Controlling molecular mobility in polymer matrices: Synchronizing switching speeds of multiple photochromic dyes

Article abstract of DOI:10.1021/ma101051m

We report a method that allows the facile synchronization of multiple photochromic dyes in a rigid polymer lens matrix together with large increases in their switching speeds. This was achieved by simple chromatographic fractionation of dye-poly(dimethyls

Full text of DOI:10.1021/ma101051m

8488 Macromolecules 2010, 43, 8488–8501
DOI: 10.1021/ma101051m
Controlling Molecular Mobility in Polymer Matrices: Synchronizing
Switching Speeds of Multiple Photochromic Dyes
Nino Malic,†,‡ Jonathan A. Campbell,‡,§ Abdelselam S. Ali,†,‡ Mark York,†,‡ Asha D’Souza,†,‡
and Richard A. Evans*,†,‡,#
†CSIRO Materials Science and Engineering, Bag 10, Clayton Victoria 3169 Australia, ‡The Cooperative
Research Centre for Polymers, 8 Redwood Drive, Notting Hill Victoria 3168, Australia, §School of Chemical
Sciences and Engineering, and #Centre of Advance Macromolecular Design, School of Chemical Sciences and
Engineering, The University of New South Wales, Sydney New South Wales 2052, Australia
Received May 12, 2010; Revised Manuscript Received August 19, 2010
ABSTRACT: We report a method that allows the facile synchronization of multiple photochromic dyes in a
rigid polymer lens matrix together with large increases in their switching speeds. This was achieved by simple
chromatographic fractionation of dye-poly(dimethylsiloxane) (PDMS) conjugates to provide tunable
switching speeds with longer PDMS tails providing faster switching speeds and shorter tails providing
slower switching with no effect on the electronic nature of the dyes. This was done for mono end-functional
dye-PDMS conjugates (one dye at one end of the PDMS) and new telechelic dye-PDMS conjugates (one
dye at each end of a PDMS oligomer) using a wide variety of academic and commercially important
spirooxazines and naphthopyrans (chromenes). Telechelic conjugates gave faster fade performance per unit
length of PDMS oligomer (greater atom efficiency) while having superior matrix compatibility. Independent
photochromic switching of different photochromic dye-PDMS conjugates within the same lens matrix was
demonstrated, resulting in the ability to synchronize coloration and decoloration within multidye systems.
The utility of the method was shown by the creation of a neutral colored (gray) lens, produced through the
combination of three different colored dye-PDMS conjugates having similar independent fade speed
kinetics, and showed exceptional fade performance with good hue maintenance compared to the control lens.
Introduction
The mobility of functional molecules in polymer matrices has
found application in the remote determination of glass transition
temperature1 or free volume.2 This is because the molecular
mobility of the functional molecules determines fluorescence or
absorption properties. Photochromic dyes, although not gener-
ally thought of or used as molecular probes, are also sensitive to
their mobility in polymer matrices.
Photochromic dyes are molecules that display a reversible
color change upon exposure to UV light.3-5 Currently, the largest
commercial use of organic photochromic dyes is within the
ophthalmic lens industry.6 Photochromic sun lenses darken with
exposure to solar UV radiation and return to their colorless state
through thermal and photochemical (visible light) processes
when the wearer returns indoors. The most common type of
photochromic dye used in commercial lenses are 2,2-diaryl-2H-
naphtho[1,2-b]pyrans (Figure 1), where cleavage of the C(sp3)-O
bond and an intramolecular rotation to a quasi-planar confor-
mation with extended pi-conjugation results in highly colored
open form isomers (merocyanines).
Figure 1. Mechanics of photochromism of a 1,3,3-trimethylspiro-
[indoline-2,30-[3H] naphtho[2,1-b][1,4]oxazine (top) and 2,2-diaryl-
2H-naphtho[1,2-b]pyran (bottom). Change in structure is accompanied
by a significant intramolecular rotation.
The photochromic lens market is currently worth in excess of
US$1.7 billion annually in trade sales.7 Competition and growing
demand has pushed research efforts into ever improving genera-
tions of photochromic lens products, with focus on properties
such as color, clarity and darkness, coloration and decoloration
speeds, hot temperature performance, and durability (fatigue
resistance). One of the major requirements of a commercial
photochromic lens product is that it has the ability to switch
quickly between a state of having high light transmission (clear
form) in the absence of ultraviolet light to a state having low
transmission (darkening) under solar irradiation, and vice versa.
Current commercial lenses can be said to be adequately fast in their
coloration performance. However, their inability to quickly fade
back to a colorless state remains a major drawback. The perfor-
mance of a photochromic lens product is a result of both the
inherent characteristics of the dyes which it contains as well as the
properties of the lens matrix in which they are incorporated.
*To whom correspondence should be addressed. E-mail: richard.
evans@csiro.au.
pubs.acs.org/Macromolecules
Published on Web 09/22/2010
r 2010 American Chemical Society

Article
Macromolecules, Vol. 43, No. 20, 2010 8489
Scheme 1. Synthesis of Telechelic (A) and Mono End-Functional (B) Photochromic Dye-Poly(Dimethylsiloxane) Conjugatesa
a Control compounds (C).
Despite there being significant ongoing research into the develop-
ment of inherently fast-fading photochromic dyes the overwhelm-
ing influence over fade-speed, however, is matrix rigidity, of which
Tg (glass transition temperature) is a primary defining measure.
The required mechanical properties of a polymeric lens material
being, namely, rigidity and hardness for shatter-proofing and
scratch resistance, result in an unfavorable host environment for
the necessary mechanics of photochromism to occur (Figure 1). A
lack of fluidity and free-volume hinders the intramolecular rotation
associated with the photochromic dye switching between colorless
and colored states, resulting in a significant slowing of switching
performance as the Tg is increased.8,9
We have previously reported on the enhancement of photo-
chromic performance (coloration/decoloration kinetics) in rigid
polymeric matrices through polymer conjugation.10-13 Covalent
attachment of low Tg polymers directly to the dye provides a soft
and mobile local environment for relatively unhindered photo-
chromic switching to occur, with the result being significantly
increased fade-speeds without compromise of the mechanical
properties of the matrix. Of the various polymers we have
tested, poly(dimethylsiloxane) (PDMS) was found to be the most
effective, the mono end-functionalized dye-PDMS conjugates
providing the largest percentage fade-speed enhancement relative
to the corresponding nonconjugated photochromic controls.
Results also showed that the conjugates achieve a steady state
of coloration, and therefore a higher optical density, far sooner
than the controls under the test conditions employed. This
method of conjugation also has the advantage of being synthet-
ically uncomplicated and uses cheap and readily available PDMS
starting materials, therefore presenting with obvious commercial
appeal.
Here we report a method to synchronize the switching speeds
of different dyes within the same matrix. This goal has been a
major scientific and commercial challenge since most current
commercial photochromic lenses use mixtures of several dyes in
order to obtain neutral tints of gray and brown. Traditionally,
large numbers of photochromic dyes are required to be made in
order to find a selection for combination that happen to synchro-
nize in terms of their performance characteristics, such as
coloration and decoloration speeds, optical densities (intensity
of coloration) at their saturation point, and residual baseline
coloration. The result of the incorporation of unsynchronized
dyes within a lens matrix is an unappealing cascade of different
hues during coloration and decoloration. The patent literature
indicates ongoing development efforts into the design and syn-
thesis of novel dyes having optimized properties. Our method14
allows independent alteration of the switching speeds of dyes
(without altering their electronic nature) to readily synchronize
multidye systems. This can now allow the combination of
exceptional but otherwise unsynchronized dyes. In addition, we
alsoreport on new advances in the enhancement of photochromic
performance in rigid matrices through the development of new
atom efficient telechelic dye-PDMS conjugates (see Scheme 1A).
These new telechelic conjugates not only address the issue of fast

