| Abstract
| - Thermotropic phase behaviors of undiluted A−B type silicone copolymers, Me3SiO−(Me2SiO)m-2−Me2SiCH2CH2CH2−O−(CH2CH2O)nH (SimC3EOn), have been studied as a function of both poly(dimethylsiloxane) chain length (m) and poly(oxyethylene) chain length (n). Differential scanningcalorimetry, small-angle X-ray scattering, and video enhanced microscopy have been employed to constructphase diagrams and characterize microstructures. Three distinct ordered-state morphologies were observedfor the Si25C3EOn system: micellar cubic (I2), hexagonal (H2) (here, the subscript 2 indicates POE embeddedin PDMS matrix), and lamellar (Lα), within the examined composition range f = 0.06 to 0.50 (f = volumefraction of the polyoxyethylene part). Only H2 and Lα ordered phases were observed in the studied rangef = 0.33−0.80 for the SimC3EO51.6 system. The I2 phase is shown to have Fd3̄m or at least Fd3̄ spacegroup symmetry. The effective cross-sectional area per copolymer molecule at the A−B interface, aP,increases with increasing both m and n, while the morphologies change in the direction from Lα to H2with m and I2 to H2 to Lα with n. The compositional range for the formation of the different microstructuresin the absence of solvent is compared with that observed in the presence of solvents (water or siliconeoil) and also with other copolymer melt systems.
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