Multisegmented degradable polymers were successfully synthesized via atom transfer radical cross-coupling of α,ω-dihalogenated polymers prepared by atom transfer radical polymerization with dinitroxides. High
molecular weight polymers (M
n
> 100 000 g mol-1) with more than 10 cleavable units in the main chain were
prepared. These multisegmented polymers were chemically and thermally degraded. Chemical degradation, via
basic hydrolysis or disulfide reduction, as well as thermal degradation, by heating in the presence or in the absence
of free nitroxides, led to low molecular weight polymers with relatively low polydispersity (2100 g mol-1 ≤ M
n
≤ 15 100 g mol-1; 1.08 ≤ M
w/M
n ≤ 1.46).
Tetraethylisoindolin-2-yloxyl and its water-soluble trimethylammonium and sulfonate derivatives are more resistant to reduction by ascorbate than the corresponding tetramethyl derivatives.
The synthesis of a carboxy-functionalized nitroxide based on the 2,2,5-trimethyl-4-phenyl-3-azahexane-3-oxy (TIPNO) structure and the synthesis of two difunctional alkoxyamines have been achieved.
Because of the presence of the carboxylic acid function, the nitroxide is organo-soluble in its acidic form and
water-soluble in its basic form. Polymerizations of styrene and n-butyl acrylate mediated with the functional
nitroxide exhibited all the expected features of a controlled system. The presence of an active chain end was
demonstrated by reinitiation of a polystyrene block to form a polystyrene-b-poly(n-butyl acrylate) block copolymer.
The ability of the new functional nitroxide to mediate polymerization in homogeneous aqueous solution has also
been demonstrated. The polymerization of sodium styrenesulfonate was successfully achieved at temperatures
below 100 °C and led to well-defined polymers, providing the first example of nitroxide-mediated radical
polymerization (NMP) in homogeneous aqueous solution below the water boiling point.
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