Evaluation of photo-induced crosslinking of thymine polymers using FT-IR spectroscopy and chemometric analysis

The photo-induced immobilization of 4-vinylbenzyl thymine (VBT) and 4-vinylbenzyl triethyl ammonium chloride (VBA) copolymers has been investigated with the aid of grazing-angle specular-reflectance FT-IR spectroscopy. As irradiation time increases, changes in the structure of pendent thymine groups in the copolymer due to the crosslinking process result in shifts of the copolymer network’s vibrational frequencies, as well as changes in numerous IR band intensities. In this work, chemometric methods have been applied to the FT-IR data obtained while monitoring the time evolution of curing of VBT-VBA copolymers of varying composition. The spectral data obtained with FT-IR normally provide information only about the degree of conversion of the reactants in the final product but there is no knowledge about how many compounds are involved or how they evolve over time. The use of the so-called Multivariate Curve Resolution-Alternating Least Squares allows the sequential estimation of the contribution to the signal due to the different species in the matrix data.Fil: Bortolato, Santiago Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Thomas, Katelyn. Simmons College; Estados UnidosFil: Mcdonough, Kristin. Simmons College; Estados UnidosFil: Gurney, Richard. Simmons College; Estados UnidosFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Photo-induced curing of thymine-based bioinspired polymers. A chemometric analysis

The curing process of new materials based on styrene monomers functionalized with thymine and charged ionic groups was studied using UV-vis spectroscopy in combination with chemomet-ric models. The effect of the copolymer molecular weight on the immobilization point was analyzed. The evolution of the curing process of the copolymer (4-vinylbenzyl) thymine (VBT) -vinylbenzyl triethyl ammonium chloride (VBA) involved three species, which absorb in the spectral region analyzed. The contributions of each species to the total signal at each irradiation time were determined, and the ki-netic constant of the crosslinking reaction was esti-mated. The study allowed evaluating the consistency of the chemometric decomposition, obtaining a rea-sonable correlation between the frequency spectra and the time evolution calculated with the algorithm. The chemometric analysis showed to be a powerful tool to provide complementary information on photo-induced immobilization of VBT-VBA films, which is crucial for developing new environmentally benign materials and new energy-saving methods.Fil: Bortolato, Santiago Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Barbarini, Alejandro Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Benitez, R. M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Salta. Instituto de Investigación para la Industria Química (i); Argentin

Energy and Electron Transfer Quenching of Porphyrins by C60

Energy- and electron-transfer from porphyrins in the triplet excited state to C60 in toluene and benzonitrile has been studied with Fourier transform EPR (FT-EPR). Pulsed-laser excitation of the systems magnesium tetraphenylporphyrin (MgTPP)/C60 and free-base octaethylporphyrin (OEP)/C60 in toluene gives rise to a resonance peak from C60 triplets (3C60) generated primarily by the energy-transfer process 3MgTPP (3OEP) + C60 -> MgTPP (OEP) + 3C60 as evident from the emissive spin polarization of the 3C60 signal observed at early times. No FT-EPR signals from redox products could be detected. In benzonitrile, triplet energy transfer from 3MgTPP or 3OEP to C60 is a minor process. In this polar solvent photoexcitation of MgTPP/C60 produces FT-EPR spectra with signal contributions from MgTPP+ and C60- in addition to the 3C60 resonance. From the spin polarization and time profile of the signal from the anion radical, it can be deduced that the primary route of electron transfer is oxidative quenching of the porphyrin triplets, 3MgTPP (3OEP) + C60 -> MgTPP+ (OEP+) + C60-. The reduction in 3C60 lifetime indicates that C60- is generated as well by the reductive triplet quenching reaction 3C60 + MgTPP (OEP) -> C60- + MgTPP+ (OEP+).Fil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: van Willigen, H.. UniVersity of Massachusetts at Boston; Estados Unido

An FT-EPR investigation of the anomalous CIDEP in photoreactions of chromone and chromone-2-carboxylic acid with alcohol induced by hydrochloric acid

