The name is absent

the molecular dimensions, that is, around 50 to 1000 À [49]. A variety of lamellar
micro-domains with different motifs, chemistries, sizes and periodicity can be created
by tuning in the molecular parameters (molecular weight, species, film thickness and
external potentials). All the aforementioned applications of the diblock copolymers
harness this spontaneous self-assembly. Furthermore, these applications will be facili-
tated by the recent developments in block copolymer synthesis, such as atom transfer
radical polymerization [128], to widen the spectrum of available copolymer materials
or decrease their cost of manufacture.

Experimental studies on confined thin films of symmetric diblock copolymers [129,
130, 131, 132, 133, 134] have provided many insights into the general features of the
lamellar morphologies. However, the detailed results are, of course, confined to the
specific systems that were examined. Furthermore, few of the experimentally observed
lamellar morphologies are found to be kinetically favored rather than the thermody-
namically stable one [135]. Hence, the concurrent development of the theoretical
models to determine the detailed microstructure of these inhomogeneous polymer
systems is important. Shull [136] developed a unified mean field theory applicable
to bulk diblock copolymer melts, melts near a single surface and confined thin films.
The theory is applicable in both weak segregation and strong segregation limits (WSL
and SSL). Turner [137] considered symmetric diblock copolymer-thin films confined
between two parallel flat surfaces, such that both the surfaces have preferential affin-
ity towards one of the blocks. The free energy calculations in the SSL showed that

113

<<   122   123   124   125   126   127   128   >>

More intriguing information