Macroinitiators were prepared by coupling disuccinimidyl ester of 4,4'-azob
is(cyanovaleric acid) with poly(N-isopropylacrylamide) (PIPA), which had an
amino group at its end. Styrene was telomerized with the initiators in THF
. When the styrene content in the A-B-A block telomer obtained (PIPA-b-PSt-
b-PIPA) was high, the telomer formed an irreversible aggregation resulting
in microspheres, whereas the telomer with a much shorter styrene block coul
d be dispersed monomolecularly, The telomers dispersed in water were aggreg
ated by raising the temperature above 32 degrees C due to a coil-globule tr
ansition of PIPA moieties. The PIPA-b-PSt-b-PIPA could be strongly adsorbed
to polystyrene (PSt) solid surfaces to form a layer, and the PSt blocks mi
ght lay on the PSt surface and the PIPA blocks might direct to the solution
phase. The contact angle of air bubbles on the surface of telomer-coated P
St in the air-in-water system was dependent on temperature; that is, with t
he increase in temperature the contact angle of air bubbles largely decreas
ed and leveled off above the coil-globule transition temperature (T-c). Cor
respondingly, the amount of protein Concanavalin A adsorbed to the telomer
layer deposited on the PSt surface increased gradually with an increase in
temperature and leveled off above the T-c. These phenomena were attributed
to the changes in hydrophobicity of the telomer layer below and above the T
-c. The usefulness of macroinitiators in preparing various kinds of block t
elomers which have responsiveness to external stimuli was strongly suggeste
d. (C) 1999 Academic Press.