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Browsing by Subject "copolymerization"

Now showing 1 - 3 of 3
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    Supporting data for Impact of macromonomer molar mass and feed composition on branch distributions in model graft copolymerizations
    (2021-12-07) Zografos, Aristotelis; Lynd, Nathaniel A; Bates, Frank S; Hillmyer, Marc A; hillmyer@umn.edu; Hillmyer, Marc A; University of Minnesota, Department of Chemistry
    These files contain primary data along with associated output from instrumentation supporting all results reported in the referenced manuscript. Graft polymers are useful in a versatile range of material applications. Understanding how changes to the grafted architecture, such as the grafting density (z), the side-chain degree of polymerization (Nsc), and the backbone degree of polymerization (Nbb), affect polymer properties is critical for accurately tuning material performance. For graft-through copolymerizations, changes to Nsc and z are controlled by the macromonomer degree of polymerization (NMM) and initial fraction of the macromonomer in the feed (fMM0), respectively. We show that changes to these parameters can influence the copolymerization reactivity ratios and, in turn, impact the side-chain distribution along a graft polymer backbone. Poly((±)-lactide) macromonomers with NMM values as low as ca. 1 and as high as 72 were copolymerized with a small-molecule dimethyl ester norbornene comonomer over a range of fMM0 values (0.1 ≤ fMM0 ≤ 0.8) using ring opening metathesis polymerization (ROMP). Monomer conversion was determined using 1H nuclear magnetic resonance spectroscopy, and the data were fit using terminal and non-terminal copolymerization models. The results from this work provide essential information for manipulating Nsc and z, while maintaining synthetic control over the side-chain distribution for graft-through copolymerizations.
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    Supporting Data for Ring-Opening Copolymerizations of a CO2-derived δ-Valerolactone with ε-Caprolactone and L-Lactide
    (2024-05-30) Anderson, Ryan A; Fine, Rachel F; Rapagnani, Rachel M; Tonks, Ian A; itonks@umn.edu; Tonks, Ian; University of Minnesota, Tonks group
    These files contain primary data along with associated output from instrumentation supporting all results reported in Anderson et. al. Ring-Opening Copolymerizations of a CO2-derived δ-Valerolactone with ε-Caprolactone and L-Lactide. This work has expanded the synthetic polymer chemistry of the CO2-derived lactone EtVP through ring-opening co-polymerizations with ε-CL and LLA. Polymer properties and microstructures could be tuned through concurrent and se-quential copolymerization strategies, which led to the formation of either block, gradient, or random copolymers. ε-CL block copolymers resulted in semi-crystalline polymers regardless of the molar ratio employed. For LLA, copolymers remained amorphous, and mechanical testing showed improved elasticity relative to PLLA. Furthermore, ε-CL and LLA copolymers could be chemically recycled back to monomer utilizing Sn(Oct)2. While this work lays the foundation for EtVP-based copolymers, investigation into triblocks and other end-of-life options may further improve the potential ap-plications of these CO2-based (co)polymers.
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    Synthesis and Rheological Properties of Branched Polylactide
    (2023-08) Zografos, Aristotelis
    Plastics are essential to society but the current trends of their production, use, and end-of-use are not sustainable. This realization has created a push towards more circular approaches to plastics management and central to this is the transition away from petroleum-based feedstocks towards those that are biobased and inherently renewable. This shift not only relies on the development of new biobased polymers but also the expanded use of those currently available. Polylactide has found its place as a key material in the biobased plastics market and is projected to remain so for the foreseeable future. However, its use is hampered by its poor melt processability in extensional flows. The work in this dissertation has sought to better understand how the polymer architecture can improve this limitation. The research presented here describes the means of implementing PLA into an architecture with precision branching and the study of how controlled changes to the branching influences the melt flow behavior. The introduction to this dissertation overviews general concepts of extensional rheology and branched polymer dynamics, which are important to the research. Chapter 2 discusses how to create graft polymers of PLA and focuses on the effects of monomer size and feed composition on the copolymerization kinetics for a graft-through synthesis. Chapter 3 uses this chemistry to synthesize a library of model graft copolymers to study how changes to the architecture influence viscoelasticity in extensional and shear deformations. In Chapter 4, a new method for synthesizing H-shaped PLA homopolymers is presented and the associated rheological properties are compared to a linear analogue. Taken together, these works further the ability to synthesize polymers with controlled branching and broadens the understanding of how specific changes to the branching can influence the rheological melt behavior. These ideas can be leveraged to target materials with viscoelastic properties amenable to industrial processing flows so that they can be used for a broader variety of applications.