The influence of the substitution degree and length of alkyl chains on the sizing properties of alkylation starches

In this work, a series of alkylation starches (St-Cn) with different alkylation degrees was synthesized by introducing alkyl chains (the number of carbon atoms was 3, 8, and 12, respectively) onto starch. The influence of the substitution degree (DS) and length of the alkyl chains on the sizing properties of alkylation starches was studied. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectra provided evidence for the linkage of alkyl chains onto the starch structure. Benefiting from the flexibility characteristic of the alkyl chain and the weakening hydrogen bonding to starch structure, St-C8 alkylation starch film with a DS of 0.114 exhibited a high elongation break of 4.64%, which is higher than that of the modified starches reported in most of the literature. Moreover, the alkyl chain could reduce the internal stress of the starch adhesive layer among fibers, which improved the adhesion of alkylation starch to cotton fibers. The St-C12 alkylation starch obtained by the longer alkyl chain weakened the adhesion among fibers due to the strong hydrophobic effect. This work provides a new idea to achieve starch plasticization.