Session: PMSE/POLY Poster Session:

The direct relationship between adhesion strength and the structure of amino acid groups is still debated. Herein, we sought to study the molecular and macroscopic effects of incorporating amino acid groups on the interfacial adhesion of synthetic mussel-inspired adhesives. Specifically, we attempted to decouple the contribution of aromatic and hydroxyl groups on the interfacial adhesion of mussel-inspired elastomers (MIEs) using synthetic chemistry, sum-frequency generation (SFG) spectroscopy, and molecular dynamics (MD) simulation. We created four different MIEs with similar moduli and varying aromatic and hydroxyl groups (MIE-mPhe = 1 aromatic, 0 hydroxyl; MIE-mSer = 0 aromatic, 1 hydroxyl; MIE-mTyr = 1 aromatic, 1 hydroxyl; MIE-mDOPA = 1 aromatic, 2 hydroxyls). The interfacial adhesion strength (W_ad) of the MIEs determined by JKR model adhesion measurements showed the following trend W_ad: MIE-mPhe ~ MIE-mSer < MIE-mTyr < MIE-mDOPA. Notably, the trend of W_ad overlapped with the overall interaction enthalpy per molecule (H_molecule) semi-empirically determined from the combination of SFG spectroscopy and MD simulation. The aromatic groups form multivalent weak acid-base interactions and hydroxyl groups form strong acid-base interactions. Interestingly, the number and the strength of both weak and strong acid-base interactions integrally influenced the W_ad.

Dr. Amal Narayanan

Princeton University

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