Scholarly Works, Macromolecules Innovation Institute (MII)

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Enhancing Electrical Conductivity of Stretchable Liquid Metal-Silver Composites through Direct Ink Writing
Zu, Wuzhou; Carranza, Hugo E.; Bartlett, Michael D. (American Chemical Society, 2024-04-30)
Structure-property-process relationships are a controlling factor in the performance of materials. This offers opportunities in emerging areas, such as stretchable conductors, to control process conditions during printing to enhance performance. Herein, by systematically tuning direct ink write (DIW) process parameters, the electrical conductivity of multiphase liquid metal (LM)-silver stretchable conductors is increased by a maximum of 400% to over 1.06 x 10(6) Sm(-1). This is achieved by modulating the DIW print velocity, which enables the in situ elongation, coalescence, and percolation of these multiphase inclusions during printing. These DIW printed filaments are conductive as fabricated and are soft (modulus as low as 1.1 MPa), stretchable (strain limit >800%), and show strain invariant conductivity up to 80% strain. These capabilities are demonstrated through a set of electromagnetic induction coils that can transfer power wirelessly through air and water, even under deformation. This work provides a methodology to program properties in stretchable conductors, where the combination of material composition and process parameters leads to greatly enhanced performance. This approach can find use in applications such as soft robots, soft electronics, and printed materials for deformable, yet highly functional devices.
Selective cross-metathesis of cellobiose derivatives with amido-functionalized olefinic structures: A model study for synthesis of cellulosic diblock copolymers
Sato, Yuuki; Sugimura, Kazuki; Edgar, Kevin J.; Kamitakahara, Hiroshi (Elsevier, 2024-09-01)
This work describes a model study for synthesis of cellulose-based block copolymers, investigating selective coupling of peracetyl beta-d-cellobiose and perethyl beta-d-cellobiose at their reducing-ends by olefin cross-metathesis (CM). Herein we explore suitable pairs of omega-alkenamides that permit selective, quantitative coupling by CM. Condensation reactions of hepta-O-acetyl-beta-d-cellobiosylamine or hepta-O-ethyl-beta-d-cellobiosylamine with acyl chlorides afforded the corresponding N-(beta-d-cellobiosyl)-omega-alkenamide derivatives with an aromatic olefin or linear olefinic structures. Among the introduced olefinic structures, CM of the undec-10-enamide (Type I olefin) and the acrylamide (Type II olefin) gave the hetero-block tetramers, N-(hepta-O-ethyl-beta-d-cellobiosyl)-N '-(hepta-O-acetyl-beta-d-cellobiosyl)-alkene-alpha,omega-diamides, with >98 % selectivity. Moreover, selectivity was not influenced by the cellobiose substituents when a Type I olefin with a long alkyl tether was used. Although the amide carbonyl group could chelate the ruthenium atom and reduce CM selectivity, the results indicated that such chelation is suppressed by sterically hindered pyranose rings or the long alkyl chain between the amido group and the double bond. Based on this model study, selective end-to-end coupling of tri-O-ethyl cellulose and acetylated cellobiose was accomplished, proving the concept that this model study with cellobiose derivatives is a useful signpost for selective synthesis of polysaccharide-based block copolymers.
