Ultralow-dielectric, nanoporous poly(methyl silsesquioxanes) films templated by a self-assembled block copolymer upon solvent annealing
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A homogenous, nanoporous poly(methyl silsesquixoxane) (PMSSQ) with a uniform pore size distribution was prepared by templating with a poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymer. The self-assembly of the PS-b-P4VP and PMSSQ precursor (PMSSQ-P) blends thin films was achieved by solvent annealing firstly; then the self-assembled thin films were thermally cured to prepare nanoporous PMSSQ films after removal of the PS-b-P4VP porogen. The influence of annealing solvent and PS-b-P4VP loading on the self-assembly behavior of the PS-b-P4VP/PMSSQ-P blends films were studied. By exposing to CHCl3 vapor, fingerprint-type microphase-separated structures were achieved for the PS-b-P4VP/PMSSQ-P blends films with PS-b-P4VP loading ranging from 30% to 60%. The formation of the microphase-separated structures is attributed to the substantial mobility of the PS blocks and the P4VP/PMSSQ-P complexes, and segregated repulsion between them under the CHCl3 vapor. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) results demonstrated the prepared nanoporous PMSSQ films had a homogenous spherical pore morphology, with closed nanopores and a uniform size distribution over large areas. The porosity and dielectric properties of the homogenous, nanoporous PMSSQ could be adjusted by the content of PS-b-P4VP in the PS-b-P4VP/PMSSQ-P blends. As the PS-b-P4VP loading increased to 60 wt%, an ultralow dielectric constant of 1.41 was obtained, making the nanoporous PMSSQ films have potential applications in microelectronic devices.
KeywordsBlock copolymers Dielectric constant Nanoporous Poly(methyl silsesquixoxane) Solvent annealing
The authors would like to acknowledge the financial support of the Nature Science Foundation of China (NSFC) (Grant No. 51403219), National Natural Science Foundation of China-Aerospace Science and Technology Corporation of China Aerospace Advanced Manufacturing Technology Research Joint Fund (U1637205), and Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms (BZ0388201701).
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