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measurements. The authors measured the changes in the interfacial tension between
PDMS and PBD during the reaction between amino-terminated PDMS and car-
boxyl-terminated PBD, which can react at the interface and form diblock copoly-
mers that compatibilize the blend. The concentration of the reaction product was
inferred from an application of Gibbs adsorption equation, justified for an insignifi-
cant degree of conversion of reactants in either phase. The obtained time-dependent
copolymer concentration was found to follow a single-exponential growth function
at low copolymer coverage, indicating first order kinetics.
Favis and coworkers [
51
,
52
] critically examined the relationship between the
interfacial tension reduction in the presence of diblock copolymer additives and
the dispersed phase morphology evolution as a function of the concentration of the
interfacial modifier. Blends of PS/PE in the presence of PS-
b
-hydrogenated poly-
butadiene-
b
-PS (Kraton, SEBS) [
51
] and of PE/PVC in the presence of PI-
b
-poly
(4-vinyl pyridine) or PS-
b
-poly(acrylic acid) [
52
] were investigated. The authors
unambiguously confirmed directly the relationship between interfacial tension and
phase size, as predicted by the Taylor theory [
280
].
4.3 Theories of the Interfacial Behavior in Homopolymer/
Homopolymer/Copolymer Blends
Statistical thermodynamic theories have been formulated to understand and predict
the emulsifying behavior of block copolymers at the polymer polymer interface
[
70 75
,
77 80
,
95
,
98
,
99
,
105
,
267
,
279
,
281
,
282
]. Noolandi and Hong [
70
,
71
,
281
] utilized their theory of inhomogeneous systems in order to investigate the
segment density profiles at the interface for the system homopolymer A/homopol-
ymer B/diblock copolymer AB/common solvent. They investigated the effect of the
molecular weight and the concentration of the diblock on the interfacial tension,
under the assumption that the copolymer is either localized at the interface or is
randomly distributed in the bulk homopolymer phases, i.e., for concentrations
below the CMC. Shull and Kramer [
77
] developed and applied the Noolandi
Hong theory for the case without solvent and also discussed the possibility of
micelle formation in view of their earlier experimental observations [
38
,
102
].
Semenov [
103
] developed an analytical mean-field theory for the equilibrium of
block copolymers in a homopolymer layer between an interface with another
homopolymer and the free surface, and the results were compared to the data of
Shull et al. [
38
]. Semenov also analyzed the situation for concentrations above
CMC and found that micelles are attracted to both the free surface and (more
weakly) to the polymer polymer interface, but he did not investigate the interfacial
tension reduction due to copolymer segregation to the polymer polymer interface.
The effects of copolymer architecture on the interfacial efficiency of the com-
patibilizers have been investigated in a series of papers by Balazs and coworkers
[
80
,
85
] using a combination of SCMF calculations, analytical theory, and Monte
Carlo simulations as well as by Dadmun [
95
,
98
] using computer simulations.
