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pH-responsive polyamidoamine (PAMAM) dendrimers are used as well-defined building blocks to design light-switchable nano-assemblies in solution. The complex interplay between the photoresponsive di-anionic azo dye Acid Yellow 38 (AY38) and the cationic PAMAM dendrimers of different generations is presented in this study. Electrostatic self-assembly involving secondary dipole–dipole interactions provides well-defined assemblies within a broad size range (10 nm–1 μm) with various shapes. The size and shape of these assemblies were determined using dynamic and static light scattering (DLS/SLS) and small-angle neutron scattering (SANS); ζ-potential measurements were performed to elucidate the charge characteristics, revealing the effective surface charge density of the nano-objects as an important parameter in the size and shape control. UV–vis spectroscopy and isothermal titration calorimetry (ITC) were employed to investigate the interaction on a molecular level and from a thermodynamic point of view. The results show that the amount of isomerized cis dye depends on the dendrimer generation because of a photoprotective effect through electrostatics for lower generations and through dipole–dipole interactions for higher generations; as the cis dye and trans dye bind with different strength, the amount of cis dye then again encodes the charge density and thereby the particle size and shape. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) is technologically relevant due to its thermal stability; chemical, mechanical and radiation resistance; transparency; biocompatibility; and ease of processing. Several of those applications are related to its high electroactivity, for which the β-phase of the polymer is its most renowned protagonist. In this context, extensive research has been conducted on the crystallization of PVDF in the β-phase, when processed from melt and from solution. Several decades of research have revealed that electroactive β-PVDF can be nucleated by introducing nanofillers within the polymer matrix, based on electrostatic interactions between polymer chains and fillers. However, one question persists: beyond these electrostatic interactions, on what mechanism does the nucleation of the β-phase in composites depend? This works demonstrates, through the use of small-angle neutron scattering measurements, that the answer is related to the type of fillers' agglomeration.