Polysaccharide-based H₂S donors: Thiol-ene functionalization of amylopectin with H₂S-releasing N-thiocarboxyanhydrides
Chinn, Abigail F.; Williams, Noah R.; Miller, Kevin M.; Matson, John B. (Wiley, 2024-09-15)
Polymeric donors of gasotransmitters, gaseous signaling molecules such as hydrogen sulfide, nitric oxide, and carbon monoxide, hold potential for localized and extended delivery of these reactive gases. Examples of gasotransmitter donors based on polysaccharides are limited despite the availability and generally low toxicity of this broad class of polymers. In this work, we sought to create a polysaccharide H2S donor by covalently attaching N-thiocarboxyanhydrides (NTAs) to amylopectin, the major component of starch. To accomplish this, we added an allyl group to an NTA, which can spontaneously hydrolyze to release carbonyl sulfide and ultimately H2S via the ubiquitous enzyme carbonic anhydrase, and then coupled it to thiol-functionalized amylopectin of three different molecular weights (MWs) through thiol-ene "click" photochemistry. We also varied the degree of substitution (DS) of the NTA along the amylopectin backbone. H2S release studies on the six samples, termed amyl-NTAs, with variable MWs (three) and DS values (two), revealed that lower MW and higher DS led to faster release. Finally, dynamic light scattering experiments suggested that aggregation increased with MW, which may also have affected H2S release rates. Collectively, these studies present a new synthetic method to produce polysaccharide H2S donors for applications in the biomedical field.
A Green, Fire-Retarding Ether Solvent for Sustainable High-Voltage Li-Ion Batteries at Standard Salt Concentration
Xia, Dawei; Tao, Lei; Hou, Dong; Hu, Anyang; Sainio, Sami; Nordlund, Dennis; Sun, Chengjun; Xiao, Xianghui; Li, Luxi; Huang, Haibo; Lin, Feng (Wiley-V C H Verlag, 2024-10-01)
Lithium-ion batteries (LIBs) are increasingly encouraged to enhance their environmental friendliness and safety while maintaining optimal energy density and cost-effectiveness. Although various electrolytes using greener and safer glyme solvents have been reported, the low charge voltage (usually lower than 4.0 V vs Li/Li+) restricts the energy density of LIBs. Herein, tetraglyme, a lesstoxic, non-volatile, and non-flammable ether solvent, is exploited to build safer and greener LIBs. It is demonstrated that ether electrolytes, at a standard salt concentration (1 m), can be reversibly cycled to 4.5 V vs Li/Li+. Anchored with Boron-rich cathode-electrolyte interphase (CEI) and mitigated current collector corrosion, the LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode delivers competitive cyclability versus commercial carbonate electrolytes when charged to 4.5 V. Synchrotron spectroscopic and imaging analyses show that the tetraglyme electrolyte can sufficiently suppress the overcharge behavior associated with the high-voltage electrolyte decomposition, which is advantageous over previously reported glyme electrolytes. The new electrolyte also enables minimal transition metal dissolution and deposition. NMC811||hard carbon full cell delivers excellent cycling stability at C/3 with a high average Coulombic efficiency of 99.77%. This work reports an oxidation-resilient tetraglyme electrolyte with record-high 4.5 V stability and enlightens further applications of glyme solvents for sustainable LIBs by designing Boron-rich interphases.
Kinetics of Calcite Nucleation onto Sulfated Chitosan Derivatives and Implications for Water-Polysaccharide Interactions during Crystallization of Sparingly Soluble Salts
Knight, Brenna M.; Mondal, Ronnie; Han, Nizhou; Pietra, Nicholas F.; Hall, Brady A.; Edgar, Kevin J.; Welborn, Valerie Vaissier; Madsen, Louis A.; De Yoreo, James J.; Dove, Patricia M. (American Chemical Society, 2024-07-11)
Anionic macromolecules are found at sites of CaCO3 biomineralization in diverse organisms, but their roles in crystallization are not well-understood. We prepared a series of sulfated chitosan derivatives with varied positions and degrees of sulfation, DS(SO3-), and measured calcite nucleation rate onto these materials. Fitting the classical nucleation theory model to the kinetic data reveals the interfacial free energy of the calcite-polysaccharide-solution system, gamma(net), is lowest for nonsulfated controls and increases with DS(SO3-). The kinetic prefactor also increases with DS(SO3-). Simulations of Ca2+-H2O-chitosan systems show greater water structuring around sulfate groups compared to uncharged substituents, independent of sulfate location. Ca2+-SO3- interactions are solvent-separated by distances that are inversely correlated with DS(SO3-) of the polysaccharide. The simulations also predict SO3- and NH3+ groups affect the solvation waters and HCO3- ions associated with Ca2+. Integrating the experimental and computational evidence suggests sulfate groups influence nucleation by increasing the difficulty of displacing near-surface water, thereby increasing gamma(net). By correlating gamma(net) and net charge per monosaccharide for diverse polysaccharides, we suggest the solvent-separated interactions of functional groups with Ca2+ influence thermodynamic and kinetic components to crystallization by similar solvent-dominated processes. The findings reiterate the importance of establishing water structure and properties at macromolecule-solution interfaces.
