Polymeric surfactants synthesised from palm-based oleic acid as potential biocompatible agents in natural rubber latex compounding

Abstract

This research aimed to design biocompatible polymeric surfactants as additives to natural rubber latex (NRL) and the mechanical properties of the latex films were evaluated thereafter. Both anionic and non-ionic surfactants, APS and NPS, were successfully synthesised from palm-based oleic acid by polyesterification, with their ester linkages verified by FTIR analysis. Both surfactants possess good thermal stability with thermal decomposition temperatures above 200 °C. They were biocompatible and non-cytotoxic, as evidenced by high cell viability > 80% for all tested cell lines. In general, the antibacterial activities of both surfactants were stronger against Gram-positive bacteria than Gram-negative bacteria. Surfactant solutions were prepared and compounded into NR latex to produce latex films. Both solutions exhibited good wetting properties with contact angles < 90°, low critical micelle concentration values ranging from 0.005 to 0.007 mol/L, low foaming ability, and reasonable foam stability above 80%. The unaged NR films compounded with APS demonstrated greater mechanical strengths than the control and NPS, recording the highest tensile strength of 28.65 MPa and the lowest modulus (M300) reflecting softness. Both latex films showed a slight reduction in mechanical properties after ageing. These results indicated that APS had a higher potential to modify NR latex film properties, in particular film softness. The surfactants also presented high potential as non-cytotoxic antimicrobial agents in NR compounding.