Long PEO-based nanoribbons generated in a polystyrene matrix through reaction-induced microphase separation followed by a fast crystallization process

GUTIÉRREZ GONZÁLEZ, JESSICA; FERNÁNDEZ LEYES, MARCOS D.; RITACCO, HERNÁN A.; SCHROEDER, WALTER F.; ZUCCHI, ILEANA A.

SOFT MATTER

ROYAL SOC CHEMISTRY

Año: 2021 vol. 17 p. 2279 - 2289

1744-683X

The dispersion of elongated nanostructures with a high aspect ratio in polymer matrices has been reported to provide the material with valuable properties such as mechanical strength, barrier effect and shape memory, among others. In this study, we show the procedure to achieve a distribution of elongated crystalline nanodomains in a PS matrix employing the self-assembly of block copolymers (BCP). The selected BCP was Polystyrene-block-Polyethylene oxide (PS-b-PEO). It was dissolved at 10 wt% in styrene (St) monomer and the blend was slowly photopolymerized during 4 days at room temperature. This blend was initially homogeneous and nanostructuration took place at an early stage of the polymerization due to the microphase separation of PEO blocks. This led to primary micelles with PEO core stabilized by PS arms. Due to its high tendency to crystallize, demixed PEO blocks crystallized immediately inducing the growing of the primary micelles into elongated nanostructures from the beginning of the polymerization. Thus, the time window between the onset of crystallization and the vitrification of the matrix was almost four days allowing all micelles to have the opportunity to couple to a growing nanostructure. As a result, a population of nanoribbons with average lengths surpassing the 10 μm dispersed in a PS matrix was obtained. It was demonstrated that these ribbon-like nanostructures are preserved as long as the heating temperature is located below Tg of the matrix. If the material is heated above this temperature, softening of the matrix allows the breakup of the molten PEO nanoribbons due to Plateau-Rayleigh instability.