Strategic Growth Area: Economical and Sustainable Materials (ESM)

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Amphiphilic hydroxyalkyl cellulose derivatives for amorphous solid dispersion prepared by olefin cross-metathesis
Dong, Yifan; Mosquera-Giraldo, Laura I.; Troutman, Jacob; Skogstad, Brittny; Taylor, Lynne S.; Edgar, Kevin J. (Royal Society of Chemistry, 2016-07-07)
Olefin cross-metathesis (CM) has enabled design and synthesis of diverse, amphiphilic cellulose ether derivatives (e.g. of ethyl and methyl cellulose). In this paper, hydroxyalkyl cellulose was selected as a hydrophilic starting material, with the additional advantage that it has DS (OH) 3.0 that allows targeting of a full range of DS of selected functional groups. Hydroxypropyl cellulose (HPC) was first etherified with 5-bromopent-1-ene to attach olefin “handles” for metathesis, whereby control of molar ratios of sodium hydride and 5-bromopent-1-ene permits full DS control of appended olefin. These olefin-terminated HPC ethers then were subjected to CM with acrylic acid and different acrylates, followed by diimide hydrogenation to reduce the resulting α,β-unsaturation. NMR and FT-IR spectroscopies were useful tools for following reaction progress. One of the product carboxyl-functionalized HPC derivatives, designated HPC-Pen106-AA-H, showed high promise as a crystallization inhibitor of the antiviral drug telaprevir. Its nucleation-induction inhibitory ability was compared to those of commercial controls, HPC and HPMCAS. All three polymers were very effective for inhibiting telaprevir crystallization, increasing induction time up to 8-fold. HPC did not effectively prevent amorphous particle growth, whereas the carboxyl-containing HPC-Pen106-AA-H and HPMCAS were able to prevent formation of agglomerates of amorphous drugs.
Biodegradable Poly(Lactic Acid) Nanocomposites for Fused Deposition Modeling 3D Printing
Bardot, Madison; Schulz, Michael D. (MDPI, 2020-12-21)
3D printing by fused deposition modelling (FDM) enables rapid prototyping and fabrication of parts with complex geometries. Unfortunately, most materials suitable for FDM 3D printing are non-degradable, petroleum-based polymers. The current ecological crisis caused by plastic waste has produced great interest in biodegradable materials for many applications, including 3D printing. Poly(lactic acid) (PLA), in particular, has been extensively investigated for FDM applications. However, most biodegradable polymers, including PLA, have insufficient mechanical properties for many applications. One approach to overcoming this challenge is to introduce additives that enhance the mechanical properties of PLA while maintaining FDM 3D printability. This review focuses on PLA-based nanocomposites with cellulose, metal-based nanoparticles, continuous fibers, carbon-based nanoparticles, or other additives. These additives impact both the physical properties and printability of the resulting nanocomposites. We also detail the optimal conditions for using these materials in FDM 3D printing. These approaches demonstrate the promise of developing nanocomposites that are both biodegradable and mechanically robust.
Development of Recyclable and High-Performance In Situ Hybrid TLCP/Glass Fiber Composites
Chen, Tianran; Kazerooni, Dana; Ju, Lin; Okonski, David A.; Baird, Donald G. (MDPI, 2020-08-24)
By combining the concepts of in situ thermotropic liquid crystalline polymer (TLCP) composites and conventional fiber composites, a recyclable and high-performance in situ hybrid polypropylene-based composite was successfully developed. The recycled hybrid composite was prepared by injection molding and grinding processes. Rheological and thermal analyses were utilized to optimize the processing temperature of the injection molding process to reduce the melt viscosity and minimize the degradation of polypropylene. The ideal temperature for blending the hybrid composite was found to be 305 °C. The influence of mechanical recycling on the different combinations of TLCP and glass fiber composites was analyzed. When the weight fraction ratio of TLCP to glass fiber was 2 to 1, the hybrid composite exhibited better processability, improved tensile performance, lower mechanical anisotropy, and greater recyclability compared to the polypropylene reinforced by either glass fiber or TLCP alone.
