Microbial functional amyloids play central roles in biofilm formation and serve as foundational building blocks for autogenic engineered living materials (ELM), yet the structural design space governing their assembly and stability remains poorly defined. In Escherichia coli , the β-solenoid protein CsgA functions as a canonical extracellular matrix scaffold, but prior engineering efforts have primarily focused on terminal functionalization rather than modification of the β-solenoid core itself. Here, inspired by the evolutionary diversification of CsgA-like proteins, which expands along the vertical fiber axis, we explore a second orthogonal axis of structural plasticity: the horizontal dimension of the β-solenoid. We rationally designed a library of CsgA variants in which the length of individual β-strands was systematically reduced or extended from the native seven residues to lengths spanning 3–21 residues, while preserving conserved gate residues and loop regions. Integration of AI-based structure prediction using AlphaFold2 with all-atom molecular dynamics simulations reveals that β-solenoid stability arises from a balance among strand length, residue composition, and solvent interactions, thereby defining both lower and optimal bounds for nanofiber assembly. Experimental validation demonstrates that engineered Escherichia coli can secrete and assemble these CsgA variants into extracellular nanofibers through the native curli biogenesis machinery, while preserving the characteristic cross-β architecture. Additionally, the CsgA β-solenoid variant library translates molecular design into macroscopic ELM, with deletion variants showing an inverse relationship between stiffness and extensibility, from highly extensible 3aa to stiff, strong 5aa films. Insertion-based variants largely retain CsgA-like extensibility while enabling tunable stiffness and strength across strand lengths. Together, these findings uncover previously unrecognized structural plasticity in microbial β-solenoid proteins and establish β-strand length as a generalizable design parameter linking molecular architecture to nanofiber stability, with implications spanning microbial functional amyloids and the rational design of autogenic engineered living materials.

During the deposition step in extrusion-based additive manufacturing (EB-AM) of semicrystalline polymers, solidification happens as crystals nucleate and interconnect, resulting in physical gelation of the system. The solidification step, governed by crystallization and physical gelation phenomena, affects the success of the process and the morphology of the printed part. We demonstrate that when fillers are present in polypropylene, they aid the physical gelation process through facilitated interconnectivity of forming crystals. The concentration of fillers and their aspect ratio seem to determine the extent to which they help induce physical gelation. Adversely, fillers hinder nucleation, affecting crystallization, which limits solidification. This paper studies how carbon fiber and graphite affect the solidification of polypropylene, focusing on the balance between physical gelation and crystallization. By decoupling physical gelation from crystallization, we found that while both fillers exhibit comparable nucleation activity, carbon fiber more strongly increases solidification temperature. To further correlate processing and morphology, the effect of medium-format EB-AM processing on polymer crystal alignment is studied, showing less alignment than literature values for small-format EB-AM. This paper provides significant insights into how fillers affect the solidification behavior of semicrystalline polymers, which is a key parameter for successfully designing optimal formulations for processing through EB-AM.

Poly(ethylene terephthalate) (PET) is the most recycled plastic; however, upcycling of this commodity polymer to value-added products has remained limited. Recent attempts to produce PET aerogels have relied on toxic solvents, chemical conversions and cross-linking, and reinforcement to achieve useful mechanical performance. Now, using a new benign solvent (1,3-diphenylacetone), we report a simple, safe, and sustainable dissolution and gelation procedure to convert waste PET into low density, monolithic aerogels with high mechanical strength (E = 20 ± 2 MPa) and remarkably low thermal conductivity (k = 21.9 to 28.9 mW m-1 K-1). The key to this process is controlled crystal nucleation by a self-seeding phenomenon during gelation that establishes a mesoscale fibrillar framework. Our strategy offers a benign sol-gel process to upcycle plastic waste into a new form of pure PET for advanced thermal insulation.

