Block Copolymer Concentration Research Articles

Dissipative Particle Dynamics Study on Interfacial Properties of Ternary H-Shaped Copolymer–Homopolymer Blends

Dissipative particle dynamics (DPD) simulations is used to study the effect of Am/2BmAm/2 and H-shaped (Am/4)2Bm(Am/4)2 block copolymers on the interfacial properties of ternary blends. Our simulations show the following: (i) The capacity of block copolymers to diminish interfacial tension is closely linked to their compositions. With identical molecular weights and concentrations, H-shaped block copolymers outperform triblock copolymers in mitigating interfacial tension. (ii) The interfacial tension within the blends correlates positively with the escalation in H-shaped block copolymer molecular weight. This correlation suggests that H-shaped block copolymers featuring a low molecular weight demonstrate superior efficacy as compatibilizers when contrasted with those possessing a high molecular weight. (iii) Enhancing the concentration of H-shaped block copolymers fosters their accumulation at the interface, leading to a reduction in correlations between immiscible homopolymers and a consequent decrease in interfacial tension. (iv) As the length of the homopolymer chains increases, there is a concurrent elevation in interfacial tension, suggesting that H-shaped block copolymers perform more effectively as compatibilizers in blends characterized by shorter homopolymer chain lengths. These findings elucidate the associations between the efficacy of H-shaped block copolymer compatibilizers and their specific molecular characteristics.

Digital Light Processing (DLP) 3D Printing of Caprolactone Copolymers with Tailored Properties through Crystallinity.

Digital light processing (DLP) 3D printing has shown great advantages such as high resolution in the fabrication of 3D objects toward a range of applications. Despite the rapid development of photocurable materials for DLP printing, tailoring properties to meet the specific demands for various applications remains challenging. Herein, we introduce copolymers of caprolactone and allyl caprolactone offering built-in functionality for thiol-ene photochemistry, thereby omitting the need for postfunctionalization. A crystalline block copolymer and an amorphous statistical copolymer were synthesized with the same comonomer composition and molecular weight. Thio-ene photocuring with a tetrafunctional thiol cross-linker was studied at different thiol to double-bond ratios for the copolymers and their blends. All formulations undergo rapid photocuring within several seconds of irradiation with slightly higher gel fractions observed for the statistical copolymer over the block copolymer under the same conditions, suggesting a somewhat higher cross-link density. Thermal properties of the networks were dependent on the presence of the semicrystalline block copolymer, where higher melting enthalpies were reached at higher block copolymer content. Similarly, crystallinity was found to be the main contributor to the mechanical properties. For a comparable composition, the modulus of a block copolymer network was found to be 31 times higher than that of the statistical copolymer network (27.7 vs 0.89 MPa). Intermediate moduli could be obtained by blending the two copolymers. DLP-printed scaffolds from these copolymers retained their thermal properties, therefore offering an efficient approach to tailoring mechanical properties, through crystallinity. Moreover, the printed scaffold displayed shape memory properties as the first example of poly(carprolactone) (PCL) copolymers in DLP printing. These materials are readily synthesized, offer fast and high-resolution 3D printing, and are degradable and cell compatible. They offer a straightforward approach to tailoring properties of PCL-based biomaterials and devices.

Poly(Sitosterol)-Based Hydrophobic Blocks in Amphiphilic Block Copolymers for the Assembly of Hybrid Vesicles.

