Hydrodynamic properties and conformation of poly(3-hexylthiophene) in dilute solutions

Abstract

Conducting polymers demonstrate low solubility in organic solvents. Introducing aliphatic substituents into polymer chains improves their solubility, but may also lead to changes in conformational characteristics of macromolecules. In the present work, the studies of hydrodynamic properties and conformational characteristics of comb-shaped poly(3-hexylthiophene) with aliphatic side substituents were carried out in chloroform solutions. Conformational analysis of the studied macromolecules was performed for the first time using homologous series with a wide range of molecular weights of the polymers in dilute solutions. The hydrodynamic properties of these macromolecules were interpreted using the worm-like spherocylinder model and the straight spherocylinder model. The projection of the monomer unit in the direction of the main polymer chain k 5 0.37 nm was determined experimentally. The following parameters of poly(3-hexylthiophene) were characterized and quantified: equilibrium rigidity (Kuhn segment length) ff 5 6.7 nm and hydrodynamic diameter of a polymer chain d 5 0.6 nm.

Molecular dynamics simulation of poly(3‐hexylthiophene) helical structure In Vacuo and in amorphous polymer surrounding

“…In the Table, the values of the persistence length and the Kuhn segment are also shown, calculated by substituting the obtained values of and to eqs and , and by numerical solution of these equations for the Gromos, Amber, and OPLS‐AA force fields. Comparison of these results with the experimental data, obtained by McCulloch and Ho ( A exp = 6 ± 1 nm) and Yakimansky et al ( A exp = 6.0 ± 0.6 nm from rotational friction experiments and A exp = 6.7 ± 0.7 nm from translational friction experiments), suggests that the flexibility of P3HT chains is highly overestimated when using the OPLS‐AA force field. This fact confirms the earlier assumption that the model based on this force field describes the studied systems inadequately.…”

Molecular Dynamics Simulation of Amorphous Poly(3-hexylthiophene)

“…To the best of our knowledge, the conformational properties of RR-P3HT have been examined only in solutions 40,52,78 of rather good solvents, and thus, they cannot be used for direct comparison with the MD results of the present study; nonetheless, they can serve as a guide for a qualitative evaluation of the simulation data. Yakimansky et al 78 measured the monomer repeat unit length of P3HT in chloroform using dynamic light scattering (DLS) and found it to be equal to 3.7 Å at 298 K. Heffner and Pearson 52 examined dilute P3HT solutions using DLS, gel permeation chromatography, and viscosity measurements.…”

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

“…Thus, it may be concluded that the Kuhn model gives neither real mass distribution within molecules nor realistic conformations of P3HT chains. In Yakimansky et al . an attempt was made to compensate this inadequacy of the Kuhn model, using the d V value (determined from the partial specific volume of a polymer ) instead of the segment hydrodynamic diameter d Kuhn .…”