S Containing Oxime Esters Moieties Based on Cyclohexanon and Cyclopentanon*

NEW POLY(METHACRYLATE)S CONTAINING OXIME ESTERS MOIETIES BASED ON CYCLOHEXANON AND CYCLOPENTANON*

Ibrahim Erol** Afyon Kocatepe Universty Faculty of Science and Arts, Department of Chemistry, Afyonkarahisar, Turkey

Abstract The synthesis of two new methacrylates such as 2-[(cyclohexylideneamino)oxy]-2-oxoethyl methylacrylate (CHOEMA) and 2-[(cyclopentylideneamino)oxy]-2-oxoethyl methylacrylate (CPOEMA) are described. The monomers produced from the reaction of corresponding cyclohexanone O-(2-chloroacetyl) oxime and cyclopentanone O-(2- chloroacetyl) oxime with sodium methacrylate was polymerized in 1,4-dioxane solution at 65°C using AIBN as an initiator. The monomers and their polymers were characterized by IR, 1H- and 13C-NMR spectroscopy. The glass transition temperature of the polymers was investigated by DSC and the apparent thermal decomposition activation energies (Ed) were calculated by Ozawa and multiple heating rate kinetics (MHRK) method using the Shimadzu TGA thermobalance. By using gel permeation chromatography, weight-average (Mw) and number-average (Mn) molecular weights and polydispersity indices of the polymers were determined. The antibacterial and antifungal effects of the monomers and polymers were also investigated on various bacteria and fungi. The photochemical properties of the polymers were investigated by UV and FTIR spectra.

Keywords: Methacrylate; Oxime esters; Activation energy; Thermal decomposition; Biological activitiy.

INTRODUCTION Nowadays, the synthesis of functional monomers and their polymers and use in the synthesis of new functional polymers have attracted considerable interest. Methacrylic polymers find extensive applications in fiber optics, metal complexes, polymeric reagents, and polymeric supports[1−5]. Recent investigations report the use of oxime esters as irreversible acyl transfer agents where the leaving group, the oxime does not participate in the back reaction[6]. This methodology has been elegantly utilized for the preparation of chiral polymers[7], regioselective acylation of nucleosides and to obtain various nucleoside derivatives of medicinal significance[8]. In a previous report[9], methacrylate containing oxime ester moieties used as irreversible acyl transfer agents. Athawale and coworker reported the synthesis of geranyl methacrylate and (±) mentyl methacrylate by transesterification reaction using 2,3-butane dione mono-oxime methacrylate as acylating agents[10, 11]. O-acyloximes can be used as photobase generators and they have been proved to be quite efficient[12−17]. In case of phenyl acetyloximes, as a schematic process for amine production can be given.

* This work was supported by Afyon Kocatepe Universty Research Fund (No. 06-FENED-09). ** Corresponding author: Ibrahim Erol, E-mail: [email protected]; [email protected] Received June 14, 2007; Revised July 12, 2007; Accepted July 13, 2007 444 Ibrahim Erol

For carbonyl derivatives, direct hydrogen abstraction from the substrate to R leads to the formation of amine without requirement of water[18]. In previous studies, photolysis of oxime esters based on antraquinone were discussed as photo induced DNA cleaving agents for single and double strand scissions[19−21]. It is well known from the literature that the compounds containing oxime esters moiety have a strong ability to form metal complexes and exhibit a wide range of biological activities[21−25]. Thermogravimetric analysis (TGA) has been widely used to investigate the decomposition characteristics of many materials. Some methods have already been established to evaluate the kinetic parameters from thermogravimetric data[26–34]. In this paper, the TGA technique is applied to 2-[(cyclohexylideneamino)oxy]-2-oxoethyl methylacrylate (CHOEMA) and 2-[(cyclopentylideneamino)oxy]-2-oxoethyl methylacrylate (CPOEMA) homopolymers. The apparent activation energy was evaluated by isothermal thermogravimetric methods. The energies of activation at different steps were calculated by Ozawa and multiple heating rate kinetics (MHRK) methods[35]. The photochemical properties of polymers were investigated by ultraviolet spectrometer.

