Polyester Precursors Research Articles

Itaconic Acid as a Comonomer in Betulin-Based Thermosets via Sequential and Bulk Preparation.

The inherent chemical functionalities of biobased monomers enable the production of renewably sourced polymers that further advance sustainable manufacturing. Itaconic acid (IA) is a nontoxic, commercially produced biobased monomer that can undergo both UV and thermal curing. Betulin is a biocompatible, structurally complex diol derived from birch tree bark that has been recently studied for materials with diverse applications. Here, betulin, IA, and biobased linear diacids, 1,12-dodecanedioic acid (C12) and 1,18-octadecanedioic acid (C18), were used to prepare thermosets using sequential and bulk curing methods. Thermoplastic polyester precursors were synthesized and formulated into polyester-methacrylate (PM) resins to produce sequential UV-curable thermosets. Bulk-cured polyester thermosets were prepared using a one-pot, solventless melt polycondensation using glycerol as a cross-linker. The structure-property relationships of the thermoplastic polyester precursors, sequentially prepared PM thermosets, and bulk-cured polyester thermosets were evaluated with varying IA content. Both types of thermosets exhibited higher storage moduli, Tgs, and thermal stabilities with greater IA comonomer content. These results demonstrate the viability of using IA as a comonomer to produce betulin-based thermosets each with tunable properties, expanding the scope of their applications and use in polymeric materials.

Module-Assembled Elastomer Showing Large Strain Stiffening Capability and High Stretchability.

Elastomers are indispensable materials due to their flexible, stretchable, and elastic nature. However, the polymer network structure constituting an elastomer is generally inhomogeneous, limiting the performance of the material. Here, a highly stretchable elastomer with unprecedented strain-stiffening capability is developed based on a highly homogeneous network structure enabled by a module assembly strategy. The elastomer is synthesized by efficient end-linking of a star-shaped aliphatic polyester precursor with a narrow molecular-weight distribution. The resulting product shows high strength (≈26MPa) and remarkable stretchability (stretch ratio at break ≈1900%), as well as good fatigue resistance and notch insensitivity. Moreover, it shows extraordinary strain-stiffening capability (>2000-fold increase in the apparent stiffness) that exceeds the performance of any existing soft material. These unique properties are due to strain-induced ordering of the polymer chains in a uniformly stretched network, as revealed by in situ X-ray scattering analyses. The utility of this great strain-stiffening capability is demonstrated by realizing a simple variable stiffness actuator for soft robotics.

Biological funneling of phenolics from transgenic plants engineered to express the bacterial 3-dehydroshikimate dehydratase (qsuB) gene

The economic and environmental sustainability of lignocellulosic biomass biorefineries is predicated on generating biofuels and bioproducts from cell-wall polysaccharide and lignin polymers. Historical efforts in plant genetic engineering have focused on the development of strategies that facilitate biomass deconstruction, with more recently efforts including the synthesis of high-value chemicals in planta. One such genetic modification is the expression of the bacterial quinate and shikimate utilization B (qsuB) gene that increases the accumulation of protocatechuic acid in lignocellulosic biomass. Herein, we evaluated the effectiveness of an alkaline pretreatment process to extract phenolics directly from wild-type and QsuB-transgenic lines of Arabidopsis, poplar, and sorghum, and then upgrade them to the polyester precursor 2-pyrone-4,6-dicarboxylic acid (PDC) with an engineered strain of Novosphingobium aromaticivorans. Protocatechuic acid extracted from all QsuB transgenic lines was found to be mostly in the glycosylated form. Glycosylated protocatechuic acid and other plant-derived phenolics were effectively metabolized by N. aromaticivorans, and PDC production was greatest using extracts from an Arabidopsis QsuB transgenic line (∼5% w/w), followed by QsuB sorghum (∼1.1% w/w), and QsuB poplar (∼0.4% w/w) lines. The comparison of PDC production from wild-type and QsuB transgenic lines of Arabidopsis, poplar, and sorghum demonstrates the utility of a mild alkaline pretreatment to liberate phenolics from plant biomass that are either naturally present or that accumulate as a consequence of genetic engineering strategies. All QsuB transgenic lines outperformed their wild-type counterparts with respect to observed PDC yields. In addition, microbial funneling to PDC was effective even when most of the protocatechuic acid extracted was in glycosylated form, clearly demonstrating that this bacterium can metabolize these aromatic conjugates. These findings illustrate the benefits of combining plant and microbial engineering for bioproduct formation from phenolics in lignocellulosic biorefineries.

