Synthesis Of N-Cyclohexylmaleimide And Its Copolymerization With Vinyl Monomers

N-cyclohexylmaleimide(CHMI) was synthesized through the dehydration reaction of N-cyclohexylmaleamic acid (CHMA) catalyzed by concentrated sulfuric acid/ triethylamine catalyst in o-xylene/toluene (50/50 v/v) mixed solvent at reflux temperature (about 125℃). Then, the radical copolymerization of cyclohexene (CH, M1) and CHMI (M2) and the atom transfer radical copolymerization of hydroxylpropyl methacrylate (HPMA, M1) and CHMI (M2) were investigated. The main contents were as follows: CHMI was synthesized through two-stages process. Firstly, CHMA was prepared through the reaction of maleic anhydride and cyclohexylamine, then the dehydration of CHMA catalyzed by sulfuric acid/triethylamine catalyst was conducted for 6 h in o-xylene/toluene (50/50 v/v) mixed solvent at reflux temperature (about 125℃). The yield of crude CHMI based on cyclohexylamine was 95 wt% under optimal synthesis conditions. The radical copolymerization of CH (M1) and CHMI (M2) was carried out with 2,2'-azobis(isobutyronitrile) as an initiator in various solvents at 55℃. The charge–transfer complexs between comonomers do not exist in this polymerization system as determined by 1H-NMR method. The copolymerization of CH with CHMI in chloroform, dioxane and benzene proceeded in a homogeneous system to give an alternating copolymer when the monomer of CH was over 40 mol% in the feed. It was found that the initial rate of the copolymerization (Rp), as well as the number-average molecular weight of copolymers, were dependent on the monomer composition and was at maximum at about 30 mol% of CH in the feed. The effects of solvents on the R_p and reactivity ratios were also investigated in this copolymerization system. The copolymerization in dioxane produced a higher Rp than that in chloroform and benzene, and the monomer reactivity ratios were found to be r1 = 0, r2 = 0.032 in chloroform; r1 = 0, r2 = 0.065 in benzene and r1 = 0, r2 = 0.14 in dioxane, respectively. The overall energy of activation, Ea, was found to be 118 kJ/mol by using of Arrhenius equation. In addition, a kinetic treatment based on this mechanistic model was used to quantitatively estimate the k21/k12 value, which was found to be 2.38. The copolymerization of CHMI with HPMA was performed by atom transfer radical polymerization (ATRP) using benzyl chloride as initiator and CuCl/ bipyridine as catalyst in anisole at 130℃. Copolymers with narrow molecular weight distribution (Mw/Mn =1.16~1.30) were prepared. The effects of comonomer composition, initiator, solvents and temperature on the ATRP were investigated. The copolymer was characterized by 1H-NMR spectroscopy.