EXPERIMENTAL Materials Cyclopentanonoxime, cyclohexanonoxime, chloroacetyl chloride, hydroxylamino hydrochloride and sodium hydroxide (Merck), sodium methacrylate, 1,4-dioxane, potassium carbonate, acetonitrile, anhydrous magnesium sulphate (Aldrich) were used as received. 2,2′-azobisisobutyronitrile was recrystallized from chloroform- methanol. Bactopeptone and glucose was obtained from Difco. All the other chemicals were analytical grade and used without any further purification. Characterization Techniques Infra-red spectra were measured on a Perkin Elmer Spectrum BX FT-IR spectrometer. 1H-NMR and 13C-NMR spectra were recorded in CDCl3 with tetramethylsilane as the internal standard using on Bruker GmbH DPX-400 500 MHz spectrometer. Thermal data were obtained by using a Shimadzu DSC-60 instrument and TGA-60 thermobalance in N2 atmosphere. Molecular weight; (Mw and Mn) of the polymers were determined by e waters 410 gel permeation chromatography equipped with a differential refractive index detector and calibrated with polystyrene standards. Electronic spectra were obtained on a Shimadzu UV 1700 spectrophotometer. Synthesis of cyclohexanone O-(2-chloroacetyl) oxime

Synthesis of cyclohexanone O-(2-chloroacetyl) oxime was as follows: cyclohexanone oxime (1 mol) and K2CO3

(1 mol) was dissolved in 20 mL of anhydrous CH2Cl2 at 0°C, and then chloroacetyl chloride (1.1 mol) were added drop wise to the solution. The reaction mixture was stirred at room temperature for 12 h. (Scheme 1). The organic layer was washed several times with water and dried over MgSO4. Dichloromethane was evaporated. The organic layers were collected and the residue was distilled at 85°C at 666.7 Pa to give colorless liquid. Yield: 80%. The yield was 80%. Elemental analysis (%): C = 50.87 (found), 50.67 (calcd), H = 6.88 (found), 6.39 (calcd), N = 7.61 (found), 7.39 (calcd). IR (neat, cm−1): 1777 (C＝O oxime ester carbonyl), 1567 (C＝N―), 727 (C―Cl; no O―H absorption). Synthesis of cyclopentanone O-(2-chloroacetyl) oxime Synthesis of cyclopentanone O-(2-chloroacetyl) oxime was similarly synthesized expect that the product was distilled at 73°C at 5 mmHg. The yield was 80%. Elemental analysis (%): C = 46.90 (found), 47.88 (calcd), H = 5.63 (found), 5.74 (calcd), N = 7.94 (found), 7.98 (calcd). IR (neat cm−1): 1780 (C＝O for oxime ester carbonyl), 1570 (C＝N―), 735 (C―Cl; no O―H absorption).

New Poly(methacrylate)s Containing Oxime Esters Moieties 445

Scheme 1 Synthesis of the CHOEMA monomer and its homopolymer Monomer synthesis The reactions paths for the synthesis of CHOEMA monomer are shown in Scheme 1. Cyclohexanone O-(2- chloroacetyl) oxime (1 mol), and sodium methacrylate (1.1 mol) were stirred in 50 mL acetonitrile at 75°C in a reflux condenser for 24 h in the presence of 100 × 10−6 hydroquinone as inhibitor. Then the solution was cooled to room temperature and neutralized with a 5% KOH solution. The organic layer was washed several times with water and the water layer was washed with diethylether a few times. The acetonitrile layer and diethyl ether layer were collected and dried over anhydrous MgSO4 overnight. Acetonitrile and diethyl ether were evaporated. The organic layers were collected and the residue was crystallized from ethanol. Elemental analysis (%): C = 60.49 (found), 60.24 (calcd), H = 7.18 (found), 7.16 (calcd), N = 5.54 (found) −l 5.85 (calcd). IR (KBr, cm ): 1780, 1728 (oxime ester and methacrylic carbonyl), 1633 (CH2＝C―), 1600 (C＝ 1 C), 1570 (C＝N). H-NMR (chemical shift, δ): 5.6 (CH2＝, 1H); 6.2 (CH2＝, 1H); 4.8 (―OCH2―, 2H); 2.1 13 (CH3―, 3H); 2.2−2.8 (CH2, 10H on the cyclohexane). C-NMR (chemical shift, δ): 169.0 and 173.0 (C＝O of esters); 131.0 (＝C); 122.1 (CH2＝); 22.1−37.8 ( cyclohexane carbons); 65.0 (―OCH2―); 21.5 (CH3). The CPOEMA monomer was similarly synthesized. Elemental analysis (%): C = 58.98 (found), 58.66 (calcd), H = 6.83 (found), 6.71 (calcd), N = 6.22 (found) −l 6.42 (calcld). IR (neat cm ): 1786, 1728 (oxime ester and methacrylic carbonyl), 1634 (CH2＝C―), 1600 (C＝ 1 C), 1573 (C＝N). H-NMR (chemical shift, δ): 5.6 (CH2＝, 1H); 6.3 (CH2＝, 1H); 4.8 (―OCH2―, 2H); 1.8 13 (CH3― 3H); 1.9−2.5 (CH2 on the cyclopentane ring). C-NMR (chemical shift, δ): 164.0 and 167 (C＝O of esters); 136.0 (＝C); 124.1 (CH2＝); 62.0 (―OCH2―); 24−391 (CH2 cyclopentane carbons ) 17 (CH3). Polymerization of the monomers

