Angewandte
Chemie
(147 gmolÀ1). Gel permeation chromatography revealed the
molecular weight and polydispersity (Mw/Mn = 1.2) of the
starting material were not altered significantly during the
triflation and substitution reactions. Changes noted in the
NMR spectra for the silicone were also observed for the
alkane and fluorochemical SMAs. Matrix-assisted laser
desorption mass spectrometry and infrared spectroscopy
provided further evidence of the structure.
To demonstrate the versatility of this new concept in
surface modification, reactive ionic SMAs were applied to a
naturally produced biomaterial, a ceramic, and a synthetic
polymer. The reactive ionic silicone was applied to cellulose,
the reactive ionic wax was applied to glass, and the reactive
ionic fluorochemical was applied to nylon. In each case, the
substrate was first prepared by deprotonating surface hydroxy
and carboxy groups using a base. The reactive ionic SMA was
then applied to the surface by adsorption from solution. The
substrate was then washed or heated. Surfaces were analyzed
spectroscopically using attenuated total reflectance infrared
(ATR-IR) spectroscopy and macroscopically using contact
angle measurements or micrographs of water droplets. The
results are summarized in Figure 3 and Table 1. For the
reactive ionic silicone application (Figure 3a), adsorption
onto a cellophane surface was confirmed by the appearance of
ATR-IR peaks at 1257 and 790 cmÀ1 which are characteristic
of silicones. After washing the treated cellophane with
tetrahydrofuran (THF), these peaks disappeared indicating
the NPP-PDMS was not bonded to the substrate. However, if
the substrate is heated at 808C for 10 min and then washed
repeatedly, the silicone peaks remain. The cellulosic surface
has been permanently modified with a silicone.
The contact angle of a water droplet (1 mL) on a glass slide
is 19 Æ 58 (Table 1). After exposing the glass slide to base,
treating with the reactive ionic wax and washing, the contact
angle was unchanged at 22 Æ 38. If the glass slide is heated at
808C before washing, the water contact angle is 63 Æ 68,
indicating the surface is more hydrophobic due to the
presence of the alkane. The triflate intermediate could also
be used to modify the surface of glass, but the temporal
stability of triflates in solution is poor and surface reaction
depends on random collisions of the SMA with the surface as
opposed to the more directed adsorption made possible with
the NPP-functionalized SMAs due to complementary ionic
charges.
The reactive ionic fluorochemical was applied to a piece
of cationic-dyeable nylon carpet (Figure 3b). Deprotonation
of carboxy groups by base was followed by treatment with the
reactive ionic fluorochemical, heating and washing. A drop of
water placed on the surface of this nylon carpet remains on
the surface indefinitely with a contact angle greater than 1308.
The drop could be rolled around the surface by tilting the
carpet. Without treatment with the reactive ionic fluoro-
chemical, a water drop disappears into the substrate in less
than a second.
In addition to the examples presented here, we also expect
that reactive ionic chemistry will have applications in layer-
by-layer assembly protocols and modifying surfaces of a
variety of functional nanostructured materials.[11] We have
recently shown that it is also very effective to employ for
dyeing of films and fibers.[12] Reactive dyeing is practiced
world-wide using anionic dyes that are applied primarily to
anionically charged cellulosic fibers. To push exhaustion of
such dyes from solution, large quantities of electrolyte (up to
100 gLÀ1) must be added to the process bath, which makes for
a tremendous economic and environmental load. By incor-
porating a positively charged reactive ionic group into a
typical azo chromophore used in dyes, we showed that we
could produce a reactive dye that could be exhausted from the
processing bath at 98% without addition of any electrolyte.
The new reactive ionic dye was successfully applied to
cellophane and nylon 6,6 films, and to cotton and nylon
fabrics.
Figure 3. a) Attenuated-total-reflectance (ATR) infrared spectra of cello-
phane, cellophane treated with NPP-PDMS showing that this reactive
ionic silicone does adsorb to the surface, cellophane treated with NPP-
functionalized PDMS and then Soxhlet-extracted with tetrahydrofuran
(THF) showing that it is not permanent, and cellophane treated with
NPP-functionalized PDMS and then heated at 808C for 10 min and
then Soxhlet-extracted with THF showing that the surface modification
is permanent. Vertical dashed lines at 1257 and 790 cmÀ1 mark Si
À
CH3 vibrations characteristic of silicones. b) Micrographs of a piece of
nylon carpet after a drop of water (containing red dye for visualization)
was placed on the surface: untreated, and treated with NPP-function-
alized fluorochemical followed by heating and washing showing
permanent surface modification by this reactive ionic fluorochemical.
Received: October 1, 2011
Revised: November 28, 2011
Published online: January 16, 2012
Keywords: reactive ions · ring-opening · self-assembly ·
.
surface modification
Table 1: Reactive ionic wax applied to glass.
Glass slide
H2O contact angle
treated, heated, washed
treated, washed
untreated
63Æ68
22Æ38
19Æ58
Angew. Chem. Int. Ed. 2012, 51, 1849 –1852
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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