Phase behavior and crystallization in blends of a low molecular weight polyethylene-block-poly(ethylene oxide) diblock copolymer and poly(hydroxyether of bisphenol A)

The phase behavior, morphology and crystallization in blends of a low-molecular-weight (Mn = 1400) double-crystalline polyethylene-block-poly(ethylene oxide) (PE-PEO) diblock copolymer with poly(hydroxyether of bisphenol A) (PH) were investigated by differential scanning calorimetry, transmission electron microscopy and small-angle X-ray scattering. The symmetric PE-PEO diblock copolymer consists of a PH-miscible PEO block and a PH-immiscible PE block. However, PH only exhibits partial miscibility with the PEO block of the copolymer in the PH/PE-PEO blends; both macrophase and microphase separations took place. There existed two macrophases in the PH/PE-PEO blends, i.e., a PH-rich phase and a PE-PEO copolymer-rich phase. The PE block of the copolymer in the blends exhibited fractionated crystallization behavior by homogeneous nucleation. There appeared three crystallization exotherms related to the crystallization of the PE block within three different microenvironments in the PH/PE-PEO blends.

Selective hydrogen bonding and hierarchical nanostructures in poly(hydroxyether of bisphenol A)/poly(ε-caprolactone)-block-poly(2-vinyl pyridine) blends

The phase behavior, hydrogen bonding interactions and morphology of poly(hydroxyether of bisphenol A) (phenoxy) and poly(var epsilon-caprolactone)-block-poly(2-vinyl pyridine) (PCL-b-P2VP) were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, optical microscopy and atomic force microscopy (AFM). In this A-b-B/C type block copolymer/homopolymer system, both P2VP and PCL blocks have favorable intermolecular interaction towards phenoxy via hydrogen bonding. However, the hydrogen bonding between P2VP and phenoxy is significantly stronger than that between PCL and phenoxy. Selective hydrogen bonding between phenoxy/P2VP pair at lower phenoxy contents and co-existence of two competitive hydrogen bonding interactions between phenoxy/P2VP and phenoxy/PCL pairs at higher phenoxy contents were observed in the blends. This leads to the formation of a variety of composition dependent nanostructures including wormlike, hierarchical and core–shell morphologies. The blends became homogeneous at 95 wt% phenoxy where both blocks of the PCL-b-P2VP were miscible with phenoxy due to hydrogen bonding. In the end, a model was proposed to explain the microphase morphology of blends based on the experimental results obtained. The swelling of the PCL-b-P2VP block copolymer by phenoxy due to selective hydrogen bonding causes formation of different microphases

Competitive hydrogen bonding and self-assembly in Poly(2-vinyl pyridine)-block-Poly(methyl methacrylate)/ Poly(hydroxyether of bisphenol A) blends

Blends of poly(2-vinyl pyridine)-block-poly(methyl methacrylate) (P2VP-b-PMMA) and poly(hydroxyether of bisphenol A) (phenoxy) were prepared by solvent casting from chloroform solution. The specific interactions, phase behavior and nanostructure morphologies of these blends were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In this block copolymer/homopolymer blend system, it is established that competitive hydrogen bonding exists as both blocks of the P2VP-b-PMMA are capable of forming intermolecular hydrogen bonds with phenoxy. It was observed that the interaction between phenoxy and P2VP is stronger than that between phenoxy and PMMA. This imbalance in the intermolecular interactions and the repulsions between the two blocks of the diblock copolymer lead to a variety of phase morphologies. At low phenoxy concentration, spherical micelles are observed. As the concentration increases, PMMA begins to interact with phenoxy, leading to the changes of morphology from spherical to wormlike micelles and finally forms a homogenous system. A model is proposed to describe the self-assembled nanostructures of the P2VP-b-PMMA/phenoxy blends, and the competitive hydrogen bonding is responsible for the morphological changes.

Toughening of a carbon-fibre composite using electrospun poly(Hydroxyether of Bisphenol A) nanofibrous membranes through inverse phase separation and inter-domain etherification

The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer (~20 microns) of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored in this work. Nanofibres, free of defect and averaging several hundred nanometres, were produced by electrospinning directly onto a pre-impregnated carbon fibre material (Toray G83C) at various concentrations between 0.5 wt % and 2 wt %. During curing at 150 °C, phenoxy diffuses through the epoxy resin to form a semi interpenetrating network with an inverse phase type of morphology where the epoxy became the co-continuous phase with a nodular morphology. This type of morphology improved the fracture toughness in mode I (opening failure) and mode II (in-plane shear failure) by up to 150% and 30%, respectively. Interlaminar shear stress test results showed that the interleaving did not negatively affect the effective in-plane strength of the composites. Furthermore, there was some evidence from DMTA and FT-IR analysis to suggest that inter-domain etherification between the residual epoxide groups with the pendant hydroxyl groups of the phenoxy occurred, also leading to an increase in glass transition temperature (~7.5 °C).

