Browsing by Subject "block polymers"

Now showing 1 - 7 of 7
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    Computational Study of Network Phase Formation in Self-Assembled Block Polymers
    (2024-08) Chen, Pengyu
    Mesoporous materials with multi-continuous networks are attracting widespread interest due to their potential applications in optical metamaterials, membrane separation, and catalysis. Block polymers, with their simple thermodynamic representation through self-consistent field theory (SCFT), provide an ideal model for examining the self-assembly behaviors in these networks. In this dissertation, we leverage SCFT to deepen our understanding of the thermodynamic principles that govern the formation ofthese complex network phases and to facilitate the discovery of new network phases. The investigation begins with an exploration of the metastability of cubic single networks via SCFT. Our findings reveal that larger interfacial areas per unit volume, resulting from lower chain-packing densities in the single networks, are a critical factor contributing to their metastability. This phenomenon is largely due to the specific positioning of chain configurations relative to the minimal surfaces. Furthermore, we utilize SCFT to validate the feasibility of using ternary polymer blends for fabricating alternating gyroids. By introducing a small amount of poly(isoprene-b-styrene-b-ethylene oxide) (ISO) triblock terpolymers into blends of double-gyroid-forming diblock copolymers, poly(isoprene-b-styrene) (IS) and poly(styrene-b-ethylene oxide) (SO), the alternating gyroid phase can be effectively stabilized. It is found that the formation of alternating gyroids is particularly sensitive to the asymmetry in thermodynamic parameters, and that matching the preferred domain sizes of the IS and SO diblocks enhances the stability of alternating gyroids. Finally, to overcome the limitations of conventional SCFT in predicting new morphologies, we integrate SCFT with a deep convolutional generative adversarial network (GAN) trained on SCFT density fields of known phases. This innovative approach allows the GAN to generate new input fields for subsequent SCFT calculations, resulting in a library of 349 candidate network phases. These phases cover both known networks and new networks with competitively low free energies, offering new directions for inverse materials design, property predictions, and structural determinations of self-assembled network phases. Overall, this dissertation advances our understanding of self-assembled network phases in block polymers and other soft matter systems, proposing new strategies for future research.
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    Data for Crystallinity-independent toughness in renewable poly(L-lactide) triblock plastics
    (2024-03-18) Krajovic, Daniel M; Haugstad, Greg; Hillmyer, Marc A; hillmyer@umn.edu; Hillmyer, Marc A; Hillmyer Research Group
    Poly(L-lactide) (PLLA)’s broad applicability is hindered by its brittleness and slow crystallization kinetics. Among the strategies for developing tough, thermally resilient PLLA-based materials, the utilization of neat PLLA block polymers has received comparatively little attention despite its attractive technological merits. In this work, we comprehensively describe the microstructural, thermal, and mechanical properties of two compositional libraries of PLLA-rich PLLA-b-poly(γ-methyl-ε-caprolactone) (PγMCL)-b-PLLA (“LML”) triblock copolymers. The rubbery PγMCL domains microphase separate from the matrix in the melt and intercalate between PLLA crystal lamellae on cooling. Despite the mobility constraints associated with mid-block tethering, the PLLA end-blocks crystallize as rapidly as a PLLA homopolymer control of similar molar mass. Independent of their degree of crystallinity, LML triblocks exhibit vastly improved tensile toughnesses (63-113 MJ m-3) over that of PLLA homopolymer (1.3-2 MJ m-3), with crystallinities of up to 55% and heat distortion temperatures (HDTs) as high as 148 °C. We investigated the microstructural origins of this appealing performance using X-ray scattering and microscopy. In the case of a largely amorphous PLLA matrix, the PγMCL domains cavitate to enable concurrent PLLA shear yielding and strain-induced crystallization. In highly crystalline PLLA matrices, PγMCL facilitates a lamellar-to-fibrillar transition during tensile deformation, the first such transition reported for PLLA drawn at room temperature. These results highlight the unique attributes of PLLA block polymers and prompt future architectural and processing optimizations to achieve ultratough, high-HDT PLLA block polymer plastics after a simple thermal history on economical timescales.
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    Data for Gaming self-consistent field theory: Generative block polymer phase discovery
    (2023-10-18) Chen, Pengyu; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D; Dorfman Research Group - University of Minnesota Department of Chemical Engineering and Materials Science
    This dataset contains the input and output files for self-consistent field theory (SCFT) simulations and the training of generative adversarial networks (GANs) in the associated paper.
