Andreea L. Chibac

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).

New acid BisGMA analogs for dental adhesive applications with antimicrobial activity.

OBJECTIVE To achieve bisphenol A glycerolate dimethacrylate (BisGMA) analogs with reduced viscosity to be used in the formulation of dental adhesives containing biocidal components. METHODS A series of low-viscosity BisGMA derivatives (η: 39-12Pas) modified with 30, 60 and, respectively 80mol% carboxylic acid units were synthesized and characterized. Hydrogen bonding interactions in our monomers, the photopolymerization behavior and implicitly the conversion degree (DC) for some experimental adhesive formulations containing acid-modified BisGMA, commercial BisGMA (only in F1-F3), triethyleneglycol dimethacrylate and 2-hydroxyethyl methacrylate were examined by FTIR spectroscopy. The water effects on the photocrosslinked networks together with the flexural strength/modulus were also investigated. The adhesive penetration into the dentin surface was surveyed by SEM analysis, and the antimicrobial activity triggered by the incorporation of 0.5wt% AgNO3, 10wt% zinc methacrylate or 1wt% triclosan methacrylate in selected adhesive formulations on the growth of Streptococcus mutans and Candida albicans strains was evidenced. RESULTS The contribution of the hydrogen bonding interactions was found to be lower in BisGMA derivatives than in non-modified BisGMA, and the DC varied between 56.5 (F6) and 83.7% (F1) compared with a control formulation based on BisGMA:TEGDMA (DC=58.2%). The flexural strength and flexural modulus varied in the range 33.7MPa (F6)-54.4MPa (F8)MPa and 0.64 (F6)-1.43 (F8)GPa, respectively. SEM observation of adhesive-dentin interface revealed the formation of resin tags for the carboxyl-containing adhesive, while for the control adhesive they are hardly formed. Also, the microorganism development was inhibited, the proposed materials displaying antimicrobial activity. SIGNIFICANCE The experimental formulations based on carboxyl-functionalized BisGMA exhibit a similar or even improved behavior over control sample, suggesting their potential applicability as antimicrobial dental adhesives.

Tuning the size and the photocatalytic performance of gold nanoparticles in situ generated in photopolymerizable glycomonomers

Polymer nanocomposites containing gold nanoparticles (Au NPs) in situ photogenerated during the UV-curing process were prepared starting from methacrylated glycomonomers with α-D-glucofuranose or D-mannitol structural units, other mono(di)methacrylates and AuCl3. The formation of Au NPs inside the polymer matrix was evidenced through UV-vis, TEM and XRD analyses, the mean size of the spherical particles being around 33 nm. By adding methacrylates functionalized with carboxylic, quaternary ammonium or thiol groups (MA-COOH, MA-N+, MA-SH) in each formulation, the mean size of gold nanoparticles in the hybrid films (purple/dark-blue, red, green) decreased from 6.4 nm to 1.5 nm (for those stabilized by a gold–thiol bond). The catalytic activity was tested for the photodegradation of methylene blue (MB) and methyl orange (MO) in aqueous phase under visible irradiation conditions, and the catalytic performance of the resulting hybrid films was improved by the size decrease of the Au NPs. The hybrid films prepared with 30 wt% MA-SH were more active than the samples with 10 wt% thiol methacrylate. Thus, the percentage degradation with nanosized Au NPs and 30 wt% photopolymerized MA-SH was about 98% in MB and 94% for MO (after 100 min of visible irradiation). Finally it was proved that the hybrid polymeric films can be reused as photocatalysts with high performance for the removal of dyes from contaminated wastewater.

Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3

Polymer nanocomposites containing titanium oxide nanoparticles (TiO2 NPs) combined with other inorganic components (Si–O–Si or/and γ-Fe2O3) were prepared by the dispersion of premade NPs (nanocrystalline TiO2, TiO2/SiO2, TiO2/Fe2O3, TiO2/SiO2/Fe2O3) within a photopolymerizable urethane dimethacrylate (polytetrahydrofuran-urethane dimethacrylate, PTHF-UDMA). The physicochemical characterization of nanoparticles and hybrid polymeric composites with 10 wt % NPs (S1–S4) was realized through XRD, TEM and FTIR analyses. The mean size (10–30 nm) and the crystallinity of the NPs varied as a function of the inorganic constituent. The catalytic activity of these hybrid films was tested for the photodegradation of phenol, hydroquinone and dopamine in aqueous solution under UV or visible-light irradiation. The best results were obtained for the films with TiO2/Fe2O3 or TiO2/SiO2/Fe2O3 NPs. The degradation of the mentioned model pollutants varied between 71% and 100% (after 250 min of irradiation) depending on the composition of the hybrid film tested and the light applied (UV–visible light). Also, it was established that such hybrid films can be reused at least for five cycles, without losing too much of the photocatalytic efficiency (ca. 7%). These findings could have implications in the development of new nanocatalysts.

Synthesis of new photoactive urethane carbohydrates and their behavior in UV or femtosecond laser-induced two-photon polymerization

Abstract Three methacrylated glycomonomers (CMA-1–3) were synthesized, characterized, and photocrosslinked in hydrophilic conetworks. The UV photobehavior of monomers was evaluated through FTIR spectrometry using Irgacure 819/Irgacure 2959 as photoinitiator, and the results showed that Irgacure 2959 is a better photoinitiator, the conversion degree (DC) varying in the range of 69–89.2% and the maximum rate of polymerization () being ~10 s−1. The addition of poly(ethylene glycol) dimethacrylate (PEG-DMA) or benzophenone macromer (BP-UDMA) as co-monomer improved the and DC (up to 100% after 300 s of irradiation in the latter). Specific analysis (gel fraction, water uptake, morphology) of the photopolymerized networks A1–A3 (CMA-1–3/PEG-DMA) and B1–B3 (CMA-1–3/BP-UDMA) demonstrated that B1–B3 films have interconnected inner pores, with irregular shapes and different sizes. The grid structures created through the two-photon polymerization of B1–B3 formulations in the presence of Irg819 are clearer and have a controlled porosity, of relevance for promising bioapplications.