Widespread reliance on non-renewable materials, e.g., in the packaging sector, contributes to resource depletion and pollution. While sustainable material alternatives such as biopolymers exist, their adoption is hampered by limited performance, particularly in terms of gas permeability and mechanical stability. The application of thin functional coatings can compensate for performance shortcomings and is a promising solution to this problem.

However, conventional coatings were developed for petroleum-based substrates utilizing thermal, ultraviolet, or chemical curing methods and thus high energy inputs or toxic agents. To address these challenges, we have developed an inorganic-organic hybrid polymer coating (IOHPC) that achieves excellent oxygen transmission rate (OTR) and Martens hardness under ambient curing conditions. This innovative material eliminates the need for toxic curing agents and preserves heat-sensitive substrates such as biodegradable substrates.

The key was to select the ideal metal alkoxide within the hybrid network, which ensures efficient network formation and material performance with minimum energy input during processing. This was characterized by ATR-FTIR, ²⁹Si CP-MAS NMR, X-ray photoelectron spectroscopy and mechanical and barrier analysis. Most importantly, the IOHPC effectively transferred its performance to three classes of heat-sensitive, sustainable substrates - recycled HDPE, polylactic acid and reduced thickness polypropylene - achieving OTR values between 22 and 31 cm³/(m²·d·bar). This IOHPC demonstrates the potential for utilization on additional sustainable substrates while preserving substrate integrity, reducing energy consumption and thus potentially leading to next-generation packaging solutions (Figure 1).