Preparation of polysiloxane oligomers bearing benzoxazine side groups and tunable properties of their thermosets

Abstract

A new pathway for the preparation of polysiloxane oligomers bearing benzoxazine side groups were reported via the hydrolysis and co‐polycondensation of benzoxazinyl siloxane (SBZ) with dimethyldiethoxysilane (DEDMS). The structures of SBZ and oligomers were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The average molecular weights of the obtained oligomers were estimated from size exclusion chromatography and 1H‐NMR to be in the range of 2000–4000. The oligomers gave transparent films by casting in THF solution. The films were further thermally treated to produce crosslinked films via the ring opening polymerization of benzoxazine side group. The effects of siloxane content on polymerization behavior, glass transition temperature, and mechanical properties of the polybenzoxazine thermosets were investigated. Tensile test of the films revealed that the elongation at break increased with increasing siloxane content. The elongation at break of poly(I‐50) was up to 12.1%. Dynamic mechanical analysis of the thermosets showed that the Tgs were in the range of 119–165°C. Thermogravimetic analysis also revealed a better thermal stability as evidenced by the 5% weight loss temperatures in the range of 363–390°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40960.

An m‐phenylenediamine‐based benzoxazine with favorable processability and its high‐performance thermoset

“…However, the corresponding phenols or primary amines from which the abovementioned benzoxazines derived are mostly not common chemicals, therefore their widespread application is limited. Another effective approach is the incorporation of inert structural moieties like biphenyl, fluorine, naphthalene, sulfone, siloxane, and polyether to benzoxazines, which endows polybenzoxazines with desired high T g , high toughness, low surface energy or favorable processability. In this case, the high polymerization temperature is still a problem awaiting solution.…”

Preparation and characterization of benzoxazine based nanocomposites: Comprehensive study in curing kinetics and enhanced thermal stabilities

“…A variety of polymers, such as rubber, polycarbonate, poly (e‐caprolactone) (PCL), polyurethane (PU), and epoxy, have been used to improve processability of benzoxazine. Apart from polymer blends, the influence of the incorporation of nanofillers on properties of benzoxazine has been studied by a few groups . Huang et al .…”

Synthesis and characterization of poly(benzoxazine‐co‐siloxane) oligomers end‐capped with arylacetylene

“…Siloxane addition can significantly improve the toughness of the polybenzoxazines; however, the heat resistance of the material does not enhance necessarily. It should be noted that in most research regarding polysiloxane-modified benzoxazines [13][14][15][16][17][18][19][20][21][22][23] the focus is on the precursors of large-molecular-weight polybenzoxazines, [13][14][15][16][18][19][20][21][22][23] and there are relatively few studies on small molecular-weight benzoxazine oligomers. Although large-molecular-weight precursors have more advantages than low-molecular-weight precursors in terms of synthesis and mechanical properties, these resins tend to have a higher curing temperature [13,14,16] and poor processability, [13,14,16,[19][20][21][22] which limits the scope of their practical use.…”

“…It should be noted that in most research regarding polysiloxane-modified benzoxazines [13][14][15][16][17][18][19][20][21][22][23] the focus is on the precursors of large-molecular-weight polybenzoxazines, [13][14][15][16][18][19][20][21][22][23] and there are relatively few studies on small molecular-weight benzoxazine oligomers. Although large-molecular-weight precursors have more advantages than low-molecular-weight precursors in terms of synthesis and mechanical properties, these resins tend to have a higher curing temperature [13,14,16] and poor processability, [13,14,16,[19][20][21][22] which limits the scope of their practical use. It is, therefore, necessary to systematically investigate the effect of introducing siloxane on the properties of low-molecularweight benzoxazine oligomers, which possess good processability.…”