Synthesis of High-Molecular Weight Biobased Epoxy Resins

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The synthesis of high molecular weight bio-based epoxy resins – determination of the course of the process by MALDI-TOF mass spectrometry Anna Sienkiewicz, and Piotr Czub ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b04727 • Publication Date (Web): 05 Apr 2018 Downloaded from http://pubs.acs.org on April 5, 2018

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ACS Sustainable Chemistry & Engineering

THE SYNTHESIS OF HIGH MOLECULAR WEIGHT BIO-BASED EPOXY RESINS – DETERMINATION OF THE COURSE OF THE PROCESS BY MALDI-TOF MASS SPECTROMETRY

Anna Sienkiewicz1, Piotr Czub2

Department of Chemistry and Technology of Polymers, Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska Str. 24, Kraków, Poland,

phone number:+48 012 628 21 29 fax: +48 12 628 20 35

1 2

e-mail: [email protected] e-mail: [email protected]

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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ABSTRACT The presented research shows the results of Matrix-Assisted Laser Desorption/Ionization mass spectrometry, which was used as a mean of monitoring the synthesis of novel high molecular-weight epoxy resins. The products were obtained by the reaction of epoxidized soybean oil (ESBO) and bisphenol A (BPA), using a modern and pro-ecological modification of the well-known method of the synthesis of epoxy resins, called „the epoxy fusion process”. Based on obtained spectrograms, the manner in which substrates reacted with each other during the conducted synthesis was determined. Initially, after the reaction of the oxirane group of ESBO with hydroxyl group of BPA, subsequent reactions occurred, involving other molecules of bisphenol and remaining oxirane rings of epoxidized vegetable oil or the reaction of free phenolic group with following macromolecule of modified oil. It was found that the final product of the polyaddition (ESBO_BPA), obtained by the epoxy fusion process conducted in bulk consists of macromolecules with various structure. First, smaller oligomers such as 1ESBO+1BPA and ESBO+2BPA were formed, which, as the reaction proceeded, they rapidly reacted with each other forming larger macromolecules: 2ESBO+2BPA, ESBO+3BPA, 2ESBO+3BPA, 3ESBO+3BPA and 3ESBO+4BPA. Based on the course of the ESBO_BPA polyaddition process in the registered m/z range, it was found that 1ESBO+1BPA tends to react with other substrates from the reacting mixture to create a linear product. Bisphenol A is a rigid element, which connects the elastic alkyl chains of epoxidized soybean oil in the obtained macromolecule.

KEYWORDS: soybean oil, epoxy resin, epoxy fusion process, MALDI-TOF MS


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INTRODUCTION Recently, a growing interest in polymer materials obtained from renewable resources has been observed

1

due to their low production cost and reduced environmental impact, the unstable prices of

petrochemical raw materials and the imminent prospect of their exhaustion. Among all available 'green' raw materials, vegetable oils are the most popular and they are already widely used for the synthesis and modification of various industrial materials. For several years, rapid growth in worldwide production of vegetable oils has been observed: 90.5 million tonnes in 2000 and 175.6 million tonnes in 2015 2. Further dynamic growth in the production of vegetable oils and their wider application for various purposes other than food is expected in the years to come 3. A unique example of the application of vegetable oils is the synthesis and modification of polymeric materials, such as epoxy resin, which are one of the most versatile thermosets. Cured epoxy resins are characterized by very good mechanical properties, chemical resistance, and adhesive strength. Additionally, they exhibit low cure shrinkage, which makes them suitable for structural matrix materials, structural adhesives, and protective coatings 4. However, they have limitations, such as easily cracking under stress or impact and brittleness 5. One of the ideas in order to surpass these disadvantages and improve the physico-chemical properties of epoxy resins is the application of modified vegetable oils, which are used as reactive diluents or could be apply to partially replace the traditional petroleum stocks in their synthesis and modification

6-8

. In these applications, long alkyl chains of modified oils are

introduced into the rigid and brittle bisphenol-based epoxy resins as plasticizers 9. One of the most important group among epoxy materials are the high-molecular weight epoxy resins, which are typically used in powder coating. They are obtained via a reaction called the „epoxy fusion process” 10-11. This is the reaction between bisphenols and low- or average-molecular-weight epoxy resins. This reaction is conducted in bulk, at a temperature higher than the melting temperature of the raw



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materials, in the presence of catalysts (such as: inorganic bases, tertiary amines, quaternary ammonium salts, phosphines, hydroxyamines or imidazoles), and in inert atmosphere, without the addition of solvents or diluents. Based on the chemistry of the conventional epoxy fusion process applied for the synthesis of the high-molecular weight epoxy resins from petrochemical raw materials, we are conducting studies on the synthesis of novel bio-based epoxies. Our studies indicates that modified vegetable oils can partially replace petrochemical resources. More specifically, epoxidized oils can substitute for low and average molecular weight epoxy resins, and hydroxylated ones can substitute for BPA in the conventional method of epoxy resins synthesis. Moreover, vegetable oils provide better flexibility and wider range of available crosslinking agents (including both: typically used for epoxies - amines or acidic anhydrides, as well as isocyanates, which are usually applied in the polyurethanes technology) for promising novel polymer materials

12-13

. The epoxy fusion process (Figure 1) involves reagents with different functionality: 2 for

bisphenol A and an average more than 3 for modified vegetable oil. Generally, if one of the reagents in polyaddition or polycondensation processes has a functionality greater than 2 this may lead to a polymer with a branched structure and even to crosslinked products. However, it was proved, that skillful conduction of the epoxy fusion process in the presence of the LiCl catalyst allows to obtain the product with designed characteristics, in a liquid form with high density and without gelling of the mixture. The performed reaction of the synthesis of high-molecular bio-based epoxy resins is the reaction of active functional groups: epoxy from modified vegetable oil and hydroxyl from bisphenol. It could be expected that probably, after the formation of 'dimer' in the first stage of the process, there are possible subsequent reactions involving another molecules of bisphenol with the use of remaining oxirane rings of epoxidized vegetable oil (Figure 1 - 2nd reaction) or the reaction of free hydroxyl group with following


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macromolecule of modified oil (Figure 1 - 1st reaction). The obtained bio-based epoxy fusion products are characterized by a number-average molecular weights in the range of 1,500-10,000 g/mol 5. The aim of this study is a detailed characterization of the course of the synthesis of highmolecular-weight epoxy resins based on plant oils. We decided to choose for this purpose the mass spectrometry MALDI-TOF. Recently, MALDI-TOF analysis is incorporated into various types of studies, in order to obtain unique information about the structure of materials. Here we would like to highlight only a few examples, such as e.g.: structural characterization (of proteins or peptides 14, oligosaccharides 15-16

or lipids and phospholipids that can be found in living organisms

17

, as well as for determination

without the necessity of pre-separation or derivatization of the composition of crude oils and fats, which are used by the cosmetic and food industries 18-19), the investigation of the course of different reactions (e.g.: changes occurring in edible vegetable oil samples, subjected to the thermal stress simulating deepfrying conditions

20

, direct observation of the active species in the polymerization of cyclic ester

polymerization initiated with tin(II) octoate 21, the determination of the structure of epoxy resins obtained throughout the synthesis under the microwave irradiation 22). In this manuscript we use MALDI-TOF for the investigation of the course of the polyaddition reaction between modified soybean oil and bisphenol A using the epoxy fusion process, conducted in bulk. The discovery of the exact pathway of the reaction occurring between substrates seems to be crucial due to the conducting the process in controlled manner, resulting in obtaining the final epoxy product characterized by the satisfactory properties and its further application. Especially due to the fact that used reactants are characterized by the functionality greater than 2, leading to the extremely high possibility of gelling of the reacting mixture. So it is tremendously important to determine the structure of all macromolecules present in the reaction medium, with the particular attention to the primary time of branched products formation, and discovering whether these structures are synthesized initially or at the end of the conducted reaction. Moreover, using MALDI-TOF



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analysis we were hoping to determine to what extent selected triglycerides react during the epoxy fusion process. The determination of the functional groups and the GPC analysis, which were previously used for the characterization of the epoxy fusion process of ESBO_BPA gave just the general information about the final product, characterizing it as a whole not as the mixture of a specific macro-species 13, 23.

