Polymer systems with multiple shape memory effect
A polymer material system that consists of multiple layers of polymers of different transition temperatures in a multilayer construction to achieve and tailor a multiple shape memory effect. Wherein two material layers of different transition temperatures are utilized, a triple shape memory effect is achieved. In alternative embodiments, a triple shape memory effect may be achieved wherein each of the two layers are transformable using different external stimulus such as heat, light, magnetism, or moisture.
1. A method for forming a polymer system having at least a triple shape memory effect, the method comprising:
selecting a first polymeric material responsive to a first external stimulus having a first glass transition temperature;
selecting a second polymeric material having a second glass transition temperature, wherein said second polymeric material is responsive to a second external stimulus, said second external stimulus is different than said first external stimulus,
forming a first polymeric material layer from said first polymeric material having a desired thickness and a desired modulus;
forming a second polymeric material layer from said second polymeric material having a desired thickness and a desired modulus;
coupling said first polymeric material layer to said second polymeric material layer to allow covalent bonding between said first and second polymeric materials to form a bi-layer polymeric material with a strong interface, wherein said first glass transition temperature and said second glass transition temperature are well separated such that the dynamic mechanical analysis curve of said bi-layer polymeric material has a mid-level plateau in storage modulus between the first and second glass transition temperatures, and said bi-layer polymeric material is capable of being transformed between an original permanent shape, a first temporary shape, and a second temporary shape without delamination between said first polymeric material layer and said second polymeric material by application of said first external stimulus or by application of said second external stimulus and wherein said original permanent shape exhibits no strain.
2. The method of claim 1 , further comprising transforming said bi-layer polymeric material from said original shape to said first temporary shape by:
applying said first external stimulus to said bi-layer polymeric material and deforming said bi-layer polymeric material under a first stress from said original permanent shape to said first temporary shape; and
removing said first external stimuli while maintaining said bi-layer polymeric material under said first stress.
3. The method of claim 2 , further comprising transforming said bi-layer polymeric material from said first temporary shape to said second temporary shape by:
applying said second external stimulus to said bi-layer polymeric material under a second stress to transform said bi-layer polymeric material from said first temporary shape to said second temporary shape; and
removing said second external stimulus while maintaining said bi-layer polymeric material under said first stress.
4. The method of claim 3 further comprising:
applying said first external stimulus in the absence of stress to recover said bi-layer polymeric material from said second one of said at least two temporary shapes to said first one of said at least two temporary shapes.
5. The method of claim 4 further comprising:
applying said second external stimulus in the absence of stress to recover said bi-layer polymeric material from said first one of said at least two temporary shapes to said original shapes.
6. The method of claim 2 , wherein said first external stimulus comprises at least one of the group of temperature, magnetism, light or moisture, and said thickness and modulus of said first and second polymeric material layers are configured to provide shape fixities of at least 76% and shape recovery of at least 91% for said first temporary shape and second temporary shape.
7. The method of claim 3 , wherein said second external stimulus comprises at least one of the group of temperature, magnetism, light or moisture.
8. The method of claim 1 , wherein at least one of said first polymeric material layer and said second polymer material layer comprises an epoxy thermosetting polymeric material.