Browsing by Author "Epps, Thomas H. III"
Now showing 1 - 16 of 16
Results Per Page
Sort Options
Item Catch and release: photocleavable cationic diblock copolymers as a potential platform for nucleic acid delivery(Royal Society of Chemistry, 2014-06-05) Green, Matthew D.; Foster, Abbygail A.; Greco, Chad T.; Roy, Raghunath; Lehr, Rachel M.; Epps, Thomas H. III; Sullivan, Millicent O.; Matthew D. Green, Abbygail A. Foster, Chad T. Greco, Raghunath Roy, Rachel M. Lehr, Thomas H. Epps, III and Millicent O. Sullivan; Green, Matthew D.; Foster, Abbygail A.; Greco, Chad T.; Roy, Raghunath; Lehr, Rachel M.; Epps, Thomas H. III; Sullivan, Millicent O.Binding interactions between DNA and cationic nanocarriers must be sufficiently strong to prevent nuclease-mediated degradation, yet weak enough to permit transcription. We demonstrate cationic diblock copolymers containing PEG and o-nitrobenzyl moieties that facilitated tailorable DNA complexation and light-activated release. This design unlocks a new approach to improved non-viral gene packaging.Item Circularity in polymers: addressing performance and sustainability challenges using dynamic covalent chemistries(Chemical Science, 2023-05-05) Yan, Tianwei; Balzer, Alex H.; Herbert, Katie M.; Epps, Thomas H. III; Korley, LaShanda T. J.The circularity of current and future polymeric materials is a major focus of fundamental and applied research, as undesirable end-of-life outcomes and waste accumulation are global problems that impact our society. The recycling or repurposing of thermoplastics and thermosets is an attractive solution to these issues, yet both options are encumbered by poor property retention upon reuse, along with heterogeneities in common waste streams that limit property optimization. Dynamic covalent chemistry, when applied to polymeric materials, enables the targeted design of reversible bonds that can be tailored to specific reprocessing conditions to help address conventional recycling challenges. In this review, we highlight the key features of several dynamic covalent chemistries that can promote closed-loop recyclability and we discuss recent synthetic progress towards incorporating these chemistries into new polymers and existing commodity plastics. Next, we outline how dynamic covalent bonds and polymer network structure influence thermomechanical properties related to application and recyclability, with a focus on predictive physical models that describe network rearrangement. Finally, we examine the potential economic and environmental impacts of dynamic covalent polymeric materials in closed-loop processing using elements derived from techno-economic analysis and life-cycle assessment, including minimum selling prices and greenhouse gas emissions. Throughout each section, we discuss interdisciplinary obstacles that hinder the widespread adoption of dynamic polymers and present opportunities and new directions toward the realization of circularity in polymeric materials.Item Controlled ionic conductivity via tapered block polymer electrolytes(Royal Society of Chemistry, 2015-01-23) Kuan, Wei-Fan; Remy, Roddel; Mackay, Michael E.; Epps, Thomas H. III; Wei-Fan Kuan, Roddel Remy, Michael E. Mackay and Thomas H. Epps, III; Kuan, Wei-Fan; Remy, Roddel; Mackay, Michael E.; Epps, Thomas H. IIIWe present the design of novel solid electrolytes using tapered block polymers (TBPs). In this work, we synthesize a series of TBPs via atom transfer radical polymerization (ATRP) consisting of rigid polystyrene and ion-conducting poly(oligo-oxyethylene methacrylate) segments and explore the role of tapered interfaces on ion transport. Previous studies on TBPs have shown that manipulating the taper composition in block polymers can reduce the unfavorable polymer–polymer interactions between blocks, enabling the design for highly-processable (lower order–disorder transition temperature) polymer electrolytes. Herein, we demonstrate that the taper profile and taper volume fraction significantly impact the glass transition temperatures (Tgs) in block polymer electrolytes, thus affecting the ionic conductivity. Additionally, we find that the normal-tapered materials with z60 vol% tapering exhibit remarkable improvements in ionic conductivity (increase z190% at 20 C and increase z90% at 80 C) in comparison to their non-tapered counterparts. Overall, our TBPs, with controllable interfacial interactions, present an exciting opportunity for the fabrication of cost-effective, highly-efficient, and stable energy storage membranes.Item Determination of Lithium-Ion Distributions in Nanostructured Block Polymer Electrolyte Thin Films by X‑ray Photoelectron Spectroscopy Depth Profiling(American Chemical Society, 2014-12-19) Gilbert, Jonathan B.; Luo, Ming; Shelton, Cameron K.; Rubner, Michael F.; Cohen, Robert E.; Epps, Thomas H. III; Jonathan B. Gilbert, Ming Luo, Cameron K. Shelton, Michael F. Rubner, Robert E. Cohen, and Thomas H. Epps, III; Shelton, Cameron K.; Epps, Thomas H. III; Luo, MingX-ray photoelectron spectroscopy (XPS) depth profiling with C60 þ sputtering was used to resolve the lithium-ion distribution in the nanometer-scale domain structures of block polymer electrolyte thin films. The electrolytes of interest are mixtures of lithium trifluoromethanesulfonate and lamellar-forming polystyrene poly(oligo(oxyethylene)methacrylate) (PS POEM) copolymer. XPS depth profiling results showed that the lithium-ion concentration was directly correlated with the POEM concentration. Furthermore, chemical state and atomic composition of the film were analyzed through the deconvolution of the C1s signal, indicating that the lithium ions appear to be uniformly distributed in the POEM domains. Overall, the unique capabilities of C60 þ depth profiling XPS provide a powerful tool for the analysis of nanostructured polymer thin films in applications ranging from energy storage and generation to surface coatings and nanoscale templates.Item Electrophoretic Deposition as a Versatile Low-Cost Tool to Construct a Synthetic Polymeric Solid-Electrolyte Interphase on Silicon Anodes: A Model System Investigation(ACS Applied Materials and Interfaces, 2024-02-14) Mou, Rownak J.; Barua, Sattajit; Prasad, Ajay K.; Epps, Thomas H. III; Yao, Koffi P. C.The cycling of next-generation, high-capacity silicon (Si) anodes capable of 3579 mAh·g–1 is greatly hindered by the instability of the solid-electrolyte interphase (SEI). The large volume changes of Si during (de)lithiation cause continuous cracking of the SEI and its reconstruction, leading to loss of lithium inventory and extensive consumption of electrolyte. The SEI formed in situ during cell cycling is mostly composed of molecular fragments and oligomers, the structure of which is difficult to tailor. In contrast, ex situ formation of a synthetic SEI provides greater flexibility to deposit long-chain, polymeric, and elastomeric components potentially capable of maintaining integrity against the large ∼350% volume expansion of Si while also enabling electronic passivation of the surface for longer cycling and calendar life. Furthermore, polymers are amenable to structural modifications, and the desired elasticity can be targeted by selection of the SEI polymer feedstock. Herein, electrophoretic deposition (EPD) is used to apply chitosan as a synthetic SEI on model Si thin film electrodes. Comparison of synthetic SEIs obtained without (Si/Chit) and with CH3COOLi (Si/Chit+CH3COOLi) added during EPD is performed to demonstrate a facile route to tuning of the polymer SEI chemistry. Atomic force and scanning electron microscopy reveal that addition of CH3COOLi at EPD assists in conformal deposition of the synthetic SEI. During electrochemical cycling, the Chit+CH3COOLi coating nearly doubles the capacity retention versus the reference bare Si thin film. X-ray photoelectron and Fourier transform infrared spectroscopy reveal that CH3COOLi caps the −NH2 groups of chitosan through amidation during EPD, which suppresses the catalytic reduction of the electrolyte. The presented approach demonstrates and validates EPD as a low-capital route to achieving and chemistry-tuning