## 4 Conclusions  
The purpose of this work was an investigation of the preparation of PMMA, PMMA-_co_-EGDMA, PS and PS-_co_-DVB NPs copolymerized with the _p_-(11-acrylamide)undecanoyloxyphenyl dimethylsulfonium methyl sulfate (AUPDS) surfmer molecule via miniEP technique. The AUPDS surfmer was successfully synthesized and presented a high yield through a modified synthesis approach. The copolymerization of St or MMA with surfmer feed concentration of 2-4 mol\(\%\) of surfmer yielded monodisperse and stable particles. Average hydrodynamic diameters, PI and ZP for the obtained particles were 127 nm, 0.05 and 42 mV for PMMA-_co_-AUPDS particles and 109 nm, 0.14 and 34 mV for PS-_co_-AUPDS particles when using 2 mol\(\%\) AUPDS. For cross-linked particles, the results indicated that up to 10 mol\(\%\) cross-linker yielded particles with low PI, with a slight increase in size. While maintaining the same AUPDS concentration ratios, increasing the cross-linker amounts also led to a decrease in the ZP of the obtained NPs, probably due to internalization of the AUPDS during polymerization. PMMA-_co_-EGDMA-_co_-AUPDS showed on average a hydrodynamic diameter of 166 nm, PI of 0.09 and ZP of 41 mV, whereas for PS-_co_-DVB-_co_-AUPDS the average was 148 nm, 0.04 and 29 mV. The presence of the surfmer on the NP surface was confirmed via ZP measurements and polyelectrolyte titration before (positive charge) and after a basic hydrolysis process (negative charge).  
In conclusion, using the optimized parameters functionalized NPs were produced in one step using the AUPDS surfmer. Furthermore, the active ester groups should allow to couple a wide range of amine-containing biomolecules to the particles which will be explored in future studies.  
The following are available online at [[http://www.mdpi.com/2073-4360/10/4/408/s1](http://www.mdpi.com/2073-4360/10/4/408/s1)]([http://www.mdpi.com/2073-4360/10/4/408/s1](http://www.mdpi.com/2073-4360/10/4/408/s1)).  
**Figure S1.**\({}^{1}\)H-NMR spectrum of AUPDS surfmer; **Figure S2.** ATR-FTIR spectrum of AUPDS surfmer; **Table S1.** Example of reagent amounts for the preparation of particles via mini-emulsion polymerization using the AUPDS surfmer. **Table S2.** Z-average, PI and ZP values obtained for different particle syntheses using AUPDS 2 mol% and cross-linker (if present) at 10 mol%. **Table S3.** Z-average, PI and ZP values obtained for AUPDS-functionalized particles under different storage conditions.  
[PERSON] gratefully acknowledges a PhD scholarship provided by the CAPES Foundation (Ministry of Education, Brazil, grant number BEX 13441-13-2) The authors thank [PERSON] (Fraunhofer IGB) for the SEM images and [PERSON] for the help with the particle charge detector measurements. This research did not receive any further specific grant from funding agencies in the public, commercial, or not-for-profit sectors.  
[PERSON] performed the experiments and drafted the manuscript; [PERSON] and [PERSON] assisted with the design of the experiments and data analysis; [PERSON] contributed with the concept of the work and with discussions; [PERSON] directed the research work and assisted with data analysis and discussions. All authors contributed to the revision of the manuscript.  
The authors declare no conflict of interest.