Synthesis of branched benzoxazine monomers with high molecular mass, wide processing window, and properties of corresponding polybenzoxazines

Abstract

Four cyclotriphosphazene-based benzoxazine monomers (I, II, III, and IV) with relatively high molecular weight were synthesized by a nucleophilic substitution reaction, and their chemical structures were confirmed by 1 H-NMR and 31 P-NMR. A new term, oxazine value (OV, similar to epoxy value), was first proposed to explain the structure-property relationship of the cured polymers. The polymerization behaviors of the four monomers were studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. The maximum exothermic peaks of the four monomers are in the range 244-248 8C. All monomers possess a wide processing window despite their high molecular weight. The thermal stability, glass-transition temperature (T g ), and mechanical properties of each cured polymer were studied by thermogravimetric analysis and dynamic mechanical thermal analysis. The char yield at 850 8C, T g , and storage moduli of PIV (polybenzoxazine obtained from monomer IV) are 60.0%, 218 8C, and 9.0 GPa, respectively. The surface property and humidity absorption character of the cured polybenzoxazines were also studied. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44453.

Low melting point, high thermal stable branched benzoxazines resin derived from mixed-substituted phosphazene core

“…Six monomers were prepared according to the reported procedure [57]. The reaction details and chemical structure of six branched monomers with phosphazene core were presented in Figure 1 (12.72 g, 92 mmol, 8 eq) and acetonitrile (150 ml) were charged into a three-necked 500 ml round-bottom flask with vigorous agitation under ice-water bath at 0°C, then a calculated amount of HO-BOZ (5.26 g, 23 mmol, 2 eq) dissolved in 100 ml acetonitrile was added dropwise into the suspension.…”

“…Undoubtedly, fluorinated benzoxazines have attracted many attentions and gradually become a research focus [51][52][53]. Recently, our group focused on preparing organicinorganic hybrid polybenzoxazines based on cyclotriphosphazene core, and this kind of resins exhibited excellent thermal stability and easy preparation [54][55][56][57]. Though these monomers have higher molecular weights (>1490 g/mol) compared that with traditithe onal bisphenol-A based benzoxazine monomer, but some of them showed relatively low melting point (32-84°C) [57] and have the potential to be used as a matrix resin for composite preparation.…”

“…Recently, our group focused on preparing organicinorganic hybrid polybenzoxazines based on cyclotriphosphazene core, and this kind of resins exhibited excellent thermal stability and easy preparation [54][55][56][57]. Though these monomers have higher molecular weights (>1490 g/mol) compared that with traditithe onal bisphenol-A based benzoxazine monomer, but some of them showed relatively low melting point (32-84°C) [57] and have the potential to be used as a matrix resin for composite preparation. With the aid of high molecular design flexibility of phosphazene-based benzoxazine, we try to introduce fluorine-containing high polar group, such as m-CF 3 PhOH/p-CF 3 PhOH, into cyclotriphosphazene core to prepare mixed-substituted phosphazenebased benzoxazine derivatives to obtain benzoxazine monomers with a low melting point or even liquidlike monomers.…”

Curing reaction mechanism and heat resistance properties of hexa‐(4‐carboxyl‐phenoxy)‐cyclotriphosphazene/bisphenol A aniline benzoxazine blends

“…Therefore, many benzoxazine monomers that contain inorganic heteroatoms, such as Si, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), and Polyhedral oligomeric silsesquioxanes (POSS), have been synthesized and researched, of which cyclotriphosphazene (CP) derivatives are special. They are typical organic–inorganic compounds, in which the organic structures react with other kinds of resin and the inorganic parts provide excellent thermal stability . New benzoxazines containing CP have been well documented .…”

Design of thermosetting polymeric systems based on benzoxazines modified with maleic anhydride

“…Polybenzoxazines are a new type of thermosetting materials that have become of great interest due to their improved properties compared to traditional phenolic systems, such as absence of byproducts during the curing reaction and low viscosity of their monomers . In addition, these polymers offer a large number of attractive properties, including high glass transition temperature ( T g ), low dielectric constant, and volume contraction upon curing, chemical and dimensional stability, flame resistance, and relatively low cost .…”