Polyesters containing cyclic carbohydrate-based units obtained by ring opening polymerization

Premi extraordinari doctorat UPC curs 2017-2018. Àmbit d’Enginyeria IndustrialIn recent years, as a result of climate change, the interest in sustainable materials has increased dramatically. The replacement of compounds of petrochemical origin by bio-based has spread to all areas of chemistry. Nowadays there is a development of sustainable polymers based in 2,5-furanedicarboxylic acid (FDCA) as it may compete in performance with the ones based on terephthalic acid (PTA). On the other hand, the entropically driven ring opening polymerization (ED-ROP) is an attractive synthesis route whose interest has grown in this last decade because the reaction is athermal, no byproducts are generated and polymers of high molecular weight can be obtained in short reaction times. This Thesis reports the synthesis and characterization of cyclic oligomers of FDCA with different diols, such as 1,4-butanediol (c(BF)n), ethylene glycol (c(EF)n), resorcinol (c(RF)n) and isomannide (c(ImF)n) using different synthetic routes including high dilution condensation (HDC) and cyclodepolymerization (CD). The cyclic oligomers of butylene isophthalate (c(BI)n) and butylene terephthalate (c(BT)n) have also been synthesized by HDC. Finally, the cyclic oligomers of butylene succinate (c(BS)n) and ethylene succinate (c(ES)n) were obtained by enzymatic cyclization reaction (EC). The furanic cyclic oligomers were homopolymerized and copolymerized with the aforementioned cyclic oligoesters as well as with epsilon-caprolactone (e-CL). The polymerization reactions were catalyzed with tin octanoate (SnOct2), except in the case of homopolyesters and copolyesters with aliphatic units in which the Candida antarctica lipase B (CALB) was used. The molecular weights of the polymers obtained ranged between 25,000 and 80,000 g / mol. The copolymers presented a random microstructure with the exception of the caprolactone derivatives, which presented a blocky microstructure. Differential scanning calorimetry (DSC) studies revealed that PEF, PBF, PBT, PBI, PBS, PES, and their copolymers with less than 30% of aliphatic comonomer, turned out to be crystalline, on the contrary, copolymers with close compositions to 50:50 were usually amorphous. On the other hand, the PRF and the PImF were amorphous and the incorporation of their units in other copolyesters restricted the their crystallinity. In addition, the melting temperature (Tm) and the glass transition temperature (Tg) were intermediate to those of the homopolyesters, with a practically linear tendency in the second case. The crystallizability of most copolyesters was also studied, which allowed obtaining different kinetic parameters through the application of the Avrami equation. Thermogravimetric analysis (TGA) revealed that most polyesters and copolyesters were thermally stable up to 400 oC. The studies of hydrolytic and enzymatic degradability showed the high resistance to the degradation of PBF, PEF and PRF, which decreased markedly with the incorporation of aliphatic units such as BS, ES, CL or ImF in the copolyesters. This thesis summarizes the main aspects in the synthesis of cyclic oligomers of FDCA and its homopolymerization and copolymerization with different cyclic oligomers via ED-ROP. According to the results obtained, polyesters based on furanic derivatives could be considered as a viable alternative to polyesters of petrochemical origin for industrial applications.En estos últimos años, como