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The impact of double bond modification by gem -difluorocyclopropanation (gDFC) in poly(norbornenes) backbone on their gas transport properties was studied for the first time. With this aim the research of gDFC of polynorbornene (PNB) and poly(5-trimethylsilylnorbornene) (PNBSi) in the conditions of sodium chlorodifluoroacetate thermolyses at 180–190 °C in methyl benzoate solution were carried out. The starting poly(norbornenes) were synthesized via ring-opening metathesis polymerization of the corresponding monomers mediated by the first generation Grubbs’ catalyst. The degree of double bonds conversion into the gem -difluorocyclopropane and the molecular weight of modified polymers could be controlled by adjusting the reaction time, sodium chlorodifluoroacetate amount, and polymer concentration in reaction mixture, as well as by addition of inhibitor. The bulky Me 3 Si-substituent hindered the modification of double bonds in poly(norbornenes)’ backbone. The gDFC decreased the thermal stability of poly(norbornenes). However, the films of modified polymers demonstrated high stability during storage at the ambient conditions, especially in comparison with unmodified polynorbornene. The introduction of gem -difluorocyclopropane in poly(norbornenes) backbone increased their gas permeability coefficients P especially strongly for PNB. Simultaneously the values of ideal selectivity α ij = P i /P j were not changed or slightly increased. The noted growth of P was caused by increases in the solubility coefficients S. To elucidate the role of the two types of modification fragment ( CF 2 and O ) of double bonds a sample was prepared that included both types of the fragments. It was distinguished by increased P and α ij values. So, a new and simple approach improving the gas permeation properties of metathesis polynorbornenes was developed. It may be extendable to broader families of polydienes and other polymers containing double bonds in the backbone. [ABSTRACT FROM AUTHOR]

New bis-trimethylsilyl-substituted poly(tricyclo[4.2.2.02,5]deca-3,9-diene) (PTDDSi2) and poly(tricyclo[4.2.2.02,5]deca-3,7,9-triene) (PTDTSi2) were synthesized by ring-opening metathesis polymerization of the corresponding new monomers in the presence of 1st ‒ 3d generation Grubbs' catalysts. For monomer synthesis, the reaction of chlorosilanes with 1,3,5,7-cyclooctatetraene was studied for the first time. Polymerization conditions (catalyst type, temperature, monomer concentration) were selected to provide 77–96% yield of polymers. The monomer and polymer spatial structure had a significant effect both on their synthesis and on properties. The high Т g of PTDDSi2 (above the T d), as well as the easily proceeding retrodiene decomposition of the PTDTSi2 with the formation of bis(trimethylsilyl)benzene and polyacetylene (at 98 °C) indicated high rigidity of the polymer chain. A gas permeability investigations of mono-(PTDDSi), bis-Me 3 Si-substituted PTDDSi2 and hydrogenated product H-PTDDSi2 showed that PTDDs belong to the group of polymers with moderate gas permeability (P O2 up to 100 Barrer). Nonetheless, PTDDSi2 exhibited "solubility controlled permeability", which is unusual for moderately permeable polymers. [Display omitted] • New silicon-substituted monomers and polymers based on cyclooctatetraene were synthesized. • Steric factors were found to play an important role in the synthesis of the monomers and polymers studied. • The polymers obtained possess a rigid structure, which affects their thermal properties. • The polymers are middle-permeable, however tend to exhibit "solubility controlled permeability". [ABSTRACT FROM AUTHOR]

Abstract: A detailed study of gas permeation, thermodynamic properties and free volume was performed for a novel polymer of intrinsic microporosity (PIM-1). Gas permeability was measured using both gas chromatographic and barometric methods. Sorption of vapors was studied by means of inverse gas chromatography (IGC). In addition, positron annihilation lifetime spectroscopy (PALS) was employed for investigation of free volume in this polymer. An unusual property of PIM-1 is a very strong sensitivity of gas permeability and free volume to the film casting protocol. Contact with water in the process of film preparation resulted in relatively low gas permeability (P(O2)=120Barrer), while soaking with methanol led to a strong increase in gas permeability (P(O2)=1600Barrer) with virtually no evidence of fast aging (decrease in permeability) that is typical for highly permeable polymers. For various gas pairs (O2/N2, CO2/CH4, CO2/N2) the data points on the Robeson diagrams are located above the upper bound lines. Hence, a very attractive combination of permeability and selectivity is observed. IGC indicated that this polymer is distinguished by the largest solubility coefficients among all the polymers so far studied. Free volume of PIM-1 includes relatively large microcavities (R =5Å), and the results of the PALS and IGC methods are in reasonable agreement. [Copyright &y& Elsevier]

Amorphous and glassy polyhexafluoropropylene (PHFP) has been used for the first time as the matrix of mixed matrix membranes (MMMs). The preparation and the gas transport modeling of defect-free MMMs based on PHFP and 200 nm SAPO-34 crystals are described. By grafting SAPO-34 with perfluorinated tails the filler was well dispersed in the polymer and a good interfacial adhesion was guaranteed. The nano-particles determine a marked increase in gas permeability and a modest enhancement of the CO 2 /CH 4 permselectivity with respect to the neat polymer. Unexpectedly, the increase of permeability of the MMMs is not monotonous with the amount of SAPO-34. Following a recent approach, unrestricted gas diffusivity and solubility in SAPO-34 and PHFP are the inputs of the four-phase macroscopic modelling of gas transport through the MMMs. A four-phase approach to MMM modelling is dictated by the evidences of two distinct interfacial changes with respect to the ideal, nominal two phase MMM made of bulk-like SAPO-34 particles embedded in the pristine PHFP polymer matrix: a modified polymer phase of larger free volume (increasing permeability), which surrounds SAPO-34 particles, and barriers to the transport of gas (making the filler less permeable than PHFP), in the interior or on the surface of SAPO-34. The four-phase modelling, which delivers total gas transport features in excellent agreement with the experiments, is carried out by means of numerical optimization procedures based on a) Maxwell's effective medium analytical formulas, and b) a finite element solution of the transport differential equations. The latter approach reveals additional details, with respect to the first one, by delivering the different paths of gases through or around the SAPO-34 crystals in the MMMs. This work demonstrates the need to identify the real phenomena at work for a fruitful modelling of mass transport in MMMs, by overcoming the simplistic assumptions of MMMs obtained by the mere addition of the two original components. Image 1 • First polyhexafluoropropylene mixed matrix membranes have been prepared. • SAPO-34 improves both CO 2 permeability and CO 2 /CH 4 selectivity. • Larger polymer free volume and transport barriers at SAPO-34 coexist. • Both interfacial effects concur to the non-monotonous increase of permeability. • Analytical and numerical models of gas transport validate a 4-phase structure. [ABSTRACT FROM AUTHOR]