Ethyl cellulose-block-poly(benzyl glutamate) block copolymer compatibilizers for ethyl cellulose/poly(ethylene terephthalate) blends
Chinn, Abigail F.; Trindade Coutinho, Isabela; Kethireddy, Saipranavi Reddy; Williams, Noah R.; Knott, Kenneth M.; Moore, Robert B.; Matson, John B. (Royal Society Chemistry, 2024-08-27)
Blends of petroleum-based polymers with bio-sourced polymers are an alternative to polymers derived from non-renewable resources. However, polymer blends are usually immiscible, and a compatibilizer, often a block copolymer, is required to improve mixing. In this work, we synthesized a block copolymer of ethyl cellulose (ECel) and poly(benzyl glutamate), termed ECel-block-poly(BG), and we applied it as a compatibilizer for ECel/poly(ethylene terephthalate) (ECel/PET) blends. To synthesize this block copolymer, two ECel-NH2 macroinitiators were evaluated for ring-opening polymerization of benzyl glutamate-N-thiocarboxyanhydride (BG-NTA), one with the amine directly attached to the ECel reducing chain end, and the other with a short PEG linker between ECel and the amine initiator. The PEG-containing macroinitiator led to the synthesis of a block copolymer that was unimodal by size-exclusion chromatography (SEC) while the other initiator led to uncontrolled homopolymerization of BG-NTA, presumably due to steric hindrance near the primary amine. A series of solvent studies revealed that polymerization of BG-NTA in CH2Cl2 was the best system for obtaining the ECel-block-poly(BG) block copolymer, achieving 95% conversion based on H-1 NMR spectroscopy. The success of chain extension and molecular weight analysis were evaluated using SEC with multi-angle light scattering (SEC-MALS). Blends composed of 70% ECel and 30% PET with different weight percentages (wt%) of block copolymer compatibilizer were made via solvent casting from hexafluoroisopropanol. Phase contrast optical microscopy and small-angle laser light scattering were used to probe the effectiveness of the ECel-block-poly(BG) block copolymer as a compatibilizer (5-30 wt%) for the 70/30 ECel/PET blends. A decrease in average domain size from 15 +/- 4 mu m in the base blend (without compatibilizer) to 2 +/- 1 mu m in the blend containing 30 wt% ECel-block-poly(BG) indicated successful compatibilization of the blend.
Customizing STEM organogels using PET-RAFT polymerization
Bowman, Zaya; Baker, Jared G.; Hughes, Madeleine J.; Nguyen, Jessica D.; Garcia, Mathew; Tamrat, Nahome; Worch, Joshua C.; Figg, C. Adrian (Royal Society Chemistry, 2024-10-01)
Photoinduced electron/energy transfer (PET) reversible addition-fragmentation chain transfer (RAFT) polymerization results in more uniform polymer networks compared to networks synthesized by thermally initiated RAFT polymerizations. However, how PET-RAFT polymerizations affect molecular weight control and physical properties during parent-to-daughter block copolymer network synthesis is unclear. Herein, we synthesized a structurally tailored and engineered macromolecular (STEM) organogel composed of poly(methyl acrylate) and a degradable crosslinker. Chain extensions on the STEM organogel were performed using PET-RAFT polymerization of either methyl acrylate (MA) or N,N-dimethylacrylamide (DMA) with or without additional crosslinker. We found that physical properties were dependent on monomer composition and crosslinking. The swelling ratios of the diblock networks were similar in DMAc. Conversely, swelling ratios in water increased by 430% for networks extended with MA and 5200% for networks extended with DMA compared to the parent organogels. Rheological analysis showed a tunable modulus from 1000-4000 Pa. However, size exclusion chromatography analysis of the degraded gels revealed that the PET-RAFT polymerization chain extension yielded disperse block copolymers with poor control over the molecular weight. These results indicate that PET-RAFT polymerizations can be used to expand organogel networks to block copolymer networks to modulate physical properties, but control over the chain extension polymerization is lost. Looking forward, this report points to opportunities to gain control over PET-RAFT block copolymer network synthesis via secondary reversible deactivation pathways. PET-RAFT polymerization was used to modify STEM organogels, while degradable linkers enabled the characterization of the resulting block copolymers.
