Modeling of Structure-Property Relationships of Polymerizable Surfactants with Antimicrobial Activity

Giorgio De Luca,Bartolo Gabriele,Alberto Figoli,Roberta Amuso,Raffaella Mancuso,Lucio Lucadamo

doi:10.3390/app8101972

Giorgio De Luca, Bartolo Gabriele + Show 4 more

Open Access

https://doi.org/10.3390/app8101972

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Abstract

Polymerizable quaternary ammonium salts (PQASs) were synthesized in a previous work and some of them were used as surfactants in the antimicrobial coating of commercial membranes. Herein, the electrostatic charges, maximum length, and aspect ratio of these antibacterial surfactants were calculated with the aim of investigating the relationship between the properties, recognized to control the biocidal activity of these molecules, and the molecular structures. The effect of the water molecules was considered through a quantum and molecular mechanics approach. The correlation between the number of carbons in the main aliphatic chain of PQAS and the above properties was investigated, by finding that the net charge on the ammonium group does not increase as the number of carbons in the aliphatic chain increase. Thus, although this number influences the antibacterial activity of the surfactants, this influence is not correlated with an increase of the ammonium positive charge. Unlike the partial charges, a different trend was obtained for the surfactants’ maximum length and aspect ratio in agreement with the experimental behavior. As this modeling does not use empirical or adjustable parameters, it can assist the synthetic plan of new structures for surface functionalization, in order to improve the biofouling resistance of the membranes.

Highlights

Biofouling can be considered a great drawback limiting the use of membranes in the treatment of domestic or agricultural wastewater
Membranes with increased resistance to biofouling are required; the knowledge of the relationships between the structure and properties, correlated with the antibacterial activity of the molecules, is crucial for the synthesis of novel membrane functionalization. Because of their well-known antimicrobial activity, since the first half of the 20th century, quaternary ammonium salts (QAS) have been used in many human activities [1,2]. They are amphiphilic chemicals with a positive charge related to the quaternary ammonium group and have a hydrophobic tail formed by alkyl chains, they are considered surfactants
Ye et al [10] measured the antimicrobial activity of six QAS tethered polydimethylsiloxanes salts as a function of aliphatic chains length, in order to explain the effect of the chain length on the antiseptic property of QAS-linked polymers

Summary

Introduction

Biofouling can be considered a great drawback limiting the use of membranes in the treatment of domestic or agricultural wastewater. Biofouling causes numerous problems, ranging from the flow declining, with a consequent loss of membrane performance, to the cleaning of the membranes, with consequences on the costs of the wastewater treatment For these reasons, membranes with increased resistance to biofouling are required; the knowledge of the relationships between the structure and properties, correlated with the antibacterial activity of the molecules, is crucial for the synthesis of novel membrane functionalization. Membranes with increased resistance to biofouling are required; the knowledge of the relationships between the structure and properties, correlated with the antibacterial activity of the molecules, is crucial for the synthesis of novel membrane functionalization Because of their well-known antimicrobial activity, since the first half of the 20th century, quaternary ammonium salts (QAS) have been used in many human activities (industrial, agricultural, household, and hospital) [1,2]. The charge density on the antiseptic surfaces [12,13] correlated to the concentration of the quaternary nitrogen and partial charge, as well as the length of the alkyl substituents [14,15,16,17], affect the antibacterial activity of QAS-linked polymers

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