synthetic SEIs on Si electrodes. More broadly, the method is a promising avenue toward controlled and tailored polymeric SEIs on various conversion-type electrodes with high particle volumetric expansion.Item Estrogenic activity of lignin-derivable alternatives to bisphenol A assessed via molecular docking simulations(RSC Advances, 2021-06-23) Amitrano, Alice; Mahajan, Jignesh S.; Korley, LaShanda T. J.; Epps, Thomas H. IIILignin-derivable bisphenols are potential alternatives to bisphenol A (BPA), a suspected endocrine disruptor; however, a greater understanding of structure–activity relationships (SARs) associated with such lignin-derivable building blocks is necessary to move replacement efforts forward. This study focuses on the prediction of bisphenol estrogenic activity (EA) to inform the design of potentially safer BPA alternatives. To achieve this goal, the binding affinities to estrogen receptor alpha (ERα) of lignin-derivable bisphenols were calculated via molecular docking simulations and correlated to median effective concentration (EC50) values using an empirical correlation curve created from known EC50 values and binding affinities of commercial (bis)phenols. Based on the correlation curve, lignin-derivable bisphenols with binding affinities weaker than ∼−6.0 kcal mol−1 were expected to exhibit no EA, and further analysis suggested that having two methoxy groups on an aromatic ring of the bio-derivable bisphenol was largely responsible for the reduction in binding to ERα. Such dimethoxy aromatics are readily sourced from the depolymerization of hardwood biomass. Additionally, bulkier substituents on the bridging carbon of lignin-bisphenols, like diethyl or dimethoxy, were shown to weaken binding to ERα. And, as the bio-derivable aromatics maintain major structural similarities to BPA, the resultant polymeric materials should possess comparable/equivalent thermal (e.g., glass transition temperatures, thermal decomposition temperatures) and mechanical (e.g., tensile strength, modulus) properties to those of polymers derived from BPA. Hence, the SARs established in this work can facilitate the development of sustainable polymers that maintain the performance of existing BPA-based materials while simultaneously reducing estrogenic potential.Item Ionic-Liquid-Mediated Deconstruction of Polymers for Advanced Recycling and Upcycling(ACS Macro Letters, 2023-08-15) Christoff-Tempesta, Ty; Epps, Thomas H. IIIIonic liquids (ILs) are a promising medium to assist in the advanced (chemical and biological) recycling of polymers, owing to their tunable catalytic activity, tailorable chemical functionality, low vapor pressures, and thermal stability. These unique physicochemical properties, combined with ILs’ capacity to solubilize plastics waste and biopolymers, offer routes to deconstruct polymers at reduced temperatures (and lower energy inputs) versus conventional bulk and solvent-based methods, while also minimizing unwanted side reactions. In this Viewpoint, we discuss the use of ILs as catalysts and mediators in advanced recycling, with an emphasis on chemical recycling, by examining the interplay between IL chemistry and deconstruction thermodynamics, deconstruction kinetics, IL recovery, and product recovery. We also consider several potential environmental benefits and concerns associated with employing ILs for advanced recycling over bulk- or solvent-mediated deconstruction techniques, such as reduced chemical escape by volatilization, decreased energy demands, toxicity, and environmental persistence. By analyzing IL-mediated polymer deconstruction across a breadth of macromolecular systems, we identify recent innovations, current challenges, and future opportunities in IL application toward circular polymer economies.Item A Life Cycle Greenhouse Gas Model of a Yellow Poplar Forest Residue Reductive Catalytic Fractionation Biorefinery(Environmental Engineering Science, 2022-09-13) Luo, Yuqing; O’Dea, Robert M.; Gupta, Yagya; Chang, Jeffrey; Sadula, Sunitha; Soh, Li Pei; Robbins, Allison