Polymerization of CHOEMA and CPOEMA was carried out in glass ampoules under N2 atmosphere in 1,4- dioxane solution with AIBN (1% based on the total weight of monomers) as an initiator. The reacting components were degassed by threefold freeze-thawing cycles and then immersed in oil bath at 65°C for a given reaction time. The polymers were separated by precipitation in ethanol and reprecipitated from dichloromethane solution. The polymers were finally dried under vacuum to constant weight at room temperature and kept in a desiccators under vacuum until use.

RESULTS AND DISCUSSION As shown in Scheme 1, the preparation of new methacrylate having pendant oxime ester moiety CHOEMA monomer was synthesized from cyclohexanone O-(2-chloroacetyl) oxime with sodium methacrylate, according to the usual method[36]. The CPOEMA monomer was synthesized and characterized by the same methods. The yields of the reactions in Scheme 1 are of medium quantity (80%). The structure of CHOEMA and 446 Ibrahim Erol

CPOEMA were identified by elemental analysis, IR and NMR spectroscopy. Results were in good agreement with the structure of the compounds. The monomeric units of poly(CPOEMA) are presented in Scheme 2.

Scheme 2 Structure of the poly(CPOEMA) Structural Characterization of the Monomers and Their Homopolymers The FT-IR spectra of the CPOEMA monomer and its polymer poly(CPOEMA) are shown in Fig. 1. In the IR spectrum of the polymer showed some characteristic absorption peaks at 1739 cm−1 (ester carbonyl stretching) 1781 cm−1 (oxime ester carbonyl stretching), 1565 cm−1 (C＝N). During the polymerization of the monomers, the IR band at 1630 cm−1 (C＝C) disappearence and ester carbonyl stretching for polymers shifted to about 1739 cm−1, whereas that of oxime ester carbonyl appeared at about 1785 cm−1. The main evidence of the polymer is certainly the disappearance of some characteristic signals of the double bond in the spectrum and this fact was effectively observed in our case. Thus, two bands vanished in the IR spectrum: the absorption band at 923 cm−1 −1 assigned to the C―H bending of geminal ＝CH2 and the stretching vibration band of C＝C at 1600 cm . The 1H-NMR spectrum of the CHOEMA monomer is presented in Fig. 2. The 1H-NMR spectra of the both monomers have the characteristic peaks of the monomeric units. The 1H- and 13C-NMR spectra of the poly(CPOEMA) are shown in Fig. 3 and are good agreement with the structure. From 1H-NMR spectroscopy the formation of the polymer is also clearly evident from the vanishing of two signals at δ = 5.6 and 6.2 of the vinyl protons and the appearance of the broad signal at δ = 1.5 and 2.2 assigned to an aliphatic ―CH2― group. In the proton decoupled 13C-NMR spectrum of poly(CPOEMA), chemical shift assignments were made from the off- resonance decoupled spectra of the polymer. Resonance signals at δ = 178 correspond to ester group present in the pendant oxime group in polymer. The ester carbonyl in the pendant methacrylate resonance is observed at δ = 165. The signal due to carbon of the cyclohexane ring attached to the C＝N group shifts towards downfield and is observed at δ = 120. The methylenoxy group flanked between the carbonyl group and ester group show signals at δ = 62. The α-methyl group of polymer shows resonance signals at δ = 14. The cyclohexane ring carbons are observed δ = 23.6−39.8.