Double helical conformation and extreme rigidity in a rodlike polyelectrolyte
Wang, Ying; He, Yadong; Yu, Zhou; Gao, Jianwei; ten Brinck, Stephanie; Slebodnick, Carla; Fahs, Gregory B.; Zanelotti, Curt J.; Hegde, Maruti; Moore, Robert Bowen; Ensing, Bernd; Dingemans, Theo J.; Qiao, Rui; Madsen, Louis A. (Nature Publishing Group, 2019-02-18)
The ubiquitous biomacromolecule DNA has an axial rigidity persistence length of ~50 nm, driven by its elegant double helical structure. While double and multiple helix structures appear widely in nature, only rarely are these found in synthetic non-chiral macromolecules. Here we report a double helical conformation in the densely charged aromatic polyamide poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) or PBDT. This double helix macromolecule represents one of the most rigid simple molecular structures known, exhibiting an extremely high axial persistence length (~1 micrometer). We present X-ray diffraction, NMR spectroscopy, and molecular dynamics (MD) simulations that reveal and confirm the double helical conformation. The discovery of this extreme rigidity in combination with high charge density gives insight into the self-assembly of molecular ionic composites with high mechanical modulus (~ 1 GPa) yet with liquid-like ion motions inside, and provides fodder for formation of other 1D-reinforced composites. © 2019, The Author(s).
Exceptional capacitive deionization rate and capacity by block copolymer–based porous carbon fibers
Liu, Tianyu; Serrano, Joel; Elliott, John; Yang, Xiaozhou; Cathcart, William; Wang, Zixuan; He, Zhen; Liu, Guoliang (American Association for the Advancement of Science, 2020-04-17)
Capacitive deionization (CDI) is energetically favorable for desalinating low-salinity water. The bottlenecks of current carbon-based CDI materials are their limited desalination capacities and time-consuming cycles, caused by insufficient ion-accessible surfaces and retarded electron/ion transport. Here, we demonstrate porous carbon fibers (PCFs) derived from microphase-separated poly(methyl methacrylate)-block-polyacrylonitrile (PMMA-b-PAN) as an effective CDI material. PCF has abundant and uniform mesopores that are interconnected with micropores. This hierarchical porous structure renders PCF a large ion-accessible surface area and a high desalination capacity. In addition, the continuous carbon fibers and interconnected porous network enable fast electron/ion transport, and hence a high desalination rate. PCF shows desalination capacity of 30 mgNaCl g⁻¹ PCF and maximal time-average desalination rate of 38.0 mgNaCl g⁻¹ PCF min⁻¹, which are about 3 and 40 times, respectively, those of typical porous carbons. Our work underlines the promise of block copolymer–based PCF for mutually high-capacity and high-rate CDI.
Folic Acid-Conjugated Cellulose Nanocrystals Show High Folate-Receptor Binding Affinity and Uptake by KB and Breast Cancer Cells
Bittleman, Katelyn Rose; Dong, Shuping; Roman, Maren; Lee, Yong Woo (American Chemical Society, 2018-10-24)
The study evaluates cellulose nanocrystals (CNCs) as nanocarriers for targeted, intracellular delivery of molecular agents. CNCs were labeled with fluorescein-5′-isothiocyanate as an imaging agent and conjugated to folic acid (FA) as a targeting ligand. The CNC conjugates were characterized by UV–vis spectroscopy, ζ-potential analysis, dynamic light scattering, and atomic force microscopy. Cellular binding/uptake of the FA-conjugated CNCs by KB and MDA-MB-468 cells was quantified with cellular uptake assays. Internalization of the particles was confirmed by confocal microscopy. Uptake mechanisms were determined by inhibition studies with chlorpromazine and genistein. Binding affinity was qualitatively assessed with a free folate inhibition assay. Both KB and MDA-MB-468 cells exhibited significant and folate-receptor specific binding/uptake of FA-conjugated CNCs. Clathrin-mediated endocytosis was a significant uptake mechanism in both cell types, whereas caveolae-mediated endocytosis only played a significant role in MDA-MB-468 cells. Uptake inhibition of FA-conjugated CNCs by KB cells required high concentrations (>1 mM) of free FA. The observed FR-specific internalization of FA-conjugated CNCs by FR-positive cancer cells and tumors and their remarkable high affinity for the FR demonstrate the great potential of CNCs as novel nanocarriers for imaging agents and chemotherapeutics in the early detection and treatment of cancer.
