Tri-Phasic Size- and Janus Balance-Tunable Colloidal
Nanoparticles (JNPs)
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Abstract
These
studies show synthesis of triphasic size- and Janus balance
(JB)-tunable nanoparticles (JNPs) utilizing a two-step emulsion polymerization
of pentafluorostyrene (PFS) and 2-(dimethylamino)ethyl methacrylate
(DMAEMA) and <i>n</i>-butyl acrylate (nBA) in the presence
of poly(methyl methacrylate (MMA)/nBA) nanoparticle seeds. Each JNP
consists of three phase-separated copolymers: p(MMA/nBA) core, temperature,
and pH-responsive (p(DMAEMA/nBA)) phase capable of reversible size
and shape changes, and shape-adoptable (p(PFS/nBA)) phase. Due to
built-in second-order lower critical solution temperature (II-LCST)
transition of p(DMAEMA/nBA) copolymer, macromolecular segments collapse
when temperature increases from 30 to 45 °C, resulting in size
and shape changes. The p(DMAEMA/nBA) and p(MMA/nBA) phases within
each JNP assume concave, flat, or convex shapes, forcing p(PFS/nBA)
phase to adopt convex, planar, or concave interfacial curvatures,
respectively. As a result, the JB can be tuned from 3.78 to 0.72.
The presence of pH-responsive DMAEMA component also facilitates the
size and JB changes due to protonation of the tertiary amine groups
of p(DMAEMA/nBA) backbone. Synthesized in this manner, JNPs are capable
of stabilizing oil droplets in water at high pH to form Pickering
emulsions, which at lower pH values release oil phase. This process
is reversible and can be repeated many times
