Elucidation of molecular structures at buried polymer interfaces and biological interfaces using sum frequency generation vibrational spectroscopy

Zhang, Chi; Myers, John N.; Chen, Zhan

doi:10.1039/c3sm27710k

Cited by 87 publications

(100 citation statements)

References 210 publications

(458 reference statements)

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“…Vibrational sum-frequency generation (SFG) spectroscopy has been previously applied to study interfaces of polymers, 34 surfactant, 35 and proteins, 36 however, only a few studies exist that address polyelectrolyte/surfactant mixtures 37,38 and none of these show specific bands of each component in different spectral regions. By addressing both solvent and adsorbate specific bands, we gain detailed information on the molecular composition, charging state, and structure of the interfacial layer.…”

Section: Introductionmentioning

confidence: 99%

Structure of Polystyrenesulfonate/Surfactant Mixtures at Air–Water Interfaces and Their Role as Building Blocks for Macroscopic Foam

Schulze-Zachau

Braunschweig

2017

Langmuir

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Air/water interfaces were modified by oppositely charged poly(sodium 4-styrenesulfonate) (NaPSS) and hexadecyltrimethylammonium bromide (CTAB) polyelectrolyte/surfactant mixtures and were studied on a molecular level with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry. In order to deduce structure property relations, our results on the interfacial molecular structure and lateral interactions of PSS–/CTA+ complexes were compared to the stability and structure of macroscopic foam as well as to bulk properties. For that, the CTAB concentration was fixed to 0.1 mM, while the NaPSS concentration was varied. At NaPSS monomer concentrations <0.1 mM, PSS–/CTA+ complexes start to replace free CTA+ surfactants at the interface and thus reduce the interfacial electric field in the process. This causes the O−H bands from interfacial H2O molecules in our SFG spectra to decrease substantially, which reach a local minimum in intensity close to equimolar concentrations. Once electrostatic repulsion is fully screened at the interface, hydrophobic PSS–/CTA+ complexes dominate and tend to aggregate at the interface and in the bulk solution. As a consequence, adsorbate layers with the highest film thickness, surface pressure, and dilatational elasticity are formed. These surface layers provide much higher stabilities and foamabilities of polyhedral macroscopic foams. Mixtures around this concentration show precipitation after a few days, while their surfaces to air are in a local equilibrium state. Concentrations >0.1 mM result in a significant decrease in surface pressure and a complete loss in foamability. However, SFG and surface dilatational rheology provide strong evidence for the existence of PSS–/CTA+ complexes at the interface. At polyelectrolyte concentrations >10 mM, air–water interfaces are dominated by an excess of free PSS– polyelectrolytes and small amounts of PSS–/CTA+ complexes which, however, provide higher foam stabilities compared to CTAB free foams. The foam structure undergoes a transition from wet to polyhedral foams during the collapse.

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Section: Introductionmentioning

confidence: 99%

Structure of Polystyrenesulfonate/Surfactant Mixtures at Air–Water Interfaces and Their Role as Building Blocks for Macroscopic Foam

Schulze-Zachau

Braunschweig

2017

Langmuir

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“…[22][23][24][25][26][27][28][29][30][31] Recently, we developed a methodology which combines different analytical techniques including SFG, coherent anti-Stokes Raman spectroscopy (CARS), and Fourier transform infrared spectroscopy (FTIR) to probe the molecular structural changes on the surface, at the buried interface, and in the bulk for the same material. Here, a second-order nonlinear optical technique, sum frequency generation vibrational spectroscopy (SFG), was utilized to study citrate plasticized PVC.…”

Section: Introductionmentioning

confidence: 99%

The molecular interfacial structure and plasticizer migration behavior of “green” plasticized poly(vinyl chloride)

Zhang

Hankett

et al. 2015

Phys. Chem. Chem. Phys.

