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Zeolitic imidazolate frameworks (ZIFs) are an emerging class of microporous materials that possess an organic flexible scaffold and zeolite-like topology. The catalytic and molecular-separation capabilities of these materials have attracted considerable attention; however, crystal-shape engineering in ZIF materials remains in its infancy. This is the first study to report an effective method for tailoring the near-spherical crystal morphology of ZIF-8 using its leaf-like pseudopolymorph, ZIF-L. A thin, uniform layer of ZIF-8 is formed on ZIF-L through heterogeneous surface growth to produce a ZIF-L@ZIF-8 core-shell nanocomposite. This results in ZIF-8 with a crystal morphology comprising two-dimensional nanoflakes. We characterized the resulting core-shell crystals using a number of solid-state techniques, including powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and nitrogen physisorption. Approximately 16 mass% of ZIF-8 in the core-shell composites heterogeneous surfacely grown on ZIF-L core crystals. We also investigated the effects of zinc salts, which were used as a source of zinc in the formation of the ZIF-L@ZIF-8 core-shell nanocomposites. Finally, we assessed the CO2 adsorption properties of ZIF-8, ZIF-L, and ZIF-L@ZIF-8 core-shell crystals, the results of which were used to deduce the dynamic and equilibrium adsorption characteristics of various microporous ZIF crystals. The core-shell materials present hybridized CO2 uptake and diffusivity of the parent crystals. The proposed method for the synthesis of core-shell nanocomposites using pseudopolymorphic crystals is applicable to other ZIF systems.

Here, we report all-polymer polysiloxane composites that overcome the long-standing processing problems of silica-reinforced silicone rubbers. Polystyrene fillers are dispersed with styrene/dimethylsiloxane symmetric diblock and triblock copolymers that control the filler morphology, filler−matrix interactions, and filler−filler interactions. Surprisingly, the composites not only rival the traditional silica-reinforced polysiloxane in mechanical properties of cured materials but also have better processability and stability than the silica-filled compound before curing. Large amplitude oscillatory shear experiments demonstrate that the triblock copolymer addition strongly affects the rheological properties. We hypothesize that the bridges and entangled loops that were formed by the triblock copolymer can connect different PS domains to provide additional reinforcement. The aging effect that originates from PDMS chain adsorption on the filler particle surface is also avoided because of the thermodynamic repulsion between PS and PDMS phases.

Here we report microphase-separated poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) as a reinforcing filler in PDMS thermosets that overcomes the long-standing problem of aging in the processing of silicareinforced silicone. Surprisingly, PS-b-PDMS reinforced composites display comparable mechanical performance to silica-modified analogs, even though the modulus of PS is much smaller than that of silica and there is no evidence of percolation with respect to the rigid PS domains. We have found that a few unique characteristics contribute to the reinforcing performance of PS-b-PDMS. The strong selfassembly behavior promotes batch-to-batch repeatability by having well-dispersed fillers. The structure and size of the fillers depend on the loading and characteristics of both filler and matrix, along with the shear effect. The reinforcing effect of PS-b-PDMS is mostly brought by the entanglements between the corona layer of the filler and the matrix, rather than the hydrodynamic reinforcement of the PS phase.

Increasing demand for safe, convenient, and affordable packaging has prompted tremendous growth in single-use plastics, with attendant increases in carbon dioxide emissions and environmental waste. This study presents a family of engineering polyesters featuring biobased naphthalate rigid segments. The proposed polyesters can serve as an eco-friendly substitute for existing packaging materials, such as poly­(ethylene terephthalate) (PET). Bio-PET analogs using 2,7-naphthalate-based rigid segments of dimethyl 1,2,3,4-tetrahydronaphthalene-2,7-dicarboxylate (THN) or dimethyl 2,7-naphthalene dicarboxylate (2,7-N) were synthesized via transesterification with ethylene glycol to the bis-hydroxy ester followed by polycondensation. The proposed bionaphthalate polyesters provide unique performance advantages. In experiments, the glass transition temperature of poly­(ethylene THN) was comparable to that of PET (T g = 67.7 °C), and the glass transition temperature of poly­(ethylene 2,7-N) was far higher (T g = 121.8 °C). The thermal stability of poly­(ethylene 2,7-N) far exceeded that of PET, as evidenced by its char yield of 33.4 wt % at 1000 °C. Moreover, the poly­(ethylene 2,7-N) also produced 30% less acetaldehyde under typical processing temperatures at 250–300 °C. Finally, the oxygen permeability values of these naphthalate-based polymers were less than P O2 = 0.0034 barrer, which represents a 3-fold improvement over PET (0.0108 barrer). Overall, biobased naphthalate rigid segment polyesters are promising candidates for sustainable packaging materials, particularly those requiring high gas barrier performance.

Herein, 3D printable polymer-toughened epoxy resin composites are reported. Epoxy resins are widely used due to their excellent properties, such as thermal and chemical stability. However, their applications are limited by traditional mold-based manufacturing and their high brittleness. Mixtures of homopolymers, diblock copolymers, and triblock copolymers composed of poly­(phenylene ether), poly­(styrene), poly­(methyl methacrylate), and poly­(ethylene oxide) that self-assemble into micelles in the uncured resin are employed, providing a balance of structure, creep resistance, and flowability that enables 3D printing processing techniques and retention of shape from the time of printing throughout the cured state. The precured ink is solid at room temperature and has strong shear-thinning behavior at elevated temperature for printing. As the printed parts cure, the polymer morphology evolves via reaction-induced phase separation to yield finished composites with enhanced mechanical properties, including a 40% increase in the impact strength compared to the neat epoxy, without compromising thermal properties.

Here we present an approach for developing the next generation of bio(meth)acrylates using glycerol ketals as a platform for property differentiation. Crude glycerol, a biodiesel byproduct, and ketones, derived from biomass valorization, are the building blocks for these polymeric materials. Biobased materials are witnessing a prominent boom in research and commercialization due to increased awareness about the carbon footprint and depletion of petroleum resources. Biodiesel and biopolymers are major linchpins to improve sustainable energy and material needs of the world in the coming years. Glycerol ketal (meth)acrylate monomers synthesized by the reaction of glycerol and various ketones consist 65-74 wt.% bioderived content. Glycerol ketals from different ketones used in our study (acetone, cyclopentanone and butanone) are the pendant groups on the (meth)acrylate polymer backbone. We studied the effect of various pendant side-chain ketal groups on the thermal and rheological properties of 1 these polymers. The methacrylate polymers had a higher glass transition temperature (T g ) (8-40 • C) while the acrylate derivatives had much lower T g between -11 • C to 2 • C. The side chain group on these polymers offers us a robust knob to tune the thermal properties (e.g. T g ) and rheological properties (e.g. modulus and entanglement behaviour) for varied applications such as hard block polymers and adhesives.