Synthesis of liquid EPDM having ultra-low-viscosity for curing at room temperature

A serial of liquid ethylene–propylene–diene rubber (EPDM) with 5-ethylidene-2-norbornene (ENB) contents of 2.0–6.5 mol% were synthesized by using VOCl₃ based catalysts. The obtained polymers have much low molecular weight with M_n = 4530–10180 g/mol (PDI = 3.5–7.1), consequently, these EPDMs without solvent have excellent flowability with the viscosity of 2198∼7460 mPa s at 25 °C. And the glass transition temperature as low as −85.9 °C was achieved. Impressively, these liquid EPDMs can be cured at 25 °C after 5 days. NMR analysis suggested that ethyl trichloroacetate acted as activator to chlorinate V(II) species to V(III), but also acted as polymer modifier to provide a chlorinated EPDM, which appeared to be essential for liquid EPDMs curing at low temperature. The dynamic water contact angle results demonstrated that the EPDMs had excellent wettability properties and surface properties. Thus, this work provided a facile way for one-pot synthesis of liquid EPDM containing functional group for curing at room temperature.