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Chapter – 2

Synthesis and characterization of

azo-salicylic acid-formaldehyde

oligomers

[PSA-1 to PSA-4]

Chapter-2

Synthesis and characterization of

azo-salicylic acid-formaldehyde oligomers

[PSA-1 to PSA-4]

2.1 Introduction

The present chapter deals with the synthesis and characterization of assorted azo- 2-

hydroxybenzoic acid – methanal oligomers i.e. PSA-1 to PSA-4. Whole chapter was divided into two

sections. Section A: included synthesis of various azo-Salicylic acid – formaldehyde oligomers i.e. PSA-1

to PSA-4, Their preparation and structures based on reactive sites have also been proposed and section B:

describe characterization of various azo-Salicylic acid - formaldehyde oligomers i.e. PSA-1 to PSA-4.

2.2 Synthesis of salicylic acid-formaldehyde oligomer

2.2.1 Introduction

Thermosetting polymers, sometimes called resins in the industry, can be found everywhere in our

environment (shoe soles, electric appliances parts, light switches, foundry refractory brick, and

adhesives). Thermosetting polymers, as

their name implies, polymerize, in a mostly irreversible manner, with the application of heat. One of the

oldest thermoset known, discovered by Leo Bakeland in the early 1900', [115] is phenol-formaldehyde or

PF, also known as a novolac (acid cured) or resol (base cured). PF are widely used as adhesives in the

wood composite (particleboard or plywood) industry [116]. If one examines, for instance a plywood

sheet, it is possible to see the adhesiveas a thin brownline between each successive veneer sheet. The

following procedure allows for the synthesis of a 50% aqueous solution of a prepolymer, which can be

used to bind wood or other materials together, with proper application of heat and pressure.

The phenol-formaldehyde polymers ar the oldest business artificial polymers, 1st introduced

around one hundred years past. Their artificer, Leo Bakeland, had no plan what was happening in his

reaction kettles, however he was ready to calculate conditions to supply a troublesome, light, rigid, with

chemicals resistant solid from 2 cheap ingredients. He presently became a chic man, within the same

category because the renowned industrialists of the time like Nobel, Henry Ford, Andrew Carnegie,

industrialist, etc.

The actual chemistry is difficult, and still not utterly understood. The polymers ar typically

thermosetting (i.e., cross linked), and their quality limits the analytical techniques which will be dropped

at bear. the most reaction is that the production of methylene group bridges between aromatic rings, as

shown below. several aspect reactions additionally occur, and a few of those offer phenol-formaldehyde

chemical compound its dark color. Of course, these cross coupled polymers can not be liquid or

dissolved, therefore their synthesis should be conducted in molds for the particular product. In follow, the

polymerisation is sometimes distributed to somewhere below the gel purpose during a separate reactor,

and so the "pre-polymer" is transferred to the mould, wherever the reaction is completed.

There are two steps in the formation of the polymer. The first is the methylolation, where

formaldehyde adds to the phenol.

C6H5OH CH2O C6H4OH(CH2OH)+

to form methylolphenol, in associate chemical reaction. The second step involves condensation of phenol

with a methylolphenol unit with the assembly of water molecule to create a group bridge between the

unsaturated rings:

C6H5OH H2OC6H4OH(CH2OH) + (C6H4OH)2CH2 +

This reaction is endothermic. This last molecule may also be methylolated again by formaldehyde

and form new methylene bridges with others. Thus a polymer is formed. Since all three ortho and para

sites on the phenol molecule are susceptible to react, pushing reaction 2 to its limit, i.e., continuing to heat

the mixture for too long time, will result in the resin curing, that is, forming a gel, and then a glass,

preferably outside the reaction flask, since the cure reaction is irreversible, due to the nearly infinite

viscosity of the final resin.