Fragaria × ananassa cv. Senga Sengana Leaf: An Agricultural Waste with Antiglycation Potential and High Content of Ellagitannins, Flavonols, and 2-Pyrone-4,6-dicarboxylic Acid.

Strawberry leaves are considered a valuable waste material; so far, mainly due to their antioxidant properties. Since the annual production of this crop is high, our study aimed to thoroughly examine the chemical composition and antidiabetes-related bioactivity of Fragaria × ananassa leaf of its popular and productive cultivar Senga Sengana. Leaves from three different seasons, collected after fruiting, were extensively analyzed (UHPLC-qTOF-MS/MS, HPLC-DAD). Some individual components were isolated and quantified, including specific flavonol diglycosides (e.g., 3-O-[β-xylosyl(1‴→2″)]-β-glucuronosides). The separated quercetin glycosides were tested in an antiglycation assay, and their methylglyoxal uptake capacity was measured. In addition, the biodegradable polyester precursor 2-pyrone-4,6-dicarboxylic acid (PDC) was confirmed at relatively high levels, providing further opportunity for strawberry leaf utilization. We want to bring to the attention of the food, pharmaceutical, and cosmetic industries the Senga Sengana strawberry leaf as a new botanical raw material. It is rich in PDC, ellagitannins, and flavonols—potent glycation inhibitors.

Ring-Opening Polymerization of CO2-Based Disubstituted δ-Valerolactone toward Sustainable Functional Polyesters.

3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL) is a disubstituent δ-lactone derived from CO2 and 1,3-butadiene. In this contribution, we report the ring-opening polymerization (ROP) of EVL with β-butyrolactone (BBL) as the comonomer catalyzed by scandium triflate [Sc(OTf)3]. The obtained polyester bearing active unsaturated bonds has the weight-average molecular weight (Mw) of 4.1 kg/mol, in which the EVL content is 38 mol % in accordance with the initial ratio of 40 mol %. The copolymers are characterized in detail and the cationic ROP mechanism has been confirmed by kinetic study, chain end analysis and density functional theory (DFT) calculation. The modification of the unsaturated bonds in EVL repeating units via the thio-ene click reaction with mercapto-ended polysarcosine polysarcosine yields the amphiphilic grafting polymers. It is a CO2 fixation approach toward the functional poly(EVL-r-BBL) that is promising as a degradable polyester precursor for adhesive or surface-coating materials.

In-planta production of the biodegradable polyester precursor 2-pyrone-4,6-dicarboxylic acid (PDC): Stacking reduced biomass recalcitrance with value-added co-product