Imparting functional variety to cellulose ethers via olefin cross-metathesis
Dong, Yifan; Edgar, Kevin J. (The Royal Society of Chemistry, 2015-04-09)
Olefin cross-metathesis is a valuable new approach for imparting functional variety to cellulose ethers. Starting from commercially available ethyl cellulose, terminally unsaturated alkyl groups were appended as metathesis handles by reaction with allyl chloride, 5-bromo-1-pentene, 7-bromo-1-heptene and 11-bromo-1-undecene, employing sodium hydride catalyst. These olefin-terminal ethyl cellulose derivatives were then subjected to olefin cross-metathesis with a variety of electron-poor olefin substrates, including acrylic acid and acrylate esters under optimized conditions (5–10 mol% Hoveyda-Grubbs’ 2nd generation catalyst, 37 °C, 2 h). The effects of varying the length of the ω-unsaturated alkyl handle, and of the solvent systems used were evaluated. Ethyl cellulose containing a pent-4-enyl substituent performed best in cross metathesis reactions and a hept-6-enyl substituent gave similarly good results. Ethyl cellulose with allyl substituents gave low to moderate metathesis conversion (<50%), possibly due to steric effects and the proximity of the ether oxygen to the terminal olefin. Interestingly, longer tethers (undec-10-enyl) gave high conversions (up to 90%) but relatively slow reactions (ca. 12 h needed for high conversion). While limited in this study by the relatively low DS (OH) of the starting commercial ethyl cellulose materials, this methodology has strong promise for introduction of diverse functionality to cellulose ethers in chemospecific and mild fashion, enabling amorphous solid dispersion and other applications.
Influence of nucleobase stoichiometry on the self-assembly of ABC triblock copolymers
Zhang, Keren; Talley, Samantha J.; Yu, Ya Peng; Moore, Robert Bowen; Murayama, Mitsuhiro; Long, Timothy E. (Royal Society of Chemistry, 2016-05-11)
ABC triblock copolymers bearing adenine- and thymine-functionalized external blocks self-assembled into long-range, ordered lamellar microphase-separated morphologies on non-patterned substrates. Intermolecular hydrogen bonding formed thymine–adenine triplets and promoted self-assembly into well-defined lamellae consisting of poly(n-butyl acrylate) soft domains and complementary nucleobase hard domains, while thymine–adenine duplets contributed to superior mechanical properties.
Mitigation of bidirectional solute flux in forward osmosis via membrane surface coating of zwitterion functionalized carbon nanotubes
Zou, Shiqiang; Smith, Ethan D.; Lin, Shihong; Martin, Stephen M.; He, Zhen (Elsevier, 2019-07-08)
Forward osmosis (FO) has emerged as a promising membrane technology to yield high-quality reusable water from various water sources. A key challenge to be solved is the bidirectional solute flux (BSF), including reverse solute flux (RSF) and forward solute flux (FSF). Herein, zwitterion functionalized carbon nanotubes (Z-CNTs) have been coated onto a commercial thin film composite (TFC) membrane, resulting in BSF mitigation via both electrostatic repulsion forces induced by zwitterionic functional groups and steric interactions with CNTs. At a coating density of 0.97 gm⁻², a significantly reduced specific RSF was observed for multiple draw solutes, including NaCl (55.5% reduction), NH₄H₂PO₄(83.8%), (NH₄)₂HPO₄ (74.5%), NH₄Cl (70.8%), and NH₄HCO₃ (61.9%). When a synthetic wastewater was applied as the feed to investigate membrane rejection, FSF was notably reduced by using the coated membrane with fewer pollutants leaked to the draw solution, including NH₄⁺-N (46.3% reduction), NO₂⁻₋N (37.0%), NO₂⁻₋N (30.3%), K⁺ (56.1%), PO₄³⁻₋P (100%), and Mg²⁺ (100%). When fed with real wastewater, a consistent water flux was achieved during semi-continuous operation with enhanced fouling resistance. This study is among the earliest efforts to address BSF control via membrane modification, and the results will encourage further exploration of effective strategies to reduce BSF.
