Note: Descriptions are shown in the official language in which they were submitted.
CA 02365814 2007-11-14
1
PHOTOLUMINESCENT MARKERS AND METHODS FOR DETECTION OF
SUCH MARKERS
FIELD OF INVENTION
This invention relates to photoluminescent chemical markers for tagging
liquids or
solids. More specifically, this invention relates to fluorene copolymer
markers.
BACKGROUND OF THE INVENTION
There is a strong drive for manufacturers and taxing authorities to tag
various
solid or liquid products with silent markers. Silent markers are invisible to
the
naked eye and yet identify the product when simple testing procedures are
used.
These silent markers when used in liquids are miscible with the liquid to be
tagged, are visually undetectable, should not affect the use and performance
of
the product and should be difficult to remove (e.g. by extraction, filtration,
bleaching, reactive conversion). These markers must be easily identifiable by
sampling and testing the product and, in some cases, quantifiable by the user.
These markers are commonly used to tag petroleum fuels in order to confirm
grade quality and taxation status. Markers are required by government
regulation
in order to police the tax classification of interchangeable fuels such as
diesel
fuel, farm equipment fuel and heating oil. Markers are also useful for
locating the
origin of leaks in storage tanks, lubrication systems, liquid handling
facilities, etc.
However, there is an increasing trend towards the use of markers in other
liquid
products including for example beverages such as soft drinks and alcohols,
foodstuffs, paints, cosmetics, refrigerants, lubricants, pharmaceuticals,
waxes,
varnishes, solvents, polymers, bulk chemicals and rubbers. For example, name
brand manufacturers of liquid products or those using inks to print brand name
labels will wish to tag products to confirm grade quality throughout their
distribution systems and to confirm origin of the product.
Furthermore, markers can also be introduced in solid during processing, in
melts,
castings or solid mixtures, or by coating or impregnating the solid with the
marker. For example, electronic products could be marked by coating their
outer
CA 02365814 2007-11-14
2
or inner surfaces. As a further example, markers, which are solid at room
temperature can be designed to melt at temperatures used for melting and
molding plastics so that the marker can be processed with the melt. Another
possibility is to provide the marker in a solution, introduce the solution in
a melt or
resin and evaporate the solvent so as to re-solidify the marker within the
targeted
product.
Thus, in general, markers will commonly be used to identify origin or grade of
a
given product. Silent markers will ideally be hard to remove or copy so as to
foil
attempts to remove or mimic the markers.
Although a number of photoluminescent markers are known, a main drawback is
their lack of sensitivity at low concentrations. Prior art markers are usually
deployed in liquids to be tagged in concentrations in the range of 1 to 100
ppm
(parts per million, volume per volume). These concentrations are often high
enough to negatively affect physical or chemical properties of the product to
be
tagged. For example, in the case of petroleum fuels, too much of a marker can
cause engine malfunctions and deposits.
Thus, there is a need for highly sensitive markers capable of effectively
tagging
solids or liquids at concentrations in the range of ppb (parts per billion),
which
may be readily identified and preferably even quantified. From a cost
standpoint,
it is also preferable to use less of the chemical marker.
Another drawback of current chemical photoluminescent markers is a limited
range of available solubility in different organic and inorganic liquids and a
limited
range of detectable photoluminescent responses.
Thus, there is a need for markers capable of solubilizing in many different
liquids.
There is also a need for markers capable or being easily designed so as to
provide an extended range of detectable photoluminescent responses.
Yet another drawback is the need for many of the existing silent markers to be
extracted by a wet chemical process. Typically, the chemical process includes
CA 02365814 2007-11-14
3
shaking a sample of the product with a water-based reagent such as described
in
U.S. Pat. Nos. 4,209,302, 4,735,631, 5,205,840 and 5,902,750. The addition of
a
chemical agent to the water phase causes the extract to turn to a visibly
distinct
color. The depth of the color indicates the quantity of marker present in the
sample. A laboratory measurement in a spectrometer indicates the concentration
of marker present in the isolated sample. Comparing the measured concentration
with the original concentration of marker in the fuel assists in the
identification of
the fuel. However, such technique involves disposal problems for the spent
sample and is generally burdensome because of the various steps that have to
be performed.