2-Pyrone-4,6-dicarboxylic acid (PDC), a chemically stable intermediate that naturally occurs during microbial degradation of lignin by bacteria, represents a promising building block for diverse biomaterials and polyesters such as biodegradable plastics. The lack of a chemical synthesis method has hindered large-scale utilization of PDC and metabolic engineering approaches for its biosynthesis have recently emerged. In this study, we demonstrate a strategy for the production of PDC via manipulation of the shikimate pathway using plants as green factories. In tobacco leaves, we first showed that transient expression of bacterial feedback-resistant 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase (AroG) and 3-dehydroshikimate dehydratase (QsuB) produced high titers of protocatechuate (PCA), which was in turn efficiently converted into PDC upon co-expression of PCA 4,5-dioxygenase (PmdAB) and 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase (PmdC) derived from Comamonas testosteroni. We validated that stable expression of AroG in Arabidopsis in a genetic background containing the QsuB gene enhanced PCA content in plant biomass, presumably via an increase of the carbon flux through the shikimate pathway. Further, introducing AroG and the PDC biosynthetic genes (PmdA, PmdB, and PmdC) into the Arabidopsis QsuB background, or introducing the five genes (AroG, QsuB, PmdA, PmdB, and PmdC) stacked on a single construct into wild-type plants, resulted in PDC titers of ~1% and ~3% dry weight in plant biomass, respectively. Consistent with previous studies of plants expressing QsuB, all PDC producing lines showed strong reduction in lignin content in stems. This low lignin trait was accompanied with improvements of biomass saccharification efficiency due to reduced cell wall recalcitrance to enzymatic degradation. Importantly, most transgenic lines showed no reduction in biomass yields. Therefore, we conclude that engineering plants with the proposed de-novo PDC pathway provides an avenue to enrich biomass with a value-added co-product while simultaneously improving biomass quality for the supply of fermentable sugars. Implementing this strategy into bioenergy crops has the potential to support existing microbial fermentation approaches that exploit lignocellulosic biomass feedstocks for PDC production.

Oxidative esterification of aliphatic α,ω-diols, an alternative route to polyester precursors for the synthesis of polyurethanes

Aliphatic α,ω-diols are converted into polyester polyols in water in the presence ofin situgenerated BrOH. The extent of the reaction is controlled by the BrOH to hydroxymethyl group molar ratio.

Dissecting the Mechanism of (R)-3-Hydroxybutyrate Dehydrogenase by Kinetic Isotope Effects, Protein Crystallography, and Computational Chemistry.

The enzyme (R)-3-hydroxybutyrate dehydrogenase (HBDH) catalyzes the enantioselective reduction of 3-oxocarboxylates to (R)-3-hydroxycarboxylates, the monomeric precursors of biodegradable polyesters. Despite its application in asymmetric reduction, which prompted several engineering attempts of this enzyme, the order of chemical events in the active site, their contributions to limit the reaction rate, and interactions between the enzyme and non-native 3-oxocarboxylates have not been explored. Here, a combination of kinetic isotope effects, protein crystallography, and quantum mechanics/molecular mechanics (QM/MM) calculations were employed to dissect the HBDH mechanism. Initial velocity patterns and primary deuterium kinetic isotope effects establish a steady-state ordered kinetic mechanism for acetoacetate reduction by a psychrophilic and a mesophilic HBDH, where hydride transfer is not rate limiting. Primary deuterium kinetic isotope effects on the reduction of 3-oxovalerate indicate that hydride transfer becomes more rate limiting with this non-native substrate. Solvent and multiple deuterium kinetic isotope effects suggest hydride and proton transfers occur in the same transition state. Crystal structures were solved for both enzymes complexed to NAD+:acetoacetate and NAD+:3-oxovalerate, illustrating the structural basis for the stereochemistry of the 3-hydroxycarboxylate products. QM/MM calculations using the crystal structures as a starting point predicted a higher activation energy for 3-oxovalerate reduction catalyzed by the mesophilic HBDH, in agreement with the higher reaction rate observed experimentally for the psychrophilic orthologue. Both transition states show concerted, albeit not synchronous, proton and hydride transfers to 3-oxovalerate. Setting the MM partial charges to zero results in identical reaction activation energies with both orthologues, suggesting the difference in activation energy between the reactions catalyzed by cold- and warm-adapted HBDHs arises from differential electrostatic stabilization of the transition state. Mutagenesis and phylogenetic analysis reveal the catalytic importance of His150 and Asn145 in the respective orthologues.

