WO2016113761A1

WO2016113761A1 - Hydrophobic polymer-supported lewis acid catalyst and process for the preparation thereof

Info

Publication number: WO2016113761A1
Application number: PCT/IN2016/050016
Authority: WO
Inventors: Nayaku Nivrati Chavan; Surendra PONRATHNAM; Sachin Tanaji MANE
Original assignee: Council Of Scientific & Industrial Research
Priority date: 2015-01-15
Filing date: 2016-01-15
Publication date: 2016-07-21

Abstract

The patent discloses a hydrophobic poly(AA-co-DVB) supported Lewis acid as a heterogeneous catalyst for anhydrous reaction. These unmodified polymer and polymer-supported Lewis acid catalysts were characterized by different techniques such as surface area, thermal degradation, glass transition temperature, reactivity, and swelling behaviour. Hydrophobic and more reactive polymer was selected for the use as a catalyst in anhydrous reaction. Overall, the invention relates to a process for the synthesis hydrophobic poly(AA-co-DVB) supported Lewis acid catalyst and its use for anhydrous reaction.

Description

"HYDROPHOBIC POLYMER- SUPPORTED LEWIS ACID CATALYST AND PROCESS FOR THE PREPARATION THEREOF"

FIELD OF THE INVENTION

The present invention relates to a hydrophobic poly (Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst for anhydrous reaction which exhibits high loading and avoids the leakage problem of catalyst during application. Particularly, present invention relates to the immobilization of Lewis acid catalyst on poly(AA-co-DVB) which can be easily recovered, recycled, and repeatedly used in various organic transformations or chemical reactions. More particularly, present invention relates to polymer-supported Lewis acid catalyst useful in synthesis of polyimine.

BACKGROUND AND PRIOR ART OF THE INVENTION

Charles Friedel and James Crafts invented the reaction to attach the substituent to the aromatic ring. In most of the cases, unsupported Lewis acid catalyst used in organic reactions are difficult to separate after completion of reaction and traces of catalyst may remain in the product which may deteriorate the purity of final product. Another concern is that unsupported Lewis acid may be used only once and discarded after use, thus, it pollutes the environment. Undoubtedly, polymer-supported Lewis acid catalyst eliminates both problems. In other words, polymer-supported Lewis acid is easily recoverable by filtration and can be recycled and reused for number of times. The polymer-supported Lewis acids are industrially economical and environmentally benign.

Most of the organic reactions have been carried out in organic solvents; as a result polymer-support to be used for immobilization of Lewis acid should have hydrophobic properties for better results. Friedel-Craft reaction using Lewis acid as a catalyst is very old method for C-C bond formation. In the past, Lewis acid catalysts were used at high temperature ranging from 50 to 300°C depending on reaction conditions.

Article titled, "Polymer-protected reagents. Polystyrene-aluminum chloride" by D. C. Neckers et al, Int. J. Am. Chem. Soc., 1972, 94(26), 9284-9285 reports a tightly bound complex of styrene-divinylbenzene copolymer beads and anhydrous aluminum chloride, as a mild Lewis acid catalyst for organic reactions.

Article titled, "Friedel Crafts acylation reaction using polymer-supported aluminium chloride" by A. P. Deshmukh et al, J. Chem. Res. (S), 1999, 568-569 reports Friedel Crafts reactions using polymer-supported A1C1₃ and the effect of crosslinking level on ortho:para ratio.

US 2009/0110907 Al relates to polymer membranes that include a crosslinked poly(vinyl alcohol-co-vinylamine), which are non-porous or are porous with pores having a median pore size of 300 nm or less.

US 5,770,539 relates to Lewis acid catalysts which are immobilized on a porous polymer substrate.

E.P. Pat. No. 1,997,555 Bl relates to immobilized Lewis acids which act as a catalyst and can be used in various chemical reactions for more turn over number without any loss of activity.

E.P. Pat. No. 1, 184,076 Bl relates to a novel Lewis acid catalyst which shows high reactivity even in an aqueous medium without the use of organic solvents, is easily prepared, recovered, and is excellent in reusability, and to methods of organic synthesis using such a novel Lewis acid catalyst.

E.P. Pat. No. 1,069, 127 Bl invented that, Lewis acid encapsulated polymer may suffer through aggregation and described its applications in Aldol and Mannich reaction.

Article titled, "Polymer-supported Lewis acid catalysts. VI. Polystyrene-bonded stannic chloride catalyst" by RAN Ruicheng et al, Chinese J. Polym. Sci., 1991, 9(1), 79-85 reports a polystyrene-bonded stannic chloride catalyst which was synthesized by the method of lithium polystyryl combined with stannic chloride. This catalyst is a polymeric organometallic compound containing 0.25 mmol Sn (IV)/g catalyst. The catalyst showed sufficient stability and catalytic activity in organic reaction such as esterification, acetylation and ketal formation, and it could be reused many times without losing its catalytic activity.

