2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/168797A simple model of quintessential inflation with the modified exponential potential $e^{-αϕ} [A+(ϕ-ϕ_0)^2]$ is analyzed in the braneworld context. Considering reheating via instant preheating, we conclude that the model exhibits transient acceleration at late times for $0.96 \lesssim A α^2 \lesssim 1.26$ and $271 \lesssim ϕ_0 α\lesssim 273$, while permanent acceleration is obtained for $2.3\times10^{-8} \lesssim A α^2 \lesssim 0.98$ and $255 \lesssim ϕ_0 α\lesssim 273$. The steep parameter $α$ is constrained to be in the range $5.3 \lesssim α\lesssim 10.8$.4 pages, 2 figures, presented at the "seventh alexander friedmann international seminar on gravitation and cosmology"Astrophysicstext