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Aromatic carboxamides as non-steroidal inhibitors of CYP17 for the treatment of prostate cancer
(Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Köseoğlu, Ahmet.; Acar, Ali Ersin.
Cancer is the most common neoplasm of the prostate in developed countries. Since up to 80 % of Prostate Cancer (PCa) proliferation depends on androgens, most patients take hormone therapy as first choice of treatment. The PCa cell proliferation occurs due to binding of these androgens to androgen receptor (AR) that is overexpressed on PCa cells. Therefore, when the androgens are segregated from the tumor cells, the proliferation of PCa cell will stop. Although the androgens are secreted from three different sites, namely the testes, adrenal glands, and PCa cells, androgen production depends on catalysis by one enzyme, CYP17, which is also known as P450-C17. Being a pivotal enzyme in the biosynthetic route to steroidal hormones, CYP17 has a key role in the conversion of progesterone and pregnenolone to androstenedione and dehydroepiandrostenedione (DHEA) respectively, which constitute as the direct precursors of 5α-dihydrotestosterone (DHT) and testosterone (T). Although Abiraterone was launched as a potent steroidal CYP17 inhibitor, it interferes with other steroidogenic enzymes leading to side effects such as hypokalemia, hepatic dysfunction, oedema, and hypertension. Due to the potential side effects of steroidal CYP17 inhibitors resulting from inhibition of other steroid receptors, there is a certain need to develop nonsteroidal inhibitors. In this study, several derivatives of a nonsteroidal lead compound were designed and synthesized in order to optimize its interaction with CYP17 enzyme. Throughout optimization process, bioisosterism was utilized as a rational drug design approach. Quinoline moiety was chosen as center of interest as it was hypothesized that similar to other CYP17 inhibitors, it could bind well to iron of the heme group of CYP17 enzyme. In order to perform a structure-activity relationship (SAR) study, a systematic synthesis of n-butyl substituted 8-amnionquinolines was done. A library of final products was built by synthesizing several aromatic carboxamides via coupling aromatic amines with aromatic carboxylic acids.
Cyclopolymerization of alkyl alpha-(hydroxymethyl)acrylate (RHMA) ether dimers via atom transfer radical polymerization (ATRP)
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2005., 2005.) Erkoç, Selda.; Acar, Ali Ersin.
Thermal stability, high glass transition temperatures and limited shrinkage duringpolymerization as compared to non-cyclic linear polymers are considered to beadvantageous properties of the polymers with high degrees of cyclization derived from cyclopolymerization of alkyl a-(hydroxymethyl)acrylate (RHMA) ether dimers. Thesecyclopolymers have been previously synthesized by conventional free radicalpolymerization. The conventional radical polymerization processes often yield polymerswith ill-controlled molecular weights and high polydispersities because of irreversible termination reactions. However, alkyl a-(hydroxymethyl)acrylate (RHMA) ether dimershave never been cyclopolymerized by controlled radical polymerization techniques.The purpose of this investigation is to get highly cyclized living aliphaticpolymers with controlled molecular weights and low polydispersities. In order to attain this goal, ATRP was applied to alkyl a -(hydroxymethyl)acrylate (RHMA) ether dimersas monomer. CuBr/PMDETA catalyst system was employed and polymerizations werecarried out in xylene. The results indicate that the desired cyclopolymers can be obtainedby ATRP technique.
Design and synthesis of drug molecules against prostate cancer
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2010., 2010.) Şahin, Tuba.; Acar, Ali Ersin.
