Synthesis and characterization of polymethylhydrosiloxane using dichloromethane as a candidate material for vitreous substitution

Polydimethylsiloxane (PDMS) is a common material as vitreous humor substitution in vitreoretinal surgery. PDMS is obtained from octamethylcyclotetrasiloxane (D4) monomer. However, alternative synthesis methods that might be more accessible or efficient under local conditions need to be developed. Therefore, finding other materials as an alternative to substitute vitreous humor is necessary. This article presents the results of the synthesis and characterization of polymethylhydrosiloxane (PMHS), produced using dichloromethylsilane (DCHS) as a precursor and dichloromethane (DCM) as a solvent, as a potential material for vitreous substitution in ophthalmological procedures. The focus is on exploring the two-stage process, namely the hydrolysis method to produce short-chain PMHS and the condensation method to produce long-chain PMHS that meet the requirements to be used as vitreous humor substitution. The polymerization process was accelerated by heating and assisted by potassium hydroxide (KOH). The short-chain PMHS had a viscosity of 50 mPa.s, a refractive index of 1.3954, and a surface tension of 18 mN/m, while the long-chain PMHS had a viscosity of 930 mPa.s, a refractive index of 1.3978, and a surface tension of 19 mN/m, respectively. The PMHS was characterized using FTIR spectroscopy and NMR spectroscopy. It was found that Si-H as a typical functional group of PMHS was observed from FTIR spectroscopy. From the NMR characterization, the possible long-chain PMHS structure is -O-{-SiH(CH3)-}n-O which shows that the sample has polymerized well producing long chains. All the characterization results of the synthesized PMHS showed that this material has potential as a candidate material for vitreous substitution.