Shape Memory Polyurethane Microcapsules with Active Deformation.
Shape Memory Polyurethane Microcapsules with Active Deformation.
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DOI：
10.1021/acsami.0c14882
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发表时间：
2020-09
影响因子：
9.5
通讯作者：
Fenghua Zhang;Tianheng H. Zhao;D. Ruíz-Molina;Yanju Liu;C. Roscini;J. Leng;S. Smoukov
中科院分区：
文献类型：
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作者：
Fenghua Zhang;Tianheng H. Zhao;D. Ruíz-Molina;Yanju Liu;C. Roscini;J. Leng;S. Smoukov
从智能自紧缝合线和可扩张支架到变形飞机机翼，形状记忆结构越来越多地出现在我们的日常生活中。然而，由于缺乏在微米和亚微米水平上合成复杂结构的方法，阻碍了该领域的发展。特别是，这种规模的形状记忆聚合物（SMP）和结构的合成方法以及新几何形状的影响仍有待探索。在这里，我们描述了通过乳化液滴的界面聚合来合成形状记忆聚氨酯（PU）胶囊。乳化液滴含有硬链段的单体，而连续水相含有软链段。采用用于形状记忆 PU 合成的三官能化学交联剂来消除蠕变并提高最终胶囊的回收率。与之前的 SMP 相比，我们观察到恢复率与编程应变量的异常相关性。我们开发了定量表征方法和理论，以表明在处理薄壳物体时，需要替代参数来量化回收率。我们表明，在实现 94-99% 面积恢复率的同时，线性胶囊恢复率可低至 70%。这种量化方法使我们能够根据胶囊中观察到的线性纵横比进行转换，以找出未恢复的区域应变和应力。胶囊的中空结构为某些应用（例如药物输送）提供了高内部体积，这得益于比聚合物颗粒更高的活性成分负载量。我们开发的胶囊合成和编程方法可以很容易地扩展到更大体积的应用。
From smart self-tightening sutures and expandable stents to morphing airplane wings, shape memory structures are increasingly present in our daily life. The lack of methods for synthesizing intricate structures from them on the micron and submicron level, however, is stopping the field from developing. In particular, the methods for the synthesis of shape memory polymers (SMPs) and structures at this scale and the effect of new geometries remain unexplored. Here, we describe the synthesis of shape memory polyurethane (PU) capsules accomplished by interfacial polymerization of emulsified droplets. The emulsified droplets contain the monomers for the hard segments, while the continuous aqueous phase contains the soft segments. A trifunctional chemical cross-linker for shape memory PU synthesis was utilized to eliminate creep and improve the recovery ratios of the final capsules. We observe an anomalous dependence of the recovery ratio with the amount of programmed strain compared to previous SMPs. We develop quantitative characterization methods and theory to show that when dealing with thin-shell objects, alternative parameters to quantify recovery ratios are needed. We show that while achieving 94-99% area recovery ratios, the linear capsule recovery ratios can be as low as 70%. This quantification method allows us to convert from observed linear aspect ratios in capsules to find out unrecovered area strain and stress. The hollow structure of the capsules grants high internal volume for some applications (e.g., drug delivery), which benefit from much higher loading of active ingredients than polymeric particles. The methods we developed for capsule synthesis and programming could be easily scaled up for larger volume applications.