Title of Invention	"A PROCESS FOR THE PREPARATION OF DOPED POLYAHILINE THERMALLY STABLE UPTO 310 C."
Abstract	A process for the preparation of doped polyaniline thermally stable upto 310°C which comprises adding 0.1 moles of aniline to an aqueous solution of organic protonic acid such as herein described, in the range of 1.0 to 3.0 molar at a temperature in the range of -5°C to 10°C, adding aqueous solution of 0.1 to 0.5 moles of oxidant such as herein described, under stirring for a period in the range 1 hour to 6 hours, followed by filtration and washing with distilled water, treating with aqueous mild base such as herein described, filtering, followed by washing with distilled water and methanol and drying by conventional methods, mixing the resultant mass with organic protonic acid at the temperature in the range of 0 - 5°C to obtain thermally stable conducting polyaniline.

Title of Invention

"A PROCESS FOR THE PREPARATION OF DOPED POLYAHILINE THERMALLY STABLE UPTO 310 C."

Abstract

A process for the preparation of doped polyaniline thermally stable upto 310°C which comprises adding 0.1 moles of aniline to an aqueous solution of organic protonic acid such as herein described, in the range of 1.0 to 3.0 molar at a temperature in the range of -5°C to 10°C, adding aqueous solution of 0.1 to 0.5 moles of oxidant such as herein described, under stirring for a period in the range 1 hour to 6 hours, followed by filtration and washing with distilled water, treating with aqueous mild base such as herein described, filtering, followed by washing with distilled water and methanol and drying by conventional methods, mixing the resultant mass with organic protonic acid at the temperature in the range of 0 - 5°C to obtain thermally stable conducting polyaniline.

