Flexible polybenzoxazine thermosets with high glass transition temperatures and low surface free energies

Abstract

Four main-chain type polybenzoxazine precursors were synthesized from the Mannich-type polycondensation of biphenol A, paraformaldehyde, and four typical aromatic diamines: 1,4-phenylenediamine, 4,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl ether, and 2,2-bis[4-(4-aminophenoxy)phenyl] propane. The solvent effect on the polycondensation was examined. We found that polybenzoxazine precursors prepared in toluene/ethanol exhibit higher purity, higher molecular weight, and lead to better thermal properties after curing than those prepared in chloroform, as recommended by Takeichi's group (T. Takeichi et al., Polymer, 2005, 46, 12172). The cured polybenzoxazine films prepared by these polybenzoxazine precursors display unusual flexibility, extremely high T-g, and low surface energy. They show T-g values as high as 272-353 degrees C (DMA data), coefficients of thermal expansion as low as 39-49 ppm/degrees C, contact angles as high as 100-102 degrees, and surface energy as low as 17.7-24.5 mJ m(-2)

Synthesis of 9,9‐bis(4‐aminophenyl)fluorene‐based benzoxazine and properties of its high‐performance thermoset

“…Note that a network will be formed because diamine and formaldehyde are tetrafunctional and difunctional, respectively. In our previous work involved with the preparation of diamine/bisphenol A/formaldehydebased polybenzoxazines, 36 we proposed that competition between R 1 and R 2 plays a key role in polybenzoxazine synthesis. If R 1 ) R 2 , gelation will occur.…”

Thiol reactive polybenzoxazine precursors: A novel route to functional polymers by thiol-oxazine chemistry

“…Thus, main chain polybenzoxazine precursor was synthesized according to the monomer synthesis procedure (Scheme 3). In order to prevent gelation, toluene:methanol (2:1, v:v) mixture was used as solvent [45]. The polymer (PBZ) was obtained as M n : 3000 Da.…”

Thermally curable main-chain benzoxazine prepolymers via polycondensation route

“…However, in the case of toluene and 1,4-dioxane instead of soluble polybenzoxazine precursors only gels were formed. Moreover, using toluene/ethanol mixtures as solvent resulted in soluble polymers in high yields with molecular weights as high as 24,000 Da [34]. Notably, the cross-linked polybenzoxazine films from the high molecular weight precursors obtained by using this method exhibited much higher toughness compared to the cured film from typical low molecular weight monomeric benzoxazines.…”

“…Thus, the resultant resin may present properties that are the combination of thermoplastic and thermosetting polymers. A wide range of chemistries such as polyesterification [30,31], Mannich type condensation using difunctional phenols or amines [32][33][34][35], coupling reactions [36,37], Huisgen type click reaction [38,39] can be utilized for the synthesis of new curable precursors. Obviously, each route would reflect the characteristics of the polymer formed and modify the properties of the resulting polybenzoxazines for specific applications.…”