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1.
Food Chem Toxicol ; 190: 114787, 2024 Jun 03.
Article in English | MEDLINE | ID: mdl-38838754

ABSTRACT

Lignin-derivable bisguaiacols/bissyringols are viable alternatives to commercial bisphenols; however, many bisguaiacols/bissyringols (e.g., bisguaiacol F [BGF]) have unsubstituted bridging carbons between the aromatic rings, making them more structurally similar to bisphenol F (BPF) than bisphenol A (BPA) - both of which are suspected endocrine disruptors. Herein, we investigated the estrogenic activity (EA) and developmental toxicity of dimethyl-substituted bridging carbon-based lignin-derivable bisphenols (bisguaiacol A [BGA] and bissyringol A [BSA]). Notably, BSA showed undetectable EA at seven test concentrations (from 10-12 M to 10-6 M) in the MCF-7 cell proliferation assay, whereas BPA had detectable EA at five concentrations (from 10-10 M to 10-6 M). In silico results indicated that BSA had the lowest binding affinity with estrogen receptors. Moreover, in vivo chicken embryonic assay results revealed that lignin-derivable monomers had minimal developmental toxicity vs. BPA at environmentally relevant test concentrations (8.7-116 µg/kg). Additionally, all lignin-derivable compounds showed significantly lower expression fold changes (from ∼1.81 to ∼4.41) in chicken fetal liver tests for an estrogen-response gene (apolipoprotein II) in comparison to BPA (fold change of ∼11.51), which was indicative of significantly reduced estrogenic response. Altogether, the methoxy substituents on lignin-derivable bisphenols appeared to be a positive factor in reducing the EA of BPA alternatives.

2.
ChemSusChem ; : e202400238, 2024 Apr 12.
Article in English | MEDLINE | ID: mdl-38609332

ABSTRACT

The hydrogenolysis of polymers is emerging as a promising approach to deconstruct plastic waste into valuable chemicals. Yet, the complexity of plastic waste, including multilayer packaging, is a significant barrier to handling realistic waste streams. Herein, we reveal fundamental insights into a new chemical route for transforming a previously unaddressed fraction of plastic waste - poly(ethylene-co-vinyl alcohol) (EVOH) and related polymer blends - into alkane products. We report that Ru/ZrO2 is active for the concurrent hydrogenolysis, hydrogenation, and hydrodeoxygenation of EVOH and its thermal degradation products into alkanes (C1-C35) and water. Detailed reaction data, product analysis, and catalyst characterization reveal that the in-situ thermal degradation of EVOH forms aromatic intermediates that are detrimental to catalytic activity. Increased hydrogen pressure promotes hydrogenation of these aromatics, preventing catalyst deactivation and improving alkane product yields. Calculated apparent rates of C-C scission reveal that the hydrogenolysis of EVOH is slower than low-density polyethylene. We apply these findings to achieve hydrogenolysis of EVOH/polyethylene blends and elucidate the sensitivity of hydrogenolysis catalysts to such blends. Overall, we demonstrate progress towards efficient catalytic processes for the hydroconversion of waste multilayer film plastic packaging into valuable products.

3.
JACS Au ; 4(4): 1471-1479, 2024 Apr 22.
Article in English | MEDLINE | ID: mdl-38665666

ABSTRACT

We report a depolymerization strategy to nearly quantitatively regenerate isocyanates from thermoplastic and thermoset polyurethanes (PUs) and then resynthesize PUs using the recovered isocyanates. To date, chemical/advanced recycling of PUs has focused primarily on the recovery of polyols and diamines under comparatively harsh conditions (e.g., high pressure and temperature), and the recovery of isocyanates has been difficult. Our approach leverages an organoboron Lewis acid to depolymerize PUs directly to isocyanates under mild conditions (e.g., ∼80 °C in toluene) without the need for phosgene or other harsh reagents, and we show that both laboratory-synthesized and commercially sourced PUs can be depolymerized. Furthermore, we demonstrate the utility of the recovered isocyanate in the production of second-generation PUs with thermal properties and molecular weights similar to those of the virgin PUs. Overall, this route uniquely provides an opportunity for circularity in PU materials and can add significant value to end-of-life PU products.