8490 Macromolecules, Vol. 43, No. 20, 2010
Malic et al.
coloration and decoloration kinetics but also of matrix compat-
ibility, an important consideration where a high degree of optical
clarity is required in the event that high loadings of PDMS-
conjugated dyes are needed.
gel column, generally eluting with a mixture of diethyl ether
and hexane.
2. Photochromic Properties. The PDMS conjugates syn-
thesized, their fractions, and corresponding control com-
pounds are outlined in Table 1. These were incorporated within
a standard thermoset lens matrix formulation composed of 4
parts (by weight) ethoxylated Bisphenol A dimethacrylate
(EBPDMA, EO/phenol = 1.3), 1 part poly(ethylene glycol)
400 dimethacrylate (PEGDMA) and 0.4 wt % AIBN (radical
initiator). The mixtures were added to a mold and thermally
cured. The test lenses produced had a thickness of approxi-
mately 2 mm and were subjected to kinetic testing using a light
table comprising a UV-vis spectrophotometer and an external
UV light source. The samples were irradiated with filtered UV
light (350-400 nm) for a duration of 1000 s (coloration) at
which point the light source was turned off and the sample was
further monitored in the dark (decoloration). The temperature
of the lens was maintained at 20 °C (see Experimental Section
for full details of the testing procedure and equipment). When
subjected to UV light irradiation the initially colorless test lens
samples become colored. Upon cessation of irradiation, the
lenses then spontaneously reverted back to their colorless form.
The resulting change in absorbance during this coloration/
decoloration cycle was monitored over time at λmax of the
colored form of the photochromic.
Results and Discussion
1. Synthesis and Fractionation of Photochromic Dye-
PDMS Conjugates. It must be appreciated that many state-
of-the-art photochromic dyes do not appear in the academic
literature but remain relatively hidden in patents. This is a
measure of the high economic value good dyes have. To
illustrate the broad applicability of our technology, we
examined a variety of naphthopyrans (chromenes) and
spirooxazines that appear in patents of some of the major
lens/photochromic dye producers in addition to some con-
ventional literature dyes.
The synthesis of dye-PDMS conjugates is outlined in
Scheme 1 and involves the succinate extension of commer-
cially available hydroxyl end-terminated PDMS followed by
conversion to the acid chloride and reaction with a hydroxyl
(or secondary amine) functionalized (conjugatable) photo-
chromic dye. Alternatively, the succinate functionalized
PDMS may be reacted with the photochromic dye in
a one-pot procedure using N-(3-dimethylaminopropyl)-
N0-ethylcarbodiimide (EDC) hydrochloride and dimethyla-
minopyridine (DMAP). Yields are high for both procedures
with the latter method producing slightly cleaner products.
This is not surprising since the process of producing the acid
chloride functionalized PDMS involves the use of oxalyl
chloride which generates HCl as a byproduct, known to
cleave the siloxane backbone.15 Despite careful control of
reaction conditions (maximum of 30 min reaction time at
ambient temperature), a small amount of byproduct is
inevitable and is detected as nonpolar front-running material
during purification by column chromatography. The use of
Decoloration kinetics were analyzed using the following
biexponential equation:
AðtÞ ¼ A1e- k t þ A2e- k t þ Ath
1
2
where A(t) is the optical density at λmax, A1, and A2 are
contributions to the initial optical density A0 (maximum at-
tained absorbance value at 1000 s UV irradiation), k1 and k2 are
the rates of the fast and slow components, respectively, and Ath
is the residual coloration when time approaches infinity. Appli-
cation of biexponential kinetics provided correlation coefficients
>0.99 in all analyses. This is the most common model used for
photochromic analysis and allows comparison to other litera-
ture reported values.10,16-19 Spectrokinetic data for all com-
pounds tested is presented in Table 2. This table also includes
values of t1/2 and t3/4 which are defined as the time taken for the
initial absorbance value (A0) to be reduced by half and three-
quarters, respectively, during decoloration. These latter values
are of most commercial concern and are commonly used within
the patent literature to define fade-speed performance of photo-
chromic dyes within lens matrices.
EDC HCl/DMAP is a less complicated and milder proce-
3
dure which avoids the in situ formation of deleterious
substances and is preferred. The synthesis of control com-
pounds is also depicted in Scheme 1, which are simply the
propionyl ester (or amide) derivatives of the starting hydroxyl
(or amine) functionalized photochromic dyes.
The PDMS starting materials used here (MCR-C12 and
DMS-C15 from Gelest Inc.) are polydisperse mixtures of
dimethylsiloxane oligomers, which range in nPDMS (number
of dimethylsiloxane repeat units in polymer chain, as defined
in the structures in Scheme 1) from 5 to >20, as determined
by electrospray ionization-mass spectrometry (ESI-MS)
analysis. As a result, the photochromic products are mix-
tures containing conjugates with a range of PDMS chain
lengths. Therefore, analysis by 1H NMR determines values
for molecular weight and nPDMS which are averages. In
addition, conjugates with different chain lengths have dif-
ferent polarities, conjugates with longer PDMS chains being
less polar than conjugates with shorter chains. This polarity
difference allows simple fractionation using column chro-
matography. Paradoxically, high molecular weight conju-
gates of low polarity move faster through a normal phase
silica gel column than do conjugates of lower molecular
weight. Therefore, the photochromic product generally
elutes as a broad band (Figure S1, Supporting Information).
The broadness of this band is influenced also by the polarity
of the solvent system (mobile phase) which can be adjusted
accordingly. The result of this process is that several frac-
tions can be collected which range in average molecular
weight (and nPDMS), from high to low, and have narrower
polydispersities. The conjugates were fractionated on a silica
The results of kinetic testing show that both the telechelic
and mono end-functional photochromic dye-PDMS con-
jugates provide a significant improvement in fade speed over
the nonconjugated control compounds (Table 2).
Our previous studies into the conjugation of free-radical
derived oligomers to photochromic dyes also demonstrated
an ability to tune fade-speed with changing molecular
weight.11,12,20-23 Low Tg oligomers, namely, poly(n-butyl
acrylate) and poly(2-ethylhexyl acrylate), provided fade-
speed enhancement as molecular weight increased.11,12,20
However, large molecular weights, typically between 3000
and 14 000, were required to show an appreciable improve-
ment and a broad distribution of fade-speed performances.
Here we demonstrate that poly(dimethylsiloxane) is a far
more efficient polymer for this purpose, with large fade-
speed improvements gained from relatively low molecular
weight oligomers (approximately between 500 and 1800).
As expected, the highest molecular weight conjugates
(having longest PDMS chain) for each photochromic dye
provide the largest improvement in fade speed performance,
with a decrease of t1/2 ranging between 71 and 88% and a

Article
Macromolecules, Vol. 43, No. 20, 2010 8491
Table 1. Photochromic Dye Functionalized PDMS Conjugates, Nonfractionated Parent Conjugate and Subsequent Fractions with Average
Molecular Weights (Mn) and Average Siloxane Repeat Units within PDMS Chain (nPDMS), and the Corresponding Control Compounds

