Functionally Graded Shape Memory Polymer

Abstract

A functionally graded shape memory polymer (SMP) that has a range of transition temperatures that are spatially distributed in a gradient fashion within one single article. The SMP is formed by post-curing a pre-cured glassy SMP in a linear temperature gradient that imposes different vitrification temperature limits at different positions along the gradient. Utilizing indentation-based surface shape memory coupled with optical measurements of photoelastic response, the capability of this material to respond over a wide range of thermal triggers is correlated with the graded glass transition behavior. This new class of SMP offers great potential for such applications as passive temperature sensing and precise control of shape evolution during a thermally triggered shape recovery.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to U.S. Provisional Patent Application No. 61 / 444,298, filed on Feb. 18, 2011, which is hereby incorporated by reference herein in its entirety.STATEMENT OF FEDERALLY SPONSORED RESEARCH[0002]The U.S. Government may have a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Grant No. DMR-0907578 of the National Science Foundation (NSF) and Grant No. FA9550-09-1-0195 of the Air Force Office of Scientific Research (AFOSR).BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]The present invention relates to shape memory polymers and, more specifically, to a shape memory polymer having a range of transition temperatures that are spatially distributed in a gradient fashion within one single article.[0005]2. Description of the Related Art[0006]Shape memory polymers (SMPs) are a ...

AI Technical Summary

Benefits of technology

[0012]In accordance with the foregoing objects and advantages, the present invention applies the concept of functionally graded materials (FGMs) to SMPs. Specifically, the present invention involves SMPs with spatially distributed transition temperatures and the methods to prepare such materials. The term, FGM, refers to any synthetic material that has spatially dependent compositions, microstructures and associated properties. The FGM concept has engaged a significant amount of research effort since its first introduction in the 1980s, with applications ranging from aerospace to tissue engineering. A variety of fabrication and processing techniques have been developed for polymeric FGMs, including UV polymerization with patterned photo-filters, photodegradation with a gradually removed mask, thermal curing in a temperature gradient, controlled interdiffusion of polymer bilayers, co-extrusion with specially designed gradient distribution and 2-dimensional mixing units, and extrusion followed by laminate molding. However none of these techniques has ever been applied to SMPs and the preparation of SMPs with functionally graded properties.

[0013]The new shape memory polymers may exist as films, coatings, or adhesives, and feature a continuous gradient, of shape memory transition temperatures from one portion of the sample to another. As a consequence, thermally stimulated recovery of a temporary configuration to the permanent configuration occurs with spatial localization. In one embodiment where the special localization of transition temperature is in the form of a conti...

Problems solved by technology

However none of these techniques has ever been applied to SM...

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