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

Selective Activation of C=C Bond in Sustainable Phenolic Compounds from Lignin via Photooxidation: Experiment and Density Functional Theory Calculations

Lignocellulosic biomass can be converted to high-value phenolic compounds, such as food additives, antioxidants, fragrances and fine chemicals. We investigated photochemical and heterogeneous photocatalytic oxidation of two isomeric phenolic compounds from lignin, isoeugenol and eugenol, in several nonprotic solvents, for the first time by experiment and the density functional theory (DFT) calculations. Photooxidation was conducted under ambient conditions using air, near-UV light and commercial P25 TiO2 photocatalyst, and the products were determined by TLC, UV-Vis absorption spectroscopy, HPLC-UV and HPLC-MS. Photochemical and photocatalytic oxidation of isoeugenol proceeds via the mild oxidative "dimerization" to produce the lignan dehydrodiisoeugenol (DHDIE), while photooxidation of eugenol does not proceed. The DFT calculations suggest a radical stepwise mechanism for the oxidative "dimerization" of isoeugenol to DHDIE as was calculated for the first time.

Adhesive Materials Utilizing a Thymine-Adenine Interaction and Thymine Photodimerization

A cross-linking reagent having two adenine units was mixed with polymers bearing thymine units to form adhesive materials utilizing both intermolecular hydrogen bonding and in situ formation of covalent bonds. In the case of 58 mol % of adenine units relative to thymine units, formation of intermolecular hydrogen bonds because of a thymine-adenine interaction was observed at room temperature using FT-IR. The peel strength became weak with heating above 60 °C, indicating breakup of intermolecular bonds between thymine and adenine units. On the other hand, UV-vis spectral measurements showed that heating at 80 °C with 254 nm light irradiation facilitated the photodimerization reaction between thymine units even in the presence of adenine cross-linking reagents. This result was consistent with a large value for the peel strength (6.5 N/10 mm) after the dual treatment, heating at 80 °C with 400 mJ/cm² of UV irradiation.

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.

Thymine modified amphiphilic biodegradable copolymers for photo-cross-linked micelles as stable drug carriers

A photo-cross-linked micelle is synthesized via photodimerization of thymine moieties fabricated from amphiphilic block copolymers (mPEG-b-P(LA-co-MPT). The crosslinking behavior is monitored by UV-Vis spectra and (1) H NMR. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that cross-linked micelles had smaller sizes than their uncross-linked precursors. In vitro studies reveal that cross-linking of the micelle cores results in a slow drug release and faster cellular uptake in comparison with uncross-linked ones in MCF-7 and Hela cells. Moreover, the paclitaxel (PTX)-loaded core-cross-linked micelles exhibit similar anticancer efficacy as free PTX. This work provides a convenient tool for designing a more stable structure in the blood circulation to realize a controlled drug delivery.