Protective behavior of natural rubber latex induced by nickel tetrasulfonated phthalocyanine interactions

Natural rubber latex (NRL), a sustainable biopolymer derived from Hevea brasiliensis , is a renewable colloidal system whose functional properties depend on particle deformation and coalescence during film formation. In this study, nickel tetrasulfonated phthalocyanine (NiTsPc) was investigated as an interfacial molecular modifier capable of altering interparticle interactions and modulating the colloidal behavior of NRL. The dispersions were characterized by dynamic light scattering (DLS), zeta potential measurements, nanoparticle tracking analysis (NTA), and UV–Vis absorption spectroscopy. DLS and NTA results indicated the interaction of NiTsPc onto the protein-phospholipid interfacial layer of the rubber particles, leading to an increase in hydrodynamic diameter while maintaining a highly negative zeta potential (−36.0 to −33.7 mV), indicative of preserved colloidal stability. UV–Vis spectroscopy showed that NiTsPc retained its characteristic aggregation profile within the latex matrix. Morphological analyses of Layer-by-Layer (LbL) films by SEM and AFM revealed that NiTsPc reduced particle coalescence during bilayer drying. This behavior was also reinforced by the increased surface roughness (RMS = 562 nm) compared with pure NRL films (243 nm). The results demonstrate that NiTsPc acts as an interfacial stabilizing agent, providing a protective effect that enables microstructural control for coatings, membranes, and assembly film formation.