0000000000231146
AUTHOR
Axel Hinrichs
Blends of PDMS and random copolymers of dimethylsiloxane and methylphenylsiloxane: Phase separation in the quiescent state and under shear
The miscibility of random copolymers (COP), consisting of dimethylsiloxane and methylphenylsiloxane units, with poly(dimethylsiloxane)s (PDMS) was studied in the absence and in the presence of shear experimentally as well as theoretically. Blends of COP 0.86 28 with PDMS 33 (subscripts: volume fraction of DMS in the copolymer, numbers after the abbreviations: weight average molar masses in kg/mol) were investigated far from critical conditions on the PDMS side of the phase diagram. According to these experiments the two phase regime increases by shear without exception and the maximum effects grow from 3 to 12 K as the PDMS concentration increases. Theoretical calculations were performed un…
Influence of Molar Mass Distribution on the Compatibility of Polymers
Abstract Phase equilibria were calculated by means of a new method (direct minimization of the Gibbs energy of mixing) for polymer blends consisting of monodisperse polymer A and polydisperse polymer B. The results obtained for a Schulz-Flory distribution of B (molecular nonuniformity U = (M w/M n) −1 = 1 and 100 components of model B) agree quantitatively with that of computations on the basis of continuous thermodynamics. The influence of U B on the miscibility of A and B in 1:1 mixtures was studied for constant M w of B, quantifying the incompatibility of the polymers by the length of the tie lines. The outcome of these calculations demonstrates that the typical effect of an augmentation…
Shear induced mixing/demixing: blends of homopolymers, of homopolymers plus copolymers, and blends in solution
Shear may shift the phase boundary towards the homogeneous state (shear induced mixing, SIM), or in the opposite direction (shear induced demixing, SID). SIM is the typical behavior of mixtures of components of low molar mass and polymer solutions, SID can be observed with solutions of high molar mass polymers and polymer blends at higher shear rates. The typical sequence with increasing shear rate is SIM, then occurrence of an isolated additional immiscible area (SLD), melting of this island into the main miscibility gap, and finally SIM again. A three phase line originates and ends in two critical end points. Raising pressure increases the shear effects. For copolymer containing systems S…