Browsing by Subject "Polymers"
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Item Charged Glycopolymer Materials for Epidermolysis Bullosa(2017-12) Boyle, WilliamImproved delivery of therapeutic nucleic acid payloads to cells could lead to dramatically improved clinical outcomes for patients suffering from genetic disorders. This work focuses on the use of a trehalose-containing cationic glycopolymer, termed Tr4, to transfect clinically relevant cell types. In particular, the development of gene delivery methods to improve the transfection of cell types associated with the skin disease epidermolysis bullosa are investigated. The sulfated glycosaminoglycan, heparin, is show to form ternary complexes with pDNA and Tr4 leading to dramatically increased transfection efficiency in primary fibroblasts, induced pluripotent stem cells, HepG2, and U87-MG cells. This increase is not caused by improved uptake, but instead appears to be driven by improved intracellular trafficking of polyplexes compared transfection without heparin. Increasing the size of the plasmid cargo from 4.7 kbp to a more therapeutically relevant 10 kbp leads to the complete loss of transfection efficiency in Tr4-heparin transfection of primary fibroblasts and a reduction in transfection efficiency in iPSCs. Co-transfecting with additives meant to increase nuclear localization of the pDNA recovers the efficiency lost by increasing the plasmid size. These techniques allowed for the development of function transfection methods in iPSCs delivering a synthetic transcription activator of collagen type VII. Finally, nanofiber mats containing chondroitin sulfate were developed to scavenge inflammatory molecules from wound exudate.Item Cost Estimate of B vs. C Grade Asphalt Binders(Minnesota Department of Transportation, 2023-06) Yan, Tianhao; Marasteanu, Mihai; Turos, Mugurel; Barman, Manik; Manickavasagan, Vishruthi; Chakraborty, ManikPolymer-modified binders (PMB) have been shown over the decades to improve the mechanical properties of asphalt mixtures compared to unmodified binders. Considering the higher initial cost of PMB, selecting the best alternative is very important, especially for local agencies given their limited budgets. A challenge in the materials selection process for low-volume roads is the limited information available, which could allow engineers to determine whether using PMB is cost-effective. In this research, we investigate the use of PG 58H-34 PMB binders (grade C) and PG58S-28 unmodified binders (grade B) for low volume roads in Minnesota. Historical pavement performance data are analyzed to compare the field performance of modified and unmodified mixtures. Laboratory experiments are performed to compare the low-temperature cracking properties of polymer-modified and unmodified binders and mixtures commonly used in Minnesota. Based on the experimental results, a lifecycle cost analysis (LCCA) is performed comparing the use of polymer-modified and unmodified binders for lowvolume roads in Minnesota. The results show that using PMBs for new construction is expected to extend the pavement service life by 6 years, and that using PMB is more cost-effective than using unmodified binders for low-traffic roads.Item Data supporting Laves Phase Field in a Diblock Copolymer Alloy(2022-04-06) Magruder, Benjamin R; Park, So Jung; Collanton, Ryan P; Bates, Frank S; Dorfman, Kevin D; dorfman@umn.edu; Dorfman, Kevin D; Dorfman Research Group - University of Minnesota Department of Chemical Engineering and Materials ScienceWe have used self-consistent field theory to predict a phase field in a blend of micelle-forming AB and B'C diblock polymers with different lengths and incompatible core blocks. The resulting paper was published in Macromolecules (doi.org/10.1021/acs.macromol.2c00346). The data were generated using the Fortran version of the open-source software PSCF (https://pscf.cems.umn.edu/). All input and output files from PSCF used to generate the data in the paper are included in this dataset, as well as the code used to process the data and generate the figures.Item Interactions of Ethylene Oxide-Propylene Oxide Block Copolymers with Lipid Bilayers(2019-08) Zhang, WenjiaNonionic poly(propylene oxide)-b-poly(ethylene oxide) (PPO-PEO) block copolymers, known as Pluronics or poloxamers, have been widely studied for their great potential in cell membrane stabilization and permeabilization due to their amphiphilicity and biocompatibility. A hydrophilic dominant commercial poloxamer P188 shows a reasonable stabilization effect in vivo on dystrophic muscle cell membranes. Despite recent advances made in this field, the structure-function relationships and the underlying mechanism of polymer protection are not fully understood. The goals of this dissertation are to understand the fundamental mechanism of polymer-membrane association and to further design effective polymers to improve the therapeutic approach of cell membrane