Amphiphilic block copolymer and lipids can be assembled into hybrid vesicles (HVs), which are an alternative to liposomes and polymersomes. Block copolymers that have either poly(sitostryl methacrylate) or statistical copolymers of sitosteryl methacrylate and butyl methacrylate as the hydrophobic part and a poly(carboxyethyl acrylate) hydrophilic segment are synthesized and characterized. These block copolymers assemble into small HVs with soybean L-α-phosphatidylcholine (soyPC), confirmed by electron microscopy and small-angle X-ray scattering. The membrane's hybrid nature is illustrated by fluorescence resonance energy transfer between labeled building blocks. The membrane packing, derived from spectra when using Laurdan as an environmentally sensitive fluorescent probe, is comparable between small HVs and the corresponding liposomes with molecular sitosterol, although the former show indications of transmembrane asymmetry. Giant HVs with homogenous distribution of the block copolymers and soyPC in their membranes are assembled using the electroformation method. The lateral diffusion of both building blocks is slowed down in giant HVs with higher block copolymer content, but their permeability toward (6)-carboxy-X-rhodamine is higher compared to giant vesicles made of soyPC and molecular sitosterol. This fundamental effort contributes to the rapidly expanding understanding of the integration of natural membrane constituents with designed synthetic compounds to form hybrid membranes.

Synthesis of Polymer Brushes on Tannic Acid-Coated Copper Particles and Surface Co-Assembly.

The synthesis of polymer brushes on inorganic particles is an effective approach to surface modification. The polymer brushes on the surface endow the substrates with new surface properties. However, the lack of functional groups and the difficulty of surface modification have made it difficult to develop an effective method for the synthesis of polymer brushes on metal surfaces. Herein, a simple and versatile strategy for synthesizing polymer brushes on copper particles is reported. Tannic acid (TA) molecules are adsorbed onto the surfaces of copper particles, forming TA coatings. Quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (qPDMAEMA-b-PS) block copolymer (BCP) chains are grafted on the TA coatings through hydrogen bonding and electrostatic interaction, and PS brushes are grafted on the copper particles. The effects of TA concentration on the adsorption of TA and PS brush synthesis are discussed. The PS brushes are able to form surface nanostructures on the copper particles through co-assembly with PDMAEMA-b-PS BCP chains. The effect of BCP concentration on the surface nanostructures is investigated. It is reasonable to expect that polymer brushes and surface nanostructures can be synthesized on different metal surfaces by using the TA-coating approach reported in this paper.

Influence of PEG-PPG-PEG Block Copolymer Concentration and Coagulation Bath Temperature on the Structure Formation of Polyphenylsulfone Membranes.

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5-15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18-20 L·m-2·h-1 for the reference PPSU membrane up to 38-140 L·m-2·h-1 for 20 wt.% PPSU/10-15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5-7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR-81-89%, DRr-26-32%, DRir-10-20%, DT-33-45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR-29-38%, DRr-6-14%, DRir-74-89%, DT-88-94%).

Toughening epoxy by nano-structured block copolymer to mitigate matrix microcracking of carbon fibre composites at cryogenic temperatures

The incorporation of rigid nanoparticles has proven to enhance microcracking resistance in carbon fibre reinforced polymer (CFRP) composites at cryogenic temperatures, enabling CFRP tanks to store cryogenic liquid like hydrogen without requiring liners. Herein, we investigate efficacy of low-modulus soft nanoparticles in addressing the microcracking challenges inherent in CFRP at cryogenic temperatures. By incorporating a tri-block copolymer (BCP) into an epoxy, nano-structured fillers with an average diameter of approximately 100 nm are formed. Experimental results reveal that, at a 2.5 wt% loading, the BCP significantly increase the fracture energy of the nanocomposite by 392% at −196 °C while maintaining stiffness and strength. More importantly, composite laminates made with the BCP-modified nanocomposite matrix can withstand cryogenic temperatures without matrix microcracking, even when they contain multiple plies with the same orientation, such as [04/904]s, which are known to be highly susceptible to matrix microcracking at cryogenic temperatures. An advanced high-fidelity micromechanical model revealed that the observed toughening effect of nanostructured block copolymer at cryogenic temperatures can be attributed to the increased fracture resistance of the nanocomposite matrix. The findings of this research demonstrate that low concentration of block copolymer can effectively mitigate the initiation and propagation of matrix microcracks in carbon fibre composites at ultra-cold temperatures.

