The new combinations of monomers presented in this work were evaluated in order to create an elastic material for potential application in soft tissue engineering. Thermoplastic elastomers (TPE) of trimethylene carbonate (TMC) with L-lactide (LLA) and 1,5-dioxepan-2-one (DXO) have been synthesized using a cyclic five-membered tin alkoxide initiator. The block copolymers were designed in such a way that poly(trimethylene carbonate-co-1,5-dioxepan-2-one) formed an amorphous middle block and the poly(L-lactide) (PLLA) formed semicrystalline terminal blocks. The amorphous middle block consisted of relatively randomly distributed TMC and DXO monomer units, and the defined block structure of the PLLA terminal segments was confirmed by 13C NMR. The properties of the TMC-DXO-LLA copolymers were compared with those of triblock copolymers based either on LLA-TMC or on LLA-DXO. Differential scanning calorimetry and dynamic mechanical analysis data confirmed the micro-phase separation in the copolymers. The mechanical properties of the copolymers were evaluated using tensile testing and cycling loading. All of the copolymers synthesized showed a highly elastic behavior. The properties of copolymers could be tailored by altering the proportions of the different monomers.

No abstract

No abstract

The copolymerization of 1,5-dioxepan-2-one (DXO) and -caprolactone, initiated by a five-membered cyclic tin alkoxide initiator, was performed in chloroform at 60°C. Copolymers with different molar ratios of DXO (25, 40, and 60%) were synthesized and characterized. 13 C NMR spectroscopy of the carbonyl region revealed the formation of copolymers with a blocklike structure. Differential scanning calorimetry measurements showed that all the copolymers had a single glass transition between Ϫ57 and Ϫ49°C and a melting temperature in the range of 30.1-47.7°C, both of which were correlated with the amount of DXO. An increase in the amount of DXO led to an increase in the glass-transition temperature and to a decrease in the melting temperature. Dynamic mechanical thermal analysis measurements confirmed the results of the calorimetric analysis, showing a single sharp drop in the storage modulus in the temperature region corresponding to the glass transition. Tensile testing demonstrated good mechanical properties with a tensile strength of 27-39 MPa and an elongation at break of up to 1400%. The morphology of the copolymers was examined with polarized optical microscopy and atomic force microscopy; the films that crystallized from the melt showed a short fibrillar structure (with a length of 0.05-0.4 m) in contrast to the untreated solution-cast films.

ABSTRACT:To increase their adhesion to silver, polyimide (PI) surfaces were modified by sulfonation reactions by means of different experimental procedures. The results of these modification reactions were analyzed in terms of the variation of the surface chemical composition examined by X-ray photoelectron spectroscopy. Longtime reactions were also followed by monitoring the increase in weight of the PI films. Changes in the total surface free energy were evaluated by contact angle measurements with the sessil drop method. The influence of the modification reactions on silver/PI adhesion was estimated by means of a 180°peeling test according to ASTM standards. Finally, the effect of chemical modification on film roughness was investigated by means of atomic force microscopy. The results obtained showed that a net improvement, that is, over the maximum rate according to the reference ASTM test, was attained via both the gaseous SO 3 and concentrated H 2 SO 4 procedures, with the latter procedure more effective in the presence of silver sulfate as a catalyst. However, the former was judged more convenient because of the low amount of reagents used and the simplicity of cleaning operations. Interestingly, optimum adhesion levels were attained after only very low contact times with all sulfonating agents, that is, after about 30 s. These results were compared with the effects on PI/silver adhesion of traditional etching procedures with KOH aqueous solutions at different temperatures. In this case, good adhesion was observed only after longer reaction times, that is, on the order of 1-2 min in the case of 1M KOH and 1 h in the case of 0.1M KOH.

No abstract

Keratinocytes and fibroblasts have been grown onto a series of triblock copolymers based on 1,5-dioxepan-2-one (DXO) and L-lactide (LLA). The molar ratio of DXO and LLA were varied in the copolymers. This resulted in different degrees of hydrophilicity, which in turn influenced the cell growth. On these surfaces, the morphological appearance of the cells with their cell movements and growth were investigated by means of scanning electron microscopy, time-lapse videomicroscopy and immunohistochemistry. All results clearly showed that the keratinocytes and fibroblasts adhered best to the most hydrophilic copolymers. A majority of the keratinocytes seeded on the most hydrophilic copolymer also presented a polarized morphology indicating a migration tendency. The cell growth onto these materials are interesting since a possible application for these unique materials is as polymeric membranes for guided cutaneous and/or periodontal tissue generation.

Aim. Comparative study of clinical efficacy and safety of antiviral drug triazavirin and umifenovir in the treatment of patients with acute respiratory viral infections and influenza. Methods. The study included 100 patients aged 18 to 65 years diagnosed with moderate acute respiratory viral infection. Group 1 included 34 patients receiving umifenovir 200 mg 4 times a day for 5 days, and comparison group included 32 patients who received triazavirin 1 capsule (250 mg) 3 times a day for 5 days. Group 3 (control group) included 34 patients not treated with antiviral therapy. Efficacy and safety of the studied antiviral drugs were evaluated based on clinical symptoms in the disease course and were confirmed by adaptive reactions of the organism. Results. Among patients receiving triazavirin, recovery time and fever, headache and catarrhal syndrome resolution time were less than among patients who received umifenovir. On triazavirin treatment with favorable tolerability, symptomatic medications (antipyretics) were discontinued, and the duration of their use was less, than in patients receiving umifenovir. Evaluation of clinical efficacy of umifenovir and triazavirin for the treatment of acute respiratory viral infections and influenza demonstrated that the drugs effectively reverse the main symptoms of the disease (p <0.05), reduce complications incidence (18.1±2.1% vs. 55.9±3.2%, p <0.05) and contribute to the stabilization of adaptive reactions of the organism in contrast to the results of patients not receiving etiotropic therapy (6.9±2.9% vs. 12.8±2.7, p <0.05). During the use of umifenovir by day 4 and during the use of triazavirin by day 3 intoxication and catarrhal syndromes had been reversed, while in case of the absence of antiviral therapy, 55.8% of patients had continuing intoxication and catarrhal symptoms. Conclusion. The results of the study allow defining umifenovir and triazavirin as the first line of defense against acute respiratory viral infections with good efficacy and tolerability of the drugs.