Multifunctional cellulose esters by olefin cross-metathesis and thiol-Michael addition
Meng, Xiangtao; Roy Choudhury, Shreya; Edgar, Kevin J. (Royal Society of Chemistry, 2016-04-25)
Olefin cross-metathesis (CM) has been shown to be a versatile, mild, modular, and efficient approach to polysaccharide modification. One issue with regard to this approach is the susceptibility of the initial α,β-unsaturated CM derivatives to H-atom abstraction in the γ-position, followed by radical recombination that leads to insoluble, crosslinked products. In our original approach, we resolved this problem through removing the offending unsaturation by hydrogenation. In the current study, we describe a method to exploit these reactive conjugated olefins, by post-CM thiol-Michael addition, thereby appending additional functionality. CM substrates and thiols bearing various functional groups were combined and reacted, employing amine catalysis. Up to 100% conversion was achieved under proper conditions (e.g. catalyst and reaction time), with minimal side reactions observed. The combination of the two modular reactions creates versatile access to cellulose derivatives equipped with a wide diversity of functional groups.
Non-isocyanate poly(amide-hydroxyurethane)s from sustainable resources
Zhang, Keren; Nelson, Ashley M.; Talley, Samantha J.; Chen, Mingtao; Margaretta, Evan; Hudson, Amanda G.; Moore, Robert Bowen; Long, Timothy E. (Royal Society of Chemistry, 2016-05-19)
A two-step synthesis of epoxidation and carbonation afforded a hetero-functional AB monomer with cyclic carbonate and methyl ester (CC-ME) using plant oil-based methyl 9-decenoate and CO2. A unprecedented one-pot synthetic platform of CC-ME with 1,12-diaminododecane and poly(tetramethylene oxide) (PTMO)-based polyether diamine allowed synthesis of both nonsegmented poly(amide-hydroxyurethane) (PA12HU) and segmented PA12HU-PTMOs with varying polyether contents. 1H NMR spectroscopy confirmed complete conversion of cyclic carbonates and methyl esters to hydroxyurethanes and amides, respectively. Thermal analysis revealed distinctive thermal stability and transitions of PA12HU and PA12HU-PTMOs compared to their precursors and model oligomers. PA12HU and PA12HU-PTMOs were melt compression molded into semicrystalline, free-standing films, except for PA12HU-PTMO100 with 100% polyether diamine. PA12HU-PTMO100 was a viscous liquid with a glass transition temperature (Tg) of −64 °C and zero-shear melt viscosity of 449 Pa s. PA12HU formed a semicrystalline, rigid film with Tg of 11 °C. Polyether incorporation afforded creasable PA12HU-PTMO films with broad glass transitions near −50 °C. Thermal and thermomechanical analysis revealed significant phase-mixing of the hard and soft segments from annealed PA12HU-PTMO films. Polyether soft segments mixed with the amorphous hard segments, forming a miscible soft phase; crystallizable hard segments with ordered hydrogen bonding formed a hard phase. Surface morphological analysis of each PA12HU-PTMO film displayed ribbon-like, hard domains with composition-dependent aspect ratios. PA12HU-PTMOs exhibited higher moisture uptake than traditional thermoplastic polyurethane (TPU) due to resultant hydroxyls. Variable temperature FTIR spectroscopy demonstrated that ordered hydrogen bonding in the crystalline domains was disrupted or dissociated as the crystallites melted. Although tensile strength of segmented PA12HU-PTMOs proved lower than traditional polyurethanes due to phase-mixing, these compositions represent the first examples of film-forming, linear isocyanate-free polyurethanes with mechanical integrity and processability.
