A Sustained Release Anchored Biocide System Utilizing the Honeycomb Cellular Structure of Expanded Perlite

The development of a sustained-release biocide system, involving an anchored quaternary ammonium salt (AQAS) embedded in expanded perlite (EP) substrate, is reported. Scanning electron microscopy (SEM) images reveal the well-defined honeycomb cells that are a feature of EP. These honeycomb cells exhibit a variety of polygon shapes, which are filled with the AQAS molecules as evidenced by SEM data. The aqueous leaching of the AQAS from the EP honeycomb cells is monitored by the Fourier transform infrared CH stretching absorbance maxima at 2920 and 2850 cm^-1. Solid-state NMR data indicate the formation of three dominant oligomeric forms of the AQAS biocide molecules formed within the EP network by condensation reactions at curing temperatures (160 °C). The various oligomeric species involve different numbers of SiO chains bonded to a central Si atom within the AQAS anchoring groups. Assays confirm the potency of the AQAS oligomers against Staphylococcus aureus and Escherichia coli bacteria.