Abstract: Polymeric materials, including polymers and polymer-composite materials, are useful for a variety of applications including biocidal coatings. Representative examples include a composite of silver salt particles and an ionic polymer. A novel process was developed whereby the counter-ion of an ionic polymer is precipitated as a metal salt, so as to form metal salt nanoparticles or microparticles within a polymer matrix. In other examples, polymers having cross-linkable silicon-containing groups form stable biocidal coatings on various substrates, including textiles. Biocidal activity may arise from silver salt particles (or other biocidal particles), ions (such as biocidal anions), membrane disruption by charged species, or some combination thereof. Further, bromide ions, such as provided by silver bromide particles, may impart fire retardant properties to textile substrates.