Title of Invention	"A PROCESS FOR THE PREPARATION OF POLYMER FILMS HAVING HIGH SOLVATOCHROMIC EFFECT"
Abstract	This invention relates to a process for the preparation of polymer films having high solvatochromic effect. Such solvatochromic films are useful in optical sensors for organic solvent vapors. Such sensors are required for non-obstructive detection of the organic vapors since there is no heat or electrical voltage are involved which otherwise may cause hazardous conditions. Optical fibers can also be coated with such films for fast sensor response. The known solvatochromic polymers reported in literature such as polydiacetylene or their derivatives cannot be coated on any substrate to give stable film. The polymer film prepared by the process shows high colour contrast when exposed to organic solvent vapors as compared to films produced by other methods which exhibits no such solvatochromic effect.

Title of Invention

"A PROCESS FOR THE PREPARATION OF POLYMER FILMS HAVING HIGH SOLVATOCHROMIC EFFECT"

Abstract

This invention relates to a process for the preparation of polymer films having high solvatochromic effect. Such solvatochromic films are useful in optical sensors for organic solvent vapors. Such sensors are required for non-obstructive detection of the organic vapors since there is no heat or electrical voltage are involved which otherwise may cause hazardous conditions. Optical fibers can also be coated with such films for fast sensor response. The known solvatochromic polymers reported in literature such as polydiacetylene or their derivatives cannot be coated on any substrate to give stable film. The polymer film prepared by the process shows high colour contrast when exposed to organic solvent vapors as compared to films produced by other methods which exhibits no such solvatochromic effect.

