Amphiphilic block copolymers by a combination of anionic polymerization and selective post-polymerization functionalization

AbstractAnionic polymerization is the oldest known living/controlled polymerization methodology that leads to well defined macromolecules. It has been also used, with considerable success, for the synthesis of amphiphilic block copolymers (AmBC), a class of functional copolymers having interesting self-assembling properties and high potential for applications in various technological fields. The use of mild and effective post-polymerization functionalization/chemical modification reactions on block copolymers has substantially increased the synthetic capabilities of anionic polymerization methodologies, toward the creation of a variety of AmBC. In this feature article we review work done on these directions in the last ten years. Some perspectives and future work on this particular field of polymer science are also discussed

Холотропное дыхание как метод реализации потенциала личности сотрудника

На сегодняшний день в организациях существует множество проблем, из-за которых возникают сложности как в управлении предприятием, так и в эффективной работе сотрудников. Для любого управляющего компанией важно, чтобы сотрудник был уверенным, умеющим нестандартно мыслить, инициативным, целеустремленным, но в большинстве случаев на предприятии такие сотрудники отсутствуют или их количество ограниченно. В любом сотруднике кроется творческая личность, которая не всегда может быть реализована на практике или же просто подавлена. Для того чтобы предприятие могло эффективно функционировать, важно, чтобы каждый сотрудник мог разобраться в своих проблемах и обрести внутреннюю гармонию, которая позволит ему настроиться на работу и выполнять ее эффективно. Методика холотропного дыхания может помочь личности реализовать свой скрытый потенциал. Цель работы: определить значимость методики холотропного дыхания в организации и выявить, какое влияние она оказывает как на сотрудников, так и на предприятие в целом. Методы исследования: анализ литера- туры по данной проблематике, аналитический метод. Результаты: выводы, полученные в данном исследовании, способствуют определению действенности методики холотропного дыхания и значимости ее применения в организации. Today there are many problems in organizations which lead to difficulties in the management of an enterpriseand in the effective work of the staff. For any company manager it is important that the employee wasconfident, able to think outside the box, initiative, committed, but in most cases such employees are absent ortheir number is limited. There is creative personality in any employee which can’t always be revealed or issimply suppressed. In order for a company to operate effectively, it is important that every employee couldunderstand their problems and find inner harmony, which will allow them to tune into work and perform itefficiently. The technique of holotropic breathwork can help the person to realize their hidden potential. Objective:to determine the significance of the technique of holotropic breathwork in the organization and itsimpact on the employees and the enterprise as a whole. Methods: review of the literature on this subject,data analysis. Results. The findings of this study help to identify the effective methods of holotropic breathworkand the importance of its application in the organization

Micellar and fractal aggregates formed by two triblock terpolymers with different arrangements of one charged, one neutral hydrophilic and one hydrophobic block

We have studied the self-assembled structures of two triblock amphiphilic polyelectrolytes of different topologies, containing a charged poly[sodium(sulfamate/carboxylate)isoprene] (SCPI) block, a polystyrene (PS) hydrophobic block and a hydrophilic neutral poly(ethylene oxide) (PEO) block in aqueous solutions, using Small Angle Neutron Scattering (SANS) and Light Scattering (LS). SANS reveals micellar and fractal aggregates in coexistence for both systems. In the case of SCPI-b-PS-b-PEO there is a higher content in fractal aggregates in comparison with PS-b-SCPI-b-PEO. In both cases the micellar aggregates are stable under different solution conditions, whereas the fractal aggregates appear to break upon addition of salt in the PS-b-SCPI-b-PEO system. The detailed picture of the micellar aggregates is consistent with the anticipated morphology of charged and neutral spherical macromolecular brushes, extended to mixed and sequential brushes. The analytical description obtained by SANS is used to interpret the LS data which is very sensitive to the presence of two species and therefore provides information on average values of the measured parameters

Quaternized Poly[3,5-bis(dimethylaminomethylene)hydroxystyrene]/DNA Complexes: Structure Formation as a Function of Solution Ionic Strength

The formation of complexes between the cationic polyelectrolyte poly­[3,5-bis­(dimethylaminomethylene)­hydroxystyrene] (Q-N-PHOS), bearing two cationic sites per repeating unit, and DNA molecules in aqueous solutions is investigated at pH 7 and at various salt (NaCl) concentrations and DNA/polymer ratios. The structural characteristics of the polyplexes at different DNA/polymer ratios were characterized in terms of mass, size, and charge using static, dynamic, and electrophoretic light scattering and fluorescence spectroscopy. The results indicate that the complexes have a loose spherical morphology with size in the range of 45–100 nm depending on polymer to DNA ratio and ionic strength of the solution. Most interestingly, it is found that the polyplexes’ response to changes in the ionic strength of the surrounding solution after complexation depends strongly on the initial solution ionic strength during complex formation. This also points to differences in the nanostructures of polyplexes formed at different ionic strengths

Effect of Temperature on the Direct Synthesis of Gold Nanoparticles Mediated by Poly(dimethylaminoethyl methacrylate) Homopolymer