4.
ACS Appl Mater Interfaces ; 16(11): 13399-13410, 2024 Mar 20.
Article in English | MEDLINE | ID: mdl-38466900

ABSTRACT

Although lipid nanoparticles (LNPs) are the predominant nanocarriers for short-interfering RNA (siRNA) delivery, most therapies use nearly identical formulations that have taken 30 years to design but lack the diverse property ranges necessary for versatile application. This dearth in variety and the extended timeline for implementation are attributed to a limited understanding of how LNP properties facilitate overcoming biological barriers. Herein, a simple kinetic model was developed by using major rate-limiting steps for siRNA delivery, and this model enabled the identification of a critical parameter to predict LNP efficacy without extensive experimental testing. A volume-averaged log D, the "solubility" of charged molecules as a function of pH weighted by component volume fractions, resulted in a good correlation between LNP composition and siRNA delivery. Both the effects of modifying the structures of ionizable lipids and LNP composition on gene silencing were easily captured in the model predictions. Thus, this approach provides a robust LNP structure-activity relationship to dramatically accelerate the realization of effective LNP formulations.


Subject(s)
Lipids , Nanoparticles , Lipids/chemistry , Liposomes , RNA, Small Interfering/chemistry , Nanoparticles/chemistry
5.
ACS Appl Mater Interfaces ; 16(6): 6908-6919, 2024 Feb 14.
Article in English | MEDLINE | ID: mdl-38305735

ABSTRACT

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.

6.
J Chem Phys ; 160(2)2024 Jan 14.
Article in English | MEDLINE | ID: mdl-38214386

ABSTRACT

Understanding polymer transport in nanopores is crucial for optimizing heterogeneously catalyzed processes in polymer upcycling and fabricating high-performance nanocomposite films and membranes. Although confined polymer dynamics have been extensively studied, the behavior of polyethylene (PE)-the most widely used commodity polymer-in pores smaller than 20 nm remains largely unexplored. We investigate the effects of extreme nanoconfinement on PE transport using capillary rise infiltration in silica nanoparticle packings with average pore radii ranging from ∼1 to ∼9 nm. Using in situ ellipsometry and the Lucas-Washburn model, we discover a previously unknown inverse relationship between effective viscosity (ηeff) and average pore radius (Rpore). Additonally, we determine that PE transport under these extreme conditions is primarily governed by physical confinement, rather than pore surface chemistry. We refine an existing theory to provide a generalized formalism to describe the polymer transport dynamics over a wide range of pore radii (from 1 nm and larger). Our results offer valuable insights for optimizing catalyst supports in polymer upcycling and improving infiltration processes for nanocomposite fabrication.

7.
ACS Macro Lett ; 12(8): 1058-1070, 2023 Aug 15.
Article in English | MEDLINE | ID: mdl-37516988

ABSTRACT

Ionic 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.

8.
Chem Sci ; 14(20): 5243-5265, 2023 May 24.
Article in English | MEDLINE | ID: mdl-37234906

ABSTRACT

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.

9.
Annu Rev Chem Biomol Eng ; 14: 109-140, 2023 06 08.
Article in English | MEDLINE | ID: mdl-37040783

ABSTRACT

Alternative polymer feedstocks are highly desirable to address environmental, social, and security concerns associated with petrochemical-based materials. Lignocellulosic biomass (LCB) has emerged as one critical feedstock in this regard because it is an abundant and ubiquitous renewable resource. LCB can be deconstructed to generate valuable fuels, chemicals, and small molecules/oligomers that are amenable to modification and polymerization. However, the diversity of LCB complicates the evaluation of biorefinery concepts in areas including process scale-up, production outputs, plant economics, and life-cycle management. We discuss aspects of current LCB biorefinery research with a focus on the major process stages, including feedstock selection, fractionation/deconstruction, and characterization, along with product purification, functionalization, and polymerization to manufacture valuable macromolecular materials. We highlight opportunities to valorize underutilized and complex feedstocks, leverage advanced characterization techniques to predict and manage biorefinery outputs, and increase the fraction of biomass converted into valuable products.


