a) b - École Polytechnique de Montréal

“compatibilization” was suggested by Gaylord in the 1960s for the method used to decrease the
interfacial tension between polymer pairs and the blend shows more stable morphology(N. G.
Gaylord, 1969; N. G. Gaylord, ,Vol.142,P.76,(ACS,Washington,1975). 1975).
Compatibility between phases is enhanced using a block copolymer with particular physically or
chemically compatible segments with each of the blend components. Block copolymers are
designed for binding two components together. They stay at the interface and either part of their
molecular chain has physical or chemical interaction with each component of the blend. The
main effect of addition of an interfacial agent on the morphology of an immiscible blend is to
reduce the particle size and to narrow the particle-size distribution(Hoganand & Banks, 1958;
Matos, Favis, & Lomellini, 1995; Sarazin & Favis, 2003) (Figure 2-2).
a) b) c)
d) e) f)
Figure 2-2. Action of the diblock copolymer to reduce the pore size for 50/50 PLLA/PS
blends at copolymer concentrations of (a) 2.5%, (b) 5%, (c) 8%, (d) 12%, (e) 15%, and (f) 20%.
Copolymer concentration shown is based on the weight of polystyrene. The white bar indicates 1
micron(Sarazin & Favis, 2003).
Both reduction of coalescence and decrease in interfacial tension results in reduction of particle
size after interfacial modification. Sundararaj et al.(Sundararaj & Macosko, 1995) showed
suppression of coalescence happens when two droplets with a layer of diblock or graft
copolymer at the interface are less likely to coalesce due to formation of a shell of copolymer
molecule around droplets.
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