Quantitative Evaluation of Cross-Linking Efficiency in Worm-like Nanoparticles Prepared via RAFT-Mediated Aqueous Emulsion PISA

Covalent cross-linking has been widely employed to stabilize the morphology of worm-like polymer nanoparticles. However, conventional qualitative evaluations of cross-linking efficiency are insufficient for further optimization of cross-linking conditions. In this study, a novel solvent-exchange method has been developed to quantitatively estimate the cross-linking efficiency of worm-like nanoparticles synthesized via reversible addition–fragmentation chain transfer (RAFT)-mediated aqueous emulsion polymerization-induced self-assembly (PISA). By integrating quantitative and qualitative analyses, the cross-linking efficiency and morphological stability of both in situ and post-cross-linking approaches were systematically compared. The results showed that in situ cross-linking consistently yielded high efficiency and better-preserved worm-like structures at lower cross-linker ratios. The present work provides a practical methodology for evaluation and optimization of cross-linking strategies in polymer nanoparticle synthesis.