Ethylene Adipate Research Articles

Fabrication of PLA-Based Nanoneedle Patches Loaded with Transcutol-Modified Chitosan Nanoparticles for the Transdermal Delivery of Levofloxacin.

Current transdermal drug delivery technologies, like patches and ointments, effectively deliver low molecular weight drugs through the skin. However, delivering larger, hydrophilic drugs and macromolecules remains a challenge. In the present study, we developed novel transdermal nanoneedle patches containing levofloxacin-loaded modified chitosan nanoparticles. Chitosan was chemically modified with transcutol in three ratios (1/1, 1/2, 1/3, w/w), and the optimum ratio was used for nanoparticle fabrication via the ionic gelation method. The successful modification was confirmed using ATR-FTIR spectroscopy, while DLS results revealed that only the 1/3 ratio afforded suitably sized particles of 220 nm. After drug encapsulation, the particle size increased to 435 nm, and the final formulations were examined via XRD and an in vitro dissolution test, which suggested that the nanoparticles reach 60% release in a monophasic pattern at 380 h. We then prepared transdermal patches with pyramidal geometry nanoneedles using different poly(lactic acid)/poly(ethylene adipate) (PLA/PEAd) polymer blends of varying ratios, which were characterized in terms of morphology and mechanical compressive strength. The 90/10 blend exhibited the best mechanical properties and was selected for further testing. Ex vivo permeation studies proved that the nanoneedle patches containing drug-loaded nanoparticles achieved the highest levofloxacin permeation (88.1%).

Photostability of CsPbBr3 nanocrystals modified with poly(ethylene adipate)

All inorganic CsPbBr3 nanocrystals (NCs) have gained significant attention due to their potential as light-emitting diodes, solar cells and other optoelectronic devices. However, to a certain extent, the stability issues of CsPbBr3 NCs under water, light, and thermal conditions limit their further applications. In order to improve stability, this article proposes a strategy of modifying CsPbBr3 NCs with poly(ethylene adipate) (PEA). The surface passivation of macromolecular polymer PEA not only increases the distance between NCs which inhibits the aggregation of small NCs, but also provides a dense protective layer to protect NCs from corrosion by water, air and light. Therefore, the performance of PEA-modified CsPbBr3 NCs in terms of optical properties and stability is significantly improved. The photoluminescence intensity of PEA-modified CsPbBr3 NCs remains at about 40% of the initial intensity when heated to 100 °C, while that of pure CsPbBr3 NCs has decreased to less than 10%. The photoluminescence intensity of PEA-modified CsPbBr3 NCs decreased to 83% of the initial intensity after 7 cycles of heating to 100 °C and then cooling to room temperature, while that of pure CsPbBr3 NCs decreased to 13%. Meanwhile, the PL intensity of PEA-modified CsPbBr3 NCs remained at 66% of the initial intensity after 10 h under 365 nm ultraviolet light, and there is no obvious red shift in PL spectra, while the PL intensity of pure CsPbBr3 NCs only maintained 21% of the initial intensity, accompanied by obvious red shift in PL spectra. The results show that the PEA-modified CsPbBr3 NCs have a positive effect on stability.

Depolymerization of Polyesters by Transesterification with Ethanol Using (Cyclopentadienyl)titanium Trichlorides

Exclusive chemical conversions of polyesters [poly(ethylene adipate) (PEA), poly(butylene adipate) (PBA), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT)] to the corresponding monomers (diethyl adipate, diethyl terephthalate, ethylene glycol, 1,4-butane diol) by transesterification with ethanol using Cp’TiCl3 (Cp’ = Cp, Cp*) catalyst have been demonstrated. The present acid-base-free depolymerizations by Cp’TiCl3 exhibited completed conversions (>99%) of PET, PBT to afford diethyl terephthalate and ethylene glycol or 1,4-butane diol exclusively (selectivity >99%) without formation of any other by-products in the NMR spectra (150–170 °C, Ti 1.0, or 2.0 mol%). The resultant reaction mixture after the depolymerization of PBA with ethanol via the CpTiCl3 catalyst (1.0 mol%, 150 °C, 3 h), consisting of diethyl adipate and 1,4-butane diol, was heated at 150 °C in vacuo for 24 h to afford high molecular weight recycled PBA with unimodal molecular weight distribution (Mn = 11,800, Mw/Mn = 1.6), strongly demonstrating a possibility of one-pot (acid-base-free) closed-loop chemical recycling.