Fully conjugated block copolymers enhance thermal stability of polymer blend solar cells

Fully conjugated donor-acceptor block copolymers are composed of covalently-linked conjugated polymers that can leverage self-assembly to realize an ordered microstructure in the active layer of photovoltaic devices. Providing a thermodynamic driving force for mesoscale structure formation may also provide enhanced morphological stability. In this work, a new donor-acceptor block copolymer is synthesized and added into polymer blend solar cells to examine their photovoltaic performance under thermal stress. Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b; 4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno [W3,4-b]thiophene)-2-carboxylate-2-6-diyl)]-block-poly{[N,N′-bis(2-octyldodecyl) naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (PTB7Th-b-PNDI) was synthesized through sequential Stille reactions. Photovoltaic performance of ternary blends comprised of PTB7Th and PNDI homopolymers with various amounts of block copolymers were examined. The addition of the block copolymer improves thermal stability, but with an initial drop in power conversion efficiency (PCE) that follows block copolymer content. Nevertheless, inclusion of 5 % of PTB7Th-b-PNDI by weight in the active layer can effectively reduce 30 % of thermal degradation of the photovoltaic devices under thermal stress at 110 °C for 168 h, without sacrificing initial PCE. Donor-acceptor block copolymers are expected to provide a broad, generalizable approach to enhance thermal stability of polymer blend solar cells.

Influence of Block Copolymer Concentration and Resin Crosslink Density on the Properties of UV‐Curable Methacrylate Resin Systems

Influence of Block Copolymer Concentration and Resin Crosslink Density on the Properties of UV‐Curable Methacrylate Resin Systems

Hybrid Supported Lipid Bilayers for Bioinspired Bioelectronics with Enhanced Stability

A promising new class of biosensors leverages the sensing mechanisms of living cells by incorporating native transmembrane proteins into biomimetic membranes. Conducting polymers (CPs) can further improve the detection of electrochemical signals from these biological recognition elements through their low electrical impedance. Supported lipid bilayers (SLBs) on CPs mimic the structure and biology of the cell membrane to enable such sensing, but their extrapolation to new target analytes and healthcare applications has been difficult due to their poor stability and limited membrane properties. Blending native phospholipids with synthetic block copolymers to create a hybrid SLB (HSLB) may address these challenges by allowing for the tuning of chemical and physical properties during membrane design. We establish the first example of HSLBs on a CP device and show that polymer incorporation enhances bilayer resilience and thus offers important benefits toward bio-hybrid bioelectronics for sensing applications. Importantly, HSLBs outperform traditional phospholipid bilayers in stability by exhibiting strong electrical sealing after exposure to physiologically relevant enzymes that cause phospholipid hydrolysis and membrane degradation. We investigate the impact of HSLB composition on membranes and device performance and demonstrate the ability to finely adjust the lateral diffusivity of HSLBs with modest changes in block copolymer content through a large compositional range. The inclusion of the block copolymer into the bilayer does not disrupt electrical sealing on CP electrodes, an essential metric for electrochemical sensors, or the insertion of a representative transmembrane protein. This work interfacing tunable and stable HSLBs with CPs paves the way for future bioinspired sensors that combine the exciting developments from both bioelectronics and synthetic biology.

Synthesis of Polymer Brushes and Removable Surface Nanostructures on Tannic Acid Coatings

Polymer brushes refer to polymer chains that are end-grafted to surfaces or interfaces at high grafting density. Polymer brushes are able to make surface self-assembly or surface coassembly with free block copolymer (BCP) chains, and surface nanostructures with different morphologies are formed on the surfaces. The formation of the surface nanostructures endows materials with new surface properties. To develop a simple and versatile approach to the synthesis of polymer brushes and surface nanostructures, the synthesis of polymer brushes and surface nanostructures on tannic acid (TA) coatings was investigated in this research. TA molecules were coated on the surfaces of amino-modified silica particles (SiO2-NH2) through noncovalent bonds. Quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (qPDMAEMA-b-PS) chains were anchored onto the TA coatings through electrostatic interaction between qPDMAEMA blocks and TA coatings, and PS brushes are formed on the particle surfaces. Thermo gravimetric analysis demonstrates the grafting of the BCP chains on the TA coatings, and the calculation results indicate that the PS chains on the silica particles are in the polymer brush regime. PS brushes on TA coatings are able to make surface coassembly with free BCP chains, and surface nanostructures with different sizes and morphologies are produced on TA coatings. The grafting density of PS blocks and BCP concentration both exert significant influences on the formation of the surface nanostructures. The surface nanostructures can be removed from the particle surfaces in the aqueous solution of sodium chloride. This research provides a simple and versatile method for the fabrication of polymer brushes and removable surface nanostructures on any solid substrates, which have specific interactions with TA molecules.

