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Synthesis, characterization, and thermal degradation of novel poly (2-(5-bromo benzofuran-2-yl)-2-oxoethyl methacrylate).


Natural and synthetic compounds with benzofuran derivatives have many applications as sedatives, hypotonic, agrochemicals, pharmaceuticals, and cosmetics depending on their physiological, pharmacological, and toxic properties (1-4). Benzofurans exhibit important optical properties because of the fact that benzofuran ring has strong [pi] - [[pi].sup.*] transitions depending on [pi] - conjugated bonds (5). They are also located in the class of semiconductors, thanks to the partial load delocalization in their structures and intermolecular load transfer (6). As a result of using these compounds in the field of polymer chemistry and technology, new developments can be seen. In the recent years, the synthesis and characterization of new benzofuran derivative polymers have been successfully carried out (7-9). Those polymers, especially, methacrylate polymers or copolymers with benzofuran derivatives, have exhibited significant properties such as optical, antibacterial, and thermal properties (10-12).

The investigation of thermal behaviors of polymers depending on the thermal stabilities is required for most applications. For this purpose, thermogravimetric analysis (TGA) is a technique widely used in terms of its simplicity, accuracy, and the information obtained from a simple thermogram (13), (14). TGA method is also used to determine thermal decomposition activation energies of polymers (15). Thermal decomposition stabilities of methacrylate polymers change depending on the side groups (16). Especially, thermal properties of these compounds have attracted the attention of researchers due to the fact that the presence of heterocyclic groups on the polymer chains lead to increasing thermal stability (9). In the literature, there has not been enough work on the investigation of thermal degradation kinetics of methacrylate polymers with 5-bromo benzofuran derivative so far. Therefore, this study discusses the synthesis, characterization, and thermal degradation characteristics of poly (2-(5-bromo benzo-furan-2-yl)-2-oxoethyl methacrylate) [poly (BOEMA)], which is a new methacrylate polymer containing 5-bromo benzofuran side group synthesized for the first time.


Kinetic Analysis

In nonisothermal kinetic analysis, the reaction rate of thermally stimulated solid-state reactions is usually described by the following expression (17):

D [alpha]/dt=A exp (-E/RT) f ([alpha]) (1)

Moreover, the integral function of conversion, g([alpha]), can be determined by integrating this equation as following:


where [alpha] is the function of conversion, T is the absolute temperature, [beta] is the heating rate, A is the pre - exponential factor, E is the activation energy, R is the ideal gas constant, k (T) is the temperature - dependent rate constant, and f([alpha]) is the particular reaction model describing the dependence of the reaction rate on the extent of reaction. In case of thermal degradation of polymers, two degradation processes can be seen that are a sigmoidal function or a deceleration function (18-20). Different expressions of integral function of conversion for thermally stimulated solid-state reaction mechanisms are listed in Table 1. To estimate the thermal degradation mechanism of polymers, these functions can be applied to thermogravimetry (21).

TABLE 1. The g([alpha]) functions of solid-state processes.

Symbol                    g([alpha])                 Solid-state

[A.sub.2]     [[-ln (1- [alpha])].sup.1/2]       Nucleation and
                                                 growth (Avrami
                                                 equation 1)

[A.sub.3]     [[-ln (1- [alpha])].sup.1/3]       Nucleation and
                                                 growth (Avrami
                                                 equation 2)

[A.sub.4]     [[-ln (1- [alpha])].sup.1/4]       Nucleation and
                                                 growth (Avrami
                                                 equation 3)


[F.sub.1]     -ln (l- [alpha])                   Random nucleation
                                                 with one nucleus
                                                 on the individual

[F.sub.2]     1/(1 - [alpha])                    Random nucleation
                                                 with two nuclei on
                                                 the individual

[F.sub.3]     1/[(1- [alpha]).sup.2]             Random nucleation
                                                 with three nuclei
                                                 on the individual

[R.sub.1]     [alpha]                            Phase boundary

[R.sub.2]     [1-(1- [[alpha]).sup.1/2]]         Phase boundary

[R.sub.3]     [1-(1- [[alpha]).sup.1/3]]         Phase boundary

[D.sub.1]     [alpha]                            One-dimensional

[D.sub.2]     (1-[alpha] ln (1-[alpha])+        Two-dimensional
              [alpha]                            diffusion

[D.sub.3]     [[1-[(1-[alpha]).sup.1/3]].sup.2]  Three-dimensional
                                                 diffusion (Jander

D.sub.4]      (1-2/3 [alpha]) [(1- [alpha]       Three-dimensional
              ).sup.2/3]                         diffusion
                                                 (Ginstling -

Instrumental Techniques

Infrared spectra were recorded on a Perkin Elmer Spectrum 100. The ((1) H and (13) C) - nuclear magnetic resonance (NMR) spectra were carried out with a Bruker AC - 400 MHz Fourier transform NMR spectrometer. All NMR spectra were obtained in [CDCl.sub.3] and tetramethylsilane as an internal standard. For the determination of glass transition temperature of poly (BOEMA), a Perkin Elmer Sapphire differential scanning calorimetry (DSC) was used in the temperature range of 30-200 [degrees] C at a heating rate of 10 [degrees] /min under nitrogen atmosphere. TGA experiments were conducted through Perkin Elmer TGA instrument (Pyris Diamond TG/DTA) by measuring the change in the weight of samples as a function of temperature under a dynamic nitrogen gas atmosphere of 25 mL [min.sup.-1] flow rate, with the heating rates of 5, 10, 15, and 20 C/min over a range of temperatures from 40 [degrees] C to 500 [degrees] C. The average molecular weight was measured on an Agilent PL-GPC 220 integrated GPC/SEC system at 25 [degrees] C using a refractive index detector. Polystyrene standards were used to generate the universal calibration curve.

Materials and Methods

Sodium hydroxide, chloracetylchloride, potassium car-bonate, sodium methacrylate, 1,4-dioxane, tetrahydrofuran, chloroform, acetone, anhydrous magnesium sulfate, and glacial acetic acid were purchased from MERCK. 5-Bromosalicylaldehyde and chloroacetone were products of Aldrich. Benzoyl peroxide (analytical reagent purchased from Aldrich) was dissolved in chloroform and then recrystallized from ethanol.

Synthesis of 2-Bromo-l -(5-bromo benzofuran-2-yl) Ethanone

In this study, 2-bromo-l -(5-bromo benzofuran-2-yl) ethanone was used to synthesize BOEMA monomer. For this purpose, 5-bromosalicylaldehyde (8.04 g, 40 mmol) was first added to a solution of [K.sub.2] C[O.sub.2] (3.04 g, 2.83 mmol) in acetone (75 mL) at room temperature. This solution was cooled down to 0-5[degrees] C. At this temperature range, chloroacetone (3.62 g, 40 mmol) was added drop-wise to this stirred solution for 15 min. The solution was then stirred under rellux for 2 h. The mixture was cooled and filtrated, and the solvent was distilled off in vacuum. The crude product was dissolved in CH[Cl.sub.3] and extracted with water. The organic layer was dried over anhydrous MgS[O.sub.4] and evaporated in vaeuum. The product was recrystallized from ethanol. After that, the synthesis of 2-bromo-1 - (5-bromo benzofuran-2-yl) ethanone was performed according to Ref. (22), where a solution of bromine (1.84 g, 11.5 mmol) in 20 mL of glacial acetic acid was added dropwise to the stirred solution of (5-bromo benzofuran-2-y1) ethanone (2.50 g, 10.5 mmol) in 75 mL of glacial acetic acid for a period of 2 h, and after this time, the solvent was removed at reduced pressure to leave a brown solid residue. The residue was washed twice with ethanol and then recrystallized from ethanol in the form of shiny yellow crystals.

Synthesis of 2-(5-Bromo Benzofuran-2-yl-2-oxoethyl Methacrylate

2-Bromol-(5-bromo benzofuran-2-yl) ethanone (2.00 g, 6.29 mmol) was reacted with sodium methacrylate (0.68 g, 6.29 mmol) at 85 [degrees] C under a reflux condenser for 24 h in the presence of 1,4 - dioxane (50 mL) and hydroquinone (0.002 g) as inhibitor. After that, the mixture was cooled and filtrated, and the 1,4 - dioxane was distilled off in vacuum. The organic layer was poured into chloroform solvent and extracted with 5% NaOH solution a few times, and thus, the inhibitor was hydrolyzed. The chloroform layer was collected and dried over anhydrous MgS[O.sub.4] overnight. The solution was filtrated again, and the solvent was evaporated in vacuum. The residue was recrystallized from ethanol.

Homopolymehzation of 2-(5-Bromo Benzofuran-2-yl)-2-oxoethyl Methacrylate

Homopolymerization of BOEMA was carried out in solution using free radical polymerization technique. A polymerization tube with plastic screw cap was charged with 1.5 g of BOEMA, 4.5 mL of 1,4 - dioxane as solvent, and 0.015 g (1 wt% of the monomer) of benzoyl peroxide as initiator. The reaction solution was purged with argon for 15 min, and the glass tube was then closed with a rubber septum. The closed tube was placed in an oil bath preheated to 60 C [+ or -] 1[degrees] C for an appropriate polymerization time. After 3 h of polymerization, the polymerization tube was removed from the oil bath, allowed to cool for a few minutes, and then the solution was added dropwise to stirring petroleum ether to precipitate the polymer. The precipitated polymer was isolated via vacuum filtration and dried overnight in a vacuum oven at 40 [degrees] C. The schematic representation of polymer synthesis is illustrated in Scheme 1.


The structure of BOEMA, which is a novel methacrylate monomer containing benzofuran side group, was characterized by Fourier transform infrared spectrophotometer (FTIR), (1) H-NMR, and (13) C-NMR techniques. Figure 1 shows the FTIR spectrum of BOEMA in which the absorption peaks at 3131-3080 [cm.sup.-1] are characteristic of aromatic C--H stretching. The peaks at 2989-2935 [cm.sup.-1] are due to C--H stretching of aliphatic methylene and methyl groups. The strong absorbance at 1716 and 1697 [cm.sup.-1] are attributed to a vibration characteristic of methacrylic ester carbonyl and ketone carbonyl, respectively. The BOEMA monomer was especially characterized from the aliphatic and aromatic C=C stretching bands observed at 1635 and 1607 [cm.sup.-1], respectively. Especially, the presence of stretching of both carbonyl and C = C bonds, which are clearly seen in Fig. la, proves the formation of BOEMA monomer. In the (1) H-NMR spectrum of BOEMA (Fig. 2a), the resonance at 2.05 ppm is attributed to methyl protons. The singlet at 5.39 ppm is assigned to - OC[H.sub.2] protons. The absorption bands at 6.31 and 5.73 ppm are due to the protons in vinyl group. The multiplet resonance absorptions between 7.48 and 7.63 ppm are characteristic of aromatic protons on the benzene group, and the singlet resonance at 7.89 ppm is also attributable to = CH proton on the furan group. For the (13) C-NMR spectrum, the attached proton test technique was used in which the methylene and quartenary carbons were positive, while methyn and methyl carbons were negative. The l3C-NMR spectrum of BOEMA shown in Fig. 3 is also compatible with its structure, where the signals at 183.69 and 166.62 ppm correspond to ketone carbonyl carbon and methacrylic ester carbonyl carbon, respectively. The signals of aromatic carbons of benzofuran group observed between 154.23 and 112.28 ppm, except of the signals at 127.09 and 117.29 ppm, are due to vinylic ipso carbon next to ester carbonyl and vinylic methylene carbon (=[CH.sub.2]), respectively. The chemical shift at 66.02 ppm is assigned to--OC[H.sub.2] carbon. The methyl carbon on the methacrylic group is observed at the lower downfield, which is 18.32 ppm.

The spectral characterization of poly (BOEMA) was performed with FTIR and JH-NMR methods. The FTIR spectrum of poly (BOEMA) was illustrated in Fig. lb. The most characteristic absorption bands for polymer are as follows: the bands at 3127-3071 and 2930-2992 [cm.sup.-1] are due to aromatic and aliphatic C--H stretching vibrations, respectively. The peaks for carbonyls of ketone and ester are observed at the vibration frequencies of 1703 and 1738 [cm.sup.-1], respectively. In the frequency region of C=C stretching, only the absorption band at 1609 [cm.sup.-1] for aromatic C=C stretching was observed, whereas the aliphatic C=C stretching was not observed. The disappearance of aliphatic C=C stretching is one of the main evidences that the homopolymerizalion of BOEMA is accomplished by free radical polymerization method. The bands at 1256 and 1049 [cm.sup.-1] are also attributable to asymmetric and symmetric C - O - C stretching vibrations of ester group. On the (1) H-NMR spectrum of the poly(BOEMA) shown in Fig. 2b, the resonance at 7.89 ppm and the resonances between 7.64 and 7.47 ppm are assigned to =CH proton on the furan group and aromatic protons on the benzo group. The singlet signal attributed to - OC[H.sub.2] protons is appeared at 5.39 ppm. The backbone methylene and methyl protons of poly (BOEMA) are observed at the resonances of 2.06 and 1.22 ppm, respectively. The other main evidences that the homopolymerization is accomplished are the disappearance of two singlet resonances at 6.31 and 5.73 ppm assigned to vinylic protons of BOEMA monomer and the appearance of a new broad signal at chemical shifting of 2.06-1.22 ppm. which is due to methylene and methyl protons on the homopolymer backbone.

The glass transition temperature of poly (BOEMA) was determined from DSC method at a fixed heating rate of 10 [degrees] C/min under nitrogen atmosphere from ambient temperature to 200 [degrees] C. From DSC thermogram, one transition was observed at 137 [degrees] C, which is illustrated in Fig. 4.

The molecular parameters of poly (BOEMA) were measured on a gel permeation chromatography (GPC) system. The number average molecular weight and molecular weight distribution of poly (BOEMA) were determined to be 80,900 and 1.92, respectively. Here, the polydispersity was partially observed at a high value because of the variable quantity of initiating sites per chain. This result is an expected behavior for free radical polymerization process.

Kinetic parameters and thermal characteristics of poly (BOEMA) samples were determined by TGA under conditions of nonisothermal heating. The dynamic experiments of degradation were performed by increasing the temperature up to 500 [degrees] C at heating rates of 5, 10, 15, and 20 [degrees] C/min in an inert atmosphere of nitrogen. The mass loss curves showed that decomposition of poly (BOEMA) took place in one stage in the 30% weight loss area attributed to the formation of volatile hydrocarbons in the first decomposition temperature range up to - 340 [degrees] C.

It was found that the temperature corresponding to the maximum rate loss shifted to higher temperatures for pyrolysis of poly (BOEMA) as the heating rate was increased. These alterations were reported in literature for different polymers (23-25). The temperatures for maximum rate losses at heating rates of 5, 10, 15, and 20 [degrees] C/ min determined from derivative thermogravimetry (DTG) were 277.71, 283.16, 291.00, and 295.00[degrees] C, respectively. Table 2 shows the analysis of the TGA data in relation to healing rale to the temperature where the decomposition initiates, to the mass losses at different temperatures, and residues at final temperature of 500 [degrees] C. Table 2 also shows that as the heating rate is increased, there was a lateral shift to higher temperatures for initial decomposition temperatures. This shifting is clearly seen in Fig. 5, where the alteration of the weight loss curves of poly (BOEMA) samples in relation to heating rate to the final temperature of 500 [degrees] C was illustrated.

TABLE 2. Thermal degradation characteristics for poly (BOEMA)
at different heating rates.

Heating                  %Weight    %Weight   % Weight
                            loss       loss       loss
   rate     [T.sub.i]     at 300     at 350     at 500
([degrees]  ([degrees]  [degrees]  [degrees]  [degrees]
   C/min)          C)          C          C          C

 5                250       24.7       34.8       62.5
10                259       18.6       32.6       59.9
15                265       15.5       30.9       58.6
20                267       13.4       30.5       58.5

[T.sub.i]: initial decomposition temperature.

The kinetic information can be evaluated from dynamic experiments by means of different methods such as Flynn-Wall-Ozawa (26), (27), Kissinger (28), Coats-Redfern [29], and Van Krevelen [30] methods. The Flynn-Wall-Ozawa method is one of the integral methods to determine the activation energy without knowledge of reaction order. It is used to determine the activation energy for given values of conversion. The kinetic equation of this method on the basis of Arrhenius equation is as follows:

[log.sub. [beta] ]=log[AE/g([alpha] R)] - 2.315 - 0.457 E/RT (3)

The E value can be calculated from the slope of a plot of log [beta] versus (1000/T) for a constant weight loss, which is equal to (-E/R). The correlation between log [beta] and (1000/T) is linear. Another integral method is Kissinger method (28), which determines the activation energy, E, of thermal degradation with the following equation:

Ln([beta]/[T.sub.max.sup.2]) = {ln AR/E +ln[n[(1-[[[alpha].sub.max]).sup.n-1]]]} (4)

where [T.sub.max] is the temperature corresponding to the maximum reaction rate, ([beta] is the healing rate, A is the Pre - exponential factor, [[alpha].sub.max] is the maximum conversion, and n is the reaction order. The activation energy, E, can be calculated from the slope of a plot of ln([beta]/[T.sup.2] max) versus l000/[T.sub.max] and fitting to a straight line.

These two methods have a significant advantage that they do not require previous knowledge of the reaction mechanism for the determination of the activation energy compared with other methods (20). The plots of log [beta] against 1000/T in Eq. 3 are appeared in Fig. 6. Owing to the fact that Eq. 3 was derived from the Doyle integral method (31), we used only conversion values at the low conversions such as intervals from 3% to 12% in this study. The fitting straight lines in Fig. 6 are nearly parallel. This indicates that the applicability of Flynn-Wall-Ozawa method to poly (BOEMA) polymer at these conversions may be valid. The activation energies estimated at different conversions are listed in Table 3. The mean activation energy value in Table 3 was calculated as 180.13 kJ / mol. According to Eq. 4y the activation energy E can be determined from Kissinger's method. Figure 7 shows the slope of a plot of ln ([beta] /[T.sup.2]) versus 1000/ [T.sub.max]. Thus, the activation energy from this method was 188.47 kJ / mol. When the activation energies determined from these two methods are compared with each other, a good agreement between these values can be seen. The activation energy at 5% conversion in which E = 187.69 kJ/mol is very close to Kissinger's method, 188.47 kJ/mol.

TABLE 3. Decomposition activation energies obtained using
I he Flynn-Wall-Ozawa method.

[alpha]  E (KJ/mol)    R

0.03        179.10  0.9808
0.05        187.69  0.9955
0.07        179.19  0.9990
0.09        181.37  0.9991
0.12        173.28  0.9845
Mean        180.13

To determine the most probable thermal degradation mechanism of poly (BOEMA), Coats-Redfern method was used. Using an asymptotic approximation for the resolution of Eq. 2, the following equation can be obtained:

Ln g([alpha])/[T.sup.2]=ln(AR/ [beta] E) - E/RT (5)

According to Eq. 5, apparent activation energy for every integral function listed in Table 1 can be calculated from fitting ln g ([alpha]) /[T.sup.2] versus 1000/T plots for each heating rate. The apparent activation energies and correlations for conversions in the range of 3%-12% are tabulated in Tables 4-7 for heating rates of 5, 10, 15, and 20 [degrees] C/min, respectively. To elucidate the degradation mechanism of poly (BOEMA) . we compared the apparent activation energies obtained by the methods of Kissinger and Flynn-Wall-Ozawa, which are independent of any thermal decomposition mechanism. According to Table 6, for a constant heating rate of 15 [degrees] C/min, it could be found that the activation energy value of poly (BOEMA) corresponding to the mechanism of [F.sub.1] is 174.29 kJ/mol, which is very close to 180.13 kJ/mol by Flynn-Wall-Ozawa method and also in good agreement with the value obtained by the Kissinger method (188.47 kJ/mol.). The activation energies calculated for [F.sub.1] thermal degradation mechanism in the other Tables 4, 5, and 7 are also in agreement with that obtained using Flynn-Wall-Ozawa and Kissinger's methods. From the analyses of these tables, it can be said that the optimum heating rate is 15 [degrees] C/min, and also that the solid-state thermodegradation mechanism of poly (BOEMA) homopolymer is a random nucleation with one nucleus on the individual particle of deceleration type of solid-state mechanism.

TABLE 4. Decomposition activation energies of poly (BOEMA)
calculated from Coats-Red fern and Van Krevelen methods
at heating rate of 5 C/min.

              Coats-Retifern method   Van Kreyelen method
Mechanism     F. (kJ/mol)       r      E (kJ/mol)       r

[A.sub.2]           81.54  0.9986           87.93  0.9990
[A.sub.3]           51.37  0.9985           57.09  0.9990
[A.sub.2]           36.29  0.9983           41.67  0.9990
[F.sub.1]          172.04  0.9988          180.43  0.9990
[F.sub.2]            3.05  0.5569            7.71  0.9519
[F.sub.3]           15.06  0.8826           20.01  0.9519
[R.sub.1]          166.11  0.9988          174.36  0.9989
[R.sub.2]          169.06  0.9988          177.37  0.9990
[R.sub.3]          170.05  0.9988          178.38  0.9990
[D.sub.1]          341.19  0.9989          353.29  0.9989
[D.sub.2]          345.09  0.9989          357.29  0.9990
[D.sub.3]          349.06  0.9989          361.35  0.9990
[D.sub.4]          346.41  0.9989          358.64  0.9990

TABLE 5. Decomposition activalion energies of poly (BOEMA)
calculated from Coats-Redferm and Van Krevelen methods
at heating rate of 10 C/min.

            Coals-Redlern method     Van Krevelen method
Mechanism    E (kJ/mol)       r     E (kJ/mol)       r

[A.sub.2]         63.88  0.9708          81.22  0.9922
[A.sub.3]         47.41  0.9900          52.61  0.9922
[A.sub.4]         33.28  0.9885          38.30  0.9922
[F.sub.1]        160.51  0.9922         167.07  0.9922
[F.sub.2]          2.30  0.6147           6.97  0.9757
[F.sub.3]         13.74  0.9324          18.56  0.9757
[R.sub.1]        154.87  0.9911         161.36  0.9911
[R.sub.2]        157.67  0.9916         164.19  0.9916
[R.sub.3]        158.61  0.9918         165.15  0.9918
[D.sub.1]        318.86  0.9916         327.33  0.9911
[D.sub.2]        322.58  0.9919         331.09  0.9915
[D.sub.3]        326.36  0.9923         334.92  0.9918
[D.sub.4]        323.92  0.9921         332.37  0.9916

TABLE 6. Decomposition activation energies of poly (BOEMA)
calculated from Coats-Redfern and Van Krevelen methods at
heating rate of 15 [degrees] C/min.

            Coats-Redfern method    Van Krevelen method
Mechanism    E (kJ/mol)       r     E (kJ/mol)       r

[A.sub.2]         82.53  0.9854          88.53  0.9870
[A.sub.3]         5l.95  0.9835          57.45  0.9870
[A.sub.4]         36.65  0.9813          41.92  0.9870
[F.sub.1]        174.29  0.9869         181.74  0.9870
[F.sub.2]          3.24  0.8130           7.99  0.9851
[F.sub.3]         15.70  0.9612          20.67  0.9851
[R.sub.1]        168.14  0.9852         175.48  0.9854
[R.sub.2]        171.20  0.9861         178.59  0.9862
[R.sub.3]        172.22  0.9864         179.64  0.9865
[D.sub.1]        345.51  0.9860         355.65  0.9854
[D.sub.2]        349.56  0.9865         359.77  0.9860
[D.sub.3]        353.69  0.9871         363.96  0.9865
[D.sub.4]        350.93  0.9867         361.17  0.9861

TABLE 7. Decomposition activation energies of poly
(BOEMA) calculated from Coats-Redfem and Van Krevelen
methods at heating rate of 20 [degrees] C/min.

             Coais-Redferm method   Van Krevelen method
Mechanism     E (kJ/mol)       r    E (kJ/mol)      r

[A.sub.2]          75.12    0.9994       81.37  0.9995
[A.sub.3]          46.99    0.9993       52.67  0.9995
[A.sub.4]          32.93    0.9992       38.33  0.9995
[F.sub.1]         159.49    0.9994      167.48  0.9995
[F.sub.2]           1.94    0.3684        6.72  0.9517
[F.sub.3]          13.13    0.8677       18.15  0.9517
[R.sub.1]         153.96    0.9995      161.83  0.9995
[R.sub.2]         156.71    0.9995      164.63  0.9996
[R.sub.3]         157.63    0.9995      165.58  0.9996
[D.sub.1]         317.18    0.9995      328.38  0.9995
[D.sub.2]         320.82    0.9995      332.09  0.9995
[D.sub.3]         324.52    0.9995      335.87  0.9996
[D.sub.4]         322.05    0.9995      333.36  0.9995

Also, the Van Krevelen method, which is another integral method, was used to verify the solid - state thermode - gradation mechanism of poly (BOEMA) determined from Coats--Redfern method mentioned earlier. For the determinations of the activation energies and correlations, Van Krevelen et al. approximated the exponential integral, and final equation is as given below:

log g ([alpha]) = log B + (E/R [T.sub.r] +1) log T (6)

where [T.sub.r] is a reference temperature, and it was taken as that corresponding to the maximum temperature rate determined from DTG in this work. The activation energies of every g ([alpha]) function were calculated from the slope of lines of log g ([alpha]) versus log T plots using Eq. 6. The activation energies and correlations in the conversions of 3%-12% were given in Tables 4-7 for heating rates of 5, 10, 15, and 20 [degrees] C/min, respectively. To verify that values,

the Van Krevelen method was compared with both Kissinger's and Flynn-Wall-Ozawa methods. Analyses of Tables 4-7 also show the [F.sub.1] reaction mechanism. Especially, the activation energy calculated for [F.sub.1] process given in Table 6 at heating rate of 15[degrees] C/min is 181.74 kJ/ mol, and correlation is 0.9870, which is in very good agreement with Flynn-Wall-Ozawa method, 180.13 kJ/ mol. That value is also in good agreement with the Kissinger's method, which is 188.47 kJ/moL As is mentioned earlier, Coats-Redfern and Van Krevelen methods, which are integral methods, were used to determine and verify the most probable thermal decomposition mechanism of poly (BOEMA). The apparent activation energies and correlations are closely related to each other, and optimum heating rale is 15 [degrees] C/min resulted from both that methods. Also, it was concluded that the thermal degradation mechanisms determined from both Coats-Redfern and Van Krevelen methods were progressing according to [F.sub.1] (mechanism, which is a random nucleation with one nucleus on the individual particle.


A novel methacrylate polymer, poly (BOEMA), was synthesized at 60 [degrees] C in solution of BOEMA with 1,4 - dioxane in the presence of benzoyl peroxide initiator using free radical polymerization technique for the first time. For the characterization, FTIR, (1) H-NMR, (13) C-NMR, GPC, DSC, and TGA/DTG techniques were used, Doyle approximation was applied to kinetic analysis of poly (BOEMA). The glass transition temperature of poly (BOEMA) was determined as 137 [degrees] C with DSC. The number average molecular weight and molecular weight distribution of poly (BOEMA) were found to be 80,900 and 1.92, respectively. The pyrolysis of poly (BOEMA) took place in one stage in the 30% weight loss area for the first decomposition temperature range up to - 340 [degrees] C. The temperatures for maximum rate losses shifted to higher temperatures with increasing heating rate. The apparent decomposition activation energies by Kissinger's and Flynn-Wall-Ozawa methods in the studied conversion range were 188.47 and 180.13 kJ/mol, respectively. Coats-Redfern and Van Krevelen methods were used to determine and verify the most probable thermal decomposition mechanism of poly (BOEMA). It was concluded from both methods that the thermodegradation mechanism was progressing according to [F.sub.1] mechanism, which is a random nucleation with one nucleus on the individual particle. The apparent activation energies and correlations are closely related to each other, and optimum heating rate is 15 [degrees] C /min.


The authors wish to thank the Adiyaman University Research Fund for financial support (FEFBAP2010/0003).


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Murat Koca, (1) Adnan Kurt, (1) Cumhur Kirilmis, (1) Yildirim Aydogdu (2)

(1.) Department of Chemistry, Faculty of Arts and Science, University of Adiyaman, 02040, Adiyaman, Turkey

(2.) Department of Physics, Faculty of Science, University of Firat, 23169, Elazig, Turkey

Correspondence to: Adnan Kurt; e-mail:

DOI 10.1002/pen.22085

Published online in Wiley Online Library (

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Author:Koca, Murat; Kurt, Adnan; Kirilmis, Cumhur; Aydogdu, Yildirim
Publication:Polymer Engineering and Science
Article Type:Report
Geographic Code:7TURK
Date:Feb 1, 2012
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