Crystallization and phase segregation of multifunctional multiblock copolymers in spin coated thin films altered by diurethane junction units

A multiblock copolymer named PDC is composed of crystallizable oligo(p-dioxanone) (OPDO) and oligo(ε-caprolactone) (OCL) as hard and switching segments. PDC has been synthesized via connecting two oligomeric macrodiols using a diisocyanate linker such as 2,2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) or 1,6-hexamethylene diisocyanate (HDI). In this work, the surface morphologies of spin coated thin films from two PDCs (PDC-HDI and PDC-TMDI) were investigated via in-situ atomic force microscopy (AFM) to examine how the diisocyanate linkers affect the balance between crystallization and phase segregation behavior. The results demonstrated that in PDC-HDI, the crystallization of poly(ε-caprolactone) (PCL) crystals provoked a "break out" from the phase segregated morphology. On contrary, the crystallization of PCL crystals in PDC-TMDI was strictly confined in the phase segregated morphology.