consecuencia del cambio climático, ha aumentado extraordinariamente el interés por materiales sostenibles. El reemplazo de los compuestos de origen petroquímico por naturales se ha extendido a todos los ámbitos de la química. Se están desarrollando polímeros sostenibles basados en ácido 2.5-furandicarboxílico (FDCA) ya que pueden competir en prestaciones con los basados en el ácido tereftálico (PTA). Por otro lado, la polimerización entrópica por apertura de anillo (ED-ROP) es una vía de síntesis atractiva cuyo interés ha crecido en esta última década debido a que la reacción es atérmica, no se generan subproductos y se puede obtener polímeros de alto peso molecular en cortos tiempos de reacción. En esta Tesis se reporta la síntesis y caracterización de oligómeros cíclicos de FDCA con diferentes dioles, tales como 1,4- butanodiol (c(BF)n), etilenglicol (c(EF)n), resorcinol (c(RF)n) e isomannide (c(ImF)n) usando diferentes rutas sintéticas incluyendo la condensación con alta dilución (HDC), la ciclodepolimerización (CD). También se han sintetizado mediante HDC los oligómeros cíclicos de butilén isoftalato (c(BI)n) y butilén tereftalato (c(BT)n). Finalmente, se han obtenido los oligómeros cíclicos de butilén succinato (c(BS)n) y etilén succinato (c(ES)n) por reacción de ciclación enzimática (EC). Los oligómeros cíclicos furánicos se homopolimerizaron y copolimerizaron con los oligoesteres cíclicos mencionados anteriormente así como con la epsilon-caprolactona (e-CL). Las reacciones de polimerización fueron catalizadas con el octanoato de estaño (SnOct2), excepto en el caso de los homopoliésteres y copoliésteres con unidades alifáticas en los que se utilizó la enzima lipasa B de Cándida antárctica (CALB). Los pesos moleculares de los polímeros obtenidos oscilaron entre 25,000 y 80,000 g/mol. Los copolímeros presentaban una microestructura al azar con la excepción de los derivados de caprolactona, los cuales presentaron una microestructura en bloques. Los estudios de calorimetría diferencial de barrido (DSC) revelaron que el PEF, PBF, PBT, PBI, PBS, PES, y sus copolímeros con menos del 30% de comonómero alifático, resultaron ser cristalinos, por el contrario, los copolímeros con composiciones cercanas al 50:50 resultaron ser por lo general amorfos. Por otro lado, el PRF y el PImF eran amorfos y la incorporación de sus unidades en otros copoliésteres restringió la cristalinidad de los mismos. Además la temperatura de fusión (Tm) y la temperatura de transición vítrea (Tg) eran intermedias a las de los homopoliésteres, con una tendencia prácticamente lineal en el segundo caso. También se estudió la cristalizabilidad de la mayoría de los copoliésteres, lo cual permitió la obtención de diferentes parámetros cinéticos mediante la aplicación de la ecuación de Avrami. El análisis termogravimétrico (TGA) reveló que la mayoría de los poliésteres y copoliésteres eran térmicamente estables hasta 400 oC. Los estudios de degradabilidad hidrolítica y enzimática mostraron la alta resistencia a la degradación del PBF, PEF y PRF, la cual decrecía notablemente con la incorporación de unidades alifáticas tales como el BS, ES, CL o ImF. La presente Tesis resume los principales aspectos en la síntesis de oligómeros cíclicos de FDCA y su homopolimerización y copolimerización con diferentes oligómeros cíclicos vía ED-ROP. De acuerdo con los resultados obtenidos, los poliésteres basados en derivados furánicos podrían considerarse como una alternativa viable a los poliésteres de origen químico.Award-winningPostprint (published version