Electrospun Lithium Porous Nanosorbent Fibers for Enhanced Lithium Adsorption and Sustainable Applications
Pan, Yanan; Zhang, Yue; Thompson, Connor; Liu, Guoliang; Zhang, Wencai (American Chemical Society, 2024-09-30)
Electrospun nanosorbent fibers specifically designed for efficient lithium extraction were developed, exhibiting superior physicochemical properties. These fibers were fabricated using a polyacrylonitrile/dimethylformamide matrix, with viscosity and dynamic mechanical analysis showing that optimal interactions were achieved at lower contents of layered double hydroxide. This meticulous adjustment in formulation led to the creation of lithium porous nanosorbent fibers (Li-PNFs-1). Li-PNFs-1 exhibited outstanding mechanical attributes, including a yield stress of 0.09 MPa, a tensile strength of 2.48 MPa, and an elongation at a break of 19.7%. Additionally, they demonstrated pronounced hydrophilicity and hierarchical porous architecture, which greatly favor rapid wetting kinetics and lithium adsorption. Morphologically, they exhibited uniform smoothness with a diameter averaging 546 nm, indicative of orderly crystalline growth and a dense molecular arrangement. X-ray photoelectron spectroscopy and density functional theory using Cambridge Serial Total Energy Package revealed modifications in the spatial and electronic configurations of polyacrylonitrile due to hydrogen bonding, facilitating lithium adsorption capacity up to 13.45 mg/g under optimal conditions. Besides, kinetics and isotherm showed rapid equilibrium within 60 min and confirmed the chemical and selective nature of Li+ uptake. These fibers demonstrated consistent adsorption performance across multiple cycles, highlighting their potential for sustainable use in industrial applications.
Catalyzing PET-RAFT Polymerizations Using Inherently Photoactive Zinc Myoglobin
Anderson, Ian C.; Gomez, Darwin C.; Zhang, Meijing; Koehler, Stephen J.; Figg, C. Adrian (Wiley-V C H Verlag, 2025-01-10)
Protein photocatalysts provide a modular platform to access new reaction pathways and affect product outcomes, but their use in polymer synthesis is limited because co-catalysts and/or co-reductants are required to complete catalytic cycles. Herein, we report using zinc myoglobin (ZnMb), an inherently photoactive protein, to mediate photoinduced electron/energy transfer (PET) reversible addition-fragmentation chain transfer (RAFT) polymerizations. Using ZnMb as the sole reagent for catalysis, photomediated polymerizations of N,N-dimethylacrylamide in PBS were achieved with predictable molecular weights, dispersity values approaching 1.1, and high chain-end fidelity. We found that initial apparent rate constants of polymerization increased from 4.6x10-5 s-1 for zinc mesoporpyhrin IX (ZnMIX) to 6.5x10-5 s-1 when ZnMIX was incorporated into myoglobin to yield ZnMb, indicating that the protein binding site enhanced catalytic activity. Chain extension reactions comparing ZnMb-mediated RAFT polymerizations to thermally-initiated RAFT polymerizations showed minimal differences in block copolymer molecular weights and dispersities. This work enables studies to elucidate how protein modifications (e.g., secondary structure folding, site-directed mutagenesis, directed evolution) can be used to modulate polymerization outcomes (e.g., selective monomer additions towards sequence control, tacticity control, molar mass distributions).