Full Text	This invention relates to a process for preparation of polymer films having high solvatochromic effect. More particularly it relates to deposition of polymer films which exhibit large colour contrast when exposed to different organic solvent vapours. The need for detection of chemical vapours in the environment has increased considerably due to realization of the hazards that these chemicals can cause in the industry. Such chemicals can lead to fire and explosion and can be dangerous to health. Hence there are different type of sensors which detect these chemical vapours and give alarm if the preset limit of concentration is crossed. Amongst these the optical detection is preferred in many working conditions since these are fast and least obstructing. In this application, the materials which change optical properties when exposed to such chemicals are finding large use. A few organic materials such as 3,3'-didecyl-2.2'bithiophene, 2,6 di-l,3,4-oxadiazole-toluene, 4,7 dibromobenzimidazole coupled to diethynylaryl compound have been reported in literature to exhibit colour change in presence of organic solvent vapours i.e. solvatochromism. The prior art for synthesis of these compounds comprises of reacting 240 mg of 4,7 dibromo benzimidazole having 3,5 di tert butyl phenol with 220 mg p-ethynyltoluene and 1ml triethylamine 10ml dimythyl forrnamide using 56 mg Pd- catalyst (palladium tri phenyl phosphene with Cul ). ( Macromolecules 1998 ,31, 6063) However, such materials are difficult to synthesize or coat on different substrates. For example polydiacetylene is also reported to be solvatochromic but its synthesis comprises making a precursor single crystalline monomer, exposing the same to high energy radiation for polymerization ( G.Wegner, MacromoLChem, 1984, 5, 83 ). These Polydiacetylene crystals are brittle, costly and not easy to coat in the form of thin films on glass plate etc. It is essential to overcome these drawbacks so that such materials can be easily available and used in optically active chemical sensors. The object of the present invention is to provide a process for preparing polymer filsm having high solvatochromic effect, Another object of the invention is to prepare polymer films by coating method easily on substrate to stable films with solvatochromic effect. Accordingly, the present invention provides a process for preparation of polymer films having high solvatochromic effect which comprises; polymerizing monomer chosen from heterocyclic compounds containing nitrogen atoms and selected from pyrrole, pyridine and their substituted derivatives such as methyl pyrrole, bi-pyridine in an organic solvent in which bulk polymer is dissolved,the said bulk polymer is selected from polyvinyl chloride, polyacrylates, polyethylene oxide, styrene-butadiene co-polymers and their derivatives wherein the ratio of monomer to bulk polymer is ranging between 0.5 to 2.0 by weight in presence of an electron acceptor, wherein the ratio of electron acceptor to the monomer is in the range of 2.0 to 4.0, separating the solution from precipitates by conventional techniques, coating the solution on pre-cleaned substrates, evaporating the solvent to form a film and drying the film so formed to obtain polymer films which exhibit high solvatio-chromic effect. In one embodiment of the present invention, the monomer used is chosen from heterocyclic compounds containing nitrogen atoms and may be selected from pyrrole, pyridine and their substituted derivatives such as methyl pyrrole, bi-pyridine and the like. In another embodiment of the present invention, the solvent used for polymerization contains oxygen and may be chosen from methyl ethyl ether, tetrahydrofuran, cyclohexanone, cyclopentanone, cyclopentene ether and their derivatives. In yet another embodiment of the present invention, the polymer dissolved in the reaction solvent may be chosen from film forming polymers having solubility parameter in the range of 8 to 10 and may be selected from polyvinyl chloride, polyacrylates, polyethylene oxide, styrene-butadiene co-polymers and their derivatives. In yet another embodiment of the present invention, the electron acceptor used consists of multivalent transition metal and may be selected from ferric nitrate, ferric chloride nickel chloride, nickel nitrate, cobalt chloride and cobalt nitrate. In a feature of the present invention, in the preferred range of composition the polymer film formed on glass plates when exposed to organic solvent vapours such as methanol, ethanol, benzene, toluene, xylene, etc. changed rapidly their colour from blue to pale yellow, brown, dark green etc. with high contrast of almost 1. The invention provides an easy step of preparation of an organic polymer which has solvatochromic effect and which can be coated on different substrates without difficulty. The films can be coated on filter paper strips which when exposed to different solvent vapours change colour just like pH paper and hence can be used for sensing the presence of such solvents. This is totally new concept in sensing the hazardous vapours. The invention is described herein by the following examples which are illustrative only and should not be construed to limit the scope of the invention in any manner. EXAMPLE -1 Polymethyl methacrylate (1.0 gm) was dissolved in 100 ml of tetrahydrofuran to which were added 50 ml solution of ferric nitrate (4.02 gm) dissolved separately. The mixture was stirred thoroughly with magnetic stirrer for fifteen minutes and cooled to 10 °C by using external freezing mixture. 1.5 ml of pure pyrrole was added dropwise to the solution with constant stirring and allowed to react for 4 hrs. The reaction mixture was filtered through fine filter paper and the filtrate collected in clean glass vessel. Clean microscope glass slides were coated with the filtered solution to form wet film thickness of 20 u m and allowed to dry at room temperature (28 ff C) for 2 hrs to obtain polymer films which have high solvato-chromic effect. The colour changes and the contrast obtained in these films are given in Table-1. EXAMPLE - 2 Polyvinyl chloride (1.0 gm) was dissolved in 100 ml of tetrahydrofuran to which were added 50 ml of ferric nitrate solution containing 4 g of FeNO3.9H2O and the mixture stirred thoroughly for 20 minutes and cooled to 5 °C by using external freezing mixture. 1.5 ml of pure pyrrole was added to the mixture with constant stirring and allowed to react for 4 hrs. The solution was filtered using fine filter paper and filtrate collected in glass vessel. Five drops of the solution were placed on white paper strips and allowed to dry at 30 ° C for 2 hrs. These polymer coated strips when exposed to different organic solvent vapours exhibited large change of colour. The colour change and the contrast obtained in these films are shown in Table -1 EXAMPLE -3 Polymethyl methacrylate (1.0 gm) was dissolved in 100 ml of cyclohexanone to which were added 50 ml solution of ferric nitrate (4.0 gm) dissolved separately. The mixture was stirred thoroughly with magnetic stirrer for fifteen minutes and cooled to 6 °C by using external freezing mixture. 1.5 ml of pure pyrrole was added dropwise to the solution with constant stirring and allowed to react for 6 hrs. The reaction mixture was filtered through fine filter paper and filtrate collected in clean glass vessel. Clean microscope glass slides were coated with the filtered solution to form wet film thickness of 15 jx m and allowed to dry at room temperature (28 ° C) for 3 hrs to obtain polymer films which have high solvato-chromic effect. The colour changes and the contrast obtained in these films are given in Table-1. TABLE -1: Solvatochromic Effect and Contrast Obtained in the samples synthesized by present invention (Table Removed) The contrast was obtained from the UV-Visible Spectra recorded before and after exposure of the films to respective organic vapours. It is seen from the results in the above Table-1 that the polymer films prepared by the process described in the present invention show high colour contrast when exposed to organic solvent vapours while those prepared by other methods exhibit no such solvatochromic effect. We Claim: 1. A process for preparation of polymer films having high solvatochromic effect which comprises; polymerizing monomer chosen from heterocyclic compounds containing nitrogen atoms and selected from pyrrole, pyridine and their substituted derivatives such as methyl pyrrole, bi-pyridine in an organic solvent in which bulk polymer is dissolved,the said bulk polymer is selected from polyvinyl chloride, polyacrylates, polyethylene oxide, styrene-butadiene co¬polymers and their derivatives wherein the ratio of monomer to bulk polymer is ranging between 0.5 to 2.0 by weight in presence of an electron acceptor, wherein the ratio of electron acceptor to the monomer is in the range of 2.0 to 4.0, separating the solution from precipitates by conventional techniques, coating the solution on pre-cleaned substrates, evaporating the solvent to form a film and drying the film so formed to obtain polymer films which exhibit high solvatio-chromic effect. 2. A process as claimed in claim 1 wherein the solvent used for polymerization contains oxygen selected from methyl ethyl either, tetrahydrofuran, cyclohexannone, cyclopentanone, cyclopentene either and their derivatives. 3. A process as claimed in claims 1 to 2, wherein the ratio of monomer to bulk polymer is preferably 1.4 to 1.6 by weight. 4. A process as claimed in 1 to 3, wherein the electron acceptor used consists of multivalent transition metal selected from ferric nitrate, ferric chloride, nickel chloride, nickel nitrate, cobalt chloride and cobalt nitrate. 5. A process as claimed in claims 1 to 4, wherein the ratio of electron acceptor to the monomer is preferably 2.5 to 3.0 by weight. 6. A process as claimed in claims 1 to 5, wherein the polymerization is carried out at a temperature ranging from 2 to 10°C. 7. A process as claimed din claims 1 to 6, wherein the time for polymerization reaction ranges from 1 to 6 hr 8. A process as claimed din claims 1 to 7 wherein the drying of the film is carried out at temperatures ranging from 25 to 50°C preferably 28 to 30°C. 9. A process for preparing polymer films having high solvatochromic effect as substantially described herein before with reference to examples.

