4.8 Article

Water-Triggered Stiffening of Shape-Memory Polyurethanes Composed of Hard Backbone Dangling PEG Soft Segments

期刊

ADVANCED MATERIALS
卷 34, 期 46, 页码 -

出版社

WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202201914

关键词

biocompatibility; microphase separation; morphology transformation; shape-memory polyurethanes; water-triggered stiffening

资金

  1. National Natural Science Foundation of China [51973134, 51733005]
  2. NSAF [U1930204]

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This article introduces a new method to achieve a soft-to-stiff transition in shape-memory polyurethane by incorporating the principle of phase-transition-induced stiffening. By triggering segmental rearrangement and transformation of hard domains through water, the material achieves improved stress transfer and shape recovery.
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 (T-g). 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.

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