Enhancing Thermal Stability of One-Dimensional Poly(ethylene oxide) Nanocrystals via Matrix Chemical Crosslinking

Abstract

One-dimensional (1D) polymer nanocrystals have attracted interest due to the exceptional properties imparted to host matrices. A proven protocol exists for developing a dispersion of 1D poly(ethylene oxide) (PEO) nanocrystals in a polystyrene (PS) matrix from PS-b-PEO self-assembly during styrene (St) photopolymerization. However, the 1D nanocrystals remain stable only below the Tg of the PS matrix. Above Tg, the matrix softens, and the molten PEO transforms into nanospheres due to Plateau-Rayleigh instability.In this study, we stabilized the nanostructures through crosslinking, replacing St with divinylbenzene (DVB). The original protocol, which began with a homogeneous solution of PS-b-PEO in St, led to macrophase separation of PS-b-PEO instead of 1D nanocrystals. Based on the PEO/St phase diagram, we tried a different approach, where PS-b-PEO nanostructures self-assembled in a gelled solution before photocuring. This resulted in a dispersion of 1D nanostructures and shorter micelles in a DVB-crosslinked matrix. When heated beyond Tg, the morphology remained stable, confirming the effectiveness of crosslinking in preserving the 1D nanostructure.