Full Text	This invention relates to a process for the preparation of thermally stable electrically conducting doped polyaniline useful for antistatic and electromagnetic interference applications. The process of the present invention particularly provides a conducting polymer polyaniline which is thermally stable upto o 310 C, which can find various applications as an display device, in the shielding of electromagnetic interference (EMI) by blending with certain insulating polymers like polyvinylchloride (PVC), polymethamethylacrylate (PMMA), polyethylene (PE), polystyrene (PS) and the like and for the dissipation of electrostatic charge (ESD). The process involves chemical polymerization of aniline in the presence of substituted oxinate sulphonic acids (SOSA) and the like using an oxidant ammonium peroxydisul- phate at 0-5oC. There has recently been an increased interest in conducting polymer polyaniline, which has been studied extensively because of its unique electrochemical behaviour and environmental stability. Kobayashi et.al. in "Electrochemical reactions concerned with electrochromism of polyaniline coated electrodes", J. Elec-troanal. Chem. 177 (1984) 281-91, describes various experiments in which spectroelectrochemical measurement of a polyaniline film electrode were made. Yong Cao et.al. in "Influence of chemical polymerization conditions on the properties of polyaniline", Polymer, 30 (1989) 2305-11, describes the oxidative polymerization of aniline as a function of wide variety of synthesis conditions like different oxidizing agents and different inorganic acids. Genies et.al. in "Polyaniline - a historical survey", Synth. Metals, 36 (1990) 139-82 describes a detailed study on the electrochemical and chemical polymerization, redox mechanism and electrochemical properties of polyaniline. F.Lux in "Properties of electronically conducting polyaniline: a comparison between literature and experimental findings", Polymer, 35 (1994) 2915-22 deals with the synthesis and properties of polyaniline. U.S. Patent No. 3,963,498; 4,025,463 and 5,069,820 describes oligomeric polyanilines which are described as being soluble in certain solvent and thermally stable form of polyaniline in the presence of inorganic dopant. Hitherto preparation of conducting polyaniline is presently carried out in the presence of inorganic acids like hydrochloric, sulphuric and perchloric acid and organic acids like benzene sulphonic acid (BSA), p-toluene sulphonic acid (PTSA), sulphamic acid (SA), 5-sulphosalicyclic acid (SSA) and the like. However the doped form of conducting polyaniline is stable upto 140-150oC in case of inorganic acid dopants and upto 240oC in case of BSA, PTSA, SSA. U.S. Patent No. 5,208,301 describes the sulphonic acid substituted polyaniline for its possible use either reversible or irreversible NH3 filter, sensor, temperature indicator and the like. Japanese Patent No. 1999434, 870810 describes the use of poly (vinyl sulphonic acid) doped polyaniline as a battery electrode. Indian Patent Nos. 1200-1202/Del/90 describes processes for the preparation of polyaniline, composites and polyaniline grafted on insulating surfaces. Y.Wei et.al. in "Thermal analysis of chemically synthesized polyaniline and effects of thermal aging on conductivity", J. Polymer Science: Part A: Polymer Chemistry, 27 (1989) 4351-63 has investigated the thermal stability of polyaniline doped with inorganic pro-tonic acid dopants. V.G.Kulkarni et.al. in "Thermal stability of polyaniline", Synthetic Metals, 30 (1989) 321-325; 41-43 (1991) 1009-12 gives a thermal stability data of polyaniline doped with counter inorganic and organic anions. Wang et.al. in "Thermal behavior of intrinsic polyaniline and its derivatives, Synth. Metals, 69 (1995) 263; ibid. 163-164 gives an account of the thermal properties of polyaniline, polytoluidine and polyanisi-dine by TGA and DSC techniques. The main objective of the present invention is to provide a process for the preparation of thermally stable doped polyaniline which yields a conducting polymer which is thermally stable upto 310oC which can find its applications in the formation of conducting composites by blending with conventional polymers. In the drawings accompanying this specification Figure 1 is a graph showing % weight loss as a function of temperature for polyaniline doped with PTSA. (p-toluene sulphor-ic acid) Figure 2 is a graph showing % weight loss as a function of temperature for polyaniline doped with SOSA. (substituted oxanic sulphoric acid ) Figure 3 is a graph showing % weight loss as a function of temperature for emeraldine base form of polyaniline. Accordingly the present invention provides a process for the preparation of doped polyaniline thermally stable upto 310°C which comprises adding 0.1 moles of aniline to an aqueous solution of organic protonic acid such as herein described, in the range of 1.0 to 3.0 molar at a temperature in the range of -5°C to 10°C, adding aqueous solution of 0.1 to 0.5 moles of oxidant such as herein described, under stirring for a period in the range 1 hour to 6 hours, followed by filtration and washing with distilled water, treating with aqueous mild base such as herein described, filtering, followed by washing with distilled water and methanol and drying by conventional methods, mixing the resultant mass with organic protonic acid at the temperature in the range of 0 - 5°C to obtain thermally stable conducting polyaniline. The temperature of the reaction mixture may be in the rqnge of 0 - 5°C. The aqueous ammonia used may be of strength in the mage of 0.5 M to 1.0 M. The conducting polyaniline doped with substituted aromatic oxinate sulphonic acid shows a two step decomposition. The first step corresponds to the loss of counter anion and the seciond step corresponds to the decomposition of the polymer backbone. The doping level of the doped polymer can be estimated from the weight loss in the first step of the doped