Amphiphilic polysiloxane block copolymer

Another possibility for azo-polysiloxane applications is to obtain photo-sensible micelles [15-18]. The interest for this application is explained by the possibility to use polymeric micellar aggregates for controlled release of substances such as drugs [19, 20]. There are few reports on the use of light as an external stimulus for small amphiphilic molecules by incorporahug the azobeuzeue chromophore iuto surfactant [16] or for light-responsive micellar aggregates formed by amphiphilic block copolymers [17,18]. 

Although polysiloxanes have superior properties compared to common organic polymers, the controlled formation of amphiphilic block copolymers consisting of a pure polysiloxane backbone remains essentially unexplored. There have been only a few reports of such polymers in the literature, for example one bearing pendant carboxyl groups on the polysiloxane chain,and another prepared by a one-pot sequential anionic ring-opening polymerization of two cyclotrisiloxanes. ... 

Polysiloxane-containing amphiphilic block copolymers have been prepared by different approaches. Coupling of an end-functionalized polydimethylsiloxane with a functionalized poly(ethylene oxide) led to the formation of PDMS- -PEO diblock copolymers. The sequential anionic ring-opening polymerization of tetramethyltetravinylcyclotetrasiloxane and hexamethylcyclotetrasiloxane resulted in the formation of a vinyl-substituted diblock copolymer, the vinyl groups of which could be modified by further reactions so as to import amphiphilic character. The phase behavior of short-chain PDMS-Z -PEO diblock copolymers revealed the preferred formation of lamellar phases by this type of amphiphile... 

Amphiphilic block copolymers that are soluble in CO2 comprise a C02-philic block and a CO2-phobic one and are thus prone to form complex structures in solution such as micelle-like aggregates and polymersomes. As a result of their high solubility, fluorinated poly(acrylates) and polysiloxanes mainly constitute the C02-philic building blocks of choice to design C02-soluble amphiphilic copolymers. 

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