The title terpolymer (8-HQ5-SAMF-IV) synthesized by the condensation of 8-hydroxyquinoline 5-sulphonic acid (8-HQ5-SA) and melamine (M) with formaldehyde (F) in the presence of acid catalyst and using varied 3 : 1 : 5 molar proportions of the reacting monomers. The synthesized terpolymer was characterized by different physicochemical techniques. The thermogravimetric analysis of terpolymer resin prepared in the present study has been carried out by nonisothermal thermogravimetric analysis technique in which sample is subjected to condition of continuous increase in temperature at linear rate. Thermal study of the resin was carried out to determine the mode of decomposition and thermal stability. Thermal decomposition curve was studied carefully with minute details. The Freeman-Carroll and Sharp-Wentworth methods have been used in the present investigation to calculate thermal activation energy and different kinetic parameter of the terpolymer resin. Thermal activation energy (
The synthesized terpolymer resins, showing versatile applications and properties, attracted the attention of scientist and introduced the recent innovations in the polymer chemistry. These terpolymers can be used as high-energy material [
The chemicals used in the synthesis of new terpolymer resin were procured from the market and were analar or Fulka or chemically pure grade. Whenever required, they were further purified by standard procedure.
The new terpolymer resin 8-HQ5-SAMF-IV was synthesized by condensing 8-hydroxyquinoline 5-sulphonic acid (0.4 mol) and melamine (0.2 mol) with 37% formaldehyde (0.7 mol) in a mol ratio of 4 : 2 : 7 in the presence of 2 M 200 mL HCl as a catalyst at 140°C ± 2°C for 6 h in an oil bath with occasional shaking to ensure thorough mixing. The separated terpolymer was washed with hot water and methanol to remove unreacted starting materials and acid monomers. The properly washed resin was dried, powdered, and then extracted with diethyl ether and then with petroleum ether to remove 8-hydroxyquinoline 5-sulphonic acid formaldehyde copolymer which might be present along with 8-HQ5-SAMF-IV terpolymer. The yellow colour resinous product was immediately removed from the flask as soon as reaction period was over and then purified. The reaction and suggested structure of 8-HQ5-SAMF-IV is shown in Figure
Reaction and expected structure of 8-HQ5-SAMF-IV terpolymer resin.
The terpolymer was purified by dissolving in 10% aqueous sodium hydroxide solution, filtered, and reprecipitated by gradual dropwise addition of ice-cold 1 : 1 (v/v) concentrated hydrochloric acid/distilled water with constant and rapid stirring to avoid lump formation. The process of reprecipitation was repeated twice. The terpolymer sample 8-HQ5-SAMF-IV thus obtained was filtered, washed several times with hot water, dried in air, powdered, and kept in vacuum desiccator over silica gel. The yield of the terpolymer resin was found to be 76%. The elemental analysis is tabulated in Table
Elemental analysis, molecular weight determination, and intrinsic viscosity of 8-HQ5-SAMF-IV terpolymer resin.
Empirical formula of repeat unit | Empirical weight of repeat unit (gm) | Average degree of polymerization | Average molecular weight | Elemental analysis | Intrinsic viscosity | |||
Percentage (%) of element | ||||||||
C | H | N | S | |||||
Found (Cal.) | Found (Cal.) | Found (Cal.) | Found (Cal.) | |||||
C55H45N11O21S5 | 1355 | 15.5 | 21002 | 48.15 (48.1) | 2.68 (3.32) | 10.79 (11.3) | 11.25 (11.80) | 1.31 |
The viscosities were determined using Taun-Fuoss viscometer at six different concentrations ranging from 1.00 to 0.031% of terpolymer in DMSO at 30°C. The intrinsic viscosity
The number average molecular weight
Electron absorption spectrum of terpolymer resin was recorded in DMSO (spectroscopic grade) on Shimadzu double beam spectrophotometer in the range of 200 to 850 nm. An infrared spectrum of 8-HQ5-SAMF-IV terpolymer resin was recorded on Perkin-Elmer-983 spectrophotometer in KBr pallets in the wave number region of 4000–400 cm−1. A nuclear magnetic resonance (NMR) spectrum of newly synthesized terpolymer resin has been scanned on Bruker Advanced 400 NMR spectrometer using DMSO-d6. TGA of terpolymer resin has been carried out by using Perkin-Elmer TGS-II Thermogravimetric Analyzer at heating rate of 10°C per minute up to 800°C.
