Gradient Multilayer Films by Forced Assembly Coextrusion

Abstract

Forced assembly polymer coextrusion utilizes layer multiplication to produce films with tens or thousands of micrometer to nanometer thick layers. The development of novel uneven split layer multiplying dies has produced gradient multilayer films with at least a 10 times difference between the thickest and thinnest layers. Coextrusion through a series of equal and uneven split multiplier dies allows for flexibility in the unique design of layer thickness distributions by: (1) altering the multiplier offset and (2) changing the sequence of a series of uneven split multiplying dies with different splitting ratios. This new technology has created highly reflective, multilayered photonic films with gradient layer thickness distributions exhibiting, as examples, a 600 nm wide reflection band and dual optical reflection bands within a single film. Also, gradient multilayers exhibit unique mechanical behavior. A layer thickness dependent craze to shear banding deformation mechanism was observed. In addition, gradient controlled buckling was observed across a single film due to foaming-induced layer delamination.

Viscosity contrast effects on the structure – Property relationship of multilayer soft film/foams

“…Recently, Baer et al [24][25][26][27][28][29][30][31][32][33][34][35] reported a miniaturized multilayer coextrusion technique. Such multilayer coextrusion represents an advanced polymer processing technique that combines two or more polymers in a layered configuration with controlled architecture.…”

Functional Macromolecular Systems: Kinetic Pathways to Obtain Tailored Structures

“…The combination of advanced experimental techniques, theoretical modeling, and computer simulation will not only accelerate our better understanding of these fascinating phenomena but also open new doors for the development of new materials with tailored properties. We did not address other important research areas in this field, such as melt processing of polymers by extrusion which can also result in highly functional materials such as 1D photonic crystals . In parallel to the physical questions addressed in this contribution, also interesting developments are going on in the area of non‐equilibrium chemical reactions.…”

Nondestructive metrology of layered polymeric optical materials using optical coherence tomography

“…A significant breakthrough is a process to produce nanolayer polymer film based GRIN optical components with an unparalleled control of their internal refractive index distribution [1]. This fabrication process, based on nanolayer co-extrusion of polymer film processing [2], is capable of producing polymer films comprised of a plurality of nanolayers, each with thickness constrained below the quarter-wavelength of visible light. The refractive indices of these thin films are controlled, based on the effective medium theory predictions, by tuning the ratio of the constituent polymerically compatible raw materials with substantially different refractive indices prior to film co-extrusion.…”