High cycle performance of twisted and coiled polymer actuators
Tsai, Samuel; Wang, Qiong; Hur, Ohnyoung; Bartlett, Michael D.; King, William P.; Tawfick, Sameh (Elsevier, 2025-01-01)
Twisted and coiled polymer actuators (TCPA), also known as coiled artificial muscles, are gaining popularity in soft robotics due to their large contractile actuation and work capacity. However, while it has been previously claimed that the stroke of TCPA remains stable after thousands of cycles, their absolute length change has not been rigorously studied. Here, we constructed an isobaric cycling setup that relies on fast heating and cooling by water immersion. This enables testing for 10k cycles in a duration of 56 hours, where the muscle temperature is varied between 15 degrees C and 75 degrees C at a rate of 20 seconds per cycle. Surprisingly, while the stroke usually remains unchanged for the entire 10k cycles as previously claimed, the final muscle loaded length exhibits all the geometrical possibilities of creep behavior as it can remain unchanged, elongate (creep), or contract (reverse creep) at the end of the test. Based on a wide range of experiments, we derived an empirical law which captures the observed relationship between the final muscle length change Delta L, the stroke alpha, and the passive strain 80: 80 + alpha = Delta L. Using this relation, the final length change of the muscle can be predicted from the first 100 cycles only. We show that polyvinylidene fluoride (PVDF), which does not swell in water, and nylon, which swells, follow this empirical law by testing in water with and without a protective coating, respectively. These results offer practical design guidelines for predictive actuation over thousands of cycles.
Reaction-Type-Dependent Behavior of Redox-Hopping in MOFs-Does Charge Transport Have a Preferred Direction?
Yan, Minliang; Bowman, Zaya; Knepp, Zachary J.; Peterson, Aiden; Fredin, Lisa A.; Morris, Amanda J. (American Chemical Society, 2024-11-21)
Redox hopping is the primary method of electron transport through redox-active metal-organic frameworks (MOFs). While redox hopping adequately supports the electrocatalytic application of MOFs, the fundamental understandings guiding the design of redox hopping MOFs remain nascent. In this study, we probe the rate of electron and hole transport through a singular MOF scaffold to determine whether the properties of the MOF promote the transport of one carrier over the other. A redox center, [RuII(bpy)2(bpy-COOH)]2+, where bpy = 2,2 '-bipyridine and bpy-COOH = 4-carboxy-2,2 '-bipyridine, was anchored within NU-1000. The electron hopping coefficients (D e ) and ion diffusion coefficients (D i ) were calculated via chronoamperometry and application of the Scholz model. We found that electrons transport more rapidly than holes in the studied MOF. Interestingly, the correlation between D e and self-exchange rate built in previous research predicted reversely. The contradicting result indicates that spacing between the molecular moieties involved in a particular hopping process dominates the response.
Gelation during Ring-Opening Reactions of Cellulosics with Cyclic Anhydrides: Phenomena and Mechanisms
Petrova, Stella P.; Zheng, Zhaoxi; Heinze, Daniel Alves; Welborn, Valerie; Bortner, Michael J.; Schmidt-Rohr, Klaus; Edgar, Kevin J. (American Chemical Society, 2024-11-21)
Cellulose esters are used in Food and Drug Administration-approved oral formulations, including in amorphous solid dispersions (ASDs). Some bear substituents with terminal carboxyl moieties (e.g., hydroxypropyl methyl cellulose acetate succinate (HPMCAS)); these omega-carboxy ester substituents enhance interactions with drug molecules in solid and solution phases and enable pH-responsive drug release. However, the synthesis of carboxyl-pendent cellulose esters is challenging, partly due to competing reactions between introduced carboxyl groups and residual hydroxyls on different chains, forming either physically or covalently cross-linked systems. As we explored ring-opening reactions of cyclic anhydrides with cellulose and its esters to prepare polymers designed for high ASD performance, we became concerned upon encountering gelation. Herein, we probe the complexity of such ring-opening reactions in detail, for the first time, utilizing rheometry and solid-state 13C NMR spectroscopy. Gelation in these ring-opening reactions was caused predominantly by physical interactions, progressing in some cases to covalent cross-links over time.
