Dilational rheology of monolayers of a miscible polymer blend: From good- to poor-solvent conditionsS. Rivillon, F. Monroy, F. Ortega and R.G. Rubio
Departamento Química Física I, Facultad de Química, Universidad Complutense, E-28040 Madrid, Spain firstname.lastname@example.org
(Received 7 June 2002 and Received in final form 5 November 2002 / Published online: 30 January 2003)
The viscoelastic moduli (elasticity and dilational viscosity) of monolayers of PVAc + P4HS has been studied over a broad frequency range (0.1 mHz-200 kHz) using a combination of relaxation and capillary-waves techniques. The analysis of the surface pressure, the elasticity and the viscosity on the semidilute regime show that the air-water interface is a good solvent for the monolayers of PVAc-rich blends, and a poor (near- ) solvent for the monolayers of P4HS-rich blends. The solvent quality changes continuously over a broad concentration range. The results of viscoelastic moduli show that there is a broad relaxation process in the low-frequency range ( Hz). While for PVAc-rich monolayers this relaxation process follows the reptation-like behavior described by Noskov, for P4HS-rich monolayers the model does not describe the amplitudes of the different relaxation modes. For PVAc-rich monolayers two processes are clearly distinguished at higher frequencies: one centered at around 500 Hz and another one at around 40 kHz. However, for P4HS-rich monolayers only one broad relaxation mode is found below 1 kHz. The crossover from one type of behavior to the other one takes place in a very narrow blend-composition range, and is not clearly related to the crossover from good- to poor-solvent condition.
68.03.Kn - Dynamics (capillary waves).
05.70.Fh - Phase transitions: general studies.
64.70.Dv - Solid-liquid transitions.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002