Reversible Droplet Bridging and Tunable Viscoelasticity in Emulsions Using Biocompatible PLA- b -PEO- b -PLA Telechelic Block Copolymers: Implications for Injectable Emulsion Gels

Telechelic polymers are known to form reversible networks through end-group association; however, their application as structuring agents in emulsion-based soft materials remains underexplored. Herein, we systematically investigate the biocompatible amphiphilic triblock copolymer poly(d,l-lactic acid)-block-poly(ethylene oxide)-block-poly(d,l-lactic acid)(PLA-b-PEO-b-PLA) as a rheology modifier in toluene-in-water model emulsions. Owing to the selective adsorption of PLA end blocks at the oil–water interface and the solvation of the PEO midblock in the aqueous phase, this polymer is expected to form reversible droplet-bridging networks. During the process, the polymer concentration, molecular weight of the mid and end blocks, and the dispersed phase volume fraction were adjusted, and the factors governing network formation were elucidated using oscillatory rheology and stress-relaxation measurements. The results show that anchoring of the PLA end blocks and PEO-mediated bridging predominantly control the strength and dynamic reversibility of the network. Step-strain experiments further reveal that the droplet-bridging interactions can be disrupted under large deformation and partially recover when small-strain conditions are restored, confirming the presence of reversible physical associations. These findings establish a molecular design strategy for biodegradable telechelic copolymers as effective and reprocessable structuring agents in emulsion gels. The shear-responsive, tunable, and reversible nature of the droplet-bridging network makes this material platform particularly suitable for injectable emulsion gels for advanced soft matter and biomedical engineering applications.