Single core and multicore aggregates from a polymer mixture: A dissipative particle dynamics study

HypothesisMulticore block copolymer aggregates correspond to self-assembly such that the polymer system spontaneously phase separates to multiple, droplet-like cores differing in the composition from the polymer surroundings. Such multiple core aggregates are highly useful capsules for different applications, e.g., drug transport, catalysis, controlled solvation, and chemical reactions platforms. We postulate that polymer system composition provides a direct means for designing polymer systems that self-assemble to such morphologies and controlling the assembly response. SimulationsUsing dissipative particle dynamics (DPD) simulations, we examine the self-assembly of a mixture of highly and weakly solvophobic homopolymers and an amphiphilic block copolymer in the presence of solvent. We map the multicore vs single core (core–shell particles) assembly response and aggregate structure in terms of block copolymer concentration, polymer component ratios, and chain length of the weakly solvophobic homopolymer. FindingsFor fixed components and polymer chemistries, the amount of block copolymer is the key to controlling single core vs multicore aggregation. We find a polymer system dependent critical copolymer concentration for the multicore aggregation and that a minimum level of incompatibility between the solvent and the weakly solvophobic component is required for multicore assembly. We discuss the implications for polymer system design for multicore assemblies. In summary, the study presents guidelines to produce multicore aggregates and to tune the assembly from multicore aggregation to single core core–shell particles.

Improving the permselectivity of asymmetric isoporous membranes by blending the micro-sized metal-organic frameworks(MOFs) crystals with block copolymer

Nanomaterials are widely used to improve the separation performance for asymmetric isoporous membranes. Different from those prevalent researches, MOFs crystals with particle sizes of 0.52–0.75 μm which were an order magnitude larger than the molecular size of block copolymers (BCPs) were loaded to casting solution, and their tailoring on membrane formation and permselectivity of isoporous membranes prepared via the SNIPS were carefully investigated. As far as we know, 3D particles with such big size have never been added to isoporous membranes before. Results from small angle X-ray scattering indicated that the microphase separation in solutions had been increased obviously although MOFs crystals were too large to co-assemble with BCPs. This interesting finding was assigned to the breathing effect from MOFs crystals that increased the effective concentrations of BCPs. Morphology observation indicated that MOFs crystals located on surface were fully covered by a thin layer of BCPs which also assembled into defect-free, isoporous structures. This result was observed even though the contents of MOFs in membranes reached 40 wt%. It was measured that the permeability and selectivity to protein mixtures improved obviously by the MOFs crystals blended to membranes. Finally, with the removal of MOFs from membranes by acid etching, the permselectivity of membranes improved further. Considering the easy synthesis and good dispersibility, micro-sized MOFs crystals can be used as more effective additives to improve the separation performances for isoporous membranes than that of nanomaterials. This finding will pave the ways for preparing the high-performance isoporous membranes by using MOFs crystals as the additives for block copolymers.

