  'Soft' patchy surfactant micelles have become an additional building tool in
self-assembling systems. The triblock copolymer, Pluronic F108, forms spherical
micelles in aqueous solutions upon heating leading to a simple phase diagram
with a micellar crystalline solid at higher temperatures and concentrations.
Here we report the strong influence of end-functionalising the chain ends
either with an azide or azide-DNA complex on the systems' phase behaviour. We
find that the azide(N3)- functionalisation renders the chain ends weakly
hydrophobic at lower temperatures, causing them to self-assemble into
flower-micelles. This hydrophobicity increases with increasing temperature and
poses a competing self-assembling mechanism to the solvent induces hydrophobic
interactions between the middle-blocks of F108 at higher temperatures and leads
to a macroscopic phase separation that is absent in the pure F108 system.
However, when we attached short, hydrophilic single-stranded (ss)DNA to the
azide groups via click chemistry the chain ends became 'sticky' due to DNA
hybridisation below the melting temperature of the complementary ssDNA ends
while reverting to hydrophilic behaviour above. We characterise their
structural and rheological properties via Dynamic Light Scattering (DLS) and
DLS-based passive microrheology with an improved time-frequency domain
inversion step. We present the structural behaviour of dilute and semi-dilute
solutions of the original F108 system and compare the results with solutions
containing either the F108- azide (F108-N3) or partially DNA-functionalised
F108-azide chains. Our DLS and microrheology studies inform us on how the
attachment of azide groups on F108 changes the mechanical and structural
properties of micellar fluids pioneering further characterisation and design of
these hybrid systems.
