Shape memory polymers applications

The PPDX-fr-PCL diblock copolymers were recently synthesized [111] and apart from the references already mentioned, only the contribution of Lendlein and Langer [112] deals with chemically similar materials, although structurally quite different since they employed multiblock copolymers of PPDX and PCL with very low molecular weights to prepare shape memory polymers for biomedical applications. 

Other materials have been found that have shape memories. Shape-memory polymers are plastics that have properties similar to SMAs. Pliable materials have recently been found that can be stretched up to twice their normal length, yet regain their shape when heated. Having a smart plastic material opens up applications of a softer, more flexible nature, such as clothing. 

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. 

Lendlein, A., and R. Langer 2002. Biodegradable, elastic shape-memory polymers for potential biomedical applications. Science 296 1673-76. Supporting material www.sdencemag.orglcgj/content full/1066102/DC1. 

Silicones, 5,113-114,135-136,261 Silk, 33-34,47, 61, 66,171 Silly Putty, 125-126,262 Silver Spencer 129 Silver halide, 122 Single-site catalysts, 106-107 Smart materials, 206-209, 218 for food packaging, 206-207 for military applications, 208 sensors for, 207,208 shape-memory polymers, 207-208 Society of Automotive Engineers (SAE), 121 Sodium acrylate, 122 ... 

To date, heat-triggered shape memory polymers have had the greatest share of research and application adaptation. However, trigger mechanisms could also be chemo-responsive, e.g., water, ethanol, and pH change photo-responsive, e.g., UV or IR, including radio waves and/or mechano-responsive, e.g., stretching, impact, etc. 

Ahmad, M., Luo, J., Miraftab, M., 2012. Feasibility study of polyurethane shape-memory polymer actuators for pressure bandage application. Science and Technology of Advanced Materials 13, 015006 (7 pp.). 

Hu, J., Zhu, Y., Huang, H., Lu, J., 2012. Recent advances in shape—memory polymers structure, mechanism, functionality, modeling and applications. Progress in Polymer... 

Xu, J., Song, J., Thermal Responsive Shape Memory Polymers for Biomedical Applications, Department of Orthopedics Physical Rehabilitation, Department of Cell Biology, University of Massachusetts Medical School, Worcester, USA. 

A. Ixndlein, M. Behl, B. Hiebl, C. Wischke, Shape-memory polymers as a technology platform for biomedical applications. Expert Rev. Med. Devices 7 (2010) 357-379. 

M.C. Serrano, G.A. Ameer, Recent insights into the biomedical applications of shape-memory polymers, Macromol. Biosci. 12 (2012) 1156-1171. 

Shape memory polymers make up another class of injectable biomaterials for vascular applications, yet are relatively new in the field of endovascular embolization. Shape memory polymers are chemically structured so that they are able to reversibly take on a different physical shape in response to some stimuli (Small et al, 2007). Usually these different shapes include a compact form and an expanded form of the polymer. In the case of endovascular embolization, the expanded polymer can be pre-formed to fit specific contours of an individual aneurysm (Ortega et al, 2007). Upon interacting with some type of stimuli, such as heat or cold, the material is compacted into a shape that can be delivered through a microcatheter. The process of using shape memory polymers to embolize an aneurysm is shown in Fig. 7.5, along with samples of expanded SMPs (Ortega et al, 2007). 

These materials have an obvious application to fusiform aneurysms, which are difficult to treat using coils or liquid embolics due to migration into the parent vessel. Shape memory polymers can potentially remove this limitation since the device is pre-formed to the aneurysm topography. Metcalf et al (2003) investigated a porous polyurethane shape memory polymer as an embolic device for fusiform aneurysms in an animal model. In this study, thick neointimal formation was found over aneurysm necks after a 12-week period. The porous nature of this material may have encouraged cell infiltration and neointimal growth to seal off the aneurysm from the rest of the vasculature (Metcalfe et al,... 

In more recent times, the possibilities enabled by utilising the reversible nature [11] of supramolecular interactions has resulted in their introduction into materials chemistry [12, 13]. The driving force for such studies is that the strength of supramolecular interactions can be reversibly altered by application of external stimuli. In the case of materials chemistry, this means that a physical property of the material (for example, its tensile strength) can be changed in real time and in situ. This feature has transformative potential in numerous applications, including those as healable materials [14-24] and shape-memory polymers [25-28]. 

Stimuli-responsive materials have sparked enormous interest in recent years due to their potential applications in micro-machines, soft robots, biomedical systems, etc. [1-6]. A variety of intelligent polymeric materials such as shape memory polymers [7, 8], polymer gels [9, 10], conducting polymers [11, 12], and dielectric elastomers [13,14] have been developed for these applications. Compared to other stimulus-driven methods including pressure [15], heat [16, 17], electric field... 

One of the important developments in, and applications of, textiles is the manufacture of intelligent waterproof breathable fabrics based on shape memory polymers using shape memory polyurethanes. The fabric restricts the loss of body warmth by stopping... 

---