title: Synthesis and comparison of two poly (methyl methacrylate-b-3-(trimethoxysilyl)propyl methacrylate)/SiO2 hybrids by "grafting-to" approach.
abstract: Two copolymer/SiO2 hybrids are prepared by growing SiO2 on the template of well -structured diblock copolymer PMMA-b-PMPS using a "grafting-to" approach. PMMA-b-PMPS is obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate (PMMA) and 3-(trimethoxysilyl)propyl methacrylate (PMPS) using a brominated initiator end group termed 1H,1H,2H,2H-heptadecafluoro (F-Br) and a conventional initiator of ethyl 2-bromoisobutyrate (EBiB), respectively. The "grafting-to" approach is controlled at HCl for 24h by hydrolysis and condensation of Si(OCH3)3 groups in PMPS with tetraethyl orthosilicate (TEOS) to gain both hybrids of F-PMMA-b-PMPS/SiO2 (by F-Br initiator) and E-PMMA-b-PMPS/SiO2 (by EBIB initiator). Comparatively, a little amount of fluorine content provided by F-Br is able to tighten the size of self-assembled micelles, to improve wettability and the viscoelasticity of F-PMMA-b-PMPS film due to F-Br migrating onto the film surface. Therefore, the surface of F-PMMA-b-PMPS film is sufficiently hydrophobic (99° and Δf=2941Hz) than E-PMMA-b-PMPS film (94°and Δf=4820Hz), and the viscoelasticity of the adsorbed layer for F-PMMA-b-PMPS (ΔD/Δf=-0.112) film is much harder than E-PMMA-b-PMPS/SiO2 (ΔD/Δf=-0.071). On the other hand, the cross-linked silica in PMMA-b-PMPS/SiO2 could also increase water contact angels of films (100-107°) and decrease the water absorption (Δf=704-798Hz). The influence on the viscoelasticity of the adsorbed layer by the fluorine group is much more obvious than the cross-linked silica, therefore F-PMMA-b-PMPS/SiO2 (ΔD/Δf=-0.347) and F-PMMA-b-PMPS (ΔD/Δf=-0.112) films have harder adsorbed layer than E-PMMA-b-PMPS/SiO2 (-0.071) and F-PMMA-b-PMPS films (-0.042). However, compared with a slightly improvement in thermo stability by F-Br, the cross-linked silica in PMMA-b-PMPS/SiO2 performs significantly improving thermal decomposition temperature at 300°C and 350°C.
authors.affiliation: Department of Chemistry, School of Science, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Hongpu
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Chemistry, School of Science, Xi'an Jiaotong University, Xi'an 710049, China. Electronic address: heling@mail.xjtu.edu.cn.
authors.forename: Ling
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Chemistry, School of Science, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Kehan
authors.initials: K
authors.lastname: Huang
authors.affiliation: Department of Chemistry, School of Science, Xi'an Jiaotong University, Xi'an 710049, China.
authors.forename: Min
authors.initials: M
authors.lastname: Gao
keywords: Diblock copolymer; Hybrid; Self-assembly; Surface properties; Thermo stability; Viscoelasticity