An efficient cyclodepolymerization route for the chemical recycling of poly(ethylene adipate)

We present here a green cyclodepolymerization route for the chemical recycling of poly(ethylene adipate) to its cyclic oligomers based on ring–chain equilibria in solution.

Evaluation of poly(lactic acid)/ and poly(lactic-co-glycolic acid)/ poly(ethylene adipate) copolymers for the preparation of paclitaxel loaded drug nanoparticles

The present study evaluates the use of novel poly(lactic acid)/poly(ethylene adipate) (PLA-PEAd) and poly(lactic-co-glycolic acid)/poly(ethylene adipate) (PLGA-PEAd) copolymers for the preparation of paclitaxel (PTX) loaded nanoparticles (NPs). Specifically, four copolymers, namely PLA-PEAd and PLGA-PEAd at 90/10 and 75/25 w/w ratio, were prepared via reactive melt mixing, and their successful synthesis was verified by proton nuclear magnetic resonance (1H NMR and 13C NMR) and FTIR analysis. Then, the enzymic hydrolysis and cytotoxicity characteristics of them were comprehensively assessed. The results confirmed that all synthesized copolymers can be enzymatically hydrolyzed (i.e., are biodegradable) with low cytotoxicity, and hence can be used as suitable drug matrix/carriers. In the next step, the newly synthesized copolymers were used to prepare PTX-loaded NPs via o/w emulsification/solvent evaporation method. The size of the PTX-loaded NPs varied from 250 to 490 nm, depending on the polyester used, while X-ray diffraction analysis revealed that the drug was amorphously dispersed in all cases. Scanning electron microscopy showed the formation of spherical NPs with smooth surfaces, while good drug loading and encapsulation efficiency values were obtained in all cases. Finally, the in vitro dissolution analysis of all prepared PTX-loaded NPs showed biphasic drug dissolution profiles in all cases, while the use of PEAd resulted in the formation of NP having highly tunable dissolution properties.

Novel efficient method of chemical upcycling of waste poly(ethylene terephthalate) bottles by acidolysis with adipic acid under microwave irradiation

In this work, for the first time, the reaction of post-consumer poly(ethylene terephthalate) (PET) bottles with adipic acid (AA) under microwave (MW) irradiation without catalyst was investigated. An efficient procedure to isolate various materials was proposed, namely the excess adipic acid, terephthalic acid, and novel oligo(ethylene adipate-co-terephthalate) (OEAT) with carboxylic end groups. The structure of OEAT was confirmed by FTIR, 1H-NMR, and ESI-MS. OEAT is a mixture of oligomers, containing co-oligomers of ethylene adipate and terephthalate, and nonreacted adipic acid. An explanation of the mechanism of the reaction was proposed through a concerted six-member ring formation including an O-alkyl fission process. Adipic acid and terephthalic acid were recovered and used as basic materials. OEAT was used for curing diglycidyl ether of bisphenol-A (DGEBA) resin and applied as a coating material. This upcycling method of PET showed high atom efficiency and high isolated yield reaction.

Polymorphism and grating assembly with unique iridescence features in periodically banded poly(ethylene adipate)

Poly(ethylene adipate) (PEA) forms either ring-banded spherulites (RBS) crystallized between T c = 20–32 °C, or ringless spherulites (RLS) if crystallized away from this range. Morphologies differ correspondingly in their interior structures, as well as polymorphism in that α-form crystal is packed in RLS but combination of α, β crystals are dominantly in ring-banded one. Internal structure of banded spherulites is determined by dissection analyses. Interior lamellae of the banded PEA spherulites are assembled as discontinuous concentric-shell structures with concave shapes like cut onions. The radial-direction plate-like lamellae intersection constitutes each shell with the tangential cilia-like lamellae. Interior tangential lamellae bend or branch out perpendicularly at 90° angle in the radial direction to merge with the radial plate-like lamellae. Through designing optimal regularly-banded morphologies, prominent photonic iridescence is attained in the PEA banded spherulites. Moreover, the PEA banded spherulitic morphology can structured the light with circular pattern by laser interference. Light-interfering grating structures for iridescence applications can be achieved by custom-designing the PEA-RBS assemblies. The interior 3D self-assembly in periodically banded poly(ethylene adipate) is analyzed, and proved to be able to custom-structured as gratings, which, along with the top-surface periodicity, are capable of displaying optical iridescence for potential applications. • PEA spherulite morphology differs correspondingly with variation in polymorphism. • Monomorphic crystal is packed in ringless PEA spherulite but polymorphic crystals are dominantly in ring-banded one. • Interior lamellae of the banded PEA spherulites are assembled as discontinuous cross-hatch gratings. • Light-interference grating structures for iridescence applications can be achieved by custom-designing the PEA-RBS.

