Synthesis of a Bisbenzylideneacetone-Containing Benzoxazine and Its Photo- and Thermally Cured Thermoset

Abstract

A bis(4-hydroxybenzylidene)acetone/aniline-based benzoxazine ( BHBA-a ) was prepared from a bisbenzylidene-containing bisphenol, bis(4-hydroxybenzylidene)acetone ( BHBA ), aniline, and paraformaldehyde through Mannich condensation in a cosolvent of toluene/ethanol (2:1, v/v). The structure of BHBA-a was successfully confirmed by Fourier transform infrared and 1 H and 13 C NMR spectra. According to the differential scanning calorimetry (DSC) thermogram of BHBA , an immediate exothermic peak after the melting peak was observed, suggesting that BHBA is thermally active. NMR data of thermally treated BHBA confirm that the immediate exothermic peak after melting of BHBA in the DSC thermogram is resulted from the curing of a double bond. UV and 1 H NMR spectra of BHBA-a show that the bisbenzylideneacetone moiety underwent dimerization through the [2π + 2π] cycloaddition. Therefore, two procedures were applied to cure BHBA-a . The first one was thermal curing of the double bond of bisbenzylideneacetone and oxazine moieties. The second one was photocuring of the bisbenzylideneacetone moiety, followed by thermal curing of the oxazine moiety. The thermal properties of thermosets were evaluated based on these two procedures. Thermosets of BHBA-a exhibit T g as high as 318 °C for curing procedure 1 and 342 °C for curing procedure 2. These values are much higher than that of a traditional bisphenol/aniline-based benzoxazine thermoset. We conclude that the thermal curing of the double bond of bisbenzylideneacetone and photodimerization of bisbenzylideneacetone contributes to the good thermal properties.

Photo-sensitive benzoxazine II: chalcone-containing benzoxazine and its photo and thermal-cured thermoset

“…7), P(BHP-a)-UV-240 exhibits a T g value as high as 328 C. The T g value of P(BHP-a)-UV-X is higher than that of P(BHP-a)-X, indicating that the BHP-a dimer, a tetrafunctional benzoxazine, contributes to a higher crosslinking density. Although the T g value of P(BHP-a)-X is slightly lower than that of P(BHBA-a)-X, 32 probably due to BHBA-a has one more unsaturated double bond than BHP-a, leading to a higher crosslinking density. However, the difference is small.…”

“…Recently, we have reported the synthesis of a bis(4hydroxybenzylidene)acetone/aniline-based benzoxazine (BHBA-a, n ¼ 1 in Scheme 1) and studied its photo-and thermally-curing behavior. 32 BHBA-was photo-cured to afford a tetrafunctional benzoxazine (BHBA-a dimer), and followed by thermal curing of the double bond and oxazine linkage. The resulting thermoset shows a T g value as high as 342 C was achieved.…”

“…To the best of our knowledge, no chalcone-containing benzoxazine has been reported in literature. Continuing other's and our effort in developing photo-sensitive benzoxazines, [28][29][30][31][32] we prepared a chalcone-containing benzoxazine, the 1,3-bis(4hydroxyphenyl) propanone/aniline/formaldehyde-based benzoxazine (BHP-a, n ¼ 0 in Scheme 1) and evaluated the properties of its thermosets. Solubility test shows that the double bond of chalcone is thermally reactive.…”

“…DMA thermograms of P(BHP-a)-UV-X. g values of (a) P(BHP-a)-X and P(BHBP-a)-X32 (b) P(BHP-a)-UV-X and P(BHBA-a)-UV-X. 32 37850 | RSC Adv., 2017, 7, 37844-37851 This journal is © The Royal Society of Chemistry 2017 RSC Advances Paper Open Access Article.…”

Novel Linear Bis-Crown Receptors with Cross-Conjugated and Conjugated Central Cores

“…[16][17][18][19][20][21][22] Recently, cross-conjugated dienones with pyridine substituents have been used as ligands to produce discrete and polymeric coordination compounds. [23][24][25][26] Thus, it has been possible to produce discrete dimers based on cyclopentanone-based ligands, [23] one-dimensional coordination polymers, in the case of cyclohexanone-based ligands, [24], [27] and two-dimensional coordination polymers using piperidones-4.…”