Full Text

This invention relates to a process for preparation of polymer films having high solvatochromic effect. More particularly it relates to deposition of polymer films which exhibit large colour contrast when exposed to different organic solvent vapours.
The need for detection of chemical vapours in the environment has increased considerably due to realization of the hazards that these chemicals can cause in the industry. Such chemicals can lead to fire and explosion and can be dangerous to health. Hence there are different type of sensors which detect these chemical vapours and give alarm if the preset limit of concentration is crossed. Amongst these the optical detection is preferred in many working conditions since these are fast and least obstructing. In this application, the materials which change optical properties when exposed to such chemicals are finding large use. A few organic materials such as 3,3'-didecyl-2.2'bithiophene, 2,6 di-l,3,4-oxadiazole-toluene, 4,7 dibromobenzimidazole coupled to diethynylaryl compound have been reported in literature to exhibit colour change in presence of organic solvent vapours i.e. solvatochromism. The prior art for synthesis of these compounds comprises of reacting 240 mg of 4,7 dibromo benzimidazole having 3,5 di tert butyl phenol with 220 mg p-ethynyltoluene and 1ml triethylamine 10ml dimythyl forrnamide using 56 mg Pd- catalyst (palladium tri phenyl phosphene with Cul ). ( Macromolecules 1998 ,31, 6063) However, such materials are difficult to synthesize or coat on different substrates. For example polydiacetylene is also reported to be solvatochromic but its synthesis comprises making a precursor single crystalline monomer, exposing the same to high energy radiation for polymerization ( G.Wegner, MacromoLChem, 1984, 5, 83 ). These