Article titled, "Cycloreversion of quadricyclane to norbornadiene catalyzed by Tin (II) complexes" by M. E. Landis et al, Tetrahedron Lett, 1982, 23(4), 375-378 reports conversion of quadricyclane to norbornadiene catalyzed by stannous chloride and stannous chloride-phosphine complexes. A newly synthesized polymer-bound phosphine-stannous chloride complex also proved effective in the catalytic conversion.

Article titled, "Organic polymer supports for synthesis and for reagent and catalyst immobilization" by J. Lu et al, Chem. Rev., 2009, 109(2), 815-838 relates to divinylbenzene as a crosslinker for various polymerization reactions. It also reports poly(ethylene imine) condensation with small quantities of terephthalic dialdehyde to form a cross-linked polyimine network with very high loading level in range of 10.0- 16.0 mmol/g.

Article titled, "Heteropolyanions doped polyimine-preparation and spectroscopic properties" by I. Kulszewicz-Bajer et al, Mater. Res. Bull, 1995, 30, 1571-1578 relates to aromatic polyimine obtained by the condensation of p-phenylenediamine and terephtalaldehyde can be chemically doped with heteropolyanions of Keggin- type.

Article titled, "Polyimine, a C=N double bond containing polymers: synthesis and properties" by K. Suematsu et al, Polym. J., 1983, 15, 71-79 reports polymerization of terephthalaldehyde and hexamethylenediamine to obtain a film-forming high molecular weight polyimine solution was considerably facilitated through the use of w-cresol as a solvent under mild conditions. A crystalline but partially cross-linked powder and film were obtained from the solution.

WO 2004003044 A2 relates to polymers capable of sustaining and/or promoting a process involving the exchange of the regular repeating monomer units presented in the form of a polyhydrazone or a polyimine, polymerized by repeating alternating units of dihydrazides and/or diamines and dialdehydes, but not limited to these two polymers and may also include other alternating co-polymers, defined as Dynamers. Also, it relates to a process of exchanging the regular repeating monomer units of a polyhydrazone or polyimine, polymerized by the condensation of alternating units of dihydrazides and/or diamines and dialdehydes, but not limited to these two polymers and may also include other alternating co-polymers, defined as Dynamerization. Further, the process of exchanging the regular repeating monomer units of a polyimine whereby polymers's solubility has changed from hydrophobic to hydrophilic or vice- versa. US 2014/0241966 Al cross-linked poly(allylamine) is prepared by crosslinking of poly(allylamine) with epichlorohydrin (PAAEPI), branched poly(allylamine) prepared by branching of poly(allylamine) with divinylbenzene (PAADVB) with mol. wt. in the range of 500 to 2200 g/mol.

US 2011/0139466 Al discloses 4, 4 ' PHENYLENEDI AMINE.

US 4,000, 187 disclose aromatic diketones.

US 3,506,613 relates to reacting an aliphatic or aromatic substituted aliphatic diketone and an aliphatic diamine such that they results a linear, non cross-conjugated polymer. US 3,668, 183 relates to polyenamine resins useful as adhesives and in coating applications are produced from the reaction of polyacetoacetates or polyacetoacetamides with blocked polyamines. The blocked polyamines are ketimines or enamines obtained by the reaction of an amine or amide with either a ketone or an aldimine obtained by the reaction of an amine or amide with an aldehyde.

US 2,352,387 relates to the process of producing condensation products which consists of condensing a primary aliphatic diamine containing at least 6 carbon atoms and only two amino groups with a monomeric carbonyl compound selected from the class consisting of aldehydes and ketones in the molecular ratio of about one carbonyl group of the carbonyl compounds for each amino group of the diamine.

US 3,461, 100 relates to a polymeric material for use as a protective coating, which is insoluble in water but soluble in a common aliphatic hydrocarbon solvent, can be produced by condensing an aldehyde or ketone (formaldehyde) with a diamine (hexamethylenediamine) in organic medium while continuously removing by-product water.

Article titled, "Hydrophilic polymer supports for solid-phase synthesis: preparation of poly(ethylene glycol) methacrylate polymer beads using "classical" suspension polymerization in aqueous medium and their application in the solid-phase synthesis of hydantoins." by R. Kita et al, J. Comb. Chem., 2001, 3, 564-571 reports a completely water soluble crosslinker in a classical suspension polymerization by using cyclohexanol as the porogen.

