Cationic styrene-butyl acrylate-quaternary ammonium copolymer nanospheres for surface modification of cotton fibers

Cationic copolymer nanospheres are important functional materials, for example, for fiber modification. Here, emulsifier-free ternary emulsion copolymerizations of styrene (St) and butyl acrylate (BA) with two different quaternary ammonium cationic monomers (QACMs), methacryloxyethyl trimethyl ammonium chloride (DMC) and trimethyl (vinylbenzyl) ammonium chloride (VBT), and 2,2’-azobis[2-methylpropionamidine] dihydrochloride (AIBA) as an initiator were conducted at 80 ×C, under agitation at 300 rpm. The differences between the two cationic comonomers strongly influenced the monomer conversion, diameter, morphology, and surface charge density of the nanospheres. In particular, a higher cationic comonomer content is found to produce more oligomer radicals and thus more primary particles in the polymerization process, which leads to higher monomer conversion, smaller particle diameter, and increased surface charge density. The cationic nanospheres could be adsorbed in either a monolayer or in multiple layers on the oppositely charged cotton fiber because of their fierce electrostatic attraction. Compared with poly(St-BA-VBT) nanospheres, the distribution of poly(St-BA-DMC) nanospheres was more nonuniform on fiber surfaces accompanied by agglomerates.