Highly Porous Polymer Structures Fabricated via Rapid Precipitation from Ternary Systems

High Modulus, Strut-like poly(ether ether ketone) Aerogels Produced from a Benign Solvent

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.

Facile construction of gas diode membrane towards in situ gas consumption via coupling two chemical reactions

Controlling the bubbles' behavior on a solid surface is significant for exploring more related applications and thus recently has attracted increased investigations. Based on this, a Janus poly (l-lactic acid) (PLLA) membrane with definitely opposite water wettability in air and opposite bubble wettability underwater was successfully fabricated in this work. The obtained Janus membrane exhibited unidirectional transport for air bubble underwater from the superaerophilic side to superaerophobic side, meanwhile prevented the permeation of water medium from both sides under low pressure. This special membrane was designed to couple two chemical reactions. During the designed chemical reaction process, the feature of bubble unidirectional transport allowed the carbon dioxide (CO₂) produced in one reaction system to transport through the resultant membrane into another reaction system, wherein it could be consumed. Meanwhile, the anti-water-permeation function of the membrane guaranteed that the two chemical reactions could be performed independently. We believe that the present research could broaden the potential applications of membranes with super-wetting character for gas bubbles.

Unique Ivy-Like Morphology Composed of Poly(lactic acid) and Bacterial Cellulose Cryogel

This study examines the unique morphology and properties of enhanced poly(l-lactic acid) (PLLA) monoliths having a bacterial cellulose (BC) framework. Open-porous BC/PLLA monoliths were successfully prepared using thermally induced phase separation (TIPS) and a freeze-drying technique. The BC/PLLA monoliths exhibited a unique ivy-like structure composed of leaf-like PLLA units and a BC fiber network. We demonstrated for the first time that the interpenetrating BC fiber gives PLLA monoliths four times higher compressive strength than the pristine PLLA. Scanning electron microscopy observation and the N₂ adsorption test revealed that the size of PLLA units and the surface area of the monoliths can be manipulated by varying the starting PLLA concentration during the TIPS process. Moreover, the hydrophilicity of the PLLA monoliths was easily controlled by incorporating BC; the neat PLLA monoliths showed a high static water contact angle of as high as 128.8 ± 1.1°, whereas the BC/PLLA monoliths exhibited a much lower contact angle (102.1 ± 1.7°) and greater absorbability to water.