Estrogen-related receptor γ is an in vivo receptor of bisphenol A

Bisphenol A (BPA) is an endocrine disruptor that displays estrogenic activity. Several reports suggest that BPA may have estrogen receptor-independent effects. In zebrafish, 50 μM BPA exposure induces otic vesicle abnormalities, including otolith aggregation. The purpose of this study was to test if BPA action was mediated in vivo during zebrafish development by the orphan nuclear estrogen related receptor (ERR) γ. Combining pharmacological and functional approaches, we demonstrate that the zebrafish ERRγ mediates BPA-induced malformations in otoliths. Using different bisphenol derivatives, we show that different compounds can induce a similar otolith phenotype than BPA and that the binding affinity of these derivatives to the zebrafish ERRγ correlates with their ability to induce otolith malformations. Morpholino knockdown of ERRγ function suppresses the BPA effect on otoliths whereas overexpression of ERRγ led to a BPA-like otolith phenotype. Moreover, a subphenotypical dose of BPA (1 μM) combined with ERRγ overexpression led to a full-dose (50 μM) BPA otolith phenotype. We therefore conclude that ERRγ mediates the otic vesicle phenotype generated by BPA. Our results suggest that the range of pathways perturbed by this compound and its potential harmful effect are larger than expected.—Tohmé, M., Prud’homme, S. M., Boulahtouf, A., Samarut, E., Brunet, F., Bernard, L., Bourguet, W., Gibert, Y., Balaguer, P., Laudet, V. Estrogen-related receptor γ is an in vivo receptor of bisphenol A.

Hydrogen bonding interactions in poly(ε-caprolactone-dimethyl siloxane-ε-caprolactone)/poly(hydroxyether of bisphenol A) triblock copolymer/homopolymer blends and the effect on crystallization, microphase separation and self-assembly

This study investigated the self-assembled microphase separated morphologies that are obtained in bulk, by the complexation of a semicrystalline poly(ε-caprolactone-dimethyl siloxane-ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer and a homopolymer, poly(hydroxyether of bisphenol A) (PH) in tetrahydrofuran (THF). In these blends, microphase separation takes place due to the disparity in intermolecular interactions; specifically, the homopolymer interacts with PCL blocks through hydrogen bonding interactions. The crystallization, microphase separation and crystalline structures of a triblock copolymer/homopolymer blends were investigated. The phase behavior of the complexes was investigated using small-angle X-ray scattering and transmission electron microscopy. At low PH concentrations, PCL interacts relatively weakly with PH, whereas in complexes containing more than 50 wt% PH, the PCL block interacts significantly with PH, leading to the formation of composition-dependent nanostructures. SAXS and TEM results indicate that the lamellar morphology of neat PCL-PDMS-PCL triblock copolymer changes into disordered structures at 40-60 wt% PH. Spherical microdomains were obtained in the order of 40-50 nm in complexes with 80 wt% PH. At this concentration, the complexes show a completely homogenous phase of PH/PCL, with phase-separated spherical PDMS domains. The formation of these nanostructures and changes in morphology depends on the strength of hydrogen bonding between PH/PCL blocks and also the phase separated PDMS blocks.

Nano-capsules of amphiphilic poly (ethylene glycol)-block-poly (bisphenol A carbonate) copolymers via thermodynamic entrapment

The synthesis of amphiphilic poly(ethylene glycol)-block-poly(bisphenol A carbonate) (PEG-b-PC) block copolymer is presented here using a simple bio-chemistry coupling reaction between poly(bisphenol A carbonate) (PC) with a monomethylether poly(ethylene glycol) (mPEG-OH) block, mediated by dicyclohexylcarbodiimide/4-dimethylaminopyridine. This method inherently allows great flexibility in the choice of starting materials as well as easy product purification only requiring phase separation and water washing. Collective data from Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and modulated dynamic scanning calorimetry (MDSC) confirmed the successful attachment of the poly(ethylene glycol) (mPEG-OH) and poly(bisphenol A carbonate) (PC) blocks. The preparation of nano-capsules was carried out by sudden addition of water to PEG-b-PC copolymers dispersed in THF, resulting in the controlled precipitation (i.e. thermodynamic entrapment) of the copolymer. Nano-capsules as small as 85 nm ± 30 nm were produced using this simple and fast methodology. We also demonstrate that encapsulating a water-insoluble bisphenol A diglycidyl ether (DGEBA) epoxy resin is possible highlighting the potential use of these capsules as a chemical delivery system.