Article titled, "Porous copolymer resins: tuning pore structure and surface area with non reactive porogens" by M. H. Mohamed et al, Nanomaterials, 2012, 2, 163-186 the preparation of porous copolymer resin (PCR) materials via suspension polymerization with variable properties are described by tuning the polymerization reaction, using solvents which act as porogens, to yield microporous, mesoporous, or macroporous materials.

Over the last decade, Lewis acids which were potentially used in organic synthesis are aluminium chloride, stannous chloride, mercury chloride, boron trifluoride, and titanium tetrachloride. Different methods including immobilization, encapsulation, coordinate complex, anchoring (covalent), and entrapment are widely used to support the Lewis acids onto the porous polymer matrix. Leakage and small loading of catalysts are the major concern with applications of supported species. In most of the cases, polymer-supported Lewis acid was used in high temperature reactions, consequently, thermal stability of base polymer and polymer-supported Lewis acid was studied before the use in solid-phase synthesis.

Therefore, it is the need to develop a hydrophobic polymer-supported Lewis acid which is thermostable, exhibits high loading and avoids the leakage problem of catalyst during application.

OBJECTIVE OF THE INVENTION

The main objective of the present invention is to provide a thermostable hydrophobic poly(AA-co-DVB) supported Lewis acid catalyst which exhibits high loading and avoids the leakage problem of catalyst during application in reaction.

Another objective of the present invention is to provide a process for the synthesis of hydrophobic poly(AA-co-DVB) supported Lewis acid as a catalyst for anhydrous reaction.

Yet another objective of the present invention is to provide a polymer-supported Lewis acid catalyst for the synthesis of polyimine.

ABBREVIATIONS USED

ADC Allylamine-divinylbenzene-cyclohexanol

ADCA Allylamine-divinylbenzene-cyclohexanol-aluminium chloride ADCS Allylamine-divinylbenzene-cyclohexanol-stannous chloride CLD Crosslink density

Poly(AA-co-DVB) Poly(allylamine-co-divinylbenzene) SUMMARY OF THE INVENTION

Accordingly, present invention provides a hydrophobic poly(Allylamine-co- divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst comprising poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] in the range of 60 to 90 wt% and Lewis acid in the range of 10 to 40wt%.

In another embodiment, present invention provides a process for the synthesis of hydrophobic poly(AA-co-DVB) supported Lewis acid catalyst comprising the steps of:

a. conducting suspension polymerization by adding the oil phase comprising allylamine, divinylbenzene, 2,2'-azobisisobutyronitrile, and cyclohexanol as a porogen to the suspension reactor containing poly(vinylpyrrolidone) as a protective colloid solution in water with constant stirring to obtain the reaction mixture;

b. polymerizing the reaction mixture as obtained in step (a) by heating the reactor and obtain the product in the form of beads which on purification affords the copolymer [poly(AA-co-DVB)] in 70-80% yields; c. adding Lewis acid solution to copolymer as obtained in step (b) followed by washing and drying to affords poly(AA-co-DVB) supported Lewis acid catalyst.

In another embodiment of the present invention, Lewis acids used is selected from aluminium chloride or stannous chloride.

In yet another embodiment of the present invention, said catalyst is thermostable upto 400°C and useful for high temperature reactions.

In yet another embodiment of the present invention, said catalyst exhibit glass transition temperature upto 240°C.

In yet another embodiment of the present invention, said catalyst is recyclable and reusable.

In yet another embodiment of the present invention, said catalyst is useful to avoids the catalyst leakage during organic transformations.

In yet another embodiment of the present invention, said catalyst is useful in an organic synthesis and functional group transformation. In another embodiment, present invention provides a process for the synthesis of polyimine using the catalyst as claimed in claim 1, and the said process comprising the steps of:

a. mixing 4,4'-diacetylbiphenyl, N-methyl-2-pyrrolidone and poly(AA-co- DVB) supported Lewis acid catalyst followed by stirring and adding para phenylene diamine and stirring to obtain the reaction mixture; b. filtering the reaction mixture as obtained in step (a) to recover poly(AA- co-OV ) supported Lewis acid catalyst and adding alcohol to the filtrate to form precipitate which on filtration, washing, and drying furnishes the desired product polyimine.

In yet another embodiment of the present invention, alcohol used is preferably ethanol

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 : depicts Fourier transform infrared (FT-IR) spectrum of base (ADC) and polymer-supported Lewis acid(ADCA and ADCS).

Figure 2: depicts average particle size of base and polymer-supported Lewis acid.

Figure 3 : depicts DTG thermograms of base and polymer-supported Lewis acid.

Figure 4: depicts DSC thermograms of base and polymer-supported Lewis acid.

Figure 5: depicts swelling ratio of polymer-supported Lewis acid.

