Synthesis and characterization of semi-conductive, thermally stable imine polymers containing methyl silane group

Abstract

A series of Schiff bases were synthesized by condensation reaction of 3-aminopropyl(diethoxy)methylsilane with 3-hydroxybenzaldehyde and 4-hydroxy benzaldehyde compounds. Poly(imine)s were synthesized from Schiff bases by oxidative polycondensation. 2-Hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde and 2-hydroxy-1-naphthaldehyde were oxidatively polymerized using sodium hypochlorite (NaOCl) as oxidant, then poly(imine)s were grafted by adding 3-aminopropyl (diethoxy)methylsilane. Solubility tests of the synthesized Schiff bases and polymers were performed to determine the study conditions. All compounds were characterized by FT-IR, UV–Vis, 1H-NMR, 13C-NMR, CV and XPS analyses. Thermal properties of the synthesized compounds were determined using TG, DTA and DSC techniques. DMA analyses of polymers were performed to examine their T g values. The number-average molecular weight (M n ), weight average molecular weight (M w ) and polydispersity index (PDI) values of the synthesized compounds were determined by size exclusion chromatography. Photoluminescence (PL) properties of the synthesized compounds were determined in DMSO. Fluorescence measurements were carried out to obtain the maximum PL intensities. The cyclic voltammetry was an effective method to explore electrochemical ( $$E_{\text{g}}^{'}$$ ) band gaps of the polymers. Four-point collinear probe was used to determine the electrical conductivities of both doped and undoped states of the synthesized polymers with respect to doping time with iodine. Combined with the good thermal stability, the morphologic properties of the polymers were illustrated using scanning electron microscopy images at different amplifications. The result of this study revealed that polysiloxanes containing imine linkages were crucial for π-conjugated polymers whose electronic composition and properties could be adjusted by side group. The highest conductivity was obtained for P4 polymerized using o-vanillin and 3-aminopropyl(diethoxy)methylsilane.