Prostate cancer is a common disease in today’s world; especially in the western world it is the most prevalent cancer among men. It is believed that there is a correlation between prostate cancer and increased levels of certain hormones. It has been also observed that lowering androgen levels often makes prostate cancers shrink or grow more slowly, and therefore, the target of the treatment becomes the androgen removal. It is believed that effective inhibitors of the enzymes involved in testosterone and dihydrotestosterone (DHT) biosynthesis could be useful in the treatment of diseases associated with androgen excess in women and in the treatment of androgen-sensitive prostatic hyperplasia and cancer in men. In the biosynthesis of testosterone and DHT there is a common enzyme, 17-alpha hydroxylase C17,20-lyase (CYP17), utilized both in testicular and adrenal androgen synthesis. Therefore inhibition of this enzyme is a valuable technique to lower or, if possible, to eliminate the availability of androgens to the prostate. This project started with Structure Based Drug Design (SBDD) studies at Koc University using a computer generated model of the CYP17 enzyme where several thousands of molecules were subject to screening. In this screening study, the docking and binding energies were calculated and a lead compound was found. The in-vivo testing of the lead compound showed that the computer model’s prediction for the potential activity was right. To increase the observed activity (IC50= 35 micromolar) and specificity against the enzyme, the lead compound needed to be derivatized. The lead compound is constituted of two parts; the naphtyl and the phenyl subunits. In this study the aim was to synthesize lead compound derivatives which have branched alkyl susbstituents on the phenyl ring. Thus benzoic acids substituted with amino and/or methoxy groups were subjected to functionalization using different techniques to obtain branched alkyl groups on the phenyl unit. Among these, the reaction of the benzoic acid ester derivative with a Grignard reagent proved to be the best approach in the synthesis of the branched alkyl derivatives.
Effect of polymer topology on non-covalently bonded polyesters
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Süsler, Göknil.; Acar, Ali Ersin.
Synthetic polymers have a crucial role in our daily lives. The irreversible nature of covalent bonding in conventional synthetic polymers makes them non-recyclable and prevents re-processing of the materials. Throughout the years with the development in technology, the demand for more advanced materials such as, reversible, recycable, and reprocessable materials has increased. Supramolecular chemistry has emerged to solve this need for reversibility in polymer materials. Supramolecular polymers are more tunable and dynamic due to their non-covalent and reversible nature. Non-covalent interactions include metal-ligand coordinations, host-guest, π – π stacking, ionic interactions and hydrogen bonding. Ionic hydrogen bonding has the known characteristics of hydrogen bonding such as directionality, strength and versatility. For instance, a carboxylic acid and an amine give rise to ionic hydrogen bonding by acid-base complexation reaction. Thus, carboxyl-terminated polyesters, in principle, may coordinate with amines to produce supramolecular materials. In this study, the carboxyl-terminated polyesters and amines having different functionalities were mixed/reacted in a melt reactor to form acid-base coordinates. The thermal and mechanical properties of the amine treated polyesters were investigated through DSC and rheometric measurements, respectively.
Effect of the ester (R) groups on the controlled/living ATRP cyclopolymerization of alkyl alpha-(hydroxymethyl) acrylate (RHMA) ether dimers
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2009., 2009.) Bayrak, Sezgin.; Acar, Ali Ersin.
Previous cyclopolymerization studies of alkyl α-(hydroxymethyl) acrylate (RHMA) ether dimers showed that they are superior to non-cyclic linear ones due to improved thermal stability and high glass transition temperatures. Cyclopolymerizations of RHMA ether dimers via controlled living ATRP have been formerly investigated in the literature where smaller alkyl groups such as ethyl, n-butyl and tert-butyl and bulkier groups such as; adamantyl and cyclohexyl groups were used as the alkyl group. It was found out that as the bulkiness of the alkyl group (R) increased, cyclization efficiency and polydispersities were improved up to certain size (t-butyl), but became worse when the size was increased further. However, the present study with another bulky group, isobornyl, exhibited polydisperties as low as the ones obtained with smaller t-butyl derivative, indicating that the ATRP process was more controlled than other bulky groups such as adamantyl. In addition to this, smaller isopropyl derivative was also studied and polydisperties was found to be much higher than the monomers with bulkier isobornyl and t-butyl groups, indicating that the ATRP polymerization was less controlled. In this study, CuBr/PMDETA catalyst system was employed and cyclopolymerizations of isobornyl and isopropyl α-(hydroxymethyl) acrylate ether dimers were carried out in xylene. Cyclopolymers of IBHMA and IPHMA ether dimers were employed as macroinitiators in copolymerization studies with t-butyl acrylate comonomer in order to prove the livingness. SEC analysis showed that the cyclopolymers obtained were all living. Fortcoming studies on the physical properties of the cyclopolymers were also carried out and high Tg values and thermal stabilities were investigated.