8492 Macromolecules, Vol. 43, No. 20, 2010
Malic et al.
Table 1. Continued
a Commercially available (James Robinson Ltd.) 5-methoxycarbonyl derivative used as control.
decrease in t3/4 between 80 and 96%, as compared with the
control dyes. The lowest molecular weight conjugates
(shortest PDMS chain), while being the slowest of all the
fractions, also provide a significant fade speed improvement
over the control compounds. Here the reduction in t1/2 and
t3/4 values range between 51 and 76% and 61-86%, respec-
tively, across the range of photochromic dyes tested. These
results are reflected in the values for k1 (fast rate constant)
which show a steady increase going from fractions of low to
high molecular weight. Interestingly, values for A0 are gen-
erally higher for the conjugates compared to the control
compounds, achieving a virtual steady state of coloration far
before that of the control whose coloration is generally still
on the incline at 1000 s UV irradiation. A further feature to
note is that the dye-PDMS conjugates tested here have a
significantly lower residual coloration (Ath) in the last stages
of decoloration in the dark than the corresponding noncon-
jugated control compounds. In addition, lenses containing
the conjugates were also observed to have lower baseline
coloration in their fully bleached state.
their plots considerably to the left of curves corresponding to
mono end-functionalized conjugates. Thus, it can be con-
cluded that telechelic conjugates provide a more atom effi-
cient use of PDMS, with less than half the chain length
required to provide the same fade speed enhancement.
The relationship between fade speed and the length of
PDMS chain is depicted in Figure 2 (Figures S2-S9, Sup-
porting Information). This plot shows that fade speed in-
creases with chain length, with extrapolation of the curves
indicating an approach to a limit after which longer PDMS
chain lengths will not provide further appreciable fade speed
enhancements. We also observe that the fade speed of the
nonfractionated conjugate product falls on the curve gener-
ated by its corresponding derived fractions. This indicates
that polydispersity does not influence fade speed, which is
only dependent on average molecular weight. Figure 2 shows
the plots of t1/2 and t3/4 versus chain length (nPDMS) of
the naphthopyran functionalized PDMS conjugates 10a-d
and 11a-c, which indicate a crossover point at nPDMS ca. 15
and 18, respectively, where shorter PDMS chain lengths of
telechelic conjugates perform better at enhancing fade speed
than the corresponding mono end-functionalized conju-
gates. Interestingly, this crossover point is also observed
for the series of spirooxazine conjugates 1a-d, 2a-c and
4a-c, 5a-c, although here it is shifted to lower nPDMS values
(see Supporting Information). This crossover seems to be a
relatively common feature of this conjugation system. How-
ever, if we were to plot fade speed versus chain length per dye
moiety (Figure 2, bottom plot) then all nPDMS values for
telechelic conjugates would essentially be halved, putting
3. Matrix Compatibility. The atom efficiency of the tele-
chelic approach provided additional flow-on advantages.
Reducing the amount of PDMS required for fade speed
enhancement also enhances matrix compatibility. Poly-
(dimethylsiloxane) itself is an oily substance that is not very
compatible with many lens matrix materials, particularly
those of commercial significance. Phase separation of PDMS
materials within a lens matrix leads to hazing and blooming,
a characteristic obviously undesirable in ophthalmic appli-
cations. The PDMS materials used herein are of a relatively
low molecular weight (average ca. 1200), and therefore the
presence of large organic photochromic moieties (molecular
weights ca. 400-550) at the PDMS termini dramatically
increases the matrix compatibility of the corresponding
conjugates. Of course, two photochromes are better than
one in this regard and so telechelic conjugates out-perform
mono end-functionalized conjugates (see Figure 3). This
appears to be a synergistic kind of relationship where the
PDMS provides a rapid switching environment and the dye
provides matrix compatibility to the PDMS. Matrix compat-
ibility is particularly an issue where high concentrations of
photochromics are required, such as in lens coatings. When

Article
Macromolecules, Vol. 43, No. 20, 2010 8493
Table 2. Spectrokinetic Data of the Ambient Thermal Decoloration (Colored Form to Uncolored Form) for All Conjugates and Controls
within a Test Lens Matrix Comprised of Ethoxylated Bisphenol A Dimethacrylate (EBPDMA): Poly(ethylene glycol) 400 Dimethacrylate
(PEGDMA), (4:1)
compound
t1/2 (s)
t3/4 (s)
A0
A1
k1 (min-1
)
A2
k2 (min-1
)
Ath
conc (mol/g)
λmax (nm)
1
1a
1b
1c
1d
2
2a
2b
2c
3
4
4a
4b
4c
5
5a
5b
5c
6
7
7a
7b
8
8a
8b
8c
9
10
30
21
24
30
33
25
22
26
37
80
16
12
16
18
14
12
17
21
45
10
7
77
50
59
76
93
67
54
69
120
343
42
27
40
56
34
27
45
71
213
28
14
55
21
18
21
37
234
127
89
110
125
190
151
84
130
237
1482
183
139
167
166
189
232
168
120
122
151
198
255
978
594
483
578
617
572
518
591
777
2465
271
211
240
276
332
1.617
1.279
1.292
1.378
1.334
1.199
1.134
1.367
1.351
1.169
0.802
0.732
0.820
0.799
0.811
0.666
0.838
0.839
0.813
1.745
1.440
1.855
1.664
1.842
1.947
2.161
1.421
0.780
0.843
0.841
0.801
0.825
0.922
0.884
0.948
0.927
0.739
0.531
0.943
0.794
0.883
0.832
0.827
0.791
0.650
0.732
0.879
0.864
0.757
0.767
0.898
0.935
0.827
0.870
0.778
0.910
0.890
0.796
0.735
0.894
0.827
0.860
0.842
0.745
0.803
0.864
0.834
0.804
0.772
0.803
0.838
0.790
0.728
0.593
0.816
0.907
0.825
0.772
0.840
0.895
0.801
0.740
0.618
0.792
0.932
0.741
0.810
0.850
0.827
0.782
0.559
0.748
0.759
0.748
0.735
0.722
0.740
0.746
0.743
0.702
0.562
0.781
0.810
0.782
0.776
0.765
0.705
0.776
0.840
0.839
0.788
0.718
0.694
0.626
0.638
0.657
0.638
0.633
0.629
0.651
0.638
0.611
0.529
0.743
0.782
0.749
0.745
0.704
1.611
2.165
1.913
1.571
1.470
1.849
2.143
1.831
1.362
0.892
3.000
3.795
3.087
2.601
3.420
3.841
2.903
2.373
1.396
4.289
6.986
3.050
5.129
6.397
5.287
3.945
1.699
1.572
1.750
1.535
1.448
1.260
1.455
1.835
1.512
1.289
0.976
0.869
0.970
0.869
0.868
0.826
0.905
0.876
1.021
1.009
0.931
0.998
0.899
0.335
0.812
0.871
0.794
0.740
0.788
0.863
0.783
0.720
0.320
0.567
0.618
0.580
0.539
0.529
0.147
0.106
0.121
0.142
0.170
0.140
0.127
0.149
0.196
0.296
0.134
0.078
0.132
0.162
0.117
0.084
0.143
0.183
0.267
0.128
0.062
0.166
0.109
0.093
0.105
0.135
0.255
0.087
0.106
0.101
0.124
0.052
0.060
0.095
0.083
0.064
0.175
0.075
0.070
0.061
0.061
0.069
0.137
0.060
0.078
0.051
0.052
0.128
0.151
0.184
0.237
0.243
0.246
0.237
0.239
0.234
0.233
0.244
0.255
0.161
0.126
0.144
0.168
0.188
0.126
0.166
0.141
0.122
0.118
0.122
0.161
0.127
0.099
0.079
0.151
0.175
0.162
0.138
0.152
0.171
0.142
0.125
0.093
0.102
0.131
0.091
0.125
0.123
0.117
0.102
0.070
0.008
0.003
0.003
0.003
0.027
0.013
0.003
0.006
0.029
0.069
0.039
0.009
0.040
0.040
0.039
0.113
0.042
0.006
0.015
0.039
0.119
0.105
0.023
0.038
0.035
0.038
0.040
0.043
0.037
0.038
0.041
0.023
0.094
0.125
0.106
0.092
0.085
0.012
0.007
0.008
0.013
0.014
0.014
0.009
0.014
0.023
0.057
0.014
0.008
0.013
0.018
0.012
0.007
0.016
0.023
0.046
0.020
0.009
0.027
0.014
0.013
0.014
0.019
0.053
0.117
0.082
0.093
0.074
0.167
0.148
0.094
0.118
0.170
0.217
0.108
0.084
0.115
0.117
0.118
0.135
0.119
0.059
0.080
0.113
0.130
0.131
0.119
0.091
0.069
0.083
0.096
0.094
0.082
0.094
0.110
0.155
0.082
0.074
0.084
0.071
0.087
0.6 ꢀ 10-6
630
1.2 ꢀ 10-6
1.2 ꢀ 10-6
0.6 ꢀ 10-6
590
1.2 ꢀ 10-6
1.2 ꢀ 10-6
0.6 ꢀ 10-6
610
15
8
7
1.2 ꢀ 10-6
8
11
31
33
29
32
34
40
35
27
33
41
92
59
52
57
58
62
69
56
47
47
53
61
71
186
90
81
92
100
93
82
93
110
280
99
86
94
105
116
1.2 ꢀ 10-6
0.75 ꢀ 10-7
515
10a
10b
10c
10d
11
11a
11b
11c
12
1.5 ꢀ 10-7
1.5 ꢀ 10-7
13
0.75 ꢀ 10-7
561
13a
13b
13c
13d
13e
14
14a
14b
14c
14d
14e
15
1.5 ꢀ 10-7
1.5 ꢀ 10-7
16
0.75 ꢀ 10-7
585
16a
16b
16c
17
17a
17b
17c
18
1.5 ꢀ 10-7
1.5 ꢀ 10-7
19
0.75 ꢀ 10-7
567
19a
19b
19c
19d

