Multi-maleimides bearing electron-donating chromophores: reversible fluorescence and aggregation behavior.

A((=))-D, [A((=))](2)-D and [A ((=))](3)-D multi-maleimides and multi-itaconimides bearing electron-donating chromophores display a strong fluorescence quenching due to an intramolecular charge-transfer interaction. The electron-accepting C=C bond plays a key role in the intramolecular quenching. For the isomerization of these multi-itaconimides and Michael additions of these multi-maleimides, their emission behavior is irreversible. For the Diels-Alder additions of these multi-maleimides, their emission behavior is reversible due to the reversible opening and closing of intramolecular charge-transfer pathway. Tris-maleimide TMPA peripherally modified with furfural alcohol displays not only reversible fluorescence behavior but also reversible aggregation behavior.

A convenient method for the synthesis of amine-terminated poly(ethylene oxide) and poly(epsilon-caprolactone).

A convenient synthetic route to prepare amine-terminated poly(ethylene oxide) (PEO) and poly(epsilon-caprolactone) (PCL) was described. The strategy involved two-step reactions, the condensation of hydroxyl-terminated PEO and PCL with N-benzyloxycarbonyl amino acid followed by the catalytic hydrogenation under mild conditions. NMR and GPC measurements indicated that the reactions proceeded nearly quantitatively. Amine-terminated PEO thus prepared was used to initiate the polymerization of alpha-(N(epsilon)-benzyloxycarbonyl-L-lysine) N-carboxy anhydride [lys(Z)-NCA], and the results confirmed that the reactivity of the amino group was high.