Scalable Accelerated Materials Discovery of Sustainable Polysaccharide-Based Hydrogels by Autonomous Experimentation and Collaborative Learning
Liu, Yang; Yue, Xubo; Zhang, Junru; Zhai, Zhenghao; Moammeri, Ali; Edgar, Kevin J.; Berahas, Albert S.; Al Kontar, Raed; Johnson, Blake N. (American Chemical Society, 2024-12-11)
While some materials can be discovered and engineered using standalone self-driving workflows, coordinating multiple stakeholders and workflows toward a common goal could advance autonomous experimentation (AE) for accelerated materials discovery (AMD). Here, we describe a scalable AMD paradigm based on AE and "collaborative learning". Collaborative learning using a novel consensus Bayesian optimization (BO) model enabled the rapid discovery of mechanically optimized composite polysaccharide hydrogels. The collaborative workflow outperformed a non-collaborating AMD workflow scaled by independent learning based on the trend of mechanical property evolution over eight experimental iterations, corresponding to a budget limit. After five iterations, four collaborating clients obtained notable material performance (i.e., composition discovery). Collaborative learning by consensus BO can enable scaling and performance optimization for a range of self-driving materials research workflows driven by optimally cooperating humans and machines that share a material design objective.
Anisotropic and Heterogeneous Thermal Conductivity in Programmed Liquid Metal Composites Through Direct Ink Writing
Hur, Ohnyoung; Markvicka, Eric J.; Bartlett, Michael D. (Wiley-V C H Verlag, 2025-03-01)
Thermal management in electric vehicles, electronics, and robotics requires the systematic ability to dissipate and direct the flow of heat. Thermally conductive soft composites are promising for thermal management due to their high thermal conductivity and mechanical flexibility. However, composites typically have the same microstructure throughout a film, which limits directional and spatial control of thermal management in emerging systems that have distributed heat loads. Herein, directional and spatially tunable thermal properties are programmed into liquid metal (LM) soft composites through a direct ink writing (DIW) process. Through the local control of LM droplet aspect ratio and orientation this programmable LM microstructure has a thermal conductivity in the direction of LM elongation of 9.9 W m-1K-1, which is similar to 40 times higher than the unfilled elastomer (0.24 W m-1K-1). The DIW process enables LM droplets to be oriented in specific directions with tunable aspect ratios at different locations throughout a continuous film. This introduces anisotropic and heterogeneous thermal conductivity in compliant films to control the direction and magnitude of heat transfer. This methodology and resulting materials can provide designed thermal management solutions for rigid and soft devices.
Process parameter optimization in polymer powder bed fusion of final part properties in polyphenylene sulfide through design of experiments
Ho, Ian; Bryant, Jackson; Chatham, Camden; Williams, Christopher (Springernature, 2024-12-17)
The Additive Manufacturing (AM) modality of Laser-Based Powder Bed Fusion of Polymers (PBF-LB/P) is an established method for manufacturing semi-crystalline polymers. Like other AM processes, the selection of PBF-LB/P process parameters is critical as it has direct effect on final part properties. While prior research has been predominantly focused on polyamides (e.g., nylon 12), there exists a gap in exploring how process parameters affect higher performance polymers, such as polyphenylene sulfide (PPS). This work aims to explore the effects of PBF-LB/P process parameters on PPS parts printed via PBF-LB/P. While prior PBF-LB/P parameter research primarily relies on evaluating energy input to the system through a single numerical value of energy density, this study investigates the interplay of the print parameters within the energy density equation. To achieve these goals, an analysis was performed on the influence of the laser power, hatch spacing, and beam velocity on ultimate tensile strength (UTS), modulus, and crystallinity of printed parts. A Taguchi L8 array was used in balancing the print parameter combinations allowing for isolation of variance to the specific factors and interactions. Through this approach, print parameter combinations that improved UTS and modulus were identified. Additionally, the study revealed that numerically equivalent energy densities did not lead to equivalent performance, underscoring the significance for including the constitutive process parameters within the energy density equation when establishing process property relationships in printing with PBF-LB/P.
