PERSONAL DE APOYO
YAÑEZ Maria Julia
congresos y reuniones científicas
Título:
PEO-b-PE elongated micelles dispersed in a visible-light photopolymerized epoxy matrix
Autor/es:
ZUCCHI, ILEANA; YAÑEZ MARIA JULIA; SCHROEDER, WALTER
Lugar:
Barcelona
Reunión:
Simposio; Third International Symposium ? Frontiers in Polymer Science; 2013; 2013
Institución organizadora:
ELSEVIER
Resumen:
Self-assembly
of
amphiphilic molecules provides a fundamental mechanism for building
complex
soft materials. This report describes the preparation of thermoset
materials
containing self-assembled nanostructures of a low-molecular-weight
poly(ethylene oxide)-poly(ethylene) (PEO-b-PE)
diblock copolymer dispersed in a epoxy matrix. The preparation of these
nanostructured materials involves firstly the dissolution of
the block copolymer in an epoxy monomer of the type diglycidyl ether of
bisphenol A (DGEBA) at 150ºC for 5 min. The mixture
was then allowed to cool to room temperature and exposed to
visible-light in
order to polymerize the DGEBA monomer via a cationic photopolymerization
mechanism. DGEBA monomer undergoes slow photoinitiated polymerization
allowing
during this term the growth of block copolymer micelles. After the DGEBA
cured,
samples looked cloudy with the opacity increasing with the block
copolymer
content. Transmission electron microscopy (TEM) analysis of samples
containing
up to 20 wt% PEO-b-PE showed elongated micelles dispersed in the epoxy
matrix
without any macroscopic phase separation evidence. These micelles were
typically on the order of 20 to 30 nm in width with variable lengths,
comprised
between 1 and greater than 10 microns, depending on block copolymer
concentration. Figure 1a shows a TEM image of the sample modified with
10 wt% PEO-b-PE, whereas Figure 1b shows the same sample
stained with RuO4. In this last image, PEO appears black, epoxy
gray, and PE white. A micelle structure consisting in a semicrystalline
PE core
surrounded by a PEO shell is revealed. We were able to explore the
growth mechanism of these
micelles by following the evolution of the DRX (X-Ray Diffraction)
pattern
corresponding to semicrystalline PE moiety. Additional Small angle X-ray
scattering (SAXS) experiments are currently under study in order to
understand the formation mechanism and structural features of this
intriguing
system.