Competition between polycrystalline morphology and microphase separation in blends based on cellulose triacetate

Polymer blends based on cellulose triacetate (CTA) modified with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer (PEO-PPO-PEO or EPE) and 1,1′‑diethyl-4,4′-bipyridinium dibromide (viologen or VG) were employed to obtain nanostructured micrometric films. 3VG/CTA binary blend showed worm-like structure, which was disrupted by the addition of 5 wt% of VG as a consequence of higher partial miscibility between blend components of 3VG/CTA blend. The competition between the self-assembly ability of EPE triblock copolymer and the formation of CTA crystalline lamellae was responsible for the morphology of EPE/CTA binary blends. In the ternary blends, CTA matrix was partially miscible with both VG and PEO block of EPE triblock copolymer. AFM proved that the addition of the 3 and 5 wt% of VG into had a similar effect on the final morphology of ternary systems contained 5 and 10 wt% of EPE triblock copolymer. The obtained results confirm not only self-organization ability of EPE block copolymer but also of VG. In ternary blends, VG acted as nanostructuration agent leading to similar morphology using less content of EPE block copolymer. The results provided from this investigation work allowed to build the morphologies diagram to design CTA based blends with tuneable morphologies obtained playing with VG and EPE content.

Influence of Block Copolymer Concentration and Resin Crosslink Density on the Properties of UV‐Curable Methacrylate Resin Systems

AbstractAdditive manufacturing is on the verge of replacing established processes in dentistry, as it offers the possibility of manufacturing individual parts simply and cost‐effectively. Due to its suitability for a wide variety of materials and, above all, its high precision, the focus is currently on stereolithographic processes. Intrinsic brittleness of the used multifunctional acrylic monomers remains however one of the major challenges. One promising concept is the use of block copolymers (BCPs) guaranteeing minor effects on 3D‐printing processing and UV‐curing due to initially at least partial solubility, and hence low viscosity impact. A polycaprolactone‐polysiloxane (PCL‐PDMS‐PCL) triblock copolymer is synthesized via ring‐opening polymerization of caprolactone and used in radical UV‐cured methacrylic resin systems. Small angle X‐ray scattering measurements reveal the self‐assembly of the BCPs to objects of around 20 nm prior to curing. Subsequently, thermo‐mechanical characterization is carried out by dynamic mechanical analysis, flexural testing, and fracture toughness measurements (KIC). Transmission electron microscopy and scanning electron microscopy micrographs show a homogenous distribution of the BCPs and effective toughening via cavitation and shear yielding. The influence of the crosslink density on the toughness and the high effectiveness of block copolymers for improving fracture toughness is clearly shown.

Transport and targeted binding of Pluronic-coated nanoparticles in unsaturated porous media

The effectiveness of most in situ remedial technologies, including nanoremediation, lies on successful delivery of reagents to a subsurface target treatment zone. Targeted delivery of engineered nanoparticles (NPs) to treat petroleum hydrocarbons present in the unsaturated zone requires an understanding of their transport behaviour in these systems. A series of column experiments explored the effect of initial water saturation, flowrate, input dosage, and porous medium texture on the transport of iron oxide or cobalt ferrite NPs coated with an amphiphilic co-polymer, as well as their targeted attachment to a crude oil zone. As the initial water content increased with a concomitant reduction in air saturation, the degree of tailing present in the NP breakthrough curves (BTCs) reduced, and the mass of NPs recovered increased. Air saturation is positively correlated with the magnitude of air-water interfaces, which provide additional NP retention sites. At a lower injection flow rate, NP retention increased due to a longer residence time and comparatively high air saturation. NP transport behaviour was not sensitive to NP injection dose over the range tested. Increased retention and retardation of the NP BTC was observed in sediments with a higher clay and silt content. NPs coated with a lower concentration of a Pluronic block co-polymer to promote binding were preferentially retained within the crude oil zone. To simulate the asymmetrical NP breakthrough curves observed from the unsaturated systems required the use of a model that accounted for both mobile and immobile flow regions as well as NP attachment and detachment with nonlinear Langmuirian blocking. This model allowed examination of attachment and detachment rate coefficients which captured NP interaction with the porous medium and/or crude oil. It was found that the initial water saturation and flow rate did not have an appreciable impact on the NP attachment rate coefficient, while it increased by ~10× with increasing clay and silt content, and by ~100× in the presence of crude oil, indicating preferential NP attachment within the crude oil zone. As a result of the lower NP polymer concentration coating used to promote increased attachment to crude oil, higher retention was observed near the column inlet and was captured quantitatively by adding a depth-dependent straining term to the model. This retention behaviour represents a combination of irreversible attachment at the air-water interfaces and straining near the column inlet enhanced by the formation of NP aggregates. The detachment rate coefficient decreased with a lower initial water saturation and flowrate, but increased with higher clay and silt content. The findings from this study contribute to our understanding of the transport and binding behaviour of Pluronic-coated NPs in unsaturated conditions and, in particular, the role of initial water content, flowrate and porous medium texture. Demonstrated delivery of NPs to a target zone is an important step towards expanding the utility of NPs as treatment reagents.

