Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF FUNCTIONALIZED POLYSTYRENE
Abstract	This invention provides an improved process for the preparation of functionalized polystyrene. In particular, the present invention provides an improved process for the preparation of poly (acetoxystyrene). The poly (acetoxy styrene) prepared by the process of this invention can be used for the preparation of poly (hydroxy styrene) a potential photoresist material.

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Field of the invention This invention relates to an improved process for the preparation of functionalized polystyrene. More particularly, it relates to a process for the preparation of poly (acetoxystyrene), effected by the modification of polystyrene to get a material containing acetoxy functional groups. The fictionalized polystyrene prepared by the process of this invention has the following structure: (Figure Removed) The poly (acetoxy styrene) prepared by the process of this invention can be used for the preparation of poly (hydroxy styrene) a potential photoresist material. The term photoresist materials refer to a formulation. The key component in the formulation useful as a photoresist is the correct choice of the polymer. In practical applications other ingredients are solvent, sensitizers, optionally dye have to be added. Background of the invention The role of the polymer is to create patterns after exposure to irradiation. Upon exposure to irradiation, a chemical reaction occurs which makes the polymer soluble or insoluble when in contact with a developer. The reactions are classified under two heads, one wherein the polymer on exposure to irradiation becomes soluble in the unexposed areas and the other wherein the exposed area become insoluble. The former are termed as negative, while the latter are terms as positive photoresists. The spectral region of exposure determines the usefulness of a photoresist in practical applications. Although the initially the region of 200 and 260 nm was associated with deep-UV due to the spectral sensitivity of the photoresist used, it is now been accepted that the region 200 to 300 nm can be used for deep-UV photolithography. The material prepared by the process of this invention, namely, acetoxy polystyrene can be conveniently modified to hydroxy polystyrene and can be used as a potential material for deep-UV applications. Conventionally reported method for the preparation of acetoxy polystyrene employs the methodology that uses hydrogen peroxide and peracids. (Journal of Polymer Science : Part A, Polymer Chemistry, Vol. 38, 453-461, 2000). Another method of preparing polyacetoxy styrene involves polymerization of acetoxy styrene, a method that could lead to material with molecular weight distribution in addition to the problems in the polymerization methodology and affects the process economics to a great extent (Journal of Polymer Science : Part B, Polymer Physics, Vol. 40, 1661-1672, 2002; Polymer, Vol. 42, 9843-9848, 2001; Macromol. Chem. Phys., Vol. 203, 868-878, 2002 ) The acetoxy derivative of polystyrene prepared as per the process of this invention can be suitably modified to obtain poly (hydroxy styrene) and used directly for the preparation of photoresist formulation. The primary requirements for a material useful for photoresist applications are- 1. The material should have good film forming characteristics on various substrates. 2. The material should have sufficient resistance to chemicals during wet etching process. 3. The material should not be affected to radiations during exposure to a variety of light sources. 4. The material should have sufficient adhesive strength to bond to different substrates, 5. The molecular weight of the material should not be very high and the molecular weight distribution should not be very large. 6. The material should have good thermal properties in the temperature range upto 120°C. Objects of the invention The main object of the present invention is to provide an improved process for the preparation of functionalized polystyrene with acetoxy functional groups that are suitable for preparation of photoresist materials. Another object of the present invention is to provide a process for the preparation of functionalized polystyrene with acetoxy functional groups that uses polystyrene as the starting material. Yet another object of the present invention is to provide a process for the preparation of functionalized polystyrene with acetoxy functional groups that does not use hazardous chemicals such as hydrogen peroxide. Summary of the invention Accordingly, the present invention provides an improved process for the preparation of functionalized polystyrene formula 1, (Figure Removed) which comprises, contacting the solution of polyacetyl styrene in weak organic acid with a solution of alkali metal perborate or percarbonate in the same acid, in the presence of trihaloacetic acid and optionally acetic anhydride, stirring the above said reaction mixture, at a speed of 150 to 200 rpm, at a temperature in the range of 25 to 50°C, for a period of 20 to 48 hours, filtering the reaction mass to remove the excess perborate / percarbonate and separating the product by precipitation in water and isolating the resultant solid by known method, followed by washing and drying under reduced pressure, at a temperature in the range of 40 to 60°C to obtain the desired product. In an embodiment of the present invention the weak organic used is acetic acid. In yet another embodiment the trihaloacetic acid used is selected from trichloroacetic acid and trifluoroacetic acid. In yet another embodiment, the alkali metal perborate used is sodium perborate. In still another embodiment the percarbonate used is sodium percarbonate, The process of the present invention is described with reference to following examples, which are illustrative only and should not be construed to limit the scope of this invention in any manner. As an illustration, the method for the preparation of acetyl polystyrene is given in Example 1, which describes the procedure for the preparation of acetyl polystyrene by the known procedure in the literature. EXAMPLE 1 2.5 grams of polystyrene was dissolved in 80 ml of carbon disulphide. This solution was cooled with ice under stirring. 