Also, some silent markers are large organic molecules that either absorb or
fluoresce in the near infrared to mark their presence in a fuel sample. U.S.
Pat.
Nos. 5,498,808, 5,980,593 and 5,525,516. In U.S. Pat. No. 5,498,808 and
5,980,593, the presence of such silent marker is detected by firstly
extracting the
marker with an aqueous reagent and then exposing the extract to UV light to
witness fluorescence. However, such multi-step procedure is generally
burdensome. In U.S. Pat. No. 5,525,516 (squaraines, phthalocyanines and
naphthalocyanines markers) and 5,984,983 (carbonyl markers) the presence of a
silent marker is detected by exposing the marker to near infrared radiation
and
then detecting emitted fluorescent light via a near infrared light detection
element.
Although meritorious, these efforts have not lead to silent markers being
sufficiently sensitive and versatile to properly function in various organic
environments. Solubility problems, detection problems and stability problems
are
often encountered.
Therefore, there remains a great need for a novel class of silent markers
which
do not require extraction before testing, which fluoresce under simple testing
conditions and at very low concentrations, which are soluble and non-reactive
in
a host of chosen liquids, preferably organic liquids, and which remain
sufficiently
stable over time whilst present in the organic liquid.
Preferably, the silent marker will be colorless or very lightly colored (will
not
fluorescence under normal lighting conditions). Also, the silent marker would
CA 02365814 2007-11-14
4
preferably be essentially insoluble in aqueous media (i.e. less than about 0.2
per
100mI at 20 C) so as to make its removal via extraction difficult. Still
preferably,
the marker should be combustible when used to tag combustible fuels.
The invention is next described in connection with certain embodiments;
however, it will be clear to those skilled in the art of petroleum product
marking
that various modifications, additions and subtractions can be made to the
described embodiments without departing from the spirit or scope of the
invention.
SUMMARY OF THE INVENTION
The invention provides fluorene-containing photoluminescent markers for
identification purposes and methods for detection of such photoluminescent
markers when present in organic liquid products or present in solid products.
These novel markers are described in more detail with reference to preferred
embodiments.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows the emission spectra of a copolymer of the present invention at
various concentrations when dissolved in gasoline;
Figure 2 shows the plot of concentration versus absorbance corresponding to
the
data of Figure 1;
Figure 3 shows the emission spectrum (corresponding to bright green visible
color) upon exposure to UV light of a polyethylene plastic bag when tagged
with a
fluorene copolymer of the present invention;
Figure 4 shows the absorption spectrum of the same tagged polyethylene plastic
bag which shows colorless under normal room light as indicated by a very low
absorption.
DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
This invention relates to photoluminescent markers for identification purposes
and methods for detection of such photoluminescent markers when present in
organic or inorganic liquid products or solid products.
CA 02365814 2007-11-14
When used herein, the expression "organic liquid products" is meant to
encompass non-aqueous liquid products containing essentially organic molecules
and blends thereof.
5 More specifically, this invention relates to fluorene copolymers as
photoluminescent markers, which are colorless to naked eyes and exhibit strong
photoluminescence between about 380-800 nm upon exposure to ultra-violet
radiation or laser light. The soluble fluorene copolymers described in this
invention having a general formula as shown in Formula 1.
M
In
Ri R2
Formula 1
Where:
= R, and R2 are C, - C24 linear or branched alkyl chain.
= n is the number of repeating unit.
