Supplementary Information for K.B. Shepard et al. “Patchy Janus particles with
tunable roughness and composition via vapor-assisted deposition of
macromolecules”
Particle materials and synthesis
PS particles were synthesized according to the procedures detailed by Zhang et al.1 Particle sizes
are modified from the above procedure by varying the relative concentrations of the ammonium
persulfate initiator and monomers. Silica nanoparticles were synthesized a classical Stober
technique2 in which 10mL NH3 was mixed well in 10mL water and 74mL ethanol, then 5.6 mL
tetraethyl orthosilicate was added and stirred for 12 hr.
Precursor particle film preparation
Prior to coating, microscope glass slides
were cleaned by heating in piranha acid
(4:1 H2SO4:H2O2,) at 95 ºC for 30 min,
then rinsed and stored in DI water.
Suspensions of PS or silica nanoparticles
(1-9%wt) in a water/methanol solution
(3:1 – 1:1) were immersed in a sonic
bath for 15 minutes prior to film casting.
Precursor particle monolayers were
coated onto the glass slides via a
programmable syringe pump following
the procedure of Prevo and Velev.3 A 50
μm image of a typical silica particle
monolayer is shown in the figure below,
taken with a 3D laser microscope (SI
Figure 1). The bright spots represent
areas where more than a monolayer of
SI Figure 1: Laser microscope image of a Silica
particles has deposited. Even coverage
particle monolayer formed by drag coating.
and large areas (grain size >10μm) of
hexagonally-packed particles was observed. After sonication of either precursor or Janus particle
films, examination of the substrate with the laser microscope showed that nearly all particles
were removed, indicating that particle immobilization is easily reversed by sonication in water.
MAPLE deposition
Amorphous PMMA (~15 kg/mol molecular weight) or semicrystalline PEO (4.6 kg/mol) was
dissolved in chloroform (0.1% by weight). The details of the MAPLE deposition process have
been described in detail in previous papers.4 During deposition, the glass substrate was held at a
constant temperature of 27°C, unless stated otherwise. Though not discussed in the paper, the
size distribution of the polymer nanodroplets could be manipulated by varying the composition
of the MAPLE target solution, as reported in our previous work.4 This provides another method
to systematically tune the surface properties of the Janus particles.
Janus particle post-fabrication annealing study
PMMA/silica patchy Janus particles were fabricated via MAPLE deposition with a substrate
temperature of 27 °C, then underwent 1 hour annealing at 130°C. The morphology is very
different than that of particles fabricated with a substrate temperature of 130°C, in that most of
the polymer now forms polymer bridges between particles, instead of wetted droplets at the
particles’ surfaces.
SI Figure 2: AFM height and phase images of post-annealed PMMA/silica patchy Janus
particles.
References:
(1) Zhang, L.; D’Acunzi, M.; Kappl, M.; Auernhammer, G. K.; Vollmer, D.; van Kats, C. M.;
van Blaaderen, A. Hollow Silica Spheres: Synthesis and Mechanical Properties. Langmuir
2009, 25, 2711–2717.
(2) Stöber, W.; Fink, A.; Bohn, E. Controlled Growth of Monodisperse Silica Spheres in the
Micron Size Range. J. Colloid Interface Sci. 1968, 26, 62–69.
(3) Prevo, B. G.; Velev, O. D. Controlled, Rapid Deposition of Structured Coatings from
Micro- and Nanoparticle Suspensions. Langmuir 2004, 20, 2099–2107.
(4) Shepard, K. B.; Arnold, C. B.; Priestley, R. D. Origins of Nanostructure in Amorphous
Polymer Coatings via Matrix Assisted Pulsed Laser Evaporation. Appl. Phys. Lett. 2013,
103, 123105.