Syafiqa Mohd Saleh, Ahmad Shalabi Md Sauri, Mohd Fazli Mohammat, Fatin Nur Amira Mohammad Hejemi, Mifzal Mohamad Nazrel, Karimah Kassim, Ahmad Zafir Romli, Putri Nur Arina Mohd Ariff, Ahmad Faiza Mohd, Noor Hidayah Pungot, Aimi Suhaily Saaidin, Agustono Wibowo, Mohamad Faizzudin Mat Piah, Jamali Basar
Polyisobutylene succinic anhydride (PIBSA) is an important intermediate for ashless dispersant additives used in lubricant formulations, where conversion and exo-selectivity strongly influence product performance. In this work, the thermal synthesis of PIBSA derived from highly reactive polyisobutylene (HR-PIB) 1300 and 2300 was systematically investigated using a full factorial experimental design to evaluate the effects of feed molar ratio, reaction temperature, and stirring rate on conversion and exo-PIBSA yield. Structural confirmation was performed using 1H NMR spectroscopy, gel permeation chromatography (GPC), and saponification value analysis. HR-PIB 1300 achieved conversions of 60-94%, while HR-PIB 2300 achieved conversions of 75-88% under the investigated conditions. A clear molecular-weight-dependent trade-off between conversion and exo-selectivity was observed. For PIBSA 1300, higher temperatures increased conversion but reduced selectivity, resulting in exo-PIBSA yields of 24-56%. In contrast, PIBSA 2300 achieved yields of up to 71%, highlighting the importance of mixing and mass-transfer effects in higher-viscosity systems. These findings demonstrate that optimal thermal maleation conditions are strongly dependent on polymer molecular weight and provide mechanistic insight for future optimization of industrial PIBSA production.