Enhance the viscosity of polydimethylsiloxane by controlling the volume ratio of monomer and chain terminator

The production of polydimethylsiloxane (PDMS) as a vitreous substitute in Indonesia has been carried out. In our previous study, a good quality of low viscosity PDMS was well provided using a low-grade octamethylcyclotetrasiloxane (D4) monomer. We also reported that a new type of PDMS with medium viscosity had been produced. In vitreoretinal surgery, medium-viscosity PDMS has advantages over the other types of PDMS due to its injectability and lower propensity to emulsify. However, to produce a high-quality medium viscosity PDMS and fulfill stringent requirements, the conditions affecting the synthesis results need to be explored. Here, we reported the effect of changing one of the PDMS synthesis parameters, namely, the volume ratio composition of low-grade D4 monomer and chain terminator of hexamethyldisiloxane (MM) in producing medium viscosity PDMS. PDMS with low viscosity was successfully synthesized with a ratio of D4:MM = 26:10. However, only by changing the ratio of D4:MM from 26:10 to 46:10, the resulting PDMS increased in viscosity from low- to medium-viscosity PDMS of 1.81 Pa s. Quality improvement was also indicated by high surface tension and higher yield values. The medium viscosity PDMS had a refractive index and functional group values similar to the PDMS produced in previous studies.