scholarly journals Dependence on Film Thickness of Guest-Induced c Perpendicular Orientation in PPO Films

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4384
Author(s):  
Baku Nagendra ◽  
Emanuele Vignola ◽  
Christophe Daniel ◽  
Paola Rizzo ◽  
Gaetano Guerra
Keyword(s):  
Crystallinity Index ◽  
Crystalline Polymer ◽  
Sorption Kinetics ◽  
Film Plane ◽  
Melting Enthalpy ◽  
Amorphous Films ◽  
Guest Molecules ◽  
Confined Spaces ◽  
Inflection Points ◽  
Kinetics Of

For poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) films exhibiting nanoporous-crystalline (NC) phases, c^ orientation (i.e., crystalline polymer chain axes being preferentially perpendicular to the film plane) is obtained by crystallization of amorphous films, as induced by sorption of suitable low-molecular-mass guest molecules. The occurrence of c^ orientation is relevant for applications of NC PPO films because it markedly increases film transparency as well as guest diffusivity. Surprisingly, we show that the known crystallization procedures lead to c^ oriented thick (50–300 μm) films and to unoriented thin (£20 μm) films. This absence of crystalline phase orientation for thin films is rationalized by fast guest sorption kinetics, which avoid co-crystallization in confined spaces and hence inhibit formation of flat-on lamellae. For thick films exhibiting c^ orientation, sigmoid kinetics of guest sorption and of thickening of PPO films are observed, with inflection points associated with guest-induced film plasticization. Corresponding crystallization kinetics are linear with time and show that co-crystal growth is poorly affected by film plasticization. An additional relevant result of this study is the linear relationship between WAXD crystallinity index and DSC melting enthalpy, which allows evaluation of melting enthalpy of the NC α form of PPO (DHmo = 42 ± 2 J/g).

Modeling of sorption kinetics of U(VI) micro-quantities nanostructured materials with anatase mesoporous structures

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Veniamin Zheleznov ◽  
Aleksey Golikov ◽  
Tatiana Sokolnitskaya ◽  
Sergey Ivannikov
Keyword(s):  
Nanostructured Materials ◽  
Sorption Kinetics ◽  
Uranyl Ion ◽  
Competitive Sorption ◽  
Hydroxyl Groups ◽  
Complex Ions ◽  
The Stability ◽  
Kinetics Of ◽  
Mesoporous Structures ◽  
Ionic Forms

Abstract The sorption kinetics of uranyl ions micro-quantities from fluoride solutions by nanostructured materials with anatase mesoporous structures has been studied. Using the model of competitive sorption of ions and positively charged complexes of uranyl ion on deprotonated hydroxyl groups of an anatase, kinetic curves of changes in the ratio of ionic forms of uranium in solution were calculated. Modeling was carried out under the assumption of a two-stage mechanism of uranium complex ions sorption. The modeling considered the influence of the uranyl ion carbonate complexes formation. The shift in equilibrium among ionic forms of uranyl correlates with the stability of the complexes in solution.

scholarly journals c-Perpendicular Orientation of Poly(ʟ-lactide) Films

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1572
Author(s):  
Baku Nagendra ◽  
Paola Rizzo ◽  
Christophe Daniel ◽  
Lucia Baldino ◽  
Gaetano Guerra
Keyword(s):  
Low Temperature ◽  
Film Plane ◽  
Wide Angle ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Amorphous Films ◽  
High Transparency ◽  
X Ray ◽  
Crystalline Forms ◽  
Induced Crystallization

Poly(ʟ-lactide) (PLLA) films, even of high thickness, exhibiting co-crystalline and crystalline α phases with their chain axes preferentially perpendicular to the film plane (c⊥ orientation) have been obtained. This c⊥ orientation, unprecedented for PLLA films, can be achieved by the crystallization of amorphous films as induced by low-temperature sorption of molecules being suitable as guests of PLLA co-crystalline forms, such as N,N-dimethylformamide, cyclopentanone or 1,3-dioxolane. This kind of orientation is shown and quantified by two-dimensional wide-angle X-ray diffraction (2D-WAXD) patterns, as taken with the X-ray beam parallel to the film plane (EDGE patterns), which present all the hk0 arcs centered on the meridian. PLLA α-form films, as obtained by low-temperature guest-induced crystallization, also exhibit high transparency, being not far from those of the starting amorphous films.

Experimental Investigations of the Kinetics of a Catalytic Trapping Reaction in Confined Spaces

1996 ◽  
Vol 464 ◽  
Author(s):  
Mark S. Feldman ◽  
Anna L. Lin ◽  
Raoul Kopelman
Keyword(s):  
Reaction Front ◽  
Rate Coefficient ◽  
Capillary Tube ◽  
One Dimension ◽  
Experimental Investigations ◽  
Confined Spaces ◽  
Diffusion Limited ◽  
Kinetics Of ◽  
Oxidation Of Glucose ◽  
Theoretical Results

AbstractWe investigate the anomalous kinetics in one dimension of a diffusion limited catalytic trapping reaction, A + T → T, by measuring the oxidation of glucose. The reaction is carried out in a thin capillary tube, and the depletion of oxygen in the vicinity of the reaction front is monitored by the fluorescence of a Ru(II) dye. Theoretical results and simulations have predicted an asymptotic t1/2 dependence for the rate coefficient. We observe a depedence on t0.56, with what appears to be an asymptotic behavior approaching t1/2.

Sorption Kinetics of High Pressure Gases in Polymeric Tubing Materials

2006 ◽  
Author(s):  
P. Jaeger ◽  
S. Buchner ◽  
R. Eggers
Keyword(s):  
Diffusion Coefficients ◽  
Gas Permeability ◽  
Gravimetric Method ◽  
Sorption Kinetics ◽  
Operating Pressure ◽  
Gas Solubility ◽  
Atmospheric Conditions ◽  
High Solubility ◽  
Industrial Practice ◽  
Kinetics Of

A gravimetric method was applied to determine the sorption kinetics of gases into polymers. Diffusivity as well as sorption capacity are determined directly. Data of gas permeability that are required for calculating leakage rates in polymeric flexile gas and oil ducts may be retrieved by multiplying the obtained diffusion coefficients and the gas solubility. In general carbon dioxide enters polymers to the highest extent. In industrial practice, the high solubility of CO2 e.g. may lead to explosive decompression of sealings once the operating pressure is reduced to atmospheric conditions. Diffusion coefficients are presented in the range of 75 to 130°C at 2 to 30 MPa.

Sign in / Sign up

Export Citation Format

Share Document