319
of Mw on surfactant have been studied. Gentle and Snow (1995) showed that
changes in the length of the polyether block do not have a significant impact on the
surfactant performance when ethylene oxide block repeat units were less than sixteen. However, surface adsorption decreased as the length of the ethylene oxide
block increased. This is probably due to an increase in water solubility of the surfactants. In fact, water soluble siloxanes are often highly desirable depending on the
application.
Such diblock surfactants (polyethers and siloxanes) are widely used in cosmetics, such as facial moisturizers, pharmaceuticals and shampoos (Kalasho et al.
2019; Guidi et al. 2014). In many of these cases, silicones are listed under commercial names, such as dimethicone or methicone. The use of the commercial names is
due largely in part to the backlash against silicone materials from the breast augmentation lawsuits of the late 1990s. Interestingly, there is no scientific evidence
that silicones were responsible for any of the health problems observed related with
them, and eventually the U. S. Institute of Medicine published a report exonerating
these materials (Bondurant et al. 1999).
Another important use of silicone surfactants is the preparation of PU foams.
Without the surfactants, the foams collapse providing an amorphous and generally
unusable product (Baferani et al. 2018; Zhang et al. 1999; Hasan et al. 2016).
Typically, instead of using traditional block-copolymers, PDMS with poly(ethylene
oxide)-co-poly(propylene oxide) (PEO-co-PPO) grafted chains are used. In the
preparation of PU materials, carbon dioxide is generated during polymerization. In
foams, the silicone surfactant stabilizes the gaseous bubbles produced within the
material and kinetically traps them in the PU. However, the activity of the silicone
surfactants plays an important role in the resulting bubble size, with a high silicone
content resulting in smaller bubble sizes (Zhang et al. 1999).
A new class of silicone surfactants made from silicone-polyol copolymers has
attracted the attention of many researchers, due to its interesting surface activities.
These copolymers are prepared very similarly to traditional PDMS-co-PEG copolymers, i.e. via hydrosilylation. Wang et al. (2017) demonstrated that one of these
surfactants (PDMS-b-poly(glycerol)) had comparable surface tensions (γ LV ~ 21
mN/m) to traditional siloxane surfactants, but with lower CACs. Another advantage
of these surfactants is that they can be derived from biorenewable sources, such as
polysaccharides or castor oil (Furtwengler and Avérous 2018; Mathew et al. 2018).
Hyaluronan-derived silicone surfactants have been studied by Paterson et al. (2014)
for their use as wetting agents for contact lens. The palm oil derived surfactants have
also been tested for the preparation of PU foams as a potential replacement for traditional PDMS-co-PEG surfactants (Nasir et al. 2016). The list of potential silicone
surfactants seems innumerable, and we note that the few examples selected only
provide a wide range of surfactants currently in use and development.
13 Synthetic Methods and Applications of Functional and Reactive Silicone Polymers
of Mw on surfactant have been studied. Gentle and Snow (1995) showed that
changes in the length of the polyether block do not have a significant impact on the
surfactant performance when ethylene oxide block repeat units were less than sixteen. However, surface adsorption decreased as the length of the ethylene oxide
block increased. This is probably due to an increase in water solubility of the surfactants. In fact, water soluble siloxanes are often highly desirable depending on the
application.
Such diblock surfactants (polyethers and siloxanes) are widely used in cosmetics, such as facial moisturizers, pharmaceuticals and shampoos (Kalasho et al.
2019; Guidi et al. 2014). In many of these cases, silicones are listed under commercial names, such as dimethicone or methicone. The use of the commercial names is
due largely in part to the backlash against silicone materials from the breast augmentation lawsuits of the late 1990s. Interestingly, there is no scientific evidence
that silicones were responsible for any of the health problems observed related with
them, and eventually the U. S. Institute of Medicine published a report exonerating
these materials (Bondurant et al. 1999).
Another important use of silicone surfactants is the preparation of PU foams.
Without the surfactants, the foams collapse providing an amorphous and generally
unusable product (Baferani et al. 2018; Zhang et al. 1999; Hasan et al. 2016).
Typically, instead of using traditional block-copolymers, PDMS with poly(ethylene
oxide)-co-poly(propylene oxide) (PEO-co-PPO) grafted chains are used. In the
preparation of PU materials, carbon dioxide is generated during polymerization. In
foams, the silicone surfactant stabilizes the gaseous bubbles produced within the
material and kinetically traps them in the PU. However, the activity of the silicone
surfactants plays an important role in the resulting bubble size, with a high silicone
content resulting in smaller bubble sizes (Zhang et al. 1999).
A new class of silicone surfactants made from silicone-polyol copolymers has
attracted the attention of many researchers, due to its interesting surface activities.
These copolymers are prepared very similarly to traditional PDMS-co-PEG copolymers, i.e. via hydrosilylation. Wang et al. (2017) demonstrated that one of these
surfactants (PDMS-b-poly(glycerol)) had comparable surface tensions (γ LV ~ 21
mN/m) to traditional siloxane surfactants, but with lower CACs. Another advantage
of these surfactants is that they can be derived from biorenewable sources, such as
polysaccharides or castor oil (Furtwengler and Avérous 2018; Mathew et al. 2018).
Hyaluronan-derived silicone surfactants have been studied by Paterson et al. (2014)
for their use as wetting agents for contact lens. The palm oil derived surfactants have
also been tested for the preparation of PU foams as a potential replacement for traditional PDMS-co-PEG surfactants (Nasir et al. 2016). The list of potential silicone
surfactants seems innumerable, and we note that the few examples selected only
provide a wide range of surfactants currently in use and development.
13 Synthetic Methods and Applications of Functional and Reactive Silicone Polymers