Autogenic engineered living materials (ELMs) enable the in situ production and engineering of native extracellular matrix (ECM). However, existing autogenic ELMs remain limited in scope and functionality. Here, we present a versatile platform for de novo autogenic functional ELMs, leveraging protein mining, computational modeling, and synthetic biology. By analyzing 33,564 CsgA-like homologs, we identify candidates for de novo ECM protein nanofibers. Using AlphaFold2 and molecular dynamics simulations, we elucidate the structural stability of these β-solenoid proteins. By reprogramming the Escherichia coli curli machinery, we achieve the biosynthesis of CsgA-like ELMs from non-model bacteria, featuring up to a 9-fold increased molecular weight and expanded β-sheet repeat units. Furthermore, we fabricate macroscopic biomaterials with enhanced mechanical properties (a 3-fold increase in storage modulus), and their extracellular fiber networks attenuate UV-C irradiation, extending the survival of embedded cells by 5-fold. We further demonstrate programmable functionalities, including 3D printability and selective binding to nanoparticles and antibodies. This work establishes a powerful framework for discovering, designing, and harnessing natural biomolecular systems to advance next-generation autogenic ELMs.

Molecular dynamics (MD) simulations of three α-glucans─amylose, dextran, and pullulan─were performed in explicit solvent to investigate how differences in their glycosidic linkages influence molecular conformation and solvation dynamics, and to assess the performance of three major force fields (FFs): CHARMM36, GLYCAM06, and OPLS-AA. Structural analysis revealed that amylose adopts a more extended and constrained conformation owing to its α-(1 → 4) linkages, whereas dextran and pullulan exhibit more collapsed structures. Differences in linkage chemistry also influenced the organization of surrounding water, with this effect more pronounced in CHARMM than in GLYCAM or OPLS. Dextran formed more stable hydrogen bonds with water than amylose or pullulan. Although glucan-water nonbonded interactions were energetically more favorable in GLYCAM and OPLS, these FFs also predicted stronger nonpolar interactions that promoted more compact glucan conformations. Overall, the results indicate that glucan-glucan interactions contribute comparably to glucan-water interactions in determining polysaccharide structure. These insights clarify molecular determinants of glucan solubility and hydration and provide a basis for designing glucan-based materials with tunable properties.

Sequence distribution in poly(vinyl alcohol) (PVOH)-based copolymers strongly influences their properties, yet methods for producing and characterizing highly blocky microstructures remain limited. Conventional postpolymerization hydrolysis and reacetylation methods yield only moderately blocky microstructures, limiting access to well-defined copolymer sequences. To access highly blocky acetylated poly(vinyl alcohol) (AcPVOH) microstructures, PVOH was acetylated in the heterogeneous (i.e., semicrystalline), supercritical CO2-swollen film state. A matched set of random rAcPVOH and blocky bAcPVOH copolymers with degrees of acetylation spanning 3-30% were prepared, and differences between their H-1 and C-13 NMR spectra were explored. Dyad peak assignments were confirmed using HSQC and HMBC spectroscopy. The copolymer blockiness was quantified using C-13 NMR spectroscopy, where the random copolymers exhibited blocky character eta values close to 1, consistent with statistically random sequencing. In contrast, the blocky products had eta values around 0.25, indicating they were significantly blockier than any previously reported blocky AcPVOH copolymer. Blockiness was also quantified using the randomness factor R, where the blocky products exhibited R values well above 80, consistent with a highly blocky microstructure. Together, these results establish scCO(2) acetylation as a robust route to synthesizing highly blocky PVOH-based copolymers and lay the fundamental groundwork for elucidating the microstructure of these commercially relevant water-soluble polymers using NMR spectroscopy.

Alcohol-water solvent systems are commonly used to disperse perfluorosulfonic acid ionomers (PFSAs) for the fabrication of proton-exchange membranes, catalyst layers, and thin films. The profound effect of PFSA chemical structure, concentration, and solvent composition on the colloidal morphology of PFSA dispersions is investigated using small-angle X-ray scattering (SAXS). Five different PFSA chemical structures and three different binary alcohol-water solvent systems are utilized for relevance to industrial processing parameters. Although evidence for a cylindrical PFSA aggregate morphology is shown, the strong scattering maximum frequently observed in scattering patterns of semidilute PFSA dispersions is demonstrated to prevent the quantification of aggregate length. A semiempirical small-angle scattering model is introduced to fit the dispersion scattering patterns over a wide q-range and quantify aggregate dimensions on length scales smaller than the average interaggregate spacing. A thermodynamic model based on the self-assembly of cylindrical micelles is shown to describe aggregate dimensions. The surface area per side chain, σ, calculated from this model is observed to increase with increasing alcohol concentration in the solvent, while the aggregate radius and average number of chains per aggregate both decrease. These observations suggest that increases in σ may represent an increase in the hydrophobic component of the PFSA aggregates to the solvent due to improved compatibility between the PFSA and solvent. The PFSA-solvent interactions are studied in more detail in a second publication of the present study.

