Seung-Sock Choi

Cationically photopolymerizable epoxy-functionalized thermoplastic polysilsesquioxanes: synthesis and properties

A series of epoxy-functionalized inorganic–organic hybrid ladder-like structured polysilsesquioxanes were synthesized in one-batch via a base-catalyzed co-solvent system. Two types of epoxy functionalities were examined: aliphatic and cycloaliphatic. Obtained polymeric epoxy-functionalized ladder-like polysilsesquioxanes were cationically photopolymerized under UV irradiation over glass and plastic substrates. Obtained cross-linked films were examined as hardcoating materials as their thermal, optical, mechanical, and barrier properties were studied. These materials showed superior thermal properties (Td > 400 °C), high optical transparency (>95%), high pencil hardness (4H–9H), low dielectric constant (3.0–3.6), and good barrier properties (WVTR < 101 g m−2 day−1, OTR < 102 g m−2 day−1).

Thiol-Ene photopolymerization of well-defined hybrid graft polymers from a ladder-like polysilsesquioxane

AbstractA ladder-like structured poly(mercaptopropyl)silsesquioxane (LPMPSQ) was synthesized in one-bath, under mildly basic conditions at room temperature. Obtained LPMPSQ was utilized as a macroinitiator for thiol-ene graft photopolymerization of various vinyl monomers to give hard, soft, hydrophobic, and hydrophilic graft copolymers with low PDI (<1.4). Synthesized hybrid graft copolymers were characterized by 1H NMR, 29Si NMR, FTIR, GPC, TGA, and DSC. Thermal studies with these hybrid graft copolymers revealed that the ladder-structure substantially increased the thermal stabilities in the form of increased glass transition temperatures and higher degradation temperatures over their organic analogues.

Incompletely condensed POSS-based spin-on-glass networks for impeccable ultra low-k integration

Poly(methyl)silsesquioxane-based spin-on-glass resins incorporating both a cyclic precursor, 1,3,5,7-tetramethyl 1,3,5,7-tetrahydroxyl cyclosiloxane, and incompletely condensed methyl-substituted POSS were synthesized and their thermal, mechanical, and electrical properties were investigated as a function of the POSS loading content. By introducing incompletely condensed methyl-substituted POSS compounds at the molecular level as sol–gel precursors, exceptional thermal stability (>700 °C), good mechanical properties (elastic modulus >4.0 GPa), and an ultra-low dielectric constant (k = 1.8) were obtained. In addition to providing a new route towards fully poly(methyl)silsesquioxane-based spin-on-glass resins with the above properties, the realization of the application of integration circuits was evaluated to show that the ultra low-k, mechanically robust spin-on-glass materials were able to withstand harsh wet chemical and dry etching, as well as chemical mechanical planarization (CMP) processing.

Structural analysis of high molecular weight PMSQs and their related properties for interlayer dielectric (ILD) application

AbstractA series of high molecular weight polymethylsilsesquioxanes (PMSQs) were synthesized through polymerization of an isolated hydroxyl-substituted cyclic siloxane stereoisomer, cis-trans-cis 1,3,5,7 tetramethyl 1,3,5,7 tetrahydroxyl cyclosiloxane, for interlayer dielectric (ILD) application as low dielectric materials. The molecular weights of PMSQs were controlled by varying polycondensation time. Structural analyses of the obtained PMSQs were carried out by gel chromatography (GPC), FTIR, 29Si NMR, static light scattering (SLS), solution X-ray scattering, and X-ray diffraction. The change in molecular shape of the PMSQs went from linear to branched in structure as molecular weight increased. Furthermore, thin film properties were investigated for application as interlayer dielectric materials. As structural branching increased, its properties showed isotropic tendencies, relatively high modulus (5.4 GPa), and low dielectric constant (2.74) with increase in the inter-molecular space.

Robust spin-on-glass poly(methyl)silsesquioxane-based low-k materials derived from a cyclic siloxane precursor

A series of organic–inorganic hybrid spin-on-glass polymethylsilsesquioxanes were synthesized utilizing a cyclic siloxane precursor, 1,3,5,7-tetramethyl-1,3,5,7-tetrahydroxyl cyclosiloxane (MT4-OH), copolymerized with methyltriethoxysilane (MTES) at various comonomer ratios. By selectively introducing this 2-D cyclic crosslinker, we were able to obtain spin-on-glass hybrimers with low dielectric constant (2.5–2.7), high nanoindentation modulus (5–10.5 GPa), with high thermal stability (>700 °C) without the use of porogens or additives. The use of the cyclic monomer MT4-OH greatly increased the mechanical properties, which allowed for impeccable reliability of a variety of patterns obtained through etching and chemical mechanical planarization processes, while maintaining optimal gap-filling properties. Due to the superior dielectric, mechanical, and integrated processing of these materials, these hybrids derived from MT4-OH may be utilized as next generation spin-on-glass low-dielectric constant materials.

Preparation of high modulus thin films based on photocurable azido-functionalized ladder-like structured polysilsesquioxanes

A series of azido-functionalized ladder-like structures was prepared by direct azidation of ladder-like structured poly(p-chloromethylphenyl)silsesquioxane (LPCMPSQ) and poly(chloropropyl)silsesquioxane (LPAPSQ) in excellent yields with perfect substitution of the chloro-compounds. The azido-functionalized silsesquioxanes obtained were then photocured without additional photoinitiator to give highly cross-linked thin films with an exceptionally high modulus (> 12 GPa). Furthermore, these materials were shown to be patterned through photolithography to give impeccable micropatterned microstructures.

Synthesis and Characterization of Azido-Substituted Ladder-like Polysilsesquioxanes and their Click Chemistry

A novel organic-inorganic hybrid-type ladder-like poly(benzylazide) silsesquioxane (LPBAzSQ) and ladder-like poly(propylazide) silsesquioxane (LPPAzSQ) were synthesized through azidation of ladder-like poly(p-chloromethyl)phenylsilsesquioxane (LPCMPSQ) and ladder-like poly(propylchloro)silsesquioxane (LPPCSQ). The ladder-like structure of the synthesized LPBAzSQ and LPPAzSQ compounds, full substitution of azide groups, and their click chemistry with various functional groups was characterized by 1H NMR, 13C NMR, 29Si NMR, FT-IR, GPC. This new approach for functionalization of ladder-like silsesquioxanes has allowed for insertion of polar functional groups that have yet be examined in silsesquioxane chemistry.

Physical Properties of Polymethylsilsesquioxane with UV-Curable Group for Low-Loss Optical Materials

Polymethylsilsesquioxane(PMSQ)s with photo-curable groups were prepared by copolymerization of alkoxysilanes. Poly(acryloyl-co-methylsilsesquioxane)(PAMSQ)s of various mole ratio acryloyl group (6 mol%, 12 mol%, 24 mol%, 48 mol%, 100 mol%) were obtained from copolymerization of methyltrimethoxylsilane and 3-(trimethoxysilyl)propyl acrylate. Optical and photonic curable properties were studied by near infrared region spectra, prism coupler, UV-visible spectra, and photo-DSC. The optical losses were below 0.002 dB/cm at 830, 1330, and 1550 nm, respectively. Optical loss was found to be independent of a molar ratio of functional group.