Novel Si‐Based Chain Transfer Agents for LDPE Molecular Architecture Control

In this work, we present a new class of silane chain‐transfer agents (CTAs) for the molecular weight and the molecular weight distribution control during the production of low‐density polyethylene (LDPE). These silanes exhibit a wide range of chain‐transfer propensity as measured by their C s values (the ratio of the rate coefficient for hydrogen abstraction and ethylene propagation, k h / k p ) with the best performers being tris(trimethylsilyl)silane ( C s = 16.0) and trimethylsilylsilane ( C s = 15.7). Density functional theory (DFT) calculations were used to estimate the C s values. The quantum chemical calculations were validated by pilot‐plant experiments for triethylsilane ( C s = 0.22) and tris(trimethylsilyl)silane ( C s = 36.5). Given the expected variability in the pilot‐plant data, an excellent agreement between theory and experiment was achieved. Furthermore, a model utilizing the DFT calculated Mulliken charge on the silicon atom to predict the C s value was developed to facilitate silane screening in the future.