Formaldehyde - free crosslinker synthesis in waterborne binder dispersions for textile industry
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Aracı, Seda.; Acar, Ali Ersin.
In textile industry, the binders used are mostly water based acrylic dispersions. These binders provide strength, elastic recovery, soft hand, flexibility, color retention and also resistance to washing and aging to the textile and nonwoven. Nevertheless, binders having no reactive functional monomers are not very successful in imparting these properties. Self crosslinking monomers are used to improve the properties of textile and non woven end products. N-methylolacrylamide (NMA) is one of these monomers having functional groups for self-crosslinking. However, N-methylol acrylamide used in textile binders emit formaldehyde during crosslinking at high temperatures. This formaldehyde either remains in the end product or is liberated into the air. The U.S. Department of Health and Human Services published the 12th Report on Carcinogens and formaldehyde is listed in the category of known to be a human carcinogen. Researchers on textile sector are focud on the subject of formaldehyde emission due to the harmfull effects on both people and environment. In this study, a novel monomer that emmits no formaldehyde and have ability to self-crosslink was investigated for replacement of NMA and the performance results are compared with that of NMA.
Investigation of polyethylene terephthalate synthesis via solution polymerization technique
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Yeşil, Işıl.; Acar, Ali Ersin.
Poly (ethylene terephthalate) (PET) is a thermoplastic polyester commonly used in the industry owing to its good mechanical strength, thermal stability, high solvent resistance and low-cost production. According to application area, various molecular weight PET is produced mostly at high temperature at melt phase under vacuum. Although melt polymerization is feasible and widely used, there are disadvantages of the system such as degradation of PET due to the long reaction time at high temperature and formation of side products such as diethylene glycol. To avoid such degradations, melt polymerization is used to obtain PET’s that are considered medium molecular weights then solid state polymerization is employed to produce higher molecular weight PET’s. However, SSP requires very long reaction times (12-24 h) which makes it very inconvenient and expensive. Therefore, in the present work, an alternative pathway that could potentially replace the SSP process was investigated. The main goal was to synthesize PET-anhydrides, in other words, polyester anhydrides, that may act as chain extenders when reacted with –OH terminated medium molecular weight PET’s. During such effort, syntheses of polyacid anhydrides, then PET polyesters, then finally PET polyester anhydrides were investigated. These reactions were all carried out by solution polymerization techniques which is not a reported technique for the synthesis of PET. The scope and the limitation of such a process for the synthesis, and its effect on the final polymer properties are discussed. The results from templatize chain coupling reactions of PET using the polyanhydrides and polyester anhydrides is presented.
Investigation of reaction mechanism of epoxy resins with amide functional groups
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) İkikardeşler, Seda.; Acar, Ali Ersin.
Epoxy resins are used for many applications due to their noteworthy properties such as low creep, reasonable elevated temperature performance, chemical resistance and good adhesion to various substrate, etc. Epoxy resins gain such characteristics even at moderate level of crosslinking often referred as curings. There are various types of hardeners that initiate curing reaction, which all bring some characteristics to the material depending on their chemical and physical features. The information we have up to now, amides as hardener are not used as much as other kinds of curing agents like amines, anhydrides and acids, etc. Interestingly there are only a few reports on the reaction of epoxides with amides in general. Furthermore, in these limited studies done with amide and epoxy resins, there is little information about the effect of amide or the epoxide structure on these reactions, since the cured product analyses were mostly limited to FTIR analyses due to the solubility issues. Here, synthesis of soluble samples and their further spectroscopic analyses were aimed. Thus depending on these results about the structure of product, the idea about probable reaction pathway was developed. Also, temperature and heating time were adjusted to carry out the reaction under suitable conditions. Monomeric amide sources were used to avoid from complete crosslinked structure and provide solubility. Aromatic group containing amide and epoxy were used as well for comparison of effect of aromaticity and aliphaticity on reaction. In addition to FTIR and DSC, 1H-NMR and LS-MS analysis were realized for soluble samples.
