Ethylene Vinyl Alcohol Research Articles

Effectiveness Evaluation of Preventive Embolization of the Internal Iliac Artery in Preventing Type II Endoleaks.

Purpose The aim of this study was to evaluate the effectiveness of the proposed method of preventive embolization of the internal iliac arteries using a liquid tantalum-containing ethylene vinyl alcohol copolymer. Methods In this nonrandomized clinical study with a retrospective control group, 55 patients with aneurysmal lesions of the infrarenal abdominal aorta participated. In the course of this study, we developed and implemented a method of preventive embolization of the ostia of the internal iliac artery using a liquid tantalum containing ethylene-vinyl alcohol copolymer having viscosity of 34 centipoise. The method was applied in 27 cases in patients with aneurysmal lesions of the infrarenal abdominal aorta with unilateral involvement of the common iliac artery. The maximum follow-up period at the stage of publication of the results was 24 months. Results The proposed method of embolization of the internal iliac artery is accompanied by an absolute risk of developing type II endoleak 0.393 (95% confidence interval: 0.2120-0.5738, p = 0.029); therefore, when using the new technique, there is a decrease in the absolute risk of developing type II endoleak by 39.3%. Conclusion The proposed method of preventive embolization allows to perform reliable occlusion of the internal iliac artery as proximally as possible, which makes it possible to maintain distal blood flow in the internal iliac artery and minimizes the risks of ischemic events.

Successful retrieval of ethylene vinyl alcohol (EVOH) from the left middle cerebral artery during preoperative embolization of a juvenile nasopharyngeal angiofibroma (JNA).

Preoperative embolization of a juvenile nasopharyngeal angiofibroma (JNA) using ethyl vinyl alcohol (EVOH) is an effective adjunctive treatment prior to surgical resection. While liquid embolic agents are safe to use, we present a unique case involving the migration of EVOH into the left middle cerebral artery (MCA) through an external carotid artery-internal carotid artery (ECA-ICA) collateral during preoperative embolization using a dual-lumen balloon catheter. A 16-year-old male presented with left-sided nasal congestion, new nasal intonation in voice, and epistaxis. CT imaging showed a hypervascular mass centered within the left posterior nasal cavity and nasopharynx with expansion of the ipsilateral sphenopalatine foramen. A JNA was diagnosed, and preoperative embolization was performed prior to surgical resection. During the embolization procedure, EVOH migrated into the intracranial circulation through a hypertrophied ECA-ICA collateral. Angiography confirmed embolic material at the left MCA bifurcation. The embolic material was successfully removed using a balloon guide catheter and stentriever. This case is presented to highlight potential complications and rescue techniques used in the setting of non-target embolization occurring during JNA embolization.

Endovascular treatment simulations using a novel in vitro brain arteriovenous malformation model based on three-dimensional printing millifluidic technology.

Brain arteriovenous malformations (bAVM) are complex vascular diseases. Several models have been used to simulate endovascular treatments; thus in vitro models have not been widely employed because it has been difficult to recreate realistic phantoms of this disease. To describe the development and evaluate the preliminary experience of a novel bAVM in vitro model for endovascular embolization using millifluidic three-dimensional (3D) printing technology. We designed a bAVM phantom starting from simple to more complex designs, composed of a nidus, feeding arteries and draining vein. We recreate the design by using millifluidic technology with stereolithography 3D printing. Structural and functional tests were performed using angiographic images and computer flow dynamics. Treatment simulations with ethylene vinyl alcohol were tested using two different microcatheter position techniques. A Likert-scale questionnaire was applied to perform a qualitative evaluation of the model. We developed a realistic model of a bAVM with hollow channels. The structural evaluation showed a high precision of the 3D printing process. Embolization tests with the liquid agent gave similar sensations and material behaviour as in vivo cases. There were no significant differences between microcatheter position techniques, thus we observed a trend for better nidus filling with a deeper in-nidus position technique. We were able to create and test a novel bAVM in vitro model with stereolithography 3D printing in resin. It showed a high capacity for simulating endovascular embolization characteristics, with an excellent user experience. It could be potentially used for training and testing of bAVM embolizations.

The impact of storage temperature and packaging material on the quality of ultrasound treated sweet lime juice

The aim of this study is to examine the shelf life of ultrasound (US) treated sweet lime juice at 4, 15, 25, 30, and 35 °C and in two different packaging materials (coextruded ethylene vinyl alcohol copolymer [EVOH] and multi-layered polyethylene terephthalate [ML-PET] films). The US-treated sweet lime juice (0.7 W/cm3) was analyzed for the microbial count, enzyme activity, bioactive compounds degradation, and sensory attribute for a shelf-life of 37 days. Different packaging materials and storage temperatures had a significant effect (p < 0.05) on the microbial, enzyme inactivation, and biochemical attributes but had no significant influence (p > 0.05) on pH, acidity, and soluble solids in the samples. On a zeroth day, the US-treated sample showed an increase in bioactive compounds and vitamin C due to the increased cavitation effect. US-treated juice (0.7 W/cm3) retained 88.8% vitamin C and 100% antioxidants after 37 days of storage at 4 °C. Untreated and US-treated juice (0.7 W/cm3 at 0 day) got sensory scores of 8.1 and 7.5 out of 9 respectively. The juice stored in ML-PET had a better shelf life and nutrient retention than in the EVOH pouch. Interestingly, the sensory and vitamin C profile was above the allowable limit even after 37 days of storage. However, the microbiological count (>6 log cfu/mL) limited shelf life up to 37, 17, 11, 5, and 3 days, at 4, 15, 25, 30, and 35 °C for the juice packed in ML-PET pouch.

