Polydimethylsiloxane (PDMS) is one of the most superior materials and has been used as a substitute for vitreous humor in the human eye. In previous research, we have succeeded in producing PDMS with low and medium viscosity using octamethylcyclotetrasiloxane (D4) monomer with a low grade of 96%. Both have good physical properties and are comparable to commercial product PDMS and PDMS synthesized using D4 monomer with a high grade of 98%. An improvement of the synthesis process is needed to ensure that PDMS synthesized from a low-grade D4 monomer under specific synthesis conditions can repeatedly produce high-quality PDMS. Apart from good physical properties, the PDMS as a substitute for vitreous humor must also be safe and not cause other disturbances to the eyes. Here, we reported the process of synthesizing and characterizing the physical properties of low- and medium-viscosity PDMS using a low-grade D4 monomer. We also reported for the first time the in vitro toxicity test using the Hen’s Egg Test Chorioallantoic Membrane (HET-CAM) test method. We have succeeded in obtaining PDMS with viscosities of 1.15 Pa.s, 1.17 Pa.s, and 1.81 Pa.s. All samples have good physical properties such as refractive index, surface tension, and functional groups that are similar to commercial PDMS. The HET-CAM test results showed that all samples did not show signs of irritation indicating that samples were non-toxic. From the results of this study, it can be concluded that PDMS synthesized from a low-grade D4 monomer under specific synthesis conditions by the ROP method is very safe and has the potential to be developed as a substitute for vitreous humor in human eyes.

Polydimethylsiloxane (PDMS) is a substitute for vitreous humour in vitreoretinal surgery and is usually produced from octamethylcyclotetrasiloxane (D4). In Indonesia, both commercial PDMS and D4 are limited and expensive. Dichlorodimethylsilane (DCMS) can be an alternative to produce PDMS. DCMS is cheaper and easier to obtain than D4. However, more extra effort is needed in order to produce PDMS from DCMS. Therefore, this study aimed to produce PDMS from DCMS by varying the ratio of DCMS precursor to dichloromethane (DCM) solvent at ratios of 1:1 and 1:4 through the hydrolysis–condensation method under neutral conditions. The PDMS produced had medium- (2.06 Pa·s) and high viscosity (3.59 Pa·s), with densities ranging from 0.96 to 0.99 g/mL. The refractive index was 1.4034–1.4036 and surface tension was 21 × 10⁻³ N/m, while they were able to transmit ~100% visible light, which were similar values to the commercial PDMS characteristics. PDMS samples were characterized using IR and NMR spectroscopy, which confirmed they were of PDMS type. The most optimum DCMS:DCM ratio was 1:1 due to the medium-viscosity PDMS type that could be produced. The in vitro HET–CAM toxicity test showed that samples were non-irritant, similar to PDMS produced from D4. PDMS from DCMS was non-toxic and ready to be used as a vitreous humuor substitution.

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.

Polymethylhydrosiloxane (PMHS) has been considered to be developed as an alternative material of polydimethylsiloxane (PDMS) for vitreous humour substitution. This polymer production begins with hydrolysis of dichloromethylsilane (DCMS), as raw material, which continues through condensation polymerization. Previous research reported the synthesis of PMHS using an acid solvent with different temperature variations and indicated that low-viscosity PMHS can be produced through condensation at 15–20 °C. However, this process requires a very long polymerization time. Meanwhile, synthesis using a higher temperature of 50 °C required a catalyst. The influence of solvents, one of the important synthesis temperatures, on the synthesis process of PMHS has not been explored. Furthermore, the toxicity of this material has not been reported. In this study, PMHS with low- and medium-viscosity were synthesized from DCMS with different solvents and additional control of the condensation temperature to accelerate the polymerization. Utilizing a basic diethyl ether (DE) solvent facilitates a higher viscosity value than an acidic dichloromethane (DCM) solvent. All PMHS samples were characterized by a viscometer, refractometer, surfgauge, UV–Vis, FTIR, and NMR spectroscopy. The in vitro hen’s egg chorioallantoic membrane (HET-CAM) toxicity test of PMHS was also conducted. A low-viscosity PMHS sample had a surface tension of 20 milliN/m and a refractive index of 1.3960, while medium-viscosity had 21 milliN/m and 1.3982. All samples were ~ 100% transparent, had typical functional groups of PMHS, and did not show signs of being irritant (non-toxic). Therefore, PMHS has the potential to be developed as a new material for vitreous humour substitution.

Self-polymerization offers an easy and simple technique to produce polydimethylsiloxane (PDMS) from dichlorodimethylsilane (DCDMS). This method is a condensation stage that does not require additional treatments and materials. Here, we report the self-polymerization technique for the synthesis of high-viscosity PDMS without using a catalyst. Synthesis was carried out using dichloromethane (DCM) solvent with the volume ratio to DCDMS was 1:1. The polymerization process lasted for 63 days. PDMS with a viscosity of 5.13 Pa s which meets the category of high-viscosity of vitreous substitution obtained. The sample was clear and had a refractive index of 1.4028, slightly lower than commercial PDMS. The surface tension of the sample was 21 milliN/m. The sample has the advantage of higher surface tension compared to the commercial PDMS. It will have the effect of reducing the emulsification tendency. The viscosity, refractive index, and surface tension of the sample meet the requirements for the application of a vitreous humour substitute. This research reduced the number of catalyst and solvent used in the hydrolysis and accelerated the polymerization process.