Preparation method for admixture for plasterboard, admixture prepared thereby, and composition for forming plasterboard comprising same

A method for preparing an admixture for a plasterboard, comprising subjecting a polystyrene to a sulfonation with a sulfonating agent comprising a sulfuric acid to give a sulfonated polystyrene (SPS)-based compound of Formula 1, and

• adding water to the sulfonated polystyrene (SPS)-based compound of Formula 1 to prepare the admixture for a plasterboard:
• wherein, in Formula 1,
• R1 and R2 are selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a nitro group, a C1-C20 alkyl group, a C2-C20 alkenyl group, a C2-C20 alkynyl group, a C1-C20 alkoxy group, a C3-C10 cycloalkyl group, a C6-C20 aryl group, a C1-C20 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group,
• a1 is an integer selected from 1 to 5,
• a2 is an integer selected from 1 to 4,
• M+ is H+, Li+, Na+, K+, or NH4+,
• x is an integer selected from 5 to 50,000, and
• y is an integer selected from 1 to 50,000,
• wherein a degree of sulfonation (DS) of the SPS-based compound is in a range of 15% to 60%.