Browsing by Subject "block copolymers"

Now showing 1 - 6 of 6
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    Data for "Stability of Cubic Single Network Phases in Diblock Copolymer Melts"
    (2022-07-25) Chen, Pengyu; Mahanthappa, Mahesh K; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D; Dorfman Research Group
    This dataset contains the self-consistent field theory (SCFT) simulation results and data for geometric analysis in "Stability of cubic single networks in diblock copolymer melts" by Chen et. al. (DOI: 10.1002/pol.20220318). SCFT was used to investigate the stability of cubic single and double network phases. Geometric analysis, including the calculations of mean curvatures and interfacial areas per unit volume of the domain interface, was used to understand the metastability of the single network phases. With this dataset, users should be able to regenerate the calculations and figures that appeared in the paper.
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    Data for Combining photocontrolled-cationic and anionic-group transfer polymerizations using a universal mediator: enabling access to two- and three-Mechanism block copolymers
    (2024-08-15) Hosford, Brandon M; Ramos, William; Lamb, Jessica R; jrlamb@umn.edu; Lamb, Jessica R; Lamb Research Group
    An ongoing challenge in polymer chemistry is accessing diverse block copolymers from multiple polymerization mechanisms and monomer classes. One strategy to accomplish this goal without intermediate compatibilization steps is the use of universal mediators. Thiocarbonyl thio (TCT) functional groups are well-known mediators to combine radical with either cationic or anionic polymerization, but a sequential cationic-anionic universal mediator system has never been reported. Herein, we report a TCT universal mediator that can sequentially perform photocontrolled cationic polymerization and thioacyl anionic group transfer polymerization to access poly(ethyl vinyl ether)-block-poly(thiirane) polymers for the first time. Thermal analyses of these block copolymers provide evidence of microphase separation. The success of this system, along with the established compatibility of radical polymerization, enabled us to further chain extend the cationic-anionic diblock using radical polymerization of N-isopropylacrylamide. The resulting terpolymer represents the first example of a triblock made from three different monomer classes incorporated via three different mechanisms without any end-group modification steps. The development of this simple, sequential synthesis using a universal mediator approach opens up new possibilities by providing facile access to diverse block copolymers of vinyl ethers, thiiranes, and acrylamides.
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    Physical and Biochemical Strategies for Improving the Yield and Material Properties of Polyhydroxyalkanoate Biopolymers
    (2014-10) Barrett, John
    Polyhydroxyalkanoates (PHAs) are a diverse class of microbially synthesized biopolymers that are valued for their synthesis from renewable feedstocks and rapid biodegradation. As such, the commercial development of PHA plastics has potential to reduce the environmental impact of many, current polymers, which are non-biodegradable and rely on the use of unsustainable petroleum feedstocks. But despite the desirable traits of PHAs, the proliferation of these materials into commercial markets remains slow. Part of this is due to the greater cost of the renewable substrates used for PHA production versus the artificially low cost of petroleum-derived feedstocks. The other part of the challenge of promoting PHA utilization owes to the relatively limited diversity of physical and mechanical properties of PHAs that are currently available. As such, additional work is needed to develop new PHAs, which can satisfy the performance characteristics of many polymers already in use. Motivated by these two main challenges, 1.) to lower the production cost of PHAs and 2.) to broaden the range of unique PHAs materials available, the thesis presented herein details the development of new technologies to increase the substrate-to-product yield of PHA production and to expand the range of physical and mechanical properties of PHA-based materials. Chapter1 gives a broad introduction to polyhydroxyalkanoates and discuss various aspects of their production and application. Chapter 2 highlights the value of block-copolymers as a rich source for scientific discovery and technological development of PHAs. Methods are detailed in Chapter 3. The experimental results are presented in Chapters 4, 5, and 6, which focus generally upon: 4.) production of PHA copolymers in recombinant E. coli , 5.) fabrication and testing of PHA-graphene nanocomposites and 6.) production of PHA copolymers and block-copolymers directly from CO2 using Ralstonia eutropha. Finally, conclusions and prospects for future PHA research and development are given in Chapter 7. Taken all together, this thesis provides a solid foundation in theory and practice, for several technological approaches, which have great potential
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    Renewable polymer materials from bicyclic sugar derivatives
    (2016-05) Gallagher, James
    Sugar derivatives are excellent candidates for the building blocks of biobased plastics. This thesis focuses on the preparation of new monomers derived from bicyclic sugar derivatives and the polymerization thereof to afford useful polymer materials. The first area of research presented is the preparation of two new monovinyl monomers acetylated methacrylic isosorbide and acetylated acrylic isosorbide (AMI and AAI). PAMI and PAAI prepared by radical polymerization of were found to have high Tg and good thermal stability. Reversible Addition Fragmentation chain Transfer polymerization was used to prepare PAMI and PAAI block copolymer samples with low Tg polyacrylates. These block copolymers were investigated as pressure sensitive adhesives and were found to exhibit desirable adhesive properties consistent with high shear removable pressure sensitive adhesives. The second area of research focuses on the synthesis and polymerization of two new dimethacrylate monomers from glucarodilactone and mannarodilactone (GDMA and MDMA). Thermally initiated free radical polymerization of these monomers in the bulk afforded highly crosslinked and rigid thermoset materials. Tensile testing of PGDMA demonstrated mechanical properties similar to those reported for commercially available poly(dimethacrylates) from rigid monomers. PGDMA was found to degrade to water-soluble components after 17 days in the presence of base, but remained stable under acidic and neutral conditions. Applications investigated were P(GDMA-co-MDMA) coatings and copolymer microspheres from GDMA and methyl methacrylate.