Dielectric and calorimetric study in renewable polymer blends based on poly(ethylene adipate) and poly(lactic acid) with microphase separation

A series of sustainable polymeric blends based on poly(lactic acid) (PLA) and poly(ethylene adipate) (PEAd), are studied herein, from the point of view of thermal transitions, crystallization and molecular mobility. The blending aims at the manipulation of the chains' mobility and crystallization of PLA, as PEAd exhibits quite lower glass transition temperature and is expected to act as plasticizer. In a next step, such systems are envisaged for use as patches for transdermal administration of antimicrobial drugs, formed as fibril-systems via the electrospinning technique. For the present work, we have employed calorimetry and the advanced technique of dielectric spectroscopy as main investigation tools, which are supplemented by polarized microscopy. Regarding molecular mobility, the overall dynamics (local and segmental) map was constructed for these systems, for the first time. The presence of PEAd imposed plasticization on the PLA chains, as manifested by the lowering of Tg and acceleration of segmental dynamics. On the other hand, PEAd is deplasticized at the presence of PLA. In addition, the fragility of PLA chains drops at the presence of PEAd, suggesting increasing in the cooperativity length, or else, a chain-chain detaching. The overall data are also indicative of the partially miscible polymers. Regarding crystallization, neat PLA exhibits neither hot nor cold crystallization, whereas, strikingly, with the addition of PEAd, the nucleation of PLA is facilitated and strong cold crystallization is systematically recorded. The phenomenon seems to be connected with both the plasticization of the PLA chains along with the homogeneous microphase separation of the two polymers (partial immiscibility), overall, with size-effects. Local dynamics, originating from more localized molecular motions, exhibit systematic alternation in the blends in both the time scale and dielectric strength. Our results show that the PLA/PEAd blends are ‘phase change materials’ with potentials to tune the materials performance, connected, among others, with the semicrystalline morphology and the interchain distances.

Transesterification of Methyl-10-undecenoate and Poly(ethylene adipate) Catalyzed by (Cyclopentadienyl)titanium Trichlorides as Model Chemical Conversions of Plant Oils and Acid-, Base-Free Chemical Recycling of Aliphatic Polyesters

Highly active and exclusive transesterifications of methyl 10-undecenoate with alcohols (cyclohexanemethanol, 1,4-cyclohexanedimethanol, 10-undecen-1-ol, 3-hexanol) have been demonstrated by Cp′TiCl3 (Cp′ = Cp, C5Me5) at 100–120 °C. The CpTiCl3 enabled depolymerization of poly(ethylene adipate) by the transesterification (>99% conv., 0.25–0.5 mol % Ti) at 120 °C; the depolymerization completed after 6 h at 150 °C (0.5 mol % Ti).

Biodegradability Assessment of Polyester Copolymers Based on Poly(ethylene adipate) and Poly(ε-caprolactone).

