Sonication-induced conformation transitions may influence the supramolecular
interactions and further affect the gelation processes. In one study, Naota and
co-workers demonstrated that dinuclear palladium(II) complex gelator 29
(Scheme 2.5) undergoes sol–gel transition with sonication for 3–10 s along with
the structural transformation from self-locked intramolecular p–p stacking to
interlocked intermolecular p–p stacking (Fig. 2.21) [105]. In an ALS system, Yi
N
H
NH
C 4 H 9
O
O
C 12 H 25
O
NH
C 4 H 9
27
N
O
N
O
H
N
N
H
3
O
O
O
N
H
R
O
28
N
O
N
O
O
H
N
O
H
N
O
O
30
N
N
N
Pt
N
O
O
NH
O
O
H
H H
CF 3 SO 3
31
N
O
N
O
O
NH
NH
O
O
NH
O
HO
H
OH
OH
32
O
Pd N
N
O
N
Pd
O
O
N
(CH 2 ) 5
(H 2 C) 5
29
Scheme 2.5 Chemical structures of gelators 27–32
Fig. 2.19 SEM micrographs of propylene glycol gels of 27, a after a heating–cooling cycle and
b with additional ultrasound treatment (b) (scale bars 500 nm). Reprinted with the permission from
Ref. [101]. Copyright 2009 American Chemical Society
2.3 Sonication and Mechanical Stress Responsive Gels
31