Tuning morphology of Siloxane Bond-based Polybenzoxazines by controlling the sol-gel and curing processes

A. FORCHETTI; S. BORTOLATO; D. ESTENOZ; M. SPONTÓN

POLYMER ENGINEERING AND SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 2021

0032-3888

Novel polybenzoxazine/polysilsesquioxane nanocomposites were synthesized withuniform and reproducible structural morphology, high Tg, and good thermal stability.Polysilsesquioxane was oriented in a nanometer-size lamellar structure. Benzoxazinemonomer based on silane (BA-3aptms) was synthesized by reaction between bisphenolA, 3-(trimethoxysilyl)propylamine, and paraformaldehyde in a 1:2:4 molar ratio. Fourexperimental conditions of the two stage sol-gel process for polysilsesquioxane werestudied, and their effect on the material characteristics investigated. In the first stage,hydrolysis was favored, while the second stage mostly consisted of condensation. Thereaction condition with the longest hydrolysis time allowed the increase of theconcentration of silanol units and the selective condensation, favoring the formation of ahigher amount of cage-like cyclic structures. In addition, this experimental procedurewas well controlled so that the sol-gel and oxazine-ring opening reactions wereextremely reproducible from batch to batch. All processes were monitored by FourierTransform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) andDynamic Mechanical Thermal Analysis (DMTA), Scanning Electron and TransmissionElectron Microscopies (SEM and TEM), and X-Ray Diffraction. A chemometricapproach based on a multivariate curve resolution model was applied to the FTIRspectra, which allowed the identification of four reaction components associated withthe sol-gel and the curing processes.