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    Data supporting Interfacial geometry in particle-forming phases of diblock copolymers
    (2022-01-19) Collanton, Ryan P; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D
    Frank-Kasper phases are complex particle packings known to form in a wide variety of hard and soft materials, including single-component AB diblock copolymer melts. An important open question in the context of this system is why these lower-symmetry packings are selected over the classical, higher-symmetry, body-centered cubic phase. To address this question, we simulated a library of diblock copolymer melts under intermediate-segregation conditions using self-consistent field theory and performed a combination of geometric and thermodynamic analyses. Our findings show that imprinting of the enclosing Voronoi polyhedra onto the micelle core is generally weak, but nonetheless coincides with sharpening of the interface between A and B monomers compared to more spherical cores. The corresponding reduction in enthalpy, which is the dominant contribution to the free energy, drives the bcc-σ transition, overcoming increases in stretching penalties and giving way to more polyhedral micelle cores. These results offer insight into the stability and formation of Frank-Kasper phases under experimentally realistic conditions.
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    High Performance Materials from Renewable Aliphatic Polyesters
    (2016-08) Schneiderman, Deborah
    Although synthetic polymers are essential to our society, their manufacture and disposal can be damaging to the environment. This dissertation is concerned with the development of new high performance sustainable polymers for a wide variety of applications. The first chapter gives a brief overview of the polymer industry and introduces past work in arena of sustainable polymers with a particular focus on poly(lactide). The remaining chapters discuss my research efforts to expand on earlier work to toughen poly(lactide) using a block polymer approach. Described first is the syntheses of renewable and degradable aliphatic polyester copolymers polyols containing ε-caprolactone. These statistical copolymers are used as building blocks to prepare mechanically tunable triblock and multiblock materials (Chapter 2). Following this, an efficient semisynthetic route to a branched lactone monomer, MVL, is presented and discussed. The potential of this monomer for the synthesis of block polymer and polyurethane materials is explored (Chapters 3 and 5, respectively). A large portion of each of these chapters is dedicated to exploring the relationship between aliphatic polyester structure and key physical parameters that influence material performance (summarized in Chapter 4).
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    Supporting Data for "From Order to Disorder: Computational Design of Triblock Amphiphiles with 1 nm Domains"
    (2020-07-06) Shen, Zhengyuan; Chen, Jingyi L; Vernadskaia, Viktoriia; Ertem, S Piril; Mahanthappa, Mahesh K; Hillmyer, Marc A; Reineke, Theresa M; Lodge, Timothy P; Siepmann, J Ilja; siepmann@umn.edu; Siepmann, J Ilja; Materials Research Science & Engineering Center (MRSEC)
    Data including input/output and restart files for all the systems, analysis codes (python, fortran, cpp), and figures in the paper "From Order to Disorder: Computational Design of Triblock Amphiphiles with 1 nm Domains." Sample molecular dynamics trajectories pieces are provided due to the extremely long simulation trajectories.
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    Unraveling Structure-Property Relationships in Polymer Blends for Intelligent Materials Design
    (2016) Irwin, Matthew
    Block polymers provide an accessible route to structured, composite materials by combining two or more components with disparate mechanical, chemical, and electrical properties into a single bulk material with nanoscale domains. However, the characteristic lengthscale of these systems is limited, and the choice of components is restricted to those that are able to undergo microstructural ordering at accessible temperatures. This thesis details routes to overcoming these limitations through the addition of a lithium salt, a blend of homopolymers, or both. Chapter 2 describes a study wherein complex sphere phases such as the Frank-Kasper sigma phase can be observed in otherwise disordered asymmetric block polymers through the addition of a lithium salt. Chapter 3 discusses the development and characterization of a ternary polymer blend of an AB diblock copolymer and A and B homopolymers doped with a lithium salt. Detailed characterization showed that doping blends that are otherwise disordered with lithium salt induced microstructural ordering and largely recovers the phase behavior of traditional ternary polymer blends. A systematic study of the ionic conductivity of the blends at a fixed salt concentration demonstrates that, at a given composition, disordered, yet highly structured blends consistently exhibit better conductivity than polycrystalline morphologies with long range order. Chapter 4 extends the methodology of Chapter 3 and details a systematic study of the effects of cross-linker concentration on the performance of polymer electrolyte membranes produced via polymerization-induced microphase separation that exhibit a highly structured, globally disordered microstructure. Finally, Chapter 5 details efforts to develop a water filtration membrane using a polyethylene template derived from a polymeric bicontinuous microemulsion. Throughout all of this work, the goal is to better understand structure-property relationships at the molecular level in order to ultimately inform design criteria for materials where simultaneous control over morphology and mechanical, chemical, or electrical properties is important.