Figure 6: depicts Scanning electron microscopy (SEM) images of base (ADC) and polymer-supported Lewis acid (ADCA and ADCS) for 5% and 25% crosslink density

(2500x magnification).

Figure 7: depicts EDX analysis of polymer-supported Lewis acid (a) wt%, and (b) at%

Figure 8: depicts 1H MR of polyimine.

Figure 9: depicts DTG thermograms of polyimine.

Scheme 1 represents process steps for the synthesis of poly(AA-co-DVB) and its modification with Lewis acid.

Scheme 2 represents process steps for the synthesis of polyimine. DETAILED DESCRIPTION OF THE INVENTION

Present invention provides a thermostable hydrophobic poly(AA-co-DVB) supported Lewis acid catalyst which exhibits high loading and avoids the leakage problem of catalyst during application in reaction.

The present invention provides a process for the synthesis of hydrophobic poly(AA- co-DVB) supported Lewis acid catalyst which is used in an organic synthesis and functional group transformation reactions.

Further, it provides a process for the synthesis of hydrophobic poly(AA-co-DVB) supported Lewis acid as a catalyst and its use for the synthesis of polyimine.

Hydrophobic poly(AA-co-DVB) supported Lewis acid catalyst was used for anhydrous reaction, wherein the Lewis acid is bonded to the polymer support through a coordinate bond.

The present invention provides a process for the synthesis of poly(AA-co-DVB) using cyclohexanol as a porogen at different crosslink densities and its modification with Lewis acid comprising:

a. conducting suspension polymerization by adding the oil phase comprising allylamine, divinylbenzene, 2,2'-azobisisobutyronitrile, and cyclohexanol (porogen) to the suspension reactor containing poly(vinylpyrrolidone) as a protective colloid solution (in distilled water) with constant stirring to obtain the reaction mixture;

b. heating the reactor to carry out the polymerization and obtain the product in the form of beads which on purification affords the copolymer in 70- 80% yields;

c. adding Lewis acid solution (in ethanol) to polymer of step (b), to obtain the modified polymer which on washing and drying affords the polymer modified Lewis acid.

The above process for the synthesis of poly(AA-co-DVB) and its modification with Lewis acid is shown in Scheme 1. The present invention provides a process wherein Lewis acids used is preferably selected from aluminum chloride (A1C1₃) or stannous chloride (SnCl₂). The present invention provides a process for the synthesis of polyimine using poly(AA-co-DVB) supported AlCl₃/SnCl₂ catalyst comprising the steps of:

a. mixing 4,4'-diacetylbiphenyl, N-methyl-2-pyrrolidone, poly(AA-co-DVB) supported A1C1₃ or SnCl₂ and stirring followed by addition of para phenylene diamine and further stirring at 100°C to obtain the reaction mixture;

b. On completion of reaction time, filtering the reaction mixture of step (a) to recover polymer-supported AICI3 or SnCl₂ and adding methanol to the filtrate to form precipitate which on filtration, washing, and drying furnishes the desired product.

The above process is shown in Scheme 2.

In an aspect, the present invention provides polymer-supported catalyst which is thermostable and useful for high temperature reactions.

In a preferred aspect the present invention provides polymer-supported catalyst with thermostability up to 400°C and glass transition temperature up to 240°C.

In another aspect the present invention provides polymer-supported catalyst which is useful to recover, recycle, and reuse of the catalyst which make the process environmentally benign and industrially economical.

In yet another aspect, the swelling behavior of the polymer-supported catalyst was also examined for different solvents to decide the compatibility of polymer with solvent.

In still another aspect, the present invention provides a polymer with more loading of Lewis acid catalyst as well as to avoid the catalyst leakage during application. EXAMPLES

The following examples are given by way of illustration and therefore should not ne construed to limit the scope of the invention.

GENERAL

The polymers obtained by suspension polymerization were purified by soxhlet extraction method to remove unreacted and adsorbed reaction composition. Fourier transform infrared (FT-IR) spectra were recorded on Perkin Elmer spectrophotometer having model spectrum GX. The samples for FTIR were prepared after drying the polymers at 80°C for 8 h. Surface area of polymer was determined by nitrogen adsorption/desorption isotherm (BET method) using surface area analyzer NOVA 2000e, Quantachrome. Furthermore, average particle diameter was determined using an Accusizer 780 (model LE 2500-20) PSS.NICOMP Particle sizing system, Santa Barbara, California, USA. Amine content of unmodified polymer was determined by acetic anhydride in pyridine, titrimetrically. Thermal stability (TGA) of polymers was studied by simultaneous thermal analysis (STA, Perkin Elmer) while glass transition temperature was evaluated using differential scanning calorimetry Q10 (Thermal analysis). Swelling ratio of polymers was determined by wt/wt ratio. Scanning electron microscopy (SEM) was used for external morphology and particle visualization which were performed by Quanta 200-3D, dual beam ESEM microscope wherein electron source was thermionic emission tungsten filament.

