Dynamic Urea Bond‐Mediated Polymerization for Solvent‐Free Low‐ <i>Ð</i> Linear Polyurethanes of Controlled Molar Mass: Hypothesis of Diffusion Control

Dynamic urea bond-mediated polymerization (DUBMP) has been employed for the synthesis of linear, branched, telechelic, and random-block polyurethanes (PUs) with low molar-mass dispersity relative to conventionally synthesized PUs (Đ < 1.5). However, reason improved control molar mass reduction in dispersity, promoted by DUBMP, not explained. In this paper, DUBMP linear PU based on low-molar-mass poly(ethylene glycol) (PEG) isophorone diisocyanate is studied comprehensively. The lower viscosity PEG-based allows reach high conversions (≈0.97) first time, while Đ vary substantially reaction conditions, despite yielding similar/equal conversion values. Both increase an temperature, or a amine/isocyanate ratio. Therefore, evidence suggests that provides diffusion due mobility longer chains associated isocyanate-deactivator-rich environment. An and/or decrease ratio, reduces control, leading higher values mass. Tuning conditions obtaining controlled (11 kDa ≤ Mw 42 kDa) 1.3 1.75.