Polydiacetylene crystals are brittle, costly and not easy to coat in the form of thin films on glass plate etc. It is essential to overcome these drawbacks so that such materials can be easily available and used in optically active chemical sensors.
The object of the present invention is to provide a process for preparing polymer filsm having high solvatochromic effect,
Another object of the invention is to prepare polymer films by coating method easily on substrate to stable films with solvatochromic effect.
Accordingly, the present invention provides a process for preparation of polymer films having high solvatochromic effect which comprises; polymerizing monomer chosen from heterocyclic compounds containing nitrogen atoms and selected from pyrrole, pyridine and their substituted derivatives such as methyl pyrrole, bi-pyridine in an organic solvent in which bulk polymer is dissolved,the said bulk polymer is selected from polyvinyl chloride, polyacrylates, polyethylene oxide, styrene-butadiene co-polymers and their derivatives wherein the ratio of monomer to bulk polymer is ranging between 0.5 to 2.0 by weight in presence of an electron acceptor, wherein the ratio of electron acceptor to the monomer is in the range of 2.0 to 4.0, separating the solution from precipitates by conventional techniques, coating the solution on pre-cleaned substrates, evaporating the solvent to form a film and drying the film so formed to obtain polymer films which exhibit high solvatio-chromic effect.
In one embodiment of the present invention, the monomer used is chosen from heterocyclic compounds containing nitrogen atoms and may be selected from pyrrole, pyridine and their substituted derivatives such as methyl pyrrole, bi-pyridine and the like.

In another embodiment of the present invention, the solvent used for polymerization contains oxygen and may be chosen from methyl ethyl ether, tetrahydrofuran, cyclohexanone, cyclopentanone, cyclopentene ether and their derivatives.
In yet another embodiment of the present invention, the polymer dissolved in the reaction solvent may be chosen from film forming polymers having solubility parameter in the range of 8 to 10 and may be selected from polyvinyl chloride, polyacrylates, polyethylene oxide, styrene-butadiene co-polymers and their derivatives.
In yet another embodiment of the present invention, the electron acceptor used consists of multivalent transition metal and may be selected from ferric nitrate, ferric chloride nickel chloride, nickel nitrate, cobalt chloride and cobalt nitrate.
In a feature of the present invention, in the preferred range of composition the polymer film formed on glass plates when exposed to organic solvent vapours such as methanol, ethanol, benzene, toluene, xylene, etc. changed rapidly their colour from blue to pale yellow, brown, dark green etc. with high contrast of almost 1.
The invention provides an easy step of preparation of an organic polymer which has solvatochromic effect and which can be coated on different substrates without difficulty. The films can be coated on filter paper strips which when exposed to different solvent vapours change colour just like pH paper and hence can be used for

sensing the presence of such solvents. This is totally new concept in sensing the hazardous vapours.
The invention is described herein by the following examples which are illustrative only and should not be construed to limit the scope of the invention in any manner.
EXAMPLE -1
Polymethyl methacrylate (1.0 gm) was dissolved in 100 ml of tetrahydrofuran to which were added 50 ml solution of ferric nitrate (4.02 gm) dissolved separately. The mixture was stirred thoroughly with magnetic stirrer for fifteen minutes and cooled to 10 °C by using external freezing mixture. 1.5 ml of pure pyrrole was added dropwise to the solution with constant stirring and allowed to react for 4 hrs. The reaction mixture was filtered through fine filter paper and the filtrate collected in clean glass vessel. Clean microscope glass slides were coated with the filtered solution to form wet film thickness of 20 u m and allowed to dry at room temperature (28 ff C) for 2 hrs to obtain polymer films which have high solvato-chromic effect. The colour changes and the contrast obtained in these films are given in Table-1.
EXAMPLE - 2
Polyvinyl chloride (1.0 gm) was dissolved in 100 ml of tetrahydrofuran to which were added 50 ml of ferric nitrate solution containing 4 g of FeNO3.9H2O and the mixture stirred thoroughly for 20 minutes and cooled to 5 °C by using external freezing

mixture. 1.5 ml of pure pyrrole was added to the mixture with constant stirring and allowed to react for 4 hrs. The solution was filtered using fine filter paper and filtrate collected in glass vessel. Five drops of the solution were placed on white paper strips and allowed to dry at 30 ° C for 2 hrs. These polymer coated strips when exposed to different organic solvent vapours exhibited large change of colour. The colour change and the contrast obtained in these films are shown in Table -1
EXAMPLE -3
Polymethyl methacrylate (1.0 gm) was dissolved in 100 ml of cyclohexanone to which were added 50 ml solution of ferric nitrate (4.0 gm) dissolved separately. The mixture was stirred thoroughly with magnetic stirrer for fifteen minutes and cooled to 6 °C by using external freezing mixture. 1.5 ml of pure pyrrole was added dropwise to the solution with constant stirring and allowed to react for 6 hrs. The reaction mixture was filtered through fine filter paper and filtrate collected in clean glass vessel. Clean microscope glass slides were coated with the filtered solution to form wet film thickness of 15 jx m and allowed to dry at room temperature (28 ° C) for 3 hrs to obtain polymer films which have high solvato-chromic effect. The colour changes and the contrast obtained in these films are given in Table-1.

