Compatibilization of PS and PDMS in chloroform is achieved by
addition of a small amount of a star polymer containing a g-CD-core
and PS arms. Compatibilization is visually observed when turbid, asprepared
solutions become clear upon heating or extended stirring
at room temperature. At a solids concentration of 10 g/dl, these
solutions remain clear over several months. The mechanism of
compatibilization involves threading of the CD-core by PDMS and
solubilization of the resulting ‘‘slip-ring graft copolymer’’ via the PS
star arms. This process breaks up the undissolved PDMS domains
into smaller, more stable micelles. Evidence for threading of the CDcore
by PDMS is found using ROESY 2D-NMR. Compatibilization
requires a solvent which is good for PS and poor for PDMS.
Characterization of the compatibilized solutions by dilute
solution viscosity and DLS shows that they behave similarly to graft
copolymers in selective solvents which are known to form micelles.
As with graft copolymers, micelle formation in the CD-star solutions
is accompanied by a reduction in intrinsic viscosity. The size of
the micelles is not affected by CD-star content or PDMS molecular
weight within the ranges studied here. DLS measurements show
that dilution of the solutions from 10 to 1 g/dl induces de-threading
and agglomeration of PDMS, suggesting that the critical micelle
concentration for this system lies between 1 and 10 g/dl.