MATERIAL AND METHODS Materials. In the performed epoxy fusion process epoxidized soybean oil (ESBO, Ergoplast EG, Boryszew, EV = 0.363 mol/100g), bisphenol A (BPA, GE Cartagenie, 99.93%) and LiCl (Merck, pure) were used. The process was carried out in nitrogen atmosphere. Amounts of reagents were calculated with respect to the required properties of the final product (EV ≈ 0.100 mol/100g). In the first step, the epoxidized soybean oil was heated up to 110°C and an appropriate amount of the BPA was added. The reaction mixture was homogenized, followed by adding LiCl (in amount of 0.002 mol per 1 mol of bisphenol A) and increasing the temperature to the desired 160°C. The duration of the process was established experimentally, by monitoring the epoxy value of reacting mixture

5, 24

. The process was

carried out until the assumed content of epoxy groups in the final product was reached. Epoxy and hydroxyl values. The content of epoxy groups (epoxy value, EV) in the investigated products was evaluated according to the standard PN-87/C-89085/13: the samples were dissolved in HCl/1,4dioxane solution (1.9 mol/L) and titrated by NaOH/methanol (0.2 mol/L) in the presence of cresol red as an indicator to the visual change of tint to purple (from light pink through yellow to red/purple). In order to define the hydroxyl value (HV), samples of epoxidized soybean oil and fusion products were dissolved in the solution of catalyst [4(dimethylamine)pyridine in DMF – 0.1 mol/L] and acetic anhydride in DMF (2.4 mol/L). This was followed by intensive stirring for 15 minutes and titration with KOH aqueous solution (1 mol/L) in presence of thymolphthalein until the tint changed from colorless to blue.


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Gel permeation chromatography. The number-average molecular weight ( M n ), weight-average molecular weight ( M w ), and polydispersity (PDI) of the obtained products were determined by Knauer gel-permeation chromatography with two PL-gel columns (300 × 7.5 mm) with grain size 3 µm and MIXED-E pores and a refractive index detector. The equipment was calibrated using standard polystyrene samples in the molecular weight range of 410 to 20,500 g/mol. The analyses were performed at 25°C and tetrahydrofuran dried over metallic sodium, distilled and stabilized with BHT (2,6-bis(1,1-dimethylethyl)4-methylphenol), was used as an as eluent (with eluent flow 0.8 mL/min). MALDI-TOF analysis. 2,5-dihydroxybenzoic acid (DHB, Merck, ≥ 99 (HPLC)), 1,8,9-trihydroxyanthracene

(Dithranol,

Across

Organics,

97%)

and

trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-

propenylidene]malo-nonitrile) (DCTB, Merck, ≥ 99% (HPLC)) were tested as matrix for the MALDITOF analysis. Finally DCTB was used. Samples of the epoxy fusion product were dissolved in tetrahydrofuran (THF), and then applied to the slider as 1 µl droplets in a form of a mixture containing: sample, sodium trifluoroacetate and matrix in a ratio 1:5:25. Subsequently, samples were crystallized rapidly under a warm gas stream. All MALDI-TOF mass spectra were recorded on ultrafleXtreme™ Bruker Daltonics.

RESULTS AND DISCUSSION Epoxidized vegetable oils usually contain more than one oxirane group in the molecule and are able to react with typical hardeners applied for crosslinking of epoxy resins, therefore they can be formally treated as epoxy resins. Working on this basis, the epoxidized derivatives of natural oils were used to substitute for low- or average-molecular-weight resin in the reaction with bisphenol

12, 25

. The

synthesis was conducted in the presence of LiCl as a catalyst. The application of the catalyst was dictated by: (i) the promotion of the reaction of phenol groups of bisphenol A with epoxy groups over the possible



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reaction of secondary hydroxyl groups (obtained by oxirane ring opening) with epoxy groups, as well as (ii) inhibition of branching reaction and in the same time prevention of gelling of the reacting mixture. Based on numerous experiments, it was found that the proposed application of modified vegetable oil in the process of the synthesis of high-molecular weight epoxy resins allows to obtain the fusion product in liquid form, containing diverse number of active hydroxyl and epoxy groups. These functional groups might be utilized for crosslinking purposes. Curing of the bio-resins with a selected hardener (amine, acidic anhydride or isocyanates) produces materials with interesting mechanical properties 13, 26. Previously, the epoxy fusion process of the synthesis of bio-based epoxy resins was monitored by determining the contents of functional groups and average molecular weight during the process

12

.

However, the GPC method, used in previous studies was able to determine only the general characteristics of the individual products, without presenting any information about the reactions that occur in the process. It is worth emphasizing here, that defining the structure of the final product, including the content of active functional groups, together with determining the maximum achievable conversion rate, is important in order to obtain the product with the highest possible molecular weight and in a form suitable for subsequent applications. In order to monitor the course of the synthesis of bio-based epoxy resins by the polyaddition reaction of modified vegetable oil and bisphenol A, using MALDI-TOF, the structure of raw substrates as well as mid-products sampled during the process were characterized. At this point, it is worth mentioning that despite our attempts to select different matrixes for product ionization (including: 2,5dihydroxybenzoic

acid,

1,8,9-trihydroxyanthracene

and

trans-2[3-(4-tert-butylphenyl)-2-methyl-2-

propynylidene]malonitrile), it was possible to ionize and analyze only products of molecular weight up to 4000 g/mol. However, based on the analysis of EV and M w changes, it is known that products with higher molecular weight (even up to 42,000 g/mol), unfortunately not detected by the MALDI-TOF method, are


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generated during the synthesis. Nevertheless, in spite of the identified problems, an attempt was made to analyze the course of the polyaddition reaction of epoxidized soybean oil and bisphenol A in the recorded, narrowed down range of molecular weight. In the first stage of the research, epoxidized soybean oil and bisphenol A were analyzed. It was not possible to record the spectrogram for BPA, most likely due to its low molecular weight and hence potential fragmentation during the analysis. The decomposition of small molecules in the MALDI-TOF is associated with their significantly reduced, compared to large molecules (e.g.: triglyceride macromolecules), ability to disperse energy without breaking chemical bonds. This results in much less vibration and rotation capability 27. The mass spectrum of the epoxidized soybean oil is presented in the Figure S-1 of the Supporting information and the selected values of molecular weight of triglycerides are presented in the Table S-1 of the Supporting information. The MALDI-TOF analysis of ESBO and its products during the polyaddition reaction was performed in the presence of sodium trifluoroacetate, whereby the corresponding m/z signals refer to the individual positive ions formed by the attachment of Na+ cations to the molecules, which were present in the analyzed sample. Bearing in mind that vegetable oil is a mixture of glycerin and various fatty acid residues, both saturated and unsaturated, it was possible to determined the variety of molecular masses of various triglycerides present in the epoxidized soybean oil. The assignment of a given value to corresponding triglyceride structure was made by taking into the consideration the equation: MTAG = M[(glycerol-3OH)+M(FA1+FA2+FA3-3H). MTAG stands for the mass of triglyceride, as a mixture of glycerin esters M(glycerol-3OH) and fatty acids M(FA1+FA2+FA3-3H). On the mass spectrum the signal with the highest intensity is attributed to [M+H]+, while other m/z signals, corresponds to the multi-charged [M+nH]n+ and [nM+H]+ ions. For the purposes of the interpretation of MALDI-TOF results, the acronyms: ESBO, stands for [M+H]+ and nESBO - for [nM+H]+. Whereas M, due to the