8494 Macromolecules, Vol. 43, No. 20, 2010
Malic et al.
Table 2. Continued
compound
t1/2 (s)
t3/4 (s)
A0
A1
k1 (min-1
)
A2
k2 (min-1
)
Ath
conc (mol/g)
λmax (nm)
20
74
69
78
78
107
237
37
34
39
42
42
28
27
29
33
36
100
27
22
24
27
28
23
27
32
105
9
7
7
8
9
9
5
6
7
10
42
39
43
114
220
181
219
225
353
908
104
83
109
120
124
81
0.777
0.920
0.948
0.841
0.795
0.620
0.622
0.602
0.782
0.697
0.607
0.769
0.688
0.784
0.803
0.737
0.690
0.972
1.114
1.080
1.103
0.715
0.762
0.756
0.729
0.613
0.624
0.982
0.961
1.011
0.920
0.572
0.823
1.074
1.117
1.087
0.592
0.929
0.633
0.842
0.723
0.756
0.733
0.730
0.670
0.639
0.801
0.842
0.802
0.798
0.792
0.780
0.806
0.789
0.774
0.751
0.640
0.743
0.759
0.740
0.716
0.722
0.738
0.732
0.704
0.548
0.865
0.771
0.760
0.740
0.709
0.838
0.861
0.813
0.752
0.701
0.557
0.772
0.798
0.584
0.776
0.791
0.725
0.727
0.591
0.241
1.311
1.508
1.252
1.156
1.180
1.652
1.772
1.644
1.459
1.396
0.714
2.067
2.290
2.221
2.047
2.000
2.099
2.032
1.791
0.837
5.461
7.540
7.307
6.282
4.929
5.437
10.852
7.955
5.534
4.146
1.624
1.169
1.083
0.633
0.156
0.136
0.152
0.156
0.202
0.207
0.083
0.090
0.083
0.081
0.049
0.114
0.117
0.115
0.046
0.056
0.157
0.093
0.102
0.095
0.106
0.098
0.108
0.095
0.109
0.217
0.170
0.159
0.162
0.168
0.180
0.176
0.108
0.123
0.139
0.159
0.289
0.138
0.119
0.256
0.101
0.145
0.111
0.098
0.077
0.024
0.004
0.002
0.004
0.004
0.016
0.003
0.002
0.003
0.020
0.028
0.070
0.041
0.016
0.039
0.042
0.041
0.013
0.042
0.048
0.045
0.181
0.121
0.117
0.106
0.094
0.174
0.264
0.175
0.119
0.097
0.085
0.044
0.040
0.047
0.091
0.085
0.087
0.084
0.094
0.080
0.076
0.053
0.076
0.080
0.118
0.048
0.035
0.045
0.133
0.138
0.169
0.124
0.089
0.123
0.129
0.132
0.088
0.132
0.141
0.173
0.018
0.023
0.027
0.028
0.031
0.021
0.011
0.016
0.022
0.030
0.067
0.024
0.028
0.095
1.5 ꢀ 10-7
20a
20b
20c
20d
21
1.5 ꢀ 10-7
22
0.75 ꢀ 10-7
463
22a
22b
22c
22d
23
23a
23b
23c
23d
24
1.5 ꢀ 10-7
72
81
108
128
547
105
76
101
135
129
88
123
185
1326
31
25
28
35
50
34
11
17
29
47
1.5 ꢀ 10-7
1.5 ꢀ 10-7
25
592
25a
25b
25c
26
26a
26b
26c
27
1.5 ꢀ 10-7
1.5 ꢀ 10-7
1.5 ꢀ 10-7
28
623
28a
28b
28c
28d
29
29a
29b
29c
29d
30
3.0 ꢀ 10-7
303
114
115
616
3.0 ꢀ 10-7
35a
35b
36
0.75 ꢀ 10-7
615
1.5 ꢀ 10-7
the test lenses were loaded with increasing amounts of a
mono end-functionalized (11a) and telechelic (10a) PDMS-
conjugated naphthopyran, it was the mono end-functionalized
conjugate that first phase separated (Figure 3). It must be noted
that the concentration of PDMS is quite high and it should
not be concluded that the mono end-functionalized conjugate
has inherently poor compatibility. Rather, telechelic conjugates
should be viewed as having superior compatibility.
To analyze the efficacy of telechelic conjugation versus mono
end-functionalization in the reduction of phase separation and
hazing the naphthopyran conjugates 10a and 11a and spiroox-
azine conjugates 7a and 8a were incorporated within a test lens
matrix (EBPDMA/PEGDMA) at equimolar dye concentra-
tions and with a very high loading. The lenses were then analyzed
using a haze-meter, the results of which are given in Table 3. The
most striking result here is of the lens containing conjugate 11a
which shows gross phase separation with a severely reduced
transmission and large haze reading compared to the lens
containing telechelic conjugate 10a, which remains transparent.
Such a large difference is not seen between spirooxazine con-
jugates 7a and 8a, which is an indicator of the influence of the
photochromic end group toward overall matrix compatibility.
The relatively low transmittance of telechelic conjugate 10a is a
result of the high baseline coloration due to the high loading of
photochromic.
arises, then we have shown that telechelic PDMS conjugates
have superior compatibility to the mono-end functional geo-
metry with minimal impact on switching speeds.
4. Independent Switching in Multiple Photochromic Dye
Conjugate Systems. The haze associated with the incompat-
ibility of PDMS within matrix materials arises from the
phase separation of the polymer, forming aggregates of
sufficient size to cause light scattering. As demonstrated in
the previous section, sufficient loading of the photochromic
dye-PDMS conjugates may result in such phase separation.
The question still arises, however, as to whether aggregation
still occurs at lower concentrations where no hazing is visible,
where aggregates are not sufficiently large to scatter visible
light. We postulated that aggregation of different dye-PDMS
conjugates having different chain lengths could affect each
others kinetic performance, conjugates with long chains may
have their kinetic performance slowed on aggregation with
shorter chained conjugates, and vice versa.
For PDMS conjugation to be of practical use in the tuning
of coloration and decoloration speeds of different dyes,
applicable to commercial multidye lens systems with neutral
tints, the individual conjugate components must act inde-
pendently of one another. We devised a test to determine the
independence of performance which involved the incorpora-
tion of conjugate 13e within the test lens matrix formulation
together with varying amounts of a nonphotochromic model
compound 33 (Table 4). This latter compound was synthe-
sized in order to replicate the presence of a second conjugate,
Thus, compatibility of the PDMS conjugates is influenced by
loading, molecular weight, type of photochromic agents, and
the geometry of the conjugate. If an issue of phase separation

