Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II) Ions

The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA) has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC) were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity decrease caused by oxidative system, indicating HA protection from degradation, SEC analysis suggested that some other mechanisms leading to the bucillamine transformations without the decay of the viscosity may come into a play as well. Nonetheless, the link between the reduction of chemiluminescence intensity and disappearance of the differential scanning calorimetry exotherm at 270 °C for fragmented HAs indicates a particular role of the bucillamine in preventing the decrease of HA viscosity

Influence of surface modification of carbon nanotubes on interactions with polystyrene-b-polyisoprene-b-polystyrene matrix and its photo-actuation properties

The influence of various surface modification of multiwalled carbon nanotubes (MWCNT) on preferential interactions with individual phases of the linear triblock copolymer polystyrene-b-polyisoprene-b-polystyrene (SIS) and the photo-actuation ability, reproducibility, and stability of the composite was investigated. The preferential interactions of MWCNT were achieved with covalent modification of MWCNT surface either with cholesteryl groups (MWCNT-chol) or with short polystyrene chains (MWCNT-PS). The specific interactions were investigated by dynamic mechanical analysis. The activation energy of glass transition of the polystyrene phase in the MWCNT-PS/SIS composite increased significantly compared with the neat SIS matrix, while the incorporation of MWCNT-chol resulted in selective increase of activation energy of glass transition of the polyisoprene phase. The best reproducible and stable photo-actuation behavior was obtained during irradiation of the composite containing low content of MWCNT-PS.* Slovak Research and Development Agency APVV. Grant Number: APVV-0109-10 * Centre of Excellence SAS for Functionalized Multiphase Materials * European Commission within 7th Frame Program. Grant Number: 228916Wiley Online librar

Mechanical and Electrical Properties of Styrene-Isoprene-Styrene Copolymer Doped with Expanded Graphite Nanoplatelets

The molecular dynamics of a triblock copolymer and of expanded graphite nanoplatelets were investigated. Composites were prepared using the solution technique. The effects of filler addition and of filler-matrix interactions were investigated using dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Only one relaxation was observed by DRS, which was associated with the relaxation of the main polymer chain. Both DRS and DMA demonstrated that the addition of the filler does not cause a significant change in either the temperature of the relaxation or its activation energy, which suggests the presence of weak interactions between the filler and matrix. The storage modulus of the composites increased with increasing filler content. The composite containing 8% filler exhibited a storage modulus increase of approximately 394% in the rubber area. Using the DC electrical conductivity measurements, the electrical percolation threshold was determined to be approximately 5%. The dielectric permittivity and conductivity in the microwave region were determined, confirming that percolating behavior and the critical threshold concentration

A tertiary amine in two competitive processes: Reduction of graphene oxide vs. catalysis of atom transfer radical polymerization

Electrically conductive graphene oxide-polystyrene hybrids (GO-PS) were prepared by reduction of graphene oxide (GO) in one step during covalent modification of graphene oxide surface using surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene. The reduction of the GO surface was proven by Raman spectroscopy, electrical conductivity measurements, thermogravimetric analysis and X-ray photoelectron spectroscopy. Electrical conductivity of the synthesized GO-PS particles increased in eight orders of magnitude, depending on the polymerization period. Detailed studies were performed to determine that the tertiary amine, such as N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA), used in SI-ATRP as a ligand complexing copper catalyst, was responsible for the GO surface reduction. It was shown that due to participation of PMDETA in reduction of graphene oxide, the ATRP in the presence of GO can proceed only above a certain PMDETA-GO ratio.Slovak Research and Development Agency APVV [APVV-0109-10]; Centre of Excellence SAS for Functionalized Multiphase Materials (FUN-MAT), Grant Agency VEGA [2/0151/12]; Centre of Excellence SAS for Functionalized Multiphase Materials (FUN-MAT), MNT-ERA. Net II [794]; European Regional Development Fund; Czech Republic [CZ.1.05/2.1.00/03.0111

Visualization of carbon nanotubes dispersion in composite by using confocal laser scanning microscopy

Nanocomposites of polystyrene-block-polyisoprene-block-polystyrene triblock copolymer (SIS) and various types of neat and polystyrene-modified carbon nanotubes (CNT-PS) were prepared and distribution of the CNT-PS throughout the polymer matrix was evaluated using confocal laser scanning microscopy (CLSM). The Nanoamor MWCNT-PS with highest thickness of 25-60 nm were readily visualized using both reflection mode without necessity of fluorescent labelling and fluorescent mode after addition of free dye to the nanocomposite. Visualization of Nanocyl MWCNT-PS with thickness of 8-18 nm and SWCNT-PS was achieved after covalent labelling of the CNT-PS with benzothioxanthene fluorescent dye. The CLSM can serve as a non-invasive method for evaluation of quality of dispersion of nanofillers on quite large area and at various depth of polymer film. © 2016 Elsevier Ltd. All rights reserved.50755038, DAAD, German Academic Exchange ServiceVEGA grant agency [2/0112/13]; Slovak Research and Development Agency APVV [APVV-14-0891]; SAS-MOST JRP [2014-9]; DAAD project [50755038]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504