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polydispersity of soybean oil, is identified as the molar mass of the various triglycerides. On this basis, the signal m/z equal 1864.5 might be assigned to the presence of LLL+PPL+4H, LLL+PPL+4H, LLnO+PPL+4H, LLnO+PSS, LLL+LnPP, LLL+OSP, LLL+PSO, LnO+LnPP, LnO+OSP or LnO+PSO. Additionally, the value of signals m/z on MALDI-TOF spectra indicates the presence of diglycerides, triglycerides and oligomers in the form of sodium adducts. It was possible to define about 20 different configurations of fatty acids in triglycerides present in the epoxidized soybean oil (Table S-1 of the Supporting information). Additionally, it was found that certain m/z signals may be assigned to the presence of triglycerides of various sets of fatty acids (e.g. m/z=969.8 corresponds to OLS, LLS, OLnS or m/z=997.7 to LLL, LLnO). There are also signals, which were assigned to the products of the side reactions which occurred during the oxidation process of raw soybean oil (e.g.: LLnL–H2O, LnLnO– H2O, and LLnLn–H2O for the signal m/z = 1029.7). The presence of these signals indicates that in the case of some triglycerides, an opening reaction of the newly formed oxirane rings with water present in the reaction system occurred (Figure 2). In the next step of our research, we synthesized novel bio-based epoxy resins by the polyaddition reaction of epoxidized soybean oil with bisphenol A, conducted in bulk, using the fusion method (Table S-2 of the Supporting information). A two-stage change of values both the content of epoxy groups and the molecular weight was observed. Up to around 12 hours of conducting the process, the decrease of the epoxy value and the corresponding adequate increase of molecular weight was relatively slow. During that time, the epoxy value decreased by just 12 % (EVESBO_BPA_12h = 0.262 mol/100g). The sharpest change of mentioned values was observed in the last two hours of the process. Starting from 16 h – a significant decrease of the epoxy value was observed along with an increase of molecular weight and viscosity of the reacting mixture (EV = 0.112 mol/100g, M n = 2324 g/mol, M w = 6363 g/mol, PDI = 2.74 and η = 147.58 Pa·s, Table S-2 of the Supporting information). These observations may indicate that in


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the first stage of the process (up to 12 h) the reaction between macromolecules of vegetable oil and bisphenol A is dominant. In final stage, an intensively increasing viscosity is characteristic for the formation of products with much higher molecular weights, which result from the combination of earlier formed oligomers of epoxy fusion product characterized by smaller molecular weights. The discussed model of observed changes of the content of active functional groups as well as average molecular weight, along with the significant increase of viscosity in the final stage of the process are characteristic features of the polyaddytion reaction 28-29. The increase in the molecular weight of the obtained polymer is closely related to the degree of conversion of the active functional groups. Although, in general the concentration of the substrates decreases rapidly in the first stage, a proper polymer is formed only after reaching a high degree of conversion. That is why for a long time, the concentration of short oligomers in the reacting mixture is relatively large, finally leading to continuous reaction of one another. After 18 h, we obtained a bio-epox y fusion product containing epox y and h ydrox yl active groups at the level of EV = 0.118 mol/100 g, HV = 144 mg KOH/g (Table S-2 of the Supporting information). In the next step of the analysis, MALDI-TOF was performed on samples taken at specified intervals during the polyaddition process of epoxidized soybean oil with bisphenol A (Figure 3, Table 1). Based on the presented mass spectra, it was found that, as a result of the reaction, the group of m/z signals characteristic of the substrates gave the corresponding m/z signal group for the reaction product. The MALDI TOF spectrogram of the sample obtained after the first hour (Figure S-2 of the Supporting information) presents, mostly signals from unreacted soybean oil (m/z = 997.7-1323.9, 1906.5, 2064.4 and 2867.2-2997.2). There are also first signals from the products of the reaction of epoxidized soybean oil and bisphenol. Listing them in order of abundance, the signals, which are characteristic for adducts are: 1ESBO+BPA (at m/z equals 1247.9; 1477.0 and 3092.3-3193.3) and 2ESBO+BPA (m/z = 2088.6-2214.5). The mentioned products were obtained by the reaction between the



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epoxy groups of modified vegetable oil and the hydroxyl group of bisphenol (1ESBO+BPA), and later or parallel to that, by the reaction with another macromolecule of epoxidized soybean oil (2ESBO+BPA). In the mass spectrogram there are also single signals of other adducts, such as 1ESBO+2BPA (1850.4; 1878.5 and 3347.4), ESBO+3BPA (1668.2 and 1696.2), 1ESBO+4BPA (3886.9 and 3929.9), and 2ESBO+2BPA (2302.7). In the mass spectrogram of the next sample, collected at 3h (Figure 4A), the signals derived from unreacted epoxidized soybean oil, as well as all signals characteristic for adducts 1ESBO+BPA and 2ESBO+BPA, are still predominant. The triglycerides used in the applied epoxidized soybean oil are characterized by a complex and diverse structure, resulting from the presence of fatty acid residues of different lengths of alkyl chains and different amounts of epoxy groups in their structures. Therefore, for the purpose of detailed analysis of the changes, which took place in the reaction mixture during the first three hours of the polyaddition process, several samples of triglycerides with different structures were selected. The intensity ratio of their m/z signals was then determined. The epoxidized soybean oil, which was used in the experiment, amongst other triglycerides, contains PLO (m/z = 927.7) and LLO (as well as OLnO, m/z = 983.8). The PLO is made of epoxidized palmitic, linoleic and oleic acids and thus contains 3 oxirane rings (respectively - one oxirane group in the oleic acid residue and two in the linoleic acid). The LLO is the ester of glycerol and the residues of epoxidized: linoleic, linoleic and oleic fatty acid residues (respectively - OLnO contains epoxidized: oleic, linolenic and oleic fatty acid). In order to characterized the changes during the polyaddition process, we analyzed the changes of the intensity of selected m/z signals as well as their ratios: Ipr/I1ESBO+1BPA, I3/I1 and I6/I3. Based on the results, it was found that 1ESBO+1BPA is formed at the initial stage of the discussed reaction and at the same time becomes a transition product for the next emerging macromolecules in the system. Due to that, it was highlighted and treated as the reference product (Table 2). In the Table 2 the products with the highest m/z intensity are marked in red. It was


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found that the intensity ratio I3/I1 of the corresponding m/z signals on the MALDI-TOF spectra for all newly-formed adducts (1ESBO+1BPA, 1ESBO+2BPA, 1ESBO+3BPA, 2ESBO+1BPA, 2ESBO+2BPA, 2ESBO+3BPA and 3ESBO+3BPA) indicates a smaller amount of suitable products in the sample taken after the 3rd hour than in the sample after the 1st hour of the reaction. Considering these changes on an example PLO triglyceride, after 3 h of conducting the epoxy fusion process it was found that there is four times less 1ESBO+1BPA product, and 3 times less 2ESBO+1BPA adduct in the mixture. Only the 3ESBO+3BPA oligomer of LLO (OLnO) triglyceride showed an increase in the intensity ratios (I3/I1) of m/z signals. Additionally, taking into account the intensity of the m/z signals of the corresponding products that were formed in the subsequent stages of the process in relation to the intensity of m/z signals of 1ESBO+1BPA (Ipr/I1ESBO+1BPA), it was observed that for PLO triglyceride mainly: 2ESBO+1BPA and 1ESBO+2BPA are created. While for LLO - 2ESBO+1BPA and 1ESBO+3BPA are created. Based on the above observations, it can be expected that during the first three hours of the ESBO_BPA polyaddition process, immediately after the initial stage, further reactions are taking place and they involve the newlycreated products, resulting in formation of oligomers with significantly higher molecular weight. In addition, considering the products for which m/z signals are most commonly found in the MALDI-TOF spectra, we calculated the ratios: I1ESBO+1BPA/IESBO+2BPA and IESBO+BPA/I2ESBO+1BPA as well as I2ESBO+2BPA and I2ESBO+1BPA/I2ESBO+2BPA (Table 3). In the case of the highlighted triglycerides, in the first three hours of reaction, more 2ESBO+1BPA than 1ESBO+2BPA products were formed. This may indicate a greater tendency for 1ESBO+2BPA to participate in subsequent reactions to form macromolecules with higher molecular weights. Additionally, the results could also indicate a greater predisposition to form products with linear rather than branched structures. We also analyzed the ratio of the intensity of the m/z signals attributed to the emerging macromolecules and the corresponding signals from the potential initial products from which they could be derived (Table 4). It may thus be assumed