polymer. In substituted oxinate sulphonate doped polyaniline, the weight loss begins at 310°C and continues upto 380°C. The weight loss is 50 % corre- sponding to the weight of the dopant. This shows that the thermal stability of the doped polyaniline depends upon the SOSA dopant attached to the polymer backbone which probably prevents the decomposition of the polymer likely due to the electron withdrawing properties of sulphonate dopant. The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention. Example 1 Preparation of thermally stable conducting polyaniline containing substituted oxinate sulphonate anion as dopant To 1.0 M of substituted oxinate sulphonic acid in 100 ml. of o water was added 0.1 M of aniline. To this solution at 0 C was then added slowly 0.1 M aqueous solution of ammonium peroxydisul-phate. After stirring for 4 hours, green precipitate was filtered, washed thoroughly with water and then with methanol and diethylether. Dull green precipitate cake was then dried under vacuum. Thermogravimetric analysis under nitrogen of the material o polyaniline shows only a negligible weight loss upto 310 C and o from 310 C major weight loss begins corresponding to the weight of the dopant. Example 2 Preparation of substituted-oxinate sulphonate doped polyaniline by treatment of emeraldine base form of polyaniline with SOSA To 100 ml. of 1.0 M substituted-SOSA in water was added 1.0 gram of emeraldine base form of polyaniline. The solution was then stirred for 3-4 hours at room temperature, filtered, washed with SOSA and dried in vacuum at 50oC. Thermogravimetric analysis of this material showed similar weight loss behaviour to that of material prepared as in example 1. Example 3 Preparation of polyaniline doped with p-toluenesulphonic acid To 1.0 M of p-toluene sulphonic acid in 100 ml. of water was added 0.1 M of aniline. To this solution at 0oC was then added slowly 0.1 M aqueous solution of ammonium peroxydisulphate. After stirring for 4 hours, green precipitate was filtered, washed thoroughly with water and then with methanol and diethylether. Green precipitate cake so obtained was then dried under vacuum. Thermogravimetric analysis under nitrogen of the material polya- niline shows only a negligible weight loss upto 240oC and from 240oC major weight loss begins corresponding to the weight of the dopant. Thermogravimetric analysis of polyaniline doped with p-toluene sulphonate and substituted-oxinate sulphonate: Brief Description of the Drawings: In the drawings Figure 1 is a graph showing % weight loss as a function of temperature for polyaniline doped with PTSA. Figure 2 is a graph showing % weight loss as a function of temperature for polyaniline doped with SOSA. Figure 3 is a graph showing % weight loss as a function of temperature for emeraldine base form of polyaniline. An experiment was carried out to compare the thermal stability of thermally stable polyaniline of this invention and conventional doped polyaniline. The polyaniline of this invention was doped with SOSA and was prepared as described in example 1. The conventional polyaniline was doped with p-toluene sulphonic acid and was prepared as in example 3. Samples of polyaniline doped with p-toluene sulphonate and polyaniline doped with SOSA were analyzed by Thermogravimetric analysis (TGA) under nitrogen to determine their stability to weight loss (dopant ion). The results of this experiment are set forths in Figures 1 & 2 of the drawings accompanying this specification. At a 20oC/minute heating rate, sample of polyaniline doped with PTS exhibited two weight loss steps. One between 50 and 100oC (9% weight loss) and other between 234 -338oC corresponding to dopant loss (45 % weight loss) (as shown in Fig. 1 of the drawing). Subjecting a sample of polyaniline doped with substituted oxine sulphonate to the same analysis shows that initial weight loss of approximately 8-9% corresponds to the weight of the water present in the polymeric material and from 310 C to 380 C weight loss occurs corresponding to the weight of the dopant (as shown in Figure 2 of the drawing). Thus polyaniline doped with SOSA is much more thermally stable to the dopant loss than polyaniline doped with PTSA. However the undoped form of polyaniline is thermally stable upto 43 4oC (as shown in Figure 3 of the drawing) . Because of high thermal stability of polyaniline of this invention, this material is useful as an additive in melt processing with many conventional polymers such as. poly vinylchloride, polymethamethylacrylate, polyethylene, polyproplene and the like. The thermal stability also allows the melt processing of the conducting polymer of this invention. We Claim: 1. A process for the preparation of doped polyaniline thermally stable upto 310°C which comprises adding 0.1 moles of aniline to an aqueous solution of organic protonic acid such as herein described, in the range of 1.0 to 3.0 molar at a temperature in the range of -5°C to 10°C, adding aqueous solution of 0.1 to 0.5 moles of oxidant such as herein described, under stirring for a period in the range 1 hour to 6 hours, followed by filtration and washing with distilled water, treating with aqueous mild base such as herein described, filtering, followed by washing with distilled water and methanol and drying by conventional methods, mixing the resultant mass with organic protonic acid at the temperature in the range of 0 - 5°C to obtain thermally stable conducting polyaniline. 2. A process as claimed in claim 1 wherein the organic protonic acid used is substituted oxinate sulphoric acid. 3. A process as claimed in claims 1-2 wherein oxidant used is ammonium peroxydisulphate, potassium peroxydisulphate, sodium peroxydisulphate, potassium dichlronate. 4. A process as claimed in claims 1 to 3 wherein the mild base used is aq. ammonia. 5. A process for preparation of doped polyaniline thermally stable upto 310°C substantially as herein described with reference to examples.