In this work, the post-polymerization sulfonation of poly(ether ketone ketone) (KEPSTAN 8001, T/I = 80/20) with chlorosulfonic acid is reported for the first time. Two microstructures are synthesized-a random microstructure through functionalization in the homogeneous solution state and a blocky microstructure through functionalization in the heterogeneous gel state. Poly(ether ketone ketone) (PEKK) is gelled by thermally induced phase separation from a benign solvent, diphenyl acetone. Degrees of sulfonation between 3 and 59 mol% were obtained for both the random and blocky sulfonated PEKK and verified by NMR. At similar degrees of sulfonation, blocky sulfonated PEKK membranes exhibited greater crystallizability, faster crystallization rates, higher conductivity, and improved solubility resistance in water, as compared to the random analogs. Conductivities comparable to state-of-the-art benchmark material Nafion 212 were obtained for the blocky materials. Superior thermal properties and proton conductivities of the blocky microstructures are attributed to the heterogeneous gel state functionalization resulting in longer runs of pristine PEKK units between sulfonated monomers as compared to the random analogs. SAXS/WAXS analysis revealed that the blocky microstructure resulted in larger ionic domains compared to the random analogs. This finding further demonstrates blocky functionalization in the gel state is a facile way to produce high-performance proton exchange membranes through effective blocking up of the sulfonate functionality, while preserving long runs of crystallizable segments along the chains.

Regioselectively substituted amylose acetate-graft-polylactide (AmAc-g-PLA) graft polymers were synthesized via grafting-to "click" reaction between C6-azide functionalized AmAc and alkyne-terminated PLA. Alkyne-terminated PLA synthesized through organocatalytic ring-opening polymerization (ROP) permitted control over graft degree of polymerization (DP) and stereochemistry, while azide functionalized AmAc with tailorable C6-azide degree of substitution (DS) allowed graft density control. This describes the first synthesis of polysaccharide-based graft polymers with exclusive C6 grafting and controllable topology. Thermal analysis indicates that glass transition temperatures (Tg) of AmAc and PLA segments are affected after grafting-to coupling, with poly(l-lactide) (PLLA) grafts maintaining crystallizability. AmAc-graft-poly(d,l-lactide) (PDLLA) graft polymers were effective compatibilizers for immiscible blends of starch acetate (StAc) and PDLLA as evidenced by small-angle laser light scattering (SALLS) and phase contrast optical microscopy (PCOM). This method permits the determination of structure-property relationships with regard to the effect of graft polymer topology on blend compatibilization, which will be invaluable in designing compatibilized biobased polymer blends as sustainable materials.

The purpose of this study was to investigate the effect of different drying methods on the structure and properties of semicrystalline polymer aerogels. Aerogels, consisting of either globular or strut-like morphologies, were prepared from poly(ether ether ketone) (PEEK) or poly(phenylene sulfide) (PPS) and dried using vacuum drying, freeze-drying, or supercritical CO2 extraction. Vacuum drying was found to result in aerogels with a higher shrinkage, smaller mesopores (with pore widths of 2-50 nm), and smaller surface areas compared to the use of supercritical extraction as the drying method. Freeze-dried aerogels tended to have properties between those of vacuum-dried aerogels and aerogels prepared with supercritical extraction. High network connectivity was found to lead to improved gel modulus, which increased the ability of aerogels to resist network deformation due to stresses induced during drying. The PEEK and PPS aerogel networks consisting of highly connected strut-like features were considerably stiffer than those composed of globular features, and thus shrank less under the forces induced by vacuum drying or freeze-drying. The aerogels prepared from PPS were found to have larger mesopores and smaller surface areas than the aerogels prepared from PEEK. The larger mesopores of the PPS aerogels induced lower capillary stresses on the aerogel network, and thus shrank less. This work demonstrates that preparing PEEK and PPS gels with strut-like features can allow aerogel processing with simpler evaporative drying methods rather than the more complex supercritical drying method.

