Which factor is likely to increase the molecular weight of a polymer during its synthesis?

During condensation polymerization, the molecular weight rises when the by‑product (usually water or alcohol) is continuously removed from the reaction mixture. Removing this small molecule drives the equilibrium toward the formation of more covalent bonds, allowing chains to grow longer. If the by‑product remains in the system, it can reverse the reaction and shorten chains. For example, in the synthesis of polyesters, a Dean–Stark trap is used to pull water out, leading to higher‑molecular‑weight polymers. Thus, efficient removal of the small molecule by‑product is a key factor that increases polymer molecular weight.