Yoo Youngman, Martinez Carlos, Youngblood Jeffrey P
School of Materials Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
Langmuir. 2017 Feb 14;33(6):1521-1532. doi: 10.1021/acs.langmuir.6b04628. Epub 2017 Jan 31.
The aim of this study is to develop methods to reinforce polymeric microspheres with cellulose nanocrystals (CNCs) to make eco-friendly microcapsules for a variety of applications such as medicines, perfumes, nutrients, pesticides, and phase change materials. Surface hydrophobization treatments for CNCs were performed by grafting poly(lactic acid) oligomers and fatty acids (FAs) to enhance the dispersion of nanoparticles in the polymeric shell. Then, a straightforward process is demonstrated to design sustained release microcapsules by the incorporation of the modified CNCs (mCNCs) in the shell structure. The combination of the mCNC dispersion with subsequent interfacial polyurea (PU) to form composite capsules as well as their morphology, composition, mechanical properties, and release rates were examined in this study. The PU microcapsules embedded with the mCNC were characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The morphologies of the microcapsules were characterized by optical microscopy (OM) and scanning electron microscope (SEM). The rupture stress and failure behavior of the microcapsules were determined through single-capsule compression tests. Oil-soluble Sudan II dye solution in mineral oil was utilized as a model hydrophobic fill, representing other latent fills with low partition coefficients, and their encapsulation efficiency was measured spectroscopically. The release rates of the encapsulated dye from the microcapsules were examined spectroscopically by both ethanol and 2-ethyl-1-hexanol medium at room temperature. The concentration of released dye was determined by using UV-vis absorption spectrometry (UV-vis). The mCNC embedded poly(urea-urethane) capsules have strong and dense walls, which function as excellent barriers against leakage due to their extended diffusion path length and ensure enough mechanical strength from rupture for handling or postprocessing.
本研究的目的是开发用纤维素纳米晶体（CNCs）增强聚合物微球的方法，以制备用于多种应用的环保型微胶囊，如药物、香水、营养物质、农药和相变材料。通过接枝聚乳酸低聚物和脂肪酸（FAs）对CNCs进行表面疏水化处理，以提高纳米颗粒在聚合物壳中的分散性。然后，展示了一种直接的方法，通过在壳结构中掺入改性CNCs（mCNCs）来设计缓释微胶囊。本研究考察了mCNC分散体与后续界面聚脲（PU）形成复合胶囊的情况，以及它们的形态、组成、机械性能和释放速率。用傅里叶变换红外光谱（FT-IR）和热重分析（TGA）对嵌入mCNC的PU微胶囊进行了表征。用光学显微镜（OM）和扫描电子显微镜（SEM）对微胶囊的形态进行了表征。通过单胶囊压缩试验测定了微胶囊的破裂应力和破坏行为。将矿物油中的油溶性苏丹II染料溶液用作模型疏水填充物，代表其他具有低分配系数的潜在填充物，并通过光谱法测量其包封效率。在室温下，用乙醇和2-乙基-1-己醇介质通过光谱法考察了微胶囊中包封染料的释放速率。用紫外-可见吸收光谱法（UV-vis）测定释放染料的浓度。嵌入mCNC的聚（脲-聚氨酯）胶囊具有坚固致密的壁，由于其延长的扩散路径长度，它们起到了防止泄漏的优良屏障作用，并确保了足够的机械强度以防止在处理或后处理过程中破裂。
