Interphase Materials by Forced Assembly of Glassy Polymers

Abstract

When two immiscible polymers are brought into intimate contact, highly localized mixing of polymer chains creates an "interphase" region. We have fabricated materials that are entirely interphase by forced assembly of two immiscible polymers. Assemblies of thousands of alternating layers of two polymers, with individual layer thickness on the nanometer size scale of the interphase, were created by layer multiplying coextrusion. The properties of the interphase materials were probed with conventional tools of polymer analysis. In this study, the effect of interaction strength was examined with assemblies that combined an amorphous polyester with a series of styrene-acrylonitrile copolymers that varied in acrylonitrile content from 0 to 30 wt %. Continuous, uniform layers were directly observed using atomic force microscopy. Interphase thickness was extracted from the layer thickness dependence of oxygen permeability. The interphase thickness showed the predicted dependency on the parameter and correlated with interphase strength as measured with the T-peel test. Unexpectedly, volumetric properties of the interphase deviated from additive predictions. Correspondence between the decrease in specific volume from macroscopic density and the decrease in free volume hole size from positron annihilation lifetime spectroscopy suggested that densification of the interphase occurred primarily by a decrease in free volume hole size rather than by a decrease in the number of free volume holes. The volume change did not directly correlate with the parameter. At present, the origin of the volume change is not clear.

Eliminating the Enhanced Mobility at the Free Surface of Polystyrene: Fluorescence Studies of the Glass Transition Temperature in Thin Bilayer Films of Immiscible Polymers

“…In addition, these results indicate that multilayer films with layer thicknesses at or near the nanoscale [63][64][65] and nanostructured or quasi-nanostructured polymer blends with substantial interfacial area [66][67][68] have the potential for properties that are strongly modified from those expected on the basis of the behavior of bulk, neat polymer or thin films of individual polymers. Bilayer and multilayer experiments employing fluorescence dyes in one layer provide a particularly sensitive method for characterizing novel behavior associated with nanostructured multilayer films and nanostructured blends, and further studies are underway.…”

Oxygen transport as a solid‐state structure probe for polymeric materials: A review

“…74,75 The scientifically and technologically important interphase between two immiscible polymers is probed with assemblies of thousands of alternating layers of two glassy polymers, with the individual layer thickness on the nanometer size scale of the interphase. 76,77 By sensing the composite nature of the assembly, gas transport becomes a primary method for extracting the dimension and other fundamental characteristics of the interphase. Nanolayer assemblies of crystalline polymers are also fabricated by layer-multiplying coextrusion.…”

Impact of Nanoscale Confinement on Crystal Orientation of Poly(ethylene oxide)

“…Fabrication of films with hundreds or thousands of confined nanolayers of almost any melt-processible polymer is possible. [15,16] The continuous confining layers provide long-range, almost defect-free confinement. We discovered that large single crystal-like lamellae, previously obtained only from solution, form when poly(ethylene oxide) (PEO) crystallizes under nanolayer confinement.…”