Spiering Glenn A, Godshall Garrett F, Moore Robert B
Department of Chemistry, Macromolecules Innovation Institute, Virginia Tech, Blacksburg, VA 24061, USA.
Gels. 2025 Jun 10;11(6):447. doi: 10.3390/gels11060447.
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 CO 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.
本研究的目的是探究不同干燥方法对半结晶聚合物气凝胶结构和性能的影响。由聚醚醚酮（PEEK）或聚苯硫醚（PPS）制备的具有球状或柱状形态的气凝胶，采用真空干燥、冷冻干燥或超临界CO₂萃取进行干燥。结果发现，与使用超临界萃取作为干燥方法相比，真空干燥导致气凝胶收缩率更高、中孔更小（孔径为2 - 50 nm）且表面积更小。冷冻干燥的气凝胶的性能往往介于真空干燥的气凝胶和用超临界萃取制备的气凝胶之间。发现高网络连通性会提高凝胶模量，这增强了气凝胶抵抗干燥过程中产生的应力引起的网络变形的能力。由高度连接的柱状特征组成的PEEK和PPS气凝胶网络比由球状特征组成的网络刚度大得多，因此在真空干燥或冷冻干燥产生的力作用下收缩较小。发现由PPS制备的气凝胶比由PEEK制备的气凝胶具有更大的中孔和更小的表面积。PPS气凝胶较大的中孔在气凝胶网络上产生较低的毛细应力，因此收缩较小。这项工作表明，制备具有柱状特征的PEEK和PPS凝胶可以采用更简单的蒸发干燥方法而非更复杂的超临界干燥方法来进行气凝胶加工。
