Abstract：
Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport out of pharmaceutical pellets. Water-soluble HPC leaches out and forms a porous structure that controls the drug transport. Industrially, the pellets are coated using a fluidized bed spraying device, and a layered film exhibiting varying porosity and structure after leaching is obtained. A detailed understanding of the formation of the multilayered, phase-separated structure during production is lacking. Here, we have investigated multilayered EC/HPC films produced by sequential spin-coating, which was used to mimic the industrial process. The effects of EC/HPC ratio and spin speed on the multilayer film formation and structure were investigated using advanced microscopy techniques and image analysis. Cahn-Hilliard simulations were performed to analyze the mixing behavior. A gradient with larger structures close to the substrate surface and smaller structures close to the air surface was formed due to coarsening of the layers already coated during successive deposition cycles. The porosity of the multilayer film was found to vary with both EC/HPC ratio and spin speed. Simulation of the mixing behavior and in situ characterization of the structure evolution showed that the origin of the discontinuities and multilayer structure can be explained by the non-mixing of the layers.
摘要：
多孔相分离的乙基纤维素/羟丙基纤维素(EC/HPC)膜用于控制药物从药物小丸的运输。水溶性HPC浸出并形成控制药物运输的多孔结构。在工业上,使用流化床喷雾装置对颗粒进行包衣，以及在浸出后获得表现出变化的孔隙率和结构的层状膜。详细了解多层的形成,生产过程中缺乏相分离结构。这里,我们已经研究了通过顺序旋涂生产的多层EC/HPC薄膜，用来模仿工业过程。使用先进的显微镜技术和图像分析研究了EC/HPC比率和旋转速度对多层膜形成和结构的影响。进行Cahn-Hilliard模拟以分析混合行为。由于在连续沉积循环期间已经涂覆的层的粗化,形成了具有靠近衬底表面的较大结构和靠近空气表面的较小结构的梯度。发现多层膜的孔隙率随EC/HPC比和旋转速度而变化。混合行为的模拟和结构演化的原位表征表明，不连续性和多层结构的起源可以通过层的非混合来解释。