Biodegradable polymers contain chains that are hydrolytically or enzymatically cleaved, resulting in soluble degradation products. Biodegradability is particularly desired in biomedical applications, in which degradation of the polymer ensures clearance from the body and eliminates the need for retrieval or explant. In this study, a homologues series of poly(ε-caprolactone)-b-poly(ethylene adipate)-b-poly(ε-caprolactone) (PCL-b-PEA-b-PCL) block copolymers, with constant PEA molar mass and different PCL sequence lengths was obtained. The starting point of these copolymers was a dihydroxy-PEA precursor with a molar mass (Mn) of 2500 g/mol. Mn values of the PCL varied between 1000 and 10,000 g/mol. Both the precursors and the copolymers were characterized using different physicochemical methods, such as: NMR, SEC, Maldi-TOFF, DSC, and ATG. The molecular characteristics of the copolymers were in a direct correlation with the sequence length of the PCL. Enzymatic degradability studies were also conducted by using cell-free extract containing Pseudomonas aeruginosa PAO1 for 10 and 21 days, and it appeared that the presence of the PEA central sequence has an important influence on the biodegradability of the copolymer samples. In fact, copolymer PCL7000-PEA2500-PCL7000 had a weight loss of around 50% after 10 days whereas the weight loss of the homopolymer PCL, with a similar Mn of 14,000 g/mol, was only 6%. The results obtained in this study indicate that these copolymer samples can be further used for the preparation of drug delivery systems with modulated biodegradability.

Synthesis and Characterization of Crosslinked Castor Oil-Based Polyurethane Nanocomposites Based on Novel Silane-Modified Isocyanate and Their Potential Application in Heat Insulating Coating.

An isocyanate with trimethoxysilane groups at the side chains (IPDI-M) was synthesized via an addition between the mercaptopropyl trimethoxysilane groups (MPTMS) and IPDI tripolymer (IPDI-T). Then, silane grafted isocyanate as the functional hard segment, castor oil as the soft segment, poly (ethylene adipate) diol (PEA) as the chain extender, and MPTMS as an end-capping reagent were applied to form a series of organosilicon hybrid bio-based polyurethane (CPUSi). The effect of the IPDI-M contents on the thermal stability, mechanical properties, and surface properties of the resulting product was systematically investigated. Profit from the Si–O–Si crosslinked structures formed from MPTMS curing, the tensile strength, and Young’s modulus of the resulting products increased from 9.5 MPa to 22.3 Mpa and 4.05 Mpa to 81.59 Mpa, respectively, whereas the elongation at break decreased from 342% to 101%. The glass transition temperature, thermal stability, transparency, hydrophobicity, and chemical resistance were remarkably strengthened for the obtained organosilicon-modified polyurethane with the increasing MPTMS content. At the end of the work, the thermal insulation coating that was based on CPUSi and ATO can effectively block near-infrared rays, and the temperature difference between the inside and outside of the film reached 15.1 °C.

Modified Release of the Pineal Hormone Melatonin from Matrix Tablets Containing Poly(L-lactic Acid) and Its PLA-co-PEAd and PLA-co-PBAd Copolymers.

In terms of drug delivery, the attractive properties of poly(L-lactic acid) (PLA) and its aliphatic polyesters, poly(ethylene adipate) (PEAd) and poly(butylene adipate) (PBAd), render them ideal co-formulants for the preparation of modified-release pharmaceutical formulations. Furthermore, we have previously demonstrated that by adding a “softer” aliphatic polyester onto the macromolecular chain of PLA, i.e., PEAd or PBAd, resulting in the formation of the PLA’s copolymers (PLA-co-PEAd and PLA-co-PBAd, in 95/5, 90/10, 75/25 and 50/50 weight ratios), the hydrolysis rate is also severely affected, leading to improved dissolution rates of the active pharmaceutical ingredients (API). In the present report, we communicate our findings on the in vitro modified release of the chronobiotic hormone melatonin (MLT), in aqueous media (pH 1.2 and 6.8), from poly(L-lactic acid) and the aforementioned copolymer matrix tablets, enriched with commonly used biopolymers, such as hydroxypropylmethylcellulose (HPMC K15), lactose monohydrate, and sodium alginate. It was found that, depending on the composition and the relevant content of these excipients in the matrix tablets, the release of MLT satisfied the sought targets for fast sleep onset and sleep maintenance. These findings constitute a useful background for pursuing relevant in vivo studies on melatonin in the future.

Unusually negative, single ring-banded spherulites of poly(ethylene adipate) formed via controlled stepwise evaporative crystallization

Double ring-banded poly(ethylene adipate) (PEA) spherulites consisting of periodically twisted lamellae were usually observed. In this work, besides the usually positive and negative spherulites, we report a novel transitional morphology of negatively birefringent, single ring-banded PEA spherulites formed in solution-cast films via controlled stepwise evaporative crystallization. The periodic structure shows a nature of rhythmic change of thickness deriving from alternating stacks of lamellar crystals with tilted or even edge-on orientations, and its negative birefringence is attributed to the coupling of spherulite radius of the a*-axis and the strongly oblique orientation of the lamellae in ridges. We believe that such evaporative-flow-induced rhythmic crystal growth into ringed structures can be observed for most crystallizable polymers under suitable crystallization conditions.

