Wyniki wyszukiwania - BazTech

1

Short discussion of static properties of dense polymer melts in two dimensions : CMA Monte Carlo Simulation vs Molecular Dynamics

Polanowski P., Jeszka J. K.

Computational Methods in Science and Technology

|

2020

|

Vol. 26, No. 4

137-142

EN

In this paper we present the results of an extensive Monte Carlo lattice simulation of two dimensional dense athermal polymer solutions using the Cooperative Motion Algorithm (CMA). Simulations were performed for a wide range of polymer chain length N which varies from 32 to 1024 and for high concentration of polymer. Our results were compared with those obtained by means of molecular dynamics [1].

2

Monte-Carlo Simulations of Two-Dimensional Polymer Solutions with Explicit Solvent Treatment

Polanowski P., Jeszka J. K., Sikorski A.

Computational Methods in Science and Technology

|

2017

|

Vol. 23, No. 4

305--316

EN

The static properties of two dimensional athermal polymer solutions with explicit solvent molecules were studied by Monte Carlo lattice simulations using the cooperative motion algorithm (CMA). The simulations were performed for a wide range of polymer chain length N (from 16 to 1024) and polymer concentration (from 0.0156 to 1.00). The results obtained for short chains (N < 256) were in good agreement with theoretical predictions and previous simulations. For the longest chains (512 or 1024 beads) some unexpected behavior in the dilute and semidilute regimes was found. A rapid change in the concentration dependence of the end-to-end distance, the radius of gyration and the chain asphericity was observed below a critical concentration of the microphase separation, ϕc = 0.6 (for N = 1024). At concentrations lower than _c, the chains tends to be more rod-like. Single chain scattering structure factors showed changes in the fractal dimension of the chain as a function of the polymer concentration. The observed phenomena can be related to the excluded volume of solvent molecules, which leads to a modification of chain statistics in the vicinity of other chains.

3

Functional Nanocomposite Poly(phenylene sulphide) Fibres - Preliminary Studies

Kulpinski P., Czarnecki P., Niekraszewicz B., Jeszka J. K.

Fibres & Textiles in Eastern Europe

|

2016

|

Vol. 24, no. 4 (118)

20--26

EN

Composite poly(phenylene sulphide) (PPS) fibres and nonwovens were obtained by the melt blowing method. A specially designed twin screw extruder was used which allowed to perform several mixing cycles prior to final extrusion. Multiwall carbon nanotubes (CNTs) and carbonyl iron microparticles were used as the additives. To obtain possibly good dispersion of the modifiers in the polymer melt, the CNTs were first dispersed in N-methyl-2-pyrrolidone and Fe microparticles were dispersed in polyethylene wax. Rheological characteristics of the melts and bulk composites, such as viscosity, loss and storage moduli, are similar to those reported by other groups; however, the contents of additives must be lower than in the case of bulk materials to assure satisfactory melt spinability. The fibres obtained show satisfactory mechanical characteristics and electromagnetic screening efficiency in the GHz region.

PL

W artykule zaprezentowano kompozytowe włókna oraz włókniny z poli(siarczku fenylenu) wytwarzane metodą melt-blown. Do formowania włókien zastosowano laboratoryjną wytłaczarkę dwuślimakową, której konstrukcja pozwala na wykonanie kilku cykli mieszania polimeru przed procesem formowania włókien. Jako modyfikatory zastosowano wielościenne nanorurki węglowe (CNTs) oraz cząstki żelaza o rozdrobnieniu mikrometrycznym. W celu otrzymania możliwe dobrej dyspersji modyfikatorów w polimerze, nanorurki węglowe zostały wstępnie rozprowadzone w N-metylo pirolidonie (NMP), natomiast mikrocząstki żelaza były zdyspergowane w niskocząsteczkowym wosku polietylenowym. Wykonano charakterystykę reologiczną stopów polimerowych zawierających modyfikatory. Określono również parametry mechaniczne włókien oraz oszacowano właściwości barierowe otrzymanych włóknin. Na podstawie uzyskanych wyników można stwierdzić, iż otrzymane włókna charakteryzują się stosunkowo dobrymi parametrami mechanicznymi oraz mają właściwości ekranujące w zakresie fal elektromagnetycznych o częstotliwości rzędu GHz.

4

Nanokompozyty polilaktyd/wielościenne nanorurki węglowe - otrzymywanie i właściwości elektryczne

Pietrzak Ł., Jeszka J. K.

Polimery

|

2010

|

T. 55, nr 7-8

524-528

PL

Opracowaną metodą wytworzono nanokompozyty połilaktydu (PLA) z udziałem wielościennych nanorurek węglowych (MWCNTs) uzyskując dobrą dyspersję nanorurek w matrycy. Na pierwszym etapie zdyspergowano nanorurki w roztworze polimeru za pomocą ultradźwięków, a następnie w wyniku szybkiego wytrącania polimeru z roztworu uniemożliwiono powtórną agregację MWCNTs. Zbadano zależność przewodnictwa elektrycznego, wytworzonych tą metodą kompozytów połilaktydu z różną zawartością nanorurek, od udziału fazy przewodzącej. Dla porównania w taki sam sposób otrzymano kompozyty PLA z sadzą jako napełniaczem przewodzącym. Nanokompozyty PLA/MWCNTs wykazywały bardzo niski próg perkolacji (0,25 % mas.) i przewodnictwo (przy zawartości l % mas. monomeru) równe 5 · 10-² S/cm. Uzyskany próg perkolacji jest 10 razy niższy, a przewodnictwo 100 razy większe niż w przypadku kompozytów zawierających sadzę. Obserwowane różnice są spowodowane wysokim współczynnikiem kształtu nanorurek i ich wysokim przewodnictwem.