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    Rheological Design of Sustainable Block Copolymers
    (2016-08) Mannion, Alexander
    Block copolymers are extremely versatile materials that microphase separate to give rise to a rich array of complex behavior, making them the ideal platform for the development of rheologically sophisticated soft matter. In line with growing environmental concerns of conventional plastics from petroleum feedstocks, this work focuses on the rheological design of sustainable block copolymers - those derived from renewable sources and are degradable - based on poly(lactide). Although commercially viable, poly(lactide) has a number of inherent deficiencies that result in a host of challenges that require both creative and practical solutions that are cost-effective and amenable to large-scale production. Specifically, this dissertation looks at applications in which both shear and extensional rheology dictate performance attributes, namely chewing gum, pressure-sensitive adhesives, and polymers for blown film extrusion. Structure-property relationships in the context of block polymer architecture, polymer composition, morphology, and branching are explored in depth. The basic principles and fundamental findings presented in this thesis are applicable to a broader range of substances that incorporate block copolymers for which rheology plays a pivotal role.
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    Structure and Thermodynamics of Neutral and Charged Block Copolymer-Based Materials
    (2022-08) Zhang, Bo
    Next-generation materials are often required to exhibit two (or more) orthogonal properties simultaneously. One example is polymer electrolytes, as both facile ion transport and mechanical robustness are desired. However, these orthogonal properties are hard to achieve in single-component systems, because ion transport usually requires high chain mobility while high chain rigidity or low chain mobility is desired for mechanical stability. One way to overcome this challenge is to develop co-continuous nanostructured materials, such that one domain provides ion transport while the other imparts mechanical robustness. A promising predictable and tunable co-continuous structure is the bicontinuous microemulsion from ternary blends of an AB diblock copolymer and the corresponding A and B homopolymers. However, the structure and thermodynamics of such ternary mixtures are not fully elucidated, even in the limit of neutral ternary blends. Moreover, little is known about ion-containing ternary blends. Therefore, the focus of this thesis work is to understand the fundamental phase behavior of these systems and to ultimately provide insight into the rational design of functional materials. In Chapter 2, we investigate the phase behavior of neutral ternary blends comprising a linear diblock copolymer and the corresponding homopolymers. The impacts of block copolymer compositional asymmetry on ordered, disordered, and macrophase-separated regions of the ternary phase prism are discussed. In Chapter 3, we expand the research to ternary mixtures involving a bottlebrush diblock copolymer and the corresponding linear homopolymers. The overall phase behavior closely resembles that of linear ternary mixtures, except for an unconventional spatial distribution of the homopolymers. Chapters 4 and 5 focus on the self-assembly of charged diblock copolymers, serving as the starting point for the investigation of charged ternary blend phase behavior. Chapter 4 details the phase behavior of a series of symmetric charged diblock copolymers, where the effective interaction parameter was found to increase linearly with the increase in charge fraction. Chapter 5 extends the work to a different model system with a relatively nonpolar charged block. A tilted, “chimney”-like order-disorder transition boundary was observed. However, the composition windows of the ordered phases remain nearly unchanged. Overall, the findings from this thesis research provide valuable insight into the structure and thermodynamics of neutral and charged polymer mixtures, and will inform the rational design of nanostructured polymer electrolytes with tunable structure and properties.