stabilization for Duchenne muscular dystrophy. Herein, we developed a simple yet powerful method that enables the quantification of the relatively weak interactions between the copolymers and vesicular lipid bilayers based on distinct diffusivity of free and bound polymers, using pulsed-field-gradient NMR (PFG-NMR). This is the first quantitative study that systematically investigated polymer binding to lipid membranes in the literature to our knowledge, which provides direct evidence regarding how polymer structure and membrane composition and curvature dictate their interactions. With lab-synthesized PPO-PEO diblock analogs as complements to the commercial triblock poloxamers, we found that polymers with larger molecular weight and higher hydrophobicity result in stronger polymer-membrane association. Also, the lipid bilayer composition plays a critical role. Notably, polymer binding drops 10-fold in a universal fashion as cholesterol concentration in the bilayer increases from 0 to 30 mol.%. Switching the lipid headgroup from choline to glycerol significantly enhanced polymer binding. Additionally, polymer protection efficacy on liposomes against induced lipid peroxidation was assessed and compared with their stabilization efficacy in vitro and in vivo.Item Polymer Literature Review(Minnesota Department of Transportation, 1995-09) Stroup-Gardiner, Mary; Newcomb, David E.This report compiles a vast majority of research on polymer modified asphalt cements and mixtures. It covers a general discussion of polymer chemistry and terns typically used by polymer suppliers; asphalt cement chemistry; typical test methods historically used to evaluate modified asphalts; reported results; comparisons of polymer rnodified asphalt cements and mixtures; proposed binder specifications; and a summary of field trials reported in the literature. Based on this information, the report suggests several experimental designs for use in the completion of the laboratory and field trial phases of this project.Item Semifluorinated Polymers and Hydrophilic High Capacity Ion-Exchangers as Ion-Sensing Membranes for Measurements in Harsh Sample Conditions(2016-01) Carey, JesseThe research presented in this thesis is focused on the development and use of ion-selective electrodes (ISEs) in harsh conditions, such as measurements in organic solvents, biological media, and samples containing lipophilic ions and at high temperatures. This thesis focuses on the study of two classes of ISE membranes to overcome challenges presented by these conditions, semifluorinated polymer membranes and hydrophilic high capacity ion-exchanger (HHCIE) membranes. First, a brief overview of the working mechanism and components of ISEs, as well as the problems caused by harsh sample conditions is given. Also, included is a discussion on fluorous membrane ISEs, which show resistance to biofouling, HHCIE membranes and polymer background relevant to ISEs. Semifluorinated polymers were synthesized by attachment of fluorinated side chains to the lipophilic polymer, poly(4-vinylphenol). However, the percent conversions of these reactions are not high enough to produce polymers that are suitable for use as ISE membranes. Several semifluorinated monomers were synthesized, polymerized into semifluorinated polymers and then fabricated into ISEs. These electrodes can utilize both fluorophilic and lipophilic ionophores, allowing for a wider range of possible analyte ions then previously available to fluorous membrane ISEs. Ion-exchanger electrodes made from these polymers show a wide selectivity rage, up to 14 orders of magnitude. Study of HHCIE membranes found them to be highly resistant to the effect of Donnan failure (co-ion interference). HHCIE membranes were used to make a sensor that could monitor the concentration of NOX- species in situ during nanoparticle synthesis reactions at 150 ºC in propylene glycol. It is also shown that nitrate ions present in this reaction are reduced to nitrite. A current pulse reference electrode with a HHCIE membrane was developed which should have advantages over similar electrodes made with lipophilic membranes when measuring in biological media.Item Structure and mechanical properties of elastomeric block copolymers.