Perfluorosulfonic acid ionomer (PFSA) dispersions are essential to the coating processes used to fabricate membranes, catalyst layers, and thin films for hydrogen fuel cell and water electrolyzer applications. The PFSA dispersion viscosity can significantly affect coating parameters including wetting, leveling, and compatibility with coating equipment. The effect of PFSA concentration, chemical structure, and solvent composition on dispersion viscosity is examined as a function of five different PFSAs and three different binary alcohol-water solvent systems, using n-propanol, isopropanol, or ethanol as the alcohol. The zero-shear viscosity, η0, is observed to increase with decreasing side chain length, increasing side chain content, and increasing alcohol concentration in the binary alcohol-water solvent. A direct comparison is made between the PFSA colloidal morphology discussed in a previous publication by the present authors and η0. At a fixed, nondilute PFSA concentration, two regimes of weak and strong dependence of η0 on alcohol concentration in the solvent are identified. In the regime where η0 weakly depends on alcohol concentration, an increase in η0 is associated with an increase in the aggregate surface area normalized by side chain content. The orders of magnitude increases in η0 with increasing alcohol concentration in the regime of strong dependence of η0 are attributed to both aggregate morphology and interaggregate ionic associations. By independently considering the PFSA side chain and backbone solubility parameters, two regimes corresponding to relatively favorable solvent-side chain and relatively favorable solvent-backbone interactions are defined as a function of alcohol-water solvent composition. An analysis of PFSA-solvent interaction parameters shows that interaggregate ionic associations occur when solvent-side chain interactions are unfavorable relative to solvent-backbone interactionsfor example, at high alcohol concentrations in the solvent. The alcohol concentration corresponding to the crossover between the weak and strong regimes of η0 is found to agree within ±5 wt % alcohol with the crossover between the regimes of favorable solvent-side chain and favorable solvent-backbone interactions.

The additive manufacturing (AM) method of powder bed fusion (PBF) is especially suited for processing semi- crystalline polymers due to the printer's ability to maintain a build volume temperature to control crystallization rate and shrinkage. In PBF, polymers are rapidly heated by the scanning laser and subsequently cooled to the set powder bed temperature, which yields a complex thermal history for printed materials. In this work, fast scanning calorimetry (FSC) is used as a tool to mimic the rapid thermal transitions experienced during PBF of isotactic polypropylene (iPP) powder in order to gain understanding of how the polymer crystallizes during the printing process. FSC is necessary to study the crystallization behavior of iPP during PBF due to the rapid heating and cooling rates of this process. Utilizing in-situ IR thermography in the PBF system, the heating and cooling rates observed for a single-layer PBF print were used to establish the experimental FSC conditions as a mimic for the PBF process. The isothermal crystallization kinetics and non-isothermal crystallization behavior were also investigated by FSC. The crystallization kinetics of iPP exhibits bimodal parabolic-like behavior with the most rapid crystallization occurring at 30 C-degrees. The non-isothermal crystallization behavior exhibits a transition from the alpha-form polymorph crystallization to mesomorphic crystallization at cooling rates > 40 K/s. It is found that partial melting in the printing process leads to self-seeding and increased crystallization onset temperatures upon cooling. The importance of nucleation from surrounding powder and partially melted crystals on the crystallization kinetics and crystal morphology upon melting during the PBF process is shown via this FSC technique. While iPP serves as a material for this analysis, we have uncovered the ability to capture complex morphology evolution during the PBF process to help enable targeted part design and performance for crystallizable polymers. This is a broadly applicable approach to understand how to mimic PBF of any semi-crystalline polymer using FSC.