Article
Macromolecules, Vol. 43, No. 20, 2010 8495
Figure 3. Haze test, showing mono end-functional dye-PDMS con-
jugate 11a (left) and telechelic conjugate 10a (right) incorporated within
a test lens formulation, ethoxylated bisphenol A dimethacrylate
(EBPDMA): poly(ethylene glycol) 400 dimethacrylate (PEGDMA),
(4:1), at a high equimolar concentration (1.975 ꢀ 10-5 mol/gmatrix with
respect to the photochromic moiety).
Table 3. Haze-Meter Testing of Highly Loaded Lenses Containing
Equimolar Quantities (With Respect to Photochromic Moiety) of
Telechelic and Mono End-Functionalized Photochromic
Dye-PDMS Conjugates
conjugate
concentration (mol/g)
transmittance, %
haze
blank lens
85.3
62.9
33.5
78.4
73.0
2.00
7.52
43.5
4.09
10.3
10a
11a
7a
0.988 ꢀ 10-5
1.975 ꢀ 10-5
2.0 ꢀ 10-5
8a
1.0 ꢀ 10-5
Table 4. Decoloration Performance of Photochromic Conjugate 13e
(nPDMS = 8.4) in Test Lens Matrix (EBPDMA/PEGDMA) Con-
taining Varying Amounts of Non-Photochromic Model Compound 33
(nPDMS = 22.3)
photochromic
conjugate, 13e
(molar equiv)a
non-photochromic
conjugate, 33
(molar equiv)
t1/2
(s)
t3/4
(s)
b
entry
A0
1
2
3
4
5
1
1
1
1
1
0
2
4
8
16
0.21
0.21
0.19
0.20
0.19
74
72
69
72
71
241
233
222
234
229
a Conjugate conc (1 molar equiv) = 1.88 ꢀ 10-8 mol/g (dye conc =
3.75 ꢀ 10-8 mol/g). b Absorption at 1000 s UV irradiation.
Scheme 2. Synthesis of the Non-Photochromic Model Telechelic
PDMS Conjugate
Figure 2. Plots of t1/2 and t3/4 versus nPDMS (top and middle) for
naphthopyran-PDMS conjugates 10, 10a-d (telechelic conjugates)
and 11, 11a-c (mono end-functionalized conjugates). Plot of t1/2
versus nPDMS per dye moiety (bottom), indicating telechelic conju-
gates to be a far more atom efficient use of PDMS for fade speed
enhancement.
both chemically and sterically, but without having an ab-
sorption in the visible spectrum. This allowed the accurate
analysis of fade speed performance of only the photochromic
conjugate by eliminating interference from a second source of
variable absorption (a second photochromic). The synthesis of
the model compound 33 (Scheme 2) involved the hydrogenation
of the pyran double bond of an actual photochromic dye, 31,
producing a colorless and nonphotochromic analogue 32,
which was subsequently conjugated to PDMS and then fraction-
ated. The highest molecular weight fraction (nPDMS=22.3) was
chosen in an attempt to increase the fade speed performance
of the low molecular weight photochromic conjugate 13e
(nPDMS = 8.4). The results in Table 4 show no change in decolo-
ration performance between the control test lens containing
only the photochromic conjugate (entry 1) and the lenses
containing the model conjugate up to 16 mol equiv with respect

8496 Macromolecules, Vol. 43, No. 20, 2010
Malic et al.
Figure 4. Plots of the range of t1/2 values of each photochromic dye conjugate system tested in a rigid polymer matrix, indicating (i) fade speed
enhancement due to PDMS conjugation to the dye, and (ii) potential for synchronization in multidye systems where overlap is observed.
to 13e (entries 2-5), with t1/2 and t3/4 values remaining uniform.
This indicates that photochromic conjugate 13e is not affected
by the presence of a second conjugate, at least at the concentra-
tions tested.
The same experiment was also performed with mono end-
functionalized dye-PDMS conjugate 11c (nPDMS = 8.7), but at
two different concentrations (Table S1, Supporting Informa-
tion). In this case, we also observe that the fade performance of
11c remains uniform across the whole range of concentrations
used, once again indicating independent kinetic performance
of the photochromic. Therefore, fade speed matching of diffe-
rent dye-PDMS conjugates via the process of fractionation is
indeed feasible.
this purpose was facilitated by plotting the range of t1/2 values
obtained for each photochromic dye system (both mono end-
functional and telechelic) as seen in Figure 4. (Note: these ranges
are not absolute, as the extremities of each range may be ex-
tended by the use of shorter and longer PDMS oligomers than
was used herein.) Plots for the ranges of t3/4 values are included
in the Supporting Information (Figure S10). An overlap in the
range of t1/2 and t3/4 values indicates the potential for synchro-
nization. From analysis of these plots and the kinetic fade data
of the various fractions of dyes 14 and 22 it was clear that mono
end-functional conjugate 14b (nPDMS=15.9) and telechelic con-
jugate 22d (nPDMS = 6.1) had similar switching speeds with t1/2
values of 47 and 42 s and t3/4 values of 122 and 124 s, respec-
tively. Additionally, the λmax values of each dye conjugate (560
and 463 nm, respectively) are sufficiently different so when
combined would produce a lens having a broad absorption in
the visible spectrum upon UV irradiation. The superimposed
normalized kinetic plots of both dye conjugates in separate
5. Synchronized Switching in Multiple Photochromic Dye
Conjugate Systems. We further tested the system by incor-
porating two different photochromic conjugates with almost
identical kinetic performance within the same lens. The choice of
two different and synchronized photochromic conjugates for

Article
Macromolecules, Vol. 43, No. 20, 2010 8497
lenses are shown in Figure 5, which indicates very good
synchronicity during coloration and decoloration. A slight
deviation is seen after the t3/4 point of decoloration and is mainly
due to a difference in the residual coloration (Ath) of each
conjugate. In contrast, when the kinetic plots of the correspond-
ing control compounds, 15 and 24, are superimposed there is an
obvious mismatch (Figure S11, Supporting Information), as is
also indicated by their values for t1/2 (236 vs. 100 s) and t3/4 (908
vs. 547 s), respectively.
Conjugates 14b (purple, λmax = 560 nm) and 22d (orange,
max = 463 nm) were then combined in the same lens matrix
λ
at a molar ratio of 0.5:1.25, respectively, producing an
effective dye ratio of 1:1.25. The lens was analyzed by
recording the entire visible spectrum at intervals of 30 s
during both coloration and decoloration in the dark
(Figure 5, middle plots). Synchronization was then evaluated
by plotting the normalized absorption values at the wave-
lengths of 560 and 463 nm (λmax values of the individual dye
components) versus time (Figure 5, bottom plot), which
indeed shows an even change in absorption across the visible
spectrum with no color shift during coloration and until after
the t3/4 point of decoloration. This plot is an almost identical
replication of the plot of the superimposed kinetic profiles of
each individual dye component (Figure 5, top). A photo-
graphic illustration of this lens during decoloration under
indoor ambient lighting conditions is shown in Figure 6 (left
lens) and shows a fast and very uniform color fade to the
naked eye.
The decoloration process can be both thermally driven or
photoinduced (usually by intense visible light). Decoloration
in these experiments was monitored in the dark to allow
evaluation of challenging and commercially critical thermal
decoloration reactions. The persistence of color of approxi-
mately 0.15-0.25 absorbance units (Figures 5, S10, S11, and
S12, Supporting Information) is due to the presence of a
minor and relatively thermally stable isomer of the open
(colored) form of the respective dyes. This is a typical
characteristic of these types of 2H-naphthopyrans and in-
deed of other chromene photochromic compounds.12,24-28
Therefore, under normal indoor ambient lighting conditions
the test samples would and do continue to slowly decolorize.
The two corresponding nonsynchronized control com-
pounds, 15 and 24, were also incorporated together in a test
lens matrix as a comparison. As expected, the decoloration
process was far slower and an uneven change in absorbance
at 463 and 560 nm was observed (Figure S12, Supporting
Information). Despite the individual kinetics of these two
nonconjugated control compounds being nonsynchronized,
as depicted in Figure S11 (Supporting Information), when
combined in the same matrix the change in absorption at
the corresponding wavelengths of maximum absorption of
the individual dyes is not as stark (Figure S12, Support-
ing Information). This is most probably due to the overlap
of the absorbances of each dye in the visible region, which
seems to have a “smoothing” effect on the overall decolora-
tion across the broader (combined) absorption profile. The
smoothing effect can be explained by the individual orange-
colored dye 24 not having an appreciable absorption at 560
nm (the absorption maximum of the purple colored dye 15),
whereas both purple dye 15 and orange dye 24 absorb light at
463 nm (the absorption maximum of orange dye 24). So
monitoring the change in absorption at 560 nm will essen-
tially be free from the influence of the orange dye and moni-
toring at 463 nm will produce a kinetic profile that results
from the combined influences of both dyes. In effect, since
the purple dye is the slower of the two the change in absor-
bance at 463 nm is thus also slowed when compared to the
Figure 5. Superimposed kinetic profiles of coloration (60-1000 s) and
decoloration (1000 s onward) of individual synchronized “speed-
matched” photochromic dye-PDMS conjugates 14b and 22d (top);
visible spectrum at 30 s intervals during coloration and decoloration
(middle plots) of lens containing combination of 14b (purple, λmax
=
560 nm) and 22d (orange, λmax = 463 nm) conjugates with synchronized
switching performance, of which the absorbance values at 463 and 560
nm are plotted versus time (bottom plot).