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that during the first three hours of the reaction, 1ESBO+1BPA shows a higher tendency to react with another epoxidized soybean oil molecule than with BPA to form 2ESBO+1BPA. On the other hand, it should be kept in mind that the analyzed mixture is a dynamic system and therefore it is not possible to clearly determine the reactivity of 1ESBO+1BPA as it could very quickly become the substrate for subsequent reactions to form molecules with higher molecular weights. Hence, the intensity of the corresponding m/z signals in the sample taken after 3 hours of reaction may be lower. Likewise, 1ESBO+2BPA and 2ESBO+1BPA products formed in the first hour of reaction could sequentially react with macromolecules of soybean oil or bisphenol A to form: ESBO+3BPA and 2ESBO+2BPA or 2ESBO+2BPA and 3ESBO+2BPA, respectively. Meanwhile, considering the calculated ratio: I1ESBO+2BPA_1h/I1ESBO+3BPA_1h and I1ESBO+2BPA_1h/I2ESBO+2BPA_1h for the product 1ESBO+2BPA, it was found that it shows a similar predisposition towards formation of both ESBO+3BPA, as well as 2ESBO+2BPA (I1ESBO+2BPA_1h/I1ESBO+3BPA_1h = 1.35, and I1ESBO+2BPA_1h/I2ESBO+2BPA_1h = 1.25). In the case of the sample ESBO_BPA_6h, an increase of intensity was observed for m/z signals from products formed by the attachment of two and three BPA molecules. As the reaction progresses, the intensity of the signals from the non-reacted epoxidized soybean oil decreases. At the same time, in the case of PLO triglyceride, 3ESBO+3BPA had the highest intensity of m/z signal, whereas for LLO (OLnO) – it was 1ESBO+1BPA. When it comes to the changes in the ratio Ipr/I1ESBO+1BPA for PLO, most of the products are created in the form of 2nESBO+1BPA and 3nESBO+3BPA (Ipr/I1ESBO+1BPA equal 2.14 and 2.59, respectively). On the other hand, for LLO triglyceride (OLnO), in the period of 3-6 h, 1nESBO+1BPA presented the highest intensity of m/z signals. The observed differences are probably related to the different structure of the fatty acid residues of the individual triglycerides, and thus the different availability of the active functional groups, which are involved in the polyaddition reaction.


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Next, in the sample collected at 12 h, a significant decrease is observed in the intensity of signals characteristic for both ESBO and ESBO+BPA, respectively for the regions m/z = 1850.3-2064.5 (for nESBO) and 2130.6-2200.5 (for 1nESBO+1BPA). The mass spectrogram of the product obtained within the 18th hour of the process (Figure 5) presents signals from the adduct 1nESBO+1BPA (m/z = 1113.81268.0), which is dominant both in terms of number and their intensities. There are also signals characteristic of 1nESBO+2BPA (at m/z = 1341.9-1734.2), as well as much larger macromolecules: 2nESBO+1BPA (at m/z = 2120.5-2302.7), 2nESBO+2BPA (with m/z = 2331.7-2853.0), 1nESBO+3BPA (e.g.: at m/z = 2558.8) and 1nESBO+3BPA (e.g.: at m/z = 2712.9). In order to perform a detailed analysis of the process over the period of the 12th-18th hours of the polyaddition reaction, the intensity ratios of m/z signals attributed to certain products in the reaction mixture was determined (Table S-3 of the Supporting information). In the case of the PLO triglyceride, at the final stage of polyaddition (16-18 h), the intensity of the m/z signals for 1ESBO+1BPA and 2ESBO+1BPA was increased due to the reaction of BPA with ESBO and reaction of 1ESBO+1BPA with another oil molecule. The dominant signal is 1ESBO+1BPA. A similar regularity was also observed in the case of a triglyceride giving a signal at m/z = 983.8 containing epoxidized LLO or OLnO. At the same time, taking into consideration the determined intensity ratios of I1ESBO+1BPA/IESBO+2BPA and I1ESBO+1BPA/I2ESBO+1BPA, it can be assumed that 1ESBO+1BPA is equally likely to be involved in the formation of 1ESBO+2BPA and 2ESBO+1BPA. On the spectrograms of all samples collected during subsequent ESBO_BPA polyaddition reactions, the presence of m/z signals characteristic of epoxidized soybean oil was found. As the reaction progresses, their intensity decreases but does not disappear completely, even in the spectrum of the final reaction product (ESBO_BPA_18h). The observed phenomenon is characteristic for a polyaddition reaction carried out in bulk by the fusion method, where reactions with substrates can take place during the whole process rather than just in the beginning


28

.


Page 16 of 47

Moreover, as in the previously analyzed time interval (1-6 h) of the ESBO_BPA polyaddition reaction, 1ESBO+2BPA and 2ESBO+1BPA products presumably reacted with macromolecules of soybean oil or bisphenol A to form ESBO+3BPA and 2ESBO+2BPA or 2ESBO+2BPA and 3ESBO+2BPA. As the reaction progresses, it is expected that the reaction will take place with all the distinguished products created in the earlier stages of the process. In order to complete the above interpretation we analyzed the content of active functional groups, the structure of the final product and the changes of molecular weight in the subsequent stages of the reaction. The process was terminated when the content of epoxy groups in the reaction mixture was at the level of 0.118 mol/100 g, which was very close to the founded value of LE ≈ 0.100 mol/100 g. Additionally, in the final stage of the process a significant increase in the viscosity of the reaction mixture was discovered. The phenomenon observed here was also found in polyaddition reactions conducted by the fusion method, which were described in the literature

28

. Due to the rapidly increasing viscosity of the

system and the limited mobility of large molecules, access to the individual reactants in the system is impeded. Hence, the macromolecules with the higher molecular weights are formed by the reaction between the molecules, which are close to each other. Undoubtedly, the observed changes are related to the increase in the size of the created macromolecules due to the reaction between the products formed in earlier stages of the process, leading to the formation of macromolecules with significantly higher molecular weights (GPC chromatogram ESBO_BPA: Figure S-3 and Table S-2 of the Supporting information). The increasing viscosity of the reacting mixture may also explain the previously indicated continuous presence of substrates in the system. Based on the GPC analysis, oligomers with a maximum molecular weight of 3790-4150 g/mol are formed within the first six hours of reaction. In turn, products with significantly higher molecular weights, up to 17,200 g/mol for ESBO_BPA_12h and 42,000 g/mol for the sample of the final polyaddition product - EOS_BPA_18h, are formed.


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CONCLUSION The aim of this study was to determine in detail using MALDI-TOF the mechanism of the synthesis of high-molecular-weight epoxy resins based on plant oils, without the necessity of previous separation or derivatization of the complex mixture containing modified vegetable oil. Despite the fact that collected samples include products with a molecular weight as high as 42,000 g/mol, it was possible to ionize and examine only those with a molecular weight up to 4,000 g/mol. A decrease was observed in the intensity of the signals attributed to subsequent products of PLO triglyceride within the first six hours of the reaction. Only for the 3ESBO+3BPA oligomer of LLO (OLnO) triglyceride, an increase in the ratio of intensity was detected in the corresponding m/z signals for samples collected after the 1st and 3rd hour of the process. On the other hand, based on the intensity of the m/z signals of the corresponding products that are formed in the subsequent stages of the process in relation to the intensity of m/z signals of 1ESBO+1BPA (Ipr/I1ESBO+1BPA), it was discovered that in the case of PLO - mainly 2nESBO+1BPA and 1nESBO+2BPA are formed, whereas in the case of LLO - 2nESBO+1BPA and 1nESBO+3BPA are formed. The value of Ipr for highlighted products decreased at the initial stage of polyaddition, which indicates that they are not the main products of the analyzed reaction but only the intermediate products (Figure 6). The observed decrease indirectly confirms that, as the reaction progresses, significantly larger products are formed, which are not registered on the mass spectrogram, but their presence has been established on the basis of GPC analysis. At the end of the process, the intensity of the m/z signals of the individual products had increased. Most likely, on the basis of the MALDI-TOF analysis, the phenomenon is related to the presence of unreacted epoxidized soybean oil in the reacting mixture. Additionally, since BPA (not detected by MALDI-TOF, but visible on the GPC chromatogram) and ESBO are present in the reacting system throughout the entire process, even in the final stage, the reaction to form 1ESBO+1BPA product as well as other more complex structures is possible. For all the identified products (Table 2 and



Page 18 of 47

Table S-3 of the Supporting information), quite significant values of the intensity of m/z signal were found. It may indirectly be explained that, as more complex oligomers are formed, the long chains of macromolecules of intermediate products become tangled with each other, hindering proper orientation of subsequent adducts against each other, thereby limiting access to active functional groups. As a result, in the final stage of the process, smaller molecules, which are more mobile, react more easily with each other. MALDI-TOF not only allowed for analysis of the reactions occurred during epoxy fusion process, but also, due to the detection of unreacted epoxidized soybean oil throughout the process, confirmed the reaction pattern, which is typical for polyaddition in bulk conducted by the fusion method. Here, alike in a typical polyaddition process conducted in bulk, the reaction with starting substrates may take place throughout the entire process, not only in the initial step. Moreover, MALDI-TOF allowed for to indirect analysis of the polyaddition process of modified soybean oil and BPA in terms of the degree of branching of the formed macromolecules. Based on the course of the ESBO_BPA polyaddition process in the registered m/z range, it has been found that 1ESBO+1BPA tends to produce a linear product - bisphenol A is a rigid component of the molecule by which elastic alkyl chains of epoxidized soybean oil are connected.

