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 lambda=50.37 nm was determined experimentally. The following parameters of poly(3-hexylthiophene) were characterized and quantified: equilibrium rigidity (Kuhn segment length) A=6.7 nm and hydrodynamic diameter of a polymer chain d=0.6 nm. (C) 2016 Wiley Periodicals, Inc.