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Tributyl acetyl citrate (TBAC), a widely-used "green" plasticizer, has been extensively applied in products for daily use. In this paper, a variety of analytical tools including sum frequency generation vibrational spectroscopy (SFG), coherent anti-Stokes Raman spectroscopy (CARS), contact angle goniometry (CA), and Fourier transform infrared spectroscopy (FTIR) were applied together to investigate the molecular structures of TBAC plasticized poly(vinyl chloride) (PVC) and the migration behavior of TBAC from PVC-TBAC mixtures into water. We comprehensively examine the effects of oxygen and argon plasma treatments on the surface structures of PVC-TBAC thin films containing various bulk percentages of plasticizers and the leaching behavior of TBAC into water. It was found that TBAC is a relatively stable PVC plasticizer compared to traditional non-covalent plasticizers but is also surface active. Oxygen plasma treatment increased the hydrophilicity of TBAC-PVC surfaces, but did not enhance TBAC leaching. However, argon plasma treatment greatly enhanced the leaching of TBAC molecules from PVC plastics to water. Based on our observations, we believe that oxygen plasma treatment could be applied to TBAC plasticized PVC products to enhance surface hydrophilicity for improving the biocompatibility and antibacterial properties of PVC products. The structural information obtained in this study will ultimately facilitate a molecular level understanding of plasticized polymers, aiding in the design of PVC materials with improved properties.

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“…This type of buried interface is usually difficult to probe using other analytical methods [2]. Polarized SFG spectra can be used to derive molecular orientation information of various functional groups such as methyl, methylene, and phenyl groups, as well as protein secondary structures at various interfaces [4][5][6][7] SFG can also be used to study time-dependent interfacial behaviors of various molecules [8]. These advantages make SFG spectroscopy unique in material science and biological studies [6].…”

mentioning

confidence: 99%

“…The entire system resided on a movable breadboard and could be transitioned conveniently for fast installation. All of the SFG spectra in this study were collected using a polarization combination of s-polarized signal, s-polarized visible, and p-polarized IR, although other polarization combinations also can be used [6]. The system still has the capability of deriving molecular orientations based on polarized SFG spectra.…”

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confidence: 99%

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Sum frequency generation vibrational spectroscopic studies on buried heterogeneous biointerfaces

et al. 2014

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A sum frequency generation (SFG) vibrational micro-spectroscopy system was developed to examine buried heterogeneous biointerfaces. A compact optical microscope was constructed with total-internal reflection (TIR) SFG geometry to monitor the tightly focused SFG laser spots on interfaces, providing the capability of selectively probing different regions on heterogeneous biointerfaces. The TIR configuration ensures and enhances the SFG signal generated only from the sample/substrate interfacial area. As an example for possible applications in biointerfaces studies, the system was used to probe and compare buried interfacial structures of different biological samples attached to underwater surfaces. We studied the interface of a single mouse oocyte on a silica prism to demonstrate the feasibility of tracing and studying a single live cell and substrate interface using SFG. We also examined the interface between a marine mussel adhesive plaque and a CaF2 substrate, showing the removal of interface-bonded water molecules. This work also paves the way for future integration of other microscopic techniques such as TIR-fluorescence microscopy or nonlinear optical imaging with SFG spectroscopy for multimodal surface or interface studies.

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Elucidation of molecular structures at buried polymer interfaces and biological interfaces using sum frequency generation vibrational spectroscopy

Cited by 87 publications

References 210 publications

Structure of Polystyrenesulfonate/Surfactant Mixtures at Air–Water Interfaces and Their Role as Building Blocks for Macroscopic Foam

Structure of Polystyrenesulfonate/Surfactant Mixtures at Air–Water Interfaces and Their Role as Building Blocks for Macroscopic Foam

The molecular interfacial structure and plasticizer migration behavior of “green” plasticized poly(vinyl chloride)

Sum frequency generation vibrational spectroscopic studies on buried heterogeneous biointerfaces

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