= M is a co-monomer unit selected from the group consisting of:
R3
R3
R3 R4 R4 R4
CA 02365814 2007-11-14
6
R3 R3
R4 R4
R3
R4
R3
R3 R4
R4 R3 R4
R4
R3
R3 R4
S
R3 R4 0 0 Nz /N
S S s
CA 02365814 2007-11-14
7
R4
I
N
N N
R3 R3
R6 IR7
N
R5
R6 R7. R6 R7
N N
R5 R5
N N N
R3 R3 R3
N N
R3 R4 and
CA 02365814 2007-11-14
8
N N N
R3 R4 R5
Wherein:
= R3, R4 and R5 are hydrogen, C, - C12 linear or branched alkyl, alkylene,
alkyloxy, hydroxy alkyl, amino alkyl, cyanato alkyl, mercaptoalkyl, or
poly(oxyalkylene)ether; and
= R6 and R7 are each independently hydrogen, Cl-C12 linear or branched alkyl,
alkylene, alkyloxy, hydroxyl alkyl, amino alkyl, cyanato alkyl, mercaptoalkyl,
or
poly(oxyalkylene)ether with the proviso that at least one of R6 or R7 is not
hydrogen.
The terms "alkyl", "alkylene", "alkyloxy' refer to C, - C12 groups.
Each fluorene copolymer described in this invention exhibits unique absorption
and photoluminescent characteristics. These characteristics are key parameters
for detection methods of this invention. The fluorene copolymer also exhibit
solubility and melting points which can vary depending on the chosen R, and R2
groups in formula 1.
The following examples illustrate the syntheses of a wide variety of fluorene
copolymers, which are useful in the practice of this invention. All the
syntheses
were performed using a three-neck flask, which was equipped with magnetic
stirrers, heating mantle, temperature controller, water condenser and nitrogen
gas inlet. The products were characterized with spectrofluorometer (available
from Photon Technology International, Model QM2000), spectrometer (available
from Shimadzu, Model PC-1201), differential scanning calorimeter (Instrument
Specialties, Model DSC-500). The molecular weights of fluorene copolymers
were determined by gel permeable chromatography (available from Waters,
Model Breeze-System, equipped with 2410 reflective index detector). The
molecular weight of fluorene copolymers was evaluated using tetrahydrofuran as
eluent and polystyrene standards.
CA 02365814 2007-11-14
9
EXAMPLE 1
Synthesis of poly[2,7-(9,9-dihexyl)fluorene-co-2,7-(9,9-(di-5-
pentenyl)fluorene)]
Poly[2,7-(9,9-dihexyl)fluorene-co-2,7-(9,9-(di-5-pentenyl)fluorene)] was
obtained
by adding 0.54 mmol of 2,7-diborolane-9,9-dihexylfluorene (available from
American Dye Source, Inc., Baie D'Urfe, Quebec, Canada), 0.54 mmol of 2,7-
dibromo-9,9-di(5-pentenyl)fluorene (available from American Dye Source, Inc.,
Baie D'Urfe, Quebec, Canada), 0.28 grams of triphenylphosphine (available from
Sigma-Adrich, Oakville, Ontario, Canada ) and 0.056 grams of palladium (II)
diacetate (available from Sigma-Adrich, Oakville, Ontario, Canada) into 50 ml
of
freshly distilled tetrahydrofuran. The mixture was stirred at room temperature
for
min. A solution containing 2 molar of potassium carbonate (15 ml) was added
to the reaction flask and the mixture was heated to reflux for 18 hours. The
reaction mixture was then extracted with toluene. The organic phase was washed
15 with brine three time and dried over sodium sulfate. Removal of solvent
gave a
dark green gum. The crude product was purified by dissolution into 50 ml of
toluene solution containing 1.0 gram of silica gel (flash grade), 1.0 gram of
neutral aluminum oxide and 1.0 gram of potassium cyanide. The mixture was
stirred for 72 h. and the solid metal oxide particles were then removed by
vacuum
filtration. The filtrate was then removed by using a vacuum evaporator until
dryness. The solid polymer product was dissolved in 3 ml of dichloromethane
and
then precipitated in 75 ml of acetone. A light beige polymeric powder was
obtained by filtration and drying in a vacuum oven with 68 % yield. The
molecular
weight of the obtained polymer was determined to be 15,000 versus polystyrene
standards. The structure of Poly[2,7-(9,9-dihexyl)fluorene-co-2,7-(9,9-(di-5-
pentenyl)-fluorene)] is shown as the following.