Copper Oxidation-Induced Nanoscale Deformation of Electromechanical, Laminate Polymer/Graphene Thin Films during Thermal Annealing: Implications for Flexible, Transparent, and Conductive Electrodes
Croft, Zacary L.; Valenzuela, Oscar; Thompson, Connor; Whitfield, Brendan; Betzko, Garrett; Liu, Guoliang (American Chemical Society, 2024-12-12)
The transfer of large-area, continuous, chemical vapor deposition (CVD)-grown graphene without introducing defects remains a challenge for fabricating graphene-based electronics. Polymer thin films are commonly used as supports for transferring graphene, but they typically require thermal annealing before transfer. However, little work has been done to thoroughly investigate how thermal annealing affects the polymer/graphene thin film when directly annealed on the growth substrate. In this work, we demonstrate that under improper annealing conditions, thermal annealing of poly(ether imide)/single-layer graphene (PEI/SLG) thin films on Cu causes detrimental nanoscale structural deformations, which permanently degrade the mechanical properties. Furthermore, we elucidate the mechanisms of PEI/SLG deformation during thermal annealing and find that permanent deformations and cracking are caused by Cu substrate oxidation. This study provides an understanding of annealing-induced deformation in polymer/graphene thin films. We anticipate that this knowledge will be useful for further developing defect-free, graphene-based thin film electronics.
Advancements, applications, and challenges of polyhydroxyalkanoates (PHAs) in packaging as biodegradable bioplastics
Ahn, Kihyeon; Taylor, Chloe M.; Kim, Young-Teck (2025-04-01)
The rising environmental concerns associated with petroleum-based plastics have driven the search for biodegradable alternatives, particularly for short-term and dispos- able applications. Polyhydroxyalkanoates (PHAs), a class of biopolymers and bioplastics, derived from renewable resources, offer promising features for sustainable packaging. However, PHAs often face technical challenges limiting their practical applications in packaging. Recent advancements in biomanufacturing processes have aimed to address the limitations, such as thermal stability, selective biodegradability, barrier properties, and mechanical and physical properties, through diverse approaches including new production processes, diversified feedstocks, and fermentation technologies. This chap- ter explores the structural diversity and types of PHAs, their environmental degradation behaviors, and the perspectives on their application within the packaging industry, particularly in alignment with regulatory standards and sustainability goals.
