Shape‐memory polymers (SMPs) induced by heat or water are commonly used candidates for biomedical applications. Shape recovery inevitably leads to a dramatic decrease of Young's modulus due to the enhanced flexibility of polymer chains at the transition temperature. Herein, the principle of phase‐transition‐induced stiffening of shape‐memory metallic alloys (SMAs) is introduced to the design of molecular structures for shape‐memory polyurethane (SMPUs), featuring all‐hard segments composed of main chains that are attached with poly(ethylene glycol) (PEG) dangling side chains. Different from conventional SMPs, they achieve a soft‐to‐stiff transition when shape recovers. The stiffening process is driven by water‐triggered segmental rearrangement due to the incompatibility between the hard segments and the soft PEG segments. Upon hydration, the extent of microphase separation is enhanced and the hard domains are transformed to a more continuous morphology to realize more effective stress transfer. Meanwhile, such segmental rearrangement facilitates the shape‐recovery process in the hydrated state despite the final increased glass transition temperature (Tg). This work represents a novel paradigm of simultaneously integrating balanced mechanics, shape‐memory property, and biocompatibility for SMPUs as materials for minimally invasive surgery such as endoluminal stents.
Shape memory polymers (SMPs) with multiple functionalities have great potential in implantable biomedical devices, especially vascular stents. However, stents made of SMPs are generally faced with the problem of insufficient...
Biodegradable shape memory polymers are promising biomaterials for stents used in minimally invasive surgical procedures such as intestinal stents. Herein, a series of biodegradable shape memory polyurethanes (SMPUs) containing a novel phenylalanine‐derived chain extender (PHP) are synthesized. Inspired by the fact that the function of biomacromolecules such as proteins is rich and varied because of the multiple combinations of the amino acid in highly evolved biosystems, this study finds that the sequence distribution of PHP in SMPU will also have a great influence on the phase structure and degradation behavior, especially the difference of surface morphology caused by degradation. Considering that the transition temperature (Ttrans) of SMPU obtained is higher than physiological temperature, oxidized carbon black (OCB) with the ability of photothermal conversion is introduced into SMPU, which can not only endow SMPU with near‐infrared response shape recovery characteristics, but also enhance phase separation degree and mechanical properties of them. SMPU/OCB composites show excellent shape memory effect and rapid photothermal response, and they can be degraded by chymotrypsin with an adjustable degradation rate. These SMPU/OCB composites show broad potential for application as intestinal stents.
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