New polyaspartic ester (PAE) chain extender named PAE-f was prepared via two steps of Michael addition reactions:(1) Michael addition reaction between 4,4’-methylenebis(2-methyl cyclohexyl amine) (Laromin C260) and excessive dialkyl maleates（DEF）; (2) The Michael addition reaction of the residual dialkyl maleates of step (1) with polyester polyamine Jeffamine D230. The two-steps method proposed could reduce the reaction time in comparison with the current one step Michael addition reaction method, thus satisfying the industrialized production. New PAE based polyureas were synthesized by reacting the PAE-f chain extender with aliphatic polyisocyanates 4,4’-diisocyanato dicyclohexylmethane (H12MDI) / polyester polyamine Jeffamine D2000 prepolymer at room temperature. FT-IR and GPC were employed to characterize the new PAE prepared, and the morphology, molecular weight distribution and mechanical properties of the prepared PAE based polyureas were investigated by means of FT-IR and GPC. The FT-IR results indicated that the hydrogen bonding degree of amidogen groups in hard segments of the prepared polyureas were high, the length of hydrogen bonding were 0.305nm～0.306nm. The GPC experimental results show that the weight average molecular weight of the PAE-f based polyureas were 4.95×104～6.05×104,Mw/Mn were 1.65～1.97, the molecular weight distribution were relatively narrow. The mechanical properties demonstrated that the tensile strength were 14.7～22.5MPa, Elongation at break were 306～511%, Yang’s modulus were 67～127MPa, Shore A hardness were 64～83. The mechanical properties confirmed that the polyureas based on PAE-f were kinds of elastomeric materials with satisfied flexibility, strength, module and hardness.
Helical Polycarbenes Bearing D-Prolinol Ester Pendants: An Efficient Catalyst for Asymmetric Michael Addition Reaction
