263
(Braunmuhl et al. 1995; Wagner et al. 1996b, 1997), transacetalation (Ogawa 2003),
glycosidation with epoxy-siloxanes catalyzed by a cation exchanger (Racles and
Cozan 2012), click chemistry (Halila et al. 2008), or glucamine reaction using polysiloxanes modified with activated ester (Moukarzel et al. 2013). Lipase catalyzed
esterification between ethylglucoside and diacid terminated siloxanes was also
reported by Sahoo et al. (2005). The regioselective formation of ester bonds involving the primary hydroxyl group of ethylglucoside is produced in a one-step reaction
carried out under mild conditions without protection-deprotection steps or activation of the acid groups, with the integrity of the siloxane bonds. The reaction of
poly(3-aminopropyl)siloxane with fatty acid chlorides, followed by the reaction
with gluconolactone gave amphiphilic polysiloxanes with an aggregation behavior
tuned by the structures and functionalities of the hydrophobic parts (Iwakiri
et al. 2009).
Several recent and atypical applications of amphiphilic siloxanes have been
developed. Hetzer et al. (2014) designed a siloxane surfactant as fluorine-free aqueous film-forming foams for fire extinguishing agents for pool fires. Silicones of
different architecture modified by addition reactions onto epoxide groups have also
been explored as surface active materials with applicative potential in various directions. These contain tris(hydroxymethyl)aminomethane (known as tromethamol or
Tris -buffer) (Racles 2010) or p-aminopyridine (Racles et al. 2018) as hydrophilic
groups, which act also as ligands for metals (Racles et al. 2012, 2014e). Excellent
surfactant skills have been demonstrated for the first set of materials, in stabilization
of polymer or metal oxide NPs (Racles et al. 2011, 2014c; Racles 2013) and micellar solubilization of a hydrophobic drug (Racles et al. 2014d), while the latter
showed phase transfer properties (Racles et al. 2018), based on the encapsulation of
hydrophilic molecules in their vesicles. The variation of chemical structure, in particular the length of the polysiloxane chain, allows to tune the solubility and surfactant properties in organic solvents, with applications in polymer-polymer composites
(Racles et al. 2015a, b). Carbon nanotubes have also been efficiently dispersed into
nonpolar organic solvents using amphiphilic molecules composed of long siloxane
tails and pyrene or porphyrin, which were chosen based on their affinity for the
surface of graphene nanotubes (Ji et al. 2009). Following Ji et al. (2009) these compounds offered superior stabilization than those containing C 18 carbon tails and
imparted compatibility with the polysiloxane elastomer matrix. Carbohydratecontaining cyclosiloxane surfactants have also been used by Racles et al. (2010a)
for the preparation of silver NPs with a tunable size. Gold nanochains can also be
obtained with a siloxane surfactant (Jia et al. 2011); the 1D assembly of gold NPs
depends on the surfactant concentration and ionic strength.
11.6 Functional Silicones for Biomedical Applications
Siloxanes have been used in many consumer products for a long time. However,
there is little information available about its toxicity, and the existing one is mainly
limited to widely used, unmodified cyclosiloxanes (mainly D 4 and D 5 ),
11 Reactive and Functional Silicones for Special Applications
(Braunmuhl et al. 1995; Wagner et al. 1996b, 1997), transacetalation (Ogawa 2003),
glycosidation with epoxy-siloxanes catalyzed by a cation exchanger (Racles and
Cozan 2012), click chemistry (Halila et al. 2008), or glucamine reaction using polysiloxanes modified with activated ester (Moukarzel et al. 2013). Lipase catalyzed
esterification between ethylglucoside and diacid terminated siloxanes was also
reported by Sahoo et al. (2005). The regioselective formation of ester bonds involving the primary hydroxyl group of ethylglucoside is produced in a one-step reaction
carried out under mild conditions without protection-deprotection steps or activation of the acid groups, with the integrity of the siloxane bonds. The reaction of
poly(3-aminopropyl)siloxane with fatty acid chlorides, followed by the reaction
with gluconolactone gave amphiphilic polysiloxanes with an aggregation behavior
tuned by the structures and functionalities of the hydrophobic parts (Iwakiri
et al. 2009).
Several recent and atypical applications of amphiphilic siloxanes have been
developed. Hetzer et al. (2014) designed a siloxane surfactant as fluorine-free aqueous film-forming foams for fire extinguishing agents for pool fires. Silicones of
different architecture modified by addition reactions onto epoxide groups have also
been explored as surface active materials with applicative potential in various directions. These contain tris(hydroxymethyl)aminomethane (known as tromethamol or
Tris -buffer) (Racles 2010) or p-aminopyridine (Racles et al. 2018) as hydrophilic
groups, which act also as ligands for metals (Racles et al. 2012, 2014e). Excellent
surfactant skills have been demonstrated for the first set of materials, in stabilization
of polymer or metal oxide NPs (Racles et al. 2011, 2014c; Racles 2013) and micellar solubilization of a hydrophobic drug (Racles et al. 2014d), while the latter
showed phase transfer properties (Racles et al. 2018), based on the encapsulation of
hydrophilic molecules in their vesicles. The variation of chemical structure, in particular the length of the polysiloxane chain, allows to tune the solubility and surfactant properties in organic solvents, with applications in polymer-polymer composites
(Racles et al. 2015a, b). Carbon nanotubes have also been efficiently dispersed into
nonpolar organic solvents using amphiphilic molecules composed of long siloxane
tails and pyrene or porphyrin, which were chosen based on their affinity for the
surface of graphene nanotubes (Ji et al. 2009). Following Ji et al. (2009) these compounds offered superior stabilization than those containing C 18 carbon tails and
imparted compatibility with the polysiloxane elastomer matrix. Carbohydratecontaining cyclosiloxane surfactants have also been used by Racles et al. (2010a)
for the preparation of silver NPs with a tunable size. Gold nanochains can also be
obtained with a siloxane surfactant (Jia et al. 2011); the 1D assembly of gold NPs
depends on the surfactant concentration and ionic strength.
11.6 Functional Silicones for Biomedical Applications
Siloxanes have been used in many consumer products for a long time. However,
there is little information available about its toxicity, and the existing one is mainly
limited to widely used, unmodified cyclosiloxanes (mainly D 4 and D 5 ),
11 Reactive and Functional Silicones for Special Applications