Probing polymer surfaces and interfaces using sum frequency generation vibrational spectroscopy - a powerful nonlinear optical technique

Lü, Xiaolin; Chen, Zhan; Xue, Gi; Wang, Xinping

doi:10.1007/s11458-010-0220-7

Cited by 5 publications

(4 citation statements)

References 73 publications

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“…Sum frequency generation (SFG) vibrational spectra were obtained by a custom-designed EKSPLA SFG spectrometer, which has been described in detail by various researchers. − Briefly, the visible input beam at 0.532 μm was generated by frequency doubling a part of the fundamental output from an EKSPLA Nd:YAG laser. The IR beam, tunable between 1000 and 4300 cm –1 (with a line width < 6 cm –1 ) was obtained from an optical parametric generation/amplification/difference frequency generation (OPG/OPA/DFG) system based on LBO and AgGaS 2 crystals, which were pumped by the second harmonic and the fundamental output of the laser.…”

Section: Methodsmentioning

confidence: 99%

Surface Structure of Spin-Coated Fluorinated Polymers Films Dominated by Corresponding Film-Formation Solution/Air Interface Structure

et al. 2012

J. Phys. Chem. C

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In this paper, the relationship between the surface structures of spin-coated fluorinated polymer films and their corresponding film-formation solution/air interface structures was investigated. Film-forming poly(n-alkyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate (FMA; PFMA y -ec-PnAMA x -ec-PFMA y ) was synthesized via a controlled/living atom-transfer radical polymerization (ATRP) technique. The structures both at solution interface and on the spin-coated film surface for these polymers were studied by X-ray photoelectron spectroscopy (XPS), sum frequency spectroscopy (SFG), and surface tension measurements. The results showed that, with increasing polymerization degree of PnAMA, the fluorinated moieties in PFMA y -ec-PnAMA x -ec-PFMA y adsorbed at the solution/air interface were gradually completely replaced by PnAMA segments, resulting in an increase in corresponding solution surface tension until it was equal to that of poly(n-alkyl methacrylate) solution. Additionally, it was observed for the first time that the surface F/C ratios of spin-coated films decreased linearly with increasing surface tension of the corresponding film-formation polymer solution. Overall, the results indicate that the ultimate surface composition of spin-coated films of these fluorinated methacrylates was mainly dominated by their corresponding film-formation solution/air interfacial structure. This work provides a fundamental understanding of the formation of film surface structures from fluorinated polymer solution to the resulting solid film.

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Section: Methodsmentioning

confidence: 99%

Surface Structure of Spin-Coated Fluorinated Polymers Films Dominated by Corresponding Film-Formation Solution/Air Interface Structure

et al. 2012

J. Phys. Chem. C

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“…Sum frequency generation (SFG) vibrational spectroscopy has been developed into a powerful probe to study the surface and interfacial structures at the molecular level. − For example, it successfully elucidated molecular structures of various polymer surfaces and interfaces. ,− This technique intrinsically detects the second-order nonlinear susceptibility at polymer surfaces and interfaces in that the second-order nonlinear susceptibility of the polymer bulk vanishes under the electric dipole approximation. The generally used sample geometry in the SFG study was a polymer thin film on a substrate. ,− In this case, the polymer thin film was taken as a nonlinear polarization sheet which can generate the SFG signals, as shown in Figure .…”

Section: Introductionmentioning

confidence: 99%

A Sum Frequency Generation Vibrational Study of the Interference Effect in Poly(n-butyl methacrylate) Thin Films Sandwiched between Silica and Water

Lü

Clarke

et al. 2011

J. Phys. Chem. C

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On the basis of the development in the literature, a thin film model was used to interpret the thickness-dependent sum frequency generation (SFG) spectra collected from the air/silica/poly(n-butyl methacrylate) (PBMA)/water system. By taking into account the Fresnel coefficients of the PBMA layers at the silica/PBMA and PBMA/water interfaces, the SFG spectra of the silica/PBMA and PBMA/water interfaces were obtained. The side chain methyl vibrational modes at the two interfaces were found to have opposite phases. This suggests that the side chain methyl groups at the two interfaces adopt different absolute orientations. It is believed that methyl groups at both interfaces point toward the PBMA bulk considering the unfavorable interactions between the hydrophobic methyl groups and hydrophilic silica surface and water. Orientation analysis indicates the side chain methyl groups at both interfaces tilt more toward the interfaces rather than be perpendicular to them. Applying the thin film model to the air/PBMA/ silica system, we found that the surface signals from PBMA in air dominate the SFG output on account of the relatively higher Fresnel coefficients at this surface over those of the buried PBMA/silica interface.

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“…Nonetheless, the above requirements can be achieved by a second-order nonlinear optical technique–sum frequency generation (SFG) vibrational spectroscopy, which has been developed for 30 years. This coherent optical technique has the intrinsic monolayer/submonolayer sensitivity and surface/interface selectivity to probe the detailed molecular-level structural information at surfaces or interfaces, − thus offering a powerful analytical way to study different materials, including polymers. Previous work has demonstrated that the surface restructuring of polymeric materials can be investigated upon contact with water, organic solvents, or treatment with surface plasma by using the SFG vibrational spectroscopy. ,,,,− However, a systematic molecular-level study using SFG on an antifouling polymer surface in air, surface in contact with water/protein solution, and buried polymer/substrate interface upon water exposure has not been fully conducted yet, and there still remain important scientific issues to be studied.…”

Section: Introductionmentioning

confidence: 99%

Detecting Surface Hydration of Poly(2-hydroxyethyl methacrylate) in Solution in situ

Liu

Zhang

et al. 2016

Macromolecules

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Understanding the interfacial molecular structures of antifouling polymers in solutions is extremely important in research and applications related to chemistry, biology, and medicine. However, it is generally challenging to probe such buried solid/liquid interfaces in situ. We herein report a molecular-level study on detecting the interfacial molecular structures of an antifouling hydrogel material, poly(2-hydroxyethyl methacrylate) (PHEMA), in contact with water and bovine serum albumin (BSA) solution in situ using sum frequency generation (SFG) vibrational spectroscopy. To compare to and validate our in situ experiments, molecular-level structures of the substrate/PHEMA interface before and after water exposure were also detected. The detected strong O–H vibrational signals from water and hydroxyethyl and carbonyl vibrational signals from PHEMA prove that the PHEMA surface hydration was attributed to the interaction between water and PHEMA side hydrophilic groups. SFG experimental results verify that the adsorbed BSA molecules at the PHEMA/solution interface were disorderly arranged, supported by data from the laser scanning confocal microscopic (LSCM) experiment. This indicates the weak interaction between the BSA molecules and PHEMA surface. This direct detection of the surface hydrated structures of PHEMA sheds light on understanding the interfacial properties of antifouling materials in aqueous environments. The capability reported here to probe the PHEMA/solution interface and the hidden substrate/PHEMA interface after water exposure can be applied to investigate a broad range of interfaces of antifouling materials.

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Probing polymer surfaces and interfaces using sum frequency generation vibrational spectroscopy - a powerful nonlinear optical technique

Cited by 5 publications

References 73 publications

Surface Structure of Spin-Coated Fluorinated Polymers Films Dominated by Corresponding Film-Formation Solution/Air Interface Structure

Surface Structure of Spin-Coated Fluorinated Polymers Films Dominated by Corresponding Film-Formation Solution/Air Interface Structure

A Sum Frequency Generation Vibrational Study of the Interference Effect in Poly(n-butyl methacrylate) Thin Films Sandwiched between Silica and Water

Detecting Surface Hydration of Poly(2-hydroxyethyl methacrylate) in Solution in situ

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