Example 1

Suspension polymerization was carried out in a double walled cylindrical glass reactor maintained at a constant temperature, equipped with a condenser, nitrogen inlet, and overhead stirrer. The oil phase comprising 11.147 g (0.195 mol) of allylamine, 1.271 g (0.01 mol) of divinylbenzene, 2.5 mol% of 2,2'- azobisisobutyronitrile, and 48 mL of cyclohexanol (porogen) were added to the suspension reactor containing 1 wt% of poly(vinylpyrrolidone) as a protective colloid dissolved in 200 mL of distilled water with constant stirring speed of 500 rotations per min. After complete addition of the oil phase to the aqueous phase, the temperature of the reactor was raised to 70°C and maintained for 3 h to carry out the polymerization. On completion of the reaction time product obtained in the form of beads was cooled, filtered, and washed several times with water, methanol, and dried in oven at 60°C under reduced pressure for 8 h. Poly(AA-co-DVB) at different crosslink densities were synthesized by suspension polymerization using cyclohexanol as a porogen. Monomer-crosslinker feed composition is illustrated in Table 1. Concentration of monomer and crosslinker was determined by equation 1. where, A is the batch size, M is the monomer, C is the crosslinker, CLD is the crosslink density, and X is the determination factor.

Table 1: Feed composition of allylamine and divinylbenzene at different crosslink density

Reaction conditions: Batch size: 16 mL, 2,2'-azobisisobutyronitrile (AIBN): 2.5 mol%, stirring speed: 500 rpm, reaction time: 3 h, outer phase: H₂0, protective colloid: poly(vinylpyrrolidone), concentration of protective colloid: 1 wt%, porogen: cyclohexanol; porogen concentration - 48 mL (monomenporogen ratio, 1 :3 v/v).

Purification of the polymer

Polymers obtained by suspension polymerization were purified by soxhlet extraction method to remove low molecular weight polymer and unreacted ingredients. Methanol was used as an extracting solvent since unreacted monomer, adsorbed PVP, and porogen are soluble/miscible in methanol. One Liter of distilled methanol was added in round bottom flask of soxhlet apparatus. Subsequently, polymer beads were packed in whatmann paper, placed in soxhlet apparatus, and methanol was refluxed. After 5 methanol cycles, polymer was filtered and again washed with methanol. Later on, polymer beads were dried at 60°C under reduced pressure.

FT-IR spectroscopy

Synthesis of poly(AA-co-DVB) was confirmed by FT-IR (KBr, cm^"1) spectrometer. FT-IR spectrum illustrates the presence of primary amine (3367), aliphatic C-H str. (2937), methyl C-H asymmetric bending (1455), aromatic C-H out-of-plane bending (906 and 797), and disubstituted ring at para position (832). Moreover, polymer modified Lewis acid revealed that, A1C1₃ (1603, 1446) and SnCl₂ (1603, 1447) peak corresponds to Lewis acids in addition to base polymer peak. FT-IR spectra of unmodified and modified polymers are shown in Fig. 1.

Amine content determination

The amine content determination is the polymer reactivity measurement and was evaluated by using acetic anhydride in pyridine, titrimetrically. It was observed that, amine content was decreased with increase in crosslink density. This is mainly due to concentration of allylamine was decreased with increase in crosslink density of polymer. Observed amine content was lower than theoretical due to large number of amine functionality are buried into the polymer matrix and are not available for titrimetric determination. Amine content (theoretical and observed) of crosslinked base polymer is reported in Table 2. Table 2: Amine content (theoretical and observed) of unmodified base polymer

Particle size determination

Polymer having CLDs 5, 10, 15, 20, and 25% were synthesized using suspension polymerization and purified by soxhlet extraction was used for particle size analysis. Average particle size of base polymer and polymer-supported Lewis acid were characterized by an Accusizer 780 (model LE 2500-20). It was observed that, particle size was slightly decreased with increase in crosslink density. Perhaps this is due to highly crosslinked polymer has strong bonding between monomer and crosslinker. Moreover, polymer modified Lewis acid demonstrated the slight increase in average particle size for all crosslink density polymers. The average particle size of base and polymer-supported Lewis acid is depicted in Fig. 2. Thermogravimetric analysis

Nowadays, Lewis acids are tremendously used in different organic reactions such as alkylation and acylation at room as well as high temperature reactions. The temperature depends on the reaction conditions. Thermogravimetric analysis was carried out from 250 - 700°C in a nitrogen atmosphere. The use of polymer-supported catalyst at high temperature requires the evaluation of thermal stability of polymer matrix. As a result, thermogravimetric analysis plays an important role. Unmodified and modified polymer, showed the decomposition temperature (°C) of ADC (447, 435), ADC A (448, 435), and ADCS (448, 444) for 5% and 25% crosslink density, respectively. DTG thermograms of base and polymer-supported Lewis acids are reported in Fig. 3.

