Mechanism for the formation of PNIPAM/PS core/shell particles

Abstract

A multi-stage polymerization method was previously used to prepare PNIPAM/PS core/shell particles that exhibited uniform "raspberry-like" structures. In this current study, this polymerization process was carefully investigated in order to elucidate the PS (polystyrene) shell formation mechanism. The results indicated that the "raspberry" structure is due to heterocoagulation of polystyrene domains onto PNIPAM (poly(N-isopropylacrylamide)) particle surfaces. Different sizes and numbers of the PS domains can be obtained by varying the styrene feed rate. It was also found that linear PNIPAM may increase the compatibility between PNIPAM and PS polymers. In addition, this heterocoagulation mechanism for forming structured particles was successfully applied to a PNI-PAM and Ludox V R colloidal silica nanoparticle system where a core/shell structure was also obtained. V C 2013 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2014, 131, 40124.

Heterocoagulation of alumina and quartz studied by zeta potential distribution and particle size distribution measurements

“…Heterocoagulation can be employed to prepare special samples, e. g., raspberry-like aggregates can be prepared by attaching a lot of small surrounding particles to one large core particle [1][2][3]. Heterocoagulation can also be applied to increase the stability of charged particles in water [4,5].…”

Localization of Polystyrene Particles on the Surface of Poly(N-isopropylacrylamide-co-methacrylic acid) Microgels Prepared by Seeded Emulsion Polymerization of Styrene

“…Compared with hydrogel core–hydrogel shell microgels, core–shell microgels whose shells are solid materials have been scarcely reported in the literature. − Our group has recently reported solid nanomaterial-composited microgels synthesized by seeded emulsion polymerization with microgels used as seeds. , Specifically, we chose monodispersed poly­( N -isopropylacrylamide) (pNIPAm) microgels as seeds. Monodispersed pNIPAm microgels can be synthesized by precipitation polymerization, and pNIPAm is a representative temperature-responsive polymer with an LCST of approximately 31.8 °C. , Therefore, cross-linked pNIPAm microgels can swell/deswell in response to temperature .…”

Aqueous poly(vinyl acetate)-based core/shell emulsion: synthesis, morphology, properties and application

“…When styrene was used as secondstage monomer, the "raspberry" structure was rstly formed due to heterocoagulation of hydrophobic PSt domains onto PVAc core surface. 68 When increasing the conversion of styrene monomer, these PSt domains could gradually grow, touch each other, and build up an entire shell phase. When vinyl acetate was second-stage monomer, the shell phase was almost complete from the beginning due to its hydrophilicity.…”