Triazine functionalized hydroxyl terminated polybutadiene polyurethane: Influence of triazine structure

Abstract

In the present work, we have examined the role of triazine based functional moieties namely cyanuric chloride (CYC), 2-chloro-4, 6-bis (dimethylamino)-1, 3, 5-triazine (CBDT) and 1-chloro-3, 5-diazido-2, 4, 6-triazine (CDT), which are attached to the terminal carbons of hydroxyl terminated polybutadiene (HTPB), on the structure-property of polyurethanes (PUs). Triazine attached HTPB, called as modified HTPB, was polymerized with varieties of diisocyanates and the resulting PUs were further cured at 70 °C for 5 days to prepare the free-standing elastic PU films. Thorough spectroscopic studies (FT-IR and 13C CP-MAS solid state NMR) of PU films could not identify any hydrogen bonding interactions between urethane bonds and triazine rings present in the soft segment (HTPB segment) of PU but revealed the presence of favorable electrostatic interaction between them because of the electron rich nature of triazine and the presence of polar substituents on the triazine ring. An in-depth small angle X-ray scattering study along with morphological study carried out by scanning electron microscopy confirmed that the interaction between urethane and triazine is the driving force for the formation of nanometer size mass fractals of hard segment domains (HSD) in the triazine attached HTPB-PU. Tensile strength and mechanical stability of modified HTPB-PU was found to be better than the native HTPB-PU owing to the formation of HSD. The current study also revealed the influence of nature and position of substituents in the triazine ring on the properties of modified PUs. The electron donating dimethyl amine groups of CBDT and segregation of PU chain were responsible for the strong photoluminescence of HTPB-CBDT-PU film compared to all other modified HTPB-PUs.