Hierarchical Structures in Thin Films of Miktoarm Star Polymers: Poly(n-hexyl isocyanate)(12K)–Poly(ε-caprolactone)1–3(5K)

A series of miktoarm star polymers, [poly(n-hexyl isocyanate)(12K)]–[poly(e-caprolactone)1–3(5K)] (PHIC–PCL1–3) (composed of a rigid self-assembling PHIC arm and one to three flexible crystallizable PCL arms), were investigated to examine the polymers’ thermal properties and nanoscale thin film morphologies. The miktoarm polymers were stable up to 180 °C. The PHIC and PCL arm components underwent phase separation during the solution casting, drying, and post toluene-annealing processes, forming interesting but very complex thin film morphologies. The resulting thin film morphologies were examined in detail for the first time using synchrotron grazing incidence X-ray scattering (GIXS) measurements and quantitative data analysis. All of the miktoarm star polymer films formed vertically well-oriented lamellar structures, regardless of the number and length of PCL arms. These structures were quite different from the cylindrical structures commonly observed in conventional flexible diblock copolymer films havi...