Photocatalytic degradation of bisphenol A by HMS/g-C3N4 composite

In this work, hexagonal mesoporous silica/g-C3N4 (HMS/C3N4) was synthesized by heating a mixture of self-prepared HMS and dicyandiamide. The as-prepared materials were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), Fourier transform infrared spectra (FT-IR) and Brunauer–Emmett–Teller analysis (BET). The prepared photocatalysts were applied to decompose bisphenol A (BPA) under UV light illumination. The mass ratios of HMS to melamine were optimized. The results showed that optimal mass ratios HMS to dicyandiamide was 1:1. Even though with the same catalyst dosage (1.0 g/L), the degradation kinetic rate constant of BPA over HMS/C3N4 (0.00526 min−1) was 1.76 times and 1.4 times than those on P25 (0.00298 min−1) and pure C3N4 (0.00383 min−1), while the rate constant of photolysis was only 0.00021 min−1. The enhanced photocatalytic activity of the HMS/C3N4 composite was ascribed to higher specific surface area and less aggregation compared to the pure C3N4. It is feasible and efficient to degrade BPA by HMS/C3N4 composite, which is easier to be separated than pure C3N4 after the pollutant has been removed completely.

Miscibility, crystallization κinetics and real-time small-Angle x-ray scattering investigation of the semicrystalline morphology in thermosetting polymer blends of epoxy resin and poly(ethylene oxide)

Thermosetting polymer blends of poly(ethylene oxide) (PEO) and bisphenol-A-type epoxy resin (ER) were prepared using 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) as curing agent. The miscibility and crystallization behavior of MCDEA-cured ER/PEO blends were investigated by differential scanning calorimetry (DSC). The existence of a single composition-dependent glass transition temperature (Tg) indicates that PEO is completely miscible with MCDEA-cured ER in the melt and in the amorphous state over the entire composition range. Fourier-transform infrared (FTIR) investigations indicated hydrogen-bonding interaction between the hydroxyl groups of MCDEA-cured ER and the ether oxygens of PEO in the blends, which is an important driving force for the miscibility of the blends. The average strength of the hydrogen bond in the cured ER/PEO blends is higher than in the pure MCDEA-cured ER. Crystallization kinetics of PEO from the melt is strongly influenced by the blend composition and the crystallization temperature. At high conversion, the time dependence of the relative degree of crystallinity deviated from the Avrami equation. The addition of a non-crystallizable ER component into PEO causes a depression of both the overall crystallization rate and the melting temperature. The surface free energy of folding σe displays a minimum with variation of composition. The spherulitic morphology of PEO in the ER/PEO blends exhibits typical characteristics of miscible crystalline/amorphous blends, and the PEO spherulites in the blends are always completely volume-filling. Real-time small-angle X-ray scattering (SAXS) experiments reveal that the long period L increases drastically with increasing ER content at the same temperatures. The amorphous cured ER component segregates interlamellarly during the crystallization process of PEO because of the low chain mobility of the cured ER. A model describing the semicrystalline morphology of MCDEA-cured ER/PEO blends is proposed based on the SAXS results. The semicrystalline morphology is a stack of crystalline lamellae; the amorphous fraction of PEO, the branched ER chains and imperfect ER network are located between PEO lamellae.

Phase behavior, crystallization, and hierarchical nanostructures in self-organized thermoset blends of epoxy resin and amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) triblock copolymers

Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and amphiphilic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers were successfully prepared. Two samples of PEO-PPO-PEO triblock copolymer with different ethylene oxide (EO) contents, denoted as EO30 with 30 wt % EO content and EO80 with 80 wt % EO content, were used to form the self-organized thermoset blends of varying compositions using 4,4'-methylenedianiline (MDA) as curing agent. The phase behavior, crystallization, and morphology were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). It was found that macroscopic phase separation took place in the MDA-cured ER/EO30 blends containing 60-80 wt % EO30 triblock copolymer. The MDA-cured ER/EO30 blends with EO30 content up to 50 wt % do not show macroscopic phase separation but exhibit nanostructures on the order of 10-30 nm as revealed by both the TEM and SAXS studies. The AFM study further shows that the ER/EO30 blend at some composition displays structural inhomogeneity at two different nanoscales and is hierarchically nanostructured. The spherical PPO domains with an average size of about 10 nm are uniformly dispersed in the 80/20 ER/EO30 blend; meanwhile, a structural inhomogeneity on the order of 50-200 nm is observed. The ER/EO80 blends are not macroscopically phase-separated over the entire composition range because of the much higher PEO content of the EO80 triblock copolymer. However, the ER/EO80 blends show composition-dependent nanostructures on the order of 10-100 nm. The 80/20 ER/EO80 blend displays hierarchical structures at two different nanoscales, i.e., a bicontinuous microphase structure on the order of about 100 nm and spherical domains of 10-20 nm in diameter uniformly dispersed in both the continuous microphases. The blends with 60 wt % and higher EO80 content are completely volume-filled with spherulites. Bundles of PEO lamellae with spacing of 20-30 nm interwoven with a microphase structure on the order of about 100 nm are revealed by AFM study for the 30/70 ER/EO80 blend.