Modification of polypropylene by free radical grafting
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2021., 2021.) Kaya, Gülizar.; Acar, Ali Ersin.
Polypropylene (PP) market forms the second largest polymer business worldwide owing to its good mechanical properties, excellent chemical resistance and low-cost production. These attractive properties of PP are mainly dependent on its stereospecificity. Isotactic polypropylene (iPP), which can be produced by Ziegler-Natta catalysts with high isotacticity indices, has a commercial significance. However, atactic polypropylene (aPP) which has a lack of order is produced as a byproduct during iPP manufacturing. In general, aPP obtained as a byproduct has a low molecular weight, and it is essentially amorphous. Since aPP has low thermal stability and poor mechanical properties, it is considered an industrial waste, and application fields are limited. In this study, aPP was modified by free radical grafting technique to obtain value-added material from this industrial waste. Free radical grafting of functional monomers onto polyolefins is a widely practiced method for modification of polyolefins. The functionalization of polyolefins can improve their compatibility with engineering polymers. In this way, the incorporation of modified polyolefins into polymer blends and composites can be achieved. However, during free radical grafting, the desired grafting reaction competes against side reactions including homopolymerization of the monomer, chain scission and crosslinking. Within the scope of this study, grafting reactions of maleic anhydride and its derivative onto aPP were carried out in both solution and melt. The effect of reaction parameters and conditions on grafting yield and its effect on final polymer properties were investigated.
Polymeric tubes prepared from poly (vinyl alcohol) fiber templates
(Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2016., 2016.) Çavuşoğlu, Jesmi.; Acar, Ali Ersin.; Küsefoğlu, Selim.
In this study, the fabrication of covalently crosslinked polymeric tubes by using poly(vinyl alcohol) (PVA) fiber templates has been demonstrated. The crosslinking on the surface of PVA fiber templates was achieved by two different methods. In the first method PVA surface hydroxyl groups were reacted with difunctional crosslinkers. Crosslinking took place with several dialdehydes and diisocyanates, respectively. The conditions were adjusted to allow the reaction to occur only on the surface and unreacted PVA inner core was removed from crosslinked fibers. Tubular structures which have adjustable shell thicknesses were succesfully fabricated by glutaraldehyde (GA) and 1,6-hexamethylene diisocyanate (HMDI) crosslinked PVA microfibers. Ultraviolet-visible spectroscopy was used to investigate load/release properties of these tubular hydrogels with changing shell thicknesses. Fluorescein dye molecules were used for imaging and the succesful absorption of dye molecules inside the shells was observed by optical microscopy. Furthermore, hydrophilicity differences were predicted between the outer and the inner shells. The feasibility of this method in fabrication of nanotubes was also investigated. In the second method PVA fibers were first reacted with acryloyl chloride and 3-trimethoxysilyl propylmethacrylate, respectively, to get double bond functionalized PVA fibers. These pendant double bonds were used to photopolymerize the surface of PVA with other mono and/or difunctional acrylate monomers. It was observed that during dissolution of the inner core, the shells were ruptured which may be due to a rigid network formation by photopolymerization. Therefore, it was found that the first crosslinking method is more suitable to prepare such hollow structures whose shells can be adjusted in terms of crosslinking and thickness. It was concluded that such materials may have potential applications in entrapment and release of several molecules.
Screening of various polyethylene terephthalate chain extenders in a melt polymerization set-up
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Özdemir, Ayşenur.; Acar, Ali Ersin.
