聚甲氧基二甲醚的合成及其物理化学性质表征

聚甲氧基二甲醚（H₃CO（CH₂O）_nCH₃， PODE_n或DMM_n， n ≥ 2）具有独特的物理化学性质；作为一种柴油添加剂，可以有效提高油品燃烧效率并达到节能减排的目的。首先合成了一系列聚合度n为2、3、4和5单一组分的聚甲氧基二甲醚，采用NMR、FT-IR、Raman和DFT计算等手段对每个聚甲氧基二甲醚单体的化学结构进行表征，并对其在298.15-323.15K温度的密度和黏度进行了测试。结果表明，聚甲氧基二甲醚的密度和黏度随着温度的升高而逐渐降低，随着聚合度的增加而逐渐升高。同时，聚甲氧基二甲醚PODE_n（n =2-5）的闪点和倾点以及溶解热和凝固热均随着聚合度的增加而提高。

Synthesis and physicochemical characterization of polyoxymethylene dimethyl ethers

Polyoxymethylene dimethyl ethers (H₃CO(CH₂O)_nCH₃, PODE_n or DMM_n, n ≥ 2) with unique physical and chemical properties are a potential additive for diesel fuels, which can effectively enhance the combustion efficiency and reduce the emission of pollutants. In this work, a series of pure PODE_n components (n=2-5) were synthesized from methylal and trioxymethylene and obtained with high purity through collaborative separation; their structure and properties were characterized by NMR, FT-IR, Raman, and DFT calculation and a detailed assignment of the expressions in the spectrogram to the various groups was performed. The density and viscosity of PODE_n were measured at 298.15-323.15 K. The results indicate that the density and viscosity of PODE_n decrease gradually with the increase of temperature. Meanwhile, with the increase in the number of -CH₂O- units (n) from 2 to 5, the density, viscosity, flash point, pour point, and the heat of fusion and solidification of PODE_n are all increased. These results are valuable for the practical synthesis and application of PODE_n.