Direct Measurement of Acid−Base Interaction Energy at Solid Interfaces

Kurian, Anish; Prasad, Shishir; Dhinojwala, Ali

doi:10.1021/la103591f

Cited by 44 publications

(107 citation statements)

References 18 publications

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“…The amount of red-shift is related to the interaction strength according to the Badger–Bauer equation; the higher the shift, the stronger the interaction strength. The calculated interaction strength between pristine aggregate glue and sapphire O-H groups (Supplementary Table 1 ) is comparable to the strongest interaction between carbonyl groups and sapphire surface O–H groups reported in literature 29 , 42 . We also observe C–H stretching vibrations in the 2800–3050 cm −1 region.…”

Section: Resultssupporting

confidence: 83%

“…When sapphire O–H groups are in contact with air (air/sapphire interface), a sharp peak at ~3720 cm −1 is observed for the sapphire hydroxyl groups. However, when sapphire O–H groups come in contact with other molecules such as poly(methyl methacrylate) or polystyrene, the O–H peak becomes broader and shifts to lower wavenumbers due to acid–base interactions between the sapphire O–H groups and the other molecules in contact 29 , 42 . The amount of red-shift is related to the interaction strength according to the Badger–Bauer equation; the higher the shift, the stronger the interaction strength.…”

Section: Resultsmentioning

confidence: 99%

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Hygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions

et al. 2018

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Adhesion in humid environments is fundamentally challenging because of the presence of interfacial bound water. Spiders often hunt in wet habitats and overcome this challenge using sticky aggregate glue droplets whose adhesion is resistant to interfacial failure under humid conditions. The mechanism by which spider aggregate glue avoids interfacial failure in humid environments is still unknown. Here, we investigate the mechanism of aggregate glue adhesion by using interface-sensitive spectroscopy in conjunction with infrared spectroscopy. We demonstrate that glycoproteins act as primary binding agents at the interface. As humidity increases, we observe reversible changes in the interfacial secondary structure of glycoproteins. Surprisingly, we do not observe liquid-like water at the interface, even though liquid-like water increases inside the bulk with increasing humidity. We hypothesize that the hygroscopic compounds in aggregate glue sequester interfacial water. Using hygroscopic compounds to sequester interfacial water provides a novel design principle for developing water-resistant synthetic adhesives.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Hygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions

et al. 2018

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“…Interestingly, in SSP polarization, the 3645 cm −1 peak not only decreased in intensity but also shifted to lower wavenumber. It is possible that the weaker acid−base interactions were The correlation between the shift of OH peak and the strength of interactions can be quantified using the Badger− Bauer equation −ΔH = mΔν + C. 30,47 If we assume that the hydrogen-bonding and van der Waals interactions between hexadecanol molecules in the self-assembled monolayer were the same as those in the solid bulk, the increased monolayer melting temperature should be a result of the acid−base interactions between alcohol molecules and sapphire surface OH groups. To calculate the strength of the acid−base interactions, which were disrupted during the monolayer melting transition, we have subtracted the portion of the acid−base interactions that existed at 120°C from those at 65°C…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

“…Since SFG can also monitor the position and shift of the surface hydroxyl peak, this technique can also be used to directly determine the strength of the hydrogen-bonding interaction and its influence on stabilizing the ordered monolayer above the bulk T m . 30,31 In addition to the structure of hexadecanol SAM in contact with its own melt, it is also intriguing to understand how the SAM influences the crystal structure upon freezing (referred to as s−s interface). It has been shown that long chain alcohols exhibit three polymorphic phases: the α rotator phase, β crystalline phase, and γ crystalline phase ( Figure 1).…”