Polyesters containing cyclic carbohydrate-based units obtained by ring opening polymerization

In recent years, as a result of climate change, the interest in sustainable materials has increased dramatically. The replacement of compounds of petrochemical origin by bio-based has spread to all areas of chemistry. Nowadays there is a development of sustainable polymers based in 2,5-furanedicarboxylic acid (FDCA) as it may compete in performance with the ones based on terephthalic acid (PTA). On the other hand, the entropically driven ring opening polymerization (ED-ROP) is an attractive synthesis route whose interest has grown in this last decade because the reaction is athermal, no byproducts are generated and polymers of high molecular weight can be obtained in short reaction times. This Thesis reports the synthesis and characterization of cyclic oligomers of FDCA with different diols, such as 1,4-butanediol (c(BF)n), ethylene glycol (c(EF)n), resorcinol (c(RF)n) and isomannide (c(ImF)n) using different synthetic routes including high dilution condensation (HDC) and cyclodepolymerization (CD). The cyclic oligomers of butylene isophthalate (c(BI)n) and butylene terephthalate (c(BT)n) have also been synthesized by HDC. Finally, the cyclic oligomers of butylene succinate (c(BS)n) and ethylene succinate (c(ES)n) were obtained by enzymatic cyclization reaction (EC). The furanic cyclic oligomers were homopolymerized and copolymerized with the aforementioned cyclic oligoesters as well as with epsilon-caprolactone (e-CL). The polymerization reactions were catalyzed with tin octanoate (SnOct2), except in the case of homopolyesters and copolyesters with aliphatic units in which the Candida antarctica lipase B (CALB) was used. The molecular weights of the polymers obtained ranged between 25,000 and 80,000 g / mol. The copolymers presented a random microstructure with the exception of the caprolactone derivatives, which presented a blocky microstructure. Differential scanning calorimetry (DSC) studies revealed that PEF, PBF, PBT, PBI, PBS, PES, and their copolymers with less than 30% of aliphatic comonomer, turned out to be crystalline, on the contrary, copolymers with close compositions to 50:50 were usually amorphous. On the other hand, the PRF and the PImF were amorphous and the incorporation of their units in other copolyesters restricted the their crystallinity. In addition, the melting temperature (Tm) and the glass transition temperature (Tg) were intermediate to those of the homopolyesters, with a practically linear tendency in the second case. The crystallizability of most copolyesters was also studied, which allowed obtaining different kinetic parameters through the application of the Avrami equation. Thermogravimetric analysis (TGA) revealed that most polyesters and copolyesters were thermally stable up to 400 oC. The studies of hydrolytic and enzymatic degradability showed the high resistance to the degradation of PBF, PEF and PRF, which decreased markedly with the incorporation of aliphatic units such as BS, ES, CL or ImF in the copolyesters. This thesis summarizes the main aspects in the synthesis of cyclic oligomers of FDCA and its homopolymerization and copolymerization with different cyclic oligomers via ED-ROP. According to the results obtained, polyesters based on furanic derivatives could be considered as a viable alternative to polyesters of petrochemical origin for industrial applications.En estos últimos años, como consecuencia del cambio climático, ha aumentado extraordinariamente el interés por materiales sostenibles. El reemplazo de los compuestos de origen petroquímico por naturales se ha extendido a todos los ámbitos de la química. Se están desarrollando polímeros sostenibles basados en ácido 2.5-furandicarboxílico (FDCA) ya que pueden competir en prestaciones con los basados en el ácido tereftálico (PTA). Por otro lado, la polimerización entrópica por apertura de anillo (ED-ROP) es una vía de síntesis atractiva cuyo interés ha crecido en esta última década debido a que la reacción es atérmica, no se generan subproductos y se puede obtener polímeros de alto peso molecular en cortos tiempos de reacción. En esta Tesis se reporta la síntesis y caracterización de oligómeros cíclicos de FDCA con diferentes dioles, tales como 1,4- butanodiol (c(BF)n), etilenglicol (c(EF)n), resorcinol (c(RF)n) e isomannide (c(ImF)n) usando diferentes rutas sintéticas incluyendo la condensación con alta dilución (HDC), la ciclodepolimerización (CD). También se han sintetizado mediante HDC los oligómeros cíclicos de butilén isoftalato (c(BI)n) y butilén tereftalato (c(BT)n). Finalmente, se han obtenido los oligómeros cíclicos de butilén succinato (c(BS)n) y etilén succinato (c(ES)n) por reacción de ciclación enzimática (EC). Los oligómeros cíclicos furánicos se homopolimerizaron y copolimerizaron con los oligoesteres cíclicos mencionados anteriormente así como con la epsilon-caprolactona (e-CL). Las reacciones de polimerización fueron catalizadas con el octanoato de estaño (SnOct2), excepto en el caso de los homopoliésteres y copoliésteres con unidades alifáticas en los que se utilizó la enzima lipasa B de Cándida antárctica (CALB). Los pesos moleculares de los polímeros obtenidos oscilaron entre 25,000 y 80,000 g/mol. Los copolímeros presentaban una microestructura al azar con la excepción de los derivados de caprolactona, los cuales presentaron una microestructura en bloques. Los estudios de calorimetría diferencial de barrido (DSC) revelaron que el PEF, PBF, PBT, PBI, PBS, PES, y sus copolímeros con menos del 30% de comonómero alifático, resultaron ser cristalinos, por el contrario, los copolímeros con composiciones cercanas al 50:50 resultaron ser por lo general amorfos. Por otro lado, el PRF y el PImF eran amorfos y la incorporación de sus unidades en otros copoliésteres restringió la cristalinidad de los mismos. Además la temperatura de fusión (Tm) y la temperatura de transición vítrea (Tg) eran intermedias a las de los homopoliésteres, con una tendencia prácticamente lineal en el segundo caso. También se estudió la cristalizabilidad de la mayoría de los copoliésteres, lo cual permitió la obtención de diferentes parámetros cinéticos mediante la aplicación de la ecuación de Avrami. El análisis termogravimétrico (TGA) reveló que la mayoría de los poliésteres y copoliésteres eran térmicamente estables hasta 400 oC. Los estudios de degradabilidad hidrolítica y enzimática mostraron la alta resistencia a la degradación del PBF, PEF y PRF, la cual decrecía notablemente con la incorporación de unidades alifáticas tales como el BS, ES, CL o ImF. La presente Tesis resume los principales aspectos en la síntesis de oligómeros cíclicos de FDCA y su homopolimerización y copolimerización con diferentes oligómeros cíclicos vía ED-ROP. De acuerdo con los resultados obtenidos, los poliésteres basados en derivados furánicos podrían considerarse como una alternativa viable a los poliésteres de origen químico