Pycnoporus cinnabarinus glyoxal oxidases display differential catalytic efficiencies on 5-hydroxymethylfurfural and its oxidized derivatives

Background5-Hydroxymethylfurfural (HMF), a major residual component of a lignocellulosic bio-refinery process, can be transformed into fundamental building blocks for green chemistry via oxidation. While chemical methods are well established, interest is also being directed into the enzymatic oxidation of HMF into the bio-plastic precursor 2,5-furandicarboxylic acid (FDCA).ResultsWe demonstrate that three glyoxal oxidases (PciGLOX) isoenzymes from the Basidiomycete fungus Pycnoporus cinnabarinus were able to oxidize HMF, with PciGLOX2 and PciGLOX3 being the most efficient. The major reaction product obtained with the three isoenzymes was 5-hydroxymethyl-2-furancarboxylic (HMFCA), a precursor in polyesters and pharmaceuticals production, and very little subsequent conversion of this compound was observed. However, small concentrations of FDCA, a substitute for terephthalic acid in the production of polyesters, were also obtained. The oxidation of HMF was significantly boosted in the presence of catalase for PciGLOX2, leading to 70% HMFCA yield. The highest conversion percentages were observed on 2,5-furandicarboxaldehyde (DFF), a minor product from the reaction of PciGLOX on HMF. To bypass HMFCA accumulation and exploit the efficiency of PciGLOX in oxidizing DFF and 5-formyl-2-furan carboxylic acid (FFCA) towards FDCA production, HMF was oxidized in a cascade reaction with an aryl alcohol oxidase (UmaAAO). After 2 h of reaction, UmaAAO completely oxidized HMF to DFF and further to FFCA, with FDCA only being detected when PciGLOX3 was added to the reaction. The maximum yield of 16% FDCA was obtained 24 h after the addition of PciGLOX3 in the presence of catalase.ConclusionsAt least two conversion pathways for HMF oxidation can be considered for PciGLOX; however, the highest selectivity was seen towards the production of the valuable polyester precursor HMFCA. The three isoenzymes showed differences in their catalytic efficiencies and substrate specificities when reacted with HMF derivatives.

High performing immobilized Baeyer-Villiger monooxygenase and glucose dehydrogenase for the synthesis of ε-caprolactone derivative

The industrial application of Baeyer-Villiger monooxygenases (BVMOs) is typically hindered by stability and cofactor regeneration considerations. The stability of biocatalysts can be improved by immobilization. The goal of this study was to evaluate the (co)-immobilization of a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) with a glucose dehydrogenase (GDH) from Thermoplasma acidophilum for NADPH cofactor regeneration.Both enzymes were immobilized on an amino-functionalized agarose-based support (MANA-agarose). They were applied to the oxidation of 3,3,5-trimethylcyclohexanone for the synthesis of ε-caprolactone derivatives which are precursors of polyesters. The performances of the immobilized biocatalysts were evaluated in reutilization reactions with as many as 15 cycles and compared to the corresponding soluble enzymes. Co-immobilization proved to provide the most efficient biocatalyst with an average conversion of 83% over 15 reutilization cycles leading to a 50-fold increase of the biocatalyst yield compared to the use of soluble enzymes which were applied in a fed-batch strategy.TmCHMO was immobilized for the first time in this work, with very good retention of the activity throughout reutilization cycles. This immobilized biocatalyst contributes to the application of BVMOs in up-scaled biooxidation processes.

New AB type monomers from lignocellulosic biomass

Abstract A series of renewable novel bicyclic AB type polyester precursors have been prepared in good overall yield from lignocellulosic biomass. These advancements take full advantage of the differing oxidation states of functional groups in 5-(hydroxymethyl)furfural by chemoselective preparation of furanic hydroxy esters and applying benzyne-Diels–Alder cycloaddition/aromatization strategies.

