*Article* **Preparation of Nanochitin/Polystyrene Composite Particles by Pickering Emulsion Polymerization Using Scaled-Down Chitin Nanofibers**

**Ryuta Watanabe, Kakeru Izaki, Kazuya Yamamoto and Jun-ichi Kadokawa \***

Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan; k0984020@kadai.jp (R.W.); k3320769@kadai.jp (K.I.); yamamoto@eng.kagoshima-u.ac.jp (K.Y.) **\***Correspondence:kadokawa@eng.kagoshima-u.ac.jp;Tel.:+81-99-285-7743

**Abstract:** In this study, we investigate the Pickering emulsion polymerization of styrene using scaleddown chitin nanofibers (SD-ChNFs) as stabilizers to produce nanochitin/polystyrene composite particles. Prior to emulsion polymerization, an SD-ChNF aqueous dispersion was prepared by disintegrating bundles of the parent ChNFs with an upper hierarchical scale in aqueous acetic acid through ultrasonication. After styrene was added to the resulting dispersions, the mixtures at the desired weight ratios (SD-ChNFs to styrene = 0.1:1–1.4:1) were ultrasonicated to produce Pickering emulsions. Radical polymerization was then conducted in the presence of potassium persulfate as an initiator in the resulting emulsions to fabricate the composite particles. The results show that their average diameters decreased to a minimum of 84 nm as the weight ratios of SD-ChNFs to styrene increased. The IR and 1H-NMR spectra of the composite particle supported the presence of both chitin and polystyrene in the material.

**Keywords:** chitin nanofiber; composite particle; Pickering emulsion polymerization; polystyrene; scaled-down
