| 11456674 |
Zmolek PB, Sohn H, Gantzel PK, Trogler WC: Photopolymerization of liquid carbon disulfide produces nanoscale polythiene films. J Am Chem Soc. 2001 Feb 14;123(6):1199-207.
Broad band solar or 300--400 nm irradiation (Hg--Xe arc source) of liquid-phase carbon disulfide produces a new carbon--sulfur polymer with the approximate (n = 1.04--1.05) stoichiometry (CS (n))(x). The polymer, from here on called (CS)(x), forms as a approximately 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 (CS (2))(x) and the high-pressure-phase polymer of CS (2), 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 (CS (2))(x), (13) C labeling and model compound studies of alpha-(C (3) S (5)) R (2) and beta-(C (3) S (5)) 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-(C (3) S (5))(C (O) C (6) H (5))(2), determined at -84 degrees C, belongs to space group P1, with a = 7.486 (5) A, b = 13.335 (11) A, c = 17.830 (13) A, alpha = 105.60 (6) degrees, beta = 95.32 (6) degrees, gamma = 90.46 (6) degrees, Z = 4, V = 1706 (2) A (3), R = 0.0785, and R (w) = 0.2323. With use of electron and chemical ionization mass spectrometry, C (4) S (6) and C (6) S (7) 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 (CS (2))(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 S (2) C=CS (2) is proposed. |
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