8 grams of aluminium chloride was added to this solution. A solution of 3 grams of acetyl chloride in 30 ml of carbon disulphide was added drop wise to the reaction mixture. After the addition of acetyl chloride was completed, the reactants were allowed to reach ambient temperature and the reactants were maintained at the ambient temperature for a period of 150 minutes under stirring. The product acetyl polystyrene was separated by precipitation in cold water, filtered, dissolved in acetone and precipitated in methanol. EXAMPLE 2 1 gram of poly (acetyl styrene) prepared as per example 1, 3.16 grams of sodium perborate, 1.30 ml of acetic anhydride and 2.2 grams of trichloroacetic acid were mixed in 30 ml of acetic acid and the reactants were gently stirred at a rpm of 200 and maintained at ambient temperature of 25°C for 48 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C. EXAMPLE 3 To 30 ml of acetic acid used as solvent, 1 gram of poly (acetyl styrene) prepared as per example 1, 3.16 grams of sodium perborate, 1.30 ml of acetic anhydride and 6.6 grams of trichloroacetic acid were added and the reactants were gently stirred at a rpm of 200 and maintained at temperature of 35°C for 24 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C. Example 4 To 15 ml of acetic acid used as solvent, 2 grams of poly (acetyl styrene) prepared as per example 1, 6.32 grams of sodium perborate, and 8.5 grams of trichloroacetic acid were added and the reactants were gently stirred at a rpm of 150 and maintained at ambient temperature of 25°C for 24 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C. EXAMPLE 5 To 15 ml of acetic acid used as solvent, 2 grams of poly (acetyl styrene) prepared as per example 1, 6.32 grams of sodium perborate, and 6.5 grams of trifluoroacetic acid were added and the reactants were gently stirred at a rpm of 150 and maintained at ambient temperature of 25°C for 24 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C. Example 6 1 gram of poly (acetyl styrene) prepared as per example 1, 3.2 grams of sodium percarbonate, 1.30 ml of acetic anhydride and 2.2 grams of trichloroacetic acid were mixed in 30 ml of acetic acid and the reactants were gently stirred at a rpm of 200 and maintained at ambient temperature of 25°C for 36 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C. EXAMPLE 7 1 gram of poly (acetyl styrene) prepared as per example 1, 3.2 grams of sodium percarbonate, and 8.5 grams of trichloroacetic acid were mixed in 30 ml of acetic acid and the reactants were gently stirred at a rpm of 200 and maintained at ambient temperature of 25°C for 48 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C EXAMPLE 8 To 15 ml of acetic acid used as solvent, 2 grams of poly (acetyl styrene) prepared as per example 1, 6.25 grams of sodium percarbonate, and 6.5 grams of trifluoroacetic acid were added and the reactants were gently stirred at a rpm of 150 and maintained at ambient temperature of 25°C for 24 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C EXAMPLE 9 To 25 ml of acetic acid used as solvent, 4 grams of poly (acetyl styrene) prepared as per example 1, 8.4 grams of sodium perborate, and 12.5 grams of trichoroacetic acid were added and the reactants were gently stirred at a rpm of 150 and maintained at ambient temperature of 50°C for 20 hours. The reactants were decanted, the filtrate was precipitated in water and the product isolated by conventional methods, washing with water, followed by drying at 60°C Advantages of the present invention: 1. The process of this invention does not use hazardous chemicals such as hydrogen peroxide, concentrated sulphuric acid etc. 2. The polystyrene derivative with functional acetoxy groups obtained by the process of this invention can be used for the preparation of photoresist materials. 3. The process of this invention is amenable for scale up operation. 4. The process of this invention has low reaction time offering process economics in the synthesis. 5. The process of this invention uses cheap large scale chemicals such as sodium perborate and sodium percarbonate. We Claim 1. An improved process for the preparation of functionalized polystyrene formula 1, (Figure Removed) which comprises, contacting the solution of polyacetyl styrene in weak organic acid with a solution of alkali metal perborate or percarbonate in the same acid, in the presence of trihaloacetic acid and optionally acetic anhydride, stirring the above said reaction mixture, at a speed of 150 to 200 rpm, at a temperature in the range of 25 to 50°C, for a period of 20 to 48 hours, filtering the reaction mass to remove the excess perborate / percarbonate and separating the product by precipitation in water and isolating the resultant solid by known method, followed by washing and drying under reduced pressure, at a temperature in the range of 40 to 60°C to obtain the desired product. 2. An improved process as claimed in claim 1, wherein the weak organic used is acetic acid. 3. An improved process as claimed in claims 1 and 2, wherein the trihaloacetic acid used is selected from trichloroacetic acid and trifluoroacetic acid. 4. An improved process as claimed in claims 1-3, wherein, the alkali metal perborate used is sodium perborate. 5. An improved process as claimed in claims 1-3, wherein the percarbonate used is sodium percarbonate, 6. An improved process for the preparation of functionalized polystyrene with acetoxy functional groups, substantially as herein described with reference to the examples.

Documents:

850-del-2006-Abstract-(10-04-2013).pdf

850-del-2006-abstract.pdf

850-del-2006-Claims-(10-04-2013).pdf

850-del-2006-claims.pdf

850-del-2006-Correspondence Others-(10-04-2013).pdf

850-del-2006-correspondence-others.pdf

850-del-2006-description (provisional).pdf

850-del-2006-description(complete).pdf

850-del-2006-form-1.pdf

850-DEL-2006-Form-18-(09-01-2008).pdf

850-del-2006-form-2.pdf

850-del-2006-Form-3-(10-04-2013).pdf

850-del-2006-form-3.pdf

850-del-2006-form-5.pdf

850-DEL2006-Correspondence-Others-(09-01-2008).pdf