SUPPORTING INFORMATION MALDI-TOF spectra of ESBO and ESBO_BPA_1h along with the interpretation, GPC chromatogram of intermediate and final products obtained during the epoxy fusion process of epoxidized soybean oil and bisphenol A

REFERENCES (1) Biermann, U.; Friedt, W.; Lang, S.; Luhs, W.; Machmuller, G. New syntheses with oils and fats as renewable raw materials for

the

chemical

industry.

Angew.

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Int.

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2000,

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39,

2206-2224,

DOI

10.1002/1521-

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(2) http://www.statista.com/statistics/263978/global-vegetable-oil-production-since-2000-2001/ (online access: 28.01.2017). (3) Schmidt, J. H. Life cycle assessment of five vegetable oils. J. Clean. Prod. 2015, 87, 130-138, DOI 10.1016/j.jclepro.2014.10.011. (4) Czub, P.; Bończa-Tomaszewski, Z.; Penczek, P.; Pielichowski, J. In Chemistry and technology of epoxy resins; Structure and properties of compounds and epoxy resins., 4th ed., WNT, Warsaw, pp. 20-36. (5) Czub, P. Synthesis of high-molecular-weight epoxy resins from modified natural oils and Bisphenol A or Bisphenol A-based epoxy resins. Polymer. Adv. Tech. 2009, 20(3), 194-208, DOI 10.1002/pat.1252. (6) Czub, P. Application of modified natural oils as reactive diluents for epoxy resins. Macromol. Symp. 2006, 242(1), 60-64, DOI 10.1002/masy.200651010. (7) Czub, P. Characterization of an Epoxy Resin Modified with Natural Oil-Based Reactive Diluents. Macromol. Symp. 2006, 245-246, 533–538, DOI 10.1002/masy.200651377. (8) Czub, P.; Franek I. Epoxy resins modified with palm oil derivatives-- preparation and properties. Polimery. 2013, 58(2), 135-141, DOI 10.14314/polimery.2013.135. (9) Czub, P. Epoxy compositions with use of modified vegetable oils. Polymers. 2008, 53(3), 182-189. (10) Jackson, R.J.; Corley, L.S. (Shell Oil Company), 1988. Epoxy Fusion Process. U.S. Patent 4732 958. (11) Fache, M.; Viola, A.; Auvergne, R.; Boutevin, B.; Caillol, S. Biobased epoxy thermosets from vanillin-derived oligomers. Eur. Polym. J., 2015, 68, 526-535, DOI 10.1016/j.eurpolymj.2015.03.048. (12) Czub P. In Modified natural oils and the products of chemical degradation of waste poly(ethyleneterephthalate) as environmentally friendly raw materials for epoxy resins, Publishing House of the Cracow University of Technology, Cracow, 2008, pp. 14-18. (13) Sienkiewicz, A.; Czub, P. Novel bio-based epoxy-polyurethane materials from modified vegetable oils-synthesis and characterization. Express Polym. Lett. 2017, 11(4), 308-319, DOI 10.3144/expresspolymlett.2017.30. (14) Fuchs, B.; Schiller, J. Application of MALDI-TOF mass spectrometry in lipidomics. Eur. J. Lipid Sci. Technol. 2009, 111, 83-98, DOI 10.1002/ejlt.200800223. (15) Mechref, Y.; Novotny, M. V.; Krishnan, C. Structural characterization of oligosaccharides using MALDI-TOF/TOF tandem mass spectrometry. Anal. Chem. 2003, 75(18), 4895-4903, DOI 10.1021/ac0341968. (16) Laremore, T. N.; Zhang, F.; Linhardt, R. Ionic liquid matrix for direct UV-MALDI-TOF-MS analysis of dermatan sulfate and chondroitin sulfate oligosaccharides. J. Anal. Chem. 2007, 79(4), 1604-1610, DOI 10.1021/ac061688m.



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(17) Fuchs, B.; Süß, R.; Schiller, An update of MALDI-TOF mass spectrometry in lipid research. J. Prog. Lipid Res., 2010, 49(4), 450-475, DOI 10.1016/j.plipres.2010.07.001. (18) Saraiva, S. A.; Cabral, E. C.; Eberlin, M. N.; Catharino, R. R. Amazonian vegetable oils and fats: fast typification and quality control via triacylglycerol (TAG) profiles from dry matrix-assisted laser desorption/ionization time-of-flight (MALDI− TOF) mass spectrometry fingerprinting. J. Agric. Food Chem. 2009, 57(10), 4030-4034, DOI 10.1021/jf900043u. (19) Cozzolino, R.; De Giulio, B. Application of ESI and MALDI-TOF MS for triacylglycerols analysis in edible oils. European journal of lipid science and technology. Eur. J. Lipid Sci. Technol. 2011, 113(2), 160-167, DOI 10.1002/ejlt.201000429. (20) Picariello, G.; Paduano, A.; Sacchi, R.; Addeo, F. MALDI-TOF mass spectrometry profiling of polar and nonpolar fractions in heated vegetable oils. J. Agric. Food Chem. 2009, 57(12), 5391-5400, DOI 10.1021/jf9008795. (21) Kowalski, A.; Duda, A.; Penczek, S. Mechanism of cyclic ester polymerization initiated with tin (II) octoate. 2. macromolecules fitted with tin (II) alkoxide species observed directly in MALDI− TOF spectra. Macromol. 2000, 33(3), 689-695, DOI 10.1021/ma9906940. (22) Bogdal D.,; Gorczyk J.; Kwasek B. Microwave-assisted synthesis of solid epoxy resins: study of molecular weight by GPC and MALDI-TOF/MS. ACS Sustain. Chem. Eng. 2016, 4(6), 3024–3031, DOI 10.1021/acssuschemeng.5b01786. (23) Sienkiewicz, A.; Czub, P. The unique activity of catalyst in the epoxidation of soybean oil and following reaction of epoxidized product with bisphenol A. Ind. Crop. Prod. 2016, 83, 755-773, DOI 10.1016/j.indcrop.2015.11.071 (24) Jackson R. J. (Shell Oil Company): Epoxy Fusion Catalyst and Process, U.S. Patent 4 829 141, United States (1989). (25) Czub, P.; A comparison of the syntheses of high molar mass epoxy resins on the basis of two groups of modified vegetable oils. Macromol. Symp. 2009, 277, 162–170, DOI 10.1002/masy.200950320 (26) Czub, P.; Kasza, P. Mechanical properties of the cured using isocyanate product of modified soybean oil and epoxy resin. Polimery, 2014, 59(6), 466-476, DOI 10.14314/polimery.2014.466 (27) Calvano C. D.; Palmisano F.; Zambonin C. G., Laser desorption/ionization time of flight mass spectrometry of triacylglycerols in oils. Rapid Commun. Mass Spectrom. 2005, 19, 1315-1320, DOI 10.1002/rcm.1933 (28) Teegarden D. M. In Polymer Chemistry: Introduction to an Indispensable Science, 1st ed., NSTA Press, Arlington, 2004. (29) Zhang, M.; June, S. M.; Long, T. E. Principles of step-growth polymerization (polycondensation and polyaddition). Polym. Sci., 2012, 5, 7-47, DOI 10.1016/B978-0-444-53349-4.00131-X.