Novel Electrospun Pullulan Fibers Incorporating Hydroxypropyl-β-Cyclodextrin: Morphology and Relation with Rheological Properties
Poudel, Deepak; Swilley-Sanchez, Sarah; O'Keefe, Sean F.; Matson, John B.; Long, Timothy E.; Fernández-Fraguas, Cristina (MDPI, 2020-10-31)
Fibers produced by electrospinning from biocompatible, biodegradable and naturally occurring polymers have potential advantages in drug delivery and biomedical applications because of their unique functionalities. Here, electrospun submicron fibers were produced from mixtures containing an exopolysaccharide (pullulan) and a small molecule with hosting abilities, hydroxypropyl-β-cyclodextrin (HP-β-CD), thus serving as multi-functional blend. The procedure used water as sole solvent and excluded synthetic polymers. Rheological characterization was performed to evaluate the impact of HP-β-CD on pullulan entanglement concentration (C_E); the relationship with electrospinnability and fiber morphology was investigated. Neat pullulan solutions required three times C_E (~20% w/v pullulan) for effective electrospinning and formation of bead-free nanofibers. HP-β-CD (30% w/v) facilitated electrospinning, leading to the production of continuous, beadless fibers (average diameters: 853-1019 nm) at lower polymer concentrations than those required in neat pullulan systems, without significantly shifting the polymer C_E. Rheological, Differential Scanning Calorimetry (DSC) and Dynamic Light Scattering (DLS) measurements suggested that electrospinnability improvement was due to HP-β-CD assisting in pullulan entanglement, probably acting as a crosslinker. Yet, the type of association was not clearly identified. This study shows that blending pullulan with HP-β-CD offers a platform to exploit the inherent properties and advantages of both components in encapsulation applications.
Oil-Impregnated Hydrocarbon-Based Polymer Films
Mukherjee, Ranit; Habibi, Mohammad; Rashed, Ziad T.; Berbert, Otacilio; Shi, Xiangke; Boreyko, Jonathan B. (Springer Nature, 2018-08-03)
Porous surfaces impregnated with a liquid lubricant exhibit minimal contact angle hysteresis with immiscible test liquids, rendering them ideal as self-cleaning materials. Rather than roughening a solid substrate, an increasingly popular choice is to use an absorbent polymer as the "porous" material. However, to date the polymer choices have been limited to expensive silicone-based polymers or complex assemblies of polymer multilayers on functionalized surfaces. In this paper, we show that hydrocarbon-based polymer films such as polyethylene can be stably impregnated with chemically compatible vegetable oils, without requiring any surface treatment. These oil-impregnated hydrocarbon-based films exhibit minimal contact angle hysteresis for a wide variety of test products including water, ketchup, and yogurt. Our oil-impregnated films remain slippery even after several weeks of being submerged in ketchup, illustrating their extreme durability. We expect that the simple and cost-effective nature of our slippery hydrocarbon-based films will make them useful for industrial packaging applications.
Porous organic materials offer vast future opportunities
Liu, Tianyu; Liu, Guoliang (2020-10-02)
In light of the surging research on porous organic materials, we herein discuss the key issues of their porous structures, surface properties, and end functions. We also present an outlook on emerging opportunities, new applications, and data science-assisted materials discovery.
Prediction of Young’s Modulus for Injection Molded Long Fiber Reinforced Thermoplastics
Chen, Hongyu; Baird, Donald G. (MDPI, 2018-08-06)
In this article, the elastic properties of long-fiber injection-molded thermoplastics (LFTs) are investigated by micro-mechanical approaches including the Halpin-Tsai (HT) model and the Mori-Tanaka model based on Eshelby’s equivalent inclusion (EMT). In the modeling, the elastic properties are calculated by the fiber content, fiber length, and fiber orientation. Several closure approximations for the fourth-order fiber orientation tensor are evaluated by comparing the as-calculated elastic stiffness with that from the original experimental fourth-order tensor. An empirical model was developed to correct the fibers’ aspect ratio in the computation for the actual as-formed LFTs with fiber bundles under high fiber content. After the correction, the analytical predictions had good agreement with the experimental stiffness values from tensile tests on the LFTs. Our analysis shows that it is essential to incorporate the effect of the presence of fiber bundles to accurately predict the composite properties. This work involved the use of experimental values of fiber orientation and serves as the basis for computing part stiffness as a function of mold filling conditions. The work also explains why the modulus tends to level off with fiber concentration.

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