Fully bio-based aromatic–aliphatic copolyesters: poly(butylene furandicarboxylate-co-succinate)s obtained by ring opening polymerization

Poly(butylene 2,5-furandicarboxylate-co-succinate) copolyesters (coPBFxSy) have been synthesized by ring opening polymerization (ROP). Cyclic butylene 2,5-furandicarboxylate and butylene succinate oligomer mixtures, to be used as monomers for ROP, were prepared by high dilution condensation and enzymatic cyclization reactions, respectively. Two different catalytic systems, tin dioctanoate and supported Candida antarctica lipase B (CALB), were used for polymerization. Thus two series of copolyesters covering the whole range of compositions were prepared and their properties comparatively examined. In both cases, random copolyesters with compositions close to those used in their respective feeds were obtained. The influence of composition on reaction kinetics with respect to time and temperature was evaluated for the two series. Chemically catalyzed ROP rendered copolyesters with Mw in the ~50 000–65 000 g mol-1 range, whereas values between 15 000 and 45 000 g mol-1 were attained when the ROP reaction was assisted by CALB. The thermal behavior of coPBFxSy obtained by ROP was similar to that reported for such copolymers prepared by melt polycondensation. They all start to decompose above 300 °C and display melting enthalpy and temperatures that decrease with copolymerization, attaining minimum values when the comonomer contents are approximate to balance. On the contrary, the glass-transition temperature increased almost linearly with the content of butylene furandicarboxylate units, covering the whole range of values between those of the two parent homopolyesters. Small deviations in thermal properties observed between the two series could be attributed to their differences in molecular weights. Hydrolytic and enzymatic degradation studies revealed that coPBFxSy became more degradable with increasing content of succinic units, whereas the homopolyester PBF remained practically unaffected when incubated under similar conditions.Peer ReviewedPostprint (author's final draft