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FIGURES AND TABLES: Figure 1. Synthesis of high-molecular weight epoxy resins through the epoxy fusion process Figure 2. The reaction of the formation of by-products (LLnL-H2O, LnLnL-H2O and LLnLn-H2O) in the epoxidation of LLnO Figure 3. MALDI-TOF mass spectrum of sodium cationized species (M+Na)+ of samples of products during the epoxy fusion process of epoxidized soybean oil and bisphenol A Figure 4. MALDI-TOF mass spectrum of sample obtained during: 3rd (A) and 12th (B) hour of conducting the epoxy fusion process of the high-molecular weight bio-epoxy resins Figure 5. MALDI-TOF mass spectrum of sample obtained in the 18th hour of the epoxy fusion process of epoxidized soybean oil and bisphenol A illustrating the variety of obtained products during the synthesis of the high-molecular weight bio-epoxy resins Figure 6. Synthesis of high-molecular weight epoxy resins through the epoxy fusion process

Table 1. Attribution of the selected ions observable in the MALDI-TOF spectra during ESBO_BPA polyaddition Table 2. Changes of the intensity of selected m/z signals for the samples collected after 1st, 3rd and 6th hour of conducting the polyaddition process Table 3. Changes of the intensity of m/z signals for selected probable products present in the reacting mixture during the polyaddition process ESBO_BPA Table 4. Changes of the intensity of m/z signals of subsequent products of ESBO_BPA polyaddition


ACS Sustainable Chemistry & Engineering O

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

O

O

O

O

OH

O

O

O

O

OH O

O

O

O

O

O

OH

O

(1) O HO

OH

OH

O

OH

O OH

O

OH

+ O

O

BPA (2)

HO

O

O OH

OH

Figure 1. Synthesis of high-molecular weight epoxy resins through the epoxy fusion process


OH

O

O

ESBO

OH

O

O

O

O

O O

O

O

O

O

OH

BPA

O

OHO

O

160°C catalyst

O

O

ESBO

O

+

O

OH

O

HO

Page 22 of 47

OH

OH

Page 23 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


oleic acid O

O

O

O O o

linolenic acid

60-65 C

H2O2

O

CH3COOH H2SO4

O

O

LLnO

linoleic acid O

O

O

O

O

O

O

O O

+ H2O

OH OH

O

O

O

Epoxidized LLnO

O

O

O

O

O

O

O

O O

LLnO-H2O (one of the possible products)

Figure 2. The reaction of the formation of by-products (LLnL-H2O, LnLnL-H2O and LLnLnH2O) in the epoxidation of LLnO



Page 24 of 47

EV = 0.296 mol/100g

EV = 0.266 mol/100g

EV = 0.262 mol /100g

EV = 0.213 mol/100g

EV = 0.183 mol/100g

EV = 0.112 mol/100g

Figure 3. MALDI-TOF mass spectrum of sodium cationized species (M+Na)+ of samples of products during the epoxy fusion process of epoxidized soybean oil and bisphenol A


Page 25 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. Attribution of the selected ions observable in the MALDI-TOF spectra during ESBO_BPA polyaddition Time 1

3

6

12

16

18

m/z 1934.5 2144.6 2162.6 3092.3 3347.4 3929.9 1906.5 2050.4 2158.6 2231.5 2442.7 3078.3 1057.7 1225.8 1654.2 2130.6 2316.7 2442.7 2498.8 1341.9 1608.2 1892.3 2144.6 2200.5 2330.7 2586.8 2656.7 2711.9 1325.9 1426.0 1734.2 2200.5 2499.8 2709.9 2924.0 3320.4 4142.9 1197.9 1309.9 1440.0 1552.0 1734.2 2078.5 2302.7 2442.7 2558.8 2657.1 3547.5

m/z-Na 1911.5 2121.6 2139.6 3069.3 3324.4 3906.9 1883.5 2027.4 2135.6 2208.5 2419.7 3055.3 1034.7 1202.8 1631.2 2107.6 2293.7 2419.7 2475.8 1318.9 1585.2 1869.3 2121.6 2177.5 2307.7 2563.8 2633.7 2688.9 1302.9 1403.0 1711.2 2177.5 2476.8 2686.9 2901.0 3297.4 4119.9 1174.9 1289.9 1417.0 1529.0 1711.2 2055.5 2279.7 2419.7 2535.8 2634.1 3524.5

Interpretation nESBO (1911.5) 2nESBO+BPA (2121.9) nESBO+BPA (2139.8) nESBO+BPA (3086.5)-OH nESBO +2BPA (3328.8) nESBO+4BPA (3901.4) ESBO (1883.5) ESBO (2027.4) 2nESBO+BPA (2149.7)-CH2 ESBO+BPA (2209.7) 2nESBO +2BPA(2406.0)+CH2 2nESBO+3BPA (3058.7) ESBO ESBO+BPA (1203.0) ESBO+3BPA (1631.2) 2nESBO+BPA (2093.9) 2nESBO+2BPA (2294.0) ESBO+2BPA (2410.1) 2nESBO+2BPA (2462.0)+CH2 ESBO+2BPA nESBO+2BPA (1588.5) nESBO (1869.5) 2nESBO+BPA (2121.9) nESBO+BPA (2177.7) 2nESBO+2BPA (2222.2)-CH2 nESBO+3BPA(2582.4)-CH2 2nESBO+3BPA (2634.3) ESBO +3BPA (2690.3) ESBO (1286.9+CH2) ESBO +2BPA (1403.4) nESBO+2BPA (1729.6)-CH2 2nESBO+BPA (2177.7) 2nESBO+2BPA (2462.0)+CH2 2nESBO +3BPA (2698.3)-CH2 ESBO(2901.21) ESBO+2BPA (3286.8)+CH2 2nESBO+BPA (4115.3) ESBO+BPA (1175.1) ESBO (1286.9) nESBO+2BPA (1417.3) nESBO+BPA (1515.2)+CH2 nESBO+2BPA (1729.6)-CH2 nESBO (2041.4)+CH2 2nESBO+BPA (2177.7)+2H 2nESBO+2BPA (2414.0) ESBO+3BPA (2522.3) 2nESBO+3BPA (2634.3) nESBO+3BPA (2522.3)+2H



997,7

ESBO (A)

3500

4084,0

3000

1524,1

4213,1

1453,9

1296,0

1225,8

1155,9

1029,7

1ESBO+1BPA

3547,5

2500

1454,0

1225,8

1309,9

3375,4

3105,3 3081,0

2130,0

1892,4

2000

2867,0

1500

2400,7

1000

2ESBO+2BPA

2ESBO+2BPA 1ESBO+1BPA

1734,2

1436,9

0

983,7 1027,7

885,7

927,7

(B)


1154,9

1043,7 1057,7

885,7

941,7


1ESBO+1BPA 2997,2

2414,7

1836,4 1976,5

2116,6 2186,6 2260,5

1ESBO+1BPA

Intensity [a.u.]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 47

2ESBO+1BPA

4000

4500

5000

m/z Figure 4. MALDI-TOF mass spectrum of sample obtained during: 3rd (A) and 12th (B) hour of conducting the epoxy fusion process of the high-molecular weight bio-epoxy resins


Page 27 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Table 2. Changes of the intensity of selected m/z signals for the samples collected after 1st, 3rd and 6th hour of conducting the polyaddition process ESBO

PLO

LLO OLnO

Product

m/z

ESBO+1BPA ESBO+2BPA ESBO+3BPA 2ESBO+1BPA 2ESBO+2BPA 2ESBO+3BPA 3ESBO+3BPA ESBO+1BPA ESBO+2BPA ESBO+3BPA 2ESBO+1BPA 2ESBO+2BPA 2ESBO+3BPA 3ESBO+3BPA

1155.99 1384.28 1612.57 2083.69 2311.98 2540.27 3467.97 1212.09 1440.38 1668.67 2195.89 2424.18 2652.47 3636.27

Time of conducting the process 1 3 6 Intensity [a.u.] a 426 101 69 250 23 34 185 19 67 477 150 148 200 70 69 121 9 37 170 104 179 455 80 180 146 16 36 240 73 111 375 103 147 128 80 31 98 75 27 116 158 87

I3/I1 a, d

I6/I3 a, e

1

0.24 0.09 0.10 0.31 0.35 0.07 0.61 0.17 0.11 0.30 0.27 0.62 0.76 1.36

0.68 1.48 3.52 0.99 0.98 4.11 1.72 2.25 2.25 1.52 1.42 0.39 0.36 0.55

0.59 0.43 1.12 0.47 0.28 0.40 0.32 0.53 0.82 0.28 0.21 0.25

Time of conducting the process 3 Ipr/I1ESBO+1BPAb, c 0.23 0.19 1.49 0.69 0.09 1.03 0.20 0.90 1.27 1.00 0.94 1.97

