Selective radical cyclopolymerization of a bifunctional vinyl monomer derived fromN-vinylacetamide

Decomposing Oil-Soluble Initiators in Particles: A Template-Free Method for the Preparation of Hollow Polymer and Silica Particles

Nanovoids contained in hollow particles render them potential drug carriers. However, conventional methods for the synthesis of these particlhes involve complex processes. In this study, we developed a template-free method for the synthesis of hollow polymer and silica particles by initially preparing polystyrene core particles containing 2,2'-azobis(2-methylbutyronitrile) (V-59) through soap-free emulsion polymerization. The subsequent generation of nitrogen gas inside these particles upon the decomposition of V-59 at 70 °C led to the formation of voids. In addition, silica shells were synthesized on the surfaces of the V-59-containing polystyrene core particles through a sol-gel reaction at 40 °C, following which voids were formed by the decomposition of V-59 at 70 °C. The developed method involves straightforward steps and is environmentally friendly, as it does not require the use of surfactants, organic solvents, or templates.

Cyclopolymerizations: Synthetic Tools for the Precision Synthesis of Macromolecular Architectures

Monomers possessing two functionalities suitable for polymerization are often designed and utilized in syntheses directed to the formation of cross-linked macromolecules. In this review, we give an account of recent developments related to the use of such monomers in cyclopolymerization processes, in order to form linear, soluble macromolecules. These processes can be activated by means of radical, ionic, or transition-metal mediated chain-growth polymerization mechanisms, to achieve cyclic moieties of variable ring size which are embedded within the polymer backbone, driving and tuning peculiar physical properties of the resulting macromolecules. The two functionalities are covalently linked by a "tether", which can be appropriately designed in order to "imprint" elements of chemical information into the polymer backbone during the synthesis and, in some cases, be removed by postpolymerization reactions. The two functionalities can possess identical or even very different reactivities toward the polymerization mechanism involved; in the latter case, consequences and outcomes related to the sequence-controlled, precision synthesis of macromolecules have been demonstrated. Recent advances in new initiating systems and polymerization catalysts enabled the precision syntheses of polymers with regulated cyclic structures by highly regio- and/or stereoselective cyclopolymerization. Cyclopolymerizations involving double cyclization, ring-opening, or isomerization have been also developed, generating unique repeating structures, which can hardly be obtained by conventional polymerization methods.