From Flexible to Hard Polyurethane Aerogels: The Effect of Molecular Functionality vs. Molecular Rigidity

摘要: High performance all-polymer aerogels are not only interesting for their low thermal conductivity, but also mechanical strength and conversion to porous carbons. The prevalent design rule dictates that crosslinking at the monomer level decreases solubility of developing polymer induces phase separation nanoparticles with high surface volume ratios. Hence, hyperbranched structures based on trifunctional single aromatic core monomers should have enhanced interparticle connectivity rigidity compared those either difunctional or multiple monomers. That is applied here polyurethane (PU) synthesized from tris(4-isocyanatophenyl)methane ( TIPM ) 1,1,1-tris(4-hydroxyphenyl)ethane HPE in anhydrous acetone using dibutyltin dilaurate (DBTDL) as catalyst. resulting materials vary highly flexible rigid concentration increases. FTIR 13 C solid NMR confirm formation urethane. SEM shows variety macroporous a beaded worm-like structure, while mesoporous nanoparticulate. Lower-density (92%) area 132 m 2 g -1 , ones higher areas, up 256 . Polyurethane other triols diols, e.g., phloroglucinol POL resorcinol RES ), respectively, been studied similar concentrations shrinkage bulk density