Smart Responsive Polymers Enable Summer Radiative Cooling and Winter Heat Retention.

Conventional static radiative cooling materials cause winter overcooling, whereas existing dynamic systems remain limited by unsuitable transition temperatures, leakage, poor cycling stability, and complex fabrication. Here, we develop a readily manufacturable, cost-effective, and leakage-free temperature-responsive fluoropolymer that autonomously switches between radiative cooling and heat retention near the human comfort range. An imidazolium-based plasticizer (TMT) with a phase-transition temperature of 24 °C is incorporated into the fluoropolymer to regulate its temperature-dependent surface composition. Above 24 °C, TMT dissolves in the fluoropolymer matrix, enhancing infrared emissivity for efficient radiative cooling. Below 24 °C, TMT blooms onto the surface, where the surface accumulation of TMT enhances solar absorption while reducing infrared emission within the atmospheric transparency window. This reversible dissolve-in/bloom-out mechanism allows the polymer to adaptively regulate thermal radiation, overcoming the limitations of conventional phase-change systems. Outdoor tests demonstrate 11.4 °C cooling below the surrounding temperature in summer and 3.0 °C warming above the surrounding temperature in winter. This dissolve-in/bloom-out mechanism establishes a paradigm for realizing energy-efficient building envelopes and sustainable climate conditioning.