(2010-12) Alfonzo, Carlos GuillermoThis research presents the synthesis (by anionic polymerization and catalytic hydrogenation) and characterization of two types of block copolymers: CMC and XPX. In CMC, C is glassy poly(cyclohexylethylene) and M, the matrix, can be semicrystalline poly(ethylene) E, rubbery poly(ethylene-alt-propylene) P, or rubbery poly(ethylethylene) EE, or a combination to yield: CPC, CEEC, CEC, CPEEC and CEPC, with fC ≈ 0.18 – 0.30. XPX materials have X = CEC, fC ≈ fE, and fP ≈ 0.40 – 0.60. Block copolymer phase behavior and morphology were examined through a combination of DSC, rheology, SAXS, WAXS and TEM. CMC materials are meltordered due to block thermodynamic incompatibility with TODT > Tg (C) ≈ 147 °C and show lamellar or C cylinder morphologies. The design of XPX yields melt disordered materials up to high Mn with microphase segregation induced by E crystallization. Two high Mn XPX polymers are melt ordered above Tm(E) and show two correlation lengths in SAXS assigned to the C – E and X – P length scales. TEM images indicate that all XPX materials, irrespective of melt segregation, are characterized by composite glassy and crystalline hard domains dispersed in rubbery P at room temperature. Tensile and recovery testing at room temperature show that CMC and XPX materials, with the exception of plastic CEC, behave as thermoplastic elastomers with tunable properties. Interestingly, melt disordered XPX materials have competitive mechanical properties comparable to the strongest CMC polymers, but with advantageous processing. For melt ordered CMC, Tprocess > TODT, which is dependent on Mn, while for melt disordered XPX, Tprocess > Tm(E) ≈ 100 °C independent of Mn. The deformation of melt disordered XPX materials, probed by recovery studies and WAXS, suggests that deformation is first taken by P, then E and finally C, which causes ultimate failure, as agreed in the literature for conventional SBS and SIS thermoplastic elastomers. This implies that strain recovery in XPX materials can be comparable to that of CPC if materials contain low hard block content or are stretched to strains below the onset of E deformation. Finally, a collection of data of mechanical properties, namely modulus E, strain at break εb, tensile strength σTS and tension set εs, obtained from CMC, XPX and previously reported materials were examined. Most notably, E and εs were found to be strongly correlated with the volume fractions of C and E, as properties increase with (fC + fE)δ, where δ = 1 – 2.4. Ultimate properties such as σTS and εs are unaffected by changes in composition as failure is dictated by that of the hard domains and values are similar above a minimum amount of hard block. In addition, E, σTS, and εb are inversely correlated to rubber entanglement molecular weight Me, which implies that modulus and ultimate properties are affected by the ability of the rubber network to redistribute stress by entanglement slippage. However, εs is unresponsive to Me variations, which indicates that irrecoverable deformation in these materials results from deformation of the hard domains.Item Studies in Sustainable Polymers: Strategies for Feedstock Incorporation and Enhanced Polymer Si–O Bond Cleavage(2022-09) Gormong, EthanThe development of sustainable polymers is a significant undertaking and is best accomplished using a wide variety of complimentary techniques and chemical approaches. The body of work put forth by the NSF Center for Sustainable Polymers embodies this style of collaborative research, aspects of which will be summarized in Chapter 1. A promising avenue toward sustainable polymers is the development of new monomers derived from renewable carbohydrate resources (Chapter 2). The isohexides, including isosorbide, isomannide, and isoidide, can be readily converted into their corresponding bis-propargyl ethers, which can be polymerized using Cu(I) and Ni(II) catalysts. The resulting diyne polymers can be readily converted to their saturated polyether analogs by catalytic hydrogenation. Sustainable polymers are an excellent avenue to excite the next generation of scientists through chemistry laboratory curriculum. Dibutyl itaconate and -myrcene were copolymerized using two different reaction conditions to produce two polymeric materials with vastly different physical properties, suitable for student analysis (Chapter 3). The introduction of degradable linkages into commercial but environmentally persistent polymers, such as silicones, could be an important step toward sustainability. Though usually robust, the Si–O bonds in the polymer backbone can be activated toward cleavage by the introduction of tethered basic functional groups such as dimethyl amides and amines. The effect of tether length of the cleavage of the alkoxydisiloxanes was studied experimentally by 1H NMR analysis of small-molecule analogs and by computation (Chapter 4). These small-molecule findings are currently being applied to other classes of Si–O bonds (carbodisiloxanes) and to macromolecular systems in ongoing research efforts (Chapter 5).Item Sustainable Polymer Framework(2020-02) Wissinger, Jane E.; Ellison, Christopher J.; Dichtel, William R.; Chang, Alice B.; Trotta, Jacob T.; Yang, Anna B.; Bunyard, Clayton W.The Sustainable Polymer Framework seeks to holistically define a sustainable polymer. The intended use is for members of the NSF Center for Sustainable Polymers to be able to identify and explain how their individual research project meets this definition. The goal is to introduce an integrated systems-thinking approach that considers the interconnection of all criteria and their net impact across the environment, economy, and society.