Synthesis and Polymerization of Naphthoxazines Containing Furan Groups: An Approach to Novel Biobased and Flame-Resistant Thermosets

Davi Rabelo De Oliveira,Diego Lomonaco,Selma Elaine Mazzetto

doi:10.1155/2018/4201681

Davi Rabelo De Oliveira, Diego Lomonaco + Show 1 more

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https://doi.org/10.1155/2018/4201681

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Abstract

Naphthoxazines are a class of compounds with potential application in obtaining high-performance polymeric materials. Such application of these compounds, however, is still scarcely explored in the literature. Combined with the search for new high-performance materials, the development of biobased polymers has gained a lot of attention. In this sense, the inclusion of furan groups in polymers has been explored as a strategy that combines the search for high-performance materials with the search for the development of biobased materials. In this work, novel naphthoxazine monomers containing furan groups were synthetized. The syntheses were carried out in a single step, without the use of solvents and catalysts, obtaining the products in satisfactory yields and high purity. The naphthoxazines had their chemical structures completely characterized by FTIR, 1H NMR, and 13C NMR techniques. The thermal analyses (DSC and TGA) showed that all naphthoxazines exhibit exothermic typical polymerization events, making these compounds suitable for obtention of poly(naphthoxazines) resins, but suffer significant mass losses at temperatures below the onset polymerization temperature. In this way, a catalyst (1 mol% MgCl2) was used in order to allow the polymerization of the compounds before the mass loss events. The FTIR analysis showed strong evidences of the formation of poly(naphthoxazines), and TGA analyses showed that the resins have high thermal stability, with high flame resistance and self-extinguishing properties (LOI > 28), which makes these compounds attractive in the development of biobased and high-performance materials.

Highlights

The search for high-performance polymeric materials has attracted the attention of several research groups, which seek to develop new compounds with attractive characteristics, such as high thermal and mechanical resistance, especially for application in the microelectronics and aerospace industries [1].In this context, polymers derived from compounds containing 1,3-oxazinic rings arise as a relatively new class of high-performance thermosetting polymers
As far as it can be ascertained, the synthesis of the Naft-Fu-H and Naft-Fu-Fu compounds is not reported in the literature and even the Naft-H-Fu compound is reported in only one single work [25], where the thermal properties or polymerization behavior of this compound was not explored
The synthesis of Naft-Fu-H was conducted under microwave heating, with satisfactory yield (60%), in a few minutes (7 min), especially if compared to the syntheses of oxazinic compounds conducted under traditional heating described in literature, which normally require several hours of reaction, demonstrating the efficiency of this method in the synthesis of this type of compound, as already reported in previous studies [3]

Summary

Introduction

The search for high-performance polymeric materials has attracted the attention of several research groups, which seek to develop new compounds with attractive characteristics, such as high thermal and mechanical resistance, especially for application in the microelectronics and aerospace industries [1].In this context, polymers derived from compounds containing 1,3-oxazinic rings (six-membered heterocyclic containing nitrogen and oxygen heteroatoms) arise as a relatively new class of high-performance thermosetting polymers. In addition to the advantages of traditional phenolic polymers, such as high thermal resistance, dimensional stability, good electrical properties, flame retardancy, and low smoke generation, polyoxazines exhibit their own attractive characteristics, such as low moisture absorption, good chemical resistance, high glass transition temperature (Tg), low shrinkage, and improved mechanical and thermal properties compared to traditional phenolic polymers. They offer great flexibility of molecular design and do not generate by-products during their polymerization [2, 3]. These compounds have been investigated because of their potential application in a number of biological activities [5,6,7,8]

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