Optical engineering of polymer materials and composites for simultaneous color and thermal management

Sustainable architecture requires development of new materials with tailored optical, mechanical, and thermal properties to provide both aesthetic appeal and energy-saving functionalities. Polymers and polymer-based composites emerge as promising lightweight and conformable materials whose optical spectra can be engineered to achieve both goals. Here, we report on the development of new types of organic-inorganic films composed of ultrahigh molecular weight polyethylene with a variety of organic and inorganic nano- and micro-scale inclusions. The films simultaneously provide ultra-light weight, conformability, either visual coloring or transparency on demand, and passive thermal management via both conduction and radiation. The lightweight semi-crystalline polymer matrix yields thermal conductivity exceeding that of many metals, allowing for the lateral heat spreading and hot spots mitigation in the cases of partial illumination of films by sunlight. It also yields excellent broadband transparency, allowing for the opportunities to shape the spectral response of composite materials via targeted addition of inclusions with tailored optical spectra. We demonstrate a variety of dark- and bright-colored composite samples that exhibit reduced temperatures under direct illumination by sunlight, and outline strategies for materials design to further improve material performance.