Effect of molecular weight on the production of multi-hollow polymer particles by the alkali/cooling method

Multiblock copolymer synthesis via aqueous RAFT polymerization-induced self-assembly (PISA)

Employing RAFT PISA emulsion polymerization to synthesize high molecular weight hexablock multiblock copolymers.

Preparation of microcapsules containing a curing agent for epoxy resin by polyaddition reaction with the self-assembly of phase-separated polymer method in an aqueous dispersed system

To prepare cured epoxy resin particles encapsulating a curing agent (diamine), the self-assembly of phase-separated polymer (SaPSeP) method was developed to be applicable to polyaddition reaction of a stoichiometrically imbalanced system. The SaPSeP method was developed by the authors for preparation of micrometer-sized, hollow cross-linked polymer particles by radical polymerization based on the self-assembly of phase-separated polymer at the inner interface of particles. Although a polyaddition reaction, in general, requires that the reactants are in stoichiometric balance for the cure reaction to proceed well, diamine was successfully encapsulated within a cured epoxy resin shell by utilizing the SaPSeP method regardless of stoichiometric imbalance. The results provide further support of the previously proposed SaPSeP mechanism for the formation of hollow particles. Moreover, such diamine capsules can be employed in one-component epoxy adhesives.

Hydrophobic Core/Hydrophilic Shell Amphiphilic Particles

Amphiphilic colloidal particles with hydrophobic cores and hydrophilic shells were prepared via a two-step method. First, polystyrene cores were obtained through the concentrated emulsion polymerization. A mixture of styrene, ethyl benzene, divinyl benzene, azobisisobutyronitrile, and cumene hydroperoxide (CHPO) was partially polymerized at 80 degrees C for 40 min and subsequently used as the dispersed phase of a concentrated emulsion in water. The concentrated emulsion was subjected to complete polymerization at 60 degrees C for 12 h; colloidal particles of crosslinked polystyrene were thus obtained. In the second step, the polystyrene particles were dispersed in water, after which acrylamide, N,N'-methylenebisacrylamide, and ferrous sulfate (FS) were added. The system was heated (typically at 30 degrees C) to conduct the polymerization of the hydrophilic monomers. The CHPO present on the surface of the polystyrene particles and the FS present in the aqueous phase (both together constitute a redox initiator) ensured that the initiation occurred mostly on the surface of the particles and that the hydrophilic polymer obtained formed a shell encapsulating the particles. Under proper conditions, a porous outer shell could be generated, making the hydrophobic core accessible to the outside medium. Copyright 2001 Academic Press.