TY - JOUR
T1 - Chains end-grafted in a theta-solvent and polymer melts
T2 - Comparison of force-distance profiles
AU - Cai, Lenore Lijun
AU - Granick, Steve
N1 - Funding Information:
We are indebted to Professor Hiroshi Watanabe (Kyoto University) for the gift of a polymer sample. This work was supported by the National Science Foundation (Tribology Program).
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2001/11/15
Y1 - 2001/11/15
N2 - We find an unexpected analogy between polymer melts compressed between strongly-attractive solid surfaces, and end-attached polymers in near-theta-solvent. End-grafted polystyrene (PS) chains with various graft density were produced by immersing mica, coated with adsorbed diblock copolymers of PS/PVP, PS/polyvinylpyiridine, into trans-decalin at 24°C (this solvent is a near-theta-solvent for PS but a non-solvent for PVP), and the force-distance relations were measured using a surface forces apparatus. The end-grafted PS chains repelled one another in spite of the theta-solvent situation. Repulsive forces began at a thickness, per adsorbed layer, equivalent to 4-5 times the unperturbed radius of gyration of the PS chain. These cases of symmetrically-opposed PS layers are compared to the asymmetric case (PS on one mica surface, the other mica surface bare) and to the case of adsorbed PS homopolymer. Force-distance profiles in the presence of unattached PS homopolymer in solution at concentration c* (the overlap concentration) displayed repulsion beginning at considerably larger separation than in the presence of pure solvent. Finally, we compare to confined melts of linear polydimethylsiloxane (PDMS), cyclic PDMS and a linear perfluoropolyether (Demnum). For these cases of polymer melts confined between adsorbing surfaces, force-distance relations could be described by the same functional relations as for end-attached chains in near-theta-solvent.
AB - We find an unexpected analogy between polymer melts compressed between strongly-attractive solid surfaces, and end-attached polymers in near-theta-solvent. End-grafted polystyrene (PS) chains with various graft density were produced by immersing mica, coated with adsorbed diblock copolymers of PS/PVP, PS/polyvinylpyiridine, into trans-decalin at 24°C (this solvent is a near-theta-solvent for PS but a non-solvent for PVP), and the force-distance relations were measured using a surface forces apparatus. The end-grafted PS chains repelled one another in spite of the theta-solvent situation. Repulsive forces began at a thickness, per adsorbed layer, equivalent to 4-5 times the unperturbed radius of gyration of the PS chain. These cases of symmetrically-opposed PS layers are compared to the asymmetric case (PS on one mica surface, the other mica surface bare) and to the case of adsorbed PS homopolymer. Force-distance profiles in the presence of unattached PS homopolymer in solution at concentration c* (the overlap concentration) displayed repulsion beginning at considerably larger separation than in the presence of pure solvent. Finally, we compare to confined melts of linear polydimethylsiloxane (PDMS), cyclic PDMS and a linear perfluoropolyether (Demnum). For these cases of polymer melts confined between adsorbing surfaces, force-distance relations could be described by the same functional relations as for end-attached chains in near-theta-solvent.
KW - Adsorption
KW - Force-distance
KW - Polymer melt
KW - Polystyrene (PS) chains
KW - Surface
KW - Theta-solvent
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U2 - 10.1016/S0001-8686(01)00058-6
DO - 10.1016/S0001-8686(01)00058-6
M3 - Article
AN - SCOPUS:0035889735
SN - 0001-8686
VL - 94
SP - 135
EP - 150
JO - Advances in Colloid and Interface Science
JF - Advances in Colloid and Interface Science
IS - 1-3
ER -