DOI: 10.1140/epje/i2002-10094-0
Dilational rheology of monolayers of a miscible polymer blend: From good- to poor-solvent conditions
S. Rivillon, F. Monroy, F. Ortega and R.G. RubioDepartamento Química Física I, Facultad de Química, Universidad Complutense, E-28040 Madrid, Spain rgrubio@quim.ucm.es
(Received 7 June 2002 and Received in final form 5 November 2002 / Published online: 30 January 2003)
Abstract
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
