Pyroelectricity describes the generation of electricity by temporal temperature change in polar materials. However, thin pyroelectric films without post-treatments such as polarization or stretching remain a formidable challenge. Attempting to discover a solution to this obstacle, we combined molecular design of polar side groups with engineering of oriented polymer chains. This combination results in pyroelectricity of purely molecular origin. Here, we report a polar polyacrylonitrile polymer brushes exhibiting a superior pyroelectric behavior which is caused by the forced orientation of polar side groups due to the special off-axis structure of the polymer backbone. The obtained pyroelectric coefficient is comparable to that of polyvinylidene difluoride at room temperature.