6 0.49 0.97 2.14 1.00 0.54 2.59 0.20 0.62 0.82 0.17 0.15 0.48

Examples of triglycerides present in the analyzed ESBO: - PLO (triglyceride consisted epoxidized: palmitic, linoleic and oleic fatty acids residues; m/z (PLO) = 927.7) - LLO (triglyceride consisted epoxidized: linoleic, linoleic and oleic fatty acids residues; m/z (LLO) = 983.8) - OLnO (triglyceride consisted epoxidized: oleic, linolenic and oleic fatty acids residues; m/z (OLnO) = 983.8) a I1, I3, I6 – the intensity of m/z signals for the samples collected after 1, 3 and 6 h of conducting the process b I1ESBO+1BPA and Ipr - I1ESBO+1BPA - the intensity of m/z signals for the 1ESBO+1BPA; Ipr intensity of m/z signals for the subsequent products of the reaction of 1ESBO+1BPA with oil or BPA residues c Ipr/I1ESBO+1BPA - the ratio of intensity of selected m/z signals for samples collected in specified time interval during the polyaddition of epoxidized soybean oil and BPA in relation to the intensity of m/z signal for 1ESBO+1BPA, obtained in the first stage of the process d I3/I1 - the ratio of intensity of selected m/z signals for samples collected after 3rd and 1st h of conducting the polyaddition of epoxidized soybean oil and BPA e I6/I3 - the ratio of intensity of selected m/z signals for samples collected after 3rd and 6th h of conducting the polyaddition of epoxidized soybean oil and BPA



Page 28 of 47

Table 3. Changes of the intensity of m/z signals for selected probable products present in the reacting mixture during the polyaddition process ESBO_BPA ESBO* PLO LLO/OLnO

Time of conducting the process 3 6 I1ESBO+1BPA/IESBO+2BPAa 1.7 4.4 2.0 3.1 5.0 5.0 1

Time of conducting the process 3 6 IESBO+BPA/I2ESBO+1BPAa 0.9 0.7 0.5 1.2 0.8 1.2 1

* Examples of triglycerides present in the analyzed ESBO: - PLO (triglyceride consisted epoxidized: palmitic, linoleic and oleic fatty acids residues; m/z (PLO) = 927.7) - LLO (triglyceride consisted epoxidized: linoleic, linoleic and oleic fatty acids residues; m/z (LLO) = 983.8) - OLnO (triglyceride consisted epoxidized: oleic, linolenic and oleic fatty acids residues; m/z (OLnO) = 983.8) a I1ESBO+1BPA, I1ESBO+2BPA, I2SBO+1BPA, - the intensity of m/z signals for the products: 1ESBO+1BPA, 1ESBO+2BPA or 2ESBO+1BPA in samples collected after 1st, 3rd and 6th h of conducting the process


Page 29 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 4. Changes of the intensity of m/z signals of subsequent products of ESBO_BPA polyaddition Ratio of the intensity of the signals m/z of ESBO_BPA products of the polyaddition reaction I1ESBO+1BPA_1h/I1ESBO+2BPA_3h I1ESBO+1BPA_1h/I2ESBO+1BPA_3h I1ESBO+2BPA_1h /I1ESBO+3BPA_3h I2ESBO+1BPA_1h /I2ESBO+2BPA_3h

Value 18.5 2.8 13.1 6.8



400000 1ESBO + 1BPA

300000

Intensity [a.u.]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 47

1ESBO + 2BPA 200000

1ESBO + 3BPA 1ESBO + 4BPA

100000

2ESBO + 1BPA

3ESBO + 3BPA

2ESBO + 2BPA

3ESBO + 4BPA

0 0

1000

1500

2000

2500

3000

3500

4000

4500

m/z Figure 5. MALDI-TOF mass spectrum of sample obtained in the 18th hour of the epoxy fusion process of epoxidized soybean oil and bisphenol A illustrating the variety of obtained products during the synthesis of the high-molecular weight bio-epoxy resins


Page 31 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Possible products present in the reaction mixture OH

O

O O

OH

OH

1ESBO + 1BPA

O

OH

O

OH

HO OH

OH

O

1ESBO + 2BPA

O

OH HO

O

O

HO

OH

OH

O

OH

2ESBO + 3BPA

O O

OH O

HO O

O

OH

OH

OH

1ESBO + 3BPA

HO

OH

OH

O

O

O

O

2ESBO + 2BPA HO

OH

O

OH OH

OH

O

HO

2ESBO + 1BPA O

O

O

OH

O

OH

O

OH

HO O

3ESBO + 4BPA

O

OH

OH

O

3ESBO + 3BPA



OH

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

For Table of Contents Use Only TOC graphic synopsis: Determination of the structure of products obtained during the epoxy fusion process of high-molecular weight epoxy resins using epoxidized soybean oil and bisphenol A.


Page 32 of 47

Page 33 of 47

Soybean oil (SBO) ESBO

epoxidation OH

O

O

O

(1)

O

O

OH

OH

+ O

BPA

OH

BPA

HO

(2)

OH

O

OH

HO

Epoxidized soybean oil (ESBO)

O

O

O

O

O O O

O

OH

O

O OH

OH

OH

O OH

O

OH

OH

O

O

O O O

400000

Epoxy fusion product (?nESBO+?nBPA)

1ESBO + 1BPA 300000

Intensity [a.u.]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20HO 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


1nESBO + 2BPA 200000

1nESBO + 3BPA 1nESBO + 4BPA 3nESBO + 3BPA 2nESBO + 1BPA 2nESBO + 2BPA

100000

0 0

1000

1500

2000

2500

3000

3500

m/z

MALDI-TOF SPECTROGRAM


4000

4500

ACS Sustainable Chemistry & Engineering O

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

O

O

O

O

OH

O

O

O

O

OH O

O

O

O

O

O

OH

O

O

OH

(1)

O O

OH

O OH

O

+ O

HO

OH

OH

BPA (2)

HO

O

O OH

OH



OH

O

O

ESBO

OH

O

O

O

O

O O

O

O

O

O

OH

BPA

O

OH O

O

160°C catalyst

O

O

ESBO

O

+

O

OH

O

HO

Page 34 of 47

OH

OH

Page 35 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


oleic acid O

O

O

O O o

linolenic acid

60-65 C

H 2O2

O

CH3COOH H2SO4

O

O

LLnO

linoleic acid O

O

O

O

O

O

O

O

O + H2O

OH OH

O

O

O

Epoxidized LLnO

O

O

O

O

O

O

O

O O

LLnO-H2O (one of the possible products)

Figure 2. The reaction of the formation of by-products (LLnL-H2O, LnLnL-H2O and LLnLnH2O) in the epoxidation of LLnO



Table 1. Attribution of the selected ions observable in the MALDI-TOF spectra during ESBO_BPA polyaddition Time 1

3

6

12

16

18

m/z 1934.5 2144.6 2162.6 3092.3 3347.4 3929.9 1906.5 2050.4 2158.6 2231.5 2442.7 3078.3 1057.7 1225.8 1654.2 2130.6 2316.7 2442.7 2498.8 1341.9 1608.2 1892.3 2144.6 2200.5 2330.7 2586.8 2656.7 2711.9 1325.9 1426.0 1734.2 2200.5 2499.8 2709.9 2924.0 3320.4 4142.9 1197.9 1309.9 1440.0 1552.0 1734.2 2078.5 2302.7 2442.7 2558.8 2657.1 3547.5

m/z-Na 1911.5 2121.6 2139.6 3069.3 3324.4 3906.9 1883.5 2027.4 2135.6 2208.5 2419.7 3055.3 1034.7 1202.8 1631.2 2107.6 2293.7 2419.7 2475.8 1318.9 1585.2 1869.3 2121.6 2177.5 2307.7 2563.8 2633.7 2688.9 1302.9 1403.0 1711.2 2177.5 2476.8 2686.9 2901.0 3297.4 4119.9 1174.9 1289.9 1417.0 1529.0 1711.2 2055.5 2279.7 2419.7 2535.8 2634.1 3524.5

