Síntese de Copolímeros anfifílicos: relação entre estrutura molecular e agregação em solução aquosa

Abstract

In recent decades amphiphilic polymer materials have generated interest in the scientific community due to its ability to form micellar particles in medium aqueous condition and it can be used in several areas such as in biomaterials, in stabilizing pharmaceutical emulsions, incorporation of toxic or polluting , entrainment and controlled release of drugs and various other applications. Various types of polymers can be appointed, among them being those derived from 2-dimetylamynoethyl methacrylate (DMAEMA) having properties in response to temperature and pH. Copolymers of PDMAEMA with non-polar monomers such as acrylate of n-butyl (nBA) form amphiphilic materials which tend to aggregate in aqueous solution, forming particles able to incorporate relatively hydrophobic substances (contaminants, for example), ion and other properties of interest. In this work copolymers were synthesized in blocks based on DMAEMA and nBA with different molecular weight average and ratios between the blocks for the study of systematic influence of the molecular structure on properties such as size and shape of the aggregates in solution, the response to temperature and pH, among others. For the synthesis of polymers were used the RAFT technique (English acronym for Reversible Addition-Fragmentation chain Transfer) that allows control of the weight in the molecular of the polymer and facilitates the construction of copolymers in block. The synthesized polymers were characterized by different techniques such as Nuclear Magnetic Resonance Proton (1H NMR); Gel Permeation Chromatography (GPC); spectroscopy in the region of the infrared with Fourier Transform Attenuated and Total Reflectance and (FTIR-ATR) spectroscopy and UV/VIS. The aggregates formed in an aqueous solution had its size determined by the Dynamic Light Scattering (DLS). The materials were synthesized to form aggregates in aqueous solutions. Even homopolymer of PDMAEMA , in all conditions studied, although the aggregate of the copolymers showed greater size. It was not possible to reach any relation to the size and pH or even content PNBA in the diblock copolymer. However, in almost all conditions studied, the aggregate has a direct correlation with its concentration, making these systems very different from regular micelles in the same range of conditions. This effort fits into a wide objective to create trusting relationships between polymer structure and their properties in order to increase the efficiency of the process in synthesis of materials for specific applications.