Highly Active Copolymerization of Ethylene and N-Acetyl-O-(ω-Alkenyl)-l-Tyrosine Ethyl Esters Catalyzed by Titanium...

A series of N-acetyl-O-(ω-alkenyl)-l-tyrosine ethyl esters were synthesized by the reaction of vinyl bromides (4-bromo-1-butene, 6-bromo-1-hexene, 8-bromo-1-octene and 10-bromo-1-decene) with N-acetyl-l-tyrosine ethyl ester. ¹H NMR, elemental analysis, FT-IR, and mass spectra were performed for these N-acetyl-O-(ω-alkenyl)-l-tyrosine ethyl esters. The novel titanium complex can catalyze the copolymerization of ethylene and N-acetyl-O-(ω-alkenyl)-l-tyrosine ethyl esters efficiently and the highest catalytic activity was up to 6.86 × 10⁴ gP·(molTi)^-1·h^-1. The structures and properties of the obtained copolymers were characterized by FT-IR, (¹H)¹³C NMR, GPC, DSC, and water contact angle. The results indicated that the obtained copolymers had a uniformly high average molecular weight of 2.85 × 10⁵ g·mol^-1 and a high incorporation ratio of N-acetyl-O-(but-3-enyl)-l-tyrosine ethyl ester of 2.65 mol % within the copolymer chain. The units of the comonomer were isolated within the copolymer chains. The insertion of the polar comonomer into a copolymer chain can effectively improve the hydrophilicity of a copolymer.