Polyethylene terephthalate (PET) is one of the most important and common polyester in the industry. It is produced by the reaction of ethylene glycol (EG) with terephthalic acid (TPA) or dimethyl terephthalate (DMT). The polymerization can be carried out through melt then, if high molecular weights are targeted, solid state polymerization. PET has excellent chemical resistance, high mechanical strength and high thermal stability. Therefore it is used in very different application areas. For every application area PET have different molecular weight values. As the molecular weight requirement increases the production of PET becomes difficult via melt polymerization. Solid state polymerization (SSP) is used for high molecular weight PET production. SSP’s disadvantage is that reaction time is very long and therefore expensive. Also, during processing of PET, molecular weight decreases because of the heat applied. All these problems can be addresed via chain extenders. In this study, chain extension reactions of PET with four different chain extenders, carbonyl biscaprolactam, 1,3-phenylene-bisoxazoline, DE and SO were carried out and their effect on molecular weight were investigated. Structures of DE and SO will not be noted in this thesis due to the confidentiality of the study.
Solid state polymerization and crystallization behavior of poly (ethylene 2,6-naphthalate)
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2012., 2012.) Yaşar, Nurdan.; Acar, Ali Ersin.
Poly(ethylene 2,6-naphthalate) is a crystallizable thermoplastic produced by condensation polymerization of naphtahalene dicarboxylic acid and ethylene glycol. It has superior mechanical and physical properties compared to the well-known thermoplastic poly(ethylene terephthalate) (PET). Additionally, the resistance of PEN to chemicals, and heat make this polymer valuable for commercial uses. The production of high molecular weight PEN by melt polymerization method has many disadvantages Solid state polycondensation method is an alternative to the melt polymerization eliminates some of these disadvantages. In this study, solid state polycondensation of PEN was performed and effects of certain process parameters on polymerization rate were investigated. Isothermal crystallization study of the synthesized polymers was carried out by using differential scanning calorimetry. Isothermal crystallization kinetics of the polymers was analyzed using Avrami equation.
Structure-reactivity relationship of acrylic acid ester ether dimers in ATRP
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2007., 2007.) Kocasakal, Gülhan.; Acar, Ali Ersin.
Aliphatic cyclopolymers synthesized by the cyclopolymerization of alkyl {460}- (hydroxymethyl)acrylate ether dimers have high thermal stabilities, high glass transition temperatures and show limited shrinkage during polymerization. Cyclopolymerizations of RHMA ether dimers by ATRP have been previously investigated in the literature for three different alkyl groups: ethyl, n-butyl and tert-butyl groups. It was found that as the bulkiness of the substituent group increased cyclization efficiency also increased. However, ATRP cyclopolymerization has not been investigated with dimers that contain bulkier substituents. It is known that cyclization efficiency in conventional free radical polymerization is higher for adamantyl {460}-(hydroxymethyl)acrylate ether dimer than the ones containing smaller alkyl groups such as ethyl, t-butyl. However, the effect of such bulky groups on the ATRP process was unknown. Therefore, ATRP’s of more bulky RHMA ether dimers such as adamantyl and cyclohexyl {460}-(hydroxymethyl)acrylate ether dimers were investigated. CuBr/PMDETA was employed as the catalyst complex and polymerizations were carried out in xylene. The results showed that, highly cyclized soluble aliphatic cyclopolymers could be obtained by the ATRP process with both monomers. However, the polydispersities of the cyclopolymers obtained were higher than the cyclopolymers obtained with the t-butyl derivative, indicating that the ATRP process was less controlled with bulkier groups. The livingness of the cyclopolymers was checked by the copolymerization studies with n-butyl and t-butyl acrylate comonomers where the cyclopolymers obtained were used as macroinitiators. Results suggest that cyclopolymers were living, however, copolymers obtained had high polydispersities most probably due to the slow initiation from the cyclic backbone. Preliminary studies on the physical properties of the cyclopolymers were also carried out.
Syntheses and characterization of polyesters derived from resorcinol and iso/terephthaloyl chloride
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Tığrak, Refia.; Acar, Ali Ersin.
