Effects of n-hexadecane on sphericity of poly-α-methylstyrene shells

Abstract Millimeter-scale polymer shells with stringent specifications such as sphericity, wall thickness uniformity and surface finish are needed in inertial confinement fusion (ICF) experiment. In order to meet these stringent specifications, n -hexadecane (n-HD) is introduced in oil phase to improve the sphericity of poly-α-methylstyrene (PAMS) shells. The results show that n-HD decreases the survival rate of the final PAMS shells, since coalescence between W1/O/W2 double droplets occurs owing to phase separation during the curing process. However, characterization results show that the addition of n-HD into O phase leads an increasing interfacial tension at O-W2 interface, which is considered as the only driving force for sphericity. Tracking experiment data indicates that the addition of n-HD can effectively extend the curing process. A percolation threshold is determined at about 58% where PAMS large-scale networking occurs and over where the deformation of the droplets is considered irreversible. So the addition of n-HD can extend the period W1/O/W2 droplets stay in liquid with nice fluidity, where the interfacial tension can work sufficiently and thus improving the final sphericity of polymer shells. Furthermore, when the mass fraction of n-HD is larger than 2.0%, porous PAMS shells can be obtained.