From Computer Simulation to Synthesis of Highly Lithium-Ion Conductive Block Copolymers with Bicontinuous Morphology

Bicontinuous morphologies are ubiquitous in nature and occur at various length scales. Topological features of two such morphologies arising in an ordered block copolymer at equilibrium and a polymer blend during spinodal decomposition are measured from three-dimensional images. Interfacial curvature, coordination number, and interjunction distance distributions exhibit remarkable similarity in these systems, despite vastly different length scales. A channel coordination of 3 is dominant in both morphologies, and topological measurements such as the Euler-Poincaré characteristic and genus are reported.

Block copolymers and amphiphile/water systems both exhibit very rich polymorphism. The bicontinuous cubic morphologies mediate the transformation from a lamellar phase to a hexagonally-packed cylinder phase. However, certain bicontinuous cubic morphologies can theoretically transform smoothly (without disruption or tearing) to other bicontinuous cubic morphologies in response to variation in temperature and concentration. These bicontinuous phases are best understood in terms of their associated minimal surfaces. The minimal surfaces D (i.e, ordered bicontinuous double diamond OBDD for block copolymer; cubic phase Q224 for amphiphile/water system), G (i.e., gyroid G* for block copolymer; cubic phase Q230 for amphiphile/water system), and P (cubic phase Q229 for amphiphile/water system; not yet reported for block copolymers) were computed and their two-dimensional projections on the plane reveals various 4-fold and 3-fold symmetries that are at times indistinguishable from that of the hexagonal phase. More...

Polymeric bicontinuous morphologies were created by thermal annealing mixtures of poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymers and stabilized Au-core/Pt-shell (Au–Pt) nanoparticles. These Au–Pt nanoparticles have a cross-linked polymeric shell to promote thermal stability and are designed to adsorb strongly to the interface of the PS-b-P2VP block copolymer due to the favorable interaction between P2VP block and the exterior of the cross-linked shell of the nanoparticle. The interfacial activity of these Au–Pt nanoparticles under thermal annealing conditions leads to decrease in domain size of the lamellar diblock copolymer. As nanoparticle volume fraction ϕp was increased, a transition from a lamellar to a bicontinuous morphology was observed. Significantly, the effect of these shell-cross-linked Au–Pt nanoparticles under thermal annealing conditions was similar to those of traditional polymer grafted Au nanoparticles under solvent annealing conditions reported previously. These results suggest a general strategy for producing bicontinuous block copolymer structures by thermal processing through judicious selection of polymeric ligands, nanoparticle core, and block copolymer.

Electrostatic tuning of block copolymer morphologies by inorganic macroions

Structure development in multi-block copolymerisation: comparison of experiments with cell dynamics simulations

The bi-continuous network morphology in the hybrid quantum dot solar cell is formed using the block copolymer P3HT-b-PS since the PS block is more compatible with the quantum dots.

The self-assembly of block copolymers offers opportunities for the facile organization and templating of inorganic nanomaterials. Here, we describe a morphology map for a poly(methyl methacrylate)-b-poly(n-butyl acrylate)-b-poly(methyl methacrylate) (PMMA-b-PnBA-b-PMMA) block copolymer/polycarbosilane system that allows for tunable control over nanoscale micelle geometry via manipulation of the preceramic polymer content. We produced gels with spherical, wormlike, and bicontinuous morphologies, which were processed to create silicon carbide-based ceramic structures with tunable nanoscale porosities. The role of the constituent polymers in influencing the structure and rheology of this system is discussed. The PMMA-b-PnBA-b-PMMA block copolymer/preceramic polymer system offers a number of advantages including: (i) commercial availability, (ii) rapid self-assembly kinetics, and (iii) successful conversion of the self-assembled nanostructure to ceramic via pyrolysis. This system may be useful for catalytic, structural, or thermal applications in both industrial and academic settings because of its ease of use and relatively inexpensive reagents.

The surface chemistry of nanoparticles can be modified so that these particles behave like surfactants and localize at interfaces between two fluids. We demonstrate that small volume fractions phi(P) of such surfactant nanoparticles added to lamellar diblock copolymers lead initially to a decrease in lamellar thickness with phi(P), a consequence of decreasing interfacial tension, up to a critical value of phi(P), beyond which the block copolymer adopts a bicontinuous morphology. These bicontinuous morphologies have stable domain spacings below 100 nm that further decrease with increasing phi(P) and offer new routes to nanoscopically engineered polymer films with potential photovoltaic, fuel cell, and battery applications.

Alkaline fuel cell membranes have the potential to reduce the cost and weight of current fuel cell technology, but they still have not been broadly commercialized due to poor hydroxide conductivities and mechanical properties, in addition to low chemical stability. One approach to address these mechanical and transport shortcomings is forming a morphologically bicontinuous network of an ion transporting phase and a hydrophobic phase to provide mechanical strength. In this report, membranes having bicontinuous morphologies are fabricated by cross-linking cation-containing block copolymers with hydrophobic constituents. This is accomplished in a single step and does not require postpolymerization modification. The resulting materials conduct hydroxide ions very rapidly, as high as 120 mS cm–1 in liquid water at 60 °C. The methodological changes required to obtain a bicontinuous morphology from such strongly self-segregating block copolymers, relevant to other applications in which bicontinuous structures ar...