Subject(s)
Lignin , Polymers , Lignin/chemistry , Plants , Engineering , Biomass , Biofuels
10.
Article in English | MEDLINE | ID: mdl-36669816

ABSTRACT

Bisguaiacols, lignin-derivable bisphenols, are considered promising and possibly safer alternatives to bisphenol A (BPA), but comprehensive toxicity investigations are needed to ensure safety. Most toxicity studies of BPA and its analogues have focused on potential estrogenic activity, and only limited toxicological data are available on other toxicity aspects, such as genotoxicity at low exposure levels. In this study, the genotoxicity of six lignin-derivable bisguaiacols with varying regioisomer contents and degrees of methoxy substitution was investigated using a multi-tiered method, consisting of in silico simulations, in vitro Ames tests, and in vivo comet tests. The toxicity estimation software tool, an application that predicts toxicity of chemicals using quantitative structure-activity relationships, calculated that the majority of the lignin-derivable bisguaiacols were non-mutagenic. These results were supported by Ames tests using five tester strains (TA98, TA100, TA102, TA1535, and TA1537) at concentrations ranging from 0.5 pmol/plate to 5 nmol/plate. The potential genotoxicity of bisguaiacols was further evaluated using in vivo comet testing in fetal chicken livers, and in addition to the standard alkaline comet assay, the formamidopyrimidine DNA glycosylase enzyme-modified comet assay was employed to investigate oxidative DNA damage in the liver samples. The oxidative stress analyses indicated that the majority of lignin-derivable analogues showed no signs of mutagenicity (mutagenic index < 1.5) or genotoxicity, in comparison to BPA and bisphenol F, likely due to the methoxy groups on the lignin-derivable aromatics. These findings reinforce the potential of lignin-derivable bisphenols as safer alternatives to BPA.


Subject(s)
DNA Damage , Lignin , Mutagenicity Tests/methods , Lignin/toxicity , Comet Assay/methods , Mutagens/toxicity
11.
STAR Protoc ; 3(4): 101723, 2022 12 16.
Article in English | MEDLINE | ID: mdl-36313537

ABSTRACT

We present a computational modeling protocol that can accurately predict changes in both in vitro and in vivo gene expression levels in response to the application of various siRNA formulations. We describe how to use this Python-based pipeline to obtain crucial information, namely maximum silencing level and duration of silencing, toward the design of therapeutically relevant dosing regimens. The protocol details the steps for running internalization rate fitting to produce predictions based on experimental measurements from a single time point. For complete details on the use and execution of this protocol, please refer to Roh et al., 2021.


Subject(s)
Gene Silencing , RNA, Small Interfering/genetics , Kinetics
12.
JACS Au ; 2(1): 3-11, 2022 Jan 24.
Article in English | MEDLINE | ID: mdl-35098218

ABSTRACT

The sustainability of current and future plastic materials is a major focus of basic research, industry, government, and society at large. There is a general recognition of the positive impacts of plastics, especially packaging; however, the negative consequences around end-of-life outcomes and overall materials circularity are issues that must be addressed. In this perspective, we highlight some of the challenges associated with the many uses of plastic components and the diversity of materials needed to satisfy consumer demand, with several examples focused on plastics packaging. We also discuss the opportunities provided by conventional and advanced recycling/upgrading routes to petrochemical and bio-based materials and feedstocks, along with overviews of chemistry-related (experimental, computational, data science, and materials traceability) approaches to the valorization of polymers toward a closed-loop environment.