Nanostructures, semicrystalline morphology, and nanoscale confinement effect on the crystallization kinetics in self-organized block copolymer/thermoset blends

This work reports the first instance of self-organized thermoset blends containing diblock copolymers with a crystallizable thermoset-immiscible block. Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and a low-molecular-weight (Mn = 1400) amphiphilic polyethylene-block-poly(ethylene oxide) (EEO) symmetric diblock copolymer were prepared using 4,4'-methylenedianiline (MDA) as curing agent and were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC). All the MDA-cured ER/EEO blends do not show macroscopic phase separation but exhibit microstructures. The ER selectively mixes with the epoxy-miscible PEO block in the EEO diblock copolymer whereas the crystallizable PE blocks that are immiscible with ER form separate microdomains at nanoscales in the blends. The PE crystals with size on nanoscales are formed and restricted within the individual spherical micelles in the nanostructured ER/EEO blends with EEO content up to 30 wt %. The spherical micelles are highly aggregated in the blends containing 40 and 50 wt % EEO. The PE dentritic crystallites exist in the blend containing 50 wt % EEO whereas the blends with even higher EEO content are completely volume-filled with PE spherulites. The semicrystalline microphase-separated lamellae in the symmetric EEO diblock copolymer are swollen in the blend with decreasing EEO content, followed by a structural transition to aggregated spherical micellar phase morphology and, eventually, spherical micellar phase morphology at the lowest EEO contents. Three morphological regimes are identified, corresponding precisely to the three regimes of crystallization kinetics of the PE blocks. The nanoscale confinement effect on the crystallization kinetics in nanostructured thermoset blends is revealed for the first time. This new phenomenon is explained on the basis of homogeneous nucleation controlled crystallization within nanoscale confined environments in the block copolymer/thermoset blends.

Nanostructures and nanoporosity in thermoset epoxy blends with an amphiphilic polyisoprene-block-poly(4-vinyl pyridine) reactive diblock copolymer

Nanostructured thermoset blends were prepared based on a bisphenol A-type epoxy resin and an amphiphilic reactive diblock copolymer, namely polyisoprene-block-poly(4-vinyl pyridine) (PI-P4VP). Infrared spectra revealed that the P4VP block of the diblock copolymer reacted with the epoxy monomer. However, the non-reactive hydrophobic PI block of the diblock copolymer formed a separate microphase on the nanoscale. Ozone treatment was used to create nanoporosity in nanostructured epoxy/PI-P4VP blends via selective removal of the PI microphase and lead to nanoporous epoxy thermosets; disordered nanopores with the average diameter of about 60 nm were uniformly distributed in the blend with 50 wt% PI-P4VP. Multi-scale phase separation with a distinctly different morphology was observed at the air/sample interface due to the interfacial effects, whereas only uniform microphase separated morphology at the nanoscale was found in the bulk of the blend.

Endocrine disrupting chemicals accumulate in earthworms exposed to sewage effluent

Endocrine disrupting chemicals (EDCs) can alter endocrine function in exposed animals. Such critical effects, combined with the ubiquity of EDCs in sewage effluent and potentially in tapwater, have led to concerns that they could be major physiological disruptors for wildlife and more controversially for humans. Although sewage effluent is known to be a rich source of EDCs, there is as yet no evidence for EDC uptake by invertebrates that live within the sewage treatment system. Here, we describe the use of an extraction method and GC–MS for the first time to determine levels of EDCs (e.g., dibutylphthalate, dioctylphthalate, bisphenol-A and 17β-estradiol) in tissue samples from earthworms (Eisenia fetida) living in sewage percolating filter beds and garden soil. To the best of our knowledge, this is the first such use of these techniques to determine EDCs in tissue samples in any organism. We found significantly higher concentrations of these chemicals in the animals from sewage percolating filter beds. Our data suggest that earthworms can be used as bioindicators for EDCs in these substrates and that the animals accumulate these compounds to levels well above those reported for waste water. The potential transfer into the terrestrial food chain and effects on wildlife are discussed.