Same as phenol-formaldehyde oligomer, new oligomers like Salicylic acid-Formaldehyde

oligomer and its derivatives ar referred to as ion-exchanges. Literature survery reveals that such Salicylic

acid-Formaldehyde compound (SF) sort oligomers haven't been used as dyestuff couples. this may afford

for novel coloured ion-exchanges with sensible thermal stability. therefore the current chapter contains

the synthesis and characterization of novel ion-exchange rosin i.e. azo containing Salicylic acid –

formaldehyde oligomers. Perusal of the literature reveals that such Salicylic acid-Formaldehyde

compound oligomers haven't been applied as dyestuff coupling. The work describe within the gift

communication is in reference to the synthesis and characterization of a dyestuff supported salicylic acid-

methanal oligomers. 2.2.2 Experimental Synthesis of oligomeric 2-

hydroxybenzoic acid-formaldehyde organic compound by condensation of salicylic acid with gas

was established by varying the mole ratio of reactants, catalysts, solvents, temperature etc. Azo coupling

to oligomeric salicylic acid-formaldehyde resin done by first prepared diazonium salt of aniline, 4-chloro

aminobenzine, 4-methyl aminobenzine and 4-methoxy aminobenzine and matched with salicylic acid-

formaldehyde organic compound.

2.2.3 Materials Salicylic acid and Paraformaldehyde used were analytical grade.

2.2.4 Synthesis of hydroxy acid –formaldehyde oligomer

A mixture of hydroxy acid (69 gm, 0.5 mole), 37% formaldehyde solution (35 ml, 0.4 mole) and 60 ml

40% sulfuric acid was refluxed with smart stirring at 125-1300C for six hours. throughout this point, the

solid chemical compound was shaped. The solid was filtered, washed with an outsized quantity of water

and so with boiling water. The dry compound sample was soxhlet extracted with aromatic hydrocarbon to

get rid of unreacted compound. The compound sample was dissolved in 1:1 mixture of dissolver and plant

product and reprecipitated as a pasty mass by adding water. The pasty mass was washed by decantation

and picked up. The mass was dissolved in dilute alkali and reprecipitated by gradual addition of 1:1 conc.

HCl-water mixture with stirring. The compound sample failed to soften up to 3600C the yield was forty

gms.

2.2.5 Results and discussion

The salicylic acid-formaldehyde oligomer was obtained as a off white to light yellowish colored solid, It

was miscible with most of common organic solvents. The C, H and N contents of oligomer were in

agreement with the structure foretold. This was additionally confirmed by IR spectrum that shows bands

at 2920, 2850cm-1 as a result of CH2 , 1650 cm-1 as a result of –COOH cluster and 3350 cm-1 as a result

of -OH cluster. many bands within the covalent bond region arised from aromatics. The Mn calculable

each by VPO and non-aqueous conductometric volumetric analysis were comparable and was regarding

453. The results also indicated that the degree of polymerization of oligomer was 3. Based on results of

elemental analysis, IR spectral features and Mn of oligomer, proposed structure of oligomer would be:

OH

COOH

CH2

3

Salicylic-formaldehyde oligomer

2.2 Synthesis of azo-salicylic acid-formaldehyde oligomers

[PSA-1 to PSA-4].

2.3.1 Materials

Aniline, 4-chloro aminobenzine, 4-methyl aminobenzine and 4-methoxy aminobenzine

used was of analytical grade were used as a pure grade. All different chemicals used were of

laboratory grade.

2.3.2 Synthesis of azo-salicylic acid-formaldehyde oligomer:

every of azo-salicylic acid-formaldehyde oligomer [PSA-1 to PSA-4] was synthesize by 1st

prepare cation salt of aniline oil, 4-chloro aniline oil, 4-methyl aniline oil, 4-methoxy aniline

oil and paired with salicylic acid-formaldehyde oligomer.

(a) Synthesis of azo-salicylic acid-formaldehyde oligomer i.e. PSA-1

To a well stirred cation salt answer of amine (0.1mole) was slowly superimposed to AN

alcalescent answer of salicylic acid-Formaldehyde oligomer (0.1mole) at pH eight.5-9.0 at zero-

50 C temperature. The resultant answer was stirred for two hours. The dye was precipitated by

adjusting the pH close to concerning vi.0. The precipitated dye i.e. PSA-1 was filtered off,

washed with water and dry. the anticipated structure and formation of oligomeric substance is

shown in Scheme-2.1.

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

NH2N N Cl

N N Cl

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

N N

+

(Oligomeric Ligand PSA-1)

n


+ NaNO2 2HCl+0-50C

Benzene diazoniumchloride

+ +NaCl 2H2O


n

Azo-Salicylic-formaldehyde oligomer

Scheme 2.1 azo-salicylic acid-formaldehyde oligomer

(a) Synthesis of azo-salicylic acid-formaldehyde oligomer

i.e. PSA-2

To a well stirred Diazonium salt solution of 4-chloro aniline (0.1mole) was slowly adscititious to

associate base-forming resolution of salicylic acid-Formaldehyde oligomer (0.1mole) at pH eight.5-9.0 at

zero-50 C temperature. The resultant resolution was stirred for two hours. The dye was precipitated by

adjusting the pH close to concerning vi.0. The precipitated dye i.e. PSA-2 was filtered off, washed with

water and dry. the anticipated structure and formation of oligomeric matter is shown in Scheme-2.2.

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

NH2

Cl

N N Cl

Cl

N N Cl

Cl

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

N N

Cl

+


n


+ NaNO2 2HCl+0-50C

p-Chloro Benzenediazoniumchloride

+ +NaCl 2H2O


n



(b) Synthesis of azo-salicylic acid-formaldehyde oligomer

i.e. PSA-3 To a well stirred Diazonium salt solution of 4-methyl aniline (0.1mole)

was slowly intercalary to AN alcalescent answer of salicylic acid-Formaldehyde

oligomer (0.1mole) at pH eight.5-9.0 at zero-50 C temperature. The resultant answer

was stirred for two hours. The dye was precipitated by adjusting the pH close to

concerning six.0. The precipitated dye i.e. PSA-3 was filtered off, washed with water

and dry. the anticipated structure and formation of oligomeric matter is shown in

Scheme-2.3.

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

NH2

CH3

N N Cl

CH3

N N Cl

CH3

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

N N

CH3

+


n


+ NaNO2 2HCl+0-50C

p-Methyl Benzenediazoniumchloride

+ +NaCl 2H2O


n

Azo - Salicylic-formaldehyde oligomer


(c) Synthesis of azo-zalicylic acid-formaldehyde oligomer

i.e. PSA-4

To a well stirred cation salt answer of 4-methoxy aminobenzine (0.1mole) was slowly adscititious

to associate degree alkalic answer of salicylic acid-Formaldehyde oligomer (0.1mole) at pH scale eight.5-

9.0 at zero-50 C temperature. The resultant answer was stirred for two hours. The dye was precipitated by

adjusting the pH scale close to concerning half-dozen.0. The precipitated dye i.e. PSA-4 was filtered off,

washed with water and dry. the anticipated structure and formation of oligomeric matter is shown in

Scheme-2.4.

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

NH2

OMe

N N Cl

OMe

N N Cl

OMe

OH

COOH

CH2

OH

COOH

CH2

OH

COOH

N N

OMe

+


n


+ NaNO2 2HCl+0-50C

p-Methoxy Benzenediazoniumchloride

+ +NaCl 2H2O


n



2.3 Characterization of azo-salicylic acid-formaldehyde oligomer.

The present section deals with the characterization of azo containing salicylic acid –

formaldehyde oligomer PSA-1 to PSA-4 by

(I) Elemental analysis,

(II) IR Spectral studies,

(III) Determination of range average mass of oligomeric ligands

(IV) Thermo gravimetric Analysis and,

(V) Determination of azo group.

2.4.1 Elemental analysis

All the azo containing salicylic acid – formaldehyde oligomer PSA-1 to PSA-4

synthesized and described in an earlier section were analysed by their elemental contents. The C,

H and N elements of all the samples were measured by Elemental instrument Thermofiniggan

Flash, 1101 EA.

the fundamental contents of all four oligomeric ligands square measure given in Tables two.1.

The examination of the info reveals that the worth of C, H and N of all the ligands is in step with

the structure foretold in section-2.3.2

Table 2.1 Characterization of oligomeric Ligands PSA-1 to PSA-4.

Sr.

No.

Ligand

No.

Molecular

Formula

Mol.Wt.

Gm/

Mole

Yield

%

Elemental Analysis

% C % H % N

Cal. Found Cal. Found Cal. Found

1 PSA-1 C29H22N2O9 542 75 64.20 64.10 4.05 4.00 5.16 5.15

2 PSA-2 C29H21N2O9Cl 576.5 74 60.36 60.30 3.64 3.70 4.85 4.85

3 PSA-3 C30H24N2O9 556 73 64.74 64.70 4.31 4.30 5.03 5.00

4 PSA-4 C30H24N2O10 572 74 62.93 62.90 4.19 4.15 4.89 4.90

2.4.2 Infrared Spectroscopy

The atoms of a molecule behave as if they were connected by flexible spizings, rather

than by rigid bound resembling the connectors of a ball and stick model. Their component parts

can oscillate in different vibrational modes, designed by such terms as rocking, scissoring,

twisting, wagging and symmetrical and asymmetrical stretching. When inform red radiation is

passed through a sample of a given compound its molecules can absorb radiation of the energy

(and frequency) needed to bring about transition between vibration ground states and vibration

excited states.

2.4.2(I) Experimental

Infrared scanning for the ligands were made in the range 4000-600cm-1 in KBr. AR grade

KBr was used for this purpose. It was first fused, powdered and dried in vacuum. The absence of

moisture in this dried KBr pellet was checked by scanning the IR spectra of purified KBr. Then

the pellet of KBr with polymer was prepared as under.

A mixture of 4mg of pure dried sample and 1 gm KBr powder was ground in a mini ball

mill for about 10 minutes. The resulting mixture was placed on the disc and compressed at high

pressure about 20,000 psi giving the transparent pellet. The IR spectrum of this transparent pellet

was scanned on Nicolet FTIR-760 spectrophotometer.

2.4.2(II) Results and discussion

The anticipated IR spectral frequencies of all the radical containing salicylic acid-

formaldehyde oligomer area unit given in Table a pair of.2. The infrared spectra of oligomeric

ligands from PSA-1 to PSA-4 area unit shown in figures a pair of.1 to 2.4. The spectral

knowledge of all the oligomeric ligands area unit given in Table a pair of.3. The scrutiny of the

infrared spectra of all the oligomeric ligands reveals followings.

(I) All the IR spectra area unit identical in most aspects. The vital bands

area unit ascertained at their individual positions.

(II) The bands at 3030, 1600 and 820 cm-1 area unit principally from disubstituted

aromatic ring.

(III) The bands at 2780-2820 cm-1 area unit because of –CH2- linkage.

(IV) The sturdy band at 1630 cm-1 is from cluster|group|radical|chemical group} of –COOH

group.

(V) The band at 1406+14 cm-1 is because of –N=N- cluster.

Table-2.2

Anticipated IR spectral features for Ligands PSA-1 to PSA-4.

Sr.No. Groups IR frequencies(Cm-1)

1. Aromatic. 3050, 1600, 1010

2. -C=O of –COOH. ~1630

3. -CH2- 2500-2400

4. -N=N- 1392-1420

Figure 2.1 IR Spectrum of matter [PSA-1]

Figure 2.2 IR Spectrum of matter [PSA-2]

Figure 2.3 IR Spectrum of substance [PSA-3]

Table-2.3 IR Spectral knowledge of oligomeric ligands PSA-1 TO PSA-4

Sr.

No.

Oligomeric

Ligands

Frequencies cm-1

Azo [-N=N-] Aromatic C=O of COOH -CH2-

1 PSA-1 1419

3050

1630

1011

1529 2450

2 PSA-2 1434

3050

1608

1011

1630 2450

3 PSA-3 1430

3050

1630

1011

1628 2450

4 PSA-4 1430

3050

1635

1011

1630 2450

2.4.3 Determination of Number average molecular weight of oligomeric

ligands PSA-1 to PSA-4

Many methods have been developed for the estimation of molecular weight of polymers. For

example light scattering method, ultra centrifuge method, GPC, VPO, Non-aqueous conductometric

titrations, high speed membrane osmometry are well known.

In present case, high speed membrane osmometry could not be used because it is meant for high

molecular weight polymers and light scattering method is also. therefore VPO and non-aqueous

conductometric volumetric analysis ways used for the determination of oligomeric ligands i.e. PSA-1 to

PSA-4.

Molecular weight determination by non-aqueous conductometric volumetric analysis

it's been rumored that the relative molecular mass of an essentially linear polymer, which contains

–OH, -NH2 or –COOH group per each repeat unit be estimated by non-aqueous conductometric using a

proper titrating agent and a suitable medium. It has been shown that the manner in which the conductance

changes in the course of the titration suggests a method for the estimation of average degree of

polymerization [117-119].

Titrimetric work on linear phenol formaldehyde condensation products, in organic solvents

indicates a stepwise neutralization of acid group [–COOH] in the average chain [117]. It has been shown

that stepwise, neutralization of acid group [–COOH] groups in lower molecular weight polymers is

possible if solvent and titrant bases are properly chosen. They showed that very sharp end-points could be

obtained in the titration of acid compounds if tetra-n-butyl ammonium hydroxide is used in the titrant

base.

R. C. Degeiso and his co-workers [120] prepared salicylic acid-formaldehyde polymer (SF) and

estimated its weight average molecular weight (MW) by light scattering. These authors used solution of SF

polymer in ethanol for these experiments and found the weight average molecular weight of the given SF

polymer was about 6000.

However, these are reports about the application of non-aqueous titration in the estimation of

molecular weights of phenol-formaldehyde type polymers and also of polymers containing –COOH or –

NH2 in the repeat unit of polymer chains. A brief account of titrations of such polymers in non-aqueous

media has been presented.

Both potentiometric and conductometric titrations in non-aqueous media against proper standard

reagent have been employed in estimation of molecular weight (Mn) of polymers containing phenolic –

OH group, amino group or –COOH group in the repeat units. Such polymers are called poly-phenol, poly-

amine and poly-carboxylic acid respectively. The basic requirement is that the polymer should dissolve in

a suitable solvent capable of enhancing its acid or basic character as the case may be. Suitable solvent for

poly phenols and poly carboxylic acids is pyridine. For polyamines suitable solvent is formic acid or

glacial acetic acid. Conductometric or potentiometric titration of a poly phenol or poly carboxylic acid

have been carried out in alkali against customary atomic number 11 methoxide or characin fish radical

ammonia in alkali [121, 122, 123].

Experimental and calculations

(a) 0.05 ml up to 1.0 ml,

(b) 0.10 ml up to 3.0 ml

(c) 0.20 ml up to the end point

The conductance was measured on a METROHM KONDUCTOSKOP E 365 Switzerland. About

1.0 to 2.0 min. time lapse was allowed after each addition of sodium methoxide solution and before

addition of new lot of the titrant.

For a resin of the general structure the reaction will be 1.0 equivalent of the sample would require

1.0 equivalent (1000 milli equivalents) of the base for complete neutralization. Since out of the two

hydroxyl groups present on each repeat unit of resorcinol resin only one group will be neutralized. Hence

total mill equivalent of the base required to neutralized 100 gm of the liquid resin would be

1000 X 100

= ----------------------------------------------------------- = “Y”

Mol. Wt. of the repeat unit

Let ‘Y’ be the milli equivalent of the base used up in the shortest break (First break) in the titration curve.

Then, by principle, the degree of polymerization (P) would be

P = X / Y

and the range average relative molecular mass of the chemical compound would be

Mn = (P) X mass of the repeat unit

The plots of specific conductance against the volume of alkali were made and the values of P for

each phenolic oligomer were calculated. The values of degree of polymerization (P) are finished in Table

2.4.

Figure 2.4 Non-aqueous conductometric titration curve of Ligands PSA-1

Table 2.4 Non-aqueous conductometric titration of ligands PSA-1 to PSA-4

Solvent: anhydrous base

Reagent: 0.1 M Tetra-n-butyl ammonia in isopropyl alcohol (TBAH)

Sr.

No.

Oligomeric

ligands

Molecular weight

of repeating unit of

PSA oligomeric

ligands

Millimole of TBAH

required to

neutralized per 100

gm of sample (i.e.

Last break)

Millimole of

TBAH required

at 1st break of

titration curve

Degree of

polymerization

(P)

1 PSA-1 542 320 80 4.0

2 PSA-2 576.5 340 83 4.14

3 PSA-3 556 330 83 3.98

4 PSA-4 572 340 82 4.14

Results and discussion

The non-aqueous conductometric titration curves of each of four PSA oligomeric ligands

comprise the presence of 1st break of titration curve and last break , from these equation gives Degree of

polymerization (P).

The non-aqueous conductometric titration curves of each of four oligomeric ligands

comprise the presence of degree of polymerization (P) = 4.0.

2.4.4 Thermogravimetric study

2.4.4 (I) Introduction

The thermal ways typically utilized ar differential scanning measurement (DSC),

differential thermal analysis (DTA), thermohydrometric analysis (TGA) and derivatographic

analysis [124,125]. For comparative study of thermal behavior of related polymer or simple

molecules, each molecule is analyzed by any one or more of these methods of analysis under

identical experimental condition. For example TGA is carried out in air and in oxygen free

nitrogen. It is carried out at different heating rates. It may be method that the result of thermal

analysis of a given sample by a given method depends on various aspects. The amount and

particle size of the material being examined, influence the nature of the thermogram. The speed

of the recorder noting the change in weight and the shape of the sample container also influence

the thermogravimetric results. The rate of heating the sample and the ambient atmosphere during

analysis is very important factors to be controlled during thermal analysis. The information

furnished by TGA and DTA by DGA are to some extent complimentary. From the results of

DTA and TGA, it is possible it note the temperature up to which the material does not loss

weight. It is also possible to know the temperature at which material starts decomposing. It is

possible to know whether the decomposition occurs in one or more stages.

Besides the quantitative information derived on mere inspection of the thermogram, other

information about the order of the degradation reaction can be obtained by the analysis of the

thermal data furnished by either DTA or TGA.

The present aspect deals with the study of thermal properties of azo containing salicylic

acid-formaldehyde oligomer (PSA-1 to PSA-3 oligomeric ligands) sample which are presented

in section-2.3. The purpose of undertaking this work was to study thermal behavior of these

ligand samples in terms of decarboxylation.

2.4.4(II) Thermo gravimetric analysis

The thermal behavior of the ligand samples described in section-2.3 has been studied by

TGA. The loss in weight due to pyrolysis of the material with increase in temperature forms a

TG curve [125]. Normally the shape of the TG curve depends upon the nature of the in situ

degradation reaction of the sample. The analysis of these data by Broido method is often carried

out with a view to estimate kinetic parameters like energy of activation of the degradation

reaction [125].

The advantages of TGA are enumerated here [125, 126].

(I) A relatively small set of data is to be treated.

(II) Continuous recording of weight loss as a function of temperature ensures

Equal weightage to examination over the whole range of study.

(III) As a single sample is analysed over the whole range of temperature, the

variation in the value of the kinetic parameters, if any, will be indicated.

