Cationic polymer nanoparticles

An organic resin particle comprising a first resin having at least:

• (i) a repeating unit selected from the group consisting of a vinyl amine and an allyl amine;
• (ii) an oxalyl amide crosslinking unit —NHCOCONH—, wherein the dashed lines represent the covalent bond to the polymer residue of the first resin;
• and (iii) a repeating unit according to Formula I or Formula II:
• wherein
• X represents O or NH;
• n represents 0 or 1;
• and
• R1 is selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, and an aryl or heteroaryl group, with the proviso that R1 contains at least six carbon atoms, or
• wherein
• Y represents O or NH;
• n represents 0 or 1;
• and
• R2 is selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, and an aryl or heteroaryl group, with the proviso that R2 contains at least six carbon atoms.