Search results for "surface modification"

Photoinduced functionalization of diterpenes: photochemical behaviour of grandifloric acid in methanol and acetonitrile

2004

Abstract Irradiation of grandiflorolic acid (11) at λ=254 nm in acetonitrile gave the two epimers 13 and 14 through a photodecarboxylation reaction of the carboxylic group on C-4. Irradiation of compound 11 in methanol at λ=254 nm provided the transformation of the C-20 angular methyl into a carbomethoxymethyl group. In this case, unlike compounds 13 and 14, only one of the two possible isomers (15) was obtained (equatorial methyl at C-4). A mechanistic approach of this reaction in discussed, and the role of mutual stereochemistry between C-20 methyl and C-19 carboxylic group in determining the course of the reaction is pointed out.

Different natures of surface electronic transitions of carbon nanoparticles

2017

The photoluminescence behaviour of carbon-based nanodots is still debated. Both core and surface structures are involved in the emission mechanism, and the electronic transitions can be modified by external agents such as metal ions or pH, but the general relation between the structure and the optical function is poorly understood. Here, we report a comparative study on the effects of these variables, changing the core structure from crystalline to amorphous, and modifying the surface structure by different passivation procedures. Our results highlight that the emission mechanism of the tunable visible fluorescence is identical for crystalline and amorphous samples, indicating the independe…

Plasma Functionalization of Multiwalled Carbon Nanotubes and Their Use in the Preparation of Nylon 6-Based Nanohybrids

2012

The possibility to obtain carbon nanotubes (CNT)/polyamide 6 composites with excellent mechanical properties in a simple, industrially scalable way is investigated. Commercial CNTs are treated by plasma while changing some key parameters (exposure time, plasma power, type of gas) in order to optimize the process and to achieve a sufficient degree of functionalization. The treated samples are characterized by Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The most interesting samples are selected to be used as reinforcing fillers, in different concentrations, in a polyamide 6 matrix. The mechanical tests show a dramatic increase of both tens…

SURFACE MODIFICATION OF EAA WITH FUNCTIONALIZED SILICA NANOPARTICLES

2009

Modification of carboxyl groups of poly(ethylene-co-acrylic acid) via facile wet chemistry method: A kinetic study

2010

Abstract In this work, we present the results of a kinetic study of the surface modification of the carboxyl group of poly(ethylene-co-acrylic acid) into acyl chloride. Reaction temperature and time, concentration of the reactants, kind of agitation have been changed in order to understand their effect on the conversion. A study on the penetration of the reaction inside the sample bulk was also performed. The results indicate that, when short reaction times are adopted, the reaction limits to the outer layers of the samples and, in this case, on increasing the temperature, the concentration of the reactants and the stirring allows having a faster kinetic. At longer reaction times, the react…

"A versatile post-polymerization modification method for polyglutamic acid: synthesis of orthogonal reactive polyglutamates and their use in ""click …

2013

In this article we describe a versatile methodology for the synthesis of polyglutamic acid (PGA) derivatives bearing orthogonal reactive sites. The reactive groups enable selective conjugation chemistry by copper catalyzed azide-alkyne coupling (CuAAC). PGA was derived in aqueous media as well as in organic media using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl morpholinium chloride (DMTTM) salts. The spectra of attached chemical moieties ranges from simple PEGylation with 2,5,8,11,14,17,20-heptaoxadocosan-22-amine (mEG(6)NH2) to the incorporation of propargylamine, 11-azido-3,6,9-trioxaundecan-1-amine (NH2-EG(2)N-3), and 20-azido-3,6,9,12,15,18-hexaoxaicosan-1-amine (NH2-EG(6)N-3). Here…

When Functionalization of PLA Surfaces Meets Thiol−Yne Photochemistry: Case Study with Antibacterial PolyaspartamideDerivatives

2014

International audience; In this work we wish to report on the covalent functionalization of polylactide (PLA) surfaces by photoradical thiol–yne to yield antibacterial surfaces. At first, hydrophilic and hydrophobic thiol fluorescent probes are synthesized and used to study and optimize the conditions of ligation on alkyne-PLA surfaces. In a second part, a new antibacterial polyaspartamide copolymer is covalently grafted. The covalent surface modification and the density of surface functionalization are evaluated by SEC and XPS analyses. No degradation of PLA chains is observed, whereas covalent grafting is confirmed by the presence of S2p and N1s signals. Antiadherence and antibiofilm acti…

Click modification of multifunctional liposomes bearing hyperbranched polyether chains.

2014

Aiming at controlled modification of liposomal surface structures, we describe a postpreparational approach for surface derivatization of a new type of multifunctional, sterically stabilized liposomes. Application of dual centrifugation (DC) resulted in high encapsulation efficiencies above 50% at very small batch sizes with a total volume of 150 μL, which were conductive to fast and efficient optimization of variegated surface modification reactions. Cholesterol-polymer amphiphiles, including complex hyperbranched polyether structures bearing 1-4 terminal alkynes, were used in DC formulations to provide steric stabilization. The alkyne moieties were explored as anchors for the conjugation …

Functionalization of Liposomes with Hydrophilic Polymers Results in Macrophage Uptake Independent of the Protein Corona

2019

Liposomes are established drug carriers that are employed to transport and deliver hydrophilic drugs in the body. To minimize unspecific cellular uptake, nanocarriers are commonly modified with poly(ethylene glycol) (PEG), which is known to minimize unspecific protein adsorption. However, to date, it has not been studied whether this is an intrinsic and specific property of PEG or if it can be transferred to hyperbranched polyglycerol (hbPG) as well. Additionally, it remains unclear if the reduction of unspecific cell uptake is independent of the “basic” carrier at which a surface functionalization with polymers is usually applied. Therefore, we studied the protein corona of differently fun…

Study of the High-Frequency Inductive Coupled Discharge Plasma Interaction with Walls

2007

The high-frequency electrodeless light sources (HFELS) are widely used as bright radiators of narrow and intense spectral lines covering the region from VUV to IR. Special HFELS filled with pure helium at pressures from 0.2 to 5 Torr were prepared for diagnostics of interaction between the filling element and the wall material (glass). Pollution of the discharge plasma with the oxygen admixture was studied by spectroscopy. Atomic force microscopy experiments were performed to find modification of the wall surface at the nanoscale level. Release of oxygen by the walls is found to depend strongly on the discharge conditions and significant changes of the surface structure are detected after p…