n
H12C6 C6H12
CA 02365814 2007-11-14
EXAMPLE 2
Synthesis of poly[(2,7-{9,9-dihexylfluorene})-co-(1,4-benzene)]
5 The synthesis of poly[(2,7-{9,9-dihexylfluorene})-co-(1,4-benzene)] was
performed similarly to that of example 1, excepted that 1,4-dibromobenzene
(available from Sigma-Aldrich, Oakville, Ontario, Canada) was used to replace
2,7-dibromo-9,9-di(5-pentenyl)fluorene. A white polymeric powder was obtained
with 22 % yield. The molecular weight of the obtained polymer was determined
to
10 be 10,000 versus polystyrene standards. The structure of poly[(2,7-{9,9-
dihexylfluorene})-co-(1,4-benzene)] is shown as the following.
n
H13C6 C6H13
EXAMPLE 3
Synthesis of poly[(2,7-{9,9-dihexylfluorene})-co-(1,4-{2,5-dimethyl}-benzene)]
The synthesis of poly[(2,7-{9,9-dihexylfluorene})-co-(1,4-{2,5-dimethyl}-
benzene)]
was performed similarly to that of example 1, excepted that 2,5-dibromo-p-
xylene
(available from Sigma-Aldrich, Oakville, Ontario, Canada) was used to replace
2,7-dibromo-9,9-di(5-pentenyl)fluorene. A white polymeric powder was obtained
with 22 % yield. The molecular weight of the obtained polymer was determined
to
be 9,000 versus polystyrene standards. The structure of poly[(2,7-{9,9-
dihexylfluorene})-co-(1,4-{2,5-dimethyl}-benzene)] is shown as the following.
H3C
n
CH3
H13C6 C6H13
CA 02365814 2007-11-14
11
EXAMPLE 4
Synthesis of poly[(2,7-{9,9-dihexyl}-fluorene)-co-(4,4'-biphenyl)]
The synthesis of poly[(2,7-{9,9-dihexylfluorene})-co-(4,4'-{1,1'-biphenyl})]
was
performed similarly to that of example 1, excepted that 4,4'-dibromo-1,1'-
biphenyl
(available from Sigma-Aldrich, Oakville, Ontario, Canada) was used to replace
2,7-dibromo-9,9-di(5-pentenyl)fluorene. A white polymeric powder was obtained
with 70 % yield. The molecular weight of the obtained polymer was determined
to
be 6,000 versus polystyrene standards. The structure of poly[(2,7-{9,9-
dihexyl}-
fluorene)-co-(4,4'-biphenyl)] is shown as the following.
n
H13C6 C6H13
EXAMPLE 5
Synthesis of poly[(2,7-{9,9-dihexyl}-fluorene)-co-(9,10-anthracene)]
The synthesis of poly[(2,7-{9,9-dihexyl}-fluorene)-co-(9,10-anthracene)] was
performed similarly to that of example 1, excepted that 9,10-dibromoanthracene
(available from Sigma-Aldrich, Oakville, Ontario, Canada) was used to replace
2,7-dibromo-9,9-di(5-pentenyl)fluorene. A light yellow polymeric powder was
obtained with 20 % yield. The molecular weight of the obtained polymer was
determined to be 4,000 versus polystyrene standards. The structure of
poly[(2,7-
{9,9-dihexyl}-fluorene)-co-(9,10-anthracene)] is shown as the following.
CA 02365814 2007-11-14
12
n
H ~'6 H
13C6 13
EXAMPLE 6
Synthesis of poly[(2,7-{9,9-dihexylfluorene})-co-(1,4-benzo-{2,1',3}-
thiadiazole)]
The synthesis of poly[(2,7-{9,9-dihexyl}-fluorene)-co-(1,4-benzo-{2,1',3}-
thiadiazole)] was performed similarly to that of example 1, excepted that 1,4-
dibromo-[2,1',3]-thiadiazole (available from American Dye Source, Inc., Baie
D'Urfe, Quebec, Canada) was used to replace 2,7-dibromo-9,9-di(5-
pentenyl)fluorene. A light yellow polymeric powder was obtained with 60 %
yield.