Fig. 1 FT-IR spectra of CPOEMA monomer (a) Fig. 2 1H-NMR spectrum of CHOEMA and its polymer (b) monomer New Poly(methacrylate)s Containing Oxime Esters Moieties 447

Fig. 3 1H-NMR (a) and 13C-NMR (b) spectra of poly(CPOEMA) UV Spectra of the Polymers A solution of homopolymers in DMSO was cast onto a quartz glass plate with a spin coater and then was annealed for 30 min at 40°C. The thin film (0.8−1 µm) was irradiated with a fixed energy of light from a Spex Fluorolog 2 with a 450-W xenon lamp. The UV spectra of the polymers show an absorption maxima at 255 nm for poly(CHOEMA), 248 nm for poly (CPOEMA) due to the π-π* transition of C＝N of the pendant oxime ester group chromophore present in the polymer unit. In fact, we had anticipated that the chromophore interactions in the present polymers would have been suppressed between the C＝N groups attached in the vicinity of each chromophere group such as ester. It can be seen that the absorption properties are only slightly by the ester group. This is attributed to a S0→S1 transition localized on the oxime moiety. Due to their structural analogy and the presence of electron lone pair on the heteroatom, ketones were often compared with the corresponding oximes[37], the question being the nature of the electronic transitions. The transition observed for the present oxime ester polymers are of π-π* nature and the presence of a lone pair on the nitrogen atom do not lead to any observable n-π* transition. Representative spectral change in UV absorption for films of poly(CHOEMA) caused by the photoreaction upon irradiation with light 350 nm is presented in Fig. 4. The absorption band at the longest wavelength decreased gradually with the increase of a new absorption band at around 200 nm. In addition, although all of the polymers were soluble in CH2Cl2, CHCl3, 1, 4-dioxane, and so forth before irradiation, not one of the polymers was soluble in any solvent after irradiation. All the experimental data 448 Ibrahim Erol

indicate that photo degradation in the oxime ester region occurred and crosslinking followed. A photo degradation mechanism of the poly(CPOEMA) is shown in Scheme 3. Dissociation of oxime leads to iminyl radical and acyloxyl radical. If the decarboxylation is not fast enough, these two radicals can be recombining to give the starting oxime, and therefore the global efficiency of the photodissociation is decreased[37]. On the contrary, the occurrence of the decarboxylation process leads to the formation of carbon dioxide and a new . radical (R ). The latter can also react in-cage with the iminyl radical to form an imine, resulting, in a decrease of the free iminyl radical quantum yield. The polymers react photochemically according to a mechanism similar to that found for O-acyloximes and its derivatives[38]. Though practical evaluation from spectral data is rather dubious because sensitivity of photocrosslinkable polymers is a function of Tg, molecular weight, polymer solubility and so on, the discrimination of photoresponsibilities of chromophores themselves is possible to a certain extent.

Fig. 4 UV spectrum changes due to the photoreaction of poly(CHOEMA) in the film state (0, 10, 20, 40, 80, 140 and ∞ (s))

Scheme 3 Photodegradation mechanism of the poly(CPOEMA) Molecular Weights of Polymers

The number-average (Mn) and weight-average (Mw) molecular weights and the polydispersity index of homopolymers were determined by GPC with polystyrene and tetrahydrofuran as the standard and solvent, respectively, and given in Table 1. The GPC traces showed a unimodel elution curves for both polymers (Fig. 5).

Table 1. Differantiel scanning calorimetry, molecular weight and physical parameters data of polymers 3 1/2 3 Sample Tg (°C) Mw Mn Mw/Mn δ (J/cm ) ηinh (dL/g) d (g/cm ) Poly(CHOEMA) 109 55000 29250 1.88 6.75 0.58 1.22 Poly(CPOEMA) 85 61200 38500 1.59 6.26 0.77 1.08

New Poly(methacrylate)s Containing Oxime Esters Moieties 449

Fig. 5 The GPC curves for polymers Fig. 6 The DSC thermograms of polymers

The PDIs of the polymers range between 1.6−1.90. The theoretical values of PDI for polymers via radical recombination and disproportionation are 1.5−2.0, respectively[39]. In the free radical polymerization of methacrylate monomers, the polymeric radicals undergo termination mainly by disproportionation[40]. Hence, the polydispersity index value of polymers suggests a greater tendency for chain termination by disproportionation than radical recombination, which is the case with many methacrylates. Glass Transition Temperatures

The glass transition temperature (Tg) was determined by a Shimadzu DSC 60. Samples of about 5–8 mg held in sealed aluminum crucibles and the heating rate of 20 K/min under a dynamic nitrogen flow (5 L/h) were used for the measurements. From DSC measurements Tg was taken as the midpoint of the transition region. These values are indicated in Table 1. As shown in Table 1, the Tg of poly(CPOEMA) was lower than that of poly(CHOEMA). This situation might be attributable to bulky substituent groups; a polymer bearing bulky side groups generally has a high glass transition temperature, because for such a chain the moving segment is necessarily large. These effects are easily seen by reference to the results of Watanabe[41]. On the other hand, a polymer that has high attraction forces between the chains will expand less readily than a no interacting polymer, therefore such an interacting polymer must be heated to a higher temperature before the free volume becomes as large as required at the glass transition temperature. In the case of poly(CHOEMA), the size of cyclohexane substituent of poly(CHOEMA) is large, and raises the Tg by increasing the interchain cohesive forces. On the other hand, the Tg of polymer is related to the chain flexibility and this parameter is to a large extent, a reflection of the rotational barrier about the bond linking monomer unit. The cause of this effect is not clear since chain flexibility not only depends on the rotational barrier but also on the chain packing, side chain stiffness, dipole interactions, etc. From DSC measurements Tg was taken as the midpoint of the transition region. The DSC thermograms of the polymers are shown in Fig. 6. The Tg of poly(CHOEMA) is 109°C and poly(CPOEMA) is 85°C, respectively. The glass-transition temperature of poly(CHOEMA) is considerably higher than the poly(CPOEMA). Apparently the bulky cyclohexane side group apparently decreases the flexibility of the chain and the free volume and increases the packing of chains, thereby increasing Tg. Determination of the Physical Parameters

Some physical parameters such as density (d), solubility parameter (δ) and inherent viscosity (ηinh) of the polymers were determined in the study. The densities of the polymers were determined experimentally by the flotation method[42] at 25°C using mixtures of methanol and formic acid as the floating agent, and many glass beads of known densities. The solubility parameters of the polymers were determined by using a titration [42] method at 25°C from a solubility test using CH2Cl2 as solvent and n-heptane and ethanol as non-solvent. Solutions of polymers in DMSO at the concentration of 0.5 g dL−1 were used to determine inherent viscosities

(ηinh = lnηr/c). Measurements were performed by an Ubbelohde viscometer thermostatted at 25°C. These values are shown in Table 1. The density of poly(CHOEMA) is higher than that of poly(CPOEMA). This result showed that poly(CPOEMA) chain stiffness, free volume and induced better packing of polymer segments is more than poly(CHOEMA) units. ηinh viscosity values of poly(CPOEMA) is higher than that of poly(CHOEMA). The solubility parameter of poly(CHOEMA) is higher than that of poly(CPOEMA). Because, the side groups of 450 Ibrahim Erol

poly(CHOEMA) are bigger and longer than that of the poly(CPOEMA). For this reason the molecules of solvents do not enter the polymer molecules and solubility becomes difficult. Thermal Analysis The thermal stabilities of the polymers were investigated by thermogravimetric analysis (TGA) in a nitrogen stream at a heating rate of 20 K/min. Thermogravimetric curves of the homopolymers are shown in Fig. 7. The initial decomposition temperatures of poly(CHOEMA) and poly(CPOEMA) are around 205°C and 240°C, respectively and independent of the side-chain structures. This result shows that main-chain scission is an important reaction in the degradation of polymers, at least in the beginning. The degradation of poly(CHOEMA) occurred in three stages. The first stage was observed at 210−310°C. The second stage decomposition commenced at 315−395°C, and the last stage was observed at 400−450°C. Poly(CPEOMA) undergoes two stages decomposition. The first stage was observed at 260−345°C, and the last stage was observed at 380−420°C. The residue at 450°C for the poly(CPEOMA) is about 10% and for the poly(CHOEMA) is about 20%.

Fig. 7 TGA curves of the polymers Fig. 8 Logarithm of heating rate versus reciprocal temperature at constant conversion for the thermal degradation of poly(CPOEMA) Decomposition Kinetics The activation energies on the thermal decomposition of copolymers were determined by thermogravimetric analysis. The activation energy of the decomposition process was determined by MHRK method. Typical procedure for the calculation of activation energy for polymers was as follows: Thus, the series of experiments were run at different heating rates, ΔEa could be obtained from the slope of a linear plot of lg(heating rate) versus 1/T. The lines shown in Fig. 8 were obtained by plotting heating rates versus 1/T of TGA curves for poly(CHOEMA) at various conversion levels. The activation energies of degradation calculated from TGA curves are based on weight loss at different decompositions regions during degradation. The calculation of activation energies of the poly(CPOEMA) was done by the same measurements. From the slopes, the average activation energies for the thermal degradation of the polymers are calculated and reported in Table 2.

Table 2. Thermal decomposition data and activation energies of the polymers by MHRK method Sample Stage of Temperature Average activation decomposition range (oC) energy (kJ/mol) Poly(CHOEMA) Stage 1 210−310 (37)a 85.65 Stage 2 315−395 (23) 78.20 Stage 3 400−450 (18) 71.50 Poly(CPOEMA) Stage 1 260−345 (45) 83.70 Stage 2 380−420 (23) 91.40 a Figures in parenthesis indicate weight loss (%) during to temperature range stated New Poly(methacrylate)s Containing Oxime Esters Moieties 451

Alternatively the activation energies can be obtained using the Ozawa method. For the study on the kinetics of thermal degradation of polymers we can select the isothermal thermogravimetry (ITG) or the thermogravimetry (TG) at various heating rates. ITG is superior to obtain an accurate activation energy for thermal degradation, although it is time consuming. In the case of thermal degradation of polymers, in which depolymerization is competing with cyclization or crosslinking due to the side groups, the TG at various heating rates is much more convenient than ITG for the investigation of thermal degradation kinetics. Therefore, in the present work TG curves at various heating rates were obtained and the activation energies (Ed) for thermal degradation of polymers were calculated by Ozawa’s plot, which is a widely used method. Degradations were performed in the scanning mode, from 35°C up to 500°C, under nitrogen flow (20 mL min−1), at various heating rates (β: 2.0, 4.0, 7.0, 10.0, and 12.5 K/min). Samples of 5−8 mg held in alumina open crucibles were used and their weights were measured as a function of temperature and stored in the list of data of the appropriate built-in program of the processor. The TGA curves were immediately printed at the end of each experiment and the weights of the sample at various temperatures were then transferred to a PC.

According to the method of Ozawa the apparent thermal decomposition activation energy, Ed, can be determined from the TGA thermograms under various heating rates, such as in Fig. 9 for poly(CPOEMA), and the following equation: R ⎡ dlg β ⎤ Ed =− ⎢ ⎥ (1) b ⎣d()1 T ⎦ where R is the gas constant; b, a constant (0.4567); and β, the heating rate (K/min). According to Eq. (1), the activation energy of degradation can be determined from the slope of the linear relationship between lgβ and 1/T. The apparent thermal decomposition activation energies for poly(CHOEMA) were calculated by the same methods. The Ed values for polymers are given in Table 3. Ed calculated from the Ozawa method is superior to other methods for complex degradation, since it does not use the reaction order in the calculation of the [43] decomposition activation energy . Therefore, Ed calculated from the Ozawa method was superior to the former methods for complex degradation. The average activation energies corresponding to the different stages have been calculated and listed Table 4. It is shown that this result was similar to methacrylate polymers in the literature[44, 45].

Fig. 9 The thermal degradation curves of poly(CPOEMA) at different heating rates

Table 3. The apparent activation energies of polymers under thermal degradation in N2 Sample Poly(CHOEMA) Conversion (%) 10 20 30 40 50 60 70 80 Ea (kJ/mol) 98.7 95.6 97.2 100.3 87.8 92.8 78.1 100.6 Sample Poly(CPOEMA) Conversion (%) 10 20 30 40 50 60 70 80 Ea (kJ/mol) 100.6 89.5 98.5 87.1 103.3 87.9 88.8 98.3 452 Ibrahim Erol