Section: ■ Introductionmentioning

confidence: 99%

Thermal Behavior of Long-Chain Alcohols on Sapphire Substrate

Zhu

Dhinojwala

2015

Langmuir

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Structures of amphiphilic molecules at the liquid/solid and solid/solid interfaces are important in understanding lubrication, colloid stabilization, chromatography, and nucleation. Here, we have used interface-sensitive sum frequency generation (SFG) spectroscopy to characterize the interfacial structures of long-chain alcohols above and below the bulk melting temperature (Tm). The melting temperature of the ordered hexadecanol monolayer was measured to be around 30 °C above the bulk Tm, consistent with the transition temperature reported using X-ray reflectivity [ Phys. Rev. Lett. 2011 , 106 , 137801 ]. The disruption of hydrogen bonds between the sapphire and the alcohol hydroxyl groups was directly measured as a function of temperature. The strength of this hydrogen-bonding interaction, which explained the monolayer thermal stability above Tm, was calculated using the Badger-Bauer equation. Below Tm, the ordered self-assembled monolayer influenced the structure of the interfacial crystalline layer, and the transition from the ordered monolayer to the bulk crystalline phases (α rotator phase, β crystalline phase, and γ crystalline phase) resulted in packing frustrations at the interface.

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“…In addition, the shift in the surface sapphire O–H peak can be used to calculate the strength of the acid–base interactions (hydrogen bonding is a subset of acid–base interactions). 57 For example, in the previously reported study, the ester groups in poly(methyl methacrylate) showed stronger interaction (O–H peak is shifted to 3580 cm –1 compared to free O–H peak at 3720 cm –1 ) than functional groups in polystyrene (3645 cm –1 ) when in contact with a sapphire substrate. 58 Similarly, since the interfacial adhesion of the deprotected elastomer is higher, we speculated that there might be a larger shift for the deprotected elastomer as compared to protected elastomer, which would indicate a stronger bond between the hydroxyl groups of catechol and the sapphire.…”

Section: Results and Discussionmentioning

confidence: 81%

Direct Observation of the Interplay of Catechol Binding and Polymer Hydrophobicity in a Mussel-Inspired Elastomeric Adhesive

et al. 2018

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Marine organisms such as mussels have mastered the challenges in underwater adhesion by incorporating post-translationally modified amino acids like l-3,4-dihydroxyphenylalanine (DOPA) in adhesive proteins. Here we designed a catechol containing elastomer adhesive to identify the role of catechol in interfacial adhesion in both dry and wet conditions. To decouple the adhesive contribution of catechol to the overall adhesion, the elastomer was designed to be cross-linked through [2 + 2] photo-cycloaddition of coumarin. The elastomer with catechol moieties displayed a higher adhesion strength than the catechol-protected elastomer. The contact interface was probed using interface-sensitive sum frequency generation spectroscopy to explore the question of whether catechol can displace water and bond with hydrophilic surfaces. The spectroscopy measurements reveal that the maximum binding energy of the catechol and protected-catechol elastomers to sapphire substrate is 7.0 ± 0.1 kJ/(mole of surface O–H), which is equivalent to 0.10 J/m2. The higher dry and wet adhesion observed in the macroscopic adhesion measurements for the catechol containing elastomer originates from multiple hydrogen bonds of the catechol dihydroxy groups to the surface. In addition, our results show that catechol by itself does not remove the confined interstitial water. In these elastomers, it is the hydrophobic groups that help in partially removing interstitial water. The observation of the synergy between catechol binding and hydrophobicity in enabling the mussel-inspired soft adhesive elastomer to stick underwater provides a framework for designing materials for applications in tissue adhesion and moist-skin wearable electronics.

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Direct Measurement of Acid−Base Interaction Energy at Solid Interfaces

Cited by 44 publications

References 18 publications

Hygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions

Hygroscopic compounds in spider aggregate glue remove interfacial water to maintain adhesion in humid conditions

Thermal Behavior of Long-Chain Alcohols on Sapphire Substrate

Direct Observation of the Interplay of Catechol Binding and Polymer Hydrophobicity in a Mussel-Inspired Elastomeric Adhesive

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