Premium
Structure and viscoelasticity of interacting spherical brushes
Author(s) -
Vlassopoulos Dimitris,
Kapnistos Michael,
Fytas George,
Roovers Jacques
Publication year - 2000
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200008)158:1<149::aid-masy149>3.0.co;2-g
Subject(s) - viscoelasticity , colloid , polymer , spheres , chemical physics , materials science , hysteresis , diffusion , relaxation (psychology) , swelling , shear (geology) , thermodynamics , chemistry , composite material , condensed matter physics , physics , psychology , social psychology , astronomy
Star polymers with a high functionality of 128 are viewed as ideal spherical brushes with soft colloidal character, encompassing both polymer‐like short range and colloid‐like long range interactions. We have identified three mechanisms for relaxing the concentration and density fluctuations in semidilute solution: cooperative diffusion, characteristic of polymers, and self‐diffusion and structural relaxation, characteristics of colloidal hard spheres. Upon heating these systems undergo a reversible liquid‐solid transition, yielding weak gels. It is attributed to the trapping of the spheres in “cages” due to the swelling with temperature and hence stronger arm interpenetration. At the transition strong hysteresis phenomena are observed during steady and transient shear measurements, and relate to the changing viscoelastic character of the fluid with temperature.