Cationic polyelectrolyte-assisted synthesis of silica nanochains for enhancing mechanical properties of sodium alginate composite films

Abstract

For the improvement of the transparency of silica nanomaterials and their dispersibility in polymer films, a series of silica nanochains were synthesized via a simple and cost-effective self-assembly method. Herein, silica oligomers were prepared through chemical hydrolysis-condensation reactions of tetramethyl orthosilicate; the growth of negative-charged silica oligomers in the confinement of positive-charged poly(dimethyldiallylammonium chloride) (PDDA) led to the formation of silica nanochains. By tuning the synthesis parameters (i.e., PDDA concentration, reaction temperatures, water:ethanol volume ratios, and ammonium water contents), it is possible to control the structure of silica nanochains and subsequently mechanical properties of sodium alginate (SA) composite films. Using optimal synthesis parameters, the obtained silica nanochains exhibited exceptional performances with high transparency, excellent hydrophilicity and good dispersibility, which surpassed silica nanospheres. Compared with pure SA film, the tensile strength and storage modulus in the glassy region of the SA composite film containing 0.5 wt% silica nanochains was improved by 93.0% and 824.7%, respectively. The work demonstrates the great promise of such silica nanochains toward practical application in optoelectronic thin-film materials.