Interpretation nESBO (1911.5) 2nESBO+BPA (2121.9) nESBO+BPA (2139.8) nESBO+BPA (3086.5)-OH nESBO +2BPA (3328.8) nESBO+4BPA (3901.4) ESBO (1883.5) ESBO (2027.4) 2nESBO+BPA (2149.7)-CH2 ESBO+BPA (2209.7) 2nESBO +2BPA(2406.0)+CH2 2nESBO+3BPA (3058.7) ESBO ESBO+BPA (1203.0) ESBO+3BPA (1631.2) 2nESBO+BPA (2093.9) 2nESBO+2BPA (2294.0) ESBO+2BPA (2410.1) 2nESBO+2BPA (2462.0)+CH2 ESBO+2BPA nESBO+2BPA (1588.5) nESBO (1869.5) 2nESBO+BPA (2121.9) nESBO+BPA (2177.7) 2nESBO+2BPA (2222.2)-CH2 nESBO+3BPA(2582.4)-CH2 2nESBO+3BPA (2634.3) ESBO +3BPA (2690.3) ESBO (1286.9+CH2) ESBO +2BPA (1403.4) nESBO+2BPA (1729.6)-CH2 2nESBO+BPA (2177.7) 2nESBO+2BPA (2462.0)+CH2 2nESBO +3BPA (2698.3)-CH2 ESBO(2901.21) ESBO+2BPA (3286.8)+CH2 2nESBO+BPA (4115.3) ESBO+BPA (1175.1) ESBO (1286.9) nESBO+2BPA (1417.3) nESBO+BPA (1515.2)+CH2 nESBO+2BPA (1729.6)-CH2 nESBO (2041.4)+CH2 2nESBO+BPA (2177.7)+2H 2nESBO+2BPA (2414.0) ESBO+3BPA (2522.3) 2nESBO+3BPA (2634.3) nESBO+3BPA (2522.3)+2H


Page 36 of 47

Page 37 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


EV = 0.296 mol/100g

EV = 0.266 mol/100g

EV = 0.262 mol /100g

EV = 0.213 mol/100g

EV = 0.183 mol/100g

EV = 0.112 mol/100g

Figure 3. MALDI-TOF mass spectrum of sodium cationized species (M+Na)+ of samples of products during the epoxy fusion process of epoxidized soybean oil and bisphenol A



Page 38 of 47

Table 2. Changes of the intensity of selected m/z signals for the samples collected after 1st, 3rd and 6th hour of conducting the polyaddition process ESBO

PLO

LLO OLnO

Product

m/z

ESBO+1BPA ESBO+2BPA ESBO+3BPA 2ESBO+1BPA 2ESBO+2BPA 2ESBO+3BPA 3ESBO+3BPA ESBO+1BPA ESBO+2BPA ESBO+3BPA 2ESBO+1BPA 2ESBO+2BPA 2ESBO+3BPA 3ESBO+3BPA

1155.99 1384.28 1612.57 2083.69 2311.98 2540.27 3467.97 1212.09 1440.38 1668.67 2195.89 2424.18 2652.47 3636.27

Time of conducting the process 1 3 6 Intensity [a.u.] a 426 101 69 250 23 34 185 19 67 477 150 148 200 70 69 121 9 37 170 104 179 455 80 180 146 16 36 240 73 111 375 103 147 128 80 31 98 75 27 116 158 87

I3/I1 a, d

I6/I3 a, e

1

0.24 0.09 0.10 0.31 0.35 0.07 0.61 0.17 0.11 0.30 0.27 0.62 0.76 1.36

0.68 1.48 3.52 0.99 0.98 4.11 1.72 2.25 2.25 1.52 1.42 0.39 0.36 0.55

0.59 0.43 1.12 0.47 0.28 0.40 0.32 0.53 0.82 0.28 0.21 0.25

Time of conducting the process 3 Ipr/I1ESBO+1BPAb, c 0.23 0.19 1.49 0.69 0.09 1.03 0.20 0.90 1.27 1.00 0.94 1.97

6 0.49 0.97 2.14 1.00 0.54 2.59 0.20 0.62 0.82 0.17 0.15 0.48

Examples of triglycerides present in the analyzed ESBO: - PLO (triglyceride consisted epoxidized: palmitic, linoleic and oleic fatty acids residues; m/z (PLO) = 927.7) - LLO (triglyceride consisted epoxidized: linoleic, linoleic and oleic fatty acids residues; m/z (LLO) = 983.8) - OLnO (triglyceride consisted epoxidized: oleic, linolenic and oleic fatty acids residues; m/z (OLnO) = 983.8) a I1, I3, I6 – the intensity of m/z signals for the samples collected after 1, 3 and 6 h of conducting the process b I1ESBO+1BPA and Ipr - I1ESBO+1BPA - the intensity of m/z signals for the 1ESBO+1BPA; Ipr intensity of m/z signals for the subsequent products of the reaction of 1ESBO+1BPA with oil or BPA residues c Ipr/I1ESBO+1BPA - the ratio of intensity of selected m/z signals for samples collected in specified time interval during the polyaddition of epoxidized soybean oil and BPA in relation to the intensity of m/z signal for 1ESBO+1BPA, obtained in the first stage of the process d I3/I1 - the ratio of intensity of selected m/z signals for samples collected after 3rd and 1st h of conducting the polyaddition of epoxidized soybean oil and BPA e I6/I3 - the ratio of intensity of selected m/z signals for samples collected after 3rd and 6th h of conducting the polyaddition of epoxidized soybean oil and BPA


Page 39 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60









Value 18.5 2.8 13.1 6.8


Page 40 of 47

Page 41 of 47

400000 1ESBO + 1BPA

300000

Intensity [a.u.]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1ESBO + 2BPA 200000


100000

2ESBO + 1BPA

3ESBO + 3BPA

2ESBO + 2BPA

3ESBO + 4BPA

0 0

1000

1500

2000

2500

3000

3500

4000

4500




Page 42 of 47


O

O O

OH

OH

1ESBO + 1BPA

O

OH

O

OH

HO OH

OH

O

1ESBO + 2BPA

O

OH HO

O

O

HO

OH

OH

O

OH

2ESBO + 3BPA

O O

OH O

HO O

O

OH

OH

OH

1ESBO + 3BPA

HO

OH

OH

O

O

O

O

2ESBO + 2BPA HO

OH

O

OH OH

OH

O

HO

2ESBO + 1BPA O

O

O

OH

O

OH

O

OH

HO O

3ESBO + 4BPA

O

OH

OH

O

3ESBO + 3BPA



OH

Page 43 of 47

997,7

ESBO (A)

3000

1524,1

4213,1

1453,9

1296,0

1225,8

1155,9

3500

4084,0

2500

1454,0

1225,8

1309,9

3375,4

1ESBO+1BPA

3547,5

3081,0

2130,0

1892,4

2000

2867,0

1500

2400,7

1000

2ESBO+2BPA


1734,2

1436,9


983,7 1029,7 1027,7

3105,3

2997,2 885,7

927,7

(B)

0

1154,9

1043,7 1057,7

885,7

941,7


1ESBO+1BPA

2414,7

1836,4 1976,5

2116,6 2186,6 2260,5

1ESBO+1BPA

Intensity [a.u.]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2ESBO+1BPA

4000

4500

5000

m/z Figure 4. MALDI-TOF mass spectrum of sample obtained during: 3rd (A) and 12th (B) hour of conducting the epoxy fusion process of the high-molecular weight bio-epoxy resins



Page 44 of 47






Page 45 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



Value 18.5 2.8 13.1 6.8



400000 1ESBO + 1BPA

300000

Intensity [a.u.]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 46 of 47

1ESBO + 2BPA 200000


100000

2ESBO + 1BPA

3ESBO + 3BPA

2ESBO + 2BPA

3ESBO + 4BPA

0 0

1000

1500

2000

2500

3000

3500

4000

4500



Page 47 of 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47



O

O O

OH

OH

1ESBO + 1BPA

O

OH

O

OH

HO OH

OH

O

1ESBO + 2BPA

O

OH HO

O

O

HO

OH

OH

O

OH

2ESBO + 3BPA

O O

OH O

HO O

O

OH

OH

OH

1ESBO + 3BPA

HO

OH

OH

O

O

O

O

2ESBO + 2BPA HO

OH

O

OH OH

OH

O

HO

2ESBO + 1BPA O

O

O

OH

O

OH

O

OH

HO O

3ESBO + 4BPA

O

OH

OH

O

3ESBO + 3BPA



OH

Synthesis of High-Molecular Weight Biobased Epoxy Resins

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