The molecular weight of the obtained polymer was determined to be 10,000
versus polystyrene standards. The structure of poly[(2,7-{9,9-dihexyl}-
fluorene)-
co-(1,4-benzo-{2,1',3}-thiadiazole)] is shown as the following.
N~S~N
ic
H13C6 C6H13
EXAMPLE 7
Synthesis of poly[2,7-(9,9-{dihexylfluorene})-co-({9-ethyl}-3,6-carbazole)]
The synthesis of poly[2,7-(9,9-{dihexylfluorene})-co-({9-ethyl}-3,6-
carbazole)] was
performed similarly to that of example 1, excepted that 9-ethyl-3,6-
dibromocarbazole (available from American Dye Source, Inc., Baie D'Urfe,
Quebec, Canada) was used to replace 2,7-dibromo-9,9-di(5-pentenyl)fiuorene. A
CA 02365814 2007-11-14
13
light yellow polymeric powder was obtained with 60 % yield. The molecular
weight of the obtained polymer was determined to be 10,000 versus polystyrene
standards. The structure poly[2,7-(9,9-{dihexylfluorene})-co-(3,6-{9-ethyl}-
carbazole)] is shown as the following.
N n
H13C6 C61-113 C21"15
EXAMPLE 8
Synthesis of poly[2,7-(9,9-{dihexylfluorene})-co-(3,5-pyridine)]
The synthesis of poly[2,7-(9,9-{dihexylfluorene})-co-(3,5-pyridine)] was
performed
similarly to that of example 1, excepted that 3,5-dibromopyridine (available
from
Sigma-Aldrich, Oakville, Ontario, Canada) was used to replace 2,7-dibromo-9,9-
di(5-pentenyl)fluorene. A white polymeric powder was obtained with 30 % yield.
The molecular weight of the obtained polymer was determined to be 7,000 versus
polystyrene standards. The structure poly[2,7-(9,9-{dihexylfluorene})-co-(3,5-
pyridine)] is shown as the following.
N
\
n
H13C6 C6H13
EXAMPLE 9
Synthesis of poly[2,7-(9,9-{dihexyl}-fluorene)-co-(N,N'-di{phenyl}-N,N'-di{p-
butylphenyl}-1,4-diaminobenzene)]
CA 02365814 2007-11-14
14
The synthesis of poly[2,7-(9,9-{dihexyl}-fluorene)-co-(N,N'-di{phenyl}-N,N'-
di{p-
butylphenyl}-1,4-diaminobenzene)] was performed similarly to that of example
1,
excepted that N,N'-di(p-bromophenyl)-N,N'-di(p-butylphenyl)-1,4-diaminobenzene
(available from American Dye Source, Inc., Baie D'Urfe, Quebec, Canada) was
used to replace 2,7-dibromo-9,9-di(5-pentenyl)fluorene. A beige polymeric
powder was obtained with 30 % yield. The molecular weight of the obtained
polymer was determined to be 6,000 versus polystyrene standards. The structure
poly[2, 7-(9,9-{di hexyl}-fl uorene)-co-( N, N'-di{phenyl}-N, N'-di{p-
butylphenyl}-1,4-
diaminobenzene)] is shown as the following.
n
' '13C6 CA 3 \ I ~ I
EXAMPLE 10
Synthesis of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-vinylenephenylene)]
The synthesis of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-
vinylenephenylene)]
was performed by dropwise adding tri-n-ethyllamine (7.0 ml) into 100 ml N,N-
dimethylformamide solution containing 1.3 gram of p-divinylbenzene (available
from Sigma-Aldrich, Oakville, Ontario, Canada), 5.5 gram of 2,7-dibromo-9,9-
dioctylfluorene (available from American Dye Source, Inc., Baie D'Urfe,
Quebec,
Canada), 0.1 gram of palladium (II) acetate (available from Sigma-Aldrich,
Oakville, Ontario, Canada) and 0.63 gram of tri-o-tolylphosphine (available
from
Sigma-Aldrich, Oakville, Ontario, Canada). The reaction mixture was stirred at
100 C for 24 hours under nitrogen atmosphere. The reaction mixture was cooled
to room temperature and pour into 2 liter of methanol. The precipitate polymer
was collected by filtration. The polymer was further purified by precipitated
into 2
liter of acetone from tetrahydrofuran solution. A light yellow power polymer
was
obtained with 62 % yield after filtration and dried in air. The molecular
weight of
the obtained polymer was determined to be 20,000 versus polystyrene standards.
