Abstract
Polymers with the shape memory effect possess tremendous potential for application in diverse fields, including aerospace, textiles, robotics, and biomedicine, because of their mechanical properties (softness and flexibility) and chemical tunability. Biodegradable shape memory polymers (BSMPs) have unique benefits of long-term biocompatibility and formation of zero-waste byproducts as the final degradable products are resorbed or absorbed via metabolism or enzyme digestion processes. In addition to their application toward the prevention of biofilm formation or internal tissue damage caused by permanent implant materials and the subsequent need for secondary surgery, which causes secondary infections and complications, BSMPs have been highlighted for minimally invasive medical applications. The properties of BSMPs, including high tunability, thermomechanical properties, shape memory performance, and degradation rate, can be achieved by controlling the combination and content of the comonomer and crystallinity. In addition, the biodegradable chemistry and kinetics of BSMPs, which can be controlled by combining several biodegradable polymers with different hydrolysis chemistry products, such as anhydrides, esters, and carbonates, strongly affect the hydrolytic activity and erosion property. A wide range of applications including self-expending stents, wound closure, drug release systems, and tissue repair, suggests that the BSMPs can be applied as actuators on the basis of their shape recovery and degradation ability.
Highlights
Shape memory material (SMM) is a material capable of recovering the original shape in response to particular stimuli
This study shows that the decrease of molecular weight of hard segments by degradation may decrease the shape recovery rate, as seen in Figure 2e [54]
The breaking stress and strain of a stent prepared by Jaworska et al containing 7 wt% of a drug decreased to approximately 70% of the stent without the drug because the aggregated drug particles induced notch effects; this study showed that drug incorporation can change stent hydrophilicity and the hydrolysis degradation rate [91,98]
Summary
Shape memory material (SMM) is a material capable of recovering the original shape in response to particular stimuli. Effective manufacturing of shape-memory nickel–titanium alloy (SMA) by using spark-plasma sintering method was reported, increasing the purity of the product by preventing the chemical inhomogeneity and oxidation introduced during the multi-step conventional method [12]. The high melting temperature and reactivity of SMAs continue to make their manufacture more complex than shape memory polymers (SMPs) [15]. SMPs are lightweight, low-priced, tunable, and more deformable compared to shape memory alloys (SMAs) [8,10,16]. The basic principle of SMPs is briefly introduced, and the design strategies required to induce the thermomechanical properties and shape memory performance of biodegradable shape memory polymers (BSMPs) are discussed. Many studies aimed at reducing the shape recovery time of stents and combining stents with drug release ability are reviewed
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