Development of a promising microbial platform for the production of dicarboxylic acids from biorenewable resources

BackgroundAs a sustainable industrial process, the production of dicarboxylic acids (DCAs), used as precursors of polyamides, polyesters, perfumes, plasticizers, lubricants, and adhesives, from vegetable oil has continuously garnered interest. Although the yeast Candida tropicalis has been used as a host for DCA production, additional strains are continually investigated to meet productivity thresholds and industrial needs. In this regard, the yeast Wickerhamiella sorbophila, a potential candidate strain, has been screened. However, the lack of genetic and physiological information for this uncommon strain is an obstacle that merits further research. To overcome this limitation, we attempted to develop a method to facilitate genetic recombination in this strain and produce high amounts of DCAs from methyl laurate using engineered W. sorbophila.ResultsIn the current study, we first developed efficient genetic engineering tools for the industrial application of W. sorbophila. To increase homologous recombination (HR) efficiency during transformation, the cell cycle of the yeast was synchronized to the S/G2 phase using hydroxyurea. The HR efficiency at POX1 and POX2 loci increased from 56.3% and 41.7%, respectively, to 97.9% in both cases. The original HR efficiency at URA3 and ADE2 loci was nearly 0% during the early stationary and logarithmic phases of growth, and increased to 4.8% and 25.6%, respectively. We used the developed tools to construct W. sorbophila UHP4, in which β-oxidation was completely blocked. The strain produced 92.5 g/l of dodecanedioic acid (DDDA) from methyl laurate over 126 h in 5-l fed-batch fermentation, with a productivity of 0.83 g/l/h.ConclusionsWickerhamiella sorbophila UHP4 produced more DDDA methyl laurate than C. tropicalis. Hence, we demonstrated that W. sorbophila is a powerful microbial platform for vegetable oil-based DCA production. In addition, by using the developed genetic engineering tools, this emerging yeast could be used for the production of a variety of fatty acid derivatives, such as fatty alcohols, fatty aldehydes, and ω-hydroxy fatty acids.

Application of a thermostable Baeyer-Villiger monooxygenase for the synthesis of branched polyester precursors.

BACKGROUNDIt is widely accepted that the poor thermostability of Baeyer–Villiger monooxygenases limits their use as biocatalysts for applied biocatalysis in industrial applications. The goal of this study was to investigate the biocatalytic oxidation of 3,3,5‐trimethylcyclohexanone using a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) for the synthesis of branched ϵ‐caprolactone derivatives as building blocks for tuned polymeric backbones. In this multi‐enzymatic reaction, the thermostable cyclohexanone monooxygenase was fused to a phosphite dehydrogenase (PTDH) in order to ensure co‐factor regeneration.RESULTSUsing reaction engineering, the reaction rate and product formation of the regio‐isomeric branched lactones were improved and the use of co‐solvents and the initial substrate load were investigated. Substrate inhibition and poor product solubility were overcome using continuous substrate feeding regimes, as well as a biphasic reaction system with toluene as water‐immiscible organic solvent. A maximum volumetric productivity, or space–time‐yield, of 1.20 g L‐1 h‐1 was achieved with continuous feeding of substrate using methanol as co‐solvent, while a maximum product concentration of 11.6 g L‐1 was achieved with toluene acting as a second phase and substrate reservoir.CONCLUSIONThese improvements in key process metrics therefore demonstrate progress towards the up‐scaled Baeyer–Villiger monooxygenase‐biocatalyzed synthesis of the target building blocks for polymer application. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Synthesis of well-defined cyclic polyesters via self-accelerating click reaction

A metal-free and efficient homodifunctional bimolecular ring-closure method was developed specifically for the formation of well-defined cyclic polyesters based on the combination of ring opening polymerization (ROP) and self-accelerating double strain-promoted azide-alkyne cycloaddition (DSPAAC) reaction. In this method, ROP and the following end group modification were used to prepare the azide-terminated liner polyester precursors. The self-accelerating DSPAAC click reaction was then used to prepare the corresponding cyclic polyesters by ring-closing the linear polyester precursors with the small linkers of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA). The distinct advantage of this novel homodifunctional bimolecular ring-closure method lied in the fact that the pure cyclic polyesters could be efficiently prepared by using excess molar amounts of DBA small linkers to ring-close the linear polyester precursors. This was resulted from the self-accelerating property of the DSPAAC ring-closing reaction.

