Synthesis of Narrowly Size-Distributed Thermosensitive Poly(N-isopropylacrylamide) Nanocapsules in Inverse Miniemulsion

Abstract

Narrowly size-distributed thermosensitive poly(N-isopropylacrylamide) (PNIPAM) nanocapsules with a hydrophilic core composed of an aqueous solution of cobalt tetrafluoroborate (CoTFB) were synthesized via a one-pot polymerization of N-isopropylacrylamide (NIPAM) and the cross-linking agent N,N′-methylene bis(acrylamide) (MBA) in inverse miniemulsion. CoTFB not only worked as template and lipophobe, but also promoted the dissolution of NIPAM in water by the formation of a complex between NIPAM and CoTFB. The formation of PNIPAM nanocapsules was verified by transmission electron microscopy (TEM) and atomic force microscopy (AFM). This is the first report to synthesize nanocapsules in inverse miniemulsion by following a phase separation mechanism as proposed by Tiarks et al. in direct miniemulsion [ Tiarks F. Landfester K. Antonietti M. Tiarks F. Landfester K. Antonietti M. Langmuir200117908918]. The particle size distribution was narrowed by increasing the weight content of CoTFB, MBA, and water. The particle size of the nanocapsules could be conveniently tuned by varying the weight content of CoTFB and MBA. The as-prepared PNIPAM nanocapsules showed reversible thermosensitive properties. An ordered monolayer of PNIPAM nanocapsules could form by controlling the evaporation of apolar solvent, and moreover the size and thus interparticle distance of PNIPAM nanocapsules in the ordered arrays could be tuned by drying the sample under different temperatures below and above the lower critical solution temperature (LCST) of PNIPAM.

Small but Smart: Sensitive Microgel Capsules

“…[3,12] Whereas sub-micrometer-scale capsules are attractive for delivery and controlled release applications that rely on cellular uptake, [13] larger microgel capsules are attractive for the opposite purpose of encapsulation of cells within the microgel. [9] Established experimental techniques to fabricate sub-micrometer-scale microgel capsules include precipitation polymerization, [14][15][16][17][18][19] emulsion and miniemulsion templating, [20][21][22][23][24] and template-supported layerby-layer assembly [25][26][27][28][29][30][31][32][33] as well as grafting. [34][35][36][37] The fabrication of larger microgel capsules, however, is challenging.…”

Development and characterization of emulsions containing purple rice bran and brown rice oils

“…Emulsion II PRBO and Emulsion II BRBO had significantly ( p < .05) lower droplet sizes compared to Emulsion I PRBO or Emulsion I BRBO, which indicated that the 10 min of shearing effectively decreased the emulsion droplet sizes. The polydispersity index (PdI) is a dimensionless number that describes the heterogeneity of the sample, and it can range from 0 (monodisperse) to 1 (very polydisperse) (Cao, Ziener, & Landfester, ). Emulsion II PRBO and Emulsion II BRBO exhibited more monodisperse characteristics (Figure ) than Emulsion I PRBO and Emulsion I BRBO.…”

Crosslinked polymer nanocapsules

“…Several groups further developed this approach by introducing crosslinker in the miniemulsion systems to endow the PNCs with crosslinked structures . In addition to normal oil‐in‐water miniemulsions, inverse water‐in‐oil miniemulsion have also been used for the preparation of CPNCs using this approach …”