1.
Photo-Induced Assembly of
Spiropyran Polymers with Different
Metal Ions
Hillary Straub1,2, Larisa Florea1, Dermot Diamond1
1 Insight Centre for Data Analytics, National Centre for Sensor
Research, School of Chemical Sciences, Dublin City University,
Dublin 9, Ireland
2Department of Chemistry, University of Kansas, Lawrence, USA

2.
Background
Me2+
Spiropyrans are
photochromic molecules
that can be reversibly
switched between the
spiro form (SP) and the
merocyanine form (MC)
using light of appropriate
wavelengths.
1

3.
Background and Applications
2
Thermoresponsive polymers
incorporating spiropyran have
been used in light-induced
aggregation.
Photo-induced conformational
changes have been observed with
spiropyrans functionalized on
polypeptides.
DOI: 10.1039/c3cs60181a

4.
Aggregation of Spiropyran
Polymers with Metal Ions
Me2+
Me2+
Me2+
+
+
+
+
+
+
+
+
+
+
-
-
-
-
--
--
-
-
3

5.
Synthesis of the Monomer
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
250 300 350 400 450 500 550 600 650 700 750
Absorbance(a.u)
Wavelength (nm)
Monomer-UV
Monomer-WL
4

6.
Synthesis of Polymer
n
5

7.
Spiropyran Polymer without Me2+
6

8.
Photo-Induced Me2+ Aggregation
Explore photo-induced aggregation by
varying the given parameters:
 solvent environment
 Me2+ Identity
 The ratio of Me2+ compared to the number of
MC units in the Polymer chain
 The length of the polymer chain
7

9.
75 Length Polymer
Cu2+:MC
Units
Ratio of DMF (1mg/mL) to water
1:1 1:2.3 1:4 1:9
1:2 Prior UV UV
1:4 Prior UV
1:8 UV UV
1:16 UV
1:32
Results: Cu2+ Induced Aggregation
300 Length Polymer
Cu2+:MC
Units
Ratio of DMF (1mg/mL) to water
1:1 1:2.3 1:4 1:9
1:2 Prior UV UV UV
1:4 Prior UV UV
1:8 Prior UV
1:16 UV
1:32 UV
1:64 UV
The longer chain polymer
shows a larger range of results.
Both polymer chain lengths
demonstrate that as the
concentration of polymer
decreases and the amount of
water in the sample increases,
the aggregation is limited or
unseen.
8

10.
The Affect of Water in the Sample Vs.
the Affect of the Polymer Concentration
300 Length Polymer
Cu2+:MC
Units
Ratio of DMF to water
(amount of Polymer in 1 mL Sample)
1:1 (.5mg) 1:9 (.5mg) 1:9 (.1mg)
1:2 Prior Prior UV
1:4 Prior Prior
1:8 Prior Prior
1:16 UV UV
1:32 UV UV
1:64 UV
Although water has a
slight affect on the
aggregation of the
samples, the
concentration of the
polymer in the sample
is shown to be a more
important factor in the
aggregation of samples
in ratios of DMF and
water.
9

11.
UV-Vis Data
-0.025
0.025
0.075
0.125
0.175
300 350 400 450 500 550 600 650 700 750 800
Absorbance(a.u.)
Wavelength (nm)
Polymer+White Light
Polymer+UV
Polymer+Cu-preUV
Polymer+Cu-postUV
13

12.
Results: Testing Different Metal Ions
75 Length Polymer
1:1 DMF:water
(.5mg PMR in
1mL Sample)
Me2+:MC
units
Cu2+
Co2+
Ni2+
Zn2+
Ca2+
1:2 Prior UV UV UV
1:4 Prior UV
1:8 UV UV
1:16 UV
1:32
300 Length Polymer
1:1 DMF:water
(.5mg PMR in
1mL Sample)
Me2+ : MC
units
Cu2+
Co2+
Ni2+
Zn2+
Ca2+
1:2 Prior UV UV UV Prior
1:4 Prior UV UV
1:8 Prior UV UV
1:16 UV
1:32 UV
1:64 UV
**Copper was the only
metal ion to cause photo-
induced aggregation in
samples with an
increasing amount of
water and decreasing
concentration of polymer.
**Nickel and Zinc
samples also showed
aggregation in the
ratio 1:2.3 of DMF :
water, but not in
samples with lower
concentration of
polymer. Red
indicates ratios that
have yet to be tested.
10

13.
De-aggregation
Me2+
Me2+, UV
- Me2+, White light
• De-aggregation could not be achieved by photo-irradiation
• Irradiation with white light caused the aggregates to turn from
purple to white
• Similar results were obtained with all of the metal ions studied
11

14.
SEM Images
Left: 1:1 DMF: Water with 1:4 Cu2+:MC units; Top Right: 1:1 DMF: Water with 1:2 Zn2+:MC units;
Bottom Right: 1:1 DMF: Water with 1:2 Ni2+:MC units.
SEM images of aggregates acquired 30 July 2014
12

15.
Conclusions
 The length of the polymer chain facilitates in the
aggregation of the samples
 A higher ratio of organic solvent compared with water
showed a larger range of results, caused by the higher
amounts of polymer in the samples.
 Lower ratios of metal ion: MC units cause aggregation;
The samples with higher amounts of polymer in the
samples and the samples with the metal ions with higher
binding affinities showed successful aggregation with
lower ratios of metal ions: MC units
 Successful aggregation was seen in the metal ions with
less binding affinity
14

16.
Acknowledgements
Science Foundation Ireland under the
Insight initiative, grant SFI/12/RC/2289
 Hamilton Undergraduate Research
Scholarship 2014.
University of Kansas
15