A research team in the Department of Chemical and Biomolecular Engineering, consisting of Professor Sung Gap Im, Dr. Do Heung Kim, MS candidate Keonwoo Choi, and PhD candidate Won-Tae Jang, reported a novel technology that uses a one-step deposition process to increase the transparency of refractive polymer film. A notable quality of the resulting sulfur-containing polymer (SCP) film is its extremely high refractive index and its transparency within the entire visible range, allowing a variety of application in optoelectronic devices such as molded lenses, coatings, and stacks. The film is also extremely stable against environmental and chemical conditions, which is instrumental for its application in optical devices.

Due to advancements in optics, the need for high refractive materials is increasing. This research may open up a new way to meet this demand. Existing high refractive materials are costly to manufacture and not widely available in Korea. Traditional manufacturing techniques make use of difficult-to-control chemical reactions and chemicals that do not readily combine. The new material is easier to produce because it requires only a one-step vaporization process that yields many desirable properties. The discovered polymer’s refractive index exceeds 1.9, whereas very few polymers can exceed 1.75. Furthermore, the new polymer film is highly customizable and can be coated on a wide variety of textured surfaces. These factors combined give the SCP film a considerable advantage compared to its competitors. “[The discovered film] will serve as a platform material for future high-end optical applications,” Professor Im claimed.

To create the film, the research team capitalized on elemental sulfur’s known properties. By polymerizing vaporized sulfur with several vinyl-containing monomers, they were able to create a transparent non-crystalline polymer with great thermal stability. The film’s transparency is attributed to its uniformly dispersed, short-segmented polysulfide chains, a well-observed feature in polymerization with molten sulfur. The easy manufacturing process of the new film promises a cheap and efficiently produced alternative to existing materials. 

The study was reported in the prestigious Science Advances scientific journal, under the title “One-Step Vapor-Phase Synthesis of Transparent High-Refractive Index Sulfur-Containing Polymers”.