ExxonMobil will buy aromatics producer

ExxonMobil has inked an agreement to purchase Jurong Aromatics, which operates one of the world’s largest aromatics plants in Singapore. Jurong declared bankruptcy in 2015. Earlier this spring, South Korea’s Lotte Chemical dropped out of bidding for the firm. ExxonMobil operates two ethylene crackers and a refinery nearby. The acquisition will almost double its aromatics capacity to 3.5 million metric tons per year, half of which will be the polyester precursor p-xylene.

Influence of Polyester Chain Type in the Morphology of Silica-Carbon Composites Obtained by the Polymeric Precursor Method

Particulate composite materials containing metallic phase in ceramic matrices may be obtained by direct routes with the advantage of avoiding the partial collapse of the composite structure when a subsequent step for metal insertion is carried out. The non-metallic silica-carbon matrix combines high values of pore volume and surface area with chemical refractivity and may be applied as molecular sieves, adsorbents, filters and catalyst support. The Polymeric Precursor Method is a versatile method to obtain this composite type as the metal precursor can be reduced to metallic phase by pyrolysis of organic matter. In this work, it was used three different diol chain sizes obtaining silica-carbon composites through the pyrolysis of polyester precursor at 600°C for 3 hours in closed tubular oven. It was observed a direct dependence between the amorphous carbon phase amount and the polyester chain size. All of the composite samples presented dual distribution for mesopore size, situated at 3.8 and 11 nm in diameter. However, the pore volume and surface area significantly lowers for larger polyester chain sizes.

Morphological Characterization of Nickel-Silica Nanocomposite in Residual Carbon Obtained by Direct Polymeric Route

Nickel-silica nanocomposites can be obtained by direct chemical route, such as the Polymeric Precursor Method. That methodology type permits to obtain material powders with significant specific area and porosity suitable for reactive gases or fluids permeation, which are required characteristics for application in heterogeneous catalysis process. The composite material obtained from pyrolysis of polymeric precursor has its porosity strongly dependent from precursor constitution, which affects the decomposition kinetic. In this study, it was obtained a polyester precursor based on triethylene glycol, which has been submitted at pyrolysis at 600 oC for several times in nitrogen atmosphere. The nickel-silica nanocomposite obtained through that methodology presents a residual amorphous carbon phase playing an important rule on the mechanism of pore formation. Nickel nanoparticles nucleate with sizes close to 10 nm in diameter and are highly dispersed in a hybrid amorphous carbon-silica matrix. The composite pore volume, calculated through the JBH method, presents a continuous increasing as a function of pyrolysis time, reaching more than 0.15 cc/g after 7 hours from initial decomposition process.

Abstract P6-03-01: Low dose exposure of non-malignant breast epithelial cells to the polyester and PET precursor, terephthalic acid, triggers broad-based dysfunctional changes

