We studied dispersion polymerization in detail using well-defined pH-responsive poly[2-(diethylamino)ethyl methacrylate]- (PDEA-) based macroinitiators as an inistab (initiator + stabilizer). Colloidally stable polystyrene (PS) latex particles carrying pH-responsive PDEA hair (PDEA PS particles) were successfully synthesized in polymerization media with solubility parameters ranging between 22.3 (MPa)(1/2) and 26.0 (MPa)(1/2). The number-average particle diameters were finely controlled between 90 and 460 nm. The PDEA PS latex particles were dispersed in acidic aqueous media in which the PDEA hair was protonated and solvated, and were flocculated in basic aqueous media in which the PDEA hair was deprotonated and precipitated. The dried PDEA-PS particles served as an effective gas-responsive stabilizer for liquid marbles. The liquid marbles were stable in H2O vapor for over 18 h, but disintegrated immediately (<2 s) upon exposure to HCl gas.