Synthesis and characterization of polyamideimide-branched siloxane and its gas-separation

Abstract

Polyamideimide-branched siloxanes (PAIBrSs) were synthesized from 4, 4Ј-(hexafluoroisopropyllidene)diphthalic anhydride (6FDA), p,pЈ-oxydianiline (ODA), and aminopropyl-terminated oligomeric dimethylsiloxane (ODMS). In this investigation, a mixture of N-methylpyrrolidinone (NMP) and tetrahydrofuran (THF) was used as a cosolvent for the homogeneous mixing of poly(amic acid) (PA) and the ODMS solution. Thionyl chloride (SOCl 2 ) was used for the acylation of PA to activate the reaction between PA and ODMS. FTIR spectra showed an increase in the intensity of characteristic absorption peaks of dimethylsiloxane units with the amount of ODMS reacted. From thermogravimetric analysis (TGA), PAIBrSs showed good thermal stability, but relatively low thermal stability when compared with that of block poly(imide siloxane) (PIBlS) or poly(amideimide siloxane) (PAIBlS). A solubility test showed that dipolar aprotic solvents were relatively good solvents for the polymer. Gas separation was performed by single gas-permeation equipment. The permeabilities of PAIBrS membranes are higher than those of PIBlS membranes and the selectivities of PAIBrS membranes are lower than those of PIBlS membranes.

Poly(dimethylsiloxane-urethane) membranes: Effect of hard segment in urethane on gas transport properties

“…Limitation with this polymer is its poor mechanical properties and poor selectivity value for a particular gas in a mixture of gases. Therefore, many investigations have been carried out to improve the mechanical properties of PDMS and also to obtain a high permselective membrane by introducing functional groups to the side or the main chains of PDMS [13,14] and also a block copolymer with polyamide, polyimide and polycarbonate [15][16][17]. The study of gas transport property through polyurethane membranes is especially interesting because the molecular structure of the polymer chain can be easily changed.…”