Plants can respond differently to different wavelengths in sunlight's spectral range, and crop covers containing additives have a great effect on the growth of crops. This research focuses on synthesising new hydroxybenzophenones bearing long alkyl chains to confer polymer solubility, and to measure their UV absorption and photochemical stability. Compounds substituted with fluorine atoms or different amino groups in particular were under investigated, as these groups may impart stability towards oxidative degradation, or alter the absorption maximum. Related naphthalene analogues were substituted with different amine groups for comparing UV absorption and photostability. Modification of Uvinul A Plus was carried out to improve UV absorption maximum wavelength and light fastness.