A novel polymeric emulsifier, SMTAPE, was prepared by end-capping sulfopolyester polyol with TMA in this study. This polymeric emulsifier is applied for BMA emulsion polymerization. Also investigated herein is how SMTAPE's chemical structures, e.g. SSIPM contents and molecular weights, influence the behavior of emulsion polymerization and subsequent PBMA lattices. Experimental results indicate that SMTAPE emulsifiers with a shorter average hydrophobic length stabilize the PBMA latex by the depletion mechanism. Although possessing good mechanical stability, using those emulsifiers has a higher coagulum during the synthesis stage. However, the SMTAPE emulsifiers with a longer average hydrophobic length anchor strongly on the PBMA latex particles and stabilize them by an electrostatic force with a negligible amount of steric stabilization. Although possessing better synthesis stability, using these emulsifiers has a poor mechanical stability. In addition, according to these experimental results, formation of the subsequent PBMA latex is attributed to a coagulation process of particle precursors, micellar particles as well as existing PBMA latex particles.