## 4 Conclusions  
It was shown that St/AA submicroapsules can be obtained by miniemulsion copolymerization of AA and St with lipophilic core materials. There was an optimum condition for obtaining electronically stable St/AA submicrocapsules in the aqueous phase.  
With the increase of [AA], the mean particle size and zeta potential of St/AA submicrocapsules were greatly decreased due to anionic AA and polyacrylic blocks in micelles and submicrocapsules, respectively. However, at over [AA]/[St] = 0.33, the mean particle size of St/AA submicrocapsules was increased, which was ascribed to the particle agglomeration in the aqueous phase due to the increased hydrophilic swollen layer of the particles and the resulting reduction in surface area and zeta potential. The increase in the applied amount of surfactant assures the reduction in size of micelles and resulting St/AA submicrocapsules. At higher [SDS] of over 1.0 \(\times\) 10\({}^{-3}\) mol, however, the formation of the weakened swollen layer, causing particle aggregation and a decrease in zeta potential, was suspected. Mean particle size and zeta potential of St/AA submicrocapsules were at the optimum condition at an initiator concentration of 2.0 \(\times\) 10\({}^{-3}\) mol/mol of monomer. Droplet nucleation was not effectively activated at a lower initiator concentration. At a higher initiator concentration, particle aggregation was manifested by virtue of the reduction in the portion of polyacrylic blocks in the swollen layer around the submicrocapsules.  
From the above consideration, the optimum condition for miniemulsion copolymerization of St and AA was determined as follows; [AA]/[St] = 0.33, [SDS] = 1.0 \(\times\) 10\({}^{-3}\) mol, and [AIBN] = 2.0 \(\times\) 10\({}^{-3}\) mol/mol of monomer. Long-term colloidal stability was also evaluated for  
Figure 6: Transmission and backscattering profiles of St/AA submicrocapsule aqueous dispersion. (Prepared at the optimum miniemulsion condition of [AA]/[St] = 0.33, [SDS] = 1.0 \(\times\) 10\({}^{-3}\) mol, [AIBN] = 2.0 \(\times\) 10\({}^{-3}\) mol/mol of monomer).  
the optimum condition of St/AA submicrocapsules by measuring the optical transmission and the photon backscattering profiles of the aqueous dispersion. It is shown that backscattering was the prevalent signal and there were almost no variations in backscattering intensity, which means that St/AA submicrocapsules prepared at the optimum condition have superior colloidal stability without aggregation and sedimentation. These electrically stable St/AA submicrocapsules can be applied to various fields such as a targeted and/or sustained release drug delivery system, emulsion templating of 3D objects, additives for polymeric resins, highly dispersive fiber finishing agent, and so on.  
This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and the National Research Foundation of Korea (Grant No. 2015H1C1A1035576). This material was also based upon work supported by the Ministry of Trade, Industry & Energy (MOTIE, Korea) under Industrial Technology Innovation Program (Grant No. 10048877).  
[PERSON] conceived and designed the experiments; [PERSON] performed the experiments; [PERSON] and [PERSON] analyzed the data and wrote the paper.  
The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.