Interfacial self-assembly influence of the aliphatic region in elastin-like polypeptides-based amphiphiles

Amphiphiles based on elastin-like polypeptides (ELPs) offer a versatile platform for the design of nanostructured assemblies. However, the specific role of the hydrophobic tail architecture in governing the layer formation, assembly, and behavior remains largely unexplored. In this study, we compare the interfacial properties of two tailored ELP amphiphiles, ELP80-g-squalene (ELP80-g-SQ) and ELP80-g-dodecyl (ELP80-g-C₁₂), which share an identical ELP backbone but differ in their hydrophobic substitution. Langmuir isotherms and Brewster angle microscopy were utilized to confirm the emergence of compact multilayer domains in ELP80-g-SQcontrasting with the homogeneous and fluid morphology of ELP80-g-C₁₂. UV-vis reflection spectroscopy, ellipsometry, and contact angle studies align with the notion that these bio-based polymers readily scale up to bilayer and multilayer structures, while exhibiting divergent water retention properties. Squalene-based films are characterized by surface hydration and, consequently, a hydrophilic surface with the ELP exposed. This organization is instrumental in the promotion of water reduction through the process of evaporation. However, for ELP80-g-C₁₂, the exposure of the dodecyl chains during layer transfer results in the promotion of a hydrophobic surface. Furthermore, their surface coverage facilitates enhanced water retention within the system. These findings suggest that, in the presence of bulky hydrophilic moieties, such as ELPs, trans-unsaturated chain interdigitation can promote the formation of rigid, multilayered architectures, in contrast to the disordered packing of saturated alkyl tails. The present study establishes a direct correlation between tail chemistry and interfacial packing, thereby providing mechanistic insight into the design of protein-based films for colloidal assemblies, membrane coatings, and biointerfacial engineering.