The anomalous net absorptive CIDEP spectra observed in the photoinduced hydrogen abstraction reaction of chromone (CR) and chromone-2-carboxylic acid (CRCA) from 2-propanol with addition of hydrochloric acid (HCl) were investigated with FT-EPR. In neat 2-propanol, the spectra of the ketyl and 2-hydroxypropan-2-yl (2-HP) radicals display E*/A (low-field side emission and high-field side absorption, the asterisk denoting excess net polarization) or E/A type polarization, which is explained by the ST0 mixing radical pair mechanism and minor contributions of the triplet mechanism (TM). The addition of HCl to these systems gives the net absorptive CIDEP spectra, while the triplet states of CR and CRCA should have emissive polarizations. The analysis of the time developments of the EPR signals indicates that the radical generation rate increases with the increase of the HCl concentration, while the signal intensity of radicals does not increase. The net absorptive polarization might be explained by non-reactive quenching of the triplet by the spin-sublevel dependent back charge-transfer process in the intermediate exciplex.Fil: Ohara, Keishi. Ehime University; JapónFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: van Willigen, Hans. University of Massachusetts at Boston; Estados Unido

Crosslinkable micelles from diblock amphiphilic copolymers based on vinylbenzyl thymine and vinylbenzyl triethylammonium chloride

Polymeric micelles (PMs) composed of self-assembled amphiphilic block copolymers were synthesized from vinylbenzyl thymine (VBT) and vinylbenzyl triethylammonium chloride (VBA) exhibiting improved physical stability. Three diblock copolymers of different chemical compositions and similar molecular weights (polydispersities below 1.5) were obtained via nitroxide mediated radical polymerization. Critical micelle concentration (CMC) was determined by dye micellization method, the shift of the absorption peak of the anionic (EY) due to the interactions with non-assembled chains and auto-assembled copolymers was followed. Polymeric systems exhibited good stability revealing that a higher proportion of cationic monomers in the diblock reduce the CMC. Furthermore,after the core of PMs was photocrosslinked by UV irradiation, the CMC decreases notably. Kinetic release studies using EY dye as probe demonstrated that both, higher VBA ratios in the polymer and higher UV-irradiation, slow down the dye release.Fil: Barbarini, Alejandro Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); ArgentinaFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentin

Fluorescence spectroscopy and multivariate analysis as a greener monitoring tool: characterization of the curing kinetics of bioinspired polymers

The photo-induced curing kinetics of bioinspired copolymers vinylbenzyl thymine (VBT) and vinylphenyl sulfonatewas studied usingfluorescence spectroscopy in combination with multivariate analysis. Fluorescence spectroscopyenables a detailed description of the curing process of VBT copolymers in real time, combining selectivity,simplicity and sensitivity, without the need of sample pre-treatments, being an advantage from the green analyticalchemistry point of view. Two chemometric strategies were used to decompose the data matrix generated whilemonitoring the curing reaction, identifying the evolution of each species involved in the process in conjunctionwith the corresponding pure spectra. A comprehensive comparison between the developed approaches was made,clearly highlighting the advantages and disadvantages of both of them. The use of multivariate analysis applied tofluorescence spectroscopic data to study curing reactions have several advantages such as no sample pre-treatment,no sophisticated equipment requirement, reduced analysis time and use of non-toxic solvents, among others.Fil: Ledesma, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Quimicos Rosario. Universidad Nacional de Rosario. Facultad de Cs.bioquímicas y Farmaceuticas. Instituto de Procesos Biotecnológicos y Quimicos Rosario; ArgentinaFil: Bortolato, Santiago Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Boschetti, Carlos Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Quimicos Rosario. Universidad Nacional de Rosario. Facultad de Cs.bioquímicas y Farmaceuticas. Instituto de Procesos Biotecnológicos y Quimicos Rosario; Argentin

Second order multivariate curve resolution of Fourier Transform Infrared Spectroscopic data of the photo-induced crosslinking of thymine functionalized polymers

A meaningful characterization of the photo-induced curing process of materials based on styrene monomers functionalized with thymine and charged ionic groups was accomplished using FT-IR spectroscopy in combination with second-order multivariate calibration algorithms. The polymer composition as well as the irradiation dose effects on the photo-crosslinking of copolymer films was experimentally determined. Each FT-IR absorption spectra was decomposed into the contribution of individual species by means of chemometric algorithms. A second-order strategy involving a three-way array for each sample and analyzing all arrays simultaneously was used. Temperature and solvent frequently have a strong influence on the FT-IR peak producing shifts and trilinearity lost. A new methodology to properly pre-align the spectroscopic matrix data is used based on the decomposition of a three-way array via a suitably initialized and constrained PARAFAC model. The chemical reaction mechanism describing the underlying process in terms of identifiable steps was determined. Associated key parameters and equilibrium rate constants that characterize the interconversion and stability of diverse species were predicted. Additionally, it was possible to quantify all the species even in the presence of a non-calibrated compound.Fil: Bortolato, Santiago Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: McDonough, Kris. Simmons College. Department of Chemistry and Physics; Estados UnidosFil: Gurney, Richard W.. Simmons College. Department of Chemistry and Physics; Estados UnidosFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentin

Application of thymine-based copolymers in the quantification of organic pollutants in water by sensitized fluorescence

Bio-inspired copolymers based on thymine can interact with certain organic molecules and therefore they can be used as organized media or as optical sensors for analytical determinations. Particularly, the thymine-based copolymers have a high affinity for benzo(a)pyrene (BaP) and pyrene (Pyr), two main persistent organic pollutants in water. In the present work, such interaction is applied for the development of a simple analytical method based on fluorescence enhancement of BaP and Pyr. Since BaP and Pyr fluorescence spectra are strongly overlapped, a multivariate analysis of the data is proposed. The selectivity of the method was achieved through a parallel factors analysis (PARAFAC) of excitation-emission fluorescence matrices. The method performance was tested by simultaneous determination of BaP and Pyr in water samples, without pre-concentration steps or full chromatographic resolution. Studies of recovery for both analytes added to tap and surface waters were done, obtaining results in the order of 87–115%. The analysis was performed in the presence of additional species whose signals overlap with those of the analytes. In all cases, the calculated analytical figures of merit were compared with those obtained by the reference chromatographic method. In addition, a comparison of our method with the reference one is made based on the calculation of their respective eco-scales. The quality of the achieved results indicates that a second-order advantage was reached, while our method represents a greener alternative than the reference chromatographic methodology.Fil: Ledesma, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; ArgentinaFil: Boschetti, Carlos Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Procesos Biotecnológicos y Químicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Procesos Biotecnológicos y Químicos Rosario; ArgentinaFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Bortolato, Santiago Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Departamento de Matemática y Estadística; Argentin

Influence of pH and salt on the photocrosslinking in polyelectrolyte thymine-containing films

Photocrosslinking of thymine‐based water‐soluble polymer films was investigated at varying preparation conditions. Adding salt or decreasing the pH of the solution from which the films were cast resulted in the decreased efficiency of photoimmobilization, while increasing the pH was found to increase the photoimmobilization efficiency. A mechanistic rationale for the observed effects is proposed.Fil: Trakhtenberg, Sofia. University of Massachusetts Lowell; Estados UnidosFil: Kumar, Ramya. University of Massachusetts Lowell; Estados UnidosFil: Bianchini, Jason. University of Massachusetts Lowell; Estados UnidosFil: Thor, Savin. University of Massachusetts Lowell; Estados UnidosFil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. University of Massachusetts Lowell; Estados UnidosFil: Warner, John. University of Massachusetts Lowell; Estados Unido

Photosensitization of Bioinspired Thymine-Containing Polymers

Here, we report a sensitization study on a family of water-soluble photopolymers based on thymine. The goal of this study was to determine whether the presence of sensitizer molecules would promote photocrosslinking/immobilization of the polymers using low-energy irradiation (520 nm) as compared to the UV irradiation (approximately 280 nm) necessary for the standard photoinduced process to take place. With the aid of Eosin Y Spirit Soluble (EY) as a sensitizer, water-soluble polystyrene copolymers of vinylbenzylthymine-vinylbenzyltriethylammonium chloride (VBT-VBA) were immobilized after exposure to visible irradiation. By exciting the sensitizer molecule in the presence of VBT copolymers at a wavelength where absorption by the latter does not occur, the triplet state of the sensitizer is generated in high yields, and consequently, polymer photocross-linking takes place. UV-vis spectroscopy has been used to study the effect of irradiation dose, copolymer composition, and sensitizer concentration on the photoreactivity of VBT polymers. These studies demonstrate the feasibility of using Eosin Y as a sensitizer to achieve the thymine photodimer formation, resulting in immobilization of VBT-VBA-EY films on PET substrate. This provides complementary information on photoinduced immobilization of VBT-VBA films that are crucial for developing new classes of environmentally benign materials and new energy-saving methods.Fil: Martino, Debora Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Reyna, Dalila Luz. Universidad Nacional del Litoral; ArgentinaFil: Estenoz, Diana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Trakhtenberg, Sofía. Warner Babcock Institute for Green Chemistry; Estados UnidosFil: Warner, John. Warner Babcock Institute for Green Chemistry; Estados Unido