Block copolymers composed of polymer segments of sufficiently high molecular weight such that microphase separation and self-assembly into complex nanostructured materials can occur provide a pathway to a myriad of nano-engineered materials with applications ranging from nanomedicine to materials science and microelectronics. In the present work, we have developed a methodology based on reversible addition−fragmentation chain transfer polymerization that allows the synthesis of multiblock copolymers based on sequential aqueous emulsion polymerization using the three most common industrially employed monomer families in emulsion polymerization systems: methacrylates, acrylates, and styrene. By exploiting the segregation effect (compartmentalization) resulting from polymerization within polymeric nanoparticles, a high molecular weight multiblock copolymer (up to 140,000 g•mol −1 ) is obtained in a relative short time period of 3 h for each cycle of polymerization. The concept of nano-engineering of polymer nanoparticle morphology is demonstrated by exploiting the ability to covalently link numerous polymer blocks that are chemically incompatible, resulting in microphase separation and the formation of a well-defined multilayered structure within the nanoparticles. The method developed is environmentally friendly (use of water as solvent) and fulfills all requirements for scale up to an industrial process using existing industrial equipment such as no intermediate purification steps, relatively high solid content, good colloidal stability with no flocculation/coagulation, and near full monomer conversion.

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It is demonstrated that the degree of livingness (chain‐end fidelity) in RAFT polymerization for a given degree of polymerization can be markedly increased in miniemulsion polymerization relative to the corresponding homogeneous bulk system. Polymerization of styrene was conducted using a poly(methyl methacrylate) benzodithioate as macroRAFT agent in both miniemulsion and bulk. The substantially higher polymerization rate in miniemulsion, which is attributed to the segregation effect (compartmentalization) causing a reduction in the rate of bimolecular termination, makes it possible to reach a given degree of polymerization in a significantly shorter time than in the corresponding bulk system. As a consequence, fewer initiating radicals are required throughout the polymerization, leading to higher livingness in the more rapid miniemulsion system. It is demonstrated how this approach facilitates synthesis of high‐molecular‐weight block copolymers comprising slowly propagating monomers such as styrene and methacrylates. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1938–1946

Synthesis of multicompositional polymeric nanoparticles of diameters 100-150 nm comprising well-defined multiblock copolymers reaching from the particle surface to the particle core was conducted using surfactant-free aqueous macroRAFT emulsion polymerization. The imposed constraints on chain mobility as well as chemical incompatibility between the blocks result in microphase separation, leading to formation of an onion-like multilayered particle morphology with individual layer thicknesses of approximately 20 nm. The approach provides considerable versatility in particle morphology design as the composition of individual layers as well as the number of layers can be tailored as desired, offering more complex particle design compared to approaches relying on self-assembly of preformed diblockc opolymers within particles.M icrophase separation can occur in these systems under conditions where the corresponding bulk system would not theoretically result in microphase separation.

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