Both role of clay and LDH, as supports and nanofillers for syndiospecific styrene polymerization in the presence of vanadium-based Ziegler-Natta calalysts systems: structure and thermal stability

In this contribution, we report our investigations on the stereo-specific styrene polymerization in the presence of a homogeneous catalytic system formed by combining a Ziegler-Natta catalytic system based on vanadium oxychloride (VOCl3) and a methylaluminoxane cocatalyst (MAO). The reaction parameters, including the Al/V molar ratio and polymerization time, were systematically investigated and optimized with respect to polymer conversion, catalytic activity, and tacticity. At an Al/V molar ratio of 100, further increasing the polymerization time resulted in a higher conversion of syndiotactic polystyrene (sPS), reaching 96% with an average molecular weight of 2.50 × 106 g·mol−1. Subsequently, the polymerization reaction was conducted using heterogeneous catalytic systems, with organically modified Algerian clay (OAC) or layered double hydroxides (LDH), as catalytic supports. The influence of the nature of the support on the catalytic performance and the properties of polystyrene was investigated. The catalytic system exhibited syndiospecificity, and the conversion and stereoregularity were strongly dependent on the type of catalyst and the support. Notably, the presence of 5% OAC significantly increased the conversion rate to 85%, indicating superior catalyst activity.” The structure of the obtained polymers was examined by Fourier transform infrared spectroscopy (FTIR), wide angle X-ray scanning (WAXS), and scanning electron microscopy (SEM). Thermal properties were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Interestingly, the obtained results show that the OAC and LDH supports have both catalytic and nano-filler effects by enhancement of the polystyrene tacticity as well as its thermal degradation behavior.