8498 Macromolecules, Vol. 43, No. 20, 2010
Malic et al.
Figure 7. Top: Superimposed individual kinetic plots of nonsynchro-
nized dyes 14b (purple dye-PDMS conjugate) and 24 (orange non-
PDMS conjugated control dye) within test lens (EBPDMA/PEGDMA,
4:1). Bottom: Monitoring of color development and decoloration in the
dark of lens sample containing combined nonsynchronized dyes 14b
and 24. Absorbance readings taken at 560 and 463 nm (λmax values of
the individual dye components, respectively) from visible spectrum
recorded at 30 s intervals.
individual dye components in separate lenses, which mirrors
that of the bottom plot corresponding to the lens containing the
combined dyes). Physical examination of the lens when exposed
to sunlight saw an initial purple color develop due to the faster
conjugate 14b. This was followed by a red-brown as the lens
approached its steady state of coloration. Conversely, a yellow-
ing of the lens was observed during decoloration, as the
absorbance of the purple colored conjugate, 14b, decreased at
a faster rate than the orange-colored control compound, 24. The
yellowing can clearly be seen in the photographic illustration,
Figure 6 (middle lens).
Figure 6. Test lenses at intervals during decoloration. Left lens: com-
bined synchronized “speed-matched” photochromic dye-PDMS con-
jugates 14b and 22d (fast and synchronized switching). Middle lens:
combined nonsynchronized dyes 14b (purple dye-PDMS conjugate)
and 24 (orange non-PDMS conjugated control dye). Right lens: non-
synchronized, non-PDMS conjugated control dyes 15 and 24.
As mentioned previously, several different colored photo-
chromic dyes are usually included in commercial lenses in
order to achieve tints of gray or brown, which is acceptable to
the consumer. We also have been successful in achieving a
neutral gray coloration in our standard test lens formulation
by the combination of three dyes (Figure S13, Supporting
Information). Conjugation of these three dyes to PDMS,
each of different length, allowed us to significantly enhance
and synchronize their coloration and decoloration perfor-
mance compared to that of a control lens containing the
same photochromes in their non-PDMS conjugated form.
The conjugates 22c, 14b, and 35b were combined in a ratio of
1.25:0.6:1.0 (with respect to the dye moieties), with the blue
conjugate 35b incorporated at a concentration of 0.75 ꢀ 10-7
mol/g (effective dye concentration of 1.5 ꢀ 10-7 mol/g). The
control dyes 24, 25, and 36 were combined in a test lens at the
individual kinetics of the orange dye. A photographic illus-
tration of this lens during decoloration under indoor ambi-
ent lighting conditions is shown in Figure 6 (right lens) and
shows a slow but fairly uniform color fade to the naked eye.
To further demonstrate the effects of the combination of non-
synchronized photochromes the control compound 24 (orange,
λmax = 463nm, t1/2 = 100 s, t3/4 = 547 s) was now incorporated
with the faster conjugate 14b (purple, λmax=560 nm, t1/2=47 s,
t3/4 = 122 s) within the test lens matrix, as an exaggerated
example. The visible spectrum was once again recorded at 30 s
intervals during coloration and decoloration and the absor-
bance at 560 and 463 nm plotted over time. Figure 7 (bottom
plot) shows the absorbance at 560 nm increasing and decreasing
much faster than at 463 nm. (For comparison purposes, the top
plot of Figure 7 shows the superimposed kinetic plots of the

Article
Macromolecules, Vol. 43, No. 20, 2010 8499
due to the broad and fairly even absorbance across the visible
range. The visible absorbance spectra of each individual dye
component are also included, with intensities adjusted to
approximate each contribution based on concentration
(ratio) and optical densities at 1000 s UV irradiation
(orange, purple, and blue lines).
Concluding Remarks
This report demonstrated (1) the ability to enhance and tune
the coloration and fade speed of photochromic dyes through
conjugation to PDMS and fractionation to give a range of
conjugate molecular weights (differing average PDMS chain
lengths), (2) synchronization of switching speeds of different dyes
through the PDMS conjugation and fractionation process, and
(3) a more atom efficient method of functionalizing photochro-
mic dyes with PDMS through the use of telechelic PDMS. The
fractionation method worked for both telechelic and mono end-
functional PDMS-dye conjugates. As evidenced in Table 2 and
Figure 2, fractionation allows the ability to tune the fade speed
performance of a photochromic dye within a rigid polymeric
matrix, with a clear trend of longer PDMS chain lengths provid-
ing faster switching than shorter chain lengths. This process has
obvious commercial significance in that many currently available
lenses contain mixtures of different colored dyes to produce
neutral tints of gray and brown. The individual kinetics of these
dyes must be virtually identical to avoid a change in hue during
coloration and decoloration. It is not common that a single
photochromic dye has all the necessary characteristics required to
produce a photochromic lens article with desirable properties,
namely, fast coloration/decoloration kinetics in a polymeric
matrix, low coloration in the absence of UV light, high coloration
during solar irradiation, good fatigue resistance as well as a
neutral tint. Therefore, research into the synthesis and discovery
of novel photochromic dyes with favorable properties is ongoing.
Synchronization between dyes becomes increasingly important as
the absolute switching speed increases. A difference of 50 s
between two dyes may be acceptable in dyes with t1/2 of 250
and 300 s but unacceptable when PDMS conjugation drops the
t1/2 to only 50 and 100 s. Thus, as products strive toward
increasingly faster photochromic transitions in optical lenses
the capacity to synchronize dyes becomes essential. It can be
seenin thisreport how PDMS conjugation and fractionation may
be employed as a means of both increasing switching speeds and
matching two or more dyes that would otherwise not be syn-
chronized, thus opening up further possibilities in advancements
over current photochromic lens technology. This methodology
would be applicable to other molecules whose functionality
depended on their molecular mobility, such as fluorescent or
color glass transition (Tg) probes1 and free volume probes.2
Figure 8. Decoloration under ambient lighting conditions of fast and
synchronized gray colored lens system containing 3 dye-PDMS con-
jugates (22c, 14b, and 35b, right), versus 3 dye control lens (contains 24,
25, and 36, left).
same ratio. Figure 8 shows the decoloration of both the fast
synchronized gray lens (right) and the control lens (left)
under ambient lighting conditions.
Experimental Section
Materials and Methods. Hydroxy-terminated poly(dimethyl-
siloxane) starting materials were purchased from Gelest, Inc. All
other reagents were purchased from Aldrich and used as sup-
plied, unless stated otherwise. Synthesis procedures for all other
conjugatable photochromic dye starting materials can be found
in the Supporting Information. Mono end-functional photo-
chromic dye-poly(dimethylsiloxane) conjugates (2, 5, 8, 11, 14,
17, 20, 23, 26, 29) and control compounds (3, 6, 9, 12, 15, 18, 21,
24, 27, 30, 36) were synthesized using identical reaction condi-
tions to those described elsewhere.13 The general synthesis
procedure for telechelic photochromic dye-PDMS conjugates
(two methods) is outlined below using 1 and 4 as examples.
Details for all other telechelic and mono end-functional con-
jugates synthesized can be found in the Supporting Information.
General Experimental Measurements. 1H (400 MHz/200
MHz) and 13C (100 MHz/50 MHz) NMR spectra were obtained
The two major component dyes in the control lens, 24
(orange) and 36 (blue), coincidentally have very similar fade
speed performance, as can be seen from their t1/2 and t3/4 values
(Table 2 and Figure S13, Supporting Information). The result-
ing gray control lens thus maintains a fairly even neutral hue
upon decoloration but is very slow. The very different chain
lengths of PDMS required to synchronize the switching perfor-
mance upon conjugation, orange-colored 22c has nPDMS = 8.3
versus 35b having nPDMS = 23.1, demonstrates that every dye is
affected differently by conjugation and local environment with-
in the matrix.
The visible spectrum of the gray lens, containing three
synchronized dyes, at the point of maximum coloration
(1000 s UV irradiation), is included in the Supporting
Information (Figure S14, black line). Its gray coloration is

