Synthesis Of N-substituted Maleimides And Its Polymerization

N-substituted maleimides are one kind of thermal improver which are developed recently. When copolymerized with common vinyl monomers, the resulting copolymers contain five-member planar rings in the chain, which hinder the rotation of the imides residues around the backbone chain of the macromolecules, resulting in a greater structural stiffness and a higher thermal stabilityThe synthesis and application of N-substituted maleimides are introduced using N-phenyl maleimide as an example. Also, progress on polymerization of N-substituted maleimides by free radical polymerization, anionic polymerization and coordination polymerization are reviewed.The monomers N-phenyl maleimide, N-benzyl maleimide, N-cyclohexyl maleimide, N- (p-hydroxyphenyl) maleimide, N- (p-carboxyphenyl) maleimide were prepared from maleid anhydride and the correspongding amine using acetic anhydride as dehydrator, sodium acetate as catalyst. The effects of reaction temperature and reaction time were basicly studied. The obtained monomers were characterized by FT-IR and H NMR methods.The copolymerizations of N-substituted maleimides with styrene were studied with toluene as solvent, azobisisobutyronitrile (AIBN) as initiator.The effects of polymerization time, polymerization temperature, monomer mixture composition, monomer concentration and initiator concentration on copolymerization of N-phenyl maleimide with styrene were investigated. The compositions of the two monomers in copolymers were close to 1:1 even at a high monomer conversion of about 60%, and did not change as the NPMI feed mole fraction varied from 10% to 90%. The copolymer was characterized by ¹³C nuclear magnetic resonance spectroscopy, showing that the copolymer possessed a nearly alternating structure. It was also vertifled by the obtained teactivity ratios of the two monomers r_NPMI=0.062, r^st=0.015. The thermal properties of the copolymers were also investigated. The copolymer showed good thermal stability with no obvious decomposition under 350℃. The initial thermal decomposition temperature was 380℃ and maximum thermal decomposition temperature 430℃. The copolymers exhibited a single glass transition temperature Tg at 230 ℃ reflecting their relatively homogeneous molecular structure.Also, the effects of polymerization temperature and polymerization time oncopolymerization of N- N-benzyl maleimide, N-cyclehexyl maleimide, N-(p-hydroxyphenyl) maleimide with styrene were studied. And the copolymers were characterized by FT-IR and HNMR methods.