For the estimation of kinetic parameters, many ways ar utilized. All involve two

assumptions. It is assumed that the distinction within the thermal and diffusion processes is

negligible. it's additionally assumed that physicist relation is valid over the complete vary of

temperature. Since little materials ar utilized in TG analysis the barriers between the thermal and

diffusion processes ar quite negligible. thus it's cheap to ignore it. Besides it's cheap to assume

validity of physicist relation. [126]. Various methods are proposed to analyse the TG data

depending upon the nature of experimentation [126-133]. As the present study deals with simple

molecule. Hence attempt was not made for Application at these methods.

2.4.4(III) Experimental (TGA)

The thermohydrometric analyses (TGA) of sample are administered by victimization

“PERKIN ELMER PYRIS one TGA” in an exceedingly slow stream of air. The boat ready from

Pt foil would hold the sample for analysis. it's properly washed and dried. it absolutely was

suspended on the quartz rod within the TG balance. The pulverized sample (about five mg) was

placed within the boat. The sample within the boat is roofed by a quartz tube within which the

flow of air was maintained. The weight of sample was noted on TGA balance. the full assembly

was brought down within the chamber. it had been discovered that the boat was hanging on

quartz rod. The experiment was started by the heating the system at a continuing rate of

10°C/min. at the same time amendment within the weight was recorded mechanically with time

(temperature). this can reveal proportion weight loss of fabric s a perform of the time and also of

temperature. The experiment was stopped at about 650 °C, when there was no further decrease in

weight.

The thermograms were analyzed to obtain information about percentage weight loss at

different temperatures. The results of those analyses square measure bestowed in Table two.5.

elect themograms square measure shown in Figures two.5 to 2.7.

2.4.4(IV) Results and discussion The temporary account of the thermal behavior of oligomeric

ligands in air is given below:

(I) Examination of the TG curves of substance samples reveals that every of them

degrades in 2 steps.

(II) The initial stages of degradation up to 200° to 230°C of all the ligands indicate the load

loss within the vary at fifteen to twenty second percentages. this is often relying au courant the

relative molecular mass of sample

(III) The second stage at degradation of all the substances on the far side 200°c is speedy and

loss concerning seventy fifth to eighty fifth at 300°c relying upon the character of ligand.

(IV) All the ligands containing one –COOH teams. thence the TGA of ligands in air might

cause chemical process as rumored by Parekh [134]. The calculated worth of carbonic acid gas

of every ligands and naturally loss of 1st stage degradation of every ligands square measure

bestowed in Tables two.5. Examination of those information reveals that the dearboxylation of

every substance in keeping with the calculated values. of these facts ensure the structure of

oligomeric ligands.

Table-2.5

Sr.

No. Ligand

Wt loss at 1st stage of

degradation.

Calculated value of

decarboxylation

1 PSA-1 8.25 8.11

2 PSA-2 7.85 7.63

3 PSA-3 8.10 7.91

4 PSA-4 8.05 7.69

TGA Thermogram of Ligand-PSA-1

Figure-2.5


Figure-2.6


Figure-2.7

2.4.5 Determination of chemical group

The number of chemical group for all PSA-1 to PSA-4 oligomeric ligands were calculable by

methodology reported [135]. 35 mg. of sample was taken within the volumetric analysis flask

and dissolved in twenty five metric capacity unit. of diluted oil of vitriol (2:5 v/v) and

greenhouse gas gas was passed into it for five minutes to displace air. 20 ml. of 0.10 N titaneous

chloride answers was value-added into this air free solution. it absolutely was poached for five

minutes while maintaining the present of greenhouse gas. Cool the ensuing answer and add ten

metric capacity unit. of ammonium ion salt answer. it absolutely was titrated with customary

zero.10 N metal ammonium ion sulfate solutions. Blank set of twenty metric capacity unit. of

titaneous chloride answer was conjointly run.

Number of chemical group for every oligomeric substance sample was calculable by this

methodology indicates that there's one chemical group (-N=N-) gift within the molecule.

Examination of those knowledge reveals that there's one chemical group (-N=N-) gift within the

all oligomeric substance molecules.

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