C-H functionalization of commodity polyolefins affords functional materials derived from a high-volume, low-cost resource. However, current postpolymerization modification strategies result in randomly distributed functionalization along the length of the polymer backbone, which has a negative impact on the crystallinity of the resultant polymers, and thus the thermomechanical properties. Here, we demonstrate an amidyl radical mediated C-H functionalization of polyolefins to access blocky microstructures, which exhibit a higher crystalline fraction, larger crystallite size, and improved mechanical properties compared to their randomly functionalized analogues. Taking inspiration from the site-selective C-H functionalization of small molecules, we leverage the steric protection provided by crystallites and target polymer functionalization to amorphous domains in a semicrystalline polyolefin gel. The beneficial outcomes of blocky functionalization are independent of the identity of the pendant functional group that is installed through functionalization. The decoupling of functional group incorporation and crystallinity highlights the promise in accessing nonrandom microstructures through selective functionalization to circumvent traditional tradeoffs in postpolymerization modification, with potential impact in advanced materials and upcycling plastic waste.

Ethylene-Propylene-Diene Monomer (EPDM) rubber is recognized for elasticity over a wide temperature range and exceptional resistance to UV light and oxidative degradation. In this study, sulfonated EPDM (sEPDM) latex serves as an innovative platform for 3D printing olefinic elastomers through vat photopolymerization (VPP). The sulfonation of EPDM and subsequent neutralization with potassium hydroxide enabled the production of waterdispersible sEPDM (K-sEPDM), yielding a stable latex with an average particle diameter of 125 nm. The inherent low viscosity of the latexes allowed the direct application of elastomeric polymers during the VPP process. The photopolymerization of a scaffold precursor composition, which consisted of n-vinylpyrrolidone (NVP) and poly (ethylene glycol) diacrylate (PEGDA) in the aqueous phase of K-sEPDM latex, solidified the latex as a particle embedded hydrogel. Post-processing for removing water from the 3D printed green body facilitated coalescence of the K-sEPDM particles throughout the scaffold network, generating a second ionically crosslinked network together with scaffold as an interpenetrating polymer network (IPN). Tensile testing demonstrated tunable elastomeric properties with an ultimate strain from 315+11-453+37 % and ultimate stress from 7.6+0.5-8.2 +0.3 MPa with excellent thermal recoverability. VPP of photocurable K-sEPDM with a commercial printer showcased high-resolution printing capabilities with controllable isotropic shrinkage for the printing of olefinic elastomers.

In an effort to synthesize chemically recyclable thermoplastic elastomers, a redox-switchable catalytic system was developed to synthesize triblock copolymers containing stiff poly(lactic acid) (PLA) end blocks and a flexible poly(tetrahydrofuran- co- cyclohexene oxide) (poly(THF- co -CHO) copolymer as the mid-block. The orthogonal reactivity induced by changing the oxidation state of the iron-based catalyst enabled the synthesis of the triblock copolymers in a single reaction flask from a mixture of monomers. The triblock copolymers demonstrated improved flexibility compared to poly( l -lactic acid) (PLLA) and thermomechanical properties that resemble thermoplastic elastomers, including a rubbery plateau in the range of −60 to 40 °C. The triblock copolymers containing a higher percentage of THF versus CHO were more flexible, and a blend of triblock copolymers containing PLLA and poly( d -lactic acid) (PDLA) end-blocks resulted in a stereocomplex that further increased polymer flexibility. Besides the low cost of lactide and THF, the sustainability of this new class of triblock copolymers was also supported by their depolymerization, which was achieved by exposing the copolymers sequentially to FeCl 3 and ZnCl 2 /PEG under reactive distillation conditions.

Blocky bromination of PEKK yields superior crystallizability, high % X c , T g , T m , T c , and faster crystallization kinetics compared to random analogs.

