Porous Polymers Create White, Water-Repellent Surfaces Without Pigments or PFAS

Researchers have developed a method that gives polymers an intensely white appearance and water-repellent surface without adding white pigments or PFAS. The technique uses microscopic pores to control how materials interact with light and water, with potential applications in packaging, films and textiles.

An international team led by Professor Easan Sivaniah at Kyoto University’s Institute for Integrated Cell-Material Sciences developed the approach with researchers from Tokyo Metropolitan University and Donghua University. Their process, called Deep Foam Photolithography (DFP), works with several commercially available polymers.

Taking Inspiration From Nature

Snow, clouds and sea foam appear white because their structures scatter visible light. This phenomenon, known as structural whiteness, produces brightness without white pigments.

The researchers combined this principle with inspiration from water-repellent natural surfaces, such as lotus leaves. By creating a porous interior and a rough outer surface, they incorporated both optical and water-repellent properties into the material’s structure.

This approach could reduce reliance on titanium dioxide, a mineral pigment commonly used to provide whiteness and opacity in packaging, films and coatings. It also offers a route to water repellency without PFAS, a group of fluorinated substances associated with environmental persistence and concerns about health and environmental impacts.

Creating Pores With Light and Solvent

The process begins by exposing a polymer to light, which breaks it into smaller molecular fragments. Treatment with a mild solvent then causes the material to swell, forming an open network of microscopic pores.

These pores scatter light, making the material appear white without added pigment. Meanwhile, the resulting surface texture strongly repels water.

DFP therefore creates two functions through the same structural transformation. For designers, this suggests opportunities to develop surfaces whose appearance and interaction with water depend on their microscopic architecture.

Applications in Films and Textiles

The team demonstrated the technique on polymer films and, through collaboration with Donghua University’s textile researchers, on fabrics. The printable materials platform can achieve a resolution of 20,000 dots per inch, allowing finely detailed patterning.

Using existing commercial polymers could help broaden its practical relevance. However, the researchers identify achieving the scale and cost of established materials as a key challenge for nature-inspired material technologies.

A Different Route to Material Performance

The research points towards potentially lighter materials that require fewer mineral pigments and no PFAS to achieve the demonstrated functions. Its sustainability potential lies in reducing reliance on these additives by building performance into the material itself.

The findings do not establish that the resulting polymers are biobased, biodegradable or recyclable. Instead, they demonstrate a structural approach to combining whiteness, printability and water management.

Source: ScienceDaily
Image: Claudia Rosa