Nanotechnology-aimed Poymer Synthses using Supercritical Fluids

在超临界氟形态下进行了四氟乙烯的均相聚合，观察到聚四氟乙烯S的形态为纤维状，分散均匀地缠绕在一起，密度低，与体系的压力无关。每片宽约100 nm，长约10μm。聚四氟乙烯的数均相对分子质量和转化率分别可在10~10^4~10^6和60%~80%范围内控制。在超临界-超临界氟仿/水乳液中可以进行非均相洗涤剂、无稳定剂聚合。得到了均匀的球形亚微米粒子(200 Nm)，这依赖于压力和体系中的水分含量。研究了聚合物基材的溶胀和超临界流体浸泡等工艺作为聚合物表面改性的一种新途径。在高密度聚乙烯(HDPE)和聚碳酸酯(PC)平板存在下，四氟乙烯(TFE)在SCCO_2或SCCHF_3中聚合。用X射线光电子能谱测定了其表面性质，并用接触角估算了其表面能。渗透到基材上的聚四氟乙烯的厚度和密度取决于超临界流体的条件，如压力或温度。

Homogeneous polymerizations of tetrafluoroethylenes were executed in supercritical fluoroform, and the morphology of the resulting poly (tetrafluoroethylene)s were observed as the fibrous which were dispersedly and uniformly twined with low density, independent of pressure in the systems. Each piece was ca 100 nm in width and 10 μm in long. The number average of molecular weight and conversions of poly (tetrafluoroethylene) can be controlled by pressure and temperature from 10^4 to 10^6, and 60%-80%, respectively. Heterogeneous detergent, stabilizer-free polymerization can be performed in supercritical supercritical fluoroform/water emulsion. Uniform spherical submicron-particles (200 nm) were obtained, dependent of pressure and water content in the systems.Processing of polymer substrates such as swelling and immersing by supercritical fluids have been studied as a new route to a polymer surface modification. Polymerization of tetrafluoroethylenes (TFE) was carried out in scCO_2 or scCHF_3 in the presence of high density polyethylene (HDPE) and polycarbonate (PC) plates. The surface property was determined by X-ray photoelectron spectroscopy, and its surface energy was estimated by contact angles. Thickness and density of the penetrating PTFE onto substrates depend on conditions of supercritical fluids such as pressure or temperature.