Surface pressure-induced isothermal 2D- to 3D-transitions in Langmuir films of poly(Epsilon-caprolactone)s and oligo(Epsilon-caprolactone) based polyesterurethanes

Abstract

Surface pressure-induced isothermal 2D- to 3D-transitions in Langmuir films of biodegradable poly(ε-caprolactone) (PCL) and oligo(ε-caprolactone) based polyester-urethanes P(OCL-U)s are investigated in order to gain deeper insights into the influence of the linker species on the crystallization and aggregation behavior of macromolecules in a biomimetic aqueous environment. The presence of three urethane linkers derived from 2, 2 (4), 4-trimethyl-hexamethylene-diisocyanate (TMDI), hexamethylene diisocyanate (HDI) and lysine ethylester diisocyanate (LDI) induces remarkable changes in the mesoscopic structure compared to PCL Langmuir films. The pronounced changes in the morphology of the 3D structures co-existing with the Langmuir film above a collapse surface pressure are visualized by Brewster angle microscopy (BAM). Hysteresis of the compression–expansion isotherm in the surface pressure range of the 2D- to 3D-transition indicates the influence of the urethane linkers on the diffusion-limited kinetics and on the reversibility of this phase transition.