Polymeric Capsules Prepared by in Situ Synthesis and Cross-Linking of Amphiphilic Copolymer by Atom Transfer Radical Polymerization

Abstract

A technique for encapsulation of polar organic solvents using atom transfer radical polymerization (ATRP) by suspension polymerization was developed to encapsulate diphenyl ether (solubility parameter δ = 20.9 MPa1/2) for the first time. An amphiphilic terpolymer was prepared by suspension polymerization, by first preparing poly(methyl methacrylate-co-poly(ethylene glycol) methacrylate), P(MMA-co-PegMA), oligomers in solution conditions, followed by addition of a cross-linking monomer, diethylene glycol dimethacrylate, to the polymerization solution, and then transfer of this oil phase to a stirred aqueous phase. The thermodynamic requirement for encapsulation of polar core oils is that the polymer has low interfacial tensions with both the oil phase and the water phase. Therefore, increasing the polarity of the copolymer by increasing its PegMA content (0−31 mol %) led to a transition in suspension particle morphology from matrix to multihollow and hollow particles. Furthermore, particles prepared with similar monomer feed ratios by conventional free radical polymerization (CFRP) did not exhibit a multihollow structure. We attribute this difference in ATRP and CFRP suspension particle morphology to the slow rate of the ATRP reaction which allows sufficient time for diffusion of the forming polymer chains to the oil−water interface, resulting in the thermodynamically favored hollow particle morphology.

Utility of atom transfer radical polymerization for the preparation of poly(methyl methacrylate) beads in an aqueous suspension

“…They found that a combination of two processes, liquid–liquid emulsion and solid–liquid dispersion polymerization, was operative. More recently, the copper‐mediated ATRP of MMA in an aqueous suspension of diphenyl ether was used to prepare crosslinked hollow polymer particles about 50–100 μm in diameter 14. Zhu et al15 reported ATRP of MMA in an aqueous suspension and found a typical ATRP behavior under direct suspension conditions, although they used a water‐soluble catalyst system (CuCl/bipyridine).…”

Gelation and Hollow Particle Formation in Nitroxide‐Mediated Radical Copolymerization of Styrene and Divinylbenzene in Miniemulsion

“…[59] To the best of our knowledge, the present work constitutes the first example of formation of hollow particles in a dispersed NMP process (Figure 8c). Hollow particle synthesis has previously been reported using ATRP [60,61] and RAFT. [62][63][64][65][66] The present results demonstrate that the SaPSeP method is applicable also to NMP systems, thus providing a convenient synthetic route to hollow polymer particles with a shell of comprising crosslinked polymer of high network homogeneity.…”

Synthesis of crosslinked poly(butyl methacrylate‐co‐pentaerythritol triacrylate) gel by single electron transfer‐living radical polymerization and its oil‐absorbing properties

“…During the FRP process, the slow initiation, fast chain propagation, and termination reactions result in the number of “dead” polymer chains increasing with time. Because of the dilute solution on the early stage, polymers of full length generate intramolecular crosslinking instead of overlapping each other, and then such chains are crosslinked together to form large molecules simultaneously absorbing more chains to produce microgels 10–22. This is undesired for ideal homogeneous polymer networks.…”