*Article* **Crystallization of Poly(ethylene oxide)-Based Triblock Copolymers in Films Swollen-Rich in Solvent Vapors**

**Iulia Babutan 1,2, Otto Todor-Boer 3, Leonard Ionut Atanase 4,5, Adriana Vulpoi <sup>1</sup> and Ioan Botiz 1,2,\***


**Abstract:** In this study, we employed a polymer processing method based on solvent vapor annealing in a confined environment to swell-rich thin films of polybutadiene-*b*-poly(2-vinylpyridine)-*b*poly(ethylene oxide) triblock copolymers and to promote their crystallization. As revealed by optical and atomic force microscopy, thin films of triblock copolymers containing a rather short crystalline poly(ethylene oxide) block that was massively obstructed by the other two blocks were unable to crystallize following the spin-casting process, and their further swelling in solvent vapors was necessary in order to produce polymeric crystals displaying a dendritic morphology. In comparison, thin films of triblock copolymers containing a much longer poly(ethylene oxide) block that was less obstructed by the other two blocks were shown to crystallize into dendritic structures right after the spin-casting procedure, as well as upon rich swelling in solvent vapors.

**Keywords:** block copolymers; thin films; solvent vapor annealing; polymer crystallization; atomic force microscopy
