Ionic liquids as porogens for molecularly imprinted polymers: propranolol, a model study

Area of Science:

• Polymer Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Molecularly imprinted polymers (MIPs) are crucial for selective molecular recognition.
• Ionic liquids offer tunable properties for polymer synthesis and performance.
• Propranolol is a beta-blocker requiring selective analytical methods.

Purpose of the Study:

• To evaluate the selectivity and rebinding capacity of MIPs for propranolol.
• To investigate the influence of different room temperature ionic liquids (RTILs) as porogens.
• To compare MIP performance with traditional organic solvents.

Main Methods:

• Synthesis of MIPs using various RTILs ([BMIM][BF4], [BMIM][PF6], [HMIM][PF6], [OMIM][PF6]) and chloroform.
• Determination of imprinting factors (IF) and binding capacities.
• Characterization of MIPs using BET surface area, pore size analysis, and zeta potential measurements.
• Selective rebinding studies with propranolol, caffeine, and ephedrine.

Main Results:

• MIPCHCl3 exhibited the highest imprinting factor (IF = 4.64), signifying excellent selectivity for propranolol.
• MIPPF6 showed a lower binding capacity (5 μmol g−1) compared to MIPCHCl3 (7 μmol g−1).
• Surface properties (BET, pore size, zeta potential) varied significantly between MIPCHCl3 and MIPPF6.
• MIPPF6 performance was enhanced in methanol, with an increased IF (4.9) and binding capacity (48%).

Conclusions:

• Chloroform as a porogen yields MIPs with superior selectivity for propranolol.
• Ionic liquids, particularly [BMIM][PF6] in methanol, can enhance both binding capacity and selectivity.
• MIPs synthesized with optimized porogens and solvents show promise for propranolol recognition.