or steric exclusion effect among GE (DE) droplets at pH = 5.50–9.00 were used to explain the different phase separation kinetics of GE/DE mixtures with GE-in-DE, DE-in-GE, and bicontinuous microstructures. This work characterized the phase separation processes of GE/DE mixtures with three kinds of microstructure and provided the parameters for the phase separation kinetics at the macro-level.

Composite elastomers with on-demand convertible phase separations achieve large and healable electro-actuation.

Phase separation has been widely exploited for fabricating structured functional materials. Generally, after being fabricated, the phase structure in a hybrid material system has been set at a specific length scale and remains unchanged during the lifespan of the material. Herein, we report a strategy to construct on-demand and reversible phase switches among homogenous, nano- and macro-phase separation states in a composite elastomer during its lifespan. We trigger the nanophase separation by super-saturating an elastomer matrix with a carefully selected small-molecule organic compound (SMOC). The nanoparticles of SMOC that precipitate out upon quenching will stretch the elastomer network, yet remain stably arrested in the elastomer matrix at low temperatures for a long time. However, at elevated temperatures, the nano-phase separation will transform into the macro-one. The elastic recovery will drive the SMOC onto the elastomer surface. The phase-separated structures can be reconfigured through the homogeneous solution state at a further elevated temperature. Taking advantage of the reversible phase switches leads to a novel strategy for designing high-performance dielectric elastomers. The in situ formed nanoparticles can boost the electro-actuation performance by eliminating electro-mechanical instability and lead to a very large actuation strain (∼146%). Once the actuator broke down, SMOC could on-demand be driven to the breakdown holes and heal the actuator.

Tuning conformational asymmetry in particle-forming diblock copolymer alloys.

Self-consistent field theory is employed to compute the phase behavior of binary blends of conformationally asymmetric, micelle-forming diblock copolymers with miscible corona blocks and immiscible core blocks (a diblock copolymer "alloy"). The calculations focus on establishing conditions that promote the formation of Laves phases by tuning the relative softness of the cores of the two different Laves phase particles via independent control of their conformational asymmetries. Increasing the conformational asymmetry of the more spherical particles of the Laves structure has a stabilizing effect, consistent with the expectations of increased imprinting of the Wigner-Seitz cells on the core/corona interface as conformational asymmetry increases. The resulting phase diagram in the temperature-blend composition space features a more stable Laves phase field than that predicted for conformationally symmetric systems. The phase field closes at low temperatures in favor of macrophase separation between a hexagonally-packed cylinder (hex) phase and a body-centered cubic phase. Companion calculations, using an alloy whose components do not produce a hex phase in the neat melt state, suggest that the Laves phase field in such a blend will persist at strong segregation.

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.

Modeling Microstructure Formation in Block Copolymer Membranes Using Dynamical Self-Consistent Field Theory.

Block copolymers have attracted recent interest as candidate materials for ultrafiltration membranes, due to their ability to form isoporous integral-asymmetric membranes by the combined processes of self-assembly and nonsolvent-induced phase separation (SNIPS). However, the dependence of surface layer and substructure morphologies on the processing variables associated with SNIPS is not well understood nor is the interplay between microphase and macrophase separation in block copolymers undergoing such coagulation. Here, we use dynamical self-consistent field theory to simulate the microstructure evolution of block copolymer films during SNIPS and find that such films form the desired sponge-like asymmetric porous substructure only if the solvent and nonsolvent have opposite block selectivities and that otherwise they form a dense nonporous microphase-separated film. Our results could have important implications for the choices of solvent and nonsolvent in the processing of block copolymer membranes.

Relationship between Ion Transport and Phase Behavior in Acetal-Based Polymer Blend Electrolytes Studied by Electrochemical Characterization and Neutron Scattering

We have studied ion transport in electrolytes created by blending two different polymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The polymers covered in this study are poly(ethylene oxide) (PEO), poly(1,3,6-trioxocane) (P(2EO-MO)), and poly(1,3-dioxolane) (P(EO-MO)). Ion transport is quantified by the product κρ+ which is defined as the efficacy of the electrolytes, where κ is conductivity and ρ+ is the current fraction determined by the Bruce–Vincent method. Polymer blends can be either one-phase or macrophase-separated. We used small-angle neutron scattering (SANS) to distinguish between these two possibilities. The random phase approximation (RPA) was used to interpret SANS data from one-phase blends. The effect of added salt on polymer blend thermodynamics is quantified by an effective Flory–Huggins interaction parameter. All polymer blends were one-phase in the absence of salt. Adding salt in small concentrations results in macrophase separation in all cases. One-phase systems were observed in the PEO/P(EO-MO)/LiTFSI blends at high salt concentrations. In most of the polymer blend electrolytes, the measured κρ+ was either lower than or comparable to that of the homopolymer electrolytes. An exception to this was one-phase PEO/P(EO-MO)/LiTFSI blends electrolytes at high salt concentrations.

Hydrogen bonding induced microphase and macrophase separations in binary block copolymer blends

This study investigated the macrophase and microphase transitions of blends comprising polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and polystyrene-block-poly(acrylic acid) (PS-b-PAA). PEO and PAA molecules formed hydrogen bonds that enabled the two block copolymers to organize into a single microphase-separated morphology composed of two PS block chains in a common PS microdomain and PEO and PAA block chains in a coexisting PEO/PAA microdomain. Increasing temperature weakened the hydrogen-bonding interaction through the formation of PAA monomers and anhydride, causing the blends to macrophase separate into PS-b-PEO-rich and PS-b-PAA-rich phases. Further increasing the temperature weakened the repulsive interactions between both the PS and PEO segments and the PS and PAA segments, inducing order-to-disorder transitions in the PS-b-PEO-rich and PS-b-PAA-rich phases. However, the increasing repulsive interaction between the PEO and PAA segments with increasing temperature prevented the blends from forming an isotropic phase. The unique phase transformation of each block copolymer in the blend with an upper critical ordering transition (UCOT)-type interaction parameter, which caused the formation of a lower-critical-solution-temperature-type phase diagram, was attributed to the hydrogen-bonding interaction between PEO and PAA, which outweighed the UCOT behaviors of PS-b-PEO and PS-b-PAA and reversed the phase behaviors of their blends.

Semiflexible polymer nanocomposites: Role of stiffness on structure and macrophase separation

Polymer nanocomposites are lighter in weight as compared to the traditionally bigger size filler-loaded composites. Moreover, polymer nanocomposites show enhancement in properties with small fractions of nanoparticles. In certain cases, a high fraction of nanoparticles is needed to incorporate the required properties significantly. In most of the theoretical and simulation studies of polymeric systems, the polymer chain is modeled as ideal freely-jointed chains, thereby neglecting the effects of chain stiffness. We study a system of semiflexible polymers containing 50% volume fraction of nanoparticles using Polymer Reference Interaction Site Model (PRISM) theory. In the absence of chemical anisotropy, these systems undergo a disordered fluid phase to a macrophase-separated state. The phase transition of these systems is favored by an increase in the persistence length of the polymer chain. At lower values of persistence lengths, a slight increase in the persistence length results in a sharp decrease in the critical packing fraction. However, for longer persistence lengths, an increase in the persistence length barely affects the critical packing fraction. Studies of the local structure of these systems show that an increase in persistence length increases the polymer–polymer contacts and polymer-nanoparticle contacts. On the contrary, nanoparticle-nanoparticle contact initially increases suddenly, then decreases slightly at longer persistence lengths.