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Nonlinear Optical Response of Hybrid Block Copolymer Micelles
Encapsulating Metal Nanoparticles
Meristoudi A. 1 , Pispas S. 1 , Vainos N. 1,2 , Iliopoulos K. 3,4 , Couris S. 3,4
1 Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation,
48Vass. Constantinou Ave., Athens 11635, Greece
2 University of Patras, Materials science Department, Patras 26504, Greece
3 Institute of Chemical Engineering and High Temperature Chemical Processes, Foundation for Research and Technology-
Hellas, P.O. Box 1414, Patras 26504, Greece
4 University of Patras, Department of Physics, Patras 26504, Greece
*amerist@eie.gr
Research on metallic nanoparticles incorporated into polymer matrixes has attracted immense attention since these materials
exhibit in general fascinating properties, and in particular large third-order nonlinear optical properties [1]. The synthesis and
spectroscopic characterisation of such materials is reported in this work.
The preparation of the block copolymer based hybrid organic-inorganic materials occurs in solution, using a
selective solvent for one of the polymer’s blocks causing the formation of micelles, which are then loaded by the addition of
various amounts of salt precursors containing the metal cations. The salts are preferentially dissolved into the micelles’ core
due to the polar environment. Addition of a reducing agent, such as hydrazine, causes the reduction of the cations to metal
nanoparticles [2]. The nonlinear optical response of both bulk solutions and thin films of composite materials obtained by
spin coating is investigated here.
Poly(isoprene-b-acrylic acid) block copolymers (PI-PAA) were synthesized by anionic polymerization and post
polymerization hydrolysis. The particular block copolymers form micelles in THF with poly(acrylic acid) cores and
poly(isoprene) coronas, which can be used as nanoreactors for the templated synthesis of Ag and Au nanoparticles from salt
precursors, via chemical reduction. Poly(styrene-b-2-vynilpyridine) block copolymers (PS-P2VP) were also synthsized by
anionic polymerization through sequential addition of monomers. In this case, no post-polymerization functionalization was
performed since the pyridine groups of the P2VP block can interact directly with metal precursors, especially with HAuCl 4 ,
due to the coordination ability of the nitrogen in the pyridine ring.
Micellization
Nanosized
micelles
+ 5+
Metal loading (Ag , Au )
Reduction
Metal loaded
micelles
Nanoparticle
loaded micelles
Evaporation
of solvent
Nanostructured hybrid films
: coordinating block : Metal ions
: “sensing” block
: Metal nanoparticles
Scheme 1. Synthetic protocol for in situ preparation of Ag and Au nanoparticles in block
copolymer solutions in selective solvents
The micellization and metal loading of the block copolymers was monitored by dynamic light scattering (DLS) [3,
4] and IR spectroscopy. Further spectroscopic characterization was performed by UV-vis spectroscopy, transmission electron
microscopy (TEM) and scanning electron microscopy (SEM).
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