Polyurethane Shape memory effect

Key words shape memory polymer, shape memory polyurethane, shape memory effect, high performance shape memory polymer. 

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. 

Jeong, H. M., Ahn, B. K., and Kim, B. K. 2001. Miscibility and shape memory effect of thermoplastic polyurethane blends with phenoxy resin. European Polymer Journal 37 2245-2252. 

Ajili, S. H., Ebrahimi, N. G., and Soleimani, M. 2009. Polyurethane/polycapro-lactane blend with shape memory effect as a projxjsed material for cardiovascular implants. Acta Biomaterialia 5 1519-1530. 

Farzaneh, S., Fitoussi, J., Lucas, A., BocqueL M., and Tcharkhtchi, A. (2013) Shape memory effect and properties memory effect of polyurethane. Journal of Applied Polymer Science, 128, 3240-3249. 

Wache et al. were the first to report on the development of an SMP stent as a new vehicle for drug delivery in 2003 [39]. Prototype stents were manufactured using a thermoplastic polyurethane, which was injection molded, extruded, then tested in vitro. In this study, the activation temperature was set in close proximity to body temperature, though details on optimizing the shape-memory effect were not reported. 

The Maitland research group is the leader in developing SMPs for clot-removal devices. In 2002, two studies were reported using thermoset polyurethanes for stroke treatment [45,46]. In the first study, an SMP device was manufactured as a wire that first punctures the clot, is then activated to coil on the distal side of the clot, and is then finally retracted for removal (Fig. 3) [45]. Using an in vitro setup, the prototype devices were shown to activate and hold a porcine blood clot at pressures up to ten times that of the neurovasculature. In a follow up study, laser activation of the shape-memory effect was investigated for the coil clot extraction device along with novel umbrella extraction devices and embolic coils [46]. Laser activation allows the devices to be heated past body temperature to trigger the shape-memory... 

Orthodontics is an area in which polymers are desirable for both their esthetic appeal and shape-memory effect. In 2007, Eliades published an opinion paper on projected future materials for orthodontics and discussed research into polymer-based archwires [67]. In the following year, Jung and Cho demonstrated the use of shape-memory polyurethanes for arch wires [68]. An in vitro dental model was used to test the correction of misaligned teeth and can be seen in Fig. 10. The melt spun polymer, synthesized from 4,4 -methylene bis(phenylisocyanate) and PCL-diol, was stretched to the length required to realign the teeth and attached to stainless... 

Moisture and water uptake into the SMP matrix can be utilized in a unique way to facilitate the shape-memory effect. Recently, Huang and Yang et al. demonstrated the use of water uptake to drive shape memory in Mitsubishi Heavy Industry s MM3520 polyurethane (Fig. 11) [118,119,123]. In this study, free and bound water... 

Fig. 11 Example of water uptake driving the shape-memory effect in a polyurethane SMP. The Tg of the SMP was 35°C. Shape memory was programmed at 40°C and then cooled and stored at room temperature for 1 week. The figure shows recovery in room temperature water as a function of time. (Reprinted with permission from [118] 2005, American Institute of Physics)...

YangBetal (2005) Qualitative separation of the effects of carbon nano-powder and moisture on the glass transition temperature of polyurethane shape memory polymer. Scr Mater... 

Cho JW, Lee SH (2004) Influence of silica on shape memory effect and mechanical properties of polyurethane-silica hybrids. Eur Polym J 40 1343-1348... 

Xu J, Shi W, Pang W (2006) Synthesis and shape memory effects of Si-O-Si cross-linked hybrid polyurethanes. Polymer 47(l) 457-465... 

Zhu Y, et al. Effect of cationic group content on shape memory effect in segmented polyurethane cationomer. J Appl Polym Sci 2007 103(1) 545—56. 

Chen SJ, Hu JL, Chen SG. Studies of the moisture-sensitive shape memory effect of pyridine-containing polyurethanes. Polym Int 2012 61(2) 314—20. 

Yu, Y.-J., Hearon, K., Wilson, T.S., Maitland, D.J., 2011. The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams. Smart Materials and Structures 20, 6 p. 

W. Wang, P. Ping, X. Chen, X. Jing, Shape memory effect of poly(L-lactide)- based polyurethanes with different hard segments, Polym. Int. 56 (2007) 840-846. 

Hearon K, Smith SE, Maher CA, Wilson TS, Maitland DJ. The effect of free radical inhibitor on the sensitized radiation crosslinking and thermal processing stabilization of polyurethane shape memory polymers. Radiat Phys Chem 2013 83 111-21. 

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