4th EucheMs chemistry congress

tuesday, 28-Aug 2012
s790
chem. Listy 106, s587–s1425 (2012)
organic Chemistry, Polymers – ii
Polymer chemistry – iii
o - 2 2 8
SurfACe funCtionALized PoLyPhenyLene
dendriMerS
r. StAnGenBerG 1 , K. MüLLen 1
1 Max-Planck-Institute for Polymer Research, Synthetic
Chemistry, Mainz, Germany
Modifying the periphery of dendrimers affects properties
such as solubility, aggregation and membrane penetration. A new
type of amphiphilicity on the periphery of polyphenylene
dendrimers (PPDs) is investigated by designing the periphery in
an unprecedented way and scale. Polar (sulfonic acids) and
non-polar groups (alkyl chains) were placed alternating close to
each other on a sub-nanometer length scale (7?) to create small
hydrophilic and hydrophobic domains on the surface.
While in case of amphiphilic nanoparticles the surface
patterning relies on self-assembly, dendrimer synthesis allows the
right placement of different functional groups at assigned
positions. Thus the number and arrangement of functional groups
as well as the distance between them can be adjusted. Backward
folding of the periphery into the dendrimer interior is prevented
by the rigid PPD scaffold so that functional groups of different
polarity are fixed on the surface. Polarity differences lead to a
permanent repulsion between the different functional groups.
These functional groups cannot rearrange into a fully phase
segregated state due to their fixed positions. This frustration leads
to unique solubility i.e in polar and non-polar solvents as well. An
application of such an amphiphilic PPDs as a transport agent for
phase transfer (i.e. drug delivery via membranes) is presently
being investigated.
On the other hand two polyphenylenedendrons of different
polarity can be combined to a so called “JANUS”-dendrimer.
Such type of a PPD containing a hydrophilic and a lipophilic
hemisphere should form supramolecular structures due to their
strong aggregation.
Furthermore, the switchability of the surface polarity and
thereby the solubility is enabled by the incorporation of
photoswitchable azobenzenes in the scaffold of our PPDs is under
investigation. We aim to be able to switch the solubility in polar
solvents on and off by light.
Keywords: Dendrimers; Amphiphiles;
Polymer chemistry – iii
4 th EucheMs chemistry congress
o - 2 2 9
new Low enerGy GAP PoLyMerS for
APPLiCAtion in SoLAr CeLLS
A. irAqi 1 , h. yi 1 , A. ALGhAMdi 1 ,
M. S. SArJAdi SArJAdi 1 , S. AL-fAifi 1 , d. wAtterS 2 ,
J. KinGSLey 2 , d. G. Lidzey 2
1 University of Sheffield, Chemistry, Sheffield, United Kingdom
2 University of Sheffield, Physics & Astronomy, Sheffield, United
Kingdom
Research into the use of conjugated polymers for application
in bulk heterojunction solar cells has been the subject of much
interest in recent years in view of their potential technological
value for energy generation. Major advances have been achieved
in this area; however, new polymer systems with high absorption
coefficients and extended absorption spectra are still being sought
for use in this area.
The design of low energy-gap conjugated polymers can be
achieved by introduction of alternate electron donor and acceptor
repeat units along the polymer chains which results in
intra-molecular charge transfer. This approach proved successful
in the preparation of a range of narrow energy gap polymers for
application in bulk heterojunction solar cells. Donor/acceptor
systems comprising copolymers with alternating 2,7-carbazole
repeat units along with acceptor repeat units have been described
by Leclerc et al. and showed great promise when used with PCBM
in bulk heterojunction photovoltaic cells with good power
conversion efficiencies. We have reported recently the preparation
of a series of donor / acceptor alternating copolymers comprising
dithienyl benzothiadiazole with alkoxy substituents and 2,7-linked
carbazole repeat units. The polymers showed higher open circuit
voltage (V ) values than that of PCdtBt and good power
oc
conversion efficiencies with PCE values of 4.22 and 4.12%.
In this work, we report the preparation and
characterization of new classes of low energy gap
donor/acceptor alternating copolymers, comprising 2,7-linked
carbazole repeat units and alternate repeat units
including selenophenyl benzo[1,2,5]thiadiazole units and
thienothiophenyl benzo[1,2,5]thiadiazole units. We also present
studies on the physical properties of the polymers and their ability
to act as electron donors to PCBM as well as their performance
in bulk heterojunction solar cells in blends with PCBM.
Keywords: Conjugated polymers; Organic photovoltaics; Bulk
heterojunction solar cells;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc