STEREOCOMPLEX FORMATION IN BLENDS OF BLOCK-COPOLYMERS OF SYNDIOTACTICPOLY(METHYL METHACRYLATE) (PMMA)-POLY(DIMETHYLSILOXANE) (PDMS) AND ISOTACTIC PMMA - DIFFERENTIAL SCANNING CALORIMETRY (DSC) AND DYNAMIC-MECHANICAL THERMAL-ANALYSIS (DMTA)
H. Deuring et al., STEREOCOMPLEX FORMATION IN BLENDS OF BLOCK-COPOLYMERS OF SYNDIOTACTICPOLY(METHYL METHACRYLATE) (PMMA)-POLY(DIMETHYLSILOXANE) (PDMS) AND ISOTACTIC PMMA - DIFFERENTIAL SCANNING CALORIMETRY (DSC) AND DYNAMIC-MECHANICAL THERMAL-ANALYSIS (DMTA), Macromolecules, 28(6), 1995, pp. 1952-1958
PMMA stereocomplex formation was demonstrated in domains of PMMA-PDMS-
PMMA block copolymers having syndiotactic (S) PMMA blocks by mixing a
THF solution of the block copolymer and that of isotactic (I) PMMA in
the S/I PMMA ratio of 2 followed by precipitation fi om THF or by form
ing the same blend by precipitation from chloroform followed by anneal
ing at temperatures in the 100-140 degrees C range. The various blends
and the block copolymer itself were analyzed by DSC and DMTA. The dis
sociation-melting temperature of the stereocomplexes present in the PM
MA domains was shown to increase with increasing annealing temperature
. The rate of formation of stereocomplexes in bulk was found to be muc
h slower than that in blends of PMMA homopolymers. Crystallization of
PDMS was shown to be hindered by stereocomplex formation. The modulus
at temperatures above 100 degrees C of the blends in which stereocompl
ex formation occurred was found to be higher than in the same blends i
n which such a stereocomplex was absent. These results are interpreted
by the formation of networks formed by fringed micellar crystallites
of PMMA stereocomplexes acting as physical cross-links.