Synergistic strengthening of ion-exchange resins by post-crosslinking and selective sulfonation for PGMEA purification†

Abstract

PGMEA is widely used as a solvent and diluent for photoresists, yet developing an efficient resin that simultaneously resists organic dissolution and removes trace metal ions presents a significant challenge. To overcome this, a novel sulfonated hyper-cross-linked resin (2-CS-DVB-SO₃H) was synthesized through a multi-step process involving the preparation of a Cl-functionalized gel polymer, followed by sulfonation and post-crosslinking. The effects of the monomers, crosslinking degree, sulfonation degree, dosage, adsorption temperature, and resin stability on its purity performance were discussed. The resulting resin demonstrated exceptional stability in organic media and effectively purified PGMEA under optimized conditions (30% crosslinking, 4.69% S content, and 0.2 g mL⁻¹ resin dosage), with Ti, Co, Ni, and Cu metal ion concentrations reduced below 10 ppb. This process elevated PGMEA purity from 98.90% to 99.48%. Thermodynamic analysis revealed the adsorption to be non-spontaneous. The resin maintained chemical stability in PGMEA within 18 h. FT-IR and XPS data identified ion exchange, electrostatic interactions and lone electron pair coordination between sulfonic acid groups and metal ions as the binding mechanisms. The hydrogen bonds formed between Cl⁻ on the resin and hydroxyl groups in methanol (as organic impurities) were considered the primary factor responsible for enhancing the purity of PGMEA. These results collectively establish 2-CS-DVB-SO₃H as a robust and reliable material for metal ion removal in PGMEA purification, thereby improving the purity of photoresist solvents and potentially enhancing photoresist performance.

Keywords: Sulfonated resin; PGMEA; Metal ion removal; Purification mechanisms.