Ana-Maria Albu

Preparation and Characterization of Polar Aniline Functionalized Copolymers Thin Films for Optical Non-Linear Applications

This paper presents a study of two monomeric structures containing functional groups with different electronegativities [NH/NH-NH and NO2] and two different polymeric structures prepared by the copolymerisation of maleic anhydride and methylmethacrylate/maleic anhydride and vinyl benzyl chloride, and subsequent functionalization with 2,4 dinitroaniline. Thin films have been prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and UV-VIS, FTIR, Raman and Photoluminescence Spectroscopy have been used to comparatively investigate the properties of the synthesised compounds. We have evidenced the second harmonic emission (SHG), process sustained by the asymmetry of the chemical structure, which is correlated with the crystallization in non-centrosymmeric structures.

Synthesis and characterization of some polymers with applications in non-linear optics II. Copolymerization of styrene with some monomers containing azo-dyes

The present work describes the evolution of binary copolymerization of a monomer containing an azoic chromophore with styrene. Reactivity ratios have been computed using several methods. The sequential analysis suggests a favourable case for the use of azoic structures in electro-optical applications.

Synthesis and characterization of some polymers with applications in non-linear optics I. Polymerization of styrene and methyl methacrylate in the presence of coloured comonomers

New coloured monomers containing azoic and azomethinic chromophores attached on styrenic or methacrylic structures are typical for non-linear optics applications; the present work describes the possibility of their chemical incorporation in classical polymer matrices. It has been shown that the maximal content of coloured monomers in the copolymer chain is influenced only by their intense activity towards chain transfer. The optical properties of the chromophore present in the coloured monomers are preserved after incorporation in the copolymer chain. Inhibition or retardation phenomena have not been noticed during all copolymerization tests performed.

Polymer Architectures Based on Oxazoline Monomers

Nonaqueous dispersion copolymerization of 2-isopropenyl 2-oxazoline (IPRO) with methyl methacrylate (MMA) and chloromethylstyrene (CMS) was studied. The resulting copolymers were analyzed with FT-IR and FT-NMR techniques. The morphologies and average diameter were investigated for the characterization of the resulting particles. When the comonomer was MMA the particle size was dependent upon the molar ratio MMA/IPRO in copolymer. MMA content in the resulting copolymers is influenced by the type of stabilizing agent. Narrow size distribution was obtain for copolymer rich in IPRO. When CMS was the commoner, polymerization occurred via two mechanisms: radicalic and cationic with preference for the last one.

Kinetics of Free Radical Polymerization of N-Substituted Amides and Their Structural Implications

Two N-substituted amides (N-acryloyl morpholine and N-methyl-N-vinylacetamide) were polymerized in different solvents using radical initiator. The tacticity of obtained polymers was determined by 400 MHz 1H-NMR and 13C-NMR. At a given temperature, the syndiotacticity increased with increasing the solvent polarity. This solvent effect may be related to the hydrogen bonding interaction among solvent, monomer, and/or growing species. A peculiar aspect regards the steric hindrance at the nitrogen atom.

Influence of Dicyclopentadiene Co-Polymers on the Hardening Processes and Properties of Portland Cement Composites

Dicyclopentadine (DCPD) polymers can be used for the manufacture of self healing materials due to their ability to form in the presence of a catalyst a highly cross-linked polycyclopendiene. The DCPD polymers selected for this work contain also another constituent sequence (maleic anhydride), therefore in this paper we assess also the possibility to use it for a potential self healing process. In this paper is presented the influence of two types of (DCPD) co-polymers based on maleic anhydride copolymers on the hardening processes and main properties of portland cement pastes and mortars, as a first step in the development of a self-healing cementitious composite. The properties (mechanical strengths and volume variations) of the cementitious composites with DCPD co-polymers are influenced by the chemical structure of the obtained compounds and curing medium (dry or humid air). The mortars with AM (maleic anhydride/dicyclopentadiene co-polymer) did not develop any mechanical strength due to an important swelling phenomenon determined by the hydrolysis of anhydride groups and sterical modifications in chain structures. The presence of APA (AM copolymer modified with p-amino phenyl acetic acid) decreases the compressive strengths but has a less important effect on the flexural strength. The APA polymer-cement interaction consists in a chelatization process involving the nitrogen atoms and hydrogen bonding of carboxyl groups providing, in this case, a good cohesion of the composite material. For both polymers a delay in cement hydration was noticed at early ages as well as the formation of organo-mineral phases.

The effects of UV irradiation in azo-derivatives

From all type of external stimuli the light rays are most commonly used because it involves only photochemical processes easily to control. One of the most studied of photochemical processes is photoisomerization groups, in particular the azobenzene groups. The azobenzene and his derivatives, known for Z(sin)-E(anti) reversible photoisomerization properties, have been extensively used as functional groups to synthesize various photosensitive compounds. The UV irradiation at different time of modified maleic anhydride - styrene copolymers with azo dye solutions were with UV light to increase the rate of Z(sin)-E(anti) isomerisation. The changes in the spectral absorption domain for azo compounds, a decrease in optic absorbance after irradiation, with a predisposition to come back at primary value was made with SECOMAMS750 UV–Vis spectrophotometer.

Synthesis and characterization of photochromic polymeric materials

The reversible photoisomerization and thermal isomerization of azobenzene-based groups covalently bound to the polymers systems were investigated in the solution. The thermal Z-E isomerization rate could be obtained by varying the substituent of azobenzene or copolymer composition. This change of orientation of azobenzene groups may be suitable for optical storage. In principle the orientation change is permanent, but it can be easily erased by heating, on which the original random orientation is largely restored.

Cellulose-Based Composites for Membranes by “In Situ” Radical Polymerization

Cellulose-containing composites based on copolymers of acrylic acid with styrene, 4-chloro-methyl-styrene and maleic anhydride were prepared for proton conducting membranes. The influence of the substrate on the copolymer composition as well as the copolymer/cellulose ratio on the basic properties of composite materials is discussed using the FT-IR, optical microscopy, SEM, TGA-DSC and conductivity measurements. Moderate water swelling (2–10%) of the synthesized membranes provided volume resistivities down to 1 × 105 Ω · cm, adequate for further processing as proton exchange membrane.

Copolymerization of the Pair Maleic Anhydride‐Dicyclopentadiene: II. Kinetics at Low Conversion

Kinetic investigations regarding the copolymerization of the pair maleic anhydride (MA)–di‐cyclo‐pentadiene (DCPD) are presented. It has been shown that copolymerization takes place mainly by cross‐propagation, implying both free monomers and charge transfer complexes (CTC) as well. In this case, homo‐propagation of MA, even minor, can no longer be overlooked; termination is due to a degradative transfer. A suitable kinetic model has been devised, on this basis; the proposed model has been checked against experimental measurements.