Nanoporous thin films, a promising candidate of spin-on ultralow dielectrics for microelectronic applications, have been fabricated via thermally sacrificing a new pore generator octa(2,4-dinitrophenyl)silsesquioxane (ODNPSQ) in a higher molecular weight (M-w = 30 872) polyphenylsilsesquioxane (PPSQ) matrix. The organic-inorganic hybrid ODNPSQ exhibits a core-shell structure (one cubic Si8O12 core covered by eight dinitrophenyl groups as shell) with high decomposition temperature at similar to 420 degrees C. PPSQ holds a chain molecular structure consisting of numbered ladderlike and partial T-12 cagelike repeating units, which could be thermally bonded first via an intermolecular condensation reaction, forming two-dimensional sheets, and then further linked by sharing oxygen atoms, generating a highly cross-linked three-dimensional framework by curing at 450 degrees C, featuring a single strong FT-IR symmetrical Si-O-Si stretching frequency at 1132 cm(-1). Nanopores in PPSQ matrix are imprinted by sacrificing ODNPSQ porogen curing at 450 degrees C. FT-IR is used to study the interaction and structure changes of PPSQ precursor as a function of curing temperature (ranging from 25 to 500 degrees C) and porogen loading (ranging from 0 to 40 wt %), and a hydrophilic porogen Tween-20 was also used as a reference to carry out a comparative study with the ODNPSQ porogen. Because of phase separation, the amphiphilic PPSQ precursor has a saturated miscibility with the hydrophilic Tween-20 at 30% porogen loading after curing. However, PPSQ gives a better compatibility with the lipophilic ODNPSQ porogen over 40% porogen loading after curing, and the resulting porous spin-on thin films showed low water absorption (0.45%) and low dielectric constant (1.93).