Tuning polarity of polyphenylene dendrimers by patched surface amphiphilicity--precise control over size, shape, and polarity.

In the ideal case, a precise synthesis yields molecules with a constitutional as well as a conformational perfectness. Such a case of precision is demonstrated by the synthesis of semi-rigid amphiphilic polyphenylene dendrimers (PPDs). Polar sulfonate groups are precisely placed on their periphery in such a manner that patches of polar and non-polar regions are created. Key structural features are the semi-rigid framework and shape-persistent nature of PPDs since the limited flexibility introduces a nano-phase-separated amphiphilic rim of the dendrimer. This results in both attractive and repulsive interactions with a given solvent. Frustrated solvent structures then lead to a remarkable solubility in solvents of different polarity such as toluene, methanol, and water or their mixtures. Water solubility combined with defined surface structuring and variable hydrophobicity of PPDs that resemble the delicate surface textures of proteins are important prerequisites for their biological and medical applications based upon cellular internalization.