Recycling of a post-industrial printed multilayer plastic film containing polyurethane inks by solvent-targeted recovery and precipitation

The recently reported Solvent-Targeted Recovery And Precipitation (STRAP) strategy is used to deconstruct multilayer plastic packaging films into their constituent resins by selective polymer dissolution. To broaden the applicability of STRAP, we demonstrate the process with a flexible post-industrial printed multilayer plastic film used for food packaging. The material was a reverse printed film composed of polyethylene (PE), ethylene vinyl alcohol (EVOH), polyethylene terephthalate (PET), and polyurethane (PU)-based inks. Removal of all colors was observed with biomass-derived gamma-valerolactone (GVL) and the recovered polymers possessed comparable properties to the corresponding virgin resins. A technoeconomic analysis indicates that this STRAP process could be economically feasible at a processing capacity of 6,000 tons per year. Moreover, the production of plastic films with materials recovered by this STRAP process can have a lower climate change impact than the production of films from virgin polymers.

Fine adjustment of emission wavelength, light-conversion quality, photostability of blue-violet light conversion agents based on FRET effect

Single fluorescent chromophore is difficult to achieve efficient photoecological effect, meanwhile, the cost of light conversion agent should be more strictly controlled, thereby promoting the large-scale application of light conversion agricultural film. To solve the above problems, three carbazole derivatives CZ, TCZ and MCZ as donors of Förster resonance energy transfer, and the tris(carbazolyl) substituted triazine TPT as an acceptor of Förster resonance energy transfer, were designed and synthesized. Based on absorption and emission spectra, aggregation induced emission experiments, and light conversion quality tests, the best formulation of light conversion film are obtained. Among of them, TCZ@0.2TPT@EVAb and MCZ@0.2TPT@EVAb films (40% ethylene vinyl alcohol copolymer defined as EVAb film) show highest photosynthetic photon flux density at 400–500 nm, and matching fluorescence emission (458 nm and 461 nm). Under 20 h of intensified ultraviolet radiation (365 nm, 40 W), the emission intensity of TCZ@0.2TPT@EVAb and MCZ@0.2TPT@EVAb films can maintain over 94% of the initial value, showing excellent photostability. Compared with the blank EVAa/EVAb film, the transmittance of the doping films at 500–600 nm are up to 95.12%–99.64%, meaning excellent compatibility and dispersion of light conversion agent in doping films. It is worth mentioning that emission maxima of doping films can be continuously adjusted within the spectral range 430–480 nm, which is conducive to meet the photoecological needs of different crops. Finally, the doping films show low transmittance (1.78%–11.42%) at 200–350 nm, outlining excellent UV light conversion properties.

Diffusion and partitioning of different PFAS compounds through thermoplastic polyurethane and three different PVC-EIA liners

Perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorobutane sulfonic acid (PFBS), 6:2 fluorotelomer sulfonic acid (6:2 FTS), and GenX are tested for diffusion and sorption through thermoplastic polyurethane (TPU) and three ethylene interpolymer alloy (PVC-EIA) liners (EIA1, EIA2, and EIA3) with decreasing ketone ethylene ester (KEE) contents. The tests were conducted at room temperature (23 °C), 35 °C, and 50 °C. The tests show significant diffusion through the TPU as manifested by a decrease in the source concentration and an increase in the receptor concentrations of PFOA and PFOS over time, especially at higher temperatures. On the other hand, the PVC-EIA liners show excellent diffusive resistance to the PFAS compounds especially at 23 °C. At higher temperatures, the diffusion resistance of the PVC-EIA liner with the lowest KEE content, EIA3, was best at 50 °C followed by EIA1 (highest KEE content) and finally EIA2. Sorption tests showed no measurable partitioning of any of the compounds to the liners examined. Based on 535 days of diffusion testing, permeation coefficients are provided for all the compounds considered for the four liners at three temperatures. In addition, the Pg values for PFOA and PFOS are provided for a linear low density polyethylene (LLDPE) and a coextruded LLDPE - ethylene vinyl alcohol (EVOH) geomembrane based on 1246 to 1331 days of testing and are compared to those estimated for EIA1, EIA2, and EIA3.

Effect of nanocomposite pour point depressant EVAL/CNT on flow properties of waxy crude oil

The nanocomposite EVAL-CNT was produced by chemical grafting in the solution system through the esterification of ethylene-vinyl alcohol copