Florica Adriana Jerca

New side-chain azo-polymers for optical applications: synthesis and characterization

In this paper we report a series of side-chain polymers bearing a push-pull azo-moiety, from pseudo-stylbene type molecules. The azobenzene monomer is chemically incorporated through radical copolymerization in: poly(methacrylate), poly(styrene); and poly(oxazoline) matrices. The different classes of azo-polymers are discussed comparatively to one another from the point of view of: solubility, molecular weights, glass transition temperatures and thermal stability, chromophore contents, and as well as from the point of view of their spectral features.

Development and Characterization of Photoresponsive Polymers

Polymeric materials that respond to light stimulus represent an important research area in the field of biomaterials. Light-responsive biomaterials have received significant attention due to their ability to provide spatially and temporally control and their potential to be less invasive. In this book chapter, we highlight the exciting progress realized in the biomedical field in recent years on photoresponsive polymeric systems. More precisely, we discuss the rational design of photoactive compounds, the role they have in the photoresponsive systems, the underlying principles behind photoresponsive behavior, and the subsequent applications in the biomaterial field. We also present the progress made in the field of photopharmacology, photoregulated drug delivery, and bioimaging, emphasizing the advantages on the basis of different architectures such as micelles, hydrogels, nanoparticles, and photoresponsive supramolecular assemblies. Finally, analytical techniques used to characterize the photoresponsive materials are expound.

Smart polymeric gels

Abstract Smart polymeric hydrogels undergo reversible volume phase transitions that change their structures in response to external stimuli such as temperature, pH, light, mechanical, electrical, and analyte and have been used in diverse applications such as in controlled drug delivery, actuators, biosensors, and bioseparation. This chapter summarizes recent developments on smart polymeric hydrogels with focus on their synthesis, properties, and applications. At first, the most common methodologies for the synthesis of smart polymeric hydrogels based on synthetic polymers will be briefly discussed. Next, classification of smart polymeric hydrogels based on the stimuli and their controlling mechanism will be given. Finally, some potential applications and future perspectives will also be highlighted.

Photoresponsive behavior of azobenzene hybrid materials

The trans-cis-trans isomerization process for a series of azobenzene hybrid materials has been studied by UV-Vis spectroscopy. The photoisomerization process is mainly independent of the position and chemical nature of the substituents. The kinetics of the thermal back reaction for the azo-hybrids depend strongly on the chemical nature of the substituent and substitution pattern, with thermal relaxation rate constant ranging from 3.29×10-5 to 6.49×10-2 s-1. The photoresponsive properties can be tune up by changing substituent nature and position on the azo-chromophore. These photoresponsive hybrid materials are optimal molecules for storage data applications and for designing fast optical switching devices.

Investigations of molecular nonlinear optical polarizabilities of azobenzenes substituted with strong acceptor groups

In this paper, a detailed optical characterization of a series of 4-nitro/cyan, 2-nitro/cyan and 2,4-nitro/cyan substituted azobenzenes is carried out. The first-order hyperpolarizabilities of organic chromophores were determined by solvatochromic method. Different nonlinear optical behaviour is evidenced when the ortho position of an azo molecule is occupied by acceptor and donor substituents. An increase of first-order hyperpolarizability was noticed in the case of 2,4-disubstituted azobenzenes as compared to the monosubstituted ones. Solvent effect on the UV-Vis absorption spectra of azo-polymers was investigated using Kamlet-Taft multiparameter equation. Kamlet-Taft equation revealed that hydrogen bond acceptor properties and dipolarity/polarizability of the solvent have a significant contribution upon the solvatochromic behavior of azo-derivatives.