Surface Structures of PDMS Incorporated with Quaternary Ammonium Salts Designed for Antibiofouling and Fouling Release Applications

Abstract

Poly(dimethylsiloxane) (PDMS) materials have been extensively shown to function as excellent fouling-release (FR) coatings in the marine environment. The incorporation of biocide moieties, such as quaternary ammonium salts (QAS), can impart additional antibiofouling properties to PDMS-based FR coating systems. In this study, the molecular surface structures of two different types of QAS-incorporated PDMS systems were investigated in different chemical environments using sum frequency generation vibrational spectroscopy (SFG). Specifically, a series of PDMS coatings containing either a QAS with a single ammonium salt group per molecule or a quaternary ammonium-functionalized polyhedral oligomeric silsesquioxane (Q-POSS) were measured with SFG in air, water, and artificial seawater (ASW) to investigate the relationships between the interfacial surface structures of these materials and their antifouling properties. Although previous studies have shown that the above-mentioned materials are promising contact-active antifouling coatings, slight variations of the QAS structure can lead to substantial differences in the antifouling performance. Indeed, the SFG results presented here indicated that the surface structures of these materials depend on several factors, such as the extent of quaternization, the molecular weight of the PDMS component, and the functional groups of the QAS used for incorporation into the PDMS matrix. It was concluded that in aqueous environments a lower extent of Q-POSS quaternization and the use of ethoxy (instead of methoxy) functional groups for QAS incorporation facilitated the extension of the alkyl chains away from the nitrogen atom of the QAS on the surface. The SFG results correlated well with the antifouling activity studies that indicated that the coatings exhibiting a lower concentration of longer alkyl chains protruding out of the surface can neutralize microorganisms more effectively, ultimately leading to better antifouling performance. Furthermore, the results of this study provide additional evidence that incorporated QAS exert their antimicrobial activity through a two-step interaction. The first step is the adsorption of the bacteria on the surface as a result of the electrostatic attraction between the negatively charged microorganisms and the positively charged QAS nitrogen atoms on the surface. The second step is the disruption of the cell membranes by the penetration of the QAS long, extended alkyl chains.

Architecture, Assembly, and Emerging Applications of Branched Functional Polyelectrolytes and Poly(ionic liquid)s

“…147,148,149,150,151,152,153,154,155,156,157,158,159,160 Based on the range of molecular masses involved, these compounds can be regarded as OIL compounds. Their molecular weight depends on the length of the spacer and the type of the ionic group and starts from 1338 g/mol for derivatives with one arm 147 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 temperature of 172°C.…”

“…Such biocide coatings are promising as antibiofouling and fouling release applications in demanding marine environments. 158 Coatings and biocide films can be also prepared by sol-gel condensation of 3-(N,N-dimethylalkyl)…”

“…41 To this end, oligo(ionic liquid)s (OILs) with molecular weights below 10 kg/mol have traits of both ionic liquids and poly(ionic liquid)s. Unlike poly(ionic liquid)s, many oligo(ionic liquid)s are still able to preserve a liquid aggregate state in a broad range of temperatures, are often water-soluble, and have a strong dependence of properties on the number and type of ionic end groups and constitutional units. Furthermore, oligo(ionic liquid)s can be polymerized into poly(ionic liquid)s. 42 and antifouling agents, 158 and many other uses. 34,46,47,141,142,157 In this review, we will discuss the synthesis, structural characteristics, and properties of both branched oligo(ionic liquid)s and poly(ionic liquid)s with dendritic and star-like molecular architectures important for prospective and emerging applications.…”

“…Among them, the most explored are aprotic cationic POSS-IL, whereas the literature on protic POSS-IL of this structure is absent to the best of our knowledge. The IL-groups are represented by terminal aliphatic tertiary amines with various lengths of the aliphatic substituent at the nitrogen atom,147,148,149,151,156,158 and also 1-substituted imidazole groups 150,153,154,155,159,161,162. The classical anionic groups are usually used as counterions (Figure 2).The charge density is regulated either by synthesis of monosubstituted POSS with varied spacer lengths, or by the degree of quaternization of these amino-containing substituents in the case of octasubstituted POSS 147,149,153,154,155.…”

“…and as ionic self-assembly platforms, IL fillers, antimicrobial additives,204,205 solvents for polysaccharides and other poorly soluble materials, surface modifiers, and carriers for heterogeneous catalysis. In addition, it was reported that the dendritic PAMAM derivatives with a POSS core and imidazolium end-functionalities are candidates for the construction of ordered networks for solid ionic conductive materials 159.…”