Fabrication and Evolution of Mesostructures in Fluorinated Organosilicate Mesoporous Thin Films

1. FnC FnC FnC Fluorinated Mesoporous Silica Mesoporous F68 CFn P123 (Hexa) OH OH F68 (Cubic) OH F68 91 nm OH OH OH Substrate Substrate CTACl 20nm 20nm 20nm 20nm P123 (Hexa) HO OH HO OH OH HO Substrate 133 nm CTACl 100 nm 5 10 15 20 25 30 35 40 45 Substrate [Surfactants] / [Silanes] Hexagonal Cubic Lamellar Cubic 3-FPTMS 13-FOTES 17-FDTMS PEO-PPO-PEO triblock copolymer Surfactant concentration increase Hydrophilic head group PEO : Hydrophilic (water-soluble) Pluronic F68 (N=153, M=29) PPO : Hydrophobic (water-insoluble) Hydrophilic head Group Hydrophobic tail group Hydrophobic tail Amphiphilic surfactant Micelle Surfactant + Inorganic precursor (Silica et al.) Burn off surfactant Add methanol PFAS + 0.01 N HCl TMOS PFASs 3-FPTMS Filtering & spin coating 13-FOTES Heat treatment 17-FDTMS Silica wall Fluorinated group - The hydrophobic interaction of hydrophobic chain of CTACl & hydrophobic perfluoroalkyl chain. CTACl used - The repulsion of hydrophobic perfluoroalkyl chain & hydrophilic PEO chain. F68 used CFn CFn CFn 350 oC 550 oC CFn CFn CFn CFn CFn <Hydrophobic> <Hydrophilic> 3-FPTMS and CTACl After calcination at 550 oC, the cylindrical pores are maintained. 350 oC 550 oC 17-FDTMS and CTAClAfter calcination at 550 oC, a less ordered and broken mesostructure was formed. H H H H H H H 17-FDTMS H H H H H H H 13-FOTES H H C* C C C 3-FPTMS H C Silica H : Hexagonal C : Cubic C* : Hexagonal/Cubic F68(Cubic) 50 43 40 35 30 20 10 5 1 [ CTACl ] / [ TMOS ] (x263) Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST) Fabrication and Evolution of Mesostructures in Fluorinated Organosilicate Mesoporous Thin Films Ji-In Jung, Jae Young Bae and Byeong-Soo Bae* Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea *E-mail: bsbae@kaist.ac.kr http://www.sol-gel.net/lomc Introduction Experiments • Surfactants for Experiment • Evaporation Induced Self-Assembly (Film) • Self-Assembly of Surfactants Alkyl-ammonium halide cationic surfactant [CH3(CH2)xN(CH3)3]Cl CTACl (x=15) Spherical micelle • Experimental Routes • Experimental Purposes • Formation of Mesoporous Materials Synthesis of fluorinated mesoporous organosilicate films with surfactants and chain lengths of PFASs TMOS Fluorinated mesoporous organosilicate films Mesoporous silica films PFASs with perfluoroalkyl groups 0.01N HCl • Inorganic-Organic Hybrid Mesoporous Materials Physical characteristics of fluorinated films depending on chain lengths of PFASs and kind of surfactants Add surfactant • Kind of Mesoporous Structures Stirring for 24 hr →Optical property (n) & hydrophobicity & formation scheme Thermal induced mesostructure and composition change →Investigation of microstructure, composition and optical property in the fluorinated organosilicate films Used in membrane, sensor, and optical and electroni devices. Fabrication of Films with CTACl • Confirmation of Perfluoroalkyl Groups • XRD Patterns of the Films • PFASs, the Role of Templates • PFASs Chain Length Effect As-synthesized After calcined FT-IR spectroscopy 1060 cm-1 Asymmetric stretching mode of Si-O-Si bond (b) 1146 cm-1 Bending mode of Si-CH2 of perfluoroalkylsilane (c) 1206 cm-1 Symmetric stretching mode of C-F bond of perfluoroalkyl chain Mesoporous fluorinated organosilicate thin films were calcined at 350 oC. PFASs with long perfluoroalkyl chain act as templates! Fabrication of Films with Pluronic F68 Formation Scheme • Comparison of Mesostructure Formation • XRD Patterns of the Films • Thermal Analysis of the Films TGA Curves As-synthesized After calcined FT-IR spectroscopy Pluronic F68 copolymer decomposes above 350 oC. Mesoporous fluorinated organosilicate thin films were calcined at 400 oC. Although surfactant concentration is very low, mesoporous films are mainly formed by long perfluoroalkyl chain (As template). Future Works Thermal-Induced Mesostructure Change • Refractive Index Change • XRD patterns • Mesostructure Changes • Compositional Change Photochromic Dye • - Applicable for optical waveguide, shutters, light modulators, and optical storage media • For optical shutter applications, a fast response time is required. • Study about the effect of hydrophobicity and pore size Fast response time & long switching cycle is expected. The increase calcination temperature cause the decomposition perfluoroalkyl groups. Possibilities for a variety of application in optics ! Conclusions References Multi-mesostructured Films It is possible to form the multi-layered films with thickness and different pore surface property such as pore size and pore structure. • PFASs with long perfluoroalkyl chains act as a structure directing agent. • Different interaction with templates cause the different mesostructure formation range. • The chain length of PFASs affected the formation of mesostructure and thermal-induced mesostructure change. • The increase of calcination temperature caused the change of the composition, mesostructure, and optical property in the mesoporous fluorinated organosilicate films. [Multi-layer with different pore size and pore structure]