13.
Sci Adv ; 8(3): eabj7523, 2022 Jan 21.
Article in English | MEDLINE | ID: mdl-35044829

ABSTRACT

Chemocatalytic lignin valorization strategies are critical for a sustainable bioeconomy, as lignin, especially technical lignin, is one of the most available and underutilized aromatic feedstocks. Here, we provide the first report of an intensified reactive distillation­reductive catalytic deconstruction (RD-RCD) process to concurrently deconstruct technical lignins from diverse sources and purify the aromatic products at ambient pressure. We demonstrate the utility of RD-RCD bio-oils in high-performance additive manufacturing via stereolithography 3D printing and highlight its economic advantages over a conventional reductive catalytic fractionation/RCD process. As an example, our RD-RCD reduces the cost of producing a biobased pressure-sensitive adhesive from softwood Kraft lignin by up to 60% in comparison to the high-pressure RCD approach. Last, a facile screening method was developed to predict deconstruction yields using easy-to-obtain thermal decomposition data. This work presents an integrated lignin valorization approach for upgrading existing lignin streams toward the realization of economically viable biorefineries.

14.
Acc Chem Res ; 54(23): 4342-4353, 2021 Dec 07.
Article in English | MEDLINE | ID: mdl-34783520

ABSTRACT

ConspectusIon-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.

15.
ACS Nano ; 15(10): 16055-16066, 2021 10 26.
Article in English | MEDLINE | ID: mdl-34636541

ABSTRACT

A critical hurdle in the clinical translation of nucleic acid drugs is the inefficiency in testing formulations for therapeutic potential. Specifically, the ability to quantitatively predict gene expression is lacking when transitioning between cell culture and animal studies. We address this challenge by developing a mathematical framework that can reliably predict short-interfering RNA (siRNA)-mediated gene silencing with as few as one experimental data point as an input, evaluate the efficacies of existing formulations in an expeditious manner, and ultimately guide the design of nanocarriers with optimized performances. The model herein consisted of only essential rate-limiting steps and parameters with easily characterizable values of the RNA interference process, enabling the easy identification of which parameters play dominant roles in determining the potencies of siRNA formulations. Predictions from our framework were in close agreement with in vitro and in vivo experimental results across a retrospective analysis using multiple published data sets. Notably, our findings suggested that siRNA dilution was the primary determinant of gene-silencing kinetics. Our framework shed light on the fact that this dilution rate is governed by different parameters, i.e., cell dilution (in vitro) versus clearance from target tissue (in vivo), highlighting a key reason why in vitro experiments do not always predict in vivo outcomes. Moreover, although our current effort focuses on siRNA, we anticipate that the framework can be modified and applied to other nucleic acids, such as mRNA, that rely on similar biological processes.


Subject(s)
Nucleic Acids , Animals , Kinetics , RNA Interference , RNA, Small Interfering/genetics , Retrospective Studies
16.
Science ; 373(6550): 66-69, 2021 07 02.
Article in English | MEDLINE | ID: mdl-34210879

ABSTRACT

Plastics have revolutionized modern life, but have created a global waste crisis driven by our reliance and demand for low-cost, disposable materials. New approaches are vital to address challenges related to plastics waste heterogeneity, along with the property reductions induced by mechanical recycling. Chemical recycling and upcycling of polymers may enable circularity through separation strategies, chemistries that promote closed-loop recycling inherent to macromolecular design, and transformative processes that shift the life-cycle landscape. Polymer upcycling schemes may enable lower-energy pathways and minimal environmental impacts compared with traditional mechanical and chemical recycling. The emergence of industrial adoption of recycling and upcycling approaches is encouraging, solidifying the critical role for these strategies in addressing the fate of plastics and driving advances in next-generation materials design.

17.
J Environ Manage ; 287: 112300, 2021 Jun 01.
Article in English | MEDLINE | ID: mdl-33706090

ABSTRACT

Climate stationarity is a traditional assumption in the design of the urban drainage network, including green infrastructure practices such as bioretention cells. Predicted deviations from historic climate trends associated with global climate change introduce uncertainty in the ability of these systems to maintain service levels in the future. Climate change projections are made using output from coarse-scale general circulation models (GCMs), which can then be downscaled using regional climate models (RCMs) to provide predictions at a finer spatial resolution. However, all models contain sources of error and uncertainty, and predicted changes in future climate can be contradictory between models, requiring an approach that considers multiple projections. The performance of bioretention cells were modeled using USEPA's Storm Water Management Model (SWMM) to determine how design modifications could add resilience to these systems under future climate conditions projected for Knoxville, Tennessee, USA. Ten downscaled climate projections were acquired from the North American Coordinated Regional Downscaling Experiment program, and model bias was corrected using Kernel Density Distribution Mapping (KDDM). Bias-corrected climate projections were used to assess bioretention hydrologic function in future climate conditions. Several scenarios were evaluated using a probabilistic approach to determine the confidence with which design modifications could be implemented to maintain historic performance for both new and existing (retrofitted) bioretention cells. The largest deviations from current design (i.e., concurrently increasing ponding depths, thickness of media layer, media conductivity rates, and bioretention surface areas by 307%, 200%, 200%, and 300%, respectively, beyond current standards) resulted in the greatest improvements on historic performance with respect to annual volumes of infiltration and surface overflow, with all ten future climate scenarios across various soil types yielding increased infiltration and decreased surface overflow compared to historic conditions. However, lower performance was observed for more conservative design modifications; on average, between 13-82% and 77-100% of models fell below historic annual volumes of infiltration and surface overflow, respectively, when ponding zone depth, media layer thickness, and media conductivity were increased alone. Findings demonstrate that increasing bioretention surface area relative to the contributing catchment provides the greatest overall return on historic performance under future climate conditions and should be prioritized in locations with low in situ soil drainage rates. This study highlights the importance of considering local site conditions and management objectives when incorporating resiliency to climate change uncertainty into bioretention designs.


Subject(s)
Climate Change , Models, Theoretical , Hydrology , Tennessee , Uncertainty
18.
ACS Macro Lett ; 10(7): 864-872, 2021 07 20.
Article in English | MEDLINE | ID: mdl-35549209

ABSTRACT

Launching a startup company is like synthesizing a new molecule. There is a starting point and a general concept for how to achieve the desired end. Known steps may be taken, but a successful synthesis is rarely the result of the original plan and relies on perseverance and creativity. If done well, the starting molecule (idea) gives rise to a new final product (business). Having personally lived these journeys, the authors of this viewpoint distilled their combined experiences into relevant topics for scientific entrepreneurs. This viewpoint is not a how-to guide for launching a startup. Instead, relatable personal insights and potential best practices are shared to catalyze discussions around a topic of growing relevance to both the polymer community and workforce of the future.


Subject(s)
Commerce , Entrepreneurship , Workforce
19.
RSC Adv ; 11(36): 22149-22158, 2021 Jun 21.
Article in English | MEDLINE | ID: mdl-35480830

ABSTRACT

Lignin-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.

20.
ACS Macro Lett ; 9(4): 476-493, 2020 Apr 21.
Article in English | MEDLINE | ID: mdl-35648496

ABSTRACT

Sustainable polymers from lignocellulosic biomass have the potential to reduce the environmental impact of commercial plastics while also offering significant performance and cost benefits relative to petrochemical-derived macromolecules. However, most currently available biobased polymers are hampered by insufficient thermomechanical properties, low economic feasibility (e.g., high relative cost), and reduced scalability in comparison to petroleum-based incumbents. Future biobased materials must overcome these limitations to be competitive in the marketplace. Additionally, sustainability challenges at the beginning and end of the polymer lifecycle need to be addressed using green chemistry practices and improved end-of-life waste management strategies. This viewpoint provides an overview of recent developments that can mitigate many concerns with present materials and discusses key aspects of next-generation, biobased polymers derived from lignocellulosic biomass.

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