Side selective surface modification of chitin nanofibers on anionically modified cotton fabrics

• Side selective grafting of chitin nanofibers was carried out on anionically modified cotton fabrics.
• Chitin nanofibers were prepared using crab shells using ultrasonication method.
• Cotton fabrics were modified with partial carboxymethylation of cotton to impart anionic character to the cotton.
• Side selective grafting has been carried out using a method similar to dyeing using special apparatus.

Chitin nanofibers have been prepared from crab shell as a chitin source using ultrasound assisted fibrillation. Atomic force microscopy (AFM) study showed that the prepared nanofibers were having diameters and lengths primarily in the range of 2–20 nm and 0.3–4 μm respectively. These nanofibers were selectively grafted on one side of a 100% cotton fabric using a special apparatus. Prior to the grafting, cotton fabrics were modified with partial carboxymethylation to encourage cotton fiber nanofiber interactions. The surface modification was confirmed by Fourier transform infrared spectroscopy (FT-IR) peaks at 1594 cm−1 and 1735 cm−1 due to the presence of carboxylic acid functionality in modified cotton fabrics. Scanning electron microscope (SEM) study of the nanofiber grafted cotton fabrics showed that nanofibers were adhered to the cotton fabrics. Elemental analysis confirmed that side selective grafting of nanofiber has taken place due to the peak at 0.394 keV which attributes to the presence of nitrogen element in chitin nanofibers. This peak was absent in the other side of the fabric which was not coated with chitin nanofibers. Amount of adhered nanofibers was seen to increase with the increase of nanofiber concentration used in grafting as confirmed by Kjeldahl analysis. A possible mechanism of cotton fiber–nanofiber interactions is introduced.