8500 Macromolecules, Vol. 43, No. 20, 2010
Malic et al.
with a Bruker AV400 or a Bruker AC200 spectrometer at 25 °C.
Spectra were recorded for samples dissolved in deuterated
solvent, and chemical shifts are reported in parts per million
from external tetramethylsilane and J values are given in Hz.
Positive ion EI mass spectra were run on a ThermoQuest
MAT95XL mass spectrometer using ionization energy of
70 eV. Accurate mass measurements were obtained with a high
resolution of 5000-10000 using PerFluoroKerosene (PFK) as
the reference sample. Positive and negative ion electrospray
mass spectra (ESI-MS) were acquired with a VG Platform mass
spectrometer using a cone voltage of 50 V with the source
maintained at 80 °C. Methanol was used as solvent system with
a flow rate of 0.04 mL min-1. Molecular weights of PDMS were
obtained from 1H NMR spectra from integration values of
SiCH2 resonances along the backbone with respect to those of
Si(CH3)2. Final molecular weights of dye-PDMS conjugates
were additionally confirmed from integration of characteristic
dye end groups. Photochromic analyses were performed on
lenses containing photochromic materials at doping concentra-
tions chosen in order to maintain optical densities in a mean-
ingful detector range during photochromic kinetic tests (refer to
Table 2). The fabrication and composition of test lenses are
outlined within the main body text. Under continuous irradia-
tion, the photochromic responses of the lenses were analyzed on
a light table comprising a Cary 50 UV-vis spectrophotometer
to measure absorbance values and a 160 W Oriel xenon lamp as
an incident light source. A series of two filters (Edmund Optics
WG320 and Edmund Optics band-pass filter U-340) were used
to restrict the output of the lamp to a narrow band (350-400
nm). The samples were maintained at 20 °C and monitored at
the maximum absorbance of their colored form for a period of
1000 s. Then the thermal decoloration was monitored in the
dark for a further 2400 s (minimum).
septum, with a slight positive pressure. The solvent and excess
reagent was then evaporated in vacuo. Residual oxalyl chloride
and HCl was removed by dissolution in dichloromethane and re-
evaporation of solvent. The oily product was then used imme-
diately. This material cannot be stored for extended periods as
residual HCl degrades the siloxane polymer.
Telechelic Poly(dimethylsiloxane) Conjugated 1,3-Dihydro-1-
isobutyl-3,3-dimethyl-60-(4-(N-ethyl, N-(2-hydroxyethyl)amino)-
phenyl)-spiro[2H-indole-2,20[2H]naphtha[1,2-b][1,4]oxazine],
1. Method A. Carboxylic acid-terminated poly(dimethylsilo-
xane) (0.627 g, 0.428 mmol), EDC HCl (0.214 g, 1.114 mmol),
3
4-dimethylaminopyridine (0.105 g, 0.856 mmol), and 1,3-dihy-
dro-1-isobutyl-3,3-dimethyl-60-(4-(N-ethyl, N-(2-hydroxyethyl)-
amino)phenyl)-spiro[2H-indole-2,20[2H]naphtha[1,2-b][1,4]oxa-
zine] (0.457 g, 0.856 mmol) were combined in dry CH2Cl2 (15 mL)
under a nitrogen atmosphere and stirred at room temperature
overnight. The solvent was evaporated in vacuo and the residue
was purified by column chromatography eluting with 0-20%
EtOAc/petroleum ether to give the product as a green oil (0.97 g,
95%). This material was then fractionated by column chroma-
tography using the same solvent system. Average molecular
weights (Mn) were determined by 1H NMR analysis. Nonfrac-
tionated product, 1: Mn=2384 (nPDMS=12.0). Fraction 1, 1a:
Mn=3213 (nPDMS=23.2). Fraction 2, 1b: Mn=2710 (nPDMS
=
General Synthesis of Telechelic Photochromic Dye-PDMS
Conjugates.
17.0). Fraction 3, 1c: Mn=2,359 (nPDMS=11.8). Fraction 4, 1d:
Mn = 1829 (nPDMS = 8.5). 1H NMR (Fraction 3, 1c; 400 MHz,
CDCl3) δ 8.05-7.91 (m, 4H), 7.72 (s, 2H), 7.45 (s, 2H), 7.40-
7.33 (m, 8H), 7.21 (dt, J=7.7, 1.2 Hz, 2H), 7.09 (dd, J=7.3, 0.9
Hz, 2H), 6.89 (dt, J= 7.5, 0.8 Hz, 2H), 6.82 (d, J = 8.8 Hz, 4H),
6.61 (d, J = 7.8 Hz, 2H), 4.33 (t, J = 6.5 Hz, 4H, CH2-8), 4.24
(m, 4H, CH2-5), 3.65-3.61 (m, 8H, CH2-4,9), 3.48 (q, J = 7.0
Hz, 4H, CH2-10), 3.42 (t, J=7.1 Hz, 4H, CH2-3), 2.98 (ddd,
J= 23.4, 14.5, 7.6 Hz, 4H, isobutyl-CH2), 2.71-2.64 (m, 8H,
CH2-6,7), 2.12-2.06 (m, 2H, isobutyl-CH), 1.68-1.58 (m, 4H,
CH2-2), 1.39 (2 ꢀ s, 12H, spirooxazine geminal-CH3), 1.25 (m,
6H, ethyl-CH3), 0.98 (d, J = 6.6 Hz, 6H, isobutyl-CH3), 0.92
(d, J=6.7 Hz, 6H, isobutyl-CH3), 0.55-0.49 (m, 4H, CH2-1),
0.10-0.04 (m, 76H, SiCH3) ppm. Refer to graphic above for
corresponding numbering system used in NMR assignments.
Carboxylic Acid-Terminated Poly(dimethylsiloxane), n =
13.5. Hydroxyethoxypropyl-terminated poly(dimethylsiloxane)
(Gelest, DMS-C15, Average MW (1H NMR): ca. 1246) (20.0 g,
16.05 mmol) was added to dry dichloromethane (80 mL)
together with succinic anhydride (3.885 g, 38.52 mmol) and
then triethylamine (3.90 g, 38.52 mmol, 5.36 mL). The mixture
was stirred at ambient temperature for 4 h and then at reflux for
a further 20 min, under nitrogen. Triethyleneglycol monomethyl
ether (1.1 mL) was added and the mixture was stirred at ambient
temperature for 1 h. The solvent was evaporated and the residue
was dissolved in diethyl ether/hexane (1:1), washed with 0.5 M
HCl, and dried with MgSO4. The solution was slowly passed
through a short silica gel column, further eluting with diethyl
ether. The solvent was evaporated in vacuo to give the pure
1
product as a clear viscous oil (23.2 g, yield: quantitative). H
NMR (400 MHz, CDCl3) δ 4.25 (t, J = 4.8 Hz, 4H, CH2-5), 3.63
(t, J = 4.8 Hz, 4H, CH2-4), 3.42 (t, J = 7.0 Hz, 4H, CH2-3), 2.67
(m, 8H, CH2-6,7), 1.61 (m, 4H, CH2-2), 0.52 (m, 4H, CH2-1),
0.04-0.08 (m, approximately 85H, SiCH3). Refer to the graphic
above for corresponding numbering system used in NMR
assignments.
Acid Chloride-Terminated Poly(dimethylsiloxane). Carboxy-
lic acid-terminated poly(dimethylsiloxane) (1.50 g, 1.04 mmol)
was added to anhydrous diethyl ether (10 mL) together with 1
small drop of DMF via syringe. Oxalyl chloride (0.53 g, 4.18
mmol, 0.36 mL) was added in one portion and the mixture was
stirred at ambient temperature, under nitrogen, for no longer
than 30 min. A slow nitrogen flow was maintained over the
reaction mixture by means of a syringe needle through a rubber
Telechelic Poly(dimethylsiloxane) Conjugated 60-Piperazine-
1,3,3-trimethylspiro[indoline-2,30-[3H] naphtho[2,1-b][1,4]-oxa-
zine], 4. Method B. 60-Piperazine-1,3,3-trimethylspiro[indoline-
2,30-[3H] naphtho[2,1-b][1,4]-oxazine]29 (0.25 g, 0.61 mmol) was
dissolved in anhydrous diethyl ether (ca. 20 mL), under nitrogen,
with triethylamine (0.25 mL). Acid chloride terminated poly-
(dimethylsiloxane) (0.446 g, 0.303 mmol) was then added drop-
wise and the mixture was stirred at room temperature for 1 h. The
whole reaction mixture was passed through a plug of silica gel,
eluting with diethyl ether and finally ethyl acetate. The solvent
was evaporated to give the pure product as a purple tar (0.60 g).
A sample of the material was then fractionated by column

