Crosslinked polyamide based on main-chain type polybenzoxazines derived from a primary amine-functionalized benzoxazine monomer

Reaction-Induced Liquid Crystalline Polybenzoxazine Bearing Aromatic Amide Side Branches

In this study, a nematic phase structure is incorporated into polybenzoxazine to increase its thermal conductivity. A simple route for the synthesis of a thermally conductive polybenzoxazine containing liquid crystalline (LC) structure by grafting oligomeric p-sulfophenylene-terephthalamide (PSTA) is offered. Benzoxazine monomer of pHBA-da is synthesized via Mannich reaction of p-hydroxy benzoic acid, p-formaldehyde, and dodecyl amine. After ring-opening polymerization, the oligomer benzoxazine of OBZ─COOH is obtained. The OBZ─COOH/PSTA mixture is prepared by mixing PSTA with OBZ─COOH. Afterward, the grafted copolymer is named OBZ─PSTA copolymer. The liquid crystalline behavior of OBZ─COOH/PSTA is studied by polarized optical microscopy and small angle X-ray scattering analysis. The results show that the OBZ─PSTA forms the LC structure during isothermal and non-isothermal curing. The LC structure displays a floral textured nematic phase. The phase formation is induced by an amidation reaction. Due to the grafts of LC PSTA, the thermal conductivity of OBZ─PSTA is 0.296 W m-1 K-1 , which is 26% greater than OBZ─COOH. The glass transition temperature (Tg ) of OBZ─PSTA is 241 °C. The 5% (Td5 ) and 10% weight loss temperatures (Td10 ) of OBZ─PSTA are 346 and 362 °C, respectively.

In(NO3)3 catalyzed curing reaction of benzoxazine

Benzoxazine is a new kind of thermoset resin with excellent properties, but it suffers from high curing temperature and low char yield in the presence of catalyst without halogen. In(NO3)3 was herein used for the first time to efficiently catalyze the curing reaction of benzoxazine and to elevate the char yield at 800°C. The reaction of benzoxazine was catalyzed by In(NO3)3 after stirring at 35°C for 300 min, and the initial curing temperature decreased to 151°C. Polybenzoxazine/In(NO3)3 showed higher thermal stability and char yield at 800°C (increased by 7.5%) compared with those of polybenzoxazine. The possible pathway of coordination bonding between In3+ and benzoxazine was proposed. In the cross-linking process, two different structures, that is, the N, O-acetal bridge structure and arylamine Mannich bridge structure formed at 35°C, both existed, which ultimately affected the thermal stability of the cured product.

One-Pot Synthesis of Amide-Functional Main-Chain Polybenzoxazine Precursors

Main-chain polybenzoxazines containing amide linkages were successfully prepared in one pot. Three different polymers were synthesized by reacting 3,4-dihydrocoumarine (DHC) and paraformaldehyde with 1,3-diaminopropane or 1,6-diaminohexane or Jeffamine ED-900. The one-pot reaction proceeded through the combination of the ring-opening of DHC with amines, and subsequent Mannich and ring-closure reactions occurring in a cascading manner. The obtained polymer from Jeffamine exhibited good film-forming properties, and free-standing flexible films were easily solvent- casted on Teflon plates. All polymeric precursors were characterized by spectroscopic analysis, and their curing behavior and thermal stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Coumarines as masked phenols for amide functional benzoxazines

Benzoxazines with amide linkages were successfully prepared from 3,4-dihydrocoumarine using either one-pot or stepwise pathways.

Synthesis and properties of main-chain oligomeric benzoxazine precursor containing cyclotriphosphazene units

A linear oligobenzoxazine precursor with cyclotriphosphazene ring was prepared through the Schiff base route. The resulting polymers showed higher molecular weight and better thermal stability than those from the traditional Mannich polycondensation method. The oligomeric benzoxazine precursor can form a high-quality transparent yellow film; however, it was fragile after being cured. In order to identify the effect of end groups on the cured polymer, an aniline-capped polymer was prepared by the same Schiff base method and then was changed into a benzoxazine end group. The results indicated that the uncapped polymer exhibited higher stability than the capped polymer. This can be ascribed to different chemical structures resulting from different end groups.

Polymer alloys of high-molecular-weight benzoxazine and epoxy resin

Novel polymer alloys were prepared by curing the mixture of a high-molecular-weight benzoxazine (B-oda) that was synthesized from 4,4′-oxydianiline (oda), bisphenol-A, and formaldehyde and a typical epoxy resin prepolymer, epoxy-terminated copolymer of bisphenol-A and epichlorohydrin, up to 240°C. It was confirmed by differential scanning calorimetric and infrared (IR) investigations that the novel alloys had ether linkages that was formed by the reaction between the phenolic hydroxyl groups formed from the thermal ring-opening polymerization of B-oda and the epoxy groups of the epoxy resin. The properties of the alloy films were compared with polybenzoxazine (PB-oda), the pristine polybenzoxazine obtained by curing B-oda without the epoxy resin. The alloy films were more flexible and were found to have higher glass transition temperatures ( Tgs) from the dynamic mechanical analyses. From the IR analyses of the films, the polymer alloys were found to have higher amount of intermolecular hydrogen bonding compared with the pristine PB-oda. It was suggested that this increase of the hydrogen bonding was the cause of the higher Tgs of the polymer alloys.

Design of lamellar structured POSS/BPZ polybenzoxazine nanocomposites as a novel class of ultra low-k dielectric materials

A novel class of lamellar structured polyhedral oligomeric silsesquioxane/bisphenol Z (POSS/BPZ) polybenzoxazine (PBz) nanocomposites was successfully designed by a facile one-step copolymerization technique.

High performance crosslinked polyimide based on main-chain type polybenzoxazine

A novel approach has been developed to prepare thermosetting polyimides by incorporating benzoxazine structure as a repeating unit in the main chain. This method allows the crosslinked polyimide with excellent thermal and mechanical properties.

Preparation and properties of polymer alloys consisting of high-molecular-weight benzoxazine and bismaleimide

Novel polymer alloys were prepared by blending a high-molecular-weight benzoxazine (HMWB) and a typical bismaleimide (4,4′-bismaleimidodiphenyl methane (BMI)) followed by thermal treatment up to 240°C. It was confirmed by the infrared and differential scanning calorimetric analyses that the phenolic hydroxyl group formed by the ring-opening polymerization of HMWB reacted with the double bond of BMI, in addition to the chain polymerization of the double bond of BMI and the ring-opening polymerization of HMWB. This further cross-linking through the formation of ether linkage made the polymer alloy films much more tough and flexible than each homopolymer film. Moreover, viscoelastic analyses and thermogravimetric analyses of the polymer alloy films showed that glass transition temperature and thermal stability also increased by alloying.