Full Text

This invention relates to a process for the preparation of thermally stable electrically conducting doped polyaniline useful for antistatic and electromagnetic interference applications. The process of the present invention particularly provides a
conducting polymer polyaniline which is thermally stable upto
o 310 C, which can find various applications as an display device, in the shielding of electromagnetic interference (EMI) by blending with certain insulating polymers like polyvinylchloride (PVC), polymethamethylacrylate (PMMA), polyethylene (PE), polystyrene (PS) and the like and for the dissipation of electrostatic charge (ESD). The process involves chemical polymerization of aniline in the presence of substituted oxinate sulphonic
acids (SOSA) and the like using an oxidant ammonium peroxydisul-
phate at 0-5oC.
There has recently been an increased interest in conducting polymer polyaniline, which has been studied extensively because of its unique electrochemical behaviour and environmental stability. Kobayashi et.al. in "Electrochemical reactions concerned with electrochromism of polyaniline coated electrodes", J. Elec-troanal. Chem. 177 (1984) 281-91, describes various experiments in which spectroelectrochemical measurement of a polyaniline film electrode were made. Yong Cao et.al. in "Influence of chemical polymerization conditions on the properties of polyaniline", Polymer, 30 (1989) 2305-11, describes the oxidative polymerization of aniline as a function of wide variety of synthesis conditions like different oxidizing agents and different inorganic
acids. Genies et.al. in "Polyaniline - a historical survey", Synth. Metals, 36 (1990) 139-82 describes a detailed study on the electrochemical and chemical polymerization, redox mechanism and electrochemical properties of polyaniline. F.Lux in "Properties of electronically conducting polyaniline: a comparison between literature and experimental findings", Polymer, 35 (1994) 2915-22 deals with the synthesis and properties of polyaniline. U.S. Patent No. 3,963,498; 4,025,463 and 5,069,820 describes oligomeric polyanilines which are described as being soluble in certain solvent and thermally stable form of polyaniline in the presence of inorganic dopant.
Hitherto preparation of conducting polyaniline is presently
carried out in the presence of inorganic acids like hydrochloric,
sulphuric and perchloric acid and organic acids like benzene
sulphonic acid (BSA), p-toluene sulphonic acid (PTSA), sulphamic
acid (SA), 5-sulphosalicyclic acid (SSA) and the like. However
the doped form of conducting polyaniline is stable upto 140-150oC
in case of inorganic acid dopants and upto 240oC in case of BSA,
PTSA, SSA. U.S. Patent No. 5,208,301 describes the sulphonic acid
substituted polyaniline for its possible use either reversible or
irreversible NH3 filter, sensor, temperature indicator and the
like. Japanese Patent No. 1999434, 870810 describes the use of
poly (vinyl sulphonic acid) doped polyaniline as a battery
electrode. Indian Patent Nos. 1200-1202/Del/90 describes
processes for the preparation of polyaniline, composites and
polyaniline grafted on insulating surfaces. Y.Wei et.al. in
"Thermal analysis of chemically synthesized polyaniline and effects of thermal aging on conductivity", J. Polymer Science: Part A: Polymer Chemistry, 27 (1989) 4351-63 has investigated the thermal stability of polyaniline doped with inorganic pro-tonic acid dopants. V.G.Kulkarni et.al. in "Thermal stability of polyaniline", Synthetic Metals, 30 (1989) 321-325; 41-43 (1991) 1009-12 gives a thermal stability data of polyaniline doped with counter inorganic and organic anions. Wang et.al. in "Thermal behavior of intrinsic polyaniline and its derivatives, Synth. Metals, 69 (1995) 263; ibid. 163-164 gives an account of the thermal properties of polyaniline, polytoluidine and polyanisi-dine by TGA and DSC techniques.
The main objective of the present invention is to provide a process for the preparation of thermally stable doped polyaniline which yields a conducting polymer which is thermally
stable upto 310oC which can find its applications in the formation of conducting composites by blending with conventional polymers.
In the drawings accompanying this specification
Figure 1 is a graph showing % weight loss as a function of temperature for polyaniline doped with PTSA. (p-toluene sulphor-ic acid)
Figure 2 is a graph showing % weight loss as a function of temperature for polyaniline doped with SOSA. (substituted oxanic sulphoric acid )
Figure 3 is a graph showing % weight loss as a function of temperature for emeraldine base form of polyaniline.
Accordingly the present invention provides a process for the preparation of doped polyaniline thermally stable upto 310°C which comprises adding 0.1 moles of aniline to an aqueous solution of organic protonic acid such as herein described, in the range of 1.0 to 3.0 molar at a temperature in the range of -5°C to 10°C, adding aqueous solution of 0.1 to 0.5 moles of oxidant such as herein described, under stirring for a period in the range 1 hour to 6 hours, followed by filtration and washing with distilled water, treating with aqueous mild base such as herein described, filtering, followed by washing with distilled water and methanol and drying by conventional methods, mixing the resultant mass with organic protonic acid at the temperature in the range of 0 - 5°C to obtain thermally stable conducting polyaniline.
The temperature of the reaction mixture may be in the rqnge of 0 - 5°C. The aqueous ammonia used may be of strength in the mage of 0.5 M to 1.0 M.
The conducting polyaniline doped with substituted aromatic oxinate sulphonic acid shows a two step decomposition. The first step corresponds to the loss of counter anion and the seciond step corresponds to the decomposition of the polymer backbone. The doping level of the doped polymer can be estimated from the weight loss in the first step of the doped polymer. In substituted oxinate sulphonate doped polyaniline, the weight loss begins at 310°C and continues upto 380°C. The weight loss is 50 % corre-
sponding to the weight of the dopant. This shows that the thermal stability of the doped polyaniline depends upon the SOSA dopant attached to the polymer backbone which probably prevents the decomposition of the polymer likely due to the electron withdrawing properties of sulphonate dopant.
The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention.
Example 1
Preparation of thermally stable conducting polyaniline containing
substituted oxinate sulphonate anion as dopant
To 1.0 M of substituted oxinate sulphonic acid in 100 ml. of
o water was added 0.1 M of aniline. To this solution at 0 C was
then added slowly 0.1 M aqueous solution of ammonium peroxydisul-phate. After stirring for 4 hours, green precipitate was filtered, washed thoroughly with water and then with methanol and diethylether. Dull green precipitate cake was then dried under
vacuum. Thermogravimetric analysis under nitrogen of the material
o polyaniline shows only a negligible weight loss upto 310 C and
o from 310 C major weight loss begins corresponding to the weight
of the dopant.
Example 2
Preparation of substituted-oxinate sulphonate doped polyaniline
by treatment of emeraldine base form of polyaniline with SOSA
To 100 ml. of 1.0 M substituted-SOSA in water was added 1.0 gram
of emeraldine base form of polyaniline. The solution was then
stirred for 3-4 hours at room temperature, filtered, washed with
SOSA and dried in vacuum at 50oC. Thermogravimetric analysis of
this material showed similar weight loss behaviour to that of
material prepared as in example 1.
Example 3
Preparation of polyaniline doped with p-toluenesulphonic acid
To 1.0 M of p-toluene sulphonic acid in 100 ml. of water was
added 0.1 M of aniline. To this solution at 0oC was then added
slowly 0.1 M aqueous solution of ammonium peroxydisulphate. After
stirring for 4 hours, green precipitate was filtered, washed
thoroughly with water and then with methanol and diethylether.
Green precipitate cake so obtained was then dried under vacuum.
Thermogravimetric analysis under nitrogen of the material polya-
niline shows only a negligible weight loss upto 240oC and from
240oC major weight loss begins corresponding to the weight of the
dopant.
Thermogravimetric analysis of polyaniline doped with p-toluene
sulphonate and substituted-oxinate sulphonate:
Brief Description of the Drawings:
In the drawings

