Phthalide-containing poly(ether-imide)s based thermal rearrangement membranes for gas separation application

Area of Science:

• Polymer Science
• Materials Science
• Chemical Engineering

Background:

• Development of advanced membrane materials for efficient gas separation is crucial.
• Poly(ether imide)s (PEI) offer promising properties but often require modification for enhanced performance.
• Phthalide-containing polymers present unique opportunities for thermal rearrangement and crosslinking.

Purpose of the Study:

• To synthesize a novel diamine monomer, 3,3-bis[4-(3-hydroxy-4-amino-phenoxy)phenyl]phthalide (BHAPPP).
• To prepare a series of phthalide-containing poly(ether imide)s (PEI) via polycondensation with various dianhydrides.
• To investigate the gas separation performance of thermally rearranged (TR) membranes derived from these PEIs.

Main Methods:

• Synthesis of BHAPPP monomer through nucleophilic substitution and reduction.
• Polycondensation of BHAPPP with six different dianhydrides (6FDA, BTDA, BPDA, ODPA, CBDA, PMDA).
• Thermal imidization followed by thermal rearrangement (TR) treatment to form membranes.

Main Results:

• TR membranes exhibited significantly enhanced gas separation properties with increasing thermal treatment temperature.
• TR(BHAPPP-6FDA) membrane showed high permeability for CO2 (258.5 Barrer) and H2 (190.5 Barrer).
• CO2/CH4 selectivity of 120.2 exceeded the 2008 Robeson limit, and O2/N2 selectivity of 9.02 approached the 2015 upper limit.

Conclusions:

• The phthalide lactone ring in PEIs facilitates simultaneous thermal rearrangement and crosslinking.
• TR membranes derived from phthalide-containing PEIs demonstrate superior gas separation capabilities.
• These advanced membranes hold significant potential for practical applications in gas separation technologies.