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In this study, the optical properties of transparent bioplastics have been investigated. The long‐term technological goal is to establish biopolymers in a new market segment for demanding optical applications and to contribute to a more sustainable economy. A collection of transparent bioplastics has been tested with respect to the long‐term stability and the possibility of an application in optical components for LED lighting. The focus of materials testing was on the influence of short wavelength visible radiation as well as thermal loads. The results show, that some materials may be candidates for subsequent feasibility studies. To the best of our knowledge, the application of such polymers in complex technical products and in particular in luminaires has not yet been realized. The use of bio‐based plastics for optical components therefore represents a novelty and has a high development potential. [ABSTRACT FROM AUTHOR]

Small angle light scattering (SALS) and differential scanning calorimetry DSC have been applied to investigate the melting of spherulites isothermally crystallized polylactide. At an isothermal crystallization temperature high enough, pure α‐phase crystals are formed. Exposed to a temperature gradient, the crystals first melt and then recrystallize before they finally melt. With decreasing crystallization temperature, an increasing fraction of polylactide is crystallizing in the less stable α′‐phase. α′‐crystals also melt upon increasing the temperature but recrystallize to the more stable α‐phase. A constant spherulite size is revealed by SALS for both processes, the α/α and α′/α melt‐recrystallization, until completion of the final melting, thereby supporting integrity of the spherulites throughout the entire processes. Joint DSC and SALS experiments demonstrate that the depolarized scattering invariant correlates with the heat flow recorded by DSC and thus offer an alternative measure for the degree of crystallinity. The following mechanism is identified for both processes: initial melting and recrystallization overlay each other. Crystallinity is not fully recovered upon recrystallization because only part of the original lamellae survives the melt‐recrystallization, though with an increased thickness. While lamellae are melting and reforming or simply transforming their phase, the spherulites survive the process until final melting. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1483–1495 [ABSTRACT FROM AUTHOR]

A comparative study on the self‐assembly of sexiphenyl‐dicarbonitrile on highly oriented pyrolytic graphite and single‐layer graphene on Cu(111) is presented. Despite an overall low molecule–substrate interaction, the close‐packed structures exhibit a peculiar shift repeating every four to five molecules. This shift has hitherto not been reported for similar systems and is hence a unique feature induced by the graphitic substrates. Stepping on the surface: The self‐assembly of sexiphenyl‐dicarbonitrile on highly oriented pyrolytic graphite and graphene on Cu(111) was studied using scanning tunneling microscopy. The close‐packed networks exhibit a peculiar shift every four or five molecules (see figure). This shift is a unique feature induced by the graphitic substrates. [ABSTRACT FROM AUTHOR]

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