Tinca Buruiana

Synthesis and characterization of some polyurethane cationomers with photochromic azoaromatic groups

Polyurethane cationomers based on polytetramethylene oxide, 4,4 0 -dibenzyldiisocyanate and N,N 0 -bis(b-hydroxyethyl)piperazine quaternized with methyl iodide were prepared. Using an ionic exchange reaction between this polycation and 3( p-oxyazobenzene)-propanesulfonic acid sodium salt, two azo-cationomers bearing chromophoric groups as counterions of ammonium quaternary structure were reported. The photochromic behavior of the above mentioned polycations in polymer solution as well as in thin films exposed to UV irradiation was discussed by comparison with other polycations having an azo dye (methyl orange) in the same hard segment. The increase of azo photochromic group concentration into polymer chains leads to a decrease in the isomerization rate. ” 2000 Elsevier Science Ltd. All rights reserved.

Synthesis of polyetherurethane cationomers with anthraquinone structure

Abstract An anthraquinone monomer, 1,4-bis-(β)-iodopropionyloxy)-9,10-anthraquinone was obtained by the condensation of 1,4-dihydroxy-9,10-anthraquinone with β-chloropropionyl-chloride, followed by an exchange reaction with potassium iodide in the presence of acetone. This derivative was used to synthesize polyetherurethane cationomers by two-step Menschutkin reaction. The resulting ionenes had ammonium quaternary groups content between 98.8 and 149.6 meq/100 g polymer and the quantity of anthraquinone units in polymeric chains was between 29.8 and 45.2 wt.% polymer, respectively. The tensile and thermal properties are similar to other elastomeric polyurethanes.These anthraquinone polyurethane colorants could be useful for coloring a wide variety of products such as fibers, films, coatings, paints or inks.

Synthesis, Evaluation and Preliminary Antibacterial Testing of Hybrid Composites Based on Urethane Oligodimethacrylates and Ag Nanoparticles

A series of urethane dimethacrylates differing structurally by the nature of the spacer (PTHF, PCL, PEG) and the presence or absence of the carboxylic acid groups was synthesized via an isocyanate route frequently encountered in ionomer chemistry. 1H-NMR and FT-IR spectroscopy confirmed the structure of the macromers. Subsequently, the progress of photo-polymerization of all dimethacrylates under UV irradiation was investigated by FT-IR spectroscopy and photo-DSC with respect to conversion and polymerization rate using Irgacure as an initiator. The results of spectroscopic analysis suggested the lower reactivity of some non-carboxylic analogues during the formation of cross-linked polymers, the degree of conversion depending on the structure and viscosity. Photo-polymerization may provide many advantages for incorporating silver nanoparticles (2.5 wt%) into macromers in order to obtain hybrid nanocomposite films with controllable thickness and hydrophobicity. Combined analyses of UV spectroscopy and transmission electron microscopy confirmed the existence of nanosized silver (mean diameter 12 ± 0.7 nm) uniformly distributed in the polymer matrix. Preliminary results concerning the antibacterial activity of some composite films (thickness approx. 24 μm) showed that the obtained nanomaterial could have an excellent bactericidal effect and effectiveness in reducing bacterial growth (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923).

Photopolymerization experiments and properties of some urethane/urea methacrylates tested in dental composites

Hydrophobic silyl-urea/urethane methacrylates (UHM-1, UHM-2) and a modified BisGMA derivative (BisGMA-UMA) were synthesized and used as photopolymerizable co-monomers in the preparation of dental composites, besides other urethane dimethacrylates containing oligoethylene oxide segments and carboxylic groups. The homo- and copolymerization behaviour of the synthesized monomers were investigated by FTIR spectroscopy using camphorquinone (CQ) and 4-(dimethylamino)-phenylacetic acid (DMPheAA) as a photoinitiating system, as well as by photo-DSC. The first hybrid monomethacrylate, N-(methacryloyloxyethyl-N’-diethoxymethylsilylpropyl)-urea showed the highest value for the maximum polymerization rate (0.117 s−1) followed by BisGMA analogue (0.085 s−1) and N-methacryloyloxyethyl-N’-bis(triethoxysilylpropylcarbamoyloxyethyl)-urea (0.069 s−1), whereas the degree of conversion decreased from 75.1% (UHM-2) to 41.6% (BisGMA-UMA). Polymerization shrinkage (PS) measured by picnometry for the mixture BisGMA-UMA/TEGDMA (4.78 vol.%) was lower than that exhibited of the control organic matrix BisGMA/TEGDMA (6.85 vol.%) at the same dilution. The addition of one of the obtained monomers into a mixture based on urethane oligomers led to a polymerization shrinkage varying between 8.33 and 6.97 vol.%. A number of properties of the composites formulated with our urethane methacrylates, a urethane dimethacrylate, BisGMA, and glass filler (Zr/Sr glass, quartz, and diatomite) were also determined including the surface damage caused by the Vickers indentation to establish their utility in dentistry.