The structure of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-
vinylenephenylene)] is
shown as the following:
CA 02365814 2007-11-14
n
5 HIA C8H17
EXAMPLE 11
Synthesis of poly[(9,9-d ioctylfl uorenyl-2,7-d iyl)-co-(ethylenyl benzene)]
10 The synthesis of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-
(ethylenylbenzene)] was
performed by adding 20 ml triethylamine into 100 ml toluene solution
containing
1.4 gram of 1,4-diethynylbenzene (available from TCI, Portland, Oregon), 5.5
gram of 2,7-dibromo-9,9-dioctylfluorene, 0.4 gram of bistriphenylphosphine
palladium dichloride, 1.0 gram of copper (I) iodide and 0.3 gram
15 triphenylphosphine in a Schlenk tube under nitrogen atmosphere. The mixture
was heated at 70 - 80 C for 24 hours. The reaction mixture was cooled to room
temperature and poured into 2 liter of methanol. The precipitated polymer was
collected by filtration and washed copiously with methanol. The precipitate
polymer was collected by filtration. The polymer was further purified by
precipitation into 2 liter of acetone from tetrahydrofuran solution. A light
yellow
fiber product was obtained with 54 % yield after filtration and dried in air.
The
molecular weight of the obtained polymer was determined to be 10,000 versus
polystyrene standards. The structure of poly[(9,9-dioctylfluorenyl-2,7-diyl)-
co-
(ethylenylbenzene)] is shown as the following:
n
H17C8 C8H17
CA 02365814 2007-11-14
16
Method of use
STATEMENT OF CLAIMS
The present invention also relates to a method of tagging bulk liquid organic
products. This method comprises the. steps of (a) dissolving in a given amount
of
the bulk liquid organic product a known amount of at least one fluorene
copolymer
of the invention so as to achieve known concentrations of fluorene copolymers
in
the bulk liquid organic product and (b) recording the identity of the at least
one
fluorene copolymers and their corresponding known concentrations for eventual
testing to insure that the bulk liquid organic product remains unadulterated.
Also the present invention relates to a method of identifying the contents of
a bulk
liquid organic product. This method comprises the steps of (a) tagging the
bulk
organic product with a marker comprising at least one fluorene copolymer of
the
invention, wherein the fluorene copolymer is soluble in the liquid organic
product;
(b) subjecting a portion of the bulk liquid organic product to ultraviolet
radiation or
laser light at wavelengths between about 200 and 500 nm; (c) collecting
emitted
spectrum of the portion of liquid of step (b) with a photometer; (d) comparing
the
spectrum to a library of known spectra of tagging markers so as to obtain a
most
probable match thereby establishing the identity of the marker; and (e)
comparing
the marker to a library of bulk liquid organic product markers linked to
specific bulk
liquid organic products thereby establishing the identity of the bulk organic
liquid
being tested.
This invention also relates to a method of tagging solid products comprising
the
steps of: (a) mixing a known amount of at least one fluorene copolymer of the
invention with a solid so as to achieve known concentrations of fluorene
copolymers in the solid; and (b) recording the identity of the at least one
fluorene
copolymers and their corresponding known concentrations for eventual testing
to
insure that the solid remains unadulterated.
More specifically, in this method, the solid being tagged may be a bulk
material
and the mixing step (a) may be effected by solid state blending of a solid
copolymer of the invention and the solid being tagged. Alternatively, in this
method, the solid being tagged may be a polymeric material and the mixing step
CA 02365814 2007-11-14
17
(a) may be effected by melt mixing of a melt of a copolymer of the invention
and a
melt of the polymeric material which will yield the polymeric solid upon
eventual
cooling.