TABLE -1: Solvatochromic Effect and Contrast Obtained in the samples synthesized by present invention
(Table Removed)

The contrast was obtained from the UV-Visible Spectra recorded before and after exposure of the films to respective organic vapours.
It is seen from the results in the above Table-1 that the polymer films prepared by the process described in the present invention show high colour contrast when exposed to organic solvent vapours while those prepared by other methods exhibit no such solvatochromic effect.

We Claim:
1. A process for preparation of polymer films having high solvatochromic effect which comprises; polymerizing monomer chosen from heterocyclic compounds containing nitrogen atoms and selected from pyrrole, pyridine and their substituted derivatives such as methyl pyrrole, bi-pyridine in an organic solvent in which bulk polymer is dissolved,the said bulk polymer is selected from polyvinyl chloride, polyacrylates, polyethylene oxide, styrene-butadiene co¬polymers and their derivatives wherein the ratio of monomer to bulk polymer is ranging between 0.5 to 2.0 by weight in presence of an electron acceptor, wherein the ratio of electron acceptor to the monomer is in the range of 2.0 to 4.0, separating the solution from precipitates by conventional techniques, coating the solution on pre-cleaned substrates, evaporating the solvent to form a film and drying the film so formed to obtain polymer films which exhibit high solvatio-chromic effect.
2. A process as claimed in claim 1 wherein the solvent used for polymerization contains oxygen selected from methyl ethyl either, tetrahydrofuran, cyclohexannone, cyclopentanone, cyclopentene either and their derivatives.
3. A process as claimed in claims 1 to 2, wherein the ratio of monomer to bulk polymer is preferably 1.4 to 1.6 by weight.
4. A process as claimed in 1 to 3, wherein the electron acceptor used consists of multivalent transition metal selected from ferric nitrate, ferric chloride, nickel chloride, nickel nitrate, cobalt chloride and cobalt nitrate.
5. A process as claimed in claims 1 to 4, wherein the ratio of electron acceptor to the monomer is preferably 2.5 to 3.0 by weight.
6. A process as claimed in claims 1 to 5, wherein the polymerization is carried out at a temperature ranging from 2 to 10°C.
7. A process as claimed din claims 1 to 6, wherein the time for polymerization reaction ranges from 1 to 6 hr
8. A process as claimed din claims 1 to 7 wherein the drying of the film is carried out at temperatures ranging from 25 to 50°C preferably 28 to 30°C.

9. A process for preparing polymer films having high solvatochromic effect as substantially described herein before with reference to examples.

Documents:

937-DEL-2002-Abstract-(07-10-2008).pdf

937-del-2002-abstract.pdf

937-DEL-2002-Claims-(07-10-2008).pdf

937-del-2002-claims.pdf

937-DEL-2002-Correspondence-Others-(07-10-2008).pdf

937-del-2002-correspondence-others.pdf

937-DEL-2002-Description (Complete)-(07-10-2008).pdf

937-del-2002-description (complete).pdf

937-del-2002-form-1.pdf

937-del-2002-form-18.pdf

937-del-2002-form-2.pdf

937-DEL-2002-Form-3-(07-10-2008).pdf

937-del-2002-form-3.pdf

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Patent Number

225687

Indian Patent Application Number

937/DEL/2002

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

20-Nov-2008

Date of Filing

16-Sep-2002

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH.

Applicant Address

RAFI MARG, NEW DELHI-110 001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SUBRAMANIAM RADHAKRISHNAN	NATIONAL CHEMICAL LABORATORY, PUNE 411008, MAHARASTRA INDIA
2	SREEJITH VALIYAVALAPPIL	NATIONAL CHEMICAL LABORATORY, PUNE 411008, MAHARASTRA INDIA

PCT International Classification Number

C08F 83/30

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA