Theoretical Study of the Conversion of Sulfonyl Precursors into Chains of Poly(p-phenylene vinylene)

Abstract

The elimination and side reactions involved in the thermal conversion of sulfonyl precursor chains into poly(p-phenylene vinylene) (PPV) have been studied in detail, using Density Functional theory, along with the MPW1K functional. The performance of the MPW1K functional for describing radical dissociation and internal conversion reactions of sulfonyl precursors has been assessed against the results of benchmark CCSD(T) calculations. Enthalpies as well as entropies are calculated at different temperatures at the level of the rigid rotor-harmonic oscillator approximation. Entropy effects on internal elimination reactions are very limited. In sharp contrast, at the temperatures under which the conversion is usually performed (550 K), entropy contributions to the activation energies are found to be very significant and to strongly favor direct radical dissociations of the precursors. Further radical side reactions following an E(i) conversion through an alkyl substituent may also significantly contribute to the formation of sp(3) defects and/or cross-linked structures in the polymer-an advantageous feature for the making of materials with improved photoluminescence efficiencies.

The Gilch Synthesis of Poly(p‐phenylene vinylenes): Mechanistic Knowledge in the Service of Advanced Materials

“…Examples are the Wessling, [26] sulfinyl, [27][28][29][30][31][32][33][34] sulfonyl, [35,36] xanthate, [37][38][39] dithiocarbamate, [40] Gilch, Heck, [69][70][71][72][73] Suzuki, [74,75] McMurry, [76] ring-opening metathesis, [77,78] acyclic diene metathesis, [79][80][81] Wittig, [82][83][84] Horner-Emmons, [85] Knoevenagel, [86] chemical vapor deposition, [87][88][89][90][91] and electropolymerization [92] methods. By assessing the pros and cons of all these approaches, the Gilch route stands out as one of the most powerful, versatile, and economically efficient approaches: simply by the treatment of a,a 0 -dihalogenated p-xylene derivatives 1 with potassium tert-butoxide (KO t Bu), high-molecular-weight PPVs 2 can be obtained in good to excellent yields (Scheme 1).…”

Photoionisation and photodissociation studies of nonvolatile organic molecules by synchrotron VUV photoionisation mass spectrometry and theoretical calculations

“…The stronger signal at m/z 44 suggests that the kinetic factor is predominant in controlling the rearrangement and reaction of the a-alanine cation [52]. In addition, the direct dissociation pathways which produce radicals are found to be entropically favoured, as reported by Deleuze and coworkers [109,110].…”

Effects of cross-linking methods for polyethylene-based carbon fibers: review

“…In this region, the maximum rates of change in % mass occurred from 440 to 480 K, depending on heating rate. At these temperatures, HOS 2 decomposed and H became the radical responsible for propagation of the will therefore increase the available amount of free radical to initiate the radical chain [87][88][89][90][91][92][93][94][95].…”