The Effect of Trifluoroacetic Acid on Molecular Weight Determination of Polyesters: An in Situ NMR Investigation

Due to the poor solubility of aromatic polyesters in common organic solvents, trifluoroacetic acid is usually used as a co-solvent to increase their solubility for characterizations. However, only few works have reported the side reactions induced by it. We present here the application of in-situ 1H NMR techniques to explore its effect on the hydroxyl end-groups, which are usually used for the molecular weight determination of polyesters by end-group estimation method. Using bis(2-hydroxyethyl) terephthalate (BHET) as model compound, 1H quantitative NMR results show the peak integration of hydroxyethyl end-groups decreased with time via a pseudo-first-order kinetics in d-trifluoroacetic acid/d-chloroform mixture solvent (1:10 in volume). This is due to the esterification of hydroxyethyl groups with trifluoroacetic acid, revealed by the 1H-13C gradient-enhanced heteronuclear multiple bond correlation (gHMBC) spectrum. The mixtures of dimethyl terephthalate and BHET with different molar ratio were used to represent poly(ethylene terephthalate) (PET) with different degree of polymerization, and the effect of trifluoroacetic acid on the estimation of hydroxyethyl groups and subsequent molecular weight determination of polyesters was studied. Our results show that if a relative error of 5% is allowed, the NMR measurements must be finished within 1.3 h of solution preparation at 25 C in the mixture solvent. The results were confirmed in PET sample, while in poly(ethylene adipate), the obtained esterifaction constant is faster that those in aromatic system. The results can be applied to other polymer systems with alcohol functionalized groups, and used as a guideline for the characterization of polyesters and polyethers by end-group estimation method.

Epitaxial nucleation, modulated structure of molecular aggregation, and enhanced thermal degradation temperature of poly(ethylene adipate): Effects of the naturally occurring uracil as a nucleator

AbstractWe fabricated a novel bio‐composite using the poly(ethylene adipate) (PEA) and naturally occurring uracil (URA), in which the URA with the full biocompatibility and degradability acted as a nucleator (NA). A distinct enhancement was found in the crystallizability, melt‐crystallization temperature (Tc), and crystallization rate of the PEA upon incorporation of the URA, an indicative of a good NA of the URA. The underlying nucleation mechanism of the PEA is the epitaxial nucleation, attributed to the extremely good matching between the crystal lattice of the PEA and URA. The H‐bond interaction exists between the carbonyl/ester segment of the PEA crystalline phase and URA. With loading of the URA, both the carbonyl and ester fell behind the CH2 in the segmental reorganization in the crystallization process of the PEA. The PEA/1%URA showed an enhancement in the Td in the TG measurement (i.e. increased stability in thermal degradation), mainly attributed to the flame retardance effect of the URA.

Enhancement of Crystallization Behaviors in Quaternary Composites Containing Biodegradable Polymer by Supramolecular Inclusion Complex

Novel multi-component composites composed of the biodegradable polymer poly(ethylene adipate) (PEA), the water-soluble polymer poly(ethylene oxide) (PEO), poly(vinyl acetate) (PVAc), and a supramolecular-like inclusion complex (IC) made by α-cyclodextrin (α-CD) and poly(ε-caprolactone) (PCL) (coded as PCL–CD–IC) are discussed in this work. The PCL–CD–IC was used to increase the crystallization rate of the miscible PEA/PEO/PVAc ternary blend that crystalized slower than neat PEA. Higher resolution SEM and TEM images displayed that PCL–CD–IC did not assemble notably in the quaternary composites. For the results of isothermal crystallization, the analysis of the Avrami equation demonstrated that the rate constant k increased with the addition of PCL–CD–IC in the composites, suggesting that PCL–CD–IC provided more nucleation sites to promote the crystallization rate. The nucleation density increased with the addition of PCL–CD–IC, and the amount of spherulite also increased. Wide angle X-ray results showed that the composites displayed similar diffraction patterns to neat PEA, meaning PEO, PVAc, and PCL–CD–IC would not change the crystal structures of PEA in the composites. The PCL–CD–IC, the supramolecular nucleation agent, demonstrated its superior ability to enhance the multi-component composites of biodegradable polymer in this study.

