Diblock Copolymer Chains Research Articles

Low-Viscosity Route to High-Molecular-Weight Water-Soluble Polymers: Exploiting the Salt Sensitivity of Poly(N-acryloylmorpholine).

We report a new one-pot low-viscosity synthetic route to high molecular weight non-ionic water-soluble polymers based on polymerization-induced self-assembly (PISA). The RAFT aqueous dispersion polymerization of N-acryloylmorpholine (NAM) is conducted at 30 °C using a suitable redox initiator and a poly(2-hydroxyethyl acrylamide) (PHEAC) precursor in the presence of 0.60 M ammonium sulfate. This relatively low level of added electrolyte is sufficient to salt out the PNAM block, while steric stabilization is conferred by the relatively short salt-tolerant PHEAC block. A mean degree of polymerization (DP) of up to 6000 was targeted for the PNAM block, and high NAM conversions (>96%) were obtained in all cases. On dilution with deionized water, the as-synthesized sterically stabilized particles undergo dissociation to afford molecularly dissolved chains, as judged by dynamic light scattering and 1H NMR spectroscopy studies. DMF GPC analysis confirmed a high chain extension efficiency for the PHEAC precursor, but relatively broad molecular weight distributions were observed for the PHEAC-PNAM diblock copolymer chains (Mw/Mn > 1.9). This has been observed for many other PISA formulations when targeting high core-forming block DPs and is tentatively attributed to chain transfer to polymer, which is well known for polyacrylamide-based polymers. In fact, relatively high dispersities are actually desirable if such copolymers are to be used as viscosity modifiers because solution viscosity correlates closely with Mw. Static light scattering studies were also conducted, with a Zimm plot indicating an absolute Mw of approximately 2.5 × 106 g mol-1 when targeting a PNAM DP of 6000. Finally, it is emphasized that targeting such high DPs leads to a sulfur content for this latter formulation of just 23 ppm, which minimizes the cost, color, and malodor associated with the organosulfur RAFT agent.

Solution Self-Assembly of Amphiphilic Tadpole-like Giant Molecules Constructed by Monotethering Diblock Copolymer Chain onto a Nanoparticle.

The self-assembly behavior of a tadpole-like giant molecule (TGM) constructed from a hydrophobic nanoparticle (NP) monotethered by a single amphiphilic AB diblock copolymer chain was investigated by combining self-consistent field theory and density functional theory in solution. The effects of the hydrophobicities of the B blocks and NPs (i.e., solvent properties) on the self-assembly behavior of the TGMs were investigated in the cases of weak and strong intramolecular interactions (i.e., incompatibilities) between the components of giant molecules, respectively. Besides conventional ordered aggregates (such as spheres, rings, and vesicles) with hydrophobic B-cores covered by NP shells, several aggregates with novel hierarchical structures, including vesicles with NP-inserted hydrophobic walls, bead-string-like micelles, and long cylindrical micelles with NP bumps, were obtained by tuning the solvent properties under different intramolecular interactions. Noteworthy that the simulation results show that the arrangement of the NP bumps on the long cylindrical micelles may have a certain degree of helicity, which means that these micelles may have some unique electromagnetic features such as circular dichroism. Phase diagrams as a function of the hydrophobicities of the B blocks and NPs were constructed to show the formation conditions of these novel structures. These findings can not only offer new insights into understanding of the self-assembly behavior of the TGM in solution but also provide useful guidance for simple and efficient regulation of the morphology, as well as the NP distribution and arrangement of the ordered aggregates in experiments.

Configuration and dynamics of a self-propelled diblock copolymer chain.

