Carlos Rodriguez Arza

Oxazine Ring-Related Vibrational Modes of Benzoxazine Monomers Using Fully Aromatically Substituted, Deuterated, 15N Isotope Exchanged, and Oxazine-Ring-Substituted Compounds and Theoretical Calculations

Polymerization of benzoxazine resins is indicated by the disappearance of a 960-900 cm-1 band in infrared spectroscopy (IR). Historically, this band was assigned to the C-H out-of-plane bending of the benzene to which the oxazine ring is attached. This study shows that this band is a mixture of the O-C2 stretching of the oxazine ring and the phenolic ring vibrational modes. Vibrational frequencies of 3-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-a) and 3-(tert-butyl)-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-t) are compared with isotope-exchanged and all-substituted compounds. Deuterated benzoxazine monomers, 15N-isotope exchanged benzoxazine monomers, and all-substituted benzoxazine monomers without aromatic C-H groups are synthesized and studied meticulously. The various isotopic-exchanges involved deuteration around the benzene ring of phenol, selective deuteration of each CH2 in the O-CH2-N (2) and N-CH2-Ar (4) positions on the oxazine ring, or simultaneous deuteration of both positions. The chemical structures were confirmed by 1H nuclear magnetic resonance spectroscopy (1H NMR). The IR and Raman spectra of each compound are compared. Further analysis of 15N isotope-exchanged PH-a indicates the influence of the nitrogen isotope on the band position, both experimentally and theoretically. This finding is important for polymerization studies of benzoxazines that utilize vibrational spectroscopy.

Dispersion and interaction of graphene oxide in amorphous and semi-crystalline nano-composites: a PALS study

The influence of dispersion and interaction of Graphene Oxide (GO) in semi-crystalline Polyhydroxy butyrate (PHB) and glassy amorphous Poly(tBP-oda) is explored by Positron Annihilation Lifetime Spectroscopy (PALS). The ortho-Positronium lifetimes which represent the main free volume hole size of both polymers are mainly affected by the large differences in internal stresses built up by the shrinkage of the polymers during their preparation, restricted by the platelet structure of GO. The ortho-Positronium intensities, which represent the ortho-Positronium formation probabilities, suggest a strong dependency of on the dispersion of the nano-particles and their aspect ratio.

Indole as a new sustainable aromatic unit for high quality biopolyesters

The aim of this research was to use indole as a new sustainable aromatic unit for polyesters. A series of new polyesters were synthesised by the polycondensation of an indole-based dicarboxylate and five potentially bio-based diols. The new polyesters are amorphous, have superior thermal quality, and can form clear transparent films.

New biobased non-ionic hyperbranched polymers as environmentally friendly antibacterial additives for biopolymers

The aim of this research was to develop new biobased non-ionic polymeric additives with significant bacterial inhibition and low leaching potential, so that they can be used to produce biopolymer materials for various applications such as biomedical devices, surgical textile, or food packaging. Two new non-ionic hyperbranched polymers (HBPs) were prepared by a facile solvent-free polymerization of an AB2-monomer derived from naturally existing molecular building blocks 2-phenylethanol, isatin, and anisole. The molecular structures and thermal properties of the obtained HBPs were characterized by GPC, NMR, FTIR, HRMS, MALDI-TOF, TGA and DSC analyses. Disk diffusion tests revealed that the two obtained HBPs showed more significant antibacterial activity against 9 different food and human pathogenic bacteria, compared with small molecular antibiotics. The maximal antibacterial effect of HBPs was achieved at 2 μg per disk (or 0.1 mg mL−1), which was significantly lower (∼1/15) compared to the linear antibacterial polymer chitosan. Such enhanced antibacterial properties can be attributed to the unique highly branched structures and effectively amplified functionalities of HBPs. Finally, the prepared HBPs were added into natural polymers cellulose and polyhydroxybutyrate (PHB), and the resulting biopolymer films showed no significant leakage after being merged in water for 5 days. This was in sharp contrast to the biopolymer films containing a small model compound, which leaked out significantly under the same conditions. To our knowledge, this is the first report on non-ionic bio-based dendritic macromolecules with significant bacteria inhibition and low leakage.