PREPARATION AND STUDY OF MECHANICAL PROPERTIES OF POLYLACTIC ACID/STARCH OLEATES BLENDS

Abstract In presented work, the blends composed from pure polylactic acid (PLA) and starch oleates were examined. Starch oleates (SO) with different degree of substitution (DS) were prepared by esterification of native starch and oleoyl chloride in heterogeneous conditions (pyridine). These prepared starch esters were used in the function of additives for preparation of blends with PLA. The PLA/starch oleates blends (9:1) have been prepared and evaluated by using attenuated total reflectance (ATR) spectroscopy technique. Subsequently, their mechanical properties, such as storage modulus (E'), loss modulus (E'') and tan D were studied as a function of temperature by dynamic mechanical thermal analysis (DMTA). These blends containing 10 wt. % SO show satisfactory mechanical properties in comparison to pure PLA

Využitie mikrovlnného žiarenia pri chemických modifikáciách polysacharidov

Príspevok je zameraný na prípravu nových biopolymérov z karboxymetylcelulózy (CMC) a hydroxyetylcelulózy (HEC) modifikáciou s kyselinou škoricovou v rôznych reakčných prostrediach účinkom mikrovlnného žiarenia. Ich charakterizáciu FT-IR a UV spektrami, ktoré potvrdili prítomnosť esterovej skupiny a štúdium vybraných povrchovo-aktívnych vlastností (povrchové napätie, kritická micelárna koncentrácia a emulgačná účinnosť). Použitím mikrovlnného ohrevu sa podarilo výrazne skrátiť reakčné časy prípravy nových derivátov CMC a HEC v porovnaní s konvenčným spôsobom ohrevu. Pripravené deriváty vykazovali výborné emulgačné účinnosti porovnateľné so štandardom Tweenom 20, avšak povrchové napätie znižovali len mierne

Crystal Structure, Infrared Spectra and DFT Study of Benzyl 2,3-Anhydro-β-D-Ribopyranoside

The crystal structure of benzyl 2,3-anhydro-β-D-ribopyranoside is orthorhombic, P2₁2₁2₁, Z = 4. The pyranose ring adopts the E_O conformation distorted considerably to the ⁵H_O direction. The molecules of the title compound are linked into infinite chains running along the a-axis by bifurcated O–H···O hydrogen bonds. Interaction energies of these hydrogen bonds are significantly different, ~−5.4 for the bond with the smaller and ~−1.1 kcal/mol for the bond with the larger O···O separation. The hydrogen-bond pattern is completed by the two weaker C–H···O intermolecular hydrogen bonds, aiming at the epoxy oxygen atom. IR vibrational spectrum was interpreted by means of comparison with the full list of vibrational modes predicted using DFT method in the solid state. While till 1495 cm⁻¹ the individual bands can be reconciled with single calculated modes, the region below this limit is populated by heavily overlapped HCH, HCO, HOC, COC and HCC bending modes merged with few ν(CC) and ν(CO) modes. The respective “red” shifts of the positions of the ν(OH) bands correlate well with the size of the O···O separation

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

Photo-induced Electron Emission of Nanostructured Carbon Thin Film Based Transmission Photocathodes at Different Electric Field

Very thin nanostructured carbon films were deposited on quartz substrate by reactive magnetron sputtering using graphite target and gas mixture of Ar and reactive gas N2 or N2+H2. Film thicknesses were in the range of 20–25 nm. Rutherford backscatter- ing spectrometry and Elastic recoil detection analytical method determined the concentration of elements in the films. Scanning electron microscopy scanned the sur- face morphology of carbon films. Raman spectroscopy was used for chemical structural properties determina- tion of very thin carbon films. Raman spectra intensi- ties were fitted with Gaussian peaks. The photo-induced (pulsed laser - 266 nm) electron emission properties of very thin nanostructured carbon films were investigated by the measurement of cathode bunch charge at differ- ent electric field and calculate quantum efficiency. The influence of different electric field on the photo-induced electron emission characteristics of prepared transmis- sion photocathodes are discussed

Polyglobalide-Based Porous Networks Containing Poly(ethylene glycol) Structures Prepared by Photoinitiated Thiol-Ene Coupling

The high interest in polymers from natural resources prompted us to investigate the use of enzymatically synthesized polyglobalide (PGL) in the preparation of polymer networks with potential applications as biomaterials for drug delivery devices. Polymer networks were obtained under mild conditions by photoinitiated thiol-ene coupling between PGL and a poly(ethylene glycol-co-thiomalate) (PEG-SH) copolymer obtained by polycondensation. The obtained polymer networks were thoroughly characterized by Raman spectroscopy, scanning electron microscopy, titration of thiol groups and elemental analysis. Our study took into consideration the synthesis parameters for the polymer networks, such as the total polymer concentration and the SH/C=C functionality molar ratio. Swelling in both THF and water was assessed, and the potential of the materials for drug delivery was determined. The scanning electron microscopy images showed that the prepared polymer networks may have different morphologies ranging from homogeneous polymer materials to macroporous structures. Additionally, the prepared materials were found to be suitable from a cytotoxicity point of view, enabling their application as biomaterials for drug delivery devices. © 2018 American Chemical Society.SASPRO Programme of the Slovak Academy of Sciences [1628/03/02]; People Programme (Marie Curie Actions) European Union's Seventh Framework Programme under REA Grant [609427]; National Scholarship Programme of the Slovak Republic [18428]; Ministry of Education, Youth and Sports of the Czech Republic through program NPU I [LO1504]; [APVV-15-0545]; [VEGA 2/0158/17]; [VEGA 2/0124/18