Alexander Alentiev

Melting and recrystallization processes in a rubbery polymer detected by vapor sorption and temperature-modulated DSC methods

Series of successive absorption runs of n-hexane vapor in films of semi-crystalline poly(dimethylsilatrimethylene) at 25 °C are presented. Sorption overshoots were observed in the uptake kinetic curves of first series of absorption runs in as-prepared films. The said overshoots were absent in the second series of runs, conducted after desorption, while the sorption isotherms of the two series were identical. The overshoots are attributable to penetrant-induced melting and recrystallization phenomena. Strong support to this interpretation is given by temperature-modulated DSC data obtained from the pure polymer, which reveal similar thermally induced phenomena at slightly higher temperatures.

Enhanced gas separation factors of microporous polymer constrained in the channels of anodic alumina membranes.

New composite membranes based on porous anodic alumina films and polymer of intrinsic microporosity (PIM-1) have been prepared using a spin-coating technique. According to scanning electron microscopy, partial penetration of polymer into the pores of alumina supports takes place giving rise to selective polymeric layers with fiber-like microstructure. Geometric confinement of rigid PIM-1 in the channels of anodic alumina causes reduction of small-scale mobility in polymeric chains. As a result, transport of permanent gases, such as CH4, becomes significantly hindered across composite membranes. Contrary, the transport of condensable gases (CO2, С4H10), did not significantly suffer from the confinement due to high solubility in the polymer matrix. This strategy enables enhancement of selectivity towards CO2 and C4H10 without significant loss of the membrane performance and seems to be prospective for drain and sweetening of natural gas.

Effect of polymers chemical structure on the membrane characteristics

The comparative analysis of gas transport properties and conformational parameters of membranes obtained from two polyimides and polysulfone was made. It was shown that the introduction of a sulfone group instead of a methylene group in the amine component of polyimide leads to an increase in glass transition temperature and of polymer membrane permeability coefficient and a reduction in selectivity. Also it was demonstrated that the solvent used during the preparation of polymer membranes had a significant influence on their gas transport characteristics.