Differential scanning calorimetry

Differential scanning calorimetry (DSC) of polymer is also a crucial parameter. DSC study of unmodified polymer and polymer modified Lewis acid was performed using DSC Q10. Differential scanning calorimetry was carried out in the temperature range of 50-400°C in a nitrogen atmosphere. This study demonstrated that, glass transition temperature (Tg) of base polymer was decreased with decrease in CLD. Glass transition temperature (°C) reveals that, Tg of ADC (414, 405), ADCA (256, 249) and ADCS (402, 393) for 5% and 25% crosslink density, respectively. It was observed that, Tg of polymer was decreased after modification with Lewis acid. Undoubtedly, the use of polymer below Tg can provide better results. Polymer used at or above Tg perhaps make interaction with reactant or reaction medium and influences the product purity. DSC thermograms of base polymer and polymer-supported Lewis acid are depicted in Fig. 4.

Swelling ratio

Swelling ratio provides a suitable solvent for solid phase synthesis. Base polymer and polymer-supported Lewis acid demonstrated the higher swelling for low crosslink density polymer. As a result, low crosslink density polymer-supported Lewis acid is useful as a catalyst in organic reactions. This is mainly due to the low crosslink density polymer reveals higher swelling as well as more reactivity tends to more catalyst loading. Solubility parameter was used to calculate polymer-solvent interaction parameter. Generally, each solvent can swell the polymer to a certain extent. This extent of swelling depends on the solubility parameter of polymer and swelling solvent, polymer-solvent interaction parameter, and degree of crosslinking of polymer. Solubility parameter of polymer (calculated) and swelling solvents (referred) are reported in Table 3.

The calculated polymer-solvent interaction parameter is reported in Table 4. Subsequently, degree of swelling (Ds) was calculated by the following mass swell ratio equation 2. d (2) where, Ds is the degree of swelling, Ws is the weight of swollen polymer at a given time, and W_d is the weight of a dried polymer.

Swelling measurements were carried out by storing 0.5 g of polymer matrix in 20 mL of ethanol/acetonitrile/l,4-dioxane at room temperature for 24 h to attain equilibrium swelling. Swelling ratio of crosslinked polymer was determined by measuring the weight of the polymer after equilibrium swelling in a solvent (W_s) and after drying (W_d) of polymer.

Swelling ratio was measured as a function of polymer-solvent interaction parameter and crosslink density. Solubility parameter difference of poly(AA-co-DVB) and 1,4- dioxane is smaller and difference was increased for acetonitrile and further for ethanol. Swelling behaviour of a polymer is in accordance to solubility parameter difference between polymer and swelling solvent. It was observed that, smaller the polymer-solvent interaction parameter more is the swelling of polymer and vice-versa. Results demonstrate that, swelling ratio is dependent on the crosslink density. Swelling ratio was lower for higher crosslink density polymer. This is because small chains in a high crosslink density polymer make it difficult to swell the copolymer whereas high crosslink density polymer has long chain length that expands to swollen polymer. Swelling ratio is thus a measure of crosslink density of a polymer. Degree of swelling (Ds) is represented in Fig. 5. Table 3: Solubility parameter of polymer and different swelling solvents

Table 4: Polymer-solvent interaction parameter

Scanning electron microscopy

Scanning electron microscopy (SEM) images of base polymer and polymer-supported Lewis acids were scanned for 5% and 25% crosslink density with 2500X magnification. For this, polymer beads were mounted on grid and placed below electron beam to observe the surface morphology of polymers. It is worth noting that, external morphology revealed the porous nature of polymer beads before and after modification with Lewis acid. SEM images of base polymer and polymer-supported Lewis acid is represented in Fig. 6.

