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Raja Beryl J, Xavier JR. Influence of silane functionalized nanoclay on the barrier, mechanical and hydrophobic properties by clay nanocomposite films in an aggressive chloride medium. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127625] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Sims RA, Noguchi H, Harmer SL, Quinton JS, Uosaki K. Probing Molecular Mechanisms during the Oscillatory Adsorption of Propyl Chain Functionalized Organosilane Films with Sum Frequency Generation Spectroscopy. J Phys Chem B 2021; 125:4383-4392. [PMID: 33590760 DOI: 10.1021/acs.jpcb.0c09715] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The selectivity rules of sum frequency generation spectroscopy were exploited to determine propyl chain order during the time-dependent oscillatory adsorption of propyltrimethoxysilane (PTMS) and Langmuir-type growth of propyldimethylmethoxysilane (PDMMS). During the early stages of film growth, molecular packing density determines the extent of propyl chain defects within both films with high surface coverage resulting in a film with fewer defects. Following this, an ordered monolayer-like film stabilizes on the Al2O3 substrate for both silanes. Although this result is intuitive for the Langmuir-type growth of PDMMS, the stabilization of molecular ordering despite the continuing oscillation in PTMS surface coverage indicates the presence of a stable monolayer, while it is the oligomerized PTMS dendrimers which continue to desorb and readsorb to the substrate. We also reveal for the first time, the formation of a physisorbed bilayer during the self-assembly process of PTMS. The presence of this ordered, physisorbed bilayer on top of the covalently bound PTMS film plays a key role in the process of the molecular self-assembly mechanism and is proposed to enable further condensation of the covalently bound film.
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Affiliation(s)
- Ruby A Sims
- Flinders Institute for Nanoscale Science and Technology (FINST), College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.,Flinders Microscopy and Microanalysis (FMMA), College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.,Global Research Centre for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Japan
| | - Hidenori Noguchi
- Global Research Centre for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Japan
| | - Sarah L Harmer
- Flinders Institute for Nanoscale Science and Technology (FINST), College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.,Flinders Microscopy and Microanalysis (FMMA), College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
| | - Jamie S Quinton
- Flinders Institute for Nanoscale Science and Technology (FINST), College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.,Flinders Microscopy and Microanalysis (FMMA), College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
| | - Kohei Uosaki
- Global Research Centre for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Japan
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The Role of Physisorption and Chemisorption in the Oscillatory Adsorption of Organosilanes on Aluminium Oxide. Polymers (Basel) 2019; 11:polym11030410. [PMID: 30960394 PMCID: PMC6473760 DOI: 10.3390/polym11030410] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/20/2019] [Accepted: 02/22/2019] [Indexed: 11/29/2022] Open
Abstract
The effect of physisorbed and chemisorbed species on the time-dependent self-assembly mechanism of organosilane films has been investigated on aluminium oxide using X-ray Photoelectron Spectroscopy. The role of physisorbed species was determined through their removal using a simple rinsing procedure while monitoring film substrate coverage. Removing physisorbed species from Propyldimethylmethoxysilane films, shown to follow a Langmuir-type adsorption profile, reduces the substrate coverage initially but quickly results in coverages equivalent to films that did not undergo a rinsing procedure. This indicates that all Propyldimethylmethoxysilane molecules are covalently bound to the substrate following 15 s of film growth. Removing physisorbed species from films, which have been shown to follow an oscillatory adsorption profile, Propyltrimethoxysilane and Propylmethyldimethoxysilane, reveal the persistence of these oscillations despite a reduction in silane substrate coverage. These results not only confirm the presence of two thermodynamically favourable phases in the condensation equilibrium reaction as physisorbed and chemisorbed species, but also indicate that the desorption of species during film growth involves both states of chemical binding.
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