Abstract BACKGROUND: Terephthalic acid (TPA) is the raw material for the production of polyester fiber and polyethylene terephthalate (PET) or #1 plastic. With steadily increasing levels of TPA in our environment, concerns for public health are foreseeable. We report the role of low dose TPA exposure in the induction of well-accepted endpoints of cancer progression within non-cancerous breast cells. METHODS: In our previous work with bisphenol-A (BPA) and methylparaben (MP), we employed human, benign, high-risk donor breast epithelial cells (HRBECs) to study functional response to chemical exposure. To measure the effects of TPA, 3 independent spontaneously immortalized ER-positive HRBEC lines were treated with concentrations ranging from 100pM to 100μM for 7 days. Changes in the levels of key signaling proteins encoded by genes associated with estrogenic stimulation, cell cycle, DNA replication, DNA repair, and apoptosis, were analyzed by Western blots. Fluorescence-activated cell sorting (FACS) was used to quantitate alterations in cell proliferation and programmed cell death. TPA-induced DNA double strand breaks were visualized as nuclear foci of activated gH2AX, and p53 by immunofluorescence microscopy. RESULTS: TPA exposure was estrogenic in HRBECs as evident by ERα activation. Similar to our findings with BPA and MP, prior exposure to TPA at 1 or more concentrations in the low dose range enabled programmed cell death evasion in 3/3 immortalized HRBEC lines (p<0.01), further confirmed in finite-life HRBECs (p<0.001) from 3/3 independent donors. Otherwise, effects of TPA were distinct from those induced by BPA and MP. Instead of an increase in the S-phase fraction of the cell cycle, TPA treatment led to a G1-arrest. These G1-arrested cells accumulated the DNA repair proteins – DNA-PK, ATM (pSer1981), RAD50, MRE11, p53 (pSer15) and H2AX (pSer139), indicating the occurrence of DNA damage. TPA removal released HRBECs from G1-arrest and restored proliferation. However, due to the propensity for apoptosis evasion conferred by TPA, unrepaired cells displaying DNA repair signals persisted even in its absence. Taken together, these findings demonstrate perpetuation of cells with evidence of DNA damage from prior TPA exposure, and suggest a scenario whereby potential DNA aberrations incurred from exposure to this and other DNA damaging agents might be transmitted to the cell progeny. CONCLUSION: Supporting the novel observation of mTOR activation in HRBECs by BPA in our previous work, TPA-induced pathway perturbations demonstrate that the common practice of screening for potential breast carcinogens simply based on increased cell proliferation, presumably stimulated by the mitogenic activity of estrogen mimics, is an oversimplification of possible sources of risk to target cells within the breast. Using such limited tests, TPA would be deemed inactive – ostensibly a false negative result. Effects of environmental chemicals must therefore be evaluated by multiple endpoints in independent biological programs within responsive human cell types. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-03-01.

Reconfigurable Biodegradable Shape-Memory Elastomers via Diels–Alder Coupling

Synthetic biodegradable elastomers are a class of polymers that have demonstrated far-reaching utility as biomaterials for use in many medical applications. Biodegradable elastomers can be broadly classified into networks prepared by either step-growth or chain-growth polymerization. Each processing strategy affords distinct advantages in terms of capabilities and resulting properties of the network. This work describes the synthesis, processing, and characterization of cross-linked polyester networks based on Diels-Alder coupling reactions. Hyperbranched furan-modified polyester precursors based on poly(glycerol-co-sebacate) are coupled with bifunctional maleimide cross-linking agents. The chemical and thermomechanical properties of the elastomers are characterized at various stages of network formation. Experimental observations of gel formation are compared to theoretical predictions derived from Flory-Stockmayer relationships. This cross-linking strategy confers unique advantages in processing and properties including the ability to fabricate biodegradable reconfigurable covalent networks without additional catalysts or reaction byproducts. Reconfigurable biodegradable networks using Diels-Alder cycloaddition reactions permit the fabrication of shape-memory polymers with complex permanent geometries. Biodegradable elastomers based on polyester networks with molecular reconfigurability achieve vastly expanded properties and processing capabilities for potential applications in medicine and beyond.

Polymerisable di- and triesters from Tall Oil Fatty Acids and related compounds

Tall Oil Fatty Acids, a low value side product from the paper industry containing mainly oleic and linoleic acids, are used for producing the polyester precursor, dimethyl 1,19-nonadecanedioate by methoxycarbonylation in the presence of [Pd2(dba)3], 1,2-bis(ditertiarybutylphosphinomethyl)benzene and methanesulfonic acid in methanol. The methoxycarbonylation of methyl linoleate has been used to identify other products formed and approaches to their minimisation have been developed. It has also been used for the production of trimethyl heptadecanetricarboxylates. Finally, conjugated unsaturated esters of different chain length (up to 16 C atoms), some of them available from plant oils, are subjected to methoxycarbonylation to give α,ω-diesters.