EDX analysis

Energy dispersive X-ray (EDX) analysis of base polymer and polymer-supported Lewis acid was evaluated by Quanta 200-3D, dual beam ESEM microscope with thermionic emission tungsten filament as an electron source. It was observed that, base polymer contains carbon and nitrogen only. However, polymer-supported Lewis acid demonstrated the presence of aluminium, tin, and chlorine in their respective copolymers. It was also observed that, percentage of aluminium and tin was lower with high crosslink density polymer. Results revealed that, the presence of aluminium (10 wt%/5.18 at%) and tin (33.02 wt% / 5.30 at%) at 5% cross-link density. Hydrogen in the polymer was not detected due to instrument limitation. EDX analysis of base and polymer-supported Lewis acid in wt% and at% is represented in Fig. 7. EXAMPLE 2

Suspension polymerization was carried out in a double walled cylindrical glass reactor maintained at a constant temperature, equipped with a condenser, nitrogen inlet and overhead stirrer. The oil phase comprising 10.256 g (0.180 mol) of allylamine, 2.339 g (0.018 mol) of divinylbenzene, 2.5 mol% of 2,2'-azobisisobutyronitrile, and 48 mL of cyclohexanol (porogen) were added to the suspension reactor containing 1 wt% of poly(vinylpyrrolidone) as a protective colloid dissolved in 200 mL of distilled water with constant stirring at 500 rotations per min. After complete addition of the oil phase to the aqueous phase, the temperature of the reactor was raised to 70°C and maintained for 3 h to carry out the polymerization. On completion of the reaction time the product obtained in the form of beads was cooled, filtered, and washed several times with water, methanol, and dried in oven at 60°C under reduced pressure for 8 h.

EXAMPLE 3

Suspension polymerization was carried out in a double walled cylindrical glass reactor maintained at a constant temperature, equipped with a condenser, nitrogen inlet and overhead stirrer. The oil phase comprising 9.496 g (0.166 mol) of allylamine, 3.248 g (0.025 mol) of divinylbenzene, 2.5 mol% of 2,2' azobisisobutyronitrile, and 48 mL of cyclohexanol (porogen) were added to the suspension reactor containing 1 wt% of poly(vinylpyrrolidone) as a protective colloid dissolved in 200 mL of distilled water with constant stirring at 500 rotations per min. After complete addition of the oil phase to the aqueous phase, the temperature of the reactor was raised to 70°C and maintained for 3 h to carry out the polymerization. On completion of the reaction time the product obtained in the form of beads was cooled, filtered, and washed several times with water, methanol, and dried in oven at 60°C under reduced pressure for 8 h. EXAMPLE 4

Suspension polymerization was carried out in a double walled cylindrical glass reactor maintained at a constant temperature, equipped with a condenser, nitrogen inlet and overhead stirrer. The oil phase comprising 8.842 g (0.155 mol) of allylamine, 4.033 g (0.031 mol) of divinylbenzene, 2.5 mol% of 2,2' azobisisobutyronitrile, and 48 mL of cyclohexanol (porogen) were added to the suspension reactor containing 1 wt% of poly(vinylpyrrolidone) as a protective colloid dissolved in 200 mL of distilled water with constant stirring at 500 rotations per min. After complete addition of the oil phase to the aqueous phase, the temperature of the reactor was raised to 70°C and maintained for 3 h to carry out the polymerization. On completion of the reaction time the product obtained in the form of beads was cooled, filtered, and washed several times with water, methanol, and dried in oven at 60°C under reduced pressure for 8 h.

EXAMPLE 5

Suspension polymerization was carried out in a double walled cylindrical glass reactor maintained at a constant temperature, equipped with a condenser, nitrogen inlet and overhead stirrer. The oil phase comprising 8.271 g (0.145 mol) of allylamine, 4.716 g (0.036 mol) of divinylbenzene, 2.5 mol% of 2,2' azobisisobutyronitrile, and 48 mL of cyclohexanol (porogen) were added to the suspension reactor containing 1 wt% of poly(vinylpyrrolidone) as a protective colloid dissolved in 200 mL of distilled water with constant stirring at 500 rotations per min. After complete addition of the oil phase to the aqueous phase, the temperature of the reactor was raised to 70°C and maintained for 3 h to carry out the polymerization. On completion of the reaction time the product obtained in the form of beads was cooled, filtered, and washed several times with water, methanol, and dried in oven at 60°C under reduced pressure for 8 h. The yield of the copolymer was 70-80% for different crosslink density.

EXAMPLE 6

Soxhlet purified polymer was used for modification with Lewis acid (A1C1₃). Poly(AA-co-DVB) having crosslink densities of 5, 10, 15, 20, and 25% were used for modification with AICI3. Lewis acid (AICI3_, 5 g) was dissolved in 50 mL of ethanol and placed at room temperature for 2 days for complete dissolution of Lewis acid. ADC (5% to 25% crosslink) polymer (2 g) was weighed in a glass vial. To this, above Lewis acid solution (10 mL of A1C1₃ solution in ethanol) was added to each crosslink density polymer. Then, these modified polymers were placed for 2 days to obtain the uniform polymer modification. Subsequently, polymers were washed with ethanol for 3 - 4 times to remove unreacted Lewis acid and dried at 70°C under reduced pressure. Dried polymers were used for characterization.

