Temperature-Dependent Capsule Shell Bonding and Destruction Based on Hindered Poly(urea-urethane) Chemistry
Temperature-Dependent Capsule Shell Bonding and Destruction Based on Hindered Poly(urea-urethane) Chemistry
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DOI：
10.1021/acs.chemmater.2c00415
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发表时间：
2022-06-28
影响因子：
8.6
通讯作者：
Pentzer, Emily
中科院分区：
文献类型：
--
作者：
Wang, Yifei;Wei, Peiran;Pentzer, Emily
需要具有响应性外壳的胶囊，例如，可以破坏该外壳以释放有效负载或融合在一起以形成整体，以提高控释、材料存储/运输、分子分离等方面的性能。最常见的是，这些壳含有 pH 响应性官能团或温度响应性聚合物，并且壳渗透性会发生变化，例如在 pH 值降低或温度升高时。在此，我们报告了一种通过将受阻聚（脲-氨基甲酸酯）化学物质纳入胶囊壳来制造响应性胶囊以控制融合或破坏的新方法。使用非水皮克林乳液作为模板，我们证明三种不同仲二胺和四种不同二异氰酸酯之间的界面聚合可用于制备具有极性油（N,N-二甲基甲酰胺，DMF）或DMF和离子液体（IL）混合物核的胶囊，其壳含有受阻脲键，在稍微升高的温度下会发生动态键交换。对于核心为油的胶囊，响应温度基于二胺的位阻（35℃、55℃或80℃），与本体聚合物一致，并由变温傅里叶变换红外光谱支持。相比之下，对于核心含有IL的胶囊，所需的温度显着降低，这表明壳被核心液体塑化。将分离的胶囊加热到相关温度会导致胶囊壳融合成整体，而在高温下向分散的胶囊中添加伯胺会导致胶囊壳破坏。使用扫描电子显微镜（SEM）和光学显微镜来确认胶囊、整料或乳液液滴的形态，并使用聚焦离子束-SEM来展示胶囊的核壳结构。此外，胶囊和熔融整体的机械测试的比较凸显了键交换对整体性能的重要性。这项工作表明，含有动态共价键的胶囊壳是一类令人兴奋的新材料，除了传统使用响应性壳来改变渗透性之外，还可用于定制形态。
Capsules with responsive shells that, for example, can be destroyed to release a payload or fused together to create a monolith are needed to improve performance in, for example, controlled release, material storage/transport, molecular separation, and so on. Most commonly, these shells contain pH-responsive functional groups or temperature-responsive polymers and undergo changes in shell permeability, for example, upon decreased pH or increased temperature. Herein, we report a new approach to fabricating responsive capsules for controlled fusion or destruction by the incorporation of hindered poly(urea-urethane) chemistry into capsule shells. Using a non-aqueous Pickering emulsion as a template, we demonstrate that interfacial polymerization between three different secondary diamines and four different diisocyanates can be used to prepare capsules with a core of polar oil (N,N-dimethylformamide, DMF) or a mixture of DMF and ionic liquid (IL) with shells containing hindered urea bonds that undergo dynamic bond exchange in response to slightly elevated temperatures. For the capsules in which the core is oil, the temperature of responsivity is based on the hindrance of the diamine (35, 55, or 80 degrees C), consistent with the bulk polymer, and supported by variable-temperature Fourier transform infrared spectroscopy. In contrast, for capsules in which the core contains IL, the temperature required is significantly decreased, suggesting that the shell is plasticized with the core liquid. Heating isolated capsules to the relevant temperature leads to capsule shell fusion into a monolith, whereas addition of a primary amine to dispersed capsules at elevated temperature leads to shell destruction. Scanning electron microscopy (SEM) and optical microscopy were used to confirm the morphology of capsules, monoliths, or emulsion droplets, and focused ion beam-SEM was utilized to demonstrate the core-shell structure of the capsules. Furthermore, comparison of mechanical tests of the capsules and fused monoliths highlight the importance of bond exchange on bulk properties. This work demonstrates that capsule shells containing dynamic covalent bonds are a new exciting class of materials that can be used to tailor morphology beyond the traditional use of responsive shells to change permeability.