In-situ constructing ultra-high-aspect-ratio core–shell nanostructures to achieve high-performance epoxy thermosets and their carbon fiber reinforced epoxy composites

Using block copolymers to improve the mechanical properties of materials was a promising method, and the effect was positively correlated with the aspect ratio of the nanostructures. However, except for worm-like and branched worm-like nanostructures, nanostructures with higher aspect ratios have not been reported so far and its forming methods was unknown. In this paper, a feasible approach was provided to in-situ construct ultra-high-aspect-ratio core–shell nanostructures in epoxy, and the morphology evolution during the epoxy preparation process was clarified. It was shown that the tensile strength, elongation at break, fracture toughness and tensile modulus of the nanostructured epoxy were simultaneously improved when the content of block copolymer was as low as 1.75 wt%, achieving 93.6 MPa (31.3% improved), 7.9% (79.5% improved), 133.5 N/mm3/2 (184%) and 2693 MPa (5.6% improved), respectively. The interlaminar shear strength (ILSS) of the corresponding carbon fiber reinforced polymer (CFRP) composites was 32.5% higher than that of the control CFRP composites. Meanwhile, it was worth pointing out that the glass transformation temperatures (Tg) of the modified epoxy matrices and their corresponding CFRPs were similar to those of the unmodified materials. The improvement mechanisms on tensile strength, toughness and ILSS were also systemically investigated. It was expected that this work could provide a feasible routine for in-situ constructing complex morphological nanostructures in epoxy resins and some new ideas for the design of next-generation advanced composites.

Exploring the effect of block copolymer architecture and concentration on the microstructure, electrical conductivity and rheological properties of PP/PS blend nanocomposites

The interface between polymer matrices and nanofillers is critical for efficient interaction to achieve the desired final properties. In this work, block copolymers were utilized to control the interface and achieve optimum interfacial interaction. Specifically, we studied the compatibilizing effects of styrene-ethylene/butadiene-styrene (SEBS) and styrene-ethylene/propylene (SEP) block copolymers on the morphology, conductivity, and rheological properties of polypropylene-polystyrene (PP/PS) immiscible blend with 2 vol% multiwall carbon nanotube (MWCNT) at different blend compositions of PP/PS 80:20, 50:50 and 20:80.MWCNTs induced co-continuity in PP/PS blends and did not obstruct with the copolymer migration to the interface. Copolymers at the interface led to blend morphology refinement. Adding block copolymers at a relatively low concentration of 1 vol% to compatibilize the PP/PS 80:20 blend substantially increased the electrical conductivity from 5.15*10−7S/cm for the uncompatibilized blend to 1.07*10−2S/cm for the system with SEP and 1.51*10−3S/m for the SEBS system. These values for the compatibilized blends are about 4 orders of magnitude higher due to the interconnection of the droplet domains. For the PP/PS 50:50 blend, the SEBS copolymer resulted in a huge increase in conductivity at above 3 vol% concentration (conductivity increased to 3.49*10−3S/cm from 5.16*10−7S/cm). Both the conductivity and the storage modulus increased as the SEBS copolymer content was increased. For the PP/PS 20:80 blend, we observed an initial decrease in conductivity at lower copolymer concentrations (1–3 vol%) and then an increase in conductivity to values higher than the uncompatibilized system, but only at a higher copolymer concentration of 10 vol%. The triblock copolymer (SEBS), which had 60 wt% PS content, shows a more significant increase in rheological properties compared to the diblock copolymer (SEP). The morphology shows that the interaction between MWCNT and PS is stronger than the interaction between MWCNT and PP, hence there is selective localization of the nanofiller in the PS phase as predicted by Young’s equation and by molecular simulation.