Figure 1 is a graph showing % weight loss as a function of temperature for polyaniline doped with PTSA.
Figure 2 is a graph showing % weight loss as a function of temperature for polyaniline doped with SOSA.
Figure 3 is a graph showing % weight loss as a function of temperature for emeraldine base form of polyaniline.
An experiment was carried out to compare the thermal stability of thermally stable polyaniline of this invention and conventional doped polyaniline. The polyaniline of this invention was doped with SOSA and was prepared as described in example 1. The conventional polyaniline was doped with p-toluene sulphonic acid and was prepared as in example 3.
Samples of polyaniline doped with p-toluene sulphonate and polyaniline doped with SOSA were analyzed by Thermogravimetric analysis (TGA) under nitrogen to determine their stability to weight loss (dopant ion). The results of this experiment are set forths
in Figures 1 & 2 of the drawings accompanying this specification.
At a 20oC/minute heating rate, sample of polyaniline doped with
PTS exhibited two weight loss steps. One between 50 and 100oC (9%
weight loss) and other between 234 -338oC corresponding to dopant
loss (45 % weight loss) (as shown in Fig. 1 of the drawing).
Subjecting a sample of polyaniline doped with substituted oxine
sulphonate to the same analysis shows that initial weight loss of
approximately 8-9% corresponds to the weight of the water present
in the polymeric material and from 310 C to 380 C weight loss occurs corresponding to the weight of the dopant (as shown in Figure 2 of the drawing). Thus polyaniline doped with SOSA is much more thermally stable to the dopant loss than polyaniline
doped with PTSA. However the undoped form of polyaniline is
thermally stable upto 43 4oC (as shown in Figure 3 of the drawing) .
Because of high thermal stability of polyaniline of this invention, this material is useful as an additive in melt processing with many conventional polymers such as. poly vinylchloride, polymethamethylacrylate, polyethylene, polyproplene and the like. The thermal stability also allows the melt processing of the conducting polymer of this invention.