M.; Levia, Delphis F.; Vlachos, Dionisios G.; Epps, Thomas H. III; Ierapetritou, MarianthiThe incentive to reduce greenhouse gas (GHG) emissions has motivated the development of lignocellulosic biomass conversion technologies, especially those associated with the carbohydrate fraction. However, improving the overall biomass valorization necessitates using lignin and understanding the impact of different tree parts (leaves, bark, twigs/branchlets) on the deconstruction of lignin, cellulose, and hemicellulose toward value-added products. In this work, we explore the production of chemicals from a yellow poplar-based integrated biorefinery. Yellow poplar (Liriodendron tulipifera L.) is an ideal candidate as a second-generation biomass feedstock, given that it is relatively widespread in the eastern United States. Herein, we evaluate and compare how the different proportions of cellulose, hemicellulose (xylan), and lignin among leaves, bark, and twigs/branchlets of yellow poplar, both individually and as a composite mix, influence the life-cycle GHG model of a yellow poplar biorefinery. For example, the processing GHG emissions were reduced by 1,110 kg carbon dioxide (CO2)-eq, 654 kg CO2-eq, and 849 kg CO2-eq per metric ton of twigs/branchlets, leaves, and bark, respectively. Finally, a sensitivity analysis illustrates the robustness of this biorefinery to uncertainties of the feedstock xylan/glucan ratio and carbon content.Item Metal oxide arrays from block copolymer thin film templates(Royal Society of Chemistry, 2015-03-02) Mayeda, Michael K.; Hayat, Jeffery; Epps, Thomas H. III; Lauterbach, Jochen; Michael K. Mayeda, Jeffery Hayat, Thomas H. Epps, III and Jochen Lauterbach; Mayeda, Michael K.; Epps, Thomas H. IIIWe present a simple, though uncommonly used, method to produce versatile, well-ordered, nanoscale arrays of metal oxides such as MgO, Al2O3, TiO2, MnO2, Fe2O3, Co3O4, NiO, CuO, ZnO, ZrO2, RuO2, SnO2, or Ce2 O3 by decoupling metal oxide precursor incorporation from block copolymer (BCP) template formation. In this work, neat BCP thin films were cast and annealed, using standard techniques, to generate templates. The templates were immersed in a precursor solution and formed metal– polymer complexes in one polymer domain. Finally, the organics were removed in an oxidative environment to leave the templated metal oxides. As a concrete example of the method's applicability, we show that the templating method produced ordered TiO2 arrays that exhibited a 13% increase in photocatalytic activity over TiO2 produced by EISA. Furthermore, the addition of gold nanoparticles further improved photocatalytic activity by 43% on our templated TiO2, whereas gold nanoparticles on EISA TiO2 exhibited no improvement. The simplicity and modularity of the templating method makes it amenable to additional applications in catalysis, optics, and sensors.Item Nanostructured Block Polymer Electrolytes: Tailoring Self-Assembly to Unlock the Potential in Lithium-Ion Batteries(Accounts of Chemical Research, 2021-12-07) Ketkar, Priyanka M.; Epps, Thomas H. IIIConspectus Ion-containing solid block polymer (BP) electrolytes can self-assemble into microphase-separated domains to facilitate the independent optimization of ion conduction and mechanical stability; this assembly behavior has the potential to improve the functionality and safety of lithium-ion batteries over liquid electrolytes to meet future demands (e.g., large capacities and long lifetimes) in various applications. However, significant enhancements in the ionic conductivity and processability of BPs must be realized for BP-based electrolytes to become robust alternatives in commercial devices. Toward this end, the controlled modification of BP electrolytes’ intra-domain (nanometer-scale) and multi-grain (micrometer-scale) structure is one viable approach; intra-domain ion transport and segmental compatibility (related to the effective Flory–Huggins parameter, χeff) can be increased by tuning the ion and monomer-segment distributions, and the morphology can be selected such that the multi-grain transport is less sensitive to grain size and orientation. To highlight the characteristics of intra-domain structure that promote efficient ion transport, this Account begins by describing the relationship between BP thermodynamics (namely, χeff and the statistical segment length, b, which is indicative of chain stiffness) and local ion concentration. These thermodynamic insights are vital because they inform the selection of synthesis and formulation variables, such as polymer and ion chemistry, polymer molecular weight and composition, and ion concentration, which boost electrolyte performance. In addition to its relationship with local ion transport, χeff is also an important factor with respect to electrolyte processability. For example, a reduced χeff can allow BP electrolytes to be processed at lower temperatures (i.e., lower energy input), with less solvent (i.e., reduced waste), and/or for shorter times (i.e., higher throughput) yet still form desired nanostructures. This Account also examines the impact of electrolyte preparation and processing on the ion transport across nanostructured grains because of grain size and orientation. As morphologies with a 3D-connected versus 2D-connected conducting phase show different sensitivities to conductivity losses that can occur because of the fabrication methods, it is necessary to account for electrolyte processing effects when probing ion transport. The intra-domain and micrometer-scale structure also can be tuned using either tapered BPs (macromolecules with modified monomer-segment composition profiles between two homogeneous blocks) or blends of BPs and homopolymers, independent of the BP molecular weight and composition, as detailed herein. The application of TBPs or BP/HP blends as ion-conducting materials leads to improved ion transport, reduced χeff, and greater availability of morphologies with 3D connectivity relative to traditional (non-tapered and unblended) BP electrolytes. This feature results from the fact that ion transport is related more closely to the monomer-segment distributions within a domain than the overall nanoscale morphology or average polymer/ion mobilities. Taken together, this Account describes how ion transport and processability are influenced by BP architecture and nanostructural features, and it provides avenues to tune nanoassemblies that can contribute to improved lithium-ion battery technologies to meet future demands.Item Oxidative Functionalization of Long-Chain Liquid Alkanes by Pulsed Plasma Discharges at Atmospheric Pressure(ACS Sustainable Chemistry and Engineering, 2022-11-17) Nguyen, Darien K.; Dimitrakellis, Panagiotis; Talley, Michael R.; O'Dea, Robert M.; Epps, Thomas H. III; Watson, Mary P.; Vlachos, Dionisios G.We introduce the oxidation of long aliphatic alkanes using non-thermal, atmospheric plasma processing as an eco-friendly route for organic synthesis. A pulsed dielectric barrier discharge in He/O2 gas mixtures was employed to functionalize n-octadecane. C18 secondary alcohols and ketones were the main products, with an optimal molar yield of ∼29.2%. Prolonged treatment resulted in the formation of dialcohols, diketones, and higher molecular weight oxygenates. Lighter hydrocarbon products and decarboxylation to CO2 were also observed at longer treatment times and higher power inputs. A maximum energy yield of 5.48 × 10–8 mol/J was achieved at short treatment times and high powers, associated with higher selectivity to primary oxygenates. Direct hydroxylation of alkyl radicals, as well as disproportionation reactions, are proposed as the main pathways to alcohols and ketones. The results hold promise for functionalizing long hydrocarbon molecules at ambient conditions using catalyst-free plasma discharges.Item PEG−Polypeptide Block Copolymers as pH-Responsive Endosome- Solubilizing Drug Nanocarriers(American Chemical Society, 2014-05-12) Quadir, Mohiuddin A.; Morton, Stephen W.; Deng, Zhou J.; Shopsowitz, Kevin E.; Murphy, Ryan P.; Epps, Thomas H. III; Hammond, Paula T.; Mohiuddin A. Quadir, Stephen