Composition-Encoded Control of Amphiphilicity and Nanoscale Rigidity in Poly(isobutyl cyanoacrylate)/Poly(butylene oxide)- <i>stat</i> -polyglycidol Nanospheres and Nanoellipsoids

Tuning the interfacial hydrophobicity and morphology of polymeric nanomaterials remains a central challenge for controlling their structural, mechanical, and biological properties. Here, we introduce poly(isobutyl cyanoacrylate)/(poly(butylene oxide)-stat-polyglycidol) (PIBCA/(PBO-stat-PG)) nanospheres (NSs) and nanoellipsoids (NEs) as a chemically defined platform for decoupling hydrophobic balance, internal architecture, and morphology within a single system. Statistical copolymers with variable butylene oxide (BO) and glycidol (G) content provide precise modulation of amphiphilicity while maintaining water solubility and stability under in situ polymerization conditions. Across the BO:G gradient, multimodal analyses (TEM, cryo-TEM, DLS, AFM, SAXS, SLS, and ITC) reveal a continuous transition from hydrated, deformable G-rich NSs to compact, lamellar BO-rich structures with reduced hydration and enhanced rigidity. SAXS and AFM jointly establish that BO-induced hydrophobic interactions drive internal densification and structural ordering. Mechanical stretching of embedded NSs yielded NEs with modest aspect ratios (1.6–1.9), compared with previous reports on PIBCA/chitosan NEs. ITC experiments showed a correlation between the aspect ratio and the strength of interaction between PVA and the copolymers. The combined results demonstrate that copolymer architecture alone can encode interfacial structure and mechanical response without altering size or charge. This work establishes PIBCA/(PBO-stat-PG) as a predictive, composition-tunable model for probing how nanoscale amphiphilicity and rigidity govern morphological stability and mechanical behavior in polymeric nanomaterials.