Transport properties of silmethylene homo-polymers and random copolymers: experimental measurements and molecular simulation

A novel class of silicon-containing rubbers is proposed as membrane materials for separation of hydrocarbons of natural and associated petroleum gas. Homo-polymers of general formulas –Si(CH3)2CH2– (PDMSM) and –Si(CH3)2CH2CH2CH2– (PDMSTM) and the copolymers with the same randomly alternating repeat units were prepared by thermal initiated polymerization of strained silicon-containing four-member cycles. These polymers have low glass transition temperatures and reveal solubility controlled gas permeation properties. The highest permeability is characteristic for PDMSM, however, it has poor film forming properties. On the other hand, amorphous copolymers exhibit combination of good film forming properties and relatively high permeability. Transport properties of PDMSM were successfully simulated by molecular dynamics using a very efficient united-atom force field.