End- Capping Modification of Low Molecular Weight Polyisoprene with Alkoxy Silicon

The low molecular weight polyisoprene (LPI) obtained by anionic polymerization was end-capped with 3-chloropropyl alkoxysilane. The conditions for this end-capping modification were investigated. The structure of LPI terminated with alkoxysilane was characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Additionally, the end-capping ratios of the modified products were determined from ¹H-NMR hydrogen spectra. Results indicated that the reaction occurred at the end of the molecule, and had little effect on the microstructure, glass transition temperature, or heat resistance of the product. However, it led to a slight decrease in the number average molecular weight and an increase in the molecular weight distribution index. The end-capping ratio increased with the increase of termination temperature, and decreased significantly with the increase of the amount of 3-chloropropyl alkoxysilane. When the termination was conducted at 50 ℃ with an equivalent amount of terminator to initiator, the end-capping ratio reached 91.35%.