Shape Memory Polyurethane Foams: Innovative Solutions for Safer and Sustainable Applications

Polyurethane (PU) foams are extensively used in modern society, appearing in products such as upholstery, insulation, and various everyday items. However, their large volume can be problematic, as significant space is required during transportation and storage. Producing PU foam on-site is an alternative, but it involves handling isocyanates, which pose serious occupational health and safety risks, including respiratory irritation and long-term health effects.[1] Shape memory polymers (SMPs) present an innovative solution to these issues. As "smart materials", SMPs change shape in response to external stimuli such as temperature.[2] This is achieved through a thermomechanical "programming step": 1) heating above the phase-transition temperature, 2) loading, 3) cooling below the phase-transition temperature, and 4) unloading. Upon heating, the material then returns from the "programmed shape" to its original form (one-way shape memory effect), while some SMPs perform reversible actuation between two semi-stable states (two-way shape memory effect (2W SME)).[3] Our group implemented both effects into PU foams for innovative building applications. Programmed PU foam may exhibit a 2W SME with a maximum actuation of 22.7 %. Such behaviour could reduce energy consumption by up to 45 % in certain scenarios (Fig. 1A).[4] In 2025, the concept of FOIM (FOIl + foaM) was introduced. The material can be compressed into a translucent foil and recovers shape upon heating to 45 °C, thus exhibiting a recovery ratio of 99.5 % and an increase in height increase by 1600 % (Fig. 1B).[5]
References:
[1] A. Munn, Annals of Occupational Hygiene 1965, 163.
[2] T. Pretsch in Konstruktionspraxis (Ed.: H. Böse), Vogel Communications Group, Würzburg, 2023, pp. 227–259.
[3] a) T. Pretsch, Polymers 2010, 2, 120; b) A. Lendlein, S. Kelch, Angew. Chem. Int. Ed. 2002, 41, 2034.
[4] a) M. Walter, F. Friess, M. Krus, S. M. H. Zolanvari, G. Grün, H. Kröber, T. Pretsch, Polymers 2020, 12; b) M. Walter, K. Lengsfeld, D. Borschewski, S. Albrecht, P. Kölsch, T. Pretsch, M. Krus, S. Lehmann-Brauns, Buildings 2022, 12, 2236.
[5] A.-L. Poser, T. Pretsch, Macromolecular Rapid Communications 2025, 46, e2401103.