ИСТИНА

Silicon-containing disubstituted polyacetylene poly(1-trimethylsilyl-1-propyne) (PTMSP) exhibits the highest gas and organic vapor permeability and selectivity during recovery of C3+ from mixtures with permanent gas. Unique properties of PTMSP and a number of other high-permeable disubstituted polyacetylenes are provided by a specific organization of nanospace in these polymers, namely, extremely high fractional free volume and interconnected free volume elements. The specific structure is formed by rigid backbone containing C=C bonds and bulky substituents. The unusual high selectivities of recovery of higher hydrocarbons from vapor-gas mixtures are attributed to predominant sorption of organic vapor (e.g. butane) in nanosized pores (free volume holes), and therefore subtle variation of structure on nanolevel can provide means of developing novel effective polymer materials. Detailed investigation of synthesis of Si-containing polyacetylene PTMSP and its Ge-containing analogue poly(1-trimethylgermyl-1-propyne) (PTMGP) in the presence of catalytic systems based on Nb and Ta pentachlorides has shown that by varying synthesis conditions, e.g. cocatalyst, solvent polarity and temperature of polymerization process, one can regulate the geometric structure of macrochains, i.e. the ratio of units of cis- and trans-configuration, that determines macrochains packing and submolecular organization of the polymer 1. It was shown that functional properties of disubstituted polyacetylenes such as transport characteristics as well as stability towards organic solvents are controlled by the geometric structure 1,2. In this study disubstituted polyacetylenes PTMSP and PTMGP with different specific geometric structure (calculated from the 13C NMR spectra) were synthesized by methods of stereospecific polymerization with the use of catalytic systems based on Nb and Ta halides. An investigation of submolecular organization, utilizing PALS, N2 sorption and AFM, for PTMSP and PTMGP with different geometry was performed. All techniques indicate that polymers depending on the microstructure have distinct dissimilarities in free volume holes or pores. The PALS shows that polymers are composed of two types of free volume holes (τ3 and τ4) and it reveals differences both in amount and in structure of hole free volume in polymers with the same chemical structure (both PTMSP and PTMGP) but with different cis-/trans- composition. It was observed that polymers with bigger hole free volume demonstrate higher n-butane permeability as well as n-butane/methane mixed-gas selectivity in permeability experiments carried out for n-butane/methane mixtures (content of n-butane 1.6 mol.%). According to low-temperature nitrogen adsorption BET measurements the sorption capacity as well as the surface area of polymers with higher permeability and mixed n-butane/methane selectivity is greater than for polymers with lower permeability. AFM shows that the surface topography of polymer films consists of clusters with different lateral size. The observed correlation between increasing the size of cluster and enhancement of permeability as well as a mixed n-butane/methane selectivity indicates that the size of clusters influence on polymer packing density which governs gas transport through polymer matrix. This work was supported by RFBR (project № 11-03-00343-а).