Polyarylates are important class of polyesters, which are used for different application areas to improve thermal and mechanical properties of polymeric materials. They are also known as weatherable polymers that provide enhanced UV-protection. The different monomer compositions and their ratios in the polyesters affect the physical properties of polymers, such as flexibility or rigidity of polymer chains. On the other hand, linear and symmetrical monomer units make ordered packing while non-linear and non-symmetrical monomer units may produce cyclic oligomers. Therefore, they influence the glass transition temperatures (Tg) and the melting point (Tm) of the polymers. Previous studies performed in the literature involved the syntheses of polyarylates containing a composition of 1:1 ratio of 1,3 and 1,4 disubstituted acid chlorides. In this study, it was aimed to synthesize various polyesters with different ratios of these diacid chlorides to observe the structure-property relationship of the polymers. Furthermore, the syntheses of poly(ester-anhydrides) with the same monomers were performed to investigate the effect of anhydride linkages in the polymer backbone.
Syntheses of functional polyesters with tunable glass transition temperatures
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2018., 2018.) Kalaycı, Kübra.; Acar, Ali Ersin.
Polyesters are important polymers for many applications and one of them is powder coatings. They meet the required properties of powder coating resins. Furthermore, the ease of altering physical properties of polyesters opens a huge area to be studied. One of the important properties of polyesters is their glass transition temperature (Tg) which is the temperature that polymers change from rubbery to brittle structure. Tg can be affected by many factors related to the structure of polymers. Number average molecular weight (Mn) is one of the factors that has a great effect on it. It is also a critical feature for powder coating applications since powder coating resins undergo curing reactions in which crosslinking between chains occur and the coating takes its final form by applying heat. Therefore, the curing temperature is highly dependent on the Tg of powder coating resin. It is challenging to control Tg values of polyesters that are used as powder coating resins since it changes curing temperature. In order to study the effect of molecular structure, end group and molecular weight on Tg, various polyesters were synthesized with hydroxyl and carboxyl end groups. Polyesters with the same molecular weight but different end groups showed different Tg values. Higher Tg value was observed in carboxyl terminated polyesters probably because of hydrogen bonding between chains. On the other hand, changing one of the monomers to less sterically hindered one caused a big decrease on Tg. From the polyesters synthesized before, poly(ester-anhydride)s were tried to be obtained by using different anhydrides. Thus, it was achieved to increase Mn and Tg by increasing number of functional groups. Increasing Tg by this way, it was aimed to keep curing temperature low since these functional groups can also form crosslinks during curing reactions. Some reactions were successful with the formation of anhydride linkages, others ended up with the formation of anhydrides and chain scission at the same time. Formation of anhydride linkages between chains increased the molecular weight and Tg as expected.
Syntheses of novel acetal-based formaldehyde-free crosslinkers
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2019., 2019.) Öz, Şule Nihal.; Acar, Ali Ersin.
Crosslinking of polymers is a fundamental process applied in industry to enhance mechanical and physical properties of polymeric materials. Wide variety of crosslinkers are available to be used for this purpose whose structures depend on functionalities of the polymers and desired characteristics of the products. Crosslinkers can be in the form of polymeric or small molecule. As polymeric crosslinkers, formaldehyde based resins and latex binders may be given as examples of commonly used ones in coatings, adhesives and textile. N-Methylol acrylamide is one of the most commonly used monomer in latex binder composition to have crosslinkable system since it has good chemical, physical properties and self-crosslinking ability. However, it emits formaldehyde to the environment during the handling and crosslinking reaction as a side product. Formaldehyde based resins also release formaldehyde by degradation or during condensation as a side product. Formaldehyde is known as a human carcinogen compound and is harmful to the human health and the environment. Therefore there is a general tendency to limit or completely eliminate formaldehyde based chemical goods. Previous studies performed in our research group involved the syntheses of novel formaldehyde-free crosslinkers that are free radically polymerizable and their incorporation into latex binders by incorporating them into the polymer chains. This manuscript focuses on the synthesis of new formaldehyde-free crosslinkers in the form of small molecules. New crosslinkers will contain cyclic acetals as functional groups and have tetra- or tri- functional analogues. They will be used to crosslink –NH2 and -OH containing polymer chains through trans-acetalization reactions, and their crosslinking ability at different temperatures will be investigated.
Syntheses of polyesters and poly (ester-anhydrides) industrial applications
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2020., 2020.) Erten, Ayşe Zeyneb.; Acar, Ali Ersin.
Polyesters are one of the most important and widely used polymers in industry. Especially for powder coating application, the final properties of coating composition mainly depend on the polyester employed. These linear or branched polyesters are usually carboxylic acid terminated and thermally react with an epoxy hardener. The number of reactive end groups, the molecular weight, the viscosity, and the glass transition temperature (Tg) of polyesters affect the curing temperature and the levelling performance of the powder coating. For example, as the molecular weight of the polyester increases, Tg increases. This results in higher viscosity and thus poor levelling and surface quality. Therefore, in this study the aim was to synthesize poly(ester-anhydrides) that contains labile anhydride linkages. During the curing, those anhydride linkages will be broken and reacting with epoxy curing agents. In literature, poly(ester-anhydrides) are generally synthesized by acetic anhydride which limits its use in industry. In this study, aliphatic and aromatic cyclic anhydrides were examined for the synthesis of poly(ester-anhydrides) for industrial applications. They were melt mixed with carboxylic acid functional commercial polyesters that have different functionalities in order to investigate the effect of the total functionality on the poly(ester-anhydride) synthesis. Furthermore, a new polyester was synthesized and reacted with an aliphatic cyclic anhydride to gain know-how in polyesters and poly(ester-anhydride) syntheses. According to studies, the synthesis of poly(ester-anhydrides) with succinic anhydride (SA) seems more promising than pyromellitic dianhydride (PMDA) which has limited solubility. It is most likely that, high functionality of PMDA increased both the formation and scission of the targeted anhydride linkages.
Synthesis and characterization of precursors for quinoxaline cyclization
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Aykanat, Aylin.; Acar, Ali Ersin.
Quinoxaline compounds are essential nitrogen containing heterocyclic compounds of various biological properties and have several pharmaceutical applications. In this work, several precursors to be used in quinoxaline cyclization were synthesized from diamine- and tetra-aminobenzene hydrochloride precursors. Our group added several substituents to phenylenediamine or used directly 1,2,4,5-Benzenetetramine tetrahydrochloride before a coupling reaction with 1,2-Acenaphthylenedione. The systematic characterization of the quinoxaline derivatives and final products were done via 1H-NMR and13C-NMR.
Synthesis and properties of weatherable polymers from hydroxybenzophenones
(Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2008., 2008.) Dutağacı, Berçem.; Acar, Ali Ersin.
In this thesis, we have synthesized polymers with UV absorbing moieties in their structure which give them resistance to the sunshine and thus, make them suitable for outdoors applications. These moieties were chosen such that they are rearranged to hydroxy benzophenone type of UV absorbers under ultraviolet radiation via Photo-Fries Rearrangement. In other words, these polymers had an improved weatherability. The project involved first the synthesis of the monomer, then the homo-polymerization of the monomer followed by the co-polymerization of it with methyl methacrylate and finally investigation of absorption behaviors of the polymers under ultraviolet radiation before and after Photo-Fries Rearrangement. Thus, synthesis and properties of polymers with potentially increased weatherability will be discussed.
Synthesis and thermal characterization of tri-substituted triazines
(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Baykal, Duygu.; Acar, Ali Ersin.
Cyanuric chloride has huge application areas in chemical industries on drug, agriculture, polymer, dye and leather because of fact that cyanuric chloride is commercially cheap. In addition to this, its substitution reaction can be controlled easily via temperature. The most variety of application is in polymer industry. One of the applications of cyanuric chloride is polymerization of substituted s-triazines via a monomer with a nucleophilic group or end capping. In this study tri-substituted triazines were synthesized starting from cyanuric chloride and their thermal behavior were investigated in the presence of different nucleophiles to predict their potential for polymerization through trans-esterification reactions.

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