transparency and high resistance to YAG laser exposure at 355 nm make the
coatings obtained from polymer B-S6, S22 (Table 12.1) promising for use as
optical fiber gratings [58].
12.4.2.4 Polymers with Nitrogen-Containing Side Groups
Nitrogen-containing organic side groups can add new chemical or physical properties to polysiloxanes. In particular, amine-functionalized polysiloxanes can act as
ligands for metal ions or particles and thus can be used, e.g., for extraction of toxic
metal ions from wastewater [63], as supports for metallic catalysts [64, 65] or as
stabilizers for metal nanoparticles [66]. After transformation into quaternary
ammonium salts (QAS), they exhibit antimicrobial properties [67].
Unfortunately, direct hydrosilylation of unsaturated amines in the presence of Pt
catalysts may be accompanied by the undesired side processes that result in
polymer cross-linking due to the reaction between Si–H and N–H groups or catalyst
poisoning [68]. These problems may be avoided if protected amines are hydrosilylated. Thus, Binet et al. [69] reacted PHMS-DMS copolymer simultaneously with
N-tertbutoxycarbonyl (t-Boc) allylamine and dodec-1-ene at 70 °C using
(Et 2 S) 2 PtCl 2 as catalyst and toluene as solvent. The reaction product contained
t-Boc aminopropyl side group. Its deprotection with trimethylsilyliodide (solution
in dichloromethane, strictly anhydrous conditions −10 °C) afforded aminopropyl
and dodecyl side group-modified polysiloxane. The expected structures of the
functionalized polymers before and after deprotection of amine groups were
established by
1 H and
13 C NMR spectroscopies.
In the literature there are, however, also reports on successful direct hydrosilylation of amines. Kanjilal et al. [70] performed the reaction of PHMS with various
amounts of allylcyclohexylamine (H 2 PtCl 6 catalyst, toluene, 70 °C). The authors
found by
1 H NMR spectroscopy that it was possible to quantitatively substitute the
targeted amount of Si–H groups in PHMS.
1 H NMR spectrum corresponding to the
polymer of the highest functionalization level showed no signals due to protons
attached to carbon atoms of C=C bond (d = *5–6 ppm) or protons of Si–H groups
(d = 4.8 ppm), whereas several lines of chemical shift values below 3 ppm,
attributed to cyclohexylamine moieties (Table 12.1, S23), were visible. Similarly,
in the FTIR spectrum there was no band at *2100 cm
−1 (Si–H bond), but there
were bands proving incorporation of cyclohexylamine groups. Using
cyclohexylamine-functionalized polymers, membranes on porous polyethylene
supports were fabricated. They exhibited good separation factors in the pervaporative enrichment of propane-1,3-diol concentration from binary aqueous solutions.
Guerra-Contreras et al. [71] and Lei et al. [72] hydrosilylated N,N-dimethylallylamine (DMAA), i.e., a tertiary amine, with PHMS-DMS copolymers
(Karstedt’s catalyst, anhydrous toluene, 90–100 °C) which afforded
amine-substituted polysiloxanes (Table 12.1, polymer B-S12 and B-S24). The
processes were continued until the Si–H band disappeared from the FTIR spectrum
of the reaction mixture. Then Lei et al. [72] introduced PDMS blocks at both
12 Application of Spectroscopic Methods in the Studies …
379
coatings obtained from polymer B-S6, S22 (Table 12.1) promising for use as
optical fiber gratings [58].
12.4.2.4 Polymers with Nitrogen-Containing Side Groups
Nitrogen-containing organic side groups can add new chemical or physical properties to polysiloxanes. In particular, amine-functionalized polysiloxanes can act as
ligands for metal ions or particles and thus can be used, e.g., for extraction of toxic
metal ions from wastewater [63], as supports for metallic catalysts [64, 65] or as
stabilizers for metal nanoparticles [66]. After transformation into quaternary
ammonium salts (QAS), they exhibit antimicrobial properties [67].
Unfortunately, direct hydrosilylation of unsaturated amines in the presence of Pt
catalysts may be accompanied by the undesired side processes that result in
polymer cross-linking due to the reaction between Si–H and N–H groups or catalyst
poisoning [68]. These problems may be avoided if protected amines are hydrosilylated. Thus, Binet et al. [69] reacted PHMS-DMS copolymer simultaneously with
N-tertbutoxycarbonyl (t-Boc) allylamine and dodec-1-ene at 70 °C using
(Et 2 S) 2 PtCl 2 as catalyst and toluene as solvent. The reaction product contained
t-Boc aminopropyl side group. Its deprotection with trimethylsilyliodide (solution
in dichloromethane, strictly anhydrous conditions −10 °C) afforded aminopropyl
and dodecyl side group-modified polysiloxane. The expected structures of the
functionalized polymers before and after deprotection of amine groups were
established by
1 H and
13 C NMR spectroscopies.
In the literature there are, however, also reports on successful direct hydrosilylation of amines. Kanjilal et al. [70] performed the reaction of PHMS with various
amounts of allylcyclohexylamine (H 2 PtCl 6 catalyst, toluene, 70 °C). The authors
found by
1 H NMR spectroscopy that it was possible to quantitatively substitute the
targeted amount of Si–H groups in PHMS.
1 H NMR spectrum corresponding to the
polymer of the highest functionalization level showed no signals due to protons
attached to carbon atoms of C=C bond (d = *5–6 ppm) or protons of Si–H groups
(d = 4.8 ppm), whereas several lines of chemical shift values below 3 ppm,
attributed to cyclohexylamine moieties (Table 12.1, S23), were visible. Similarly,
in the FTIR spectrum there was no band at *2100 cm
−1 (Si–H bond), but there
were bands proving incorporation of cyclohexylamine groups. Using
cyclohexylamine-functionalized polymers, membranes on porous polyethylene
supports were fabricated. They exhibited good separation factors in the pervaporative enrichment of propane-1,3-diol concentration from binary aqueous solutions.
Guerra-Contreras et al. [71] and Lei et al. [72] hydrosilylated N,N-dimethylallylamine (DMAA), i.e., a tertiary amine, with PHMS-DMS copolymers
(Karstedt’s catalyst, anhydrous toluene, 90–100 °C) which afforded
amine-substituted polysiloxanes (Table 12.1, polymer B-S12 and B-S24). The
processes were continued until the Si–H band disappeared from the FTIR spectrum
of the reaction mixture. Then Lei et al. [72] introduced PDMS blocks at both
12 Application of Spectroscopic Methods in the Studies …
379