Homopolymer-Assisted Fusions of Polymer Brushes and Block Copolymer Vesicles

The applications of materials are closely associated with surface structures and properties. Surface coassembly of block copolymers (BCPs) and polymer brushes is an effective method to fabricate surface structures with tunable properties. The surface coassembly approach not only provides a method for the fabrication of surface structures but also provides a method for the synthesis of hybrid materials with hierarchical nanostructures. In this research, polystyrene (PS)-assisted fusions of PS brushes on silica particles and BCP vesicles in a surface coassembly process are studied. The concentrations of BCP and PS homopolymer are two key parameters in the fusion process. When the BCP concentration is held constant at 3 mg/mL, with an increase in PS concentration, aggregation of silica particles and the fusions of polymer brushes and BCP vesicles are observed. When the BCP concentration is kept at 8 mg/mL, large hybrid compound structures composed of silica particles and the fused vesicles are formed. In the surface coassembly process, the addition of PS leads to an increased volume percentage of the solvophobic component in the system. To reduce the surface energy and the unfavorable contact between the solvent and PS, silica particles with PS brushes and BCP vesicles are fused into large compound structures. A variety of hybrid materials with hierarchical macro-/mesostructures can be fabricated by using this method.

Block Copolymer and Nanosilica-Modified Epoxy Nanocomposites

The effects of nanoscale silica particle additives on the tensile properties of neat and poly(ethylene-alt-propylene)-b-poly(ethylene oxide) block copolymer (BCP)-modified epoxies were evaluated. Nanosilica and BCP modifiers were dispersed both individually and together in epoxy formulations. The nanosilica formed a stable dispersion, and BCP modifiers formed well-dispersed spherical micelle nanostructures in the matrix. When both additives were used, BCP micelles were observed to adsorb on nanosilica surfaces, resulting in limited aggregation of nanosilica particles. Tensile tests on bulk specimens showed that the addition of nanosilica to both neat and BCP-modified epoxy formulations increased the modulus of the composites. Compact tension tests also revealed increases in the critical stress intensity factor, KIc, and critical strain energy release rate, GIc, in both the block copolymer and nanosilica-modified epoxies. Combining both additives in the epoxy enhanced toughness beyond that obtained with the individually modified formulations. Increasing nanosilica loading up to 25 wt % produced a monotonic increase in the modulus and GIc. The nanocomposite with 25 wt % nanosilica reached an optimal level of toughness at low BCP concentrations (ca. 4 wt %). Scanning electron micrographs obtained from fracture surfaces revealed topological features indicative of micelle cavitation and nanosilica debonding, toughening mechanisms that operate in concert.

Microfluidic fabrication of polymer blend particles containing poly(4-butyltriphenylamine)-block-poly(methyl methacrylate): effect of block copolymer and rate of solvent evaporation on morphology

Here, we reported particles with approximately 80-μm diameter with phase-separated morphology of ternary polymer blends containing poly(4-butyltriphenylamine) (PBTPA), poly(methyl methacrylate) (PMMA), and PBTPA-b-PMMA fabricated via a microfluidic emulsification technique with a Y-shaped microreactor followed by a solvent evaporation. Addition of block copolymer changed the macroscopic structure from core-shell to Janus and more complicated sea-island type with the increase of the block copolymer content. The Janus structure with a PMMA hemisphere containing small PBTPA domain was observed at 10 wt% of the block copolymer. Meanwhile, the rapid evaporation changed the morphology macroscopically from the Janus to the undeveloped one where PMMA-rich phase mainly located at center sandwiched with outside PBTPA phases, suggesting that morphologies are governed by the kinetical factors together with the conventionally accepted thermodynamic ones. After the solvent annealing with toluene, distinct and enlarged PMMA phase appeared radiately, of which size gradiently decreased from the surface to the center (200–500 nm) in each particle.