Separation and Quantification of Living Chains in Photoiniferter RAFT Block Copolymers via Solvent-Gradient HPLC

Visible-light photoiniferter RAFT polymerization enables highly controlled block copolymer synthesis with low dead chain formation; however, distinguishing living from dead chains remains challenging. Here, an α,ω-dihydroxyl-functionalized trithiocarbonate was used as a photoiniferter to synthesize poly(benzyl acrylate) (pBzA) and poly(benzyl acrylate-b-tert-butyl acrylate) (p(BzA-b-tBA)) under blue-light irradiation. Solvent-gradient HPLC (SG-HPLC) using a bare silica column then separated RAFT agent-derived living chains from dead chains through end-group polarity contrast installed by the dihydroxyl iniferter design. Living fractions accounted for ∼96% of the integrated 260 nm signal and 94.9 wt % of the recovered block copolymer, with chain-end fidelity enriched from ∼95% to >99% upon SG-HPLC isolation. MALDI–TOF MS of the isolated fractions gave apparent dispersities (ĐMALDI = 1.02–1.03), close to 1 + 1/DPn, supporting a near-ideal single population. This study demonstrates SG-HPLC as a practical route to separate and quantify living and dead chains in photoiniferter-mediated acrylic block copolymers.