EXAMPLE 7

Soxhlet purified polymer was used for modification with Lewis acids (SnCl₂). Poly(AA-co-DVB) having crosslink densities of 5, 10, 15, 20, and 25% were used for modification with SnCl₂. Lewis acid (SnCl_2; 5 g) was dissolved in 50 mL of ethanol and placed at room temperature for 2 days for complete dissolution of Lewis acid. ADC (5% to 25% crosslink) polymer (2 g) was taken separately in a glass vial, to this above Lewis acid solution (10 mL of SnCl₂ solution in ethanol) was added to each crosslink density polymer. Then, these modified polymers were placed for 2 days to obtain the uniform polymer modification. Subsequently, polymers were washed with ethanol for 3 - 4 times to remove unreacted Lewis acid and dried at 70°C under reduced pressure. Dried Polymers were used for characterization. EXAMPLE 8

Applications poly(AA-co-DVB) supported AICI3/S11CI₂ in polymerization

A 100 mL of three necked flask was equipped with constant temperature oil bath, mechanical stirrer, and nitrogen gas inlet. In this, 4,4'-diacetylbiphenyl (1 g, 4.1967 mmol), N-methyl-2-pyrrolidone (5 mL), and poly(AA-co-DVB) supported AlCl₃/SnCl₂ (1 g) was added and stirred for 10 min. Subsequently, /?ara-phenylene diamine (0.454 g, 4.1967 mmol) was added and stirred for additional 3 h at room temperature (25°C). After completion of reaction time, reaction mixture was filtered to recover polymer-supported AlCySnC . Methanol was added to the filtrate and placed for overnight to obtain precipitate. Precipitate was filtered, washed with methanol, and dried at 70°C for 8 h under reduced pressure. Yield of the product was 1.31 g, 90.1%). Recovered polymer-supported catalyst can be used for next cycle. Synthesis of polyimine was confirmed by 1H MR (200 MHz, CDCI₃+TMS) δ 8.04 - 8.08 (8H, d) δ 7.70 - 7.74 (8H, d) δ 2.65 (6H,S). Further, - H₂ peak is absent which confirm the successful synthesis of polyimine. 1H MR (CDCI₃+TMS, 200 MHz) of polyimine is represented in Fig. 8. Thermal study was also carried out to confirm the polymer thermostability. Differential thermogravimetric (DTG) analysis was performed by simultaneous thermal analysis (Perkin Elmer) in the temperature range of 50-650°C in nitrogen atmosphere. Thermal property evaluation demonstrated that, polyimine has maximum decomposition temperature (Tmax) of 291°C and is illustrated in Fig. 9. ADVANTAGES OF THE INVENTION

a. The hydrophobic polymer-supported Lewis acid can be used in anhydrous reaction.

b. The hydrophobic polymer-supported Lewis acid has wide applications in different organic transformations for number of cycles because of recovery, recycle, and reusable properties.

c. Small amount of polymer-supported Lewis acid is sufficient for an organic reaction since high loading of catalysts, leading to industrially economical process.

Claims

The claims

1. A hydrophobic poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst comprising poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] in the range of 60 to 90 wt% and Lewis acid in the range of 10 to 40wt%.

2. A process for the synthesis of hydrophobic poly(AA-co-DVB) supported Lewis acid catalyst comprising the steps of:

3. The process as claimed in claim 1, wherein Lewis acids used is selected from aluminium chloride or stannous chloride.

4. The hydrophobic poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst as claimed in claim 1, wherein said catalyst is thermostable upto 400°C and useful for high temperature reactions.

5. The hydrophobic poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst as claimed in claim 1, wherein said catalyst exhibit glass transition temperature upto 240°C.

6. The hydrophobic poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst as claimed in claim 1, wherein said catalyst is recyclable and reusable.

7. The hydrophobic poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst as claimed in claim 1, wherein said catalyst is useful to avoids the catalyst leakage during organic transformations.

8. The hydrophobic poly(Allylamine-co-divinylbenzene) [poly(AA-co-DVB)] supported Lewis acid catalyst as claimed in claim 1, wherein said catalyst is useful in an organic synthesis and functional group transformation.

9. A process for the synthesis of polyimine using the catalyst as claimed in claim 1, and the said process comprising the steps of:

a. mixing 4,4'-diacetylbiphenyl, N-methyl-2-pyrrolidone and poly(AA-co- DVB) supported Lewis acid catalyst followed by stirring and adding para phenylene diamine and stirring to obtain the reaction mixture;

b. filtering the reaction mixture as obtained in step (a) to recover poly(AA- co-DVB) supported Lewis acid catalyst and adding alcohol to the filtrate to form precipitate which on filtration, washing, and drying furnishes the desired product polyimine.

10. The process as claimed in claim 9, wherein alcohol used is preferably ethanol.