The newly synthesized and purified 8-HQ5-SAMF-IV terpolymer resin was found to be yellow in colour. The terpolymer is soluble in solvents such as DMF, DMSO, and THF while insoluble in almost all other organic solvents. The melting point of the terpolymer was determined by using electrically heated melting point apparatus and is found to be in 392 K. This resin was analyzed for carbon, hydrogen, nitrogen, and sulphur content. The details of elemental analysis are incorporated in Table
The number average molecular weight
From the plot (Figure
Conductometric titration curve of 8-HQ5-SAMF-IV resin.
The intrinsic viscosity
According to the above relations, the plots (Figure
Viscometric curves of 8-HQ5- SAMF-IV terpolymer resin.
Values of intrinsic viscosity obtained from both plots have been found to be closed agreement with each other. The calculated values of the constants
The UV-Visible spectra (Figure
Uv-Visible spectrum of 8-HQ5-SAMF-IV terpolymer resin.
The IR (Figure
IR spectrum of 8-HQ5-SAMF-IV terpolymer resin.
The NMR spectrum (Figure
NMR spectrum of 8-HQ5-SAMF-IV terpolymer resin.
The polymer under study is terpolymer and, hence, it is very difficult to assign the exact structure. However, on the basis of the nature and reactive site of the monomers and taking into consideration the linear structure of other substituted phenol formaldehyde polymers and the linear branched nature of urea-formaldehyde polymers the most probable structure [
Thermogravimetry of 8-HQ5-SAMF-IV terpolymer resin has been carried out using Perkin-Elmer thermogravimetric analyser. A brief account of thermal behavior of 8-HQ5-SAMF-IV terpolymer is given in Figures
Decomposition pattern of 8-HQ5-SAMF-IV terpolymer resin.
Sharp-Wentworth plot of 8-HQ5-SAMF-IV terpolymer resin.
Freeman-Carroll plot of 8-HQ5-SAMF-IV terpolymer resin.
Decomposition pattern of 8-HQ5-SAMF-IV terpolymer resin has been shown in Figure
In the present investigation Sharp-Wentworth and Freeman-Carroll methods have been used to determine the kinetic parameters of 8-HQ5-SAMF-IV terpolymer sample.
In this method the following expression is used:
where
In this method the following expression is used:
where
Hence the graph of
A plot of percentage mass loss versus temperature has been shown in Figure
Results of thermogravimetric analysis of 8-HQ5-SAMF-IV terpolymer resin.
Terpolymer resin | Half decomposition temp. (K) | Activation energy (KJ/mol) | Entropy change | Free energy change | Frequency factor | Apparent entropy | Order of reaction found | |
8-HQ5-SAMF-IV | 653 | FC | SW | −160.9 | 109.7 | 780 | −19.1 | 0.98 |
36.8 | 35.5 |
FC = Freeman-Carroll, SW = Sharp-Wentworth.
Using thermal decomposition data and applying the Sharp-Wentworth method Figure
(i) Entropy change
(ii)
(iii) Frequency factor
(iv) Apparent entropy change:
where,
By using the data of the Freeman-Carroll method, various thermodynamics parameters have been calculated (Table
Fairly good straight line plots are obtained using two methods. This is expected since the decomposition of terpolymer is known not to obey first-order kinetics perfectly [
A terpolymer 8-HQ5-SAMF-IV, based on the condensation reaction of 8-hydroxyquinoline 5-sulphonic acid-melamine-formaldehyde in the presence of acid catalyst, was prepared. As the degradation of the terpolymer under investigation started at high temperature which indicates that the terpolymer 8-HQ5-SAMF-IV is thermally stable at elevated temperature. Low value of frequency factor may be concluded that the decomposition reaction of 8-hydroxyquinoline 5-sulphonic acid-melamine-formaldehyde terpolymer resin-IV can be classified as “slow reaction”.
The authors are grateful to the director of LIT, RTM Nagpur University, Nagpur, and the Head of the Department of Chemistry, LIT, RTM Nagpur University, Nagpur, for providing laboratory facility. They are also thankful to the director of SAIF, Punjab University, Chandigarh.