Bismaleimide-4,4′-diphenylmethane Research Articles

Kinetics of Michael addition polymerizations of n,n′‐bismaleimide‐4,4′‐diphenylmethane with barbituric acid

AbstractWith the addition of sufficient hydroquinone to completely suppress the free radical polymerization, the kinetics of Michael addition polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) and barbituric acid (BTA) with BMI/BTA = 2/1 (mol/mol) in 1‐methyl‐2‐pyrrolidone was investigated independently. A mechanistic model was developed to adequately predict the polymerization kinetics before a critical conversion (ca. 60%), at which point the diffusion‐controlled polymer reactions started to predominate in the latter stage of polymerization. The Michael addition polymerization rate constants and activation energy in the temperature range 383–423 K were determined accordingly. Beyond the critical conversion, a relatively stationary limiting conversion (ca. 69%) independent of the reaction temperature was achieved. A diffusion‐controlled polymerization model taken from the literature satisfactorily predicted the limiting conversion data. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Kinetic and structural studies of the polymerization of N,N′‐bismaleimide‐4,4′‐diphenylmethane with barbituric acid

AbstractBoth the isothermal and non‐isothermal polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) with barbituric acid (BTA) were investigated by the differential scanning calorimeter. The experimental results showed that the polymerizations of BMI with BTA were governed by the competitive Michael addition reaction and free radical polymerization mechanisms. Furthermore, the contribution of free radical polymerization becomes more important when the mole fraction of BTA decreases. 1H NMR and 13C NMR measurements further support the coexistence of the Michael addition reaction and free radical polymerization mechanisms. A preliminary kinetic model that took into account the competitive Michael addition reaction and free radical polymerization mechanisms was developed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Effects of solvent basicity on free radical polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane initiated by barbituric acid

AbstractThe polymerizations of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) initiated by barbituric acid (BTA) carried out in a variety of solvents at 130°C were studied. The nitrogen‐containing cyclic solvents such as N‐methyl‐2‐pyrrolidinone acted as a catalyst to promote the formation of the three‐dimensional crosslinked network structure. By contrast, the polymerization in a cyclic solvent that did not contain nitrogen such as γ‐butyrolactone resulted in nil gel content. The higher the solvent basicity, the larger the amount of insoluble polymer species formed. The molar ratio of BTA to BMI also played an important role in the polymerizations. The resultant polymers, presumably having a hyper‐branched structure, exhibited much narrower molecular weight distributions than those prepared by conventional free radical polymerizations. The BMI polymerizations using BTA as the initiator could not be adequately described by conventional free radical polymerization mechanisms. A polymerization mechanism that took into account the generation of a ketone radical pair between BTA and BMI and the subsequent initiation, propagation and termination reactions was proposed. It was concluded that the nitrogen‐containing cyclic solvents were capable of participating in the ketone radical pair formation process, thereby increasing the extent of polymer crosslinking reactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermal properties and water sorption behaviors of epoxy and bismaleimide composites

In this work, we prepared epoxy/BMI composites by usingN,N′-bismaleimide-4,4′-diphenylmethane (BMI), epoxy resin (diglycidyl ether of bisphenol-A (DGEBA)), and 4,4’-diamino diphenyl methane (DDM). The thermal properties and water sorption behaviors of the epoxy and BMI composites were investigated. For the epoxy/ BMI composites, the glass transition and decomposition temperatures both increased with increasing BMI addition, which indicates the effect of BMI addition on improved thermal stability. The water sorption behaviors were gravimetrically measured as a function of humidity, temperature, and composition. The diffusion coefficient and water uptake decreased and the activation energy for water diffusion increased with increasing BMI content, indicating that the water sorption in epoxy resin, which causes reliability problems in electronic devices, can be diminished by BMI addition. The water sorption behaviors in the epoxy/BMI composites were interpreted in terms of their chemical and morphological structures.

Silica nanoparticles modified with vinyltriethoxysilane and their copolymerization with N,N′‐bismaleimide‐4,4′‐diphenylmethane

AbstractThe synthesis and characterization of the vinyltriethoxysilane‐modified silica nanoparticles were investigated. It was shown that the vinyltriethoxysilane molecules had been successfully grafted onto the silica nanoparticles. The native and silane‐modified silica dispersions in N‐methyl‐2‐pyrrolidone with the total solids contents within the range 1–6 wt % exhibited dramatically different flow behaviors. The polymerization of N,N′‐bismaleimide‐4,4′‐diphenylmethane (BMI) initiated by barbituric acid in the presence of the native or vinyltriethoxysilane‐modified silica nanoparticles were then carried out in γ‐butyrolactone (total solids content = 20%). The higher the level of silica, the better the thermal stability of the BMI/silane/silica composite particles. The silane‐modified silica particles significantly improved their dispersion capability within the continuous BMI oligomer matrix. Furthermore, the degree of dispersion of the vinyltriethoxysilane‐modified silica particles in the BMI oligomer matrix decreased with the weight percentage of silica based on total solids increased from 20 to 40 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: Sci 103: 3600–3608, 2007