Photopolymerization of liquid carbon disulfide produces nanoscale polythiene films

Broad band solar or 300-400 nm irradiation (Hg-Xe are source) of liquid-phase carbon disulfide produces a new carbon-sulfur polymer with the approximate (n = 1.04-1.05) stoichiometry (CSn)(x). The polymer, from here on called (CS)(x), forms as a similar to 200 nm thick transparent golden membrane as measured by SEM and AFM techniques. IR spectra for this polymer show some similarities with those obtained for the gas-phase photopolymerized (CS2)(x) and the high-pressure-phase polymer of CS2, called Bridgman's Black. The observed FT-IR absorptions of (CS)(x) include prominent features at 1431 (s, br), 1298 (m), 1250 (ms), and 1070 cm(-1) (m). In contrast to previous proposals for (CS2)(x), C-13 labeling and model compound studies of alpha-(C3S5)R-2 and beta-(C3S5)R-2 (R = methyl or benzoyl) suggest that the absorption at 1431 cm(-1) and those at 1298 and 1250 cm(-1) are indicative of carbon-carbon double bonds and carbon-carbon single bonds, respectively. The molecular structure of alpha-(C3S5)(C(O)C6H5)(2), determined at -84 degreesC, belongs to space group P (1) over bar, with a = 7.486(5) Angstrom, b = 13.335(11) Angstrom, c = 17.830(13) Angstrom, alpha = 105.60(6)degrees, beta = 95.32(6)degrees, gamma = 40.46(6)degrees, Z = 4, V = 1706(2) Angstrom (3), R = 0.0785, and R-w = 0.2323. With use of electron and chemical ionization mass spectrometry, C4S6 and C6S7 were identified as the dominant soluble molecular side-products derived from a putative ethylenedithione (S=C=C=S) precursor. Atomic force microscopy (AFM) provided surface topology information for the thin film (CS)(x) and revealed features that suggested the bulk material is formed from small polymer spheres 20-50 nm in size. Both (CS2)(x) and (CS)(x) are extensively cross-linked through disulfide linkages and both materials show strong EPR resonances (g > 2.006) indicative of sulfur-centered radicals from incomplete cross-linking;. A polymerization mechanism based on the intermediacy of S2C=CS2 is proposed.