Active polymers are slender or chain-like self-propelled objects. Synthetic chains of self-propelled colloidal particles are one of the examples, which provide a potential way to develop varied active polymers. Here, we study the configuration and dynamics of an active diblock copolymer chain. Our focus is on the competition and the cooperation between the equilibrium self-assembly due to chain heterogeneity and the dynamic self-assembly due to propulsion. Simulations show that an active diblock copolymer chain can form the spiral(+)/tadpole(+) states under forward propulsion and the spiral(-)/tadpole(-)/bean states under backward propulsion. Interestingly, it is easier for the backward-propelled chain to form a spiral. The transitions between the states can be analyzed in terms of work and energy. For forward propulsion, we found a key quantity, i.e. the chirality of the packed self-attractive A block, which determines the configuration of the whole chain and the dynamics. However, no such quantity is found for the backward propulsion. Our results set the foundation for further study of the self-assembly of multiple active copolymer chains and provide a reference for the design and application of polymeric active materials.

Unsynchronous conformational transitions induced by the asymmetric adsorption-response of an active diblock copolymer in an inert brush.

To exploit the chemical asymmetry of diblock copolymer chains on the design of high-performance switch sensors, we propose an analytically tractable model system which contains an adsorption-responsive diblock copolymer in an otherwise inert brush, and study its phase transitions by using both analytical theory and self-consistent field calculations. The copolymer chain is chemically asymmetric in the sense that the two blocks assume different adsorption strengths, which is characterized by the defined adsorption ratio. We found that the conformation states, the number of stable phases, and transition types are mainly controlled by the length of each block and the adsorption ratio. In particular, when the length of the ungrafted block is longer than the brush chains, and the adsorption ratio is smaller than a critical value, the copolymer chain shows three thermodynamically stable states, and undergoes two unsynchronous transitions, where the two blocks respond to the adsorption in a different manner, when the adsorption changes from weak to sufficiently strong. For this kind of three-state transition, the transition point, transition barrier, and transition width are evaluated by using the self-consistent field method, and their scaling relationship with respect to the system parameters is extracted, which matches reasonably well with the predictions from the analytical theory. The self-consistent field calculations also indicate that the conformational transitions involved in the three-state transition process are sharp with a low energy barrier, and interestingly, barrier-free transitions are observed. Our finding shows that the three-state transitions not only specify a region where high performance unsynchronous switch sensors can be exploited, but may also provide a useful model understanding the unsynchronous biological processes.

Long-Term Stability of Pickering Nanoemulsions Prepared Using Diblock Copolymer Nanoparticles: Effect of Nanoparticle Core Crosslinking, Oil Type, and the Role Played by Excess Copolymers.

A poly(N,N′-dimethylacrylamide) (PDMAC) precursor is chain-extended via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of diacetone acrylamide (PDAAM) to produce PDMAC77-PDAAM40 spherical nanoparticles. Post-polymerization core-crosslinking of such nanoparticles was performed at 20 °C, and the resulting covalently stabilized nanoparticles survive exposure to methanol. The linear and core-crosslinked nanoparticles were subjected to high-shear homogenization in turn in the presence of n-dodecane to form macroemulsions. Subsequent processing of these macroemulsions via high-pressure microfluidization produced nanoemulsions. When using the core crosslinked nanoparticles, the droplet diameter was strongly dependent on the copolymer concentration. This indicates that such nanoparticles remain intact under the processing conditions, leading to formation of genuine Pickering nanoemulsions with a z-average diameter of 244 ± 60 nm. In contrast, the linear nanoparticles undergo disassembly to afford molecularly dissolved diblock copolymer chains, which stabilize oil droplets of 170 ± 59 nm diameter. The long-term stability of these two types of n-dodecane-in-water nanoemulsions with respect to Ostwald ripening was examined using analytical centrifugation. When prepared at the same copolymer concentration, Pickering nanoemulsions stabilized by core-crosslinked nanoparticles proved to be significantly more stable than the nanoemulsion stabilized by the amphiphilic PDMAC77-PDAAM40 chains. Moreover, higher copolymer concentrations led to a significantly faster rate of droplet growth. This is attributed to excess copolymer facilitating the diffusion of n-dodecane through the aqueous phase. Finally, analytical centrifugation is used to assess the long-term stability of the analogous squalane-in-water nanoemulsions. These systems are much more stable than the corresponding n-dodecane-in-water nanoemulsions, regardless of whether the copolymer is adsorbed as sterically stabilized nanoparticles or surface-active chains.

