Better RAFT Control is Better? Insights into the Preparation of Monodisperse Surface-Functional Polymeric Microspheres by Photoinitiated RAFT Dispersion Polymerization

Abstract

Efficient synthesis of polymeric microspheres with high uniformity, well-defined surface functionality, and precise diameter and composition has long been a challenging goal in polymer science. Herein, we exploited photoinitiated reversible addition–fragmentation transfer (RAFT) dispersion polymerization of methyl methacrylate using poly­(glycerol monomethacrylate)-based macromolecular chain transfer agents (macro-CTAs). We showed that the use of a binary mixture of macro-CTA and CTA with poor controllability was crucial for obtaining monodisperse poly­(methyl methacrylate) (PMMA) microspheres. Evolution of PMMA microspheres during the polymerization was followed by scanning electron microscopy and 1H NMR spectroscopy, confirming a linear evolution of particle volume with monomer conversion. PMMA microspheres with better colloidal stability were obtained when increasing the amount of macro-CTA used in photoinitiated RAFT dispersion polymerization. Finally, a two-stage photoinitiated RAFT dispersion polymerization was also explored by adding additional monomers in the second stage. We demonstrated that the particle size of polymeric microspheres could be precisely controlled by adding different amounts of the monomer in the second stage. Moreover, polymeric microspheres composed of two polymers were also prepared by adding a different monomer in the second stage. This study not only optimizes reaction conditions for preparing monodisperse surface-functional polymeric microspheres but also provides mechanistic insights into photoinitiated RAFT dispersion polymerization.

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“…They demonstrated that the nucleation stage of photoinitiated RAFT dispersion polymerization became long and robust, allowing the preparation of functional polymeric microspheres by adding functional reagents at the beginning (Figure ). This attractive method can be further extended by employing different monomers and stabilizers for preparing a variety of uniform polymeric microspheres. − …”

Light-intensity switch enabled nonsynchronous growth of fluorinated raspberry-like nanoparticles

“…The nonlinear relationship between the colloidal volume and exposure time (Fig. S5 †) 37 suggests that a secondary nucleation could take place during the photo-RDRP process.…”

“…The employment of light as a low-cost and environmentally sustainable stimulus in RDRP [22][23][24][25][26][27][28][29][30][31][32] (i.e., photoinduced electron transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization) [33][34][35] has aroused a lot of interest, promoting the preparation of polymeric colloids without intermediate purication. [36][37][38][39] Motivated by the outstanding physicochemical properties of uoropolymers, 40,41 we have developed photo-RDRP of uorinated alkenes. 42,43 While the uorine-uorine (F-F) interaction has been adopted to generate various morphologies, [44][45][46][47] the preparation of uorinated RB particles remains unexploited.…”

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“…The diameter of PHPMA microspheres prepared by using PPEGA-based macro-RAFT agents could be precisely controlled via a two-step seeded polymerization. Similarly, Yu et al [204] reported a photoinitiated RAFT dispersion polymerization of methyl methacrylate (MMA) by using a binary mixture of a poly(glycerol monomethacrylate) (PGMA)-based macro-RAFT agent and a small molecular RAFT agent. The chain transfer constant of the PGMA macro-RAFT agent was decreased by introducing a short poly(2-methoxyethyl acrylate) (PMEA) block.…”