Hevea brasiliensis rubber particles' fluid interfaces reveal size impact on early coagulation steps
Marion Baudoin, Gilles Paboeuf, Siriluck Liengprayoon, Natedao Musigamart, Céline Bottier, Véronique Vié
Abstract
Natural rubber originates from the coagulation of rubber particles (RP) from Hevea brasiliensis latex. The size distribution of Hevea RP is bimodal with the presence of small rubber particles (SRP) and large rubber particles (LRP). This study aims at getting a better understanding of the early coagulation steps of Hevea RP taking into account the particle size. SRP and LRP were obtained by centrifugation of freshly tapped ammonia-free latex from RRIM600 clone. Size and zeta potential measurements showed that both RP fractions were efficiently separated and stable in basic buffer. SRP and LRP dispersions were placed in a Langmuir trough and RP were let to adsorb at the air-liquid interface to form interfacial films. Surface tension and ellipsometry indicate that the formation kinetics and the stabilization of the film at the air-liquid interface are faster for SRP than LRP. Moreover, the arrangement of RP at the interface differs between SRP and LRP, as shown by Brewster angle microscopy, atomic force microscopy and confocal laser scanning microscopy. First, the RP membrane and cis -1,4-polyisoprene core spread at the air-liquid interface before clustering. Then, while the SRP fuse, the LRP keep their structure in individual particles in floating aggregate. The role of the non-isoprene molecules on the different organization of SRP and LRP films is discussed, the one of the two major RP proteins, SRPP1 (Small Rubber Particle Protein) and Rubber Elongation Factor (REF1) in the early coagulation steps. • Formation kinetics and stabilization of fluid films are faster for SRP than LRP. • Rubber particle size influences the film organization at BAM and AFM scales. • LRP membrane is partially destabilized in fluid film but LRP topology is preserved. • Interface air/liquid destructures SRP and promotes first step of coagulation. • CLSM highlights the repartition of lipids of the rubber particle membrane.