Nucleophilic cosubstitution of poly(dichlorophosphazene) with alkyl ether and amino acid ester

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2005-06, Vol.43 (11), p.2417-2425
• Main Authors: Zhang, Teng, Cai, Qing, Wu, Zhan Peng, Li, Cheng Qiang, Jin, Ri Guang
• Format: Article
• Language: English
• Subjects: alkyl ether; amino acid ester; Applied sciences; biodegradable; biomaterials; Chemical modifications; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers; polyphosphazenes
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.20722

The nucleophilic substitution reaction of poly(dichlorophosphazene) with sodium 2‐methoxyethoxide and glycine ethyl ester has been studied in detail. Polymers prepared with different methods have been characterized by 1H NMR, and the results reveal that the addition sequence of the two nucleophilic reagents is an important factor in determining the structure of the resultant polymer. If alkyl ether is added first, the subsequently introduced amino acid ester not only reacts with residual PCl but also attacks the alkyl ether side units present by replacing either the whole group or just OCH3. As a result, a new kind of side group (OCH2CH2NHCH2COOC2H5) can be detected in the macromolecule. To obtain polymers with desired compositions {poly[(methoxyethoxy)x(ethylglycino)yphosphazene]}, the amino acid ester should be introduced initially to react with poly(dichlorophosphazene), and it should be followed by the alkyl ether. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2417–2425, 2005 In the synthesis of poly(organophosphazene)s with methoxyethoxy and glycine ethyl ester units as side groups, the structure of the resultant polymer depends significantly on the addition sequence of the two nucleophiles. If sodium 2‐methoxyethoxide is added first and is followed by glycine ethyl ester, glycine ethyl ester destroys the structure of the methoxyethoxy units and even displaces all the methoxyethoxy units to form structure I. However, no such side reaction can take place if the two nucleophiles are added in the opposite sequence to obtain poly[(methoxyethoxy)x (ethylglycino)yphosphazene] with the desired compositions (structure II.).