Preparation of mesoporous and nanocomposite fibrous polymer materials based on commercial poly(ethylene terephthalate) (PET) fibers with high density of crazes (HCD fibers) via environmental crazing (EC) is described. Multiple crazes in pristine PET fibers were initiated by the precrazing procedure, and the density of the initiated crazes in the starting HCD fibers is equal to ∼200 crazes per mm. The scenario of environmental crazing of the HCD PET fibers was studied by online microscopic observations. The mechanism of environmental crazing of the HCD fibers is found to be different from the classical well-known scheme: new crazes are initiated over a broad interval of tensile strains of up to 250%, splitting of thin craze walls takes place, and the collapse of the fibrillar-porous structure of crazes is prevented. The HCD fibers preserve their porosity even upon the complete removal of the physically active liquid environment from the volume of crazes. As a result, the overall porosity of the HCD fibers can reach ∼60 vol % and pore dimensions are estimated to be below ∼6 nm. Applied properties of the mesoporous HCD fibers (gas storage potential, sorption, insulating properties) are studied. The bottom-up synthesis of silver nanoparticles in the mesoporous HCD fibers via reduction of silver ions is described, and the resultant silver-containing nanocomposite fibers are characterized by a uniform distribution of silver nanoparticles with an average size of 3 nm. The silver content in the HCD fibers is 6 times higher than that in the pristine PET fibers with the same tensile strain. The silver-loaded fibers show high bactericidal activity against Gram-positive ( Staphylococcus aureus) and Gram-negative bacteria ( Escherichia coli) and antifungal activity against Candida guilliermondii. The proposed EC approach allows preparation of sustainable mesoporous polymeric fibers and related functional nanocomposite materials with valuable functional properties for diverse applications.
Keywords: antibacterial and antifungal properties; crazes; environmental crazing; mesoporous polymer fibers; nanocomposite materials; silver nanoparticles.