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Direct Functionalization of Poly(spirophosphazene)s via the Regioselective Lithiation of the Aromatic Rings Using a Cooperative Superbase
Author(s) -
de la Campa Raquel,
García Diego,
Rodríguez Sandra,
Carriedo Gabino A.,
Presa Soto Alejandro
Publication year - 2017
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.201700039
Subject(s) - polyphosphazene , superbase , regioselectivity , lithium (medication) , chemistry , aromaticity , electrophile , surface modification , polymer , solubility , polymer chemistry , copolymer , crystallography , organic chemistry , molecule , medicine , endocrinology , catalysis
The direct chemical functionalization of poly(spirophosphazene) [NP(O 2 C 12 H 8 )] n ( 1 ) can be performed by the lithiation of the aromatic rings at low temperature using Schlosser's base (Li t Bu/KO t Bu or “superbase”), and the subsequent reaction with various electrophiles such as ClSiMe 3 , ClPPh 2 , or MeOB(O 2 C 6 H 12 ) (MeOBpin). The functionalized polymers, isolated in very high yields (>90%) and without degradation of the polymeric chains, have an average degree of substitution per repeat unit ranging from 0.3 (random copolymers) to a maximum of 1.0, which corresponds to the homopolymers [NP(O 2 C 12 H 7 FG)] n (FG (functional group) =SiMe 3 , PPh 2 , and Bpin). NMR studies, including bidimensional high temperature experiments on silylated and deuterated polymers, show that the substitution is regioselectively occurring at the C 3 carbon of the aromatic rings due to the coordination of the lithium cations to the nitrogen of the polyphosphazene chain. The introduction of functional groups on the aromatic rings leads to significant changes in the solubility (silylated polymers), T g , and electronic properties of the material, showing how the change of substituents in the aromatic rings can lead to polyphosphazenes with properties markedly different from those of the precursor polymer.