We Claim:
1. A process for the preparation of doped polyaniline thermally stable upto 310°C which comprises adding 0.1 moles of aniline to an aqueous solution of organic protonic acid such as herein described, in the range of 1.0 to 3.0 molar at a temperature in the range of -5°C to 10°C, adding aqueous solution of 0.1 to 0.5 moles of oxidant such as herein described, under stirring for a period in the range 1 hour to 6 hours, followed by filtration and washing with distilled water, treating with aqueous mild base such as herein described, filtering, followed by washing with distilled water and methanol and drying by conventional methods, mixing the resultant mass with organic protonic acid at the temperature in the range of 0 - 5°C to obtain thermally stable conducting polyaniline.
2. A process as claimed in claim 1 wherein the organic protonic acid used is substituted oxinate sulphoric acid.
3. A process as claimed in claims 1-2 wherein oxidant used is ammonium peroxydisulphate, potassium peroxydisulphate, sodium peroxydisulphate, potassium dichlronate.
4. A process as claimed in claims 1 to 3 wherein the mild base used is aq. ammonia.
5. A process for preparation of doped polyaniline thermally stable upto 310°C substantially as herein described with reference to examples.

Documents:

652-del-1996-abstract.pdf

652-del-1996-claims.pdf

652-del-1996-complete specification (granted).pdf

652-del-1996-correspondence-others.pdf

652-del-1996-correspondence-po.pdf

652-del-1996-description (complete).pdf

652-del-1996-description (provisional).pdf

652-del-1996-form-1.pdf

652-DEL-1996-Form-2.pdf

652-del-1996-form-4.pdf

652-del-1996-form-5.pdf

652-del-1996-form-6.pdf

652-del-1996-form-9.pdf

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Patent Number

193538

Indian Patent Application Number

652/DEL/1996

PG Journal Number

30/2004

Publication Date

24-Jul-2004

Grant Date

06-Jan-2006

Date of Filing

27-Mar-1996

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG,NEW DELHI-110001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	RANJANA MEHROTRA	NATIONAL PHYSICAL LABORATORY DR.K.S.KRISHNAN MARG ,NEW DELHI-110012,INDIA
2	SUBHAS CHANDRA	NATIONAL PHYSICAL LABORATORY DR.K.S.KRISHNAN MARG ,NEW DELHI-110012,INDIA
3	SUNDEEP KUMAR DHAWAN	NATIONAL PHYSICAL LABORATORY DR.K.S.KRISHNAN MARG ,NEW DELHI-110012,INDIA

PCT International Classification Number

C07C 87/52

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA