A perspective on emerging polymer technologies for bisphenol-A replacement

A Preliminary Study of Thermosets from Epoxy Resins Made Using Low-Toxicity Furan-Based Diols

Glycidyl ethers are prepared from a series of furan-based diols and cured with a diamine to form thermosets. The furan diols demonstrate lower toxicity than bisphenol-A in a prior study. The diglycidyl ethers show improved thermal stability compared to the parent diols. Cured thermosets are prepared at elevated temperature using isophorone diamine (IPDA). Glass transition temperatures are in the range of 30-54 °C and depend on the structure of the furan diol. Coatings are prepared on steel substrates and show very high hardness, good adhesion, and a range of flexibility. Properties compare favorably with a control based on a bisphenol-A epoxy resin. The study demonstrates that epoxy resins based on furan diols, which have been shown to have lower toxicity than bisphenol-A, can form thermosets having properties comparable to a standard epoxy resin system; and thus, are viable as replacements for bisphenol-A epoxy resins.

Synthesis and Properties of Bio-Based Polycarbonates Containing Silicone Blocks

This study aims to investigate the effects of different hydroxy-terminated silicones on the properties of polycarbonate-silicone copolymers (ICS-PC) by introducing flexible and hydrophobic silicone into isosorbide-based polycarbonate through melt transesterification- polycondensation method. Through compatibility and transesterification experiments, it is confirmed that the alcohol-hydroxyl polydimethylsiloxane (a-PDMS) has higher reactivity and silicone conversion than the phenol-hydroxyl polydimethylsiloxane (p-PDMS), but the conversion does not exceed 81%. Polyether-modified silicone (PEMS) exhibits better compatibility and higher reactivity, thus resulting in higher conversion that can reach 86%. Effects of the type and content of silicone on the glass transition temperature (Tg), optical transparency, saturated water absorption, and mechanical strength of ICS-PCs were also discussed. It is found that p-PDMS has higher Tg, hydrophobicity, and mechanical strength with similar silicone content, but the total transmittance does not exceed 60%. In contrast, the PEMS system exhibits better optical transparency due to its improved compatibility with the PC matrix, with a total transmittance of up to 73%, Tg exceeding 150 °C while maintaining excellent flexibility and hydrophobicity. These results are helpful to further improve the comprehensive properties of bio-based polycarbonates.

Recyclable and (Bio)degradable Polyesters in a Circular Plastics Economy

Polyesters carrying polar main-chain ester linkages exhibit distinct material properties for diverse applications and thus play an important role in today's plastics economy. It is anticipated that they will play an even greater role in tomorrow's circular plastics economy that focuses on sustainability, thanks to the abundant availability of their biosourced building blocks and the presence of the main-chain ester bonds that can be chemically or biologically cleaved on demand by multiple methods and thus bring about more desired end-of-life plastic waste management options. Because of this potential and promise, there have been intense research activities directed at addressing recycling, upcycling or biodegradation of existing legacy polyesters, designing their biorenewable alternatives, and redesigning future polyesters with intrinsic chemical recyclability and tailored performance that can rival today's commodity plastics that are either petroleum based and/or hard to recycle. This review captures these exciting recent developments and outlines future challenges and opportunities. Case studies on the legacy polyesters, poly(lactic acid), poly(3-hydroxyalkanoate)s, poly(ethylene terephthalate), poly(butylene succinate), and poly(butylene-adipate terephthalate), are presented, and emerging chemically recyclable polyesters are comprehensively reviewed.

Characteristics and catalytic behavior of Ru-Sn bimetallic catalysts for TMCB hydrogenation to CBDO

A series of Ru-Sn/γ-Al2O3 catalysts were prepared by the immersion method for tetramethylcyclobutane-1,3-dione (TMCB) hydrogenation to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). The effect of the preparation method and reaction technology on TMCB hydrogenation activity was discussed. The catalysts were analyzed by means of XRD, BET, H2-TPR, XPS, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and it was found that the synthesized Ru was distributed on the surface of the carrier in the form of nanoparticles, showing a good catalytic effect. The results showed that when Ru loading was fixed at 5%, Sn was used as an auxiliary agent, and Ru/Sn = 1 : 1 as the catalyst, the reaction conditions were 120 °C, 4 MPa, and 1 h, and the catalytic hydrogenation effect of TMCB on CBDO was the best. The selectivity was as high as 73.5%, and the cis-trans ratio was 1.11. It may be the strong interaction between Ru and Sn under this ratio condition, which leads to the largest number of nano-active centers of elemental Ru. Finally, the reaction mechanism of TMCB hydrogenation to CBDO is discussed.

Enabling New Approaches: Recent Advances in Processing Aliphatic Polycarbonate-Based Materials

Aliphatic polycarbonates (aPCs) have become increasingly popular as functional materials due to their biocompatibility and capacity for on-demand degradation. Advances in polymerization techniques and the introduction of new functional monomers have expanded the library of aPCs available, offering a diverse range of chemical compositions and structures. To accommodate the emerging requirements of new applications in biomedical and energy-related fields, various manufacturing techniques have been adopted for processing aPC-based materials. However, a summary of these techniques has yet to be conducted. The aim of this paper is to enrich the toolbox available to researchers, enabling them to select the most suitable technique for their materials. In this paper, a concise review of the recent progress in processing techniques, including controlled self-assembly, electrospinning, additive manufacturing, and other techniques, is presented. We also highlight the specific challenges and opportunities for the sustainable growth of this research area and the successful integration of aPCs in industrial applications.

Surface Mechanical Properties and Topological Characteristics of Thermoplastic Copolyesters after Precisely Controlled Abrasion

Due to the high probability of surface-to-surface contact of materials during routine applications, surface abrasion remains one of the most challenging factors governing the long-term performance of polymeric materials due to their broad range of tunable mechanical properties, as well as the varied conditions of abrasion (regarding, e.g., rate, load, and contact area). While this concept is empirically mature, a fundamental understanding of mechanical abrasion regarding thermoplastics remains lacking even though polymer abrasion can inadvertently lead to the formation of nano-/microplastics. In the present study, we introduce the concept of precision polymer abrasion (PPA) in conjunction with nanoindentation to elucidate the extent to which controlled wear is experienced by three chemically related thermoplastics under systematically varied abrasion conditions. While depth profiling of one polymer reveals a probe-dependent change in modulus, complementary results from positron annihilation lifetime spectroscopy confirm that the polymer density changes measurably, but not appreciably, with depth over the depth range explored. After a single PPA pass, the surface moduli of the polymers noticeably increase, whereas the corresponding increase in hardness is modest. The dependence of wear volume on the number of PPA passes is observed to reach limiting values for two of the thermoplastics, and application of an empirical model to the data yields estimates of these values for all three thermoplastics. These results suggest that the metrics commonly employed to describe the surface abrasion of polymers requires careful consideration of a host of underlying factors.

USAEME-GC/MS Method for Easy and Sensitive Determination of Nine Bisphenol Analogues in Water and Wastewater

A new, simple and sensitive method for isolating nine compounds from the bisphenol group (analogues: A, B, C, E, F, G, Cl₂, Z, AP) based on one-step liquid-liquid microextraction with in situ acylation followed by gas chromatography-mass spectrometry was developed and validated using influent and effluent wastewaters. The chemometric approach based on the Taguchi method was used to optimize the main conditions of simultaneous extraction and derivatization. The recoveries of the proposed procedure ranged from 85 to 122%, and the repeatability expressed by the coefficient of variation did not exceed 8%. The method's limits of detection were in the range of 0.4-64 ng/L, and the method's limits of quantification ranged from 1.3 to 194 ng/L. The developed method was used to determine the presence of the tested compounds in wastewater from a municipal wastewater treatment plant located in northeastern Poland. From this sample, eight analytes were detected. Concentrations of bisphenol A of 400 ng/L in influent and 100 ng/L in effluent were recorded, whereas other bisphenols reached 67 and 50 ng/L for influent and effluent, respectively. The removal efficiency of bisphenol analogues in the tested wastewater treatment plant ranged from 7 to approximately 88%.

The accumulation of microplastic pollution in a commercially important fishing ground

The Irish Sea is an important area for Norway Lobster Nephrops norvegicus fisheries, which are the most valuable fishing resource in the UK. Norway lobster are known to ingest microplastic pollution present in the sediment and have displayed reduced body mass when exposed to microplastic pollution. Here, we identified microplastic pollution in the Irish Sea fishing grounds through analysis of 24 sediment samples from four sites of differing proximity to the Western Irish Sea Gyre in both 2016 and 2019. We used µFTIR spectroscopy to identify seven polymer types, and a total of 77 microplastics consisting of fibres and fragments. The mean microplastics per gram of sediment ranged from 0.13 to 0.49 and 0 to 1.17 MP/g in 2016 and 2019, respectively. There were no differences in the microplastic counts across years, and there was no correlation of microplastic counts with proximity to the Western Irish Sea Gyre. Considering the consistently high microplastic abundance found in the Irish Sea, and the propensity of N. norvegicus to ingest and be negatively impacted by them, we suggest microplastic pollution levels in the Irish Sea may have adverse impacts on N. norvegicus and negative implications for fishery sustainability in the future.

Sugar-Based Polymers with Stereochemistry-Dependent Degradability and Mechanical Properties

Stereochemistry in polymers can be used as an effective tool to control the mechanical and physical properties of the resulting materials. Typically, though, in synthetic polymers, differences among polymer stereoisomers leads to incremental property variation, i.e., no changes to the baseline plastic or elastic behavior. Here we show that stereochemical differences in sugar-based monomers yield a family of nonsegmented, alternating polyurethanes that can be either strong amorphous thermoplastic elastomers with properties that exceed most cross-linked rubbers or robust, semicrystalline thermoplastics with properties comparable to commercial plastics. The stereochemical differences in the monomers direct distinct intra- and interchain supramolecular hydrogen-bonding interactions in the bulk materials to define their behavior. The chemical similarity among these isohexide-based polymers enables both statistical copolymerization and blending, which each afford independent control over degradability and mechanical properties. The modular molecular design of the polymers provides an opportunity to create a family of materials with divergent properties that possess inherently built degradability and outstanding mechanical performance.

Blended vinylogous urethane/urea vitrimers derived from aromatic alcohols

An in-depth investigation of the condensation, substitution and transamination reactions in blended vinylogous urethane/urea vitrimers derived from commercially relevant alcohols, proven by detailed model studies and 16 prepared vitrimer networks.

Pinene-Based Oxidative Synthetic Toolbox for Scalable Polyester Synthesis

Generation of renewable polymers is a long-standing goal toward reaching a more sustainable society, but building blocks in biomass can be incompatible with desired polymerization type, hampering the full implementation potential of biomaterials. Herein, we show how conceptually simple oxidative transformations can be used to unlock the inherent reactivity of terpene synthons in generating polyesters by two different mechanisms starting from the same α-pinene substrate. In the first pathway, α-pinene was oxidized into the bicyclic verbanone-based lactone and subsequently polymerized into star-shaped polymers via ring-opening polymerization, resulting in a biobased semicrystalline polyester with tunable glass transition and melting temperatures. In a second pathway, polyesters were synthesized via polycondensation, utilizing the diol 1-(1'-hydroxyethyl)-3-(2'-hydroxy-ethyl)-2,2-dimethylcyclobutane (HHDC) synthesized by oxidative cleavage of the double bond of α-pinene, together with unsaturated biobased diesters such as dimethyl maleate (DMM) and dimethyl itaconate (DMI). The resulting families of terpene-based polyesters were thereafter successfully cross-linked by either transetherification, utilizing the terminal hydroxyl groups of the synthesized verbanone-based materials, or by UV irradiation, utilizing the unsaturation provided by the DMM or DMI moieties within the HHDC-based copolymers. This work highlights the potential to apply an oxidative toolbox to valorize inert terpene metabolites enabling generation of biosourced polyesters and coatings thereof by complementary mechanisms.

DFT Analysis of Organotin Catalytic Mechanisms in Dehydration Esterification Reactions for Terephthalic Acid and 2,2,4,4-Tetramethyl-1,3-cyclobutanediol

Polyesters synthesized from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD) and terephthalic acid (TPA) are improved alternatives to toxic polycarbonates based on bisphenol A. In this work, we use ωB97X-D/LANL2DZdp calculations, in the presence of a benzaldehyde polarizable continuum model solvent, to show that esterification of TMCD and TPA will reduce and subsequently dehydrate a dimethyl tin oxide catalyst, becoming ligands on the now four-coordinate complex. This reaction then proceeds most plausibly by an intramolecular acyl-transfer mechanism from the tin complex, aided by a coordinated proton donor such as hydronium. These findings are a key first step in understanding polyester synthesis and avoiding undesirable side reactions during production.

Biomass-derived chemical substitutes for bisphenol A: recent advancements in catalytic synthesis

Bisphenol A is an oil-derived, large market volume chemical with a wide spectrum of applications in plastics, adhesives and thermal papers. However, bisphenol A is not considered safe due to its endocrine disrupting properties and reproductive toxicity. Several functional substitutes of bisphenol A have been proposed in the literature, produced from plant biomass. Unless otherwise specified, the present review covers the most significant contributions that appeared in the time span January 2015-August 2019, describing the sustainable catalytic synthesis of rigid diols from biomass derivatives. The focus is thereupon on heterogeneous catalysis, use of green solvents and mild conditions, cascade processes in one-pot, and continuous flow setups. More than 500 up-to-date references describe the various substitutes proposed and the catalytic methods for their manufacture, broken down according to the main biomass types from which they originate.