Thermodynamics of calcium binding to heparin: Implications of solvation and water structuring for polysaccharide biofunctions
Knight, Brenna M.; Gallagher, Connor M. B.; Schulz, Michael D.; Edgar, Kevin J.; McNaul, Caylyn D.; McCutchin, Christina A.; Dove, Patricia M. (National Academy of Sciences, 2025-08-26)
Heparin sulfates are found in all animal tissues and have essential roles in living systems. This family of biomacromolecules modulates binding to calcium ions (Ca²⁺) in low free energy reactions that influence biochemical processes from cell signaling and anticoagulant efficacy to biomineralization. Despite their ubiquity, the thermodynamic basis for how heparans and similarly functionalized biomolecules regulate Ca²⁺ interactions is not yet established. Using heparosan (Control) and heparins with different positions of sulfate groups, we quantify how SO₃⁻ and COO⁻ content and SO₃⁻ position modulate Ca²⁺ binding by isothermal titration calorimetry. The free energy of all heparin-Ca²⁺ interactions (ΔGrxn) is dominated by entropic contributions due to favorable water release from polar, hydrophilic groups. Heparin with both sulfate esters (O-SO₃⁻) and sulfamides (N-SO₃⁻) has the strongest binding to Ca²⁺ compared to heparosan and to heparin with only O-SO₃⁻ groups (~3X). By linking Ca²⁺ binding thermodynamics to measurements of the interfacial energy for calcite (CaCO₃) crystallization onto polysaccharides, we show molecule-specific differences in nucleation rate can be explained by differences in water structuring during Ca²⁺ interactions. A large entropic term (-TΔSrxn) upon Ca²⁺–polysaccharide binding correlates with high interfacial energy to CaCO₃ nucleation. Combining our measurements with literature values indicates many Ca²⁺–polysaccharide interactions have a shared thermodynamic signature. The resulting enthalpy–entropy compensation relationship suggests these interactions are generally dominated by water restructuring involving few conformational changes, distinct from Ca²⁺–protein binding. Our findings quantify the thermodynamic origins of heparin-specific interactions with Ca²⁺ and demonstrate the contributions of solvation and functional group position during biomacromolecule-mediated ion regulation.
Cholesterol modulates membrane elasticity via unified biophysical laws
Kumarage, Teshani; Gupta, Sudipta; Morris, Nicholas B.; Doole, Fathima T.; Scott, Haden L.; Stingaciu, Laura-Roxana; Pingali, Sai Venkatesh; Katsaras, John; Khelashvili, George; Doktorova, Milka; Brown, Michael F.; Ashkar, Rana (Springer, 2025-07)
Cholesterol and lipid unsaturation underlie a balance of opposing forces that features prominently in adaptive cell responses to diet and environmental cues. These competing factors have resulted in contradictory observations of membrane elasticity across different measurement scales, requiring chemical specificity to explain incompatible structural and elastic effects. Here, we demonstrate that - unlike macroscopic observations - lipid membranes exhibit a unified elastic behavior in the mesoscopic regime between molecular and macroscopic dimensions. Using nuclear spin techniques and computational analysis, we find that mesoscopic bending moduli follow a universal dependence on the lipid packing density regardless of cholesterol content, lipid unsaturation, or temperature. Our observations reveal that compositional complexity can be explained by simple biophysical laws that directly map membrane elasticity to molecular packing associated with biological function, curvature transformations, and protein interactions. The obtained scaling laws closely align with theoretical predictions based on conformational chain entropy and elastic stress fields. These findings provide unique insights into the membrane design rules optimized by nature and unlock predictive capabilities for guiding the functional performance of lipid-based materials in synthetic biology and real-world applications.
Mechanochemical Synthesis of Recyclable Biohybrid Polymer Networks Using Whole Biomass
Jiang, Meng; Bird, Emily; Ham, Woojung; Worch, Joshua C. (Wiley-VCH, 2025-07)
Whole-plant biomass from non-agricultural sources and waste biomass from processing agricultural products are both promising feedstocks for biopolymer production because they are abundant and do not compete with food production. However, their processing steps are notoriously tedious with the final materials often displaying inferior performance and limited scope in their properties. Here, we report a strategy to integrate whole-cell spirulina, a green-blue algae, into robust biohybrid algae-polyimine networks by leveraging a mechanochemical ball milling method. This strategy provides a greener synthetic approach to conventional solvent casting methods for polyimine synthesis; it simultaneously overcomes persistent constraints encountered in biomass processing and derivatization. The biohybrid algae-based materials retain adaptability and recyclability imparted by their underlying dynamic covalent polymer matrix and display enhanced mechanical properties compared to their all-synthetic equivalents. These advantageous properties are attributed to the unique morphology of the ball milled biohybrid materials which are facilitated by integration of the spirulina into the polymer matrix. Substituting spirulina with alternative biomass sources such as waste agricultural products also yields robust biohybrid networks, thus highlighting the broad utility of this straightforward mechanochemical synthesis to create more sustainable materials.

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