Polímeros Helicoidales Supramoleculares

Abstract

Supramolecular chemistry is a broad area of study, whose development in recent years has been exponential due to the promising applications of these materials, as well as an increasing number of specialized research groups. Supramolecular helical polymers are postulated as a viable solution to the scientific community's need to synthesize nonnatural macromolecules that replicate the behavior, and consequently the functions, of biomolecules in living organisms. These materials are mainly characterized by a modulable and reversible self-assembly and may submit a helical conformation responsible for providing the aggregate with optical activity. Moreover, the real relevance of this type of materials lies in the possibility of modulating their helicity (direction of rotation of the helix) by subjecting them to certain external stimuli (solvent polarity, temperature, pH, etc.), which makes it possible to control their optical activity by means of a stimulus-response system. For this work, a precursor monomer was synthesized and characterized, which was subsequently subjected to aggregation studies. The result was the obtaining and characterization of a stable supramolecular helical polymer with photochemical response capacity thanks to the incorporation of an azobenzene subunit, which allows the E-Z equilibrium to be modified in a simple way. This helical aggregate was prepared from a chiral precursor monomer derived from L-Valine to which a π-conjugated OPE subunit is covalently associated, which confers stiffness to the system, favoring self-assembly by means of π-π interactions. To study the secondary structure of the supramolecular helical polymer obtained, several structural and optical characterization techniques were used, such as Mass Spectrometry, Nuclear Magnetic Resonance (NMR), Polarimetry, Circular Dichroism (CD), Ultraviolet (UV-Vis) and Fourier Transform Infrared (FT-IR) Absorption Spectroscopy, Dynamic Light Scattering (DLS), RAMAN and Scanning Electron Microscopy (SEM). The information reported by these techniques will be used to describe and clarify the assembly mechanism adopted by the aggregate, as well as its behaviour in response to light and thermal stimuli.