production of selected secondary metabolites in transformed ...

LIVING RADICAL POLYMERIZATIONS INITIATED WITH
SILSESQUIOXANES
Author: Ing. Ondřej Smrtka – 3 rd year of DSP
Supervisor: Prof. RNDr. Josef Jančář, CSc.
Brno University of Technology, Faculty of Chemistry, Institute of Material Chemistry
Purkyňova 118, 612 00 Brno, Czech Republic; email: smrtka@fch.vutbr.cz
INTRODUCTION
It has been discovered that small variations in molecular structure at the nano-meter scale
level allow substantial changes in macroscopic behavior of nanostructured systems.
Nanocomposites with polymeric matrix belong among the most intensively investigated
materials since they promise extensive industrial and biomedical applications.
The polyhedral oligomeric silsesquixanes (POSS) can be included into the large group of
nano-particles used for nanocomposite preparation. POSS, due to their well-defined structure,
are considered to simulate the surface of silica nano-particles as the smallest possible silica
particle. Nanocomposites containing POSS nanoparticles are considered extremely interesting
class of nanostructure organic-inorganic materials.
Polyhedral oligomeric silsesquioxans are compounds of general formula (RSiO1.5)x, where
x is an even number higher than 4, mostly being 8. R is any of large number of organic
groups, or e.g. hydrogen or halogen atom.
R
R
O
Si
O
R
Si
O
O
Si
O
R
Si
O
Fig. 1: Polyhedral oligomeric silsesquioxan (POSS)
POSS are prepared preferentially by hydrolytic condensation of trifunctional silanes [1].
Organic groups are carried into the molecule either directly during the synthesis (as the fourth
non-reactive group of the silane precursor), or by a transformation of existing groups [2].
Monofunctional POSS are synthesized from incompletely condensed molecules of
silsesquioxane by condensation of another silane with appropriate functional group [3].
POSS particles can be incorporated to the polymeric materials directly by blending with
polymer as the additive, or as the component of polymeric chain. The POSS containing
macromolecules can be synthesized using monomers with POSS pendant groups, or
afterwards, by grafting to the polymer using various condensation or addition reactions (e.g.
hydrosilylation). Another way how to connect POSS with the polymer chain is to use it as the
initiator for ATRP.
ATRP (Atom Transfer Radical Polymerization) has been developed in 1995 by
Matyjaszewski [4]. It is based on rapid attainment of dynamic equilibrium between low
amount of growing free radicals and much higher amount of dormant species. Because the
Sborník soutěže Studentské tvůrčí činnosti Student 2006 a doktorské soutěže O cenu děkana 2005 a 2006
Sekce DSP 2006, strana 228
O
Si
O
O
Si
R
R
O
O
Si
Si
O
R
R