Unprecedented thermo‐ and ion‐responsive behavior of a non‐ionic water‐soluble polysilane

Abstract

Communications negative ion mode. methane): ' H NMR (300 MHz, CDC13): 6 = 4.38 (s, ZH), 7.18-7.95 (m, 28H): I3C NMR (250 MHz, CDCI,): 6 = : Elemental analysis calc. for C46H3"OZ (614.49): C 89.90, H 4.88; found: C 90.02, H 4.76.Thermogravimefric (TG) and Differential Scanning Calorimetric (DSC) Studies: Simultaneous TG-DSC measurements were performed using a TG-DSC 111 (SETARAM, France). The inclusion reaction of acetone from the gas phase was studied in isothermal mode at 25 "C. Inclusion was initiated by saturating the purge gas stream (argon) with acetone at 2 3°C using a temperature controlled saturator filled with liquid acetone. The relatively high concentration of acetone ensured complete and fast enclathration. For the investigation of the thermal degradation of the clathrates, the scanning mode with a linear heating rate of 5 Kimin was applied. Open aluminum crucibles and sample weights of approximately 3 mg were used for all experiments. Due to the symmetric design of both the microbalance and the calorimeter, blank effects were small and easy to correct.Single Crystal X-Ray Diffraction Analyses: Crystals of the inclusion compound suitable for X-ray analysis were obtained by slow evaporation from a solution of 1 in acetone.Data were collected on an ENRAF-NONIUS CAD 4 diffractometer with graphite-monochromatized Cu Ka-radiation at reduced temperature (155 K). Lattice constants and the orientation matrix were refined by least squares fit of 25 reflections in the 0-range 16.66-25.78". Intensities were obtained by the program HELENA [lS]. The standard reflections for intensity control were measured every 60 min and reflections for orientation control every 300th reflection, showing no decay of the crystal during data collection. An initial structure model was initiated by direct methods (SHELXS-86). All independent reflections with non-zero intensities were used to refine the final model to convergence by full matrix least squares (SHELXL-93). Isotropic temperature parameters were applied to the ordered non-hydrogen atoms. The hydrogen atoms were calculated from geometrical considerations and were refined as constrained to bonding carbon and oxygen atoms.Crystal data for 1 . acetone (1:3) monoclinic, P2,/c, a = 11.546 (3), h = 11.789(3), c = 31.598(3) A, p = 97.86(3)", Z = 4, D , = 1.230 gcm", p(CuKn) = 6.1 em-': 8751 independent reflections measured, 5464 observed reflections with I t 2u refined to R = 0.0637, BR = 0.1612. Further details of the crystal structure can be obtained from the Cambridge Crystallographic Data Centre. 12 Union Road, Cambridge CB2 1EZ (UK), on quoting the full journal citation.X-Ray Powder Diffracfion Analyses: Experiments were carried out by means of a horizontal goniometer HZG-4 (Prazisionsmechanik Freiberg, Germany) using C u K a radiation. A special closed sample chamber with a thin polyethylene window guaranteed stability of the clathrate during measurement by maintaining an acetone atmosphere above the sample.

Non-Ionic Water-Soluble Polysilanes and Polysilynes, Chameleons in Solution

“…strong solute-solvent interactions exist. Hence, in aqueous solution, 7 adopts an even more condensed random coil conformation with the polar oligo(oxyethylene) side chains extending into the water phase and the Si-CH 3 and Si-C 3 H 6 -groups positioned at the center of the coil, preserving the apoiar character of the backbone ('unimolecular micelle' analogue) (3,28). Thus, at room temperature, solvent polarity dictates the backbone structure of 7.…”

“…electroluminescence, microlithography, thermo-, piezo-, solvato-and surfacemediated chromism as well as thermoresponsive behavior (1,3). Introducing branching points in the silicon backbone branched polysilanes, viz.…”

Syntheses of poly[(dimethyl)-co-(4,7,10,13-tetraoxatetradecylmethylsilanes)].An evaluation of the use of C8K versus Na in the preparation of polysilanes

“…Apparently, the introduction of the dimethylsilane units does not influence the silicon backbone conformation, i. e. the dimethylsilane sequences do not introduce a higher degree of order in the backbone. [3,6] This is attributed to the occurrence of a slow single-chain transition from a disordered to a more ordered backbone conformation. 340 nm.…”

“…[1][2][3][4] They exhibit improved solubility properties and exhibit improved wettability for inorganic substrates in comparison to common alkyl and aryl functionalized polysilanes. [6] Another feature of polysilanes with ether sequences in their side chains is their ability to complex metal cations. Previously, we have reported that aqueous solutions of these polysilanes possess thermoresponsive properties.…”

“…[6] Another feature of polysilanes with ether sequences in their side chains is their ability to complex metal cations. [3,4] Since the low yields hampered their evaluation and, consequently, their potential application, Full Paper: To evaluate the use of C 8 K versus Na as the reducing agent in the preparation of polysilanes, the homopolymers poly(4,7,10,13-tetraoxatetradecylmethylsilanes) 1 and poly(dimethylsilane) 5 as well as the copolymers poly[(dimethyl)-co-(4,7,10,13-tetraoxatetradecylmethylsilanes)] 2 -4 were synthesized from 4,7,10,13-tetraoxatetradecylmethyldichlorosilane (6) and/or dimethyldichlorosilane (7). [8,9] Initially, these ether functionalized polysilanes were prepared using the conventional Wurtz-type coupling procedure (Na in toluene at reflux temperature), albeit in low yields (a 10%).…”