Bio-based aromatic polyesters and copolyesters by ring opening polymerization

In this work, the synthesis of both c(BF)n and c(BT)n has been performed using the high dilution cyclization technique and these cycles have been then used for the preparation of the homopolyesters PBF and PBT, as well as of a series of poly(butylene 2,5-furandicarboxylate-co-terephthalate) (coPBFxTy) with a wide range of compositions (Fig. 1). Results are compared with those obtained from similar copolyesters prepared by melt polycondensation, which have been recently reportedPostprint (published version

A green strategy for the synthesis of poly(ethylene succinate) and its copolyesters via enzymatic ring opening polymerization

Poly(ethylene succinate) (PES) with weight-average molecular weight above 60,000 g mol-1 was efficiently obtained by enzymatic ring opening polymerization of cyclic oligo(ethylene succinate)s c(ES)n, which in turn were prepared by lipase-catalysed cyclocondensation in solution of dimethyl succinate and ethylene glycol. The methodology was demonstrated to be also applicable to the synthesis of high molecular weight PES-copolyesters containing butylene succinate, e-hydroxycaproate or L-lactate units with a random distribution.Peer ReviewedPostprint (author's final draft

Sustainable aromatic copolyesters via ring opening polymerization: Poly(butylene 2,5-furandicarboxylate-co-terephthalate)s

A series of poly(butylene 2,5-furandicarboxylate-co-terephthalate) copolyesters coPBFxTy covering the whole range of compositions has been prepared via ring opening polymerization (ROP). Cyclic oligomers of butylene 2,5-furandicarboxylate c(BF)n and butylene terephthalate c(BT)n, both mainly consisting of a mixture of dimer, trimer, and tetramer species, were synthesized by the high dilution condensation method. Random copolyesters with the targeted compositions and weight-average molecular weights within the 55¿000–80¿000 g·mol–1 range were obtained by ROP of c(BF)n/c(BT)n mixtures in periods of time much shorter than those required by melt polycondensation. The thermal properties of these copolyesters were consistent with their compositions and comparable to their isocompositional analogs obtained by polycondensation. A comparative kinetics study of the isothermal crystallization of the homopolyesters and copolyesters differing in composition revealed that the presence of the 2,5-furandicarboxylate units decreased the crystallization rate of PBT. Nevertheless, coPBFxTy copolyesters with moderate contents in BF units were still able to crystallized rapidly from the meltPeer ReviewedPostprint (published version

Efectos de la alteración endocrina durante la gestación: una revisión sistemática

Los alteradores endocrinos son contaminantes ambientales, naturales y sintéticos, ubicuos, que pueden mimetizar, bloquear o alterar funciones hormonales. La exposición ambiental a estos contaminantes es prácticamente imposible de evitar debido a que están presentes en el aire, en el agua, en los suelos, en los alimentos, y en muchos de los materiales con los que estamos en contacto diariamente, como los plásticos. La gestación supone una etapa de vulnerabilidad para el feto porque su organismo está en proceso de desarrollo y cualquier alteración puede afectar su salud a corto o largo plazo. Hay cierta evidencia de que estas sustancias alteran procesos de crecimiento y diferenciación de tejidos, producen malformaciones y afectan la duración del embarazo. Hasta el momento se conoce algo de sus efectos en la etiología de la criptorquidia, hipospadias y micropene, abortos espontáneos, partos prematuros y el bajo peso al nacimiento, efectos que serán revisados en este documento que quiere aportar una actualización del conocimiento, concentrándose en la epidemiología ambiental y la literatura relacionada. La dificultad para estudiar este tema por la cantidad de factores que intervienen hace que los resultados existentes no sean concluyentes o incluso contradictorios, por lo que es necesario que se siga investigando Abstract.Endocrine disruptors are ubiquitous natural and synthetic environmental pollutants that can mimic, block or disturb normal hormonal function. Environmental exposure to these pollutants is almost impossible to prevent due to their presence in the air,water, soil, food and in many other materials with which we come in contact daily, such as plastics. Foetuses are vulnerable during pregnancy because their organism is in a developmental stage, and any disruption may affect their health in the short and/or long term. There is some evidence that these substances disrupt tissue differentiation and growth processes, cause birth defects and affect the length of pregnancy. In this review we will focus on environmental epidemiology and related literature in order to update current knowledge based on the actual evidence of the effects of these substances on the aetiology of preterm delivery, miscarriages, low birth weight, malformations, cryptorchidism, hypospadias and micropenis. The difficulty in studying this topic is due to the high number of involved factors, which makes the available results inconclusive or even contradictory. Consequently,further research is necessary

