An in depth study of solvent effects on yield and average molecular weight in poly(3-hexylthiophene)

Extended 2,2′-Bipyrroles: New Monomers for Conjugated Polymers with Tailored Processability

“…Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) spectrometry was used to confirm the formation of oligomers during the electropolymerization [39,40,41]. Figure 4 shows MALDI-TOF spectra of the cyclic voltammetry media of each 2,2′-bipyrrole monomer revealing differences in the oligomer molecular weight distribution.…”

Enabling Conducting Polymer Applications: Methods for Achieving High Molecular Weight in Chemical Oxidative Polymerization in Alkyl- and Ether-Substituted Thiophenes

“…This decrease in yields may be due to the acetonitrile present in the reaction mixture, even though the total acetonitrile volume is only approximately 15% ( v / v ) of the solution. A byproduct of the reaction, FeCl 2 , is much more soluble in acetonitrile (3 × 10 −2 M) than in conventionally used halogenated solvents (5 × 10 −14 M for chloroform) [ 36 ]. The much higher concentration of FeCl 2 dissolved in the reaction solvent results in a decrease in the oxidation potential of the solution, which can suppress the oxidation of monomers and oligomers and hinder the growth of new polymer chains, thus reducing yields [ 36 , 41 ].…”

“…It is important to note that there is considerable variability in the molecular weights reported for polymers prepared under similar conditions [ 20 , 36 ], for example, P3HT synthesized in chloroform with four equivalents of FeCl 3 (entries 2 and 3 in Table 1 ). Some of this variability can be attributed to discrepancies between the amounts of solvent used and whether the solvent contains a radical inhibitor (for example, ethanol in chloroform).…”

“…Under reverse conditions, the opposite occurs. The original publication by Sugimoto et al [ 11 ] describes polymerization of 3-hexylthiophene under reverse addition conditions, and the bulk of other studies are carried out in this fashion [ 16 , 17 , 18 , 19 , 26 , 31 , 36 , 37 , 38 , 40 , 43 , 44 , 45 ].…”

“…An alternative is to simply perform the reaction in a good solvent for the oxidant. However, the polar solvents in which FeCl 3 is soluble are typically poor solvents for polythiophenes, which can lead to significantly decreased molecular weights [ 19 , 36 ]. Herein, we describe a modified standard addition method that addresses these issues and evaluate the impact of order of addition, solvent composition, oxidant concentration, and reaction time on degree of polymerization of two different ether-substituted polythiophenes, poly(2-dodecyl-2H,3H-thieno [3,4-b][1,4]dioxine) (PEDOT-C12) and poly(3,4-bis(hexyloxy)thiophene) (PBHOT) in comparison with P3HT ( Figure 3 ).…”