Table 4. Thermal decomposition data and activation energies of the polymers by Ozowa method Sample Stage of Temperature Average activation decomposition range (oC) energy (kJ/mol) Poly(CHOEMA) Stage 1 250−320 95.75 Stage 2 325−500 88.90 Poly(CPOEMA) Stage 1 230−350 98.50 Stage 2 360−500 91.80 Antibacterial and Antifungal Effects of the Monomers and Polymers The biological activities of the monomers and their homopolymers were tested against different microorganisms with DMSO as the solvent. The sample concentrations were 50 and 100 µg/disc. All microorganism strains were obtained from the Culture Collection of Microbiology Laboratory of Afyon Kocatepe University (Afyon, Turkey). In this study, Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922 and Pseudomonas aeruginasa ATCC 27853 were used as bacteria. Candida albicans CCM 31 was a fungus. YEPD medium cell culture was prepared as described by Connerton[46]. Ten milliliters of YEPD medium were inoculated with each cell from plate cultures. Yeast extract 10 g/L, bactopeptone 20 g/L, and glucose 20 g/L, was obtained from Difco. Microorganisms were incubated at 35oC for 24 h. About 1.5 mL of these overnight stationary phase cultures were inoculated onto 250 mL of YEPD and incubated at 35°C until OD600 reached 0.5. The antibiotic sensitivity of the polymers was tested with the antibiotic disk assay as described[47]. Nutrient Agar (NA) was purchased from Merck. About 1.5 mL of each prepared different cell culture were transferred into 20 mL of NA and mixed gently. The mixture was inoculated into the plate. The plates were rotated firmly and allowed to dry at room temperature for 10 min. Prepared antibiotic discs (50 and 100 µg) were placed on the surface of the agar medium[48]. The plates were kept at 5°C for 30 min and then incubated at 35oC for 2 days. If a toxic compound leached out from the disc, it means that the microbial growth is inhibited around the sample. The width of this area expressed the antibacterial or antifungal activity by diffusion. The zones of inhibition of microorganism growth of the standard samples monomers, and homopolymers were measured with a millimeter ruler at the end of the incubation period. The results were standardized against Penicillin G and Teicoplanin under the same conditions. All the compounds exhibited moderate activity comparable to that of the standard drugs. The data reported in Tables 5 and 6 are the average data of three experiments. The results show that the investigated polymers have good biological activity comparable to that of standard drugs such as Penicillin G and Teicoplanin. However, the exhibiting and inhibition zones of monomers and polymers significantly increased with antibiotic discs of the polymer in the culture, depending on the disc concentration. The biological activity data are given in detail in Tables 5 and 6.

Table 5. Antimicrobial effects of the compounds (mm of zones) Pseudomonas Escherichia Candida Staphylococcus Compounds aeruginasa coli albicans aurous CHOEMA monomer 9 10 12 9 CPOEMA monomer 7 10 − 9 Poly(CHOEMA) 9 11 10 8 Poly(CPOEMA) 9 10 − 9 Penicillin G − 12 − 35 Teicoplanin 14 11 12 17 DMSO − − − − Compound concentration: 50 µg/disc; DMSO: dimethylsulfoxide (control)

New Poly(methacrylate)s Containing Oxime Esters Moieties 453

Table 6. Antimicrobial effects of the compounds (mm of zones) Pseudomonas Escherichia Candida Staphylococcus Compounds aeruginasa coli albicans aurous CHOEMA monomer 11 12 14 10 CPOEMA monomer 8 11 8 10 Poly(CHOEMA) 12 13 11 13 Poly(CPOEMA) 10 11 − 11 Penicillin G 14 6 8 35 Teicoplanin − 6 12 15 DMSO 12 − − − Compound concentration: 100 µg/disc; DMSO: dimethylsulfoxide (control)

CONCLUSIONS The synthesis of new methacrylate monomers having pendant oxime ester moieties have been reported for the first time. The structure of both monomer and their polymers were characterized by spectroscopic methods. The biological activity and thermal stability of the polymers were investigated. The monomers and polymers had good biological activity in comparison with standard drugs. The decomposition activation energies of the polymers were calculated with the MHRK and Ozawa methods. The molecular weights of the polymers were determined by GPC. Finally, the photocrosslinking behavior of the polymers as thin films was tested in the presence of UV light. The increasing utility of photosensitive polymers in many applications, such as microelectronics, printing and UV-curable lacquers, and inks, has provided us with an incentive to obtain novel polymers.

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