Chumakova Natalia A, Golubeva Elena N, Kuzin Sergei V, Ivanova Tatiana A, Grigoriev Igor A, Kostjuk Sergey V, Melnikov Mikhail Ya
Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskiye Gory, 1/3, 119991 Moscow, Russia.
Vorozhtsov Novosibirsk Institute of Organic Chemistry Siberian Branch, Russian Academy of Sciences, Lavrentiev Ave., 9, 630090 Novosibirsk, Russia.
Polymers (Basel). 2020 Dec 18;12(12):3046. doi: 10.3390/polym12123046.
A novel approach based on convolution of the electron paramagnetic resonance (EPR) spectra was used for quantitative study of the release kinetics of paramagnetic dopants from poly(d,l-lactide) films. A non-monotonic dependence of the release rate on time was reliably recorded. The release regularities were compared with the dynamics of polymer structure changes determined by EPR, SEM, and optic microscopy. The data obtained allow for the conclusion that the main factor governing dopant release is the formation of pores connected with the surface. In contrast, the contribution of the dopant diffusion through the polymer matrix is negligible. The dopant release can be divided into two phases: release through surface pores, which are partially closed with time, and release through pores initially formed inside the polymer matrix due to autocatalytic hydrolysis of the polymer and gradually connected to the surface of the sample. For some time, these processes co-occur. The mathematical model of the release kinetics based on pore formation is presented, describing the kinetics of release of various dopants from the polymer films of different thicknesses.
一种基于电子顺磁共振（EPR）光谱卷积的新方法被用于定量研究顺磁性掺杂剂从聚（d，l-丙交酯）薄膜中的释放动力学。可靠地记录了释放速率对时间的非单调依赖性。将释放规律与通过EPR、扫描电子显微镜（SEM）和光学显微镜确定的聚合物结构变化动力学进行了比较。所获得的数据可以得出结论，控制掺杂剂释放的主要因素是与表面相连的孔隙的形成。相比之下，掺杂剂通过聚合物基体扩散的贡献可以忽略不计。掺杂剂释放可分为两个阶段：通过随时间部分封闭的表面孔隙释放，以及通过聚合物基体内部由于聚合物的自催化水解最初形成并逐渐与样品表面相连的孔隙释放。在一段时间内，这些过程同时发生。提出了基于孔隙形成的释放动力学数学模型，该模型描述了不同厚度聚合物薄膜中各种掺杂剂的释放动力学。
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