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Summary: The synthesis of novel methacrylic phosphonated surface‐active monomer by an original method is described. The crucial stage is the telomerization of undec‐10‐enyl acetate with dialkyl (alkyl = methyl or ethyl) hydrogenphosphonate. The phosphonated acetate obtained is selectively hydrolysed to give dialkyl(11‐hydroxyundecyl)phosphonate as a precursor. The alcohol function allows setting of methacrylic side, which is highly reactive in radical polymerization. Particularly, by mono‐dealkylation of dimethyl phosphonate in a selective and quantitative way, the potassium iodide permits to get, at one stage, the expected salt of sodium methyl phosphonate. The new surface‐active sodium methyl(11‐methacryloyloxyundecyl)phosphonate is characterized by 1H and 31P NMR. Its critical micelle concentration evaluated by conductometry is 2.4 × 10−2 mol · l−1.Synthesis of dialkyl(11‐methacryloyloxyundecyl)phosphonate (DAHP) without protection of alcohol function.imageSynthesis of dialkyl(11‐methacryloyloxyundecyl)phosphonate (DAHP) without protection of alcohol function.

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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.