The Design, Synthesis And Properties Of Polysiloxane With High Optical Performance

In this work, we use a two-step method to prepare the polysiloxane. Prepolymers with vinyland hydrogen groups are fabricated via co-hydrolysis/condensation and then crosslinkedpolysiloxane resin is prepared by hydrosilylation reaction at the presence of the platinum catalyst.We study the influence of concentration of catalyst, content of phenyl group and catalyst to theproperties of polysiloxane resin. The relationship between the structure and performance ofpolysiloxane is discussed via Nuclear Magnetic Resonance (NMR), Fourier Transform InfraredSpectroscopy (FTIR), Gel Permeation Chromatography (GPC) and etc.In this work, the effects of co-hydrolysis/condensation and curing on the refractive index,transparency are researched and we obtain the optimal parameters: the concentrations of acid are1wt%in system A and0.5wt%in system B, respectively. The content of phenyl group (Ph/Si)is0.9and the time of curing is an hour at every different temperature (80℃,120℃and150℃).Polysiloxane in three different systems is prepared in this work, the structure and propertiesof which are characterized and discussed. The NMR spectra show that the crosslinked network isformed in all systems and the vinyl and hydrogen groups for hydrosilylation reaction are existedin the prepolymers. The IR spectra indicated that the crosslink reaction between vinyl andhydrogen groups is taking place as the curing is running. Besides, the fact that residual vinylgroup is tested in curing product suggests cure is not fully accomplish. The GPC spectrademonstrate that the average moleculars of polysiloxane in three systems are all about1200andthe polysiloxane possesses a densely cross-linked network structure.The research of optical performance states clearly that the transmittance of all polysiloxaneis nearly or above99%and there is nearly no absorption in the visible range. The transparency isstill excellent after aging and decrease of transmittance is slight, which proves that the stabilityof products and the resistance to yellowing ability are both good. The refractive index ofpolysiloxane is all above1.52and the polysiloxane show outstanding optical performance. Thethermogravimetric analysis indicates that the as-prepared products always possess a goodthermal stability before300℃. In conclusion, the transparent densely crosslinked polysiloxane with high refractive indexand thermal stability is obtained, which is potential and promising application for electronicencapsulation, especially for high performance Light Emitting Diode (LED).