Hydrophobically Modified Isosorbide Dimethacrylates as a Bisphenol-A (BPA)-Free Dental Filling Material

A series of bio-based hydrophobically modified isosorbide dimethacrylates, with para-, meta-, and ortho- benzoate aromatic spacers (ISBGBMA), are synthesized, characterized, and evaluated as potential dental restorative resins. The new monomers, isosorbide 2,5-bis(4-glyceryloxybenzoate) dimethacrylate (ISB4GBMA), isosorbide 2,5-bis(3-glyceryloxybenzoate) dimethacrylate (ISB3GBMA), and isosorbide 2,5-bis(2-glyceryloxybenzoate) dimethacrylate (ISB2GBMA), are mixed with triethylene glycol dimethacrylate (TEGDMA) and photopolymerized. The resulting polymers are evaluated for the degree of monomeric conversion, polymerization shrinkage, water sorption, glass transition temperature, and flexural strength. Isosorbide glycerolate dimethacrylate (ISDGMA) is synthesized, and Bisphenol A glycerolate dimethacrylate (BisGMA) is prepared, and both are evaluated as a reference. Poly(ISBGBMA/TEGDMA) series shows lower water sorption (39-44 µg/mm³) over Poly(ISDGMA/TEGDMA) (73 µg/mm³) but higher than Poly(BisGMA/TEGDMA) (26 µg/mm³). Flexural strength is higher for Poly(ISBGBMA/TEGDMA) series (37-45 MPa) over Poly(ISDGMA/TEGDMA) (10 MPa) and less than Poly(BisGMA/TEGDMA) (53 MPa) after immersion in phosphate-buffered saline (DPBS) for 24 h. Poly(ISB2GBMA/TEGDMA) has the highest glass transition temperature at 85 °C, and its monomeric mixture has the lowest viscosity at 0.62 Pa·s, among the (ISBGBMA/TEGDMA) polymers and monomer mixtures. Collectively, this data suggests that the ortho ISBGBMA monomer is a potential bio-based, BPA-free replacement for BisGMA, and could be the focus for future study.

Protecting Group-Controlled Remote Regioselective Electrophilic Aromatic Halogenation Reactions

Being able to utilize a protecting group to influence remote regiocontrol offers a simple alternative approach to direct late-stage functionalization of complex organic molecules. However, protecting groups that have the ability to influence reaction regioselectivity remote to their local chemical environment are not widely reported in the literature. Herein, we report the development of remote regioselective electrophilic aromatic substitution (S_EAr) reactions that are enabled via the application of the tetrafluoropyridyl (TFP) phenol-protecting group. We demonstrate that through sequential reactions and protection/deprotection of the TFP group, substitution patterns that do not conform to classical S_EAr regioselectivity rules can be readily accessed.

A Sensitive Impedimetric Sensor Based on Biosourced Polyphosphine Films for the Detection of Lead Ions

In this work, impedimetric sensors were developed for the detection of the four WFD heavy metals Pb2+, Cd2+, Hg2+ and Ni2+, by the modification of a gold electrode with four partially biosourced polyphosphine polymers. These polymers were obtained with satisfactory yields by polycondensation of the bis(4-fluorophenyl)(4-methylphenyl)phosphine sulfide and the bis(4-fluorophenyl)(4-methylphenyl)phosphine oxide using isosorbide or bisphenol A. The chemical structures and number-average molecular weights of the resulting polymers were determined by NMR spectroscopy (1H, 19F, and 31P) and by size exclusion chromatography. Glass transition temperatures varied between 184 and 202 °C depending on the composition of polymers. The bio-based poly(etherphosphine) oxide modified sensor showed better analytical performance than petrochemical based oxide for the detection of Pb2+. A detection limit of 10−10 g/L or 0.5 pM, which is 104 times lower than that of the anodic stripping voltammetric and the potentiometric sensors. A reversibility is obtained through rinsing of the impedimetric sensor with an EDTA solution.

