In order to prepare polymer nanoparticles you have to blend your polymer with oppositlly charged material, which could be another polymer or cation like Ca or Ag. For example poly acrylic acid (MWt thousands) chain could be collapsed to nanoparticles beads via its interaction with other basic polymer like Poly acrylamide (same Mwt) or by dropping CaCl2, its charge nutralization principle be aware of pH, ionic strength and concentration, you can investigate particle size via DLS

The change of solvent plus following fractionation (via centrifuge) might work well.

You find a procedure within the publication. Thereby you can skip the amine and modify the EMA (cross linking) and the VBS (charge).

Article Functionalized polymer colloids bearing primary amino groups

The most common way of making polymer nanoparticles is by emulsion polymerization. There are several research groups specialized in emulsion polymerization, e.g., Emulsion Polymer Institute at Lehigh University. Dow Chemicals (especially Rohm & Haas) and BASF have many commercial acrylic emulsion polymer products with particle sizes at 100 nm or below. Since early 1990s, most of commercial emulsion polymerization uses "seeded" recipes. The particle sizes of these acrylic seeds are in the range of 20-30 nm.

Dear colleagues, thank you very much for your answers.

All the ways recommended belong to "wet" chemistry. Really I wonder about plasma chemistry possibilities: Is it possible to prepare polymer (acrylics) nanoparticles with sizes between 30 and 100 nm by plasma (gas phase) chemistry processes?

We have developed a method to prepare acrylic polymer nanoparticles with 10 nm in mean diameter. Please see:

H. Saade et al, J. Biomat. Sci. Polym. Ed. DOI: 10.1080/09205063.2016.1184120; http://dx.doi.org/10.1080/09205063.2016.1184120