Advances in self-ordering macromolecules and nanostructure design

Morphological effects to carrier mobility in a RO-PPV/SF-PPV donor/acceptor binary thin film opto-electronic device

Lithium metal is a promising anode for next generation lithium batteries due to its high theoretical energy density (3860mAh g-1). However, despite the attractive feature of lithium metal, its dendrite could form short circuit inside the cells and cause serious safety problems during lithium plating and stripping process. Polymer electrolyte with high lithium transference number and high modulus would substantially mitigate dendrite growth in lithium metal battery. According to previous models, structuring the electrolyte to immobilized the anions with high shear modulus is of the various options to suppress dendrite growth. In this work, we designed a single-ion conductor (SIC) based on a block copolymer using sulfonic anion, whose structure covalently bonded with hydoxylated polyisoprene (named as sPI) to reach high transference number. Polystyrene can be used to support the mechanical properties of matrix and the adjacent polyisoprene with double bond main chain plays a decoupling role (PI(1,4)) which separate the stiff PS domain, and the lithium conducting sPI domain (referred to SII block copolymer). Using small angle X-ray scattering and transmission electron microscopy, nanostructures of membranes were identified as a bi-continuous network structure. Remarkably, the maximum conductivity was 1.4×10-4 S cm-1 at ambient temperature with merely 30 wt% solvent uptake. The lithium transference number (TLi +) was nearly unity in liquid electrolyte. The Young’s modulus of SII was 53 MPa and storage modulus was nearly 3 GPa at room temperature. This bi-continuous morphology with high TLi +, high modulus, and moderate conductivity is believed to suppress dendrite grow effectively. From galvanostatic cycling experiments, we found that the presence of PS and the sPI in SII membrane in liquid electrolyte with lithium symmetric cell provides over 245 hr in cell life time. Batteries containing SII membranes in liquid electrolyte are able to cycle at least 20 times with high coulombic efficiency (98%). This results warrant that the sPI can effectively delay lithium dendrite formation due to reduced uneven lithium deposition while maintaining the mechanical property with moderate values by adjusting PS and PI(1,4) length, and this architecture design also made the application of SIC in lithium metal polymer battery possible in the future.

Using field-theoretic simulations based on a self-consistent field theory (SCFT) with or without finite compressibility, nanoscale mesophase formation in molten linear AB and ABC block copolymers is investigated in search of candidates for new and useful nanomaterials. At selected compositions and segregation strengths, the copolymers are shown to evolve into some new nanostructures with either unusual crystal symmetry or a peculiar morphology. There exists a holey layered morphology with Im3 symmetry, which lacks one mirror reflection compared with Im3m symmetry. Also, a peculiar cubic bicontinuous morphology, whose channels are connected with tetrapod units, is found to have Pn3m symmetry. It is shown that there is another network morphology with tripod connections, which reveals P432 symmetry. The optimized free energies of these new mesophases and their relative stability are discussed in comparison with those of double gyroids and double diamonds.

As shown theoretically earlier via both weak segregation and self-consistent field theories, ordering of confined molten di- and tri-block copolymer morphologies in the presence of a proper 1D patterned substrate could induce the formation of 3D bicontinuous (in particular, diamond-like) morphologies (DLMs). The purpose of the present paper is to study, unlike the previous studies, how the stable DLMs are formed not in a melt but in a solution of symmetric diblock copolymers with a nonselective solvent that wets the thin film on the patterned substrate. It is shown, via a straightforward self-consistent field calculation of the total solution free energy for various competing phases, that the DLM could be formed in the solutions (with the solvent volume fraction of 0.5), which provides much faster thermodynamic equilibration of the solution as compared to the melt. The last circumstance can ease the production of stable DLMs in thin films of copolymers. The phase diagram describing the stable phases on the plane "the pattern period-the film thickness" is built.

In this work, we examine the swelling of nanostructured block copolymer electrolytes immersed in liquid water. A series of sulfonated polystyrene-b-polyethylene-b-polystyrene (S-SES) membranes having the same nominal chemical composition but two different morphologies are prepared by systematic changes in processing. We start with a membrane comprising a mixture of homopolymer polystyrene (hPS) and a polystyrene-b-polyethylene-b-polystyrene (SES) copolymer. hPS is subsequently selectively removed from the membrane and the polystyrene domains are sulfonated to give S-SES membranes. The morphology of the membranes is controlled by controlling ϕ v, the volume fraction of hPS in the blended membrane. The morphology of the membranes was studied by small angle X-ray scattering (SAXS), cryogenic scanning transmission electron microscopy (cryo-STEM), and cryogenic electron tomography. The overall domain swelling measured by SAXS decreases slightly at ϕ v = 0.29; a crossover from lamellar to bicontinuous morphology is obtained at the same value of ϕ v. The bicontinuous morphologies absorb more water than the lamellar morphologies. By contrast, the nanodomain swelling of the bicontinuous membrane (120%) is slightly less than that of the lamellar membrane (150%). Quantitative analysis of the STEM images and electron tomography was used to determine the swelling on the hydrophilic and hydrophobic domains due to exposure to water. The hydrophilic sulfonated polystyrene-rich domain spacing increases while the hydrophobic polyethylene domain spacing decreases when the membranes are hydrated. The extent of increase and decrease is not a strong function of ϕ v.