Morphologies of Various Polycaprolactone/Polymer Blends in Ultrathin Films

Abstract

Morphologies of ultrathin films of nine poly(ε-caprolactone)/polymer miscible and immiscible binary blends have been investigated under isothermal crystallization conditions by real time atomic force microscopy, optical microscopy, and electron diffraction techniques. It was found that the truncated lozenge-shape morphology of the pure poly(ε-caprolactone) (PCL) crystals is modified in miscible blends, forming regular or inverted S- or C-shaped crystals, the curvature depending on the nature of the second polymer and increasing with blend composition. Moreover, the growth rate decreases with the addition of the second polymer following the same order as the crystal curvature: PVC > CPE(48%) > SAN(25%) > PC > SAN(9.5%) > PVME. In contrast, for immiscible blends, no significant changes in kinetics and morphology were observed since a constant crystal growth rate and the same truncated lozenge-shape morphology as pure PCL crystals are obtained at all compositions. Kinetic and morphological changes in miscible blends are discussed in terms of PCL/polymer intermolecular interactions since the growth rate decreases and the curvature increases with the addition of polymers of increasing interactions.

Impact of Molecular Weight on the Thermal Stability and the Miscibility of Poly(ε-caprolactone)/Polystyrene Binary Blends

“…The changing of the induction time in the nucleation process results in different onset temperature for the crystallization indicating the dilution of the compatible components at the molecular level. A similar trend for compatibility of polymer blends was found using melting point depression method [21,24]. On the other hand, for PCL/PS(650K) blends, the onset temperature of crystallization does not influence with PS(650K) incorporation in the blends.…”

“…Previously, we have reported morphologies of various PCL/polymer blends in ultrathin films [20,21]. The crystallization kinetics was explained from glassy and molten states.…”

Advance application of Raman spectroscopy for quantitative analysis of noncrystalline components in thin films of poly(ε‐caprolactone)/poly(butadiene) blends

“…The overgrowths have the same orientation to the basal plane but sometimes they are not fully developed due to the lack of available melts. We have reported earlier [ 13,18 ] that for miscible blends of PCL/polyvinyl chloride (PVC), during the crystal growing process the exclusion of noncrystallizable PVC and amorphous PCL creates a local compositional field gradients in the melt near the growth front. That compositional field reduces the growth velocity turn into tip splitting phenomena, protrusion of crystal into the melt, and anisotropy of surface free energy in the growth face.…”

“…The bending of the curvature increases with lowering the crystallization temperature. [18] However, the crystal morphology and growths are explained in details for miscible and immiscible blends, but the location and quantity of the amorphous component are still unknown. To the best of our knowledge, this is the first attempt to identify the locations and quantify the amorphous poly(butadiene) (PB) polymer in the PCL/PB blend system by Raman spectroscopy.…”

“…Additionally, the melting point might be effected by the crystal lamellae thickness of the components of the blends, the crystal perfection and the physical nature of the components where one component might be surrounded by the other component of the blends. In our previous studies, [ 13,18 ] we have reported several miscible and immiscible; polymer/polymer binary blends of crystalline/crystalline and crystalline/amorphous components. The ultrathin films (10‐120 nm) of PCL/amorphous components were made from solution, isothermally crystallized at a certain temperature from melt.…”