Studies of the moisture-sensitive shape memory effect of pyridine-containing polyurethanes

Shape memory polymers have been much researched in recent years. In the work reported, moisture-sensitive shape memory effects (SMEs) of novel pyridine-containing shape memory polyurethanes (Py-SMPUs) were investigated systematically. The results show that the strain recovery start immersion time (t(s)), strain recovery immersion time (t(r)) and final strain recovery immersion time (t(e)) are prolonged with a decrease of relative humidity as well as a decrease of temperature. The final strain recovery decreases with a decrease of relative humidity as well as an increase of temperature. The key component affecting the moisture-sensitive SME is the N,N-bis(2-hydroxyethyl)isonicotinamide (BINA) unit. The lower limit of BINA content for Py-SMPUs to exhibit a good moisture-sensitive SME is 30 wt%. The addition of diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO) enhances the moisture-sensitive shape recovery. The final shape recovery decreases with a decrease of BINA content or an increase of MDIBDO content. In addition, t(s), t(r) and t(e) become shorter in the Py-SMPUs with higher BINA content or with lower MDI-BDO content. (C) 2011 Society of Chemical Industry