Complexation of a Polyelectrolyte Brush with Oppositely Charged AB Diblock Copolymers: The Zipper Brushes

AbstractThe internal stratification of a polyelectrolyte complex (zipper brush) formed by mixing of an anionic charged polyelectrolyte brush (PEB) with cationic‐neutral diblock copolymers bearing a very long neutral block is studied by means of molecular dynamics simulations. The authors find that the fraction of the neutralized PEB units in the mixture increases as the fraction of the PEB charged units (a) increase for high grafting densities (d). Due to the charge neutralization condition, from the initial PEB through the complexation with the appropriate choice of a cationic‐neutral copolymer, neutral brush having grafting density lower, equal, or much higher than that of the PEB are obtained. The addition of monovalent salt in the mixture with concentrations 0.1 and 1 m leads to a reduction in complexed diblock copolymer chains of up to 91% and practically the initial PEB is recovered. The findings are in full agreement with existing experimental predictions and provide new insights into the structure and the shape of the coacervate. The latter progressively changes from a dense film to perforated film, to lamella, to pinned micelles, to stacks as a, d, and the molecular weights of the PEB and diblock copolymer blocks are altered.

Hydrophilic Cross-Linked Aliphatic Hydrocarbon Diblock Copolymer as Proton Exchange Membrane for Fuel Cells.

This study proposes a hydrophobic and hydrophilic aliphatic diblock copolymer wherein the hydrophobic block contains glycidyl methacrylate (GMA) units that are distanced by poly(acrylonitrile) (PAN) segments to fabricate a proton exchange membrane (PEM). This diblock copolymer also known as ionomer due to the hydrophilic block comprising 3-sulfopropyl methacrylate potassium salt (SPM) block. The diblock copolymer was synthesized in the one-pot atom transfer radical polymerization (ATRP) synthesis. Subsequently, the membrane was fabricated by means of solution casting in which an organic diamine, e.g., ethylene diamine (EDA), was introduced to crosslink the diblock copolymer chains via the addition of amine to the epoxide group of GMA. As a result, the PEM attained possesses dual continuous phases, in which the hydrophobic domains are either agglomerated or bridged by the EDA-derived crosslinks, whereas the hydrophilic domains constitute the primary proton conducting channels. The in-situ crosslinking hydrophobic block by using a hydrophilic cross-linker represents the merit aspect since it leads to both improved proton conductivity and dimensional stability in alcohol fuel. To characterize the above properties, Nafion® 117 and random copolymer of P(AN-co-GMA-co-SPM) were used as control samples. The PEM with the optimized composition demonstrates slightly better fuel cell performance than Nafion 117. Lastly, this diblock ionomer is nonfluorinated and hence favors lowering down both material and environmental costs.

Conformational transitions of adsorption-responsive single diblock copolymers in homopolymer brushes.

Using self-consistent field calculations, we examine the effect of brush polydispersity on conformational transitions of single adsorption-active diblock copolymer chains embedded in inert polydisperse brushes. To represent the polydispersity, we adopt the continuous Schulz-Zimm chain length distributions, and three typical distributions are chosen such that a wide range of polydispersity is covered. A phase diagram of the diblock copolymer switches has been constructed showing that the first order phase transitions occupy a larger space in the case of polydisperse brushes. We further characterize these first order phase transitions by specifying their transition points, transition widths and transition barriers, where the latter two are particularly important as they determine the performance of the polymer switches. Our calculation indicates that polydispersity has different effect on the switching behavior depending on the lengths of both the active block and the inert block of the copolymer switch chain. In general, polydispersity improves the switching performance in the case of short active blocks, i.e. shorter or not very longer than the average length of the brush chains, and the corresponding energy barrier is smaller than a few kBT. In contrast, monodisperse brushes have the advantages when these two blocks are particularly long, i.e., lower transition barriers and fast switching. Notably, when the inert block approaches the average length of the brush chains, the transition barrier becomes almost zero in any case for monodisperse brushes, while a large finite value is still observed for that in polydisperse brushes. The complex interplay between the brush polydispersity and the switch behavior is attributed to the wide-range repulsions generated by the polydisperse brushes.

