Synthesis and characterization of poly(lactic acid) and glucosamine-formaldehyde/dodecylbenzenesulfonate composite films

The composite films of poly(lactic acid) (PLA) doped with glucosamine(Gluc)-formaldehyde(FA) polymer/sodium dodecylbenzenesulfonate (SDBS) complexes at 1–5 wt% were synthesized to demonstrate striking improvement of their structural and mechanical properties. The polymer complexes were obtained by the hydrothermal polymerization of Gluc and FA at a molar ratio of 1:2 in the presence of SDBS. The atomic ratios of S in \( - {\text{SO}}^{ - }_{3} \) to N in \( - {\text{NH}}^{ - }_{3} \) (=S/N) in the polymer complexes limitedly range from 0.52 to 0.69, indicating that the complexation develops through the nonstoichiometric reaction between \( - {\text{NH}}^{{\text{ + }}}_{{\text{3}}} \) groups of (Gluc-FA) polymer and \( - {\text{SO}}^{ - }_{3} \) ones of SDBS and 31–48% of the \( - {\text{NH}}^{ + }_{3} \) groups remain unbound. The PLA composite film doped with 1 wt% (Gluc-FA)/SDBS showed the elongation-at-break of as large as 194% compared with 37% for PLA film, together with an appreciable increase of the crystallites size (D 200) of PLA from 21.8 to 33.3 nm.