Patrícia V. Mendonça

Synthesis of cationic poly((3-acrylamidopropyl)trimethylammonium chloride) by SARA ATRP in ecofriendly solvent mixtures

Supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) of the cationic monomer (3-acrylamidopropyl)trimethylammonium chloride (AMPTMA) was successfully performed for the first time. The polymerizations were performed in water or ethanol–water mixtures at room temperature in the presence of Cu(0), using relatively low concentrations of soluble copper catalyst and an excess of ligand (Me6TREN). The reaction conditions were optimized to give the best control over the polymerization under environmentally friendly conditions. The polymerization data showed good control over the molecular weights with narrow molecular weight distributions for the entire polymerization. The preservation of the chain-end functionality was confirmed by self-chain extension and the synthesis of a block copolymer containing AMPTMA and oligo(ethylene oxide) methyl ether acrylate (OEOA). SARA ATRP was also extended to the synthesis of alkyne-terminated poly-AMPTMA (PAMPTMA), which was subsequently functionalized, using copper(I) catalyzed azide–alkyne cycloaddition, with an azido-functionalized coumarin derivative.

Recent Developments in Antimicrobial Polymers: A Review

Antimicrobial polymers represent a very promising class of therapeutics with unique characteristics for fighting microbial infections. As the classic antibiotics exhibit an increasingly low capacity to effectively act on microorganisms, new solutions must be developed. The importance of this class of materials emerged from the uncontrolled use of antibiotics, which led to the advent of multidrug-resistant microbes, being nowadays one of the most serious public health problems. This review presents a critical discussion of the latest developments involving the use of different classes of antimicrobial polymers. The synthesis pathways used to afford macromolecules with antimicrobial properties, as well as the relationship between the structure and performance of these materials are discussed.

Synergistic Effect of 1‑Butyl-3-methylimidazolium Hexafluorophosphate and DMSO in the SARA ATRP at Room Temperature Affording Very Fast Reactions and Polymers with Very Low Dispersity

An unusual synergistic effect between 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) and dimethyl sulfoxide (DMSO) mixtures is reported for the supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) of methyl acrylate (MA) using a catalytic system composed by sodium dithionate (Na2S2O4) and CuBr2/Me6TREN (Me6TREN: tris[2-(dimethylamino)ethyl]amine) at room temperature. To the best of our knowledge, the use of ionic liquids (IL) has never been reported for the SARA ATRP. The kinetic data obtained for a broad range of target molecular weights revealed very fast polymerization rates, low dispersity values (Đ < 1.05) and well-defined chain-end functionalities.

Getting faster: low temperature copper-mediated SARA ATRP of methacrylates, acrylates, styrene and vinyl chloride in polar media using sulfolane/water mixtures

Supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) of acrylates, methacrylates, styrene and vinyl chloride was successfully performed in sulfolane/water mixtures using ppm amounts of soluble copper. The catalytic effect of the presence of water in the reaction mixtures resulted in a notable acceleration of the polymerization of the different monomers studied. The first-order kinetics with monomer conversion and the low dispersity values (Đ) of the polymers revealed the controlled features of the polymerization. As a proof-of-concept, an ABA block copolymer of poly(methyl acrylate)-b-poly(vinyl chloride)-b-poly(methyl acrylate) was prepared, confirming also the “living” character of the polymers. The results presented in this contribution extend the importance of sulfolane as an universal industrial solvent for the SARA ATRP of a broad range of monomer families by significantly enhancing the polymerization rate, due to the selective addition of water to the solvent mixture. The incorporation of small amounts of water in the solvent mixture has also allowed the use of FDA-approved sulfites as the SARA agent, which was not possible using pure sulfolane as the polymerization solvent.

The Importance of Controlled/Living Radical Polymerization Techniques in the Design of Tailor Made Nanoparticles for Drug Delivery Systems

Recent developments in controlled/living radical polymerization methods (CLRP) have created the opportunity to prepare polymeric based systems with site specific functionality that has significantly expanded the range of physical and chemical properties that can be generated in materials prepared by these systems. For example, CLRP prepared block copolymers can self-assemble into nanoparticles that can be used in drug delivery applications. The development of synthetic procedures for preparation of materials targeting new and more efficient drug delivery systems (DDS) is of great interest since ultimately they can mimic most of the properties of biological systems.

Tailored design of renewable copolymers based on poly(1,4-butylene 2,5-furandicarboxylate) and poly(ethylene glycol) with refined thermal properties

In the recent years, search for innovative polymers derived from renewable resources resulted in an intense research and development of 2,5-furandicarboxylic acid-based polyesters. Special emphasis has been placed in high-performance polyesters, such as the poly(1,4-butylene 2,5-furandicarboxylate) (PBF)-based structures. In this study, both thermal and crystallisation-thermal properties of PBF have been enlarged simply by the incorporation of other renewable soft moieties in the polymer structure, namely, poly(ethylene glycol) (PEG) moieties. In particular, these novel copolymers can be designed to show some advantageous processing features as revealed by the lower melting temperature (in particular, it could be 107 °C) and higher thermal stability (up to 352–380 °C) as compared with PBF. Moreover, fast scanning calorimetric (FSC) studies of these novel copolymers indicated that crystallisation could be prevented even using relatively slow cooling rates (e.g., 0.1 °C s−1). The judicious selection and balance between hard PBF and soft PEG units enabled a segmented copolymer behaviour.

