(105c) Gradient Multilayer Films by Forced Assembly Coextrusion

?Forced assembly? polymer coextrusion is a unique processing technique utilizing novel layer multiplication dies to produce films with tens or thousands of micron to nanometer thick layers. To date, ?forced assembly? coextrusion has been limited due to the use of equal splitting layer multipliers. The development of novel ?uneven? split layer multiplying dies has enabled the production of multilayered polymer films with different layer thickness distributions. Coextrusion through a series of ?uneven? split multiplier dies has successfully produced multilayered polymer films with up to a 10X difference between the thickest and thinnest layers. Coupling ?forced assembly? coextrusion processing with the existing equal and novel ?uneven? split multiplier dies allows for unparalleled flexibility in the design and processing of different gradient multilayer film distributions by: (1) altering the off-set magnitude of the die splitting ratio and (2) changing the sequencing of a series of ?uneven? split layer multiplying dies with different off-set splitting ratios.

The added flexibility in the design of gradient layer thickness distributions allows for the development of polymer films with unique properties for a variety of applications. The creation of highly reflective, multilayered polymeric photonic crystal film systems will be described. Inclusion of step, or gradient, layer thickness distributions within these photonic film systems resulted in widening the optical reflection band, and in some cases, produced multiple optical reflections within a single film. These gradient micro- or nanolayered photonic crystal films can be tailored to give optical reflections in UV, visible, or NIR wavelengths based on individual layer thicknesses in the micron or nanometer thickness range. Further exploration of novel gradient layer thickness distributions are planned to investigate how additional multilayered polymer film systems may be developed for controlled particle diffusion or release and to produce films with unique anisotropic structures and properties.