Shape memory foams

Medical applications of biodegradable shape memory polymers include their use for removing blood clots formed during strokes. Preshaped foams can be used to fill cranial aneurisms. Loosely tied sutures made from fibers that have been stretched at 50 °C will tighten when heated just above room temperature. 

A number of manufactured products comprising thermoplastics (polyethylene, polyvinylchloride, polyamides,. ..) or elastomers (natural rubber, nitrile rubber, ethylene propylene rubber, silicones) are processed by cross-linking to improve their performances in insulated electric wires and cables, multilayered films for cooking pouches, shape memory tubes, pressure resistant water pipes, expandable foams, automotive parts exposed to motor... 

More sophisticated versions of SMPs are those based on the so-called cold hibernated elastic memory as self-deployable intelligent structures (Sendijarevic, 2003). This technology is based on polyurethane foams whereby shape memory effect is combined with elastic recovery of the foam, thus allowing them to be packed into the smallest possible form and inserted into the body via catheters. Given the foam s excellent biocompatibility, porosity, and lightness, they can potentially be used in many other forms, e.g., orthopaedic braces and splints, vascular and coronary crafts, as well as other equally vital prosthetics and implants. 

Sendijarevic, V., 2003. Foams Having Shape Memory, US Patent 6583194 B2. 

J. Rodriguez, F. Qubb, T. Wilson, M. Miller, T. Fossum, J. Hartman, E. Tuzun, P. Singhal, D. Maitland, In vivo response to an implanted shape memory polyurethane foam in a porcine aneurysm model. J. Biomed. Mater. Res. A (2013) doi 10.1002/jbm.a,34782. 

Ortega, J., Maitland, D., Wilson, T., Tsai, W., Savas, O. Saloner, D. (2007) Vascular dynamics of a shape memory polymer foam aneurysm treatment technique. Annals of Biomedical Engineering, 35, 1870-1884. 

John, M. and Li, G. (2010) Self-healing of sandwich stmctures with grid stiffened shape memory polymer syntactic foam core. Smart Materials and Structures, 19, paper 075013 (12 pages). 

Thermoset Shape Memory Polymer and Its Syntactic Foam... 

If microballoons are dispersed in a shape memory polymer matrix, smart syntactic foam is obtained. Like conventional polymer based syntactic foam, thermosetting shape memory polymer syntactic foam has all the advantages associated with polymeric syntactic foam, in addition to its shape memory properties and healing capabihties, as will be discussed in Chapter 6. In the following, the focus will be on a thermosetting polystyrene shape memory polymer and its syntactic foam. 

Figure 3.32 SEM observation of the original microstmcture of the foam (a), the effect of programming on changing the microstmcture ((b), (d), and (e)), and the effect of shape memory on recovering the microstmcture (c). Source [42] Reproduced with permission from Elsevier...

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