Hierarchical supramolecular assembly of a single peptoid polymer into a planar nanobrush with two distinct molecular packing motifs

Hierarchical nanomaterials have received increasing interest for many applications. Here, we report a facile programmable strategy based on an embedded segmental crystallinity design to prepare unprecedented supramolecular planar nanobrush-like structures composed of two distinct molecular packing motifs, by the self-assembly of one particular diblock copolymer poly(ethylene glycol)-block-poly(N-octylglycine) in a one-pot preparation. We demonstrate that the superstructures result from the temperature-controlled hierarchical self-assembly of preformed spherical micelles by optimizing the crystallization-solvophobicity balance. Particularly remarkable is that these micelles first assemble into linear arrays at elevated temperatures, which, upon cooling, subsequently template further lateral, crystallization-driven assembly in a living manner. Addition of the diblock copolymer chains to the growing nanostructure occurs via a loosely organized micellar intermediate state, which undergoes an unfolding transition to the final crystalline state in the nanobrush. This assembly mechanism is distinct from previous crystallization-driven approaches which occur via unimer addition, and is more akin to protein crystallization. Interestingly, nanobrush formation is conserved over a variety of preparation pathways. The precise control ability over the superstructure, combined with the excellent biocompatibility of polypeptoids, offers great potential for nanomaterials inaccessible previously for a broad range of advanced applications.

Novel nano-patterned structures of mixed hairy nanoparticles in single layer

Tethering mixed homo/diblock polymer chains on the nanoparticles (NPs) imposes simultaneous enthalpic and entropic influences on their self-assembly. In the aggregation of these NPs, the chain distribution is strongly influenced by the neighboring NPs. Therefore, the so-called mutual templating of the NPs is the main reason for the formation of the exotic self-assembly structures of grafted chains. In this study, by using dissipative particle dynamics simulations, we design three representative mixed hairy nanoparticles (MHNPs) systems and investigate their microphase separation process during solvent evaporation. The minimal model for the MHNP is grafting two types of incompatible (A and B) homopolymer chains on the same graft-site with uniform distribution on the NP surface. Based on the minimal model, adding a C block at the free end of both A and B blocks facilitates the investigation of the influence of chain composition on microphase separation structures. In the third model, we change the B chain in the minimal model into a BC diblock copolymer chain to study the influence of chain mismatch on the formation of nano-patterns. By comparing the microphase structures and their formation processes, we can find that wedge-shaped nanostructures appear in specific range of interparticle distances (D) due to mutual templating; adding another block will terminate the mutual templating effect and results in the wedge-shaped nanostructures attaching to the NP surface surrounded by the ring structure formed by outer block C; for the systems with chain mismatch, apertures with six-fold symmetry appear in the monolayer film formed by MHNPs when D is large enough. These findings facilitate the design and fabrication of advanced functional materials with ordered structures on the nanoparticle level.

Hybrid Mesoporous Silica Nanoparticles Grafted with 2-(tert-butylamino)ethyl Methacrylate-b-poly(ethylene Glycol) Methyl Ether Methacrylate Diblock Brushes as Drug Nanocarrier.

