The main
research activities of the group are related to the self-assembly
of block copolymers.
Block copolymers are
macromolecular structures in which at least two chemically
different polymer blocks are linked together.
Living and controlled sequential copolymerisation
techniques allow
the preparation of such structures and the control of their
molecular parameters (narrow polydispersity indexes for the blocks,
control of the chain end-groups…). The
topology (or
architecture) of the block copolymer can also be controlled
(linear, star-like, grafted block copolymers…) as well as
the number of blocks (AB, ABA, ABC, ABCD block
copolymers…).
Because polymer blocks are in most cases immiscible, a
microphase separation is observed
leading to polymeric materials organized at the nanometer scale.
This is illustrated below for a bulk AB block copolymer in which
the minor microphase forms spheres dispersed in a matrix formed by
the major block. The different spheres are further arranged into a
cubic lattice.
Roughly, the
shape and 3D arrangement of the nanosized domains depend on the
volume fraction of each block while their size is related to the
length of the blocks. The
self-assembly of the polymer
blocks in these different structures is generally driven by
hydrophobic interactions although other interactions (ionic,
hydrogen bonding, metal-ligand) can play an important role in
specific cases.
Whenever the bulk structure is dissolved in a selective solvent for
the major block,
block copolymer micelles are observed
that consist of a
core formed by the
insoluble blocks surrounded by a
corona formed by the
soluble blocks. Because these objects have a typical size of a few
nanometers, they are widely used in
nanotechnology.