Structural features of disubstituted polyacetylenes with bulky substituents at double bonds

Abstract

The structural features of polyacetylenes carrying two substituents at double bonds with the gen eral formula [-C(CH 3 )=CR-] n , where R = Si(CH 3 ) 3 , -Ge(CH 3 ) 3 , or CH(CH 3 ) 2 , are studied. It is shown that the experimental IR and Raman spectra of the polymers and the theoretically calculated vibrational spectra for the model polymers consisting of three units coincide well with experimental data. All bands in the IR spectra are interpreted. The potential curves of internal rotation are calculated and constructed; high val ues of rotation barriers indicate a high rigidity of chains for all polymers of interest. The orthogonal arrange ment of neighboring monomer units and, as a result, the absence of electron density conjugation over the polymer chain are revealed. Charges on atoms and electron density on bonds of the monomer unit obtained from theoretical calculations indicate the presence of strong polarization of all bonds, including the -C=C-bond. This effect causes a shift in the frequencies of stretching vibrations due to double bonds in the IR spec tra of polyacetylenes with Si and Ge containing side substituents toward the longwave region. For polyacet ylene with hydrocarbon side substituents -CH(CH 3 ) 2 , such polarization is absent.

Stabilization of gas transport properties of PTMSP with porous aromatic framework: Effect of annealing

“…At the same time, in the presence of PAF-11, some spectral bands of PTMSP are seen to be distorted, in particular, two splitted peaks with a wavelength of 751 or 1243 cm -1 became wider, and their intensity ratio was changed. As was shown in [36], these two peaks corresponding to the deformation vibrations in the =С-Si(CH 3 ) 3 group are sensitive to conformational changes in PTMSP and polymer microstructure. Figure 13 illustrates that upon the addition of 10 wt.% of PAF-11, the absorption band at 748 cm -1 with a well-pronounced shoulder at 755 cm -1 in the spectra for virgin PTMSP is transformed into one broad and symmetric peak with a maximum at 750 cm -1 .…”

“…(1240-1250 cm -1 ) [23]. Moreover, as compared with the initial polymer, the swollen PTMSP experienced some conformational changes related to the transformation of the vibration of the =С-Si(CH 3 ) 3 segments: the bands at 1557 cm -1 (C=C bond) and at 1250 cm -1 (deformation vibrations of CH 3 -groups at Si-atom) and 750 cm -1 (=C-Si) [36]. PAF-11 filled PTMSP showed similar changes in the corresponding IR spectra: 750 cm -1 (see Figure 13), 1250 cm -1 (see Figure 14) and 1557 cm -1 (see Figure 11).…”

CO2 stripping from ionic liquid at elevated pressures in gas-liquid membrane contactor

“…Analysis based on quantum chemical calculations shows that =С-Si bond in the monomeric unit of PTMSP is strongly polar: a high positive charge (1.190 e) occurs on the silicon atom, and a significant negative charge (-0.363 е) occurs on the carbon atom at double bond [Legkov et al, 2012]. Given this, it can be assumed that the interaction of the RTIL with the polymer occurs due to the coordination of the cation and the anion of the RTIL towards oppositely charged PTMSP atoms.…”

Chemical Modification of Poly(1-Trimethylsylil-1-Propyne) for the Creation of Highly Efficient CO2-Selective Membrane Materials

“…Changes in the spectrum of the quaternized polymer are also observed for bands characterizing the bonds at the C=C–Si(CH 3 ) 2 CH 2 –Br site: the band is broadened and shifted from the double bond of 1536 cm –1 , the band shifts from 1221 cm –1 (δ SiCH2 ) to 1217 cm –1 , and the 680 cm –1 band, related to the bond stretching vibrations =C–Si [25], shifts to the region of long waves and strongly increases in intensity.…”