Also, in this method, the solid being tagged is a polymeric material and the
mixing
step (a) may be effected by melt mixing by dissolving a copolymer of the
invention
in a suitable solvent and introducing the dissolved copolymer in a melt of the
polymeric material which will yield the polymeric solid upon eventual cooling.
This invention also relates to a method of tagging solid products comprising
the
steps of: (a) dissolving a known amount of at least one fluorene copolymer of
the
invention in a suitable solvent so as to obtain a tagged solvent; (b) applying
the
tagged solvent to the solid product so as to tag the solid product; and (c)
recording
the identity of the at least one fluorene copolymers and their corresponding
known
concentrations for eventual testing to insure that the bulk liquid organic
product
remains unadulterated.
This invention also relates to a method of identifying the contents of a solid
product. This method comprises the steps of : (a) tagging the solid product
with a
marker comprising at least one fluorene copolymer of the invention; (b)
subjecting
a portion of the tagged solid to ultraviolet radiation or laser light at
wavelengths
between about 200 and 500 nm; (c) collecting emitted spectrum of the portion
of
liquid of step (b) with a photometer; (d) comparing the spectrum to a library
of
known spectra of tagging markers so as to obtain a most probable match thereby
establishing the identity of the marker; and (e) comparing the marker to a
library of
bulk liquid organic product markers linked to specific solids thereby
establishing
the identity or origin of the solid product being tested.
More specifically, the present invention provides a method for marking various
organic liquid products for subsequent identification purposes. The markers of
the
present invention are fluorene copolymers, which are used to tag or mark
chosen
organic liquids. When samples of a tagged product are exposed to UV radiation
or
laser light, i.e. at the wavelength between about 200 to 500 nm, preferably
325 to
400 nm. A photodetector can be used to measure the spectral pattern of
CA 02365814 2007-11-14
18
fluorescent emissions (emission vs. wavelength). The fluorescence and its
color
will become immediately visible to the naked eye and will constitute a first
indication of the presence of the marker. Also, a spectrofluorometer can be
used
to measure the concentration of the fluorescence emitting substance upon
comparison with a standard calibration curve.
Furthermore, the spectral pattem collected by the spectrofluorometer, in
particular the maximum emission peak, will indicate of the exact marker used
when the pattern is compared to a database of known spectral patterns. This is
done by standard algorithms present in commercial available photodetection
equipment known to those of skill in the art.
The absorbance reading obtained by photodetector readings will indicate the
concentration of marker in a given sample. This will in turn immediately
reveal if
the sample was tampered with, blended, diluted, etc. Indeed, the concentration
can be compared to an expected value. If the concentration differs from the
expected value by a predetermined margin, the person testing the sample will
immediately know that the organic liquid was tampered with. For example, if
two
grades of fuel have been blended in an effort to pass off the blend as a
higher
grade fuel, a photodetector reading of a blend sample will reveal the presence
of
both individual markers for each fuel grade and moreover will show both
individual markers in concentrations lower than expected. This will
immediately
alert the tester and reveal exactly which fuel grades were blended and in
approximately what ratio.
Because the markers of the present invention exhibit distinct spectral
signatures,
a plurality of markers may be used at the same time in a given organic liquid.
For
example, multiple markers could be used to indicate source of manufacture,
approximate date of manufacture, grade, etc. To indicate a date of
manufacture,
for example on a month-to-month basis, twelve distinct markers could be used
on
a rotational basis.
As shown in Table 1, the various example compounds 1 through 11 of the
present invention were individually used to tag kerosene. All compounds were
CA 02365814 2007-11-14
19
placed in concentrations of about 100 ppb in Cyclosol-53 T"", available from
Shell
Canada Inc. Samples of each tagged kerosene fluids were first subjected to a
spectrophotometer reading to obtain their absorption spectral signature. The
wavelengths corresponding to the main peaks absorption peaks are listed in the
second column. Each sample was then subjected to UV radiation by exposure
to light generated by solid-state lasers (preferably 325 to 400nm, the
particular
choice of laser is not crucial, for example He-Cd, Ag, GaN or other lasers are
suitable). All of the samples had visually detectable fluorescence. The
samples
were subjected to a second spectrophotometer reading to obtain their
fluorescence spectral signature. The wavelengths corresponding to the main
absorption peaks are listed in Table 1. In a separate column, the Stoke shift
or
variation in the wavelength of the main absorption peaks for each sample is
also
provided. The Stoke shift is clearly large enough to readily allow detection
of
fluorescence. Upon standing for several weeks none of the fluorene copolymer
compounds of the present invention had settled or crystallized.
