Biomedical Engineering Reference
In-Depth Information
Fig. 4
Jorzik et al. copolymer structures [35]
copolymers exhibited a better efficiency than the triblock copolymers. In the
same paper [35], A/B/A-C and A/B/C-D systems were also studied. Two kinds
of diblock copolymers were investigated: P(EO-b-S) and P(S-b-MMA), the
polystyrene copolymer segments were located at the interface with the PDMS
and PMMA copolymer segments at the PEO interface. They were found to be
much less efficient than the PDMS-b-PEO copolymers.
3.2
In-Situ Copolymer Formation
In-situ copolymer formation has several advantages over the added copoly-
mer approach. First, the preformed copolymers need to be dispersed during
the blend mixing so that the dispersion efficiency ultimately depends on
the blending technique. Next, there is the risk that the preformed copoly-
mers micellize so that part of the added copolymer is no longer involved
in the compatibilization process. On the other hand, since in-situ synthe-
sized copolymers are already at the interface when they are formed, they
are less inclined to form micelles and hence diffusion issues are avoided. An
added advantage is the fact that in-situ-formed copolymers involve a one-step
process. The main drawback of in-situ compatibilization is that it requires
very reactive groups to be compatible with the residence time of common
industrial processes. Although many reactive groups can be involved, anhy-
dride/amine is up to now the best pair for in-situ copolymer formation since
in addition to compatibilization [38, 39], it allows the preparation of nanos-
tructured materials [40-46].