W. Morton, Zhou J. Deng, Kevin E. Shopsowitz, Ryan P. Murphy, Thomas H. Epps, III, and Paula T. Hammond; Murphy, Ryan P.; Epps, Thomas H. IIIHerein we report the potential of click chemistry-modified polypeptide-based block copolymers for the facile fabrication of pH-sensitive nanoscale drug delivery systems. PEG−polypeptide copolymers with pendant amine chains were synthesized by combining N-carboxyanhydridebased ring-opening polymerization with post-functionalization using azide−alkyne cycloaddition. The synthesized block copolymers contain a polypeptide block with amine-functional side groups and were found to self-assemble into stable polymersomes and disassemble in a pH-responsive manner under a range of biologically relevant conditions. The selfassembly of these block copolymers yields nanometer-scale vesicular structures that are able to encapsulate hydrophilic cytotoxic agents like doxorubicin at physiological pH but that fall apart spontaneously at endosomal pH levels after cellular uptake. When drug-encapsulated copolymer assemblies were delivered systemically, significant levels of tumor accumulation were achieved, with efficacy against the triple-negative breast cancer cell line, MDA-MB-468, and suppression of tumor growth in an in vivo mouse model.Item RAFT polymerization and associated reactivity ratios of methacrylate-functionalized mixed bio-oil constituents(Royal Society of Chemsitry, 2015-04-22) Holmberg, Angela L.; Karavolias, Michael G.; Epps, Thomas H. III; Angela L. Holmberg, Michael G. Karavolias and Thomas H. Epps, III; Holmberg, Angela L.; Karavolias, Michael G.; Epps, Thomas H. IIIThis work features a new suite of correlations for estimating kinetic parameters from multicomponent reversible addition–fragmentation chain-transfer (RAFT) polymerizations and an improved methodology for determining reactivity ratios in the pursuit of cost-effective and renewable plastics prepared from moderately processed bio-oils. Select monomers representing possible derivatives of compounds found in renewable bio-oils, such as pyrolyzed Kraft lignin and vegetable oils, were polymerized to investigate the consequences of structural diversity on the kinetics of RAFT polymerization. To facilitate predictions of heteropolymer dispersities and molecular weights, apparent chain-transfer coefficients (Capptr's) and propagation rate constants (kappp's) from homopolymerizations were correlated to kinetic parameters associated with the polymerization of bio-oil mixtures. Capptr depended on the reactivity ratios of the bio-oil components and the composition of the bio-oil feed, whereas kappp was related to only the composition of the bio-oil feed. A modified approach for analyzing Mayo–Lewis plots resulted in more accurate reactivity ratios and with greater precision in comparison to conventional nonlinear fitting procedures and traditional linearization fitting methods, respectively. The measured compositional data readily mapped onto the predicted monomer distribution profiles in multicomponent polymers, confirming the validity of the improved method described herein to determine reactivity ratios. Altogether, this manuscript offers a strategy for improving the viability of biobased polymers, addressing two key factors: minimizing separations costs by polymerizing bio-oil mixtures and preventing batch-to-batch inconsistencies in polymer properties by applying a priori knowledge about the bio-oil constituents’ individual kinetic parameters.Item Synthesis and characterization of bicontinuous cubic poly(3,4-ethylene dioxythiophene) gyroid (PEDOT GYR) gels(Royal Society of Chemsitry, 2015-01-12) Cho, Whirang; Wu, Jinghang; Shim, Bong Sup; Kuan, Wei-Fan; Mastroianni, Sarah E.; Young, Wen-Shiue; Kuo, Chin-Chen; Epps, Thomas H. III; Martin, David C.; Whirang Cho, Jinghang Wu, Bong Sup Shim, Wei-Fan Kuan, Sarah E. Mastroianni, Wen-Shiue Young, Chin-Chen Kuo, Thomas H. Epps, III and David C. Martin; Cho, Whirang; Wu, Jinghang; Shim, Bong Sup; Kuan, Wei-Fan; Mastroianni, Sarah E.; Young, Wen-Shiue; Kuo, Chin-Chen; Epps, Thomas