Abstract
End-group functionalization of homopolymers is a valuable way to produce high-fidelity nanostructured and functional soft materials when the structures obtained have the capacity for self-assembly (SA) encoded in their structural details. Herein, an end-functionalized PCL with a π-conjugated EDOT moiety, (EDOT-PCL), designed exclusively from hydrophobic domains, as a functional “hydrophobic amphiphile”, was synthesized in the bulk ROP of ε-caprolactone. The experimental results obtained by spectroscopic methods, including NMR, UV-vis, and fluorescence, using DLS and by AFM, confirm that in solvents with extremely different polarities (chloroform and acetonitrile), EDOT-PCL presents an interaction- and structure-based bias, which is strong and selective enough to exert control over supramolecular packing, both in dispersions and in the film state. This leads to the diversity of SA structures, including spheroidal, straight, and helical rods, as well as orthorhombic single crystals, with solvent-dependent shapes and sizes, confirming that EDOT-PCL behaves as a “block-molecule”. According to the results from AFM imaging, an unexpected transformation of micelle-type nanostructures into single 2D lamellar crystals, through breakout crystallization, took place by simple acetonitrile evaporation during the formation of the film on the mica support at room temperature. Moreover, EDOT-PCL’s propensity for spontaneous oxidant-free oligomerization in acidic media was proposed as a presumptive answer for the unexpected appearance of blue color during its dissolution in CDCl3 at a high concentration. FT-IR, UV-vis, and fluorescence techniques were used to support this claim. Besides being intriguing and unforeseen, the experimental findings concerning EDOT-PCL have raised new and interesting questions that deserve to be addressed in future research.
Highlights
Today, a plausible way to find new functions of conventional polymers, in order to better fit a given application, is through high-precision polymers with complex architectures [1]
Nuclear magnetic resonance spectroscopy (NMR), UV-vis and fluorescence spectroscopy, as well as dynamic light scattering (DLS) were chosen as methods sensitive to the intrinsic solvent effects and to those that occur as a result of a change in the solute conformation or structure due to the change in the solvent
By comparing these spectra with previously published data, for which the EDOT-PCL macromonomer nuclear magnetic resonance spectroscopy (NMR) registration was performed in deuterated chloroform (CDCl3) [42], an increased polarity of CD3CN was shown to influence the position of the signals in the 1H-NMR spectrum, as was expected [57]
Summary
A plausible way to find new functions of conventional polymers, in order to better fit a given application, is through high-precision polymers with complex architectures [1]. As different properties have been demonstrated through a comparison with the classical, linear arrangement of the chain [2], the goal of producing polymers with complex architectures can be achieved by applying the concept “from functionality to function”. In this regard, polymeric materials with specific chain-end functionality have become accessible, especially through “living” controlled polymerizations [3,4], which have led to the production of valuable materials with new and improved properties [5,6,7] and to reactive intermediates of great interest for the construction of polymers with defined molecular architectures [4,8,9]. The existing polymer properties, such as enzymatic degradation [6], of the solution–protein interaction [10] or the drug loading capacity [5] can be manipulated through the functional end-groups, or other new properties can be added such as fluorescence properties [7,11]
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