Polycinnamates and Block Co-polymers Prepared by Atom Transfer Radical Polymerization and Microwave Irradiation

Homo-polymers of 2-cinnamoyloxyethyl methacrylate (PCEMA) and block co-polymers with methyl-methacrylate (MMA) synthesized via copper(I)bromide/pentamethyldiethylentriamine-mediated atom transfer polymerization (ATRP) and microwave irradiation, under homo(co)polymerization conditions, are reported. Method 1 led to homo-polymers with relatively low molecular weight (PCEMA-1: 5100; PCEMA-2: 25 000), while the second method offered polymer of 100 000 average molecular weight (PCEMA-3), the polymerization being completed within 60 min. Two di-block co-polymers, poly(2-cinnamoyloxyethyl methacrylate-block-poly(methyl methacrylate)) ((PCEMA-b-PMMA)-1, (PCEMA-b-PMMA)-2) with 0.33 and, respectively, 0.5 molar fraction of photo-cross-linkable PCEMA were also prepared and utilized for this study. Subsequent gel-permeation chromatography (GPC) measurements on block co-polymers have indicated molecular weights of 24 000 and 45 700, respectively. In addition, structural characteristics for all photo-polymers were determined by FT-IR, 1H-NMR, UV-Vis spectroscopy, AFM and SEM/ESEM measurements. Photochemistry in thin polymeric films suggested that UV irradiation is accompanied by an insolubilization of the film caused by the transformation of cinnamate moieties and the formation of intermolecular cross-links, with important effects on the morphology. As expected, it was found that by electrospinning the above photo-polymers produced electrospun fibers of small diameter.

Synthesis and characterization of novel polyurethane cationomers with dipeptide sequences and alkylammonium groups

A synthetic approach to polyurethane cationomers containing S-pyroglutamyl-S-glutamic acid dipeptide (S-PyGlu-S-Glu) and alkylammonium groups is presented. Two segmented polycations, based on polycaprolactone diol, isophorone diisocyanate and dipeptide together with N-methyldiethanolamine, subsequently quaternized with dodecylbromide, were synthesized and characterized by IR spectroscopy, GPC, DSC and reduced viscosity measurements. Such polycations exhibited excellent film forming properties and their soft elastomeric nature provides adequate physical properties. Optical rotation varying from +10 (monomer) to -15 (polycation) could be associated with a configuration pertubation through the asymmetric carbon atoms of glutamic residues. Susceptibility of the cationic surface to heparinization and then to blood-polymer interaction suggested an anticoagulant activity of the heparinized polymeric films.

Polyurethane cationomers containing anthryl and nitroaromatic chromophores

Polyurethane cationomers bearing anthryl and o, p-nitroaromatic photoactive groups have been synthesized. Their photochemical behavior was studied by electronic absorption spectroscopy and viscosity measurements. It was found that the photosensitivity of the polyurethane cationomers is enhanced by incorporation of the nitroaromatic chromophore.

Synthesis and characterization of acid polyurethane–hydroxyapatite composites for biomedical applications

This article aims to optimize the synthesis parameters and to establish the appropriate value of pressure for the design of polyurethane/hydroxyapatite organic matrix composites with an enhanced thermal and chemical stability. Strong interactions between Ca2+ ions and COO− groups are favoured at 60 atm. For the first time, the potential of polyurethane/hydroxyapatite material to be used as synthetic scaffold for bone cancer diagnosis was tested. The ability of polyurethane/hydroxyapatite coatings to be used as substrates for N2a cells attachment was studied using inverted optical microscopy. N2a cells presented a high birefringence and projected small prolongations of the soma comparable to control conditions, thus indicating the healthy state of the cells seeded on the composite substrates, especially in the case of composites prepared at 60–80 atm.

Elastomeric azo-polyurethanes containing fluorescent pyrene and their photo activity

Two bichromophoric polyetherurethanes with a small number of pyrene rings on the quaternary ammonium groups and photoisomerizable azobenzene chromophore attached to the soft (AzPUC-Py1) or hard segment (AzPUC-Py2) of the polymeric backbone were synthesized and characterized. The effect of polymer structure on the trans–cis and cis–trans photo(thermo)isomerization of azobenzene in thin films induced by UV light (λ = 365 nm) was investigated using UV spectroscopy, and in every case the quality of sensitizer of the pyrene was not evidenced. Moreover, a better photochromic response in the film containing azobenzene in the polyether component compared to that induced of the same chromophore in the hard segment was registered. Properties in the solution and thin films were then examined in relation with the fluorescence of pyrene molecule excited at λ exc = 335 nm. Results of the fluorescence study accompanied of a fluorescence quenching through N,N-diethylaniline (DEA) sustain that these polymers could be used for the detection of amines up to a concentration of 1.57 × 10−3 mol/l (AzPUC-Py1) and 3.14 × 10−3 mol/l (AzPUC-Py2), respectively, in DMF solution. Compared to the polymer solution, in the polymer film exposed to DEA-saturated vapors about 30% monomer fluorescence quenching was found after 90 min.

Polyurethanes based on dihydroxamic acids. Synthesis, chemical characterization, and biological activity

A series of segmented polyurethanes based on polyethylene oxide/polycaprolactone diol, isophorone diisocyanate, and dihydroxamic acids were synthesized and characterized. Biocompatibility and antitumoral activity were in vivo tested on Wistar male rats and Wistar rats affected with Walker 256 carcinosarcoma, respectively. The effect of dihydroxamic acid structure on the biological properties was determined. A better antitumoral response of the polyurethanes containing aliphatic dihydroxamic segment compared with those which resulted using terephthaloyl dihydroxamic acid was evidenced. With increasing polymer chain polyethylene oxide content the antitumoral activity was also enhanced. Some attempts on the in vitro biodegradation of above polyurethanes were also performed.