Water-Triggered Stiffening of Shape-Memory Polyurethanes Composed of Hard Backbone Dangling PEG Soft Segments
Water-Triggered Stiffening of Shape-Memory Polyurethanes Composed of Hard Backbone Dangling PEG Soft Segments
复制标题
水引发由硬骨架悬挂 PEG 软链段组成的形状记忆聚氨酯的硬化
DOI：
10.1002/adma.202201914
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发表时间：
2022-06-02
影响因子：
29.4
通讯作者：
Fu, Qiang
中科院分区：
文献类型：
--
作者：
Liu, Wenkai;Wang, Ao;Fu, Qiang
由热或水诱导的形状记忆聚合物（SMP）是生物医学应用中常用的候选材料。形状恢复不可避免地导致杨氏模量的急剧下降，这是由于在转变温度下聚合物链的柔性增强。本文将形状记忆金属合金（SMA）的相变诱导硬化原理引入到形状记忆聚氨酯（SMPU）的分子结构设计中，SMPU具有由主链与聚乙二醇（PEG）悬挂侧链组成的全硬链段。与传统的SMP不同，当形状恢复时，它们实现了软到硬的过渡。硬化过程是由水引发的链段重排驱动的，这是由于硬链段和软PEG链段之间的不相容性。在水化时，微相分离的程度增强，并且硬畴转变为更连续的形态以实现更有效的应力传递。同时，这种链段重排促进了水合状态下的形状恢复过程，尽管最终的玻璃化转变温度（T-g）增加。这项工作代表了一种新的范式，同时整合平衡力学，形状记忆性能，和生物相容性的SMPU作为材料的微创手术，如腔内支架。
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.