Noncentrosymmetric Structure from a Tetrablock Quarterpolymer of the ABCA Type

Open-source platform for block polymer formulation design using particle swarm optimization

Facile exploration of large design spaces is critical to the development of new functional soft materials, including self-assembling block polymers, and computational inverse design methodologies are a promising route to initialize this task. We present here an open-source software package coupling particle swarm optimization (PSO) with an existing open-source self-consistent field theory (SCFT) software for the inverse design of self-assembling block polymers to target bulk morphologies. To lower the barrier to use of the software and facilitate exploration of novel design spaces, the underlying SCFT calculations are seeded with algorithmically generated initial fields for four typical morphologies: lamellae, network phases, cylindrical phases, and spherical phases. In addition to its utility within PSO, the initial guess tool also finds generic applicability for stand-alone SCFT calculations. The robustness of the software is demonstrated with two searches for classical phases in the conformationally symmetric diblock system, as well as one search for the Frank-Kasper [Formula: see text] phase in conformationally asymmetric diblocks. The source code for both the initial guess generation and the PSO wrapper is publicly available.

Order and Disorder in ABCA' Tetrablock Terpolymers

Self-assembly of poly(styrene)-block-poly(isoprene)-block-poly(lactide)-block-poly(styrene) (PS-PI-PLA-PS' or SILS') tetrablock terpolymers, where the volume fractions of the first three blocks are nearly equivalent, was studied both experimentally and using the self-consistent field theory (SCFT). SCFT indicates that addition of the terminal PS' chain to a low-molecular-mass, hexagonally packed cylinders forming, SIL precursor can produce a disordered state due to preferential mixing of the polystyrene end-blocks with the PI and PLA midblocks in the SILS' tetrablock, alleviating the unfavorable contact between the highly incompatible PI and PLA segments. In contrast, SCFT predicts that higher-molar-mass triblock precursors will maintain an ordered morphology upon addition of the terminal PS' block due to stronger overall segregation strengths. These predictions were tested using three sets of SILS' polymers that were synthesized based on three precursor SIL triblock polymers differing in total molar mass (14, 30, and 47 kg mol^-1) and varying the length of the terminal PS' chain. In the lowest-molar-mass set of tetrablock polymers, the shift from order to disorder was observed in the materials at ambient temperature as the molar mass of the terminal PS' block was increased, consistent with SCFT calculations. Disorder with longer S' chain lengths was not found in the two higher-molar-mass polymer sets; the medium-molar-mass set showed both microphase separation and long-range order based on transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS), while the largest of these block polymers microphase separated but showed limited long-range order. The combination of the experimental and theoretical results presented in this work provides insights into the self-assembly of ABCA'-type polymers and highlights potential complications that arise from frustration in accessing well-ordered materials.

Periodic and Aperiodic Tiling Patterns from a Tetrablock Terpolymer System of the A1BA2C Type

Two tetrablock terpolymers of the S₁IS₂P type, where S, I, and P denote polystyrene, polyisoprene, and poly(2-vinylpyridine), respectively, were prepared anionically. S₁IS₂P-1 (S₁/I/S₂/P = 0.35/0.16/0.34/0.15, four numbers being volume fractions of S₁, I, S₂, and P block chains) has a structure with double hexagonal cylinders, while S₁IS₂P-2 (S₁/I/S₂/P = 0.47/0.15/0.22/0.16) has an unusual double tetragonal structure. Moreover, 13 binary blends were prepared from these two parent polymers. Among them, five blends with α(= φ_S1/φ_S2) covering the range 1.50 ≤ α ≤ 1.86 were confirmed to have a 3.3.4.3.4 Archimedean tiling structure, in which their P domains adopt five satellite I domains, while four blends with α covering the range 1.37 ≤ α ≤ 1.48 were revealed to be a quasicrystalline tiling structure with dodecagonal symmetry.

Morphology of symmetric ABCD tetrablock quaterpolymers studied by Monte Carlo simulation

Morphology of symmetric ABCD tetrablock quaterpolymers in melt was studied by the Monte Carlo (MC) simulation, where the volume fractions of the block chains, f, kept the relationships of f_A=f_D and f_B=f_C, and the volume fraction of the two mid-blocks φ was defined as φ=f_B+f_C. Previous self-consistent field theory for ABCD reported morphological change including several structures; however, the scope was limited within a two-dimensional system. To the contrary, in this paper, MC simulations were carried out in three dimensions with changing the φ value finely, which resulted in finding a tetracontinuous structure in the range of 0.625≤φ≤0.75. Moreover the tetracontinuous structure has been found to be the gyroid structure, and the mean curvature of the B/C interface is nearly zero. We concluded that the B/C interface must be the Schoen gyroid surface, one of three-dimensional periodic minimal surfaces. The geometrical nature of the A/B interface should be equivalent to that of the C/D interface, and they stand as level surfaces to the Schoen gyroid surface.

Synthesis of Tri- and Multiblock Polymers with Asymmetric Poly(ethylene oxide) End Blocks

We report the anionic synthesis of poly(ethylene oxide-b-isoprene-b-ethylene oxide) (OIO') triblock copolymers and poly(ethylene oxide-b-styrene-b-butadiene-b-ethylene oxide) (OSBO') tetrablock terpolymers with asymmetrically sized poly(ethylene oxide) (PEO) end blocks using triisopropylsilyloxy-1-propyllithium (TIPSOPrLi) as a protected initiator and diphenylmethyl potassium (DPMK) as the base activator for EO polymerization. All final products and precursors were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) techniques confirming monomodal and narrow molecular weight distributions and controlled molar masses. The growth of independently controlled PEO blocks was additionally demonstrated by the characterization of residual PEO blocks obtained from the ozonolysis of OIO'.