Various polycarbonate graft copolymers via diels-alder click reaction

In this work, we used Diels-Alder click reaction for the preparation of various types of aliphatic polycarbonates (PCs). We first prepared a novel anthracene-functionalized cyclic carbonate monomer, anthracen-9-ylmethyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (2), followed by ring-opening polymerization of this monomer to prepare PC with pendant anthracene groups (PC-anthracene) using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)/1-(3,5- bis(trifloromethyl)phenyl)-3-cyclohexylthiourea (TU) as the catalyst and benzyl alcohol as the initiator in CH ₂Cl ₂ at room temperature. Subsequently, the resulting PC-anthracene (M _n,TDGPC = 6000 g/mol, M _w/M _n = 1.22) was grafted with a linear α-furan protected-maleimide terminated-poly(methyl methacrylate) (PMMA-MI) (M _n,GPC = 3100 g/mol, M _w/M _n = 1.31), or poly(ethylene glycol) (PEG-MI) (M _n,GPC = 550 g/mol, M _w/M _n = 1.09), or a mixture of PMMA-MI and PEG-MI to yield well-defined PC graft or hetero graft copolymers, PC-g-PMMA (M _n,TDGPC = 59000 g/mol, M _w/M _n = 1.22) or PC-g-PEG, or PC-g-(PMMA)-co-PC-g-(PEG) (M _n,TDGPC = 39900 g/mol, M _w/M _n = 1.16), respectively, using Diels-Alder click reaction in toluene at 110°C. The Diels-Alder grafting efficiencies were found to be over 97% using UV spectroscopy. Moreover, the structural analyses and the molecular weights of resulting graft copolymers were determined via ¹H NMR and triple detection GPC (TD-GPC), respectively.