Thermal studies of silverpoly (methylmethacrylate) nanocomposites

The novel nanocomposite material based on surface-modified silver nanoparticles (Np) with average diameter of 6 nm and poly(methylmethacrylate) (PMMA) matrix was synthesized. The effect of silver loading on the thermal properties of PMMA was studied. The obtained transparent nanocomposites Ag/PMMA films were characterized by IR spectroscopy and thermal techniques (TGA, DSC). The chemical composition of the PMMA matrix is not changed in the presence of the metal nanoparticles, but the thermal stability of the nanocomposites was found to be better than thermal stability of the pure polymer. Also, Ag nanoparticles have pronounced effect on a glass transition temperature (Tg) of PMMA.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Synthesis and characterization of crosslinked polyurethanes

Two polyurethane samples, crosslinked with aliphatic hyperbranched polyester, were synthesized and examined in this work. The sample PUPDMS-EO was prepared using ethylene oxide-poly(dimethylsiloxane)-ethylene oxide as macrodiol, while the synthesis of PUPTMO was performed using poly(tetramethyleneoxide). The obtained results show that thermal stability of these networks can be improved by introducing the siloxane sequences. However, the sample PUPDMS-EO has at the same time much lower crosslinking density than PUPTMO.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Rheological and thermogravimetric analysis of unmodified and modified aliphatic hyperbranched polyester

The influence of the type of end groups on the rheological and thermal properties of aliphatic hyperbranched polyesters (AHBP) was investigated in this work. Unmodified, hydroxy-functional AHBP sample of third pseudo generation (AHBP- 3) and the same sample whose end –OH groups were modified with stearic acid (AHBP-3SA) were examined. The presence of the long alkyl chain ends, instead of the polar –OH groups, has reduced the possibility for H-bonding and value of the glass transition temperature. On the other side, by modification of the end –OH groups with stearic acid, thermal stability of AHBP has been improvedPhysical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Poly(urethane-ester-siloxane) networks

The waterproof performance and formation of hydrogen bonds in polyurethane (PU) networks based on Boltorn® hyperbranched polyester of the third pseudo generation (BH-30), α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)- ethylene oxide) (EO-PDMS-EO) and 4,4’-methylenediphenyl diisocyanate (MDI) were studied in this work. Obtained results revealed that as the content of EOPDMS-EO decreases, the degree of microphase separation increases, while the water resistance of the prepared PU networks decreases.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 2012

Interaction of gold nanoparticles with rat brain synaptosomal plasma membrane Na+/K+-ATPase and Mg2+-ATPase

The aim of the work was to investigate the interaction between borate capped gold nanoparticles (AuNPs) and the rat brain synaptosomal plasma membranes (SPM), as well as the effects of these AuNPs on SPM Na+ /K+ - ATPase and Mg2+-ATPase activity. Influence of AuNPs on Na+ /K+ -ATPase and Mg2+-ATPase activity was investigated as the function of AuNPs and protein concentration and preincubation time. AuNPs induced the stimulation of Na+ /K+ -ATPase activity for more than 100%, while Mg2+-ATPase activity reminded unaffected. We propose that this stimulation of enzyme activity was a consequence of an increase of the active surface of membranes.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Synthesis and swelling behavior of polyurethane networks based on hyperbranched polymer

A series of six polyurethane (PU) networks was synthesized from Boltorn (R) hydroxy-functional hyperbranched polyester (HBP) of the second pseudo generation as a cross-linking agent, alpha,omega-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO) and 4,4-methylenediphenyl diisocyanate, by two-step polymerization in solution. Each sample of the prepared PUs had different EO-PDMS-EO content. The chemical structure of the synthesized networks was analyzed by FTIR spectroscopy. The influence of the EO-PDMS-EO content and type of the solvent on the swelling behavior of the PUs in 2-propanol and toluene was investigated. During the swelling measurements, a certain amount of sal fractions was extracted from the PUs by solvents. According to the H-1-NMR results, sal fractions were mainly composed of the soluble hyperbranched PU, formed during the polymerization by partial modification of the end hydroxyl groups of HBP with NCO-terminated prepolymer synthesized in the first step of the reaction. Chains of the so reacted prepolymer can then fold back and form cyclic products by reaction of the free -NCO group from the NCO-terminated prepolymer with free -OH group of HBP. As the EO-PDMS-EO content increases the amount of the sol fractions and swelling degree also increased, indicating that networks with lower EO-PDMS-EO content are more cross-linked and have higher solvent resistance

Novel crosslinked polyurethanes based on hyperbranched polyester

The polyurethane (PU) elastomers based on hydroxy-terminated hyperbranched polyester (BH-20) and 4,4′-methylenediphenyl diisocyanate (MDI) as hard segments and hydroxyl-terminated ethylene oxide-poly(dimethylsiloxane)- ethylene oxide (PDMS-EO) as soft segment, were synthesized and examined in this work. The obtained results show that sol fraction decreases and thermal stability increases with increase of the hard segment content

Surface modification of graphitic carbon nitride with copper nanoparticles

Two different synthetic routes were employed to modify surface of graphitic carbon nitride (gCN) with copper nanoparticles (CuNPs). Structure, morphology and CuNPs distribution on presynthesized g-CN surface are characterized by FT-IR, XRD and TEM. Results suggested that the simpler method based on mixing of precursors in inert atmosphere and room temperature, resulted in better CuNPs distribution compared to method which used refluxing as a step in synthesis

Rheological and thermal properties of boltorn® hyperbranched polyesters

Rheological (in solution and in melt) and thermal properties of aliphatic hydroxyfunctional Boltorn® hyperbranched polyesters of different pseudo generation were investigated in this work. The obtained results show that 40 wt.% solutions of Boltorn® samples in N-methyl-2-pyrrolidinon exhibit Newtonian behaviour at 30 oC and that zero shear viscosity increases with increase of the generation number, i.e. molar mass. On the other side, vales of the Tg show only slight increase with increase of the molar mass. Thermal stability of investigated samples increases with increase of the number of generation