Rheological properties of poly(1-trimethylsilyl-1-propyne) solutions

Abstract

The phase state and rheological properties of poly(1-trimethylsilyl-1-propyne) solutions in toluene and cyclohexane are studied. Samples of poly(1-trimethylsilyl-1-propyne) have the same backbone structure (cis-trans configuration ratio) but different molecular masses. Phase diagrams of these systems are derived via optical interferometry. It is found that they have an upper critical mixing temperature (UCMT) whose value exceeds the boiling points of the individual solvents. The two solvents exhibit limited solubility with respect to the studied polymer, and this parameter decreases with an increase in the molecular mass of the polymer. In the transition from dilute to concentrated solutions, the pattern of the rheological behavior changes from Newtonian to pseudoplastic. The concentration dependences of the zero-shear-rate viscosity of the solutions are typical for flexible-chain polymers. The viscous behavior of the poly(1-trimethylsilyl-1-propyne)-solvent system can be described through a single generalized viscosity-concentration relationship if dimensionless reduced values that take into account the contribution of the molecular mass, the nature of the solvent, and the pattern of intermolecular interactions in the solutions are used as the argument and the function.