The visual results were corroborated by measurement of fiber
strength loss. The loss of breaking force in the case of fabric containing
0.5% of [DDA][NO3] was smaller than that observed for the
smaller concentration and unfinished samples (Fig. 4).
For antimicrobial agents, the mechanism of action is of great
importance. The mechanism of the QACs’ biological effect against fungi
lies in affecting synthesis of the fungal protoplasmic membrane.
Hydrophobic alkyl chains of these salts absorbed onto lipophilic areas
of protoplasmic membrane and dissolve in lipoproteins, leading to
a deformation of the permeability and biochemical function of
membrane. Subsequently, nucleoprotein complexes are ruptured and
cells die (Ikeda and Tazuke, 1985). The QACs containing two long alkyl
chains or one alkyl and one aryl chain are effective fungicides. The
highest efficiency is observed for the salts containing alkyl substituent
with 8e18 carbon atoms, as in these salts there is a balance between
lipophilic and hydrophilic parts of the compound, and this balance
ensures optimum microbiological activity. The studied IL contains
two alkyl substituents with 10 carbon atoms, which probably
increased its antifungal activity. Earlier studies indicated that addition
of as little as 8 mg [DDA][NO3] per 1 g of the dry fabric was effective
against bacteria (Foksowicz-Flaczyk and Walentowska, 2008). The
results of these studies show that [DDA][NO3] is also effective against
mould fungi too, but only in the highest concentration tested.