Photostability and Dynamic Helical Behavior in Chiral Poly(phenylacetylene)s with a Preferred Screw-Sense

Data Availability Statement The data that support the findings of this study are available in the supplementary material of this article.Acknowledgements We thank Servicio de Microscopía Electrónica (RIAIDT, USC). Financial support from AEI (PID2019-109733GBI00), Ministerio de Ciencia e Innovación (PID2019- 107307RB-100 and PID2020-117605GB-100, PID2020- 113059GB-C21, PID2020-113059GB-C22). Xunta de Galicia (ED431C 2018/30, ED431C 2021/40, Centro Singular de Investigación de Galicia acreditación 2019–2022, ED431G 2019/03 and the European Regional Development Fund (ERDF) is gratefully acknowledged. F.R.T. thanks Xunta de Galicia for a predoctoral contract. We acknowledge CESGA for computational time and we also thank Servicio de Nanotecnología y Análisis de Superficies (CACTI-CINBIO, UVigo).Helical polymers such as poly(phenylacetylene)s (PPAs) are interesting materials due to the possibility of tuning their helical scaffold (sense and elongation) once they have been prepared and by the presence of external stimuli. The main limitation in the application of PPAs is their poor photostability. These polymers degrade under visible light exposure through a photochemical electrocyclization process. In this work, it was demonstrated, through a selected example, how the photochemical degradation in PPAs is directly related to their dynamic helical behavior. Thus, while PPAs with dynamic helical structures show poor photostability under UV/Vis light exposure, poly-(R)-1, bearing an enantiopure sulfoxide group as pendant group and designed to have a quasistatic helical behavior, shows a large photostability due to the restricted conformational composition at the polyene backbone, needed to orient the conjugated double bonds prior to the photochemical electrocyclization process and the subsequent degradation of the material.AEI (PID2019-109733GBI00)Ministerio de Ciencia e Innovación (PID2019- 107307RB-100 and PID2020-117605GB-100, PID2020- 113059GB-C21, PID2020-113059GB-C22)Xunta de Galicia (ED431C 2018/30, ED431C 2021/40, Centro Singular de Investigación de Galicia acreditación 2019–2022, ED431G 2019/03 and the European Regional Development Fund (ERDF