It is to be understood that among the various fluorene copolymers of the
present
invention, these will be selected to avoid overlap in the fluorescence
wavelengths
of the main peaks of the organic substance being tagged.
TABLE 1
Absorption and photoluminescent wavelengths and colors of fluorene copolymers
in Cyclosol-53 (trademark of Kerosene product, available from Shell Canada
Inc.)
Absorption Photoluminescence Stoke Shift
Examples
k (nm) Color ~ (nm) Color A), (nm)
1 385 Colorless 418 Blue 33
2 371 Colorless 407 Violet-Blue 36
3 324 Colorless 380 Violet-Blue 56
4 363 Colorless 405 Violet-Blue 42
CA 02365814 2007-11-14
Absorption Photoluminescence Stoke Shift
Examples
X (nm) Color X (nm) Color Ak (nm)
5 400 Colorless 434 Blue 34
6 440 Light Yellow 521 Green-Yellow 81
7 347 Colorless 372 Violet-Blue 25
8 337 Colorless 369 Violet 32
9 362 Light Yellow 461 Green 99
10 401 Light Yellow 450 Green 49
11 374 Colorless 411 Blue 37
Evidence of photoluminescence at low concentrations
Referring now to Figures 1 and 2, evidence of photoluminescence at very low
concentration is demonstrated. The compound of example 1, namely, poly[2,7-
5 (9,9-dihexyl)fluorene-co-2,7-(9,9-(di-5-pentenyl)fluorene)] was placed in
samples
of Cyclosol-53 T"" at various concentrations, namely 12, 50 and 100 ppb (parts
per
billion, vol/vol basis). Even at these very low concentrations, the
fluorescent
intensity of these samples was clearly detectable as shown on Figure 1. As can
be seen from Figure 2, the emission, measured in counts on the vertical axis
of
10 Figures 1 and 2 can be used to plot the concentration of the marker against
a
given standard calibration curve. It is to be understood that each fluorene
copolymer compound of the present invention will exhibit particular
fluorescent
variation with varying concentration.
15 The fluorene copolymers of this invention can be used to tag solid products
such
as sheets, tubing, containers, packaging boxes, bag, coatings and others,
which
are made from plastics, polymeric composites, wax, and paper. For example,
poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-vinylenephenylene)], which was
obtained from Example 10, was incorporated into high density polyethylene and
20 extruded at 160 C to produce polyethylene plastic bag. Upon exposure to UV
light, the tagged polyethylene emits intensive green light. Upon exposure to
violet
CA 02365814 2007-11-14
21
laser light at 410 nm wavelength, the tagged polyethylene film also emits
green
light having a maximum at 460 nm as shown in Figure 3.
On the other hand, the same tagged polyethylene plastic bag shows colorless
under normal room light as indicated by a very low absorption in the UV-Vis-
NIR
spectrum as shown in Figure 4.
Incorporating the fluorene copolymers of the present invention into polymeric
solids can be performed by various methods such as melt mixing, dissolution in
a
solvent and subsequent mixing with the polymer melt, solid-solid mixing,
dissolution in monomeric liquid prior to polymerization. It is to be
understood that
in the case of melt mixing, the R, and R2 groups of the fluorene polymer of
the
present invention may be chosen so as to impart a melting point to the
fluorene
polymer which is compatible with the melt processing temperatures of the
polymer into which the fluorene polymer is mixed.
The fluorene polymers of the present invention can also be incorporated onto
or
into various solids by coating, printing, prickling, impregnation, solid-solid
mixing,
etc.