EN

A procedure for the synthesis of polymeric nanocomposites comprising of polylactide (PLA) and well-dispersed multiwalled carbon nanotubes (MWCNT) (Figs. 3, 4) has been presented. The method involves the dispersion of the nanotubes in the PLA solution with the aid of ultrasounds and a rapid precipitation of the polymer composite in order to avoid reaggregation of the CNTs. The dependence of electrical conductivity on the content of the conducting phase for the polylactide composites containing various amounts of nanotubes obtained in this method was determined (Fig. 5). For comparison, composites with carbon black (Monarch 1100) were also prepared using the same procedure. The obtained PLA/MWCNT composites were characterized by low percolation threshold (0.25 wt. %) and a conductivity value of 5 · 10-² S/cm (with 1 wt. % of nanotubes). The obtained percolation threshold is ten times lower, and conductivity 100 times higher than in the case of respective composites containing carbon black. These differences were attributed to the high aspect ratio of the MWCNTs and their high conductivity.

5

Nanogel formation by intrachain radiation-induced cross-linking. Simulation and experiment

Ulański P., Kadłubowski S., Jeszka J.K.

Materials Science Poland

|

2006

|

Vol. 24, No. 2/2

467--476

EN

Nanogel formation by intrachain radiation-induced cross-linking is described. The origin of dispersive kinetics observed in pulse radiolysis experiments and the influence of cross-linking method on nanogel structure are studied by the Monte-Carlo simulation. The simulations have been performed on an fcc lattice using the cooperative motion algorithm. The recombination kinetics is studied as a function of the chain length (20-1068 beads) and of the number of radicals generated per chain. It is shown that the radical recombination rate coefficients are time-dependent (dispersive kinetics) and the simulation results can be fitted using single "stretched exponential" (KWW) function for two radicals per chain and a sum of two KWW functions for a larger number of radicals. The nanogel structure (radius of gyration and loop lengths, related to the resistance of nanogels to scissions) has also been studied. It is found that in the case of instant radical generation, the increasing number of radicals leads to formation of smaller and smaller loops. Results of the simulations are compared with the pulse radiolysis experiment on poly(ethylene oxide) using a suitable scaling of MC time and unit length, and a good agreement is obtained.

6

Conducting polymer films with new organic donor MDT-TSF: preparation and properties

Tracz A., Mierczyńska A., Takimiya K., Otsubo T., Niihara N., Jeszka J.K.

Materials Science Poland

|

2006

|

Vol. 24, No. 2/2

517--526

EN

Preparation and properties of surface-conductive polymer composites based on a recently synthesized electron-donor, methylenedithio-tetraselenefulvalene (MDT-TSF) are described. Polycarbonate and biodegradable polyester polylactide are used as polymer matrices. The obtained surface-conductive materials with MDT-TSF polyiodides show high, metal-like conductivities, indicating that MDT-TSF is one of the best donors for conductive composites.

7

Zone casting - a universal method of preparing oriented anisotropic layers of organic materials

Tracz A., Pakula T., Jeszka J. K.

Materials Science Poland

|

2004

|

Vol. 22, No. 4

415--421

EN

A method for the preparation of oriented, anisotropic layers of soluble molecular materials on substrates that were not pre-oriented (so-called zone casting) is presented. The method consists in casting a suitable solution, continuously supplied by a nozzle, onto a moving substrate. Solvent evaporation takes place from the surface of the meniscus formed between a special flat nozzle and the substrate. Due to a gradient of the solute concentration, its solidification proceeds in a narrow zone under highly anisotropic conditions. The conditions of stationary deposition and the influence of various parameters on the process, such as casting speed, the diffusion coefficient, evaporation rate, are discussed. It is shown that the zone casting can be used to obtain anisotropic layers of many different low-molecular-weight and macromolecular materials.

8

Synthesis of gold nanoparticles in solid state by thermal decomposition of an organometallic precursor

Wostek-Wojciechowska D., Jeszka J. K., Uznanski P. U., Amiens C., Chaudret B., Lecante P.

Materials Science Poland

|

2004

|

Vol. 22, No. 4

407--413

EN

Gold nanoparticles were obtained directly in solid polymer films by thermal decomposition of the [O(Au(PPh3))3][BF4] precursor molecularly dispersed in the polymer and by decomposition of microcrystals on different supports. The nanoparticles were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis spectroscopy, and wide-angle X-ray scattering (WAXS). In spite of high precursor concentration, the size of the obtained nanoparticles was similar to those prepared in diluted solutions.