Poly(butylene 2,5-furan dicarboxylate-co-butylene succinate) via ring opening polymerization

In this communication we wish to report on the synthesis of PBFxSy copolyesters by ring opening polymerization (ROP) using either organometallic catalysts or enzymes. The ROP of macrocyclic oligomers (MCOs) has been demonstrated to offer significant advantages over the traditional polycondensation method. The synthesis of MCOs of butylene succinate c(BS)n is known from long whereas MCOs of butylene 2,5-furandicarboxylate (c(BF)n) have not been reported until very recently. In this work, the synthesis of c(BF)n and c(BS)n has been performed using high dilution condensation (HDC) and enzymatic cyclization, respectively. Mixtures of dimer to tetramer and dimer to nonamer were obtained for c(BF)n and c(BS)n respectively.Postprint (published version

Isomannide-containing poly(butylene 2,5-furandicarboxylate) copolyesters via ring opening polymerization

Cyclic oligomers of isomannide 2,5-furandicarboxylate were synthesized using the high dilution condensation method. A mixture of dimer, trimer, and tetramer species largely enriched in dimer was obtained. These cyclic oligomers were made to react with oligo(butylene 2,5-furandicarboxylate) in bulk at 220 °C by ring opening polymerization using Sn(Oct)2 as a catalyst. A series of random poly(butylene 2,5-furandicarboxylate) copolyesters containing isomannide in a range of 5–50 mol % and with weight-average molecular weights between 30,000 and 50,000 g·mol–1 were prepared. These copolyesters started to decompose above 300 °C, and only those containing less than 10 mol % of isomannide showed signs of crystallinity. They displayed glass-transition temperatures in the 40–100 °C range with values increasing steadily with the content in isomannide. At difference with poly(butylene 2,5-furandicarboxylate) homopolyester that is reluctant to undergo hydrolysis, the isomannide-containing copolyesters were noticeably degraded by water, much more rapidly when exposed to lipases.Peer ReviewedPostprint (author's final draft

Detection of Breast Cancer using Convolutional Neural Networks with Learning Transfer Mechanisms

Breast cancer is the leading cause of mortality in women worldwide. One of the biggest challenges for physicians and technological support systems is early detection, because it is easier to treat and establish curative treatments. Currently, assistive technology systems use images to detect patterns of behavior with respect to patients who have been found to have some type of cancer. This work aims to identify and classify breast cancer using deep learning models and convolutional neural networks (CNN) with transfer learning. For the breast cancer detection process, 7803 real images with benign and malignant labels were used, which were provided by BreaKHis on the Kaggle platform. The convolutional basis (parameters) of pre-trained models VGG16, VGG19, Resnet-50 and Inception-V3 were used. The TensorFlow framework, keras and Python libraries were also used to retrain the parameters of the models proposed for this study. Metrics such as accuracy, error ratio, precision, recall and f1-score were used to evaluate the models. The results show that the models based on VGG16, VGG19 ResNet-50 and Inception-V3 obtain an accuracy of 88%, 86%, 97% and 96% respectively, recall of 84%, 82%, 96% and 96% respectively, in addition to f1-score of 86%, 83%, 96% and 95% respectively. It is concluded that the model that shows the best results is Resnet-50, obtaining high results in all the metrics considered, although it should be noted that the Inception-V3 model achieves very similar results in relation to Resnet-50, in all the metrics. In addition, these two models exceed the 95% threshold of correct results