Styrylpyridine‐based epoxy resins: Synthesis and characterization

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Abstract
Polymers containing rigid aromatic structures in the chain backbone usually gave high thermal stability and good flammability resistance. Three glycidyl ethers of epoxy resins were prepared from 2,4‐di(p‐hydroxystyryl)pyridine (2,4‐DGESP), 2,6‐di‐(p‐hydroxystyryl)pyridine (2,6‐DGESP), and 2,4,6‐tri‐(p‐hydroxystyryl)pryidine (2,4,6‐TGESP) to study the relationships of structure to polymer degradation. To prepare a highly crosslinked material, trimethoxyboroxine (TMB) was used as the curing agent. The relative char yields of the three different resins, as measured by TGA, were 2,4‐DGESP ≈ 2,6‐DGESP > 2,4,6‐TGESP. The char yield of the cured 2,6‐DGESP varied with different amounts of the TMB curing agent, and was higher than the uncured 2,6‐DGESP. The oxygen index increased as a function of thermal curing time for the 2,6‐DGESP epoxy resin. An intermolecular Diels–Alder reaction with 2,6‐DGESP is proposed as a primary reaction during thermal curing.