Synthesis of tailor-made bile acid sequestrants by supplemental activator and reducing agent atom transfer radical polymerization

This work reports the synthesis of tailor-made polymeric bile acid sequestrants (BAS) by supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) using ecofriendly conditions. The new materials were based on amphiphilic poly(methyl acrylate)-b-poly((3-acrylamidopropyl)trimethylammonium chloride) (PMA-b-PAMPTMA) star block copolymers and cationic hydrogels (PAMPTMA). The in vitro sequestration ability of the polymers was investigated in simulated intestinal fluid using sodium cholate (NaCA) as the bile salt model molecule. Both polymeric structures investigated showed higher affinity towards NaCA micelles than unimers. The cationic hydrogels proved to be attractive BAS candidates, with binding parameters similar to those of the most effective commercial BAS: Colesevelam hydrochloride. Several polymer features were investigated for the star block copolymers in order to understand the structure/performance relationship. It was found that the binding parameters can be tuned by targeting different compositions of the block copolymers and, typically, longer cationic arms led to enhanced binding capacity.

Mechanism of supplemental activator and reducing agent atom transfer radical polymerization mediated by inorganic sulfites: experimental measurements and kinetic simulations

The mechanism of atom transfer radical polymerization (ATRP) mediated by sodium dithionite (Na2S2O4), with CuIIBr2/Me6TREN as catalyst (Me6TREN: tris[2-(dimethylamino)ethyl]amine)) in ethanol/water mixtures, was investigated experimentally and by kinetic simulations. A kinetic model was proposed and the rate coefficients of the relevant reactions were measured. The kinetic model was validated by the agreement between experimental and simulated results. The results indicated that the polymerization followed the SARA ATRP mechanism, with a SO2•- radical anion derived from Na2S2O4, acting as both supplemental activator (SA) of alkyl halides and reducing agent (RA) for CuII/L to regenerate the main activator CuI/L. This is similar to the reversible-deactivation radical polymerization (RDRP) procedure conducted in the presence of Cu0. The electron transfer from SO2•-, to either CuIIBr2/Me6TREN or R-Br initiator, appears to follow an outer sphere electron transfer (OSET) process. The developed kinetic model was used to study the influence of targeted degree of polymerization, concentration of CuIIBr2/Me6TREN and solubility of Na2S2O4 on the level of polymerization control. The presence of small amounts of water in the polymerization mixtures slightly increased the reactivity of the CuI/L complex, but markedly increased the reactivity of sulfites.

Drug Delivery Systems for Predictive Medicine: Polymers as Tools for Advanced Applications

Predictive medicine represents a new philosophy in healthcare involving the detection of pathology-specific molecular patterns before the emergence of signs and symptoms, which in some diseases (e.g., diabetes) surged accompanied by severe secondary complications. Advanced drug delivery systems (DDS) present important benefits for this new and fascinating area, since they enable to deploy active molecules in specific targeted regions of the body in a controlled manner. The exponential development achieved in DDS during the last decades can be used to develop effective solutions for the premature detection and effective treatment of different pathologies. Polymers provide the ideal opportunities for the development of new effective DDS due to the easy processing and to the control over the physical and chemical characteristics that can be accomplished during the polymerization.

Deep Eutectic Solvent Aqueous Solutions as Efficient Media for the Solubilization of Hardwood Xylans

This work contributes to the development of integrated lignocellulosic-based biorefineries by the pioneering exploitation of hardwood xylans by solubilization and extraction in deep eutectic solvents (DES). DES formed by choline chloride and urea or acetic acid were initially evaluated as solvents for commercial xylan as a model compound. The effects of temperature, molar ratio, and concentration of the DES aqueous solutions were evaluated and optimized by using a response surface methodology. The results obtained demonstrated the potential of these solvents, with 328.23 g L-1 of xylan solubilization using 66.7 wt % DES in water at 80 °C. Furthermore, xylans could be recovered by precipitation from the DES aqueous media in yields above 90 %. The detailed characterization of the xylans recovered after solubilization in aqueous DES demonstrated that 4-O-methyl groups were eliminated from the 4-O-methylglucuronic acids moieties and uronic acids (15 %) were cleaved from the xylan backbone during this process. The similar Mw values of both pristine and recovered xylans confirmed the success of the reported procedure. DES recovery in four additional extraction cycles was also demonstrated. Finally, the successful extraction of xylans from Eucalyptus globulus wood by using aqueous solutions of DES was demonstrated.