María del Pilar Carreón-Castro

Synthesis and Characterization of Novel Amphiphilic Azo-Polymers Bearing Well-Defined Oligo(Ethylene Glycol) Spacers

Four novel azo-polymers bearing oligo(ethylene glycol) spacers were synthesized and characterized. Monomers were prepared by esterification of the RED-PEG dyes previously synthesized by us: N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(5-hydroxy-3-oxapentas-1-yl)amine (RED-PEG-2), N-methylN-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(8-hydroxy-3,6-dioxaoctas-1-yl)amine (RED-PEG-3), N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(11-hydroxy-3,6,9-trioxaundecas-1-yl)amine (RED-PEG-4) and N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(17-hydroxy-3,6,9,12,15-pentaoxaheptadecas-1-yl)amine (RED-PEG-6) with methacryloyl chloride. The obtained monomers (nPEGMAN series) were polymerized in the presence of AIBN in THF to give the corresponding azo-polymers (pnPEGMAN series). Also, Langmuir films were prepared with these polymers; the obtained monolayers exhibited good reversible behavior upon successive compression/expansion cycles.

Adsorption and Self-Assembly of Anticancer Antibiotic Doxorubicin on Single-Walled Carbon Nanotubes

We performed a combined experimental and theoretical study of the conjugates obtained from single-walled carbon nanotubes and anticancer antibiotic doxorubicin (DOX). Atomic force microscopy (AFM) imaging at lower magnification revealed, extended regions of single-walled carbon nanotubes (SWNTS) fully covered with DOX adsorbed molecules, along with some bare parts without the adsorbed drug, thus suggesting that the DOX adsorption is a cooperative process. Ambient atmosphere scanning tunneling microscopy (STM) at higher resolutions found that individual SWNTs-DOX conjugates exhibit a periodic texture, whose most important morphological feature is alternating depressions and protrusions along the nanotube. Based on the images and profiles measured, we suggest that doxorubicin molecules self-assemble on SWNTs sidewall according to a helical pattern, in which their tetracyclic fragments are turned with respect to the nanotube axis by about 50∘. To provide an additional insight into the structure of noncovalent SWNTs-DOX conjugates, we employed density functional theory (DFT) calculations with three long-range corrected functionals: M05-2X, wB97X-D and LCBLYP, of which M05-2X yielded the most realistic results in terms of geometries and energies.

Synthesis and characterization of novel dendrons bearing amino-nitro-substituted azobenzene units and oligo(ethylene glycol) spacers: thermal, optical properties, Langmuir blodgett films and liquid-crystalline behaviour.

In this work, we report the synthesis and characterization of a novel series of first and second generation Fréchet type dendrons bearing amino-nitro substituted azobenzene units and tetra(ethylene glycol) spacers. These compounds were fully characterized by FTIR, 1H and 13C-NMR spectroscopies, and their molecular weights were determined by MALDI-TOF-MS. The thermal properties of the obtained dendrons were studied by TGA and DSC and their optical properties by absorption spectroscopy in solution and cast film. Molecular calculations were performed in order to determine the optimized geometries of these molecules in different environments. Besides, Langmuir and Langmuir Blodgett films were prepared with the first generation dendrons that were shown to be amphiphilic. Finally, some of the dendrons showed a liquid crystalline behaviour, which was studied by light polarized microscopy as a function of the temperature in order to determine the transition temperatures and the structure of the mesophase.

Synthesis and Characterization of Novel Polythiophenes Containing Azobenzene Units and Well-Defined Oligo(Ethylene Glycol) Spacers: Thermal and Optical Properties, and Preparation of Langmuir Films

A new series of 3-alkyl-ester-substituted polythiophenes, bearing amino-nitro substituted azobenzenes and flexible tetra(ethylene glycol) spacers, have been synthesized and characterized. First an amphiphilic monomer (E)-2-(4-((4-nitrophenyl)diazenyl)phenyl)-5,8,11-trioxa-2-azatridecan-13-yl 2-(tiophen-3-yl) acetate (AT) was prepared and homo-polymerized to give the corresponding polymer poly[(E)-2-(4((4-nitrophenyl)diazenyl)phenyl)-5,8,11-trioxa-2-azatridecan-13-yl 2-(tiophen-3-yl) acetate] (HP). This monomer was also co-polymerized in the presence of 3-butylthiophene, 3-hexylthiophene and 3-dodecylthiophene to give the corresponding co-polymers CP4, CP6 and CP12. These polymers exhibited molecular weights ranging between 16 500 and 46 990 g/mol. HP showed lower thermal stability than the corresponding co-polymers CP4, CP6 and CP12. The use of 3-alkylthiophene plastificant co-monomers conferred higher thermal stability to the obtained co-polymers. Polymers bearing higher azobenzene content showed to be more susceptible to degradation. All polymers exhibited a maximum absorption band at λ max = 456–475 nm, due to the amino-nitro-substituted azobenzene units. Finally, Langmuir films were prepared with HP and CP4, whose formation was monitored by plotting their surface pressure vs. molecular area (π/A) isotherms and by Brewster angle microscopy (BAM).

Structural and morphological studies of meso-ethylcarbazole F-BODIPY thin films

In this work, we describe the synthesis of meso-(9-ethyl-9H-carbazol-3-yl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and its incorporation as thin film by vapor deposition on indium tin oxide. The morphology of the film was analyzed by scanning electron microscopy and atomic force microscopy showing a granular and homogeneous structure, contact angle measurements revealed that this film exhibits a hydrophobic surface. Packing of the compound was simulated through molecular dynamics and Monte Carlo sampling, and the electronic features of aggregates were modeled with plane-wave DFT. A semiconductor behavior for the featured compound in aggregated state, which compares well with systems applied on electronic devices, is predicted for the featured F-BODIPY.Graphical Abstract

Deposition of Carbon Nanotube Films on Polyamide and Polypropylene Substrates: A Computer Simulation Approach

In this work we study hydroxylated carbon nanotube (CNT) assembly on polyamide (PA) and polypropylene (PP) polymers activated by UV radiation from a theoretical and experimental perspective. Molecular computer simulation was done to understand the stable conformations and bulk properties (molecular dynamics) of the polymers before and after exposure to UV radiation at the molecular level. Our experiments suggest that PA presents more -OH active groups, producing a more hydrophilic surface, whereas PP exhibits less potential UV activation. These results suggest that it is possible a facile covalent functionalization method to tune organic polymer surface properties through SWCNT anchoring for nanotechnological applications requiring defined surface roughness and chemical functionality on inexpensive polymers.