Controlling the Soft-Core–Hard-Shell Gradient Copolymer-Encapsulated Structure for Smooth Pigment-Based Inkjet Printing

Pigment-based inks are essential for developing short-process and cleaner inkjet printing technology for dyeing fabrics, eliminating the need for pretreatment and postwashing procedures. However, the size and morphology distribution of conventional pigment particles are relatively random, causing the trigger nozzle to clog and lowering the colorfastness of digital inkjet printing. In this work, comb-like pyrrolidinone-functional polyacrylate hyperdispersants were synthesized by reversible addition–fragmentation chain-transfer (RAFT) polymerization, and nanoscale pigment aqueous dispersion was prepared by controlling the sand grinding conditions. Subsequently, a series of film-forming gradient copolymer-encapsulated pigment latexes were prepared with a controlled microstructure via monomer sequence distribution, and the properties of binder-free fabric inkjet printing were measured. The resulting well-defined copolymers effectively dispersed C.I. Pigment Blue 15:3, C.I. Pigment Yellow 74, and C.I. Pigment Red 122 and outperformed a commercial dispersant (DNS-86), delivering smaller D50/D90 values. AFM force measurements revealed a high adsorption force (7.302 mN/m), consistent with strengthened pigment–polymer interfacial binding and improved deagglomeration. Moreover, the soft-core/hard-shell gradient copolymer-encapsulated pigment latexes exhibited a uniform spherical morphology and a characteristic broad glass-transition behavior, enabling a layered film-formation response that improved the filtration performance, color depth, and colorfastness of binder-free inkjet-printed fabrics relative to control formulations. Collectively, these comb-like pyrrolidinone-functional copolymers provide a dual-function platform that (i) enables robust nanoscale pigment dispersion for smooth jetting and (ii) offers a microstructure-control strategy for copolymer-encapsulated layers in binder-free pigment inks, advancing high-quality digital textile inkjet printing.