246
The pendant chloride groups may be replaced by azide groups, which can be
used to introduce polar groups via aza-click chemistry (Madsen et al. 2014c). In this
sense, Madsen et al. (2014b) synthesized functional silicones using chloropropyl
side-groups and allyl or vinyl end-groups via a Piers-Rubinsztajn reaction, where
the siloxane substrates were used to incorporate other functional groups via coppercatalyzed cycloaddition reactions between the azides and a variety of alkynes, while
the vinyl or allyl end-groups allow crosslinking via a hydrosilylation reaction.
Rambarran et al. (2013) reported a synthetic strategy that allows the sequential
functionalization of polysiloxanes with hydrophilic agents including carboxylic
acids, bromoalkylesters and oligo(ethylene oxides) using a simple metal- free click
reaction (Table 11.4, entry 2). Wang et al. (2015) also synthesized a graft side-chain
liquid-crystalline polymer (Table 11.4, entry 3) using chloropropyl substituted polysiloxane as a backbone and poly(6-(4′-octyloxyphenyl-4″-benzoyl)hexylacrylate)
(a LC polymer -LCP) as the side chain via atom transfer radical polymerization
(ATRP) technique. Similarly, Lu et al. (2013) prepared polymers consisting of
oligo(dimethylsiloxane) and oligothiophene units arranged alternately from α,ωdibromooligo(dimethylsiloxane). The latter was obtained by Pd-catalyzed dehydrobromination of α,ω-dihydrooligo(dimethylsiloxane) with isopropyl bromide
(Table 11.4, entry 4). Miyauchi et al. (2015) obtained a polysilsesquioxane (PSQ)
containing phthalimido side-chain groups with good solubility and high thermal
stability by a two-step reaction (Table 11.4, entry 5).
Other less common synthetic routes have also been explored for functional silicones. Gretton et al. (2012) used Piers-Rubinsztajn reaction to obtain hydrolytically
stable silicone polymers with pendant triarylamine functional groups. De Bruycker
et al. (2019) linked thiolactone units to polysiloxanes to prepare bivalent or a multivalent thiolactone-functional silicone as the hydrophobic component of an amphiphilic network (Table 11.4, entry 6). They used thiolactone-based conjugation
chemistry as a new crosslinking strategy for the preparation of PDMS based amphiphilic co-networks, where commercial polyethylene glycol (PEG) diacrylates of
various chain lengths were selected as hydrophilic cross-linkers, which should react
quickly with the thiols that are generated by the aminolysis of the thiolactone units,
thus by adding of an amine in the polymer mixtures, the thiolactone segment generated thiol groups via aminolysis, which reacted further with the acrylates in the
mixtures. The crosslinking reactions were quick and efficient at room temperature
(RT), which led to the formation of transparent elastomers.
Zhao et al. (2019) reported the reaction of 3-aminopropyl di- or multi-functional
silicones with 2-furoyl chloride or maleic anhydride (Table 11.4, entry 7). These
authors reported that silicone oligomers obtained with reactive motifs were crosslinked by dynamic Diels–Alder bonds. By incorporating graphene nanosheets into
polysiloxane elastomer, self-curable nanocomposites were obtained with a significantly improved maximum stress (σ m ) and excellent electromechanical properties to
be used as pressure sensor.
Dendrimers and dendrons are monodisperse macromolecules with precise structure and self-assembly, comparable with those of biological molecules and macromolecules. Percec’s group discussed and reviewed the hyperbranched functional
polysiloxanes with various structures in Rosen et al. (2009).
C. Racles et al.
The pendant chloride groups may be replaced by azide groups, which can be
used to introduce polar groups via aza-click chemistry (Madsen et al. 2014c). In this
sense, Madsen et al. (2014b) synthesized functional silicones using chloropropyl
side-groups and allyl or vinyl end-groups via a Piers-Rubinsztajn reaction, where
the siloxane substrates were used to incorporate other functional groups via coppercatalyzed cycloaddition reactions between the azides and a variety of alkynes, while
the vinyl or allyl end-groups allow crosslinking via a hydrosilylation reaction.
Rambarran et al. (2013) reported a synthetic strategy that allows the sequential
functionalization of polysiloxanes with hydrophilic agents including carboxylic
acids, bromoalkylesters and oligo(ethylene oxides) using a simple metal- free click
reaction (Table 11.4, entry 2). Wang et al. (2015) also synthesized a graft side-chain
liquid-crystalline polymer (Table 11.4, entry 3) using chloropropyl substituted polysiloxane as a backbone and poly(6-(4′-octyloxyphenyl-4″-benzoyl)hexylacrylate)
(a LC polymer -LCP) as the side chain via atom transfer radical polymerization
(ATRP) technique. Similarly, Lu et al. (2013) prepared polymers consisting of
oligo(dimethylsiloxane) and oligothiophene units arranged alternately from α,ωdibromooligo(dimethylsiloxane). The latter was obtained by Pd-catalyzed dehydrobromination of α,ω-dihydrooligo(dimethylsiloxane) with isopropyl bromide
(Table 11.4, entry 4). Miyauchi et al. (2015) obtained a polysilsesquioxane (PSQ)
containing phthalimido side-chain groups with good solubility and high thermal
stability by a two-step reaction (Table 11.4, entry 5).
Other less common synthetic routes have also been explored for functional silicones. Gretton et al. (2012) used Piers-Rubinsztajn reaction to obtain hydrolytically
stable silicone polymers with pendant triarylamine functional groups. De Bruycker
et al. (2019) linked thiolactone units to polysiloxanes to prepare bivalent or a multivalent thiolactone-functional silicone as the hydrophobic component of an amphiphilic network (Table 11.4, entry 6). They used thiolactone-based conjugation
chemistry as a new crosslinking strategy for the preparation of PDMS based amphiphilic co-networks, where commercial polyethylene glycol (PEG) diacrylates of
various chain lengths were selected as hydrophilic cross-linkers, which should react
quickly with the thiols that are generated by the aminolysis of the thiolactone units,
thus by adding of an amine in the polymer mixtures, the thiolactone segment generated thiol groups via aminolysis, which reacted further with the acrylates in the
mixtures. The crosslinking reactions were quick and efficient at room temperature
(RT), which led to the formation of transparent elastomers.
Zhao et al. (2019) reported the reaction of 3-aminopropyl di- or multi-functional
silicones with 2-furoyl chloride or maleic anhydride (Table 11.4, entry 7). These
authors reported that silicone oligomers obtained with reactive motifs were crosslinked by dynamic Diels–Alder bonds. By incorporating graphene nanosheets into
polysiloxane elastomer, self-curable nanocomposites were obtained with a significantly improved maximum stress (σ m ) and excellent electromechanical properties to
be used as pressure sensor.
Dendrimers and dendrons are monodisperse macromolecules with precise structure and self-assembly, comparable with those of biological molecules and macromolecules. Percec’s group discussed and reviewed the hyperbranched functional
polysiloxanes with various structures in Rosen et al. (2009).
C. Racles et al.