The one-pot synthesis of gold nanoparticles (AuNPs) mediated by poly­(dimethylaminoethyl methacrylate) homopolymer, without the use of a reducing agent, has been studied under different temperatures. The obtained results show that the higher is the temperature, during nanoparticle synthesis, the faster is nanoparticle creation and the more uniform are the produced nanoparticles. The kinetic studies on the nanoparticles synthesis were performed mainly by light scattering techniques. The obtained results indicate that at elevated temperatures the synthesis takes place in three steps, while at lower temperatures the followed synthetic pathways are more complex. Finally, the development of gold nanoparticles was also followed by UV–vis absorption measurements, indicating a good agreement between the two techniques

Poly(vinyl benzyl trimethylammonium chloride) Homo and Block Copolymers Complexation with DNA

In this work we focus on the use of novel homo and block copolymers based on poly­(vinyl benzyl trimethyl­ammonium chloride) as gene delivery vectors. The homopolymers and block copolymers were synthesized by RAFT polymerization schemes and molecularly characterized. DNA/polymer complexes (polyplexes) in a wide range of N/P (amino-to-phosphate groups) ratios were prepared. The ability of the novel polymers to form complexes with linear DNA was investigated by light scattering, zeta potential, and ethidium bromide fluorescence quenching measurements. The resulting polyplexes were in the size range of 80–300 nm and their surface potential changed from negative to positive depending on the N/P ratio. The stability of polyplexes was monitored by changes in their hydrodynamic parameters in the presence of salt. The novel vector systems were visualized by transmission electron microscopy. The influence of factors such as molar mass, content, and chemical structure of the polycationic moieties as well as presence of a hydrophilic poly­[oligo­(ethylene glycol) methacrylate] block on the structure and stability of the polyplexes, kinetics of their formation, and effectiveness of the (co)­polymers to shrink and pack DNA was discussed

Small nanosized poly(vinyl benzyl trimethylammonium chloride) based polyplexes for siRNA delivery

The success of siRNA gene therapy requires the availability of safe and efficient delivery systems. In the present study, we investigated poly(vinyl benzyl trimethylammonium chloride) (PVTC) and its block copolymer with poly(oligo(ethyleneglycol) methacrylate) (POEGMA) as delivery vector for siRNA. Small polyplexes ranging from 8 to 25 nm in diameter were formed in aqueous solution by spontaneous self-assembly of both the homopolymer and block copolymer with siRNA and the formed particles were stable at physiological ionic strength. It was shown that when human ovarian adenocarcinoma cells were transfected, siRNA polyplexes based on PVTC (40 kDa) and PVTC-POEGMA-4 (PP4, 34 kDa) efficiently induced luciferase gene silencing to the same extent as the formulation based on a commercial lipid (Lipofectamine®) (∼80%), and showed higher gene silencing than the linear polyethylenimine formulation linear polyethylenimine (∼35%). Importantly, the POEGMA block polymers displayed a significantly lower cytotoxicity as compared to L-pEI. siRNA polyplexes based on the block polymers displayed high cellular uptake resulting in ∼50% silencing of luciferase expression also in the presence of serum. These results demonstrate that PVTC-based polymers are promising siRNA delivery vectors

Small nanosized poly(vinyl benzyl trimethylammonium chloride) based polyplexes for siRNA delivery

The success of siRNA gene therapy requires the availability of safe and efficient delivery systems. In the present study, we investigated poly(vinyl benzyl trimethylammonium chloride) (PVTC) and its block copolymer with poly(oligo(ethyleneglycol) methacrylate) (POEGMA) as delivery vector for siRNA. Small polyplexes ranging from 8 to 25 nm in diameter were formed in aqueous solution by spontaneous self-assembly of both the homopolymer and block copolymer with siRNA and the formed particles were stable at physiological ionic strength. It was shown that when human ovarian adenocarcinoma cells were transfected, siRNA polyplexes based on PVTC (40 kDa) and PVTC-POEGMA-4 (PP4, 34 kDa) efficiently induced luciferase gene silencing to the same extent as the formulation based on a commercial lipid (Lipofectamine®) (∼80%), and showed higher gene silencing than the linear polyethylenimine formulation linear polyethylenimine (∼35%). Importantly, the POEGMA block polymers displayed a significantly lower cytotoxicity as compared to L-pEI. siRNA polyplexes based on the block polymers displayed high cellular uptake resulting in ∼50% silencing of luciferase expression also in the presence of serum. These results demonstrate that PVTC-based polymers are promising siRNA delivery vectors

Synthesis and multiscale evaluation of LiNbO3 - Containing silicate glass-ceramics with efficient isotropic SHG response

International audienceA study of bulk second harmonic generation (SHG) response of lithium niobium silicate glass-ceramics is presented. The observed macroscopic SHG signals have an isotropic 3D nature. To interpret this particular nonlinear optical response, a multiscale approach is used in which clear correlations between structure and optical response are characterized from the sub-micrometer to the millimeter scale. In particular, it is inferred that the radial distribution of the LiNbO3 crystallites in spherulite domains is at the origin of the isotropic bulk second order optical property. It is suggested that spherulitic crystallization in glass-ceramic is a challenging method to elaborate isotropic nonlinear optical properties in inorganic materials