The Effect of Filler Content on the IR Spectra of Poly(p-xylylene)–Sulfide Nanocomposites

Abstract

The effect of the nature of a filler and its concentration (C ~ 0–100 vol %) on the IR spectra (500–4000 cm^–1) of thin nanocomposite films based on poly(p-xylylene) and sulfides (PPX–PbS, PPX–CdS, and PPX–S) was studied. Films with a thickness d ~ 0.5 μm are produced via low-temperature vapor deposition polymerization on silicon substrates. The common and specific variations in the IR-spectra of nanocomposite films are identified. The low-frequency shifts of C–H out-of-plane deformation vibrations of aromatic rings and the changes in characteristic band intensities of PPX are observed with increasing filler concentration. Additional IR-bands arise at 1000–1800 cm^–1 for PPX–PbS and PPX–CdS films and at 3100–3600 cm^–1 for PPX–CdS ones. However, the bands attributed to C–C and C–H stretch vibrations of the ring and С–Н deformation vibrations of СН₂-groups are found to lose much of their intensity in PPX–S films. The occurrence of complementary IR bands in nanocomposites is due to the formation of (1) complex sulfoxide phases with PbS nanoparticles, (2) C–O and C=O groups because of the oxidation of PPX polymer chains in the PPX–PbS films, and (3) complex compounds with sulfo (SO₄), hydroxyl (OH), and carboxylate (СОО^–) groups in the PPX–CdS films. Furthermore, some IR bands in PPX–PbS and PPX–CdS films are structural modifications of the substituted aromatic ring due to loss of symmetry.