Isosorbide bis(methyl carbonate) synthesis from isosorbide and dimethyl carbonate: the key role of dual basic–nucleophilic catalysts

Isosorbide bis(methyl carbonate) (IBMC) is a scarcely studied green chemical with potential applications in the manufacturing of non-isocyanate polyurethanes and bisphenol A-free polycarbonates. Its synthesis by transesterification of isosorbide with dimethyl carbonate (DMC) is very negatively influenced by the presence of small amounts of acidic impurities in isosorbide when heterogeneous inorganic carbonates such as potassium and cesium carbonates are used as catalysts. In this paper it is shown that the problem can be solved by using homogeneous catalysts consisting of nitrogenated bases and superbases having a suitable dual nucleophilic–basic character and able to form a highly reactive acyl intermediate with the electrophilic reactant DMC. Cycloaliphatic secondary and tertiary amines, guanidines and amidines covering a nucleophilicity parameter (N) range between 13.58 and 20.58 in either acetonitrile or dichloromethane, and a pK_a range in acetonitrile between 15.68 and 26.02 have been tested in batchwise mode. Highly active catalysts leading to hydroxyl conversions of 84–93% require a minimum N of 16 and a pK_a ranging from 18.0 to 26.0. Within this pK_a range, N must increase by about 0.5–0.6 units per each unit the pK_a falls to keep the catalytic activity, indicating that nucleophilicity has approximately twice as much influence as basicity on the catalytic activity. One guanidine (TBD), one amidine (DBN) and three cycloaliphatic secondary amines (N-methylpyrrolidine, quinuclidine and DABCO) have been found to be excellent catalysts at 5 mol% vs. ISO. The side reaction leading to oligomer formation is not avoided, with oligomers, mainly the dimer, affording 6 wt% of the crude product independently of hydroxyl-conversion and catalyst type.

Basic–nucleophilic nitrogenated organocatalysts catalyze the synthesis of isosorbide bis(methyl carbonate), with nucleophilicity having an influence twice as much as basicity on catalytic activity.

Synthesis and characterization of BPA-free polyesters by incorporating a semi-rigid cyclobutanediol monomer

A trans-1,3-cyclobutane-containing diol (CBDO-1) has been synthesized and introduced to materials science as a versatile monomer and a possible phenol-free BPA replacement.

Inherently degradable cross-linked polyesters and polycarbonates: resins to be cheerful

We summarise the most recent advances in the synthesis and characterisation of degradable thermosetting polyester and polycarbonates, including partially degradable systems derived from itaconic acid and isosorbide.

Determination of Endocrine Disruption Potential of Bisphenol A Alternatives in Food Contact Materials Using In Vitro Assays: State of the Art and Future Challenges

Alternatives to bisphenol A (BPA) are developed for food contact materials as a result of increasing evidence of exposure-correlated harmful effects of BPA. In vitro assays provide the fast, affordable, and mechanism insightful ways to screen endocrine disruption (ED), which is a major concern of new BPA alternatives. In this review, we summarize the safety and regulation information on the alternatives to BPA, review the state of the art of in vitro assays for ED evaluation, highlight their advantages and limitations, and discuss the challenges and future research needs. Our review shows that ligand binding, reporter gene, cell proliferation, and steroidogenesis are four commonly used in vitro assays to determine the ED at the response of receptor, gene transcription, and whole cell level. Major challenges are found from in vitro-in vivo translation and identification of ED chemicals in polymers. More studies on these areas are needed in the future.

Study on the Synthetic Characteristics of Biomass-Derived Isosorbide-Based Poly(arylene ether ketone)s for Sustainable Super Engineering Plastic

Demand for the development of novel polymers derived from biomass that can replace petroleum resources has been increasing. In this study, biomass-derived isosorbide was used as a monomer in the polymerization of poly(arylene ether ketone)s, and its synthetic characteristics were investigated. As a phase-transfer catalyst, crown ether has increased the weight-average molecular weight of polymers over 100 kg/mol by improving the reaction efficiency of isosorbide and minimizing the effect of moisture. By controlling the experimental parameters such as halogen monomer, polymerization solvent, time, and temperature, the optimal conditions were found to be fluorine-type monomer, dimethyl sulfoxide, 24 h, and 155 °C, respectively. Biomass contents from isosorbide-based polymers were determined by nuclear magnetic resonance and accelerator mass spectroscopy. The synthesized polymer resulted in a high molecular weight that enabled the preparation of transparent polymer films by the solution casting method despite its weak thermal degradation stability compared to aromatic polysulfone. The melt injection molding process was enabled by the addition of plasticizer. The tensile properties were comparable or superior to those of commercial petrochemical specimens of similar molecular weight. Interestingly, the prepared specimens exhibited a significantly lower coefficient of thermal expansion at high temperatures over 150 °C compared to polysulfone.