Article
Macromolecules, Vol. 43, No. 20, 2010 8501
chromatography (silica gel, diethyl ether/hexane, 4:1). Average
molecular weights (Mn) were determined by H NMR analysis.
Nonfractionated product, 4: Mn=2286 (nPDMS=13.9). Fraction 1,
(7) Extrapolated from data contained in Eyeglasses - Global Strategic
Business Report; Global Industry Analysts, Inc.: San Jose, CA, March
2008.
(8) Such, G.; Evans, R.; Yee, L.; Davis, T. J. Macromol. Sci., C:
Polym. Rev. 2003, 43, 547–579.
(9) Krongauz, V. A. Environmental Effects on Organic Photochromic
Systems, 1st ed.; Elsevier: Amsterdam, 1990; Vol. 40, pp 793-821.
(10) Evans, R. A.; Hanley, T. L.; Skidmore, M. A.; Davis, T. P.; Such,
G. K.; Yee, L. H.; Ball, G. E.; Lewis, D. A. Nat. Mater. 2005, 4,
249–253.
(11) Such, G. K.; Evans, R. A.; Davis, T. P. Macromolecules 2006, 39,
1391–1396.
(12) Malic, N.; Campbell, J. A.; Evans, R. A. Macromolecules 2008, 41,
1206–1214.
(13) Ercole, F.; Malic, N.; Davis, T. P.; Evans, R. A. J. Mater. Chem.
1
4a: Mn=3164 (nPDMS=25.8). Fraction 2, 4b: Mn=2144 (nPDMS
=
12.0). Fraction 3, 4c: Mn=1772 (nPDMS=7.0). 1H NMR (nonfrac-
tionated material, 4; 400 MHz, acetone-d6) δ 8.59 (d, J = 8.3 Hz,
2H), 8.15 (d, J = 8.4 Hz, 2H), 7.71 (s, 2H), 7.57 (t, J = 7.3 Hz, 2H),
7.42 (t, J = 7.6 Hz, 2H), 7.18 (t, J = 7.7 Hz, 2H), 7.13 (d, J = 7.2
Hz, 2H), 6.86 (t, J = 7.4 Hz, 2H), 6.66 (s, 2H), 6.63 (d, J = 7.7 Hz,
2H), 4.16 (t, J = 4.8 Hz, 4H, CH2-5), 3.80 (s br, 8H, piperazine-H),
3.60 (t, J = 4.8 Hz, 4H, CH2-4), 3.43 (t, J = 6.7 Hz, 4H, CH2-3),
3.07 (d br, 8H, piperazine-H), 2.74 (s br, 6H, NCH3), 2.69 (t br, J =
6.3 Hz, 4H, CH2-7),2.60(tbr, J= 6.3 Hz, 4H, CH2-6), 1.61 (m, 4H,
CH2-2), 1.34 (2 ꢀ s overlap, 12H, spirooxazine geminal-CH3), 0.59
(m, 4H, CH2-1), 0.09-0.13 (m, approximately 88H, SiCH3) ppm.
Refer to graphic above for corresponding numbering system used
in NMR assignments.
2009, 19, 5612–5623.
(14) Evans, R. A.; Malic, N.; Campbell, J. A.; York, M. R.; Ali, A. S.
Photochromic polymer and composition comprising photochromic
polymer. WO 2009/146509 A1, 10 December 2009.
(15) Cypryk, M.; Rubinsztajn, S.; Chojnowski, J. J. Organomet. Chem.
1993, 446, 91–97.
Acknowledgment. We like to thank the CRC for Polymers,
Advanced Polymerik and CSIRO Molecular and Health Tech-
nologies for supporting this work.
(16) Pardo, R.; Zayat, M.; Levy, D. C. R. Chim. 2010, 13, 212–226.
ꢀ
(17) Sriprom, W.; Neel, M.; Gabbutt, C. D.; Heron, B. M.; Perrier, S.
J. Mater. Chem. 2007, 17, 1885.
(18) Moorthy, J. N.; Venkatakrishnan, P.; Samanta, S.; Kumar, D. K.
Org. Lett. 2007, 9, 919–922.
Supporting Information Available: Synthesis procedures for
photochromic dye starting materials and corresponding PDMS
(19) Berthet, J.; Coelho, P. J.; Carvalho, L. M.; Vermeersch, G.;
Delbaere, S. J. Photochem. Photobiol. A: Chem. 2009, 208, 180–185.
(20) Ercole, F.; Davis, T. P.; Evans, R. A. Macromolecules 2009, 42,
1500–1511.
(21) Such, G. K.; Evans, R. A.; Davis, T. P. Macromolecules 2004, 37,
9664–9666.
conjugates, characterization data, plots of fade speed (t1/2 and t3/4
)
versus chain length (nPDMS), kinetic plots (absorbance versus time),
absorbance spectra and figures relevant to text. This material is
available free of charge via the Internet at http://pubs.acs.org.
(22) Such, G.; Evans, R.; Davis, T. Mol. Cryst. Liq. Cryst. 2005, 430,
273–279.
(23) Ercole, F.; Malic, N.; Harrisson, S.; Davis, T. P.; Evans, R. A.
References and Notes
Macromolecules 2010, 43, 249–261.
(1) Jager, W. F.; van den Berg, O.; Picken, S. J. Macromol. Symp. 2005,
230, 11–19.
(24) Oliveira, M. M.; Salvador, M. A.; Delbaere, S.; Berthet, J.;
Vermeersch, G.; Micheau, J.; Coelho, P. J.; Carvalho, L. M.
J. Photochem. Photobiol. A: Chem. 2008, 198, 242–249.
(25) Coelho, P. J.; Carvalho, L. M.; Vermeersch, G.; Delbaere, S.
Tetrahedron 2009, 65, 5369–5376.
(26) di Nunzio, M. R.; Gentili, P. L.; Romani, A.; Favaro, G. Chem-
PhysChem 2008, 9, 768–775.
(27) Coelho, P.; Salvador, M.; Heron, B.; Carvalho, L. Tetrahedron
2005, 61, 11730–11743.
(2) Jansen, J. C.; Macchione, M.; Tocci, E.; De Lorenzo, L.; Yampolskii,
Y. P.; Sanfirova, O.; Shantarovich, V. P.; Heuchel, M.; Hofmann, D.;
Drioli, E. Macromolecules 2009, 42, 7589–7604.
(3) Photochromism: Molecules and Systems; Bouas-Laurent, H.; D€urr,
H., Eds.; Elsevier: Amsterdam, 1990.
(4) van Gemert, B. In Organic Photochromic and Thermochromic
Compounds; Crano, J.; Gugliemetti, R., Eds.; Plenum Press:
New York, 1998; Vol. 1, pp 111.
(28) Jockusch, S.; Turro, N. J.; Blackburn, F. R. J. Phys. Chem. A 2002,
106, 9236–9241.
(29) Yuan, W.; Sun, L.; Tang, H.; Wen, Y.; Jiang, G.; Huang, W.; Jiang,
(5) Lokshin, V.; Samat, A.; Metelitsa, A. V. Russ. Chem. Rev. 2002, 71,
893–916.
(6) Corns, S. N.; Partington, S. M.; Towns, A. D. Color. Technol. 2009,
125, 249–261.
L.; Song, Y.; Tian, H.; Zhu, D. Adv. Mater. 2005, 17, 156–160.