This paper introduces the synthesis of well-defined 2-(tert-butylamino)ethyl methacrylate-b-poly(ethylene glycol) methyl ether methacrylate diblock copolymer, which has been grafted onto mesoporous silica nanoparticles (PTBAEMA-b-PEGMEMA-MSNs) via atom transfer radical polymerization (ATRP). The ATRP initiators were first attached to the MSN surfaces, followed by the ATRP of 2-(tert-butylamino)ethyl methacrylate (PTBAEMA). CuBr2/bipy and ascorbic acid were employed as the catalyst and reducing agent, respectively, to grow a second polymer, poly(ethylene glycol) methyl ether methacrylate (PEGMEMA). The surface structures of these fabricated nanomaterials were then analyzed using Fourier Transform Infrared (FTIR) spectroscopy. The results of Thermogravimetric Analysis (TGA) show that ATRP could provide a high surface grafting density for polymers. Dynamic Light Scattering (DLS) was conducted to investigate the pH-responsive behavior of the diblock copolymer chains on the nanoparticle surface. In addition, multifunctional pH-sensitive PTBAEMA-b-PEGMEMA-MSNs were loaded with doxycycline (Doxy) to study their capacities and long-circulation time.

Self-assembly of linear diblock copolymers in selective solvents: from single micelles to particles with tri-continuous inner structures.

Large-scale dissipative particle dynamics (DPD) simulations have been performed to investigate the self-assembly of over 20 000 linear diblock copolymer chains in a selective solvent. Specifically, we found that the transition from spherical to cylindrical vesicles and in turn to disk-like and onion-like vesicles, and finally to tri-continuous spherical particles is mainly due to the increase in the aggregation number. In addition, the structures with large aggregation numbers are formed through the fusion of smaller aggregates and the length of the corona block of the block copolymer plays a critical role in the resulting morphology. Furthermore, our simulations indicate that the very larger amount of polymer in our simulation is the key to the observation of a state of dynamic equilibrium between free chains and aggregates in solution, as well as the formation of more complex structures from linear diblock copolymers in selective solvents. Overall, this study paves the way for future coordinated experimental/computational studies on the formation of nanoparticles with complex morphologies from diblock copolymers, an area of great scientific and industrial interest.

Three-dimensional line edge roughness in pre- and post-dry etch line and space patterns of block copolymer lithography.

In this work, we employ large-scale coarse-grained molecular dynamics (CGMD) simulations to study the three-dimensional line edge roughness associated with line and space patterns of chemo-epitaxially directed symmetric block copolymers (BCPs) on a flat substrate. The di-block copolymer chain length and interaction parameters are validated with the experimental BCP period, L0 and corresponding molecular weight. Defect-free lamellae are formed, after which the system is quenched below the glass transition temperature before selectively dry-etching off one of the BCP phases. The effect of varying etch-selectivity on post-etch resist domain morphology was studied. The roughness of the polymer domain was evaluated over three process stages: annealing, pre-etching, and post-etching. Power spectral density plots were then generated to elucidate the contributions of low and high frequency roughness for the three process stages. The roughness results obtained from simulations are shown to be in close agreement with the roughness result obtained from analyzing experimental SEM images. Parameters like the Hurtz roughness exponent and correlation length inherent to the process and the BCP were also revealed from the experimental study.

Shear Modulus of an Irreversible Diblock Copolymer Network from Self-Consistent Field Theory

Using self-consistent field theory, we investigate the stretching-induced microphase separation in an irreversibly cross-linked polymer network composed of diblock copolymer chains and estimate its shear modulus. The topology of the network is fixed to a planar square lattice. The monomer density, the distribution of cross-links, and the free energy of the system are calculated. We find that the system develops circular domains at equilibrium, which may merge to lamellae upon compression or stretching. The lamellae are oriented perpendicular to the stretching direction. Cross-links are localized, but their distribution may be anisotropic. For asymmetric strands, the distributions of different type of cross-links differ from each other, indicating that the cross-link fluctuations are inhomogeneous. The stress is evaluated from the derivative of the free energy of stretched systems with respect to the deformation in the stretching direction. Using the elasticity theory of isotropic solids allows us to estimate the shear modulus. We find that the shear modulus increases if the network fluctuations are inhomogeneous. Our findings may provide guidance for the design of stiffer soft matter materials.

Unfolding of a diblock chain and its anomalous diffusion induced by active particles.

We study the structural and dynamical behavior of an A-B diblock chain in the bath of active Brownian particles (ABPs) by Brownian dynamics simulations in two dimensions. We are interested in the situation that the effective interaction between the A segments is attractive, while that between the B segments is repulsive. Therefore, in thermal (nonactive) equilibrium, the A block "folds" into a compact globule, while the B block is in the expanded coil state. Interestingly, we find that the A block could "unfold" sequentially like unknitting a sweater, driven by the surrounding ABPs when the propelling strength on them is beyond a certain value. This threshold value decreases and then levels off as the length of the B block increases. We also find a simple power-law relation between the unfolding time of the A block and the self-propelling strength and an exponential relation between the unfolding time and the length of the B block. Finally, we probe the translational and rotational diffusion of the chain and find that both of them show "super-diffusivity" in a large time window, especially when the self-propelling strength is small and the A block is in the folded state. Such super-diffusivity is due to the strong asymmetric distribution of ABPs around the chain. Our work provides new insights into the behavior of a polymer chain in the environment of active objects.

Effect of Chain Architecture on Phase Behavior of Giant Surfactant Constructed from Nanoparticle Monotethered by Single Diblock Copolymer Chain.

The phase behaviors of the giant surfactant constructed from a nanoparticle (NP) monotethered by a single AB diblock copolymer chain were investigated by combining self-consistent field theory and density functional theory. Three types of giant surfactants with different chain architectures were constructed via changing the location of NP on the diblock copolymer chain. The simulation results show that the introduction of the NP can induce phase separation of the originally disordered AB diblock copolymers, and phase diagrams as a function of the chain length ratio of A block and the attraction between A block and NP were constructed for the three giant surfactant systems. Via changing the location of NP from the end of B block to the AB-junction point and to the end of A block, the conformational entropies of the systems gradually decrease, leading to a significant difference in phase behaviors. When the NP is tethered to the end of B block, the giant surfactant system has the smallest phase-separation region in the phase diagram, and the resulting ordered structures have the smallest feature sizes. However, when the NP is tethered to the end of A block, the giant surfactant system has the largest phase-separation region, as well as the largest feature sizes of ordered structures. Moreover, the distributions of the NPs within microphase-separated domain can be well tailored by changing the chain length ratio of A block or the attraction between A block and NP in all of the three giant surfactant systems. These findings provide the guideline for the preparation of polymer-nanoparticle composites with controllable morphologies, desirable feature sizes, and precise NP distributions in experiments.

Synthesis, Characterization, and Pickering Emulsifier Performance of Anisotropic Cross-Linked Block Copolymer Worms: Effect of Aspect Ratio on Emulsion Stability in the Presence of Surfactant.

Reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization is used to prepare epoxy-functional PGMA-P(HPMA- stat-GlyMA) diblock copolymer worms, where GMA, HPMA, and GlyMA denote glycerol monomethacrylate, 2-hydroxypropyl methacrylate, and glycidyl methacrylate, respectively. The epoxy groups on the GlyMA residues were ring-opened using 3-aminopropyltriethoxysilane (APTES) in order to cross-link the worm cores via a series of hydrolysis-condensation reactions. Importantly, the worm aspect ratio can be adjusted depending on the precise conditions selected for covalent stabilization. Relatively long cross-linked worms are obtained by reaction with APTES at 20 °C, whereas much shorter worms with essentially the same copolymer composition are formed by cooling the linear worms from 20 to 4 °C prior to APTES addition. Small-angle X-ray scattering (SAXS) studies confirmed that the mean aspect ratio for the long worms is approximately eight times greater than that for the short worms. Aqueous electrophoresis studies indicated that both types of cross-linked worms acquired weak cationic surface charge at low pH as a result of protonation of APTES-derived secondary amine groups within the nanoparticle cores. These cross-linked worms were evaluated as emulsifiers for the stabilization of n-dodecane-in-water emulsions via high-shear homogenization at 20 °C and pH 8. Increasing the copolymer concentration led to a reduction in mean droplet diameter, indicating that APTES cross-linking was sufficient to allow the nanoparticles to adsorb intact at the oil/water interface and hence produce genuine Pickering emulsions, rather than undergo in situ dissociation to form surface-active diblock copolymer chains. In surfactant challenge studies, the relatively long worms required a thirty-fold higher concentration of a nonionic surfactant (Tween 80) to be displaced from the n-dodecane-water interface compared to the short worms. This suggests that the former nanoparticles are much more strongly adsorbed than the latter, indicating that significantly greater Pickering emulsion stability can be achieved by using highly anisotropic worms. In contrast, colloidosomes prepared by reacting the hydroxyl-functional adsorbed worms with an oil-soluble polymeric diisocyanate remained intact when exposed to high concentrations of Tween 80.

