Preparation and Thermal Behavior of Fluorine-Containing Phenylmaleimides

Abstract

ABSTRACT:Fluorine content dependency on the melting point and thermal polymerization reactivity of fluorine-containing phenylmaleimides were investigated by differential scanning calorimetry and are discussed on the basis of molecular structure calculations. The syntheses of fluorine-containing maleimides were carried out by thermal dehydration. Their yields tended to be lower with increasing fluorine content. This was due to lowered nucleophilic reactivity of the amino group. The fluorine-containing maleimides tended to have a high melting point with increasing fluorine content. But symmetry in the chemical structure was a more important factor influencing the melting point. The thermal polymerization temperature of double bonds became higher with increasing fluorine content. This thermal polymerization reactivity could be explained from results of molecular structure calculations. The decreased thermal polymerizatio'n reactivity of fluorine-containing maleimides could be attributed to molecular stabilization or the difficulty of activated biradical formation as shown by MNDO or MM method calculations. This is in agreement with that of fluorine-containing bismaleimides.KEY WORDS Maleimide / Fluoro-Containing / Melting Point/ Polymerization Reactivity / MNDO / The maleimide structure has been utilized to produce thermally stable polymers. For example, bismaleimide resin provides a thermoset product which has been applied in a wide range of composite materials. 1 -3 The unsaturated double bonds of maleimide rings can thermally polymerize without the formation of volatile by-products which may cause voids. On this point, they differ from other condensation-type polyimides. Therefore, the thermal polymerization reactivity of double bonds of maleimide has been investigated and maleimide compounds have been widely used in the electronics industry. 4 -6 Among them, fluorinecontaining compounds have several good properties which are thought suited for electronics materials. These are a low dielectric constant, excellent thermal stability, and high flame retardancy. 7 In general, a fluorine substituent might lower thermal polymerization reactivity of double bonds of maleimide due to its electron-withdrawing effect. 8 • 9 Thus investigation of reactivity of fluorine-containing maleimides is of interest. The thermal properties, melting point, and polymerization temperature, of fluorine-containing bismaleimides have been investigated. 7 These bismaleimides have flexible ether groups and a long phenoxy chain within a monomer structure. Therefore, the cured product has good mechanical properties such as high flexural strength and elongation. 10 Moreover, the fluorine-containing compound has good electrical and thermal properties and is well suitable for electronics materials. It would be of interest to investigate the fluorine introducing dependency on these thermal properties. The fluorine-containing phenylmaleimide structure was selected as the model compound for the analysis of the fluorine content dependence.

Synthesis and characterization of a novel fluorinated bismaleimide via a nucleophilic addition–elimination reaction and its polymeric networks

“…14 Several studies demonstrated the incorporation of uorine containing building blocks into bismaleimide materials can effectively reduce their dielectric constants (D k ) and moisture adsorption and modify their surface properties. 29,30 However, only limited uorinated bismaleimides were prepared due to the availability and cost of the uorinated building blocks for the synthesis of bismaleimides. 31,32 It encourages us to look for new uorinated building blocks and novel synthetic methods to effectively synthesize uorinated bismaleimides with the prospects of commercialization.…”

Use of fluorinated maleimide and telechelic bismaleimide for original hydrophobic and oleophobic polymerized networks

“…For example, bismaleimide resin provides a thermoset product that has been applied in a wide range of composite materials. [13][14][15][16][17] The unsaturated double bond of maleimide rings can thermally polymerize [18][19][20][21][22] without the formation of volatile by-products. In several reports, 19, [23][24][25][26][27] the efficient photoinitiated polymerization by excited state of maleimides and bismaleimides have been shown in numerous (acceptor; donor) pair combinations.…”