Preparation of microcapsules using a poly(2-(dimethylamino)ethyl methacrylate)-b-poly(benzyl methacrylate) diblock copolymer emulsifier

Most encapsulation techniques require suitable polymers or surfactants to stabilize the microcapsule suspension. Typically, such stabilizers are present in excess in the aqueous continuous phase. In this study, the use of a poly(2-(dimethylamino)ethyl methacrylate)-poly(benzyl methacrylate) (PDMA-PBzMA) diblock copolymer is examined as an efficient stabilizer for the preparation of three types of methacrylic microcapsules with different morphologies. Unlike conventional water-soluble stabilizers, this amphiphilic copolymer is dissolved directly in the dispersed organic phase. This approach minimizes the amount of stabilizer present in the aqueous continuous phase and hence maximizes the formulation efficiency. This new PDMA-PBzMA stabilizer enables either poly(benzyl methacrylate) (PBzMA) or poly(methyl methacrylate) (PMMA) microcapsules to be prepared with excellent colloidal stability and shell integrity, comparable to that previously achieved using poly(vinyl alcohol). Such formulations can produce (i) monolithic microcapsules, (ii) oil-core microcapsules via internal phase separation, or (iii) aqueous-core microcapsules via water-in-oil-in-water (w1/o/w2) double emulsification. In particular, PBzMA microcapsules exhibited an exceptionally slow release of the encapsulated hydrophobic model active pyrene. Diffusivities of the encapsulated active species on the order of 1 × 10-20 m2 s-1 were determined by fitting release data to appropriate models assuming Fickian diffusion. For such microcapsules, the PBzMA shell matrix acted as the primary release-rate-limiting factor. Given that PDMA-PBzMA diblock copolymers can be conveniently prepared via polymerization-induced self-assembly (PISA), this study highlights their potential as a versatile, efficient stabilizer for a broad range of microcapsule formulations.