Sustainable and recyclable super engineering thermoplastic from biorenewable monomer

Environmental and health concerns force the search for sustainable super engineering plastics (SEPs) that utilise bio-derived cyclic monomers, e.g. isosorbide instead of restricted petrochemicals. However, previously reported bio-derived thermosets or thermoplastics rarely offer thermal/mechanical properties, scalability, or recycling that match those of petrochemical SEPs. Here we use a phase transfer catalyst to synthesise an isosorbide-based polymer with a high molecular weight >100 kg mol-1, which is reproducible at a 1-kg-scale production. It is transparent and solvent/melt-processible for recycling, with a glass transition temperature of 212 °C, a tensile strength of 78 MPa, and a thermal expansion coefficient of 23.8 ppm K-1. Such a performance combination has not been reported before for bio-based thermoplastics, petrochemical SEPs, or thermosets. Interestingly, quantum chemical simulations show the alicyclic bicyclic ring structure of isosorbide imposes stronger geometric restraint to polymer chain than the aromatic group of bisphenol-A.

Recent Advances in Bio-Based Flame Retardant Additives for Synthetic Polymeric Materials

It would be difficult to imagine how modern life across the globe would operate in the absence of synthetic polymers. Although these materials (mostly in the form of plastics) have revolutionized our daily lives, there are consequences to their use, one of these being their high levels of flammability. For this reason, research into the development of flame retardant (FR) additives for these materials is of tremendous importance. However, many of the FRs prepared are problematic due to their negative impacts on human health and the environment. Furthermore, their preparations are neither green nor sustainable since they require typical organic synthetic processes that rely on fossil fuels. Because of this, the need to develop more sustainable and non-toxic options is vital. Many research groups have turned their attention to preparing new bio-based FR additives for synthetic polymers. This review explores some of the recent examples made in this field.

A synthetic strategy toward isosorbide polycarbonate with a high molecular weight: the effect of intermolecular hydrogen bonding between isosorbide and metal chlorides

Isosorbide polycarbonate (ISB-PC) was prepared by melt transesterification and polycondensation reaction by employing ISB and diphenyl carbonate (DPC) as monomers.

Cytotoxicity measurement of Bisphenol A (BPA) and its substitutes using human keratinocytes

Bisphenol-A (BPA) was first synthesized in the 1890s and has been used in many plastic products. However, BPA is known to act as an endocrine disruptor and has been found to be toxic to human health. Many alternative substances have been developed to replace BPA, but it is still widely used worldwide. In this study, we identified the potential cytotoxicity of BPA by evaluating toxicity using human keratinocytes. Also, we evaluated cytotoxicity of BPA substitutes to determine their suitability as an alternative to BPA. The proliferation assay using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry and western blot analysis showed that BPA significantly affect cell viability, induction of apoptotic fraction and increased activation of DNA-damage marker protein. In addition, through the same experiments, the substitutes of BPA were shown to be significantly less toxic than BPA, and the least toxicity was observed with 1,4-cyclohexanedimethanol (CHDM) and terephthalic acid (TPA). In conclusion, this study suggests that cytotoxicity of BPA induces apoptosis of human keratinocytes, and that CHDM and TPA are the most suitable substitutes for BPA.

Influence of cyclobutane segments in cycloaliphatic decahydronaphthalene-containing copolyesters

Melt transesterification polycondensation enabled the incorporation of rigid, cycloaliphatic diols (2,2,4,4-tetramethylcyclobutane-1,3-diol) into decahydronaphthalene-containing copolyesters, which resulted in amorphous, optically clear materials. Glass transition temperatures approached 155°C and followed predictable trends using the Fox equation for randomly sequenced copolymers. Dynamic mechanical analysis identified several low-temperature relaxations attributed to the complex motions of the decahydronaphthalate and cyclohexyl rings within the polymer backbone. Furthermore, incorporating cyclobutane rings suppressed the low-temperature local mobility, revealing a strong structural dependence on these relaxations. The rheological simplicity of these nonassociating chains permitted analysis over a large frequency window using time–temperature superposition. As a result, the characteristic relaxation times provided insight into chain dynamics and the propensity for chain entanglements. Finally, positron annihilation lifetime spectroscopy probed hole-free volume and reinforced the trends observed with oxygen permeability measurements.