Metal-based composite microcapsule shells: development of new synthesis methods and characterisation of transport properties

In this study platinum nanoparticles (Pt-NPs) and silica/platinum composite (Si/Pt)
stabilised oil-in-water emulsions (low molecular weight oil core) have been
investigated for the reduction, catalytic activity and deposition of a secondary metal
film via electroless plating, resulting in gold coated emulsion droplets. Colloidal silica
stabilised emulsion droplets have been coated in poly(dopamine) (PDA) resulting in
core-shell microcapsules where the shell is a binary mixture of polymer and particles.
Subsequently the PDA microcapsule surface has been used for the deposition of a
silver shell on the surface via electroless plating of silver ions initially adsorbed to the
PDA microcapsule shells.
The microcapsules have been tested for active core retention and shell permeability,
by introducing the microcapsules to a continuous phase of ethanol/water (volume ratio
4:1) in which the active core is completely soluble and measuring the core release by
utilising gas chromatography. The gold coated emulsion droplets (Pt-NPs and Si/Pt)
completely retained the active core for over 30 days at 40oC, demonstrating the
retention of the core and permeability of the gold shell. The silver coated PDA
microcapsules released most of the core after 1 hour due to the in-sufficient coverage
of the PDA surface with silver.
The microcapsules were also tested for encapsulating phase change materials (PCM)
resulting in MicroEncapsulated PCM (MEPCMs). The MEPCMs were tested for
thermal energy storage and release for home comfort. Analysis on the MEPCMs
properties such as supercooling, encapsulation efficiency and thermal conductivity
was also carried out. Gold coated emulsion droplet (Pt-NPs and Si/Pt), demonstrated
good encapsulation efficiencies and ratios, which demonstrated the good ability of the
iv
MEPCMs to store and release thermal heat. The gold coated emulsion droplets also
demonstrated reduced supercooling and enhanced thermal conductivity.