Preparation of the polymerizable novel high refractive index hybrid carbazole-based polysiloxane oligomers by a sol–gel condensation reaction

In this paper, a series of novel carbazole-based polysiloxane oligomers: P(CzVinyl11Siloxane2), P(CzVinyl21Siloxane2), and P(CzVinyl11Siloxane3) with high refractive index (RI) containing the linear and/ or branched structures with vinyl and carbazole reactive moieties have been presented to the literature for optoelectronic applications. The polysiloxane oligomers were synthesized by an acid-catalyzed sol–gel condensation reaction of alkoxysilane monomers (carbazole-dimethoxysilane (Cz-2SiOCH₃) and vinyl-(di- or tri-methoxy)silanes (VMDMS or VTMS)) in the presence of trimethylmethoxysilane (SiMe) after a photoinitiated thiol-ene reaction was performed to obtain the compound Cz-2SiOCH₃. The structural confirmations were made using FT-IR, ¹H NMR, and ¹³C NMR spectroscopies. In addition, a ²⁹Si NMR study was performed to elucidate the nature of the siloxane structure of P(CzVinyl11Siloxane2). The refractive indices of the polysiloxane oligomers were between 1.6028 and 1.5923 as high values by varying the linear or branched structures. DSC analyzes revealed that the glass transition temperatures of P(CzVinyl11Siloxane2), P(CzVinyl21Siloxane2), and P(CzVinyl11Siloxane3) were -11 °C, -5 °C and -39 °C, respectively. Then, the polysiloxane oligomers were photopolymerized and their structural changes were observed by spectroscopic techniques. The photopolymerized polysiloxane oligomers with maintained and/ or enhanced refractive index values (between 1.6132 and 1.5719) showed very good transparency between 86.11% and 81.33% at 600 nm by the spin coating films. The novel carbazole-based polysiloxane oligomers would be useful chemical products or intermediates for the development of optical materials applied in optoelectronic devices.