Bioassemblies Fabricated by Coassembly of Protein Molecules and Monotethered Single-Chain Polymeric Nanoparticles.

Molecular nanoparticles have been used as building blocks in the synthesis of functional materials. The grand challenges in the synthesis of the functional materials are precise control of the structures and functionalities of the materials by using nanoparticles with different architectures and properties. Monotethered single-chain polymeric nanoparticles (SCPN) are a type of nanosized asymmetric particles formed by intramolecular cross-linking of linear diblock copolymer chains. Monotethered SCPNs can be used as elemental building blocks for the fabrication of well-defined advanced structures. In this research, synthesis of biohybrid materials based on coassembly of bovine serum albumin (BSA) molecules and monotethered SCPNs is investigated. Due to the asymmetric structure of the SCPNs, positively charged SCPNs and negatively charged protein molecules coassemble into biohybrid vesicles with SCPNs on the layers and protein molecules in the walls. The self-assembled structures were analyzed by using dynamic light scattering, transmission electron microscopy, cryo-transmission electron microscopy, and atomic force microscopy. The average size of the biohybrid vesicles can be controlled by the molar ratio of SCPNs to BSA. The protein molecules in the biohybrid vesicles maintain most of the activities. This research paves a new way for the synthesis of functional biohybrid structures, and the materials can be used as protein carriers.

Nanoscale Resolution of Electric-field Induced Motion in Ionic Diblock Copolymer Thin Films.

Understanding the responses of ionic block copolymers to applied electric fields is crucial when targeting applications in areas such as energy storage, microelectronics, and transducers. This work shows that the identity of counterions in ionic diblock copolymers substantially affects their responses to electric fields, demonstrating the importance of ionic species for materials design. In situ neutron reflectometry measurements revealed that thin films containing imidazolium based cationic diblock copolymers, tetrafluoroborate counteranions led to film contraction under applied electric fields, while bromide counteranions drove expansion under similar field strengths. Coarse-grained molecular dynamics simulations were used to develop a fundamental understanding of these responses, uncovering a nonmonotonic trend in thickness change as a function of field strength. This behavior was attributed to elastic responses of microphase separated diblock copolymer chains resulting from variations in interfacial tension of polymer-polymer interfaces due to the redistribution of counteranions in the presence of electric fields.

Coassembly of Linear Diblock Copolymer Chains and Homopolymer Brushes on Silica Particles: A Combined Computer Simulation and Experimental Study

A combined computer simulation and experimental study on coassembly of poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) block copolymers and PS brushes on silica particles was performed. PS brushes on silica particles at two different grafting densities were prepared by the “grafting to” approach, and PDMAEMA-b-PS block copolymers with different molecular weights and compositions were synthesized by reversible addition–fragmentation chain transfer polymerization. In THF/methanol mixtures, block copolymer chains and PS brushes coassemble into surface micelles (s-micelles), with collapsed PS cores and PDMAEMA coronae. Meanwhile, block copolymer chains are able to self-assemble into block copolymer micelles (b-micelles). Computer simulation results and experimental results indicate that block copolymer concentration, PS and PDMAEMA block lengths, and PS grafting density exert significant influences on the coassembly process. In low BCP concentration regime, the average size of s-mic...