Detection of Tethered Biocide Moiety Segregation to Silicone Surface Using Sum Frequency Generation Vibrational Spectroscopy

Abstract

Polymer surface properties are controlled by the molecular surface structures. Sum frequency generation (SFG) vibrational spectroscopy has been demonstrated to be a powerful technique to study polymer surface structures at the molecular level in different chemical environments. In this research, SFG has been used to study the surface segregation of biocide moieties derived from triclosan (TCS) and tetradecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (C-14 QAS) that have been covalently bound to a poly(dimethylsiloxane) (PDMS) matrix. PDMS materials are being developed as coatings to control biofouling. This SFG study indicated that TCS-moieties segregate to the surface when the bulk concentration of TCS-moieties exceeds 8.75% by weight. Surface segregation of C-14 QAS moieties was detected after 5% by weight incorporation into a PDMS matrix. SFG results were found to correlate well with antifouling activity, providing a molecular interpretation of such results. This research showed that SFG can aid in the development of coatings for controlling biofouling by elucidating the chemical structure of the coating surface.

Understanding molecular structures of silanes at buried polymer interfaces using sum frequency generation vibrational spectroscopy and relating interfacial structures to polymer adhesion

“…SFG allows one to detect the presence, coverage, chemical environment, orientation and orientational ordering of surface or interfacial species, making it an ideal method to study the molecular-level mechanisms that contribute to adhesive bonding. SFG has been extensively used to characterize polymer surfaces and interfaces such as polymer surface structures in air, polymer surface restructuring in water, surface structures of polymer blends and copolymers, solid-polymer interfaces, and polymerbiomolecule interfaces [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. More specifically, it has been used to study polymer-silane interactions including the elucidation of conformations of silanes at polymer interfaces [25,26], the detection of hydrogen bonding between polymer surface groups and silanes [27], and the monitoring of interfacial diffusion of silane molecules into polymer films [28,29].…”

Molecular level studies of polymer behaviors at the water interface using sum frequency generation vibrational spectroscopy

“…80,81 SFG has been used to characterize the surfaces of PDMS materials with various quaternary ammonium salts (QAS) incorporated into the polymer. 20,21 In addition, the effects of bulk biocide concentration and the tethered QAS chain length on the surface structure of PDMS incorporated with QAS were investigated. Such surface structures can be well correlated to the antifouling activity tested using bacteria.…”

“…To improve such antibiofouling systems, molecular level research on polymer functional group orientation changes in aqueous environment has been performed as well. [19][20][21] In addition to biofouling, a particular section of recent biopolymer research focuses on polyelectrolytic systems, where the interactions between water, charged polymers, and surfactants have been studied. The folding mechanisms of polymers between water and oil interfaces are extremely important in a number of biological systems.…”

Investigation of sub-monolayer, monolayer, and multilayer self-assembled semifluorinated alkylsilane films

“…Our SFG system and the underlying SFG theory have been described in detail in previous publications [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. The experiments described herein utilize a face-up sample geometry, where the frequency-fixed visible beam overlaps with the frequency-tunable infrared beam on the SA film formed on the top face of a fused silica window.…”