Poly(ether ether ketone) (PEEK) was found to form gels in the benign solvent 1,3-diphenylacetone (DPA). Gelation of PEEK in DPA was found to form an interconnected, strut-like morphology composed of polymer axialites. To our knowledge, this is the first report of a strut-like morphology for PEEK aerogels. PEEK/DPA gels were prepared by first dissolving PEEK in DPA at 320 °C. Upon cooling to 50 °C, PEEK crystallizes and forms a gel in DPA. The PEEK/DPA phase diagram indicated that phase separation occurs by solid–liquid phase separation, implying that DPA is a good solvent for PEEK. The Flory–Huggins interaction parameter, calculated as χ12 = 0.093 for the PEEK/DPA system, confirmed that DPA is a good solvent for PEEK. PEEK aerogels were prepared by solvent exchanging DPA to water then freeze-drying. PEEK aerogels were found to have densities between 0.09 and 0.25 g/cm3, porosities between 80 and 93%, and surface areas between 200 and 225 m2/g, depending on the initial gel concentration. Using nitrogen adsorption analyses, PEEK aerogels were found to be mesoporous adsorbents, with mesopore sizes of about 8 nm, which formed between stacks of platelike crystalline lamellae. Scanning electron microscopy and X-ray scattering were utilized to elucidate the hierarchical structure of the PEEK aerogels. Morphological analysis found that the PEEK/DPA gels were composed of a highly nucleated network of PEEK axialites (i.e., aggregates of stacked crystalline lamellae). The highly connected axialite network imparted robust mechanical properties on PEEK aerogels, which were found to densify less upon freeze-drying than globular PEEK aerogel counterparts gelled from dichloroacetic acid (DCA) or 4-chlorphenol (4CP). PEEK aerogels formed from DPA were also found to have a modulus–density scaling that was far more efficient in supporting loads than the poorly connected aerogels formed from PEEK/DCA or PEEK/4CP solutions. The strut-like morphology in these new PEEK aerogels also significantly improved the modulus to a degree that is comparable to high-performance crosslinked aerogels based on polyimide and polyurea of comparable densities.

This manuscript describes the synthesis and characterization of guanine and cytosine‐containing supramolecular copolymers, which are inspired from the guanine and cytosine nucleobase pair in deoxyribonucleic acid. Regioselective Michael‐addition allowed the efficient installation of the nucleobases on acrylate‐containing monomers, which enabled the preparation of a series of nucleobase‐functionalized acrylate and n ‐butyl acrylate copolymers using conventional free radical copolymerization. Guanine‐containing copolymers exhibited superior thermal properties, thermomechanical performance, and more defined morphological structure than cytosine‐containing copolymer analogs due to the relatively strong guanine self‐association, thus expanding the potential applications for mechanically reinforced polymeric networks. Blending guanine‐ and cytosine‐containing copolymers formed a supramolecular structure through multiple hydrogen bonding between guanine and cytosine units. The supramolecular blend exhibited intermediate thermomechanical and morphological properties, which suggested that guanine and cytosine units were not fully associated in the random copolymer composition. This work provides valuable fundamental understanding of structure–property‐morphology relationships in acrylic copolymers with the presence of guanine‐cytosine self‐ and complementary interactions, suggesting new understanding in supramolecular design for enhanced mechanical and morphological properties.

Reinforcement of styrene-butadiene rubber/butadiene rubber is achieved by grafting mercapto-functionalized sodium phosphate esters to the rubber during peroxide curing. The size of the anionic phosphate ester moiety is varied by changing the alkyl substituent (ethyl vs octyl) with the intention of modulating the association strength between the grafted ionic dipoles. The concentration of the ionic graft is also varied. These lead to different degrees of reinforcement and dynamic mechanical properties of the vulcanized rubber. The morphologies of ionic aggregates are characterized by transmission electron microscopy (TEM) imaging and X-ray scattering experiments. TEM imaging revealed heterogeneities in the material, which sometimes included the formation of vesicular aggregates with diameters of approximately 20-30 nm. These features are consistent with the radius of gyration calculated from a knee observed in X-ray scattering at scattering vectors below 0.4 nm(-1). Smaller aggregates were analyzed using the Kinning-Thomas liquid-like hard sphere model and were found to be similar in radius (similar to 1.2-1.3 nm), irrespective of the molar volume of the ionic grafts from which they were constituted. However, the number of aggregates per unit volume within the material and the aggregation number are both profoundly affected by such variations. The structural variations of the ionic graft give rise to substantial changes in the tensile properties of the rubber at room temperature. At high temperatures, the differences in the dynamic moduli substantially diminish among the ionically grafted vulcanizates but remain substantial between the vulcanizates with and without ionic grafts. The equilibrium moduli of all vulcanizates converge at 60 degrees C. Possible mechanisms responsible for reinforcement are discussed at various temperatures, time scales, and ionic graft concentrations.