Kinetics and Mechanism of Liquid-State Polymerization of 2,4-Hexadiyne-1,6-diyl -(-toluenesulfonate) as Studied by Thermal Analysis.

A detailed investigation of the liquid-state polymerization of diacetylenes by calorimetric (DSC) and spectroscopic (in situ EPR) thermal analysis techniques is performed. Isoconversional kinetic analysis of the calorimetric data reveals that liquid-state polymerization is governed by a well-defined rate-limiting step as evidenced by a nearly constant isoconversional activation energy. By comparison, solid-state polymerization demonstrates isoconversional activation energy that varies widely, signifying multistep kinetics behavior.

Kinetics of Polycycloaddition of Flexible α-Azide-ω-Alkynes Having Different Spacer Length.

Two flexible α-azide-ω-alkynes differing in the length of the hydrocarbon spacers (C vs. C) between functional groups are synthesized. Their bulk polymerization kinetics is studied by differential scanning calorimetry (DSC) and parameterized with the aid of isoconversional methodology.

Probing kinetic and mechanistic features of bulk azide-alkyne cycloaddition.

Bulk azide-alkyne cycloaddition between 1-azidodecane and phenyl propargyl ether is studied in detail under the conditions of linear heating. The reaction mechanism involves two parallel channels that respectively yield isomeric 1,4- and 1,5-adducts. Remarkably, the ratio of the isomer amounts remains practically the same at different heating rates.

The Kinetics of Formation of Microporous Polytriazine in Diphenyl Sulfone.

This study highlights the value of nonisothermal kinetic methods in selecting temperature conditions for the isothermal preparation of microporous polymeric materials. A dicyanate ester is synthesized and the kinetics of its polymerization in diphenyl sulfone are studied by calorimetry under nonisothermal conditions. The kinetics are analyzed by a model-based approach, using the Kamal model, as well as by a model-free approach, using an advanced isoconversional method.

Problems with Applying the Ozawa-Avrami Crystallization Model to Non-Isothermal Crosslinking Polymerization.

Ozawa has modified the Avrami model to treat non-isothermal crystallization kinetics. The resulting Ozawa-Avrami model yields the Avrami index () and heating/cooling function (()). There has been a number of recent applications of the Ozawa-Avrami model to non-isothermal crosslinking polymerization (curing) kinetics that have determined and have used () in place of the rate constant (()) in the Arrhenius equation to evaluate the activation energy () and the preexponential factor ().

Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester.

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics.

Polymerization Kinetics of Cyanate Ester Confined to Hydrophilic Nanopores of Silica Colloidal Crystals with Different Surface-Grafted Groups.

This study investigates the kinetics of confined polymerization of bisphenol E cyanate ester in the nanopores of the three types of silica colloidal crystals that differ in the concentration and acidity of the surface-grafted proton-donor groups. In all three types of pores, the polymerization has released less heat and demonstrated a very similar significant acceleration as compared to the bulk process. Isoconversional kinetic analysis of the differential scanning calorimetry measurements has revealed that the confinement causes not only a dramatic change in the Arrhenius parameters, but also in the reaction model of the polymerization process.

Pore-Size Distribution of Silica Colloidal Crystals from Nitrogen Adsorption Isotherms.

Silica colloidal crystals are face-centered cubic structures comprised of silica spheres with the diameters ranging between tens and hundreds of nanometers. The voids between the spheres form pores, which can be probed by nitrogen adsorption porosimetry. Here, we prepared two mesoporous samples and a macroporous reference sample and then measured nitrogen adsorption and desorption isotherms for further characterization.

Porous Structure of Silica Colloidal Crystals.

We prepared silica colloidal crystals with different pore sizes using isothermal heating evaporation-induced self-assembly in quantities suitable for nitrogen porosimetry and studied their porous structure. We observed pores of two types in agreement with the description of silica colloidal crystals as face-centered cubic packed structures containing octahedral and tetrahedral voids. We calculated the sizes of these pores using the Derjaguin-Broekhoff-de Boer theory of capillary condensation for spherical pores.

Synthesis of Cyanate Esters Based on Mono-O-Methylated Bisphenols with Sulfur-Containing Bridges.

We described a synthetic approach to bisphenol-based monocyanate esters based on mono--methylation of parental bisphenols followed by cyanation of the residual phenolic hydroxyl. Structures of the synthesized compounds were determined by the application of IR, NMR ¹H and C spectroscopies, EI and MALDI mass spectrometry, and purity of the final product was controlled by HPLC. We showed that stability of the cyanate esters depends on the nature of the bridging group.

Heavy oil oxidation in the nano-porous medium of synthetic opal.

Increasing interest to study hydrocarbon behavior in fine porous media, awakened by the shale revolution, requires the application of suitable model porous media. In the current study we prepared nano-porous synthetic opal, profoundly investigated its morphological and textural properties, and studied the kinetics of combustion of heavy oil impregnated into nanopores. Comparison of kinetic parameters of the oil oxidation process for nano-porous and coarse-porous media revealed that nanoconfinement affects the reactivity of oil.