H. III; Martin, David C.We describe the synthesis and characterization of bicontinuous cubic poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer gels prepared within lyotropic cubic poly(oxyethylene)10 nonylphenol ether (NP-10) templates with Ia[3 with combining macron]d (gyroid, GYR) symmetry. The chemical polymerization of EDOT monomer in the hydrophobic channels of the NP-10 GYR phase was initiated by AgNO3, a mild oxidant that is activated when exposed to ultraviolet (UV) radiation. The morphology and physical properties of the resulting PEDOT gels were examined as a function of temperature and frequency using optical and electron microscopy, small-angle X-ray scattering (SAXS), dynamic mechanical spectroscopy, and electrochemical impedance spectroscopy (EIS). Microscopy and SAXS results showed that the PEDOT gels remained ordered and stable after the UV-initiated chemical polymerization, confirming the successful templated-synthesis of PEDOT in bicontinuous GYR nanostructures. In comparison to unpolymerized 3,4-ethylenedioxythiophene (EDOT) gel phases, the PEDOT structures had a higher storage modulus, presumably due to the formation of semi-rigid PEDOT-rich nanochannels. Additionally, the storage modulus (G′) for PEDOT gels decreased only modestly with increasing temperature, from ∼1.2 × 105 Pa (10 °C) to ∼7 × 104 Pa (40 °C), whereas G′ for the NP-10 and EDOT gels decreased dramatically, from ∼5.0 × 104 Pa (10 °C) to ∼1.5 × 102 Pa (40 °C). EIS revealed that the impedance of the PEDOT gels was smaller than the impedance of EDOT gels at both high frequencies (PEDOT ∼102 Ω and EDOT 2–3 × 104 Ω at 105 Hz) and low frequencies (PEDOT 103–105 Ω and EDOT ∼5 × 105 Ω at 10−1 Hz). These results indicated that PEDOT gels were highly ordered, mechanically stable and electrically conductive, and thus should be of interest for applications for which such properties are important, including low impedance and compliant coatings for biomedical electrodes.Item Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation(American Chemical Society, 2014-10-14) Murphy, Ryan P.; Kelley, Elizabeth G.; Rogers, Simon A.; Sullivan, Millicent O.; Epps, Thomas H. III; Ryan P. Murphy, Elizabeth G. Kelley, Simon A. Rogers, Millicent O. Sullivan, and Thomas H. Epps, III; Murphy, Ryan P.; Kelley, Elizabeth G.; Rogers, Simon A.; Sullivan, Millicent O.; Epps, Thomas H. IIIChain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene-b-ethylene oxide) or pure poly(butadiene-b-ethylene oxide-d4) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air–water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.Item Unlocking Circularity Through the Chemical Recycling and Upcycling of Lignin-Derivable Polymethacrylates(Macromolecules, 2023-11-22) Christoff-Tempesta, Ty; O’Dea, Robert M.; Epps, Thomas H. IIIThe synthesis of polymers from lignin-derivable compounds can replace petrochemical building blocks with a renewable feedstock. However, the end-of-life management of bioderivable, nonbiodegradable polymers remains an outstanding challenge. Herein, the chemical recycling and upcycling of two higher-glass-transition temperature (>100 °C), lignin-derivable polymethacrylates, poly(syringyl methacrylate) (PSM) and poly(guaiacyl methacrylate) (PGM), is reported. Neat PSM and PGM were thermally depolymerized to quantitative conversions, producing their constituent monomers at high yields and purity. The deconstruction atmosphere influenced the depolymerization reaction order, and depolymerization was thermodynamically favored in air over N2. Further, monomer bulkiness and volatility impacted depolymerization activation energies. Notably, bulk depolymerization of PSM and PGM was performed without solvent or catalyst to high polymer conversions (89–90 wt %) and monomer yields (86–90 mol %) without byproduct formation. The resultant monomers were then upcycled to narrow-dispersity polymers and phase-separated block polymers. The findings herein offer a pathway to material circularity for higher-performance, lignin-derivable polymethacrylates.