Synthesis and property of polyurethane elastomer for biomedical applications based on nonaromatic isocyanates, polyesters, and ethylene glycol

Polyurethane (PU) elastomers were synthesized by the reaction of HDI or IPDI diisocyanates and poly(ε-caprolactone) (PCL or poly(ethylene adipate) (PA) diols and ethylene glycol as a polymer chain extender. IR, 1H, and 13C NMR spectroscopy and X-ray analysis were used for the structural analysis of the formed films. The molecular weight distribution was examined by GPC chromatography. Based on the measured contact angles, free surface energy parameters were calculated. The obtained results were analyzed for the possible use of these polyurethanes as biomaterials. The most promising in this respect was PU-3, which was synthesized from IPDI and PCL. This was due to its high molecular weight of approximately 90,000, the presence of a crystalline phase, and the relatively high hydrophobicity, with a SEP value below 25 mJ/m2. These films showed a good resistance to hydrolysis during incubation in Baxter physiological saline during 6 weeks. Both Gram-positive (Bacillus sp.) and Gram-negative (Pseudomonas sp.) types of bacterial strains were used to test the biodegradation property. Synthesized PUs are biodegradable and showed moderate or even mild cytotoxicity against human normal fibroblasts (BJ) and immortalized keratinocytes (HaCaT), estimated with direct contact assay. The most biocompatible was PU-3 film, which revealed rather mild reactivity against both cell lines, and the least was PU-2 film, synthesized from HDI and PA (severe toxicity for HaCaTs).

Unusual Ringed/Dendritic Sector Faces in Poly(butylene succinate) Crystallized with Isomeric Polymer

Poly(butylene succinate) (PBSu) and poly(ethylene adipate) (PEA), isomeric to each other, are mixed in a miscible state, and PBSu crystallized at Tc’s where PEA is kept at a molten state. PBSu upon...

Prediction of polyurethane behaviour via time-temperature superposition: Meanings and limitations

Two main issues are essential nowadays for practitioners in the field of polymeric materials: how a polymer will behave under dynamic loading conditions and for how long a polymer is reliable. In this sense, the time-temperature superposition principle was applied to the main viscoelastic properties (E′, E″ and tan δ) of a series of polyurethane coatings (PU-DEG-TMP) tested for mechatronic devices. Polyurethanes are derived from an ester glycol (poly(ethylene adipate) glycol), an aromatic diisocyanate (4,4′-dibenzyldiisocyanate) and di/trifunctional chain extenders - diethylene glycol (DEG) and trimethylol propane (TMP). Despite polyurethane intrinsic rheologic complexity, the moduli/loss factor curves superimpose well over several decades of reduced frequency at the glass transition temperature (Tg), 0 °C and 15 °C, the last temperature being considered the midpoint of the practical testing range. Three criteria were for checking the applicability of the time-temperature superposition: the Cole-Cole plot, the similarity between the aT calculated from both moduli (E′, E″) and the visual appearance of the final master curve. The presence of both hydrogen bonding and chemical joint points, along with some dangling chains put in a broader context the discussion of the microstructural features resulted from the application of the William-Landell-Ferry (WLF) equation.

Morphological analyses evidencing corrugate-grating lamellae assembly in banded spherulites of Poly(ethylene adipate)

The classical model of continuous helix-twist lamellae versus a novel corrugate-grating assembly in accounting for long-debated issues of periodic optical banding in poly(ethylene adipate) (PEA) polymer spherulites is critically assessed, by comparing and checking against a series of scientific evidence based on experimental data of scanning electron microscopy (SEM), ultrathin microbeam small-angle & wide-angle X-ray scattering (SAXS/WAXD), and optical microscopy. Analyses show that grating-structured model fits perfectly with all results. The novel proposition of grating-structured lamellae with a crossbar pitch fits perfectly with the experimental optical band spacing, and the interior morphology dissection is fully supported by the literature-reported microbeam X-ray data.