Facile Manufacture and Storage of Poly(methylhydrogenosiloxane)s

• Published in: International journal of biological macromolecules 2005-03, Vol.38 (6), p.2230-2236
• Main Authors: Yactine, Bassem, Ganachaud, François, Senhaji, Omar, Boutevin, Bernard
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical Sciences; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers; Polymers; Preparation
• ISSN: 0024-9297; 0141-8130; 1520-5835
• DOI: 10.1021/ma047912w

This paper describes the ring-opening polymerization of 2,4,6,8-tetramethylcyclotetrasiloxane (D4 H) in miniemulsion, using mono- and diphosphonic acid surfactants. In the simplest formulation conditions, polymerization proceeds in less than 15 min to generate linear poly(methylhydrogenosiloxane) (PMHS) of large molar masses (typical number-average of 25 kg/mol), of low polydispersities (around 2), and in good yields (up to 94%). Molar masses can be tuned at will since for similar conversions but increasing times, varies between 10 and 30 kg/mol. After 4 h reaction, some redistribution reactions start to proceed, responsible for PMHS chains switching into macrocycles. It was shown that rising the pH to stop the polymerization and breaking the emulsion with excess of alun salt induced hydrolysis/condensation reactions, which rapidly convert the polymer chains into an unwished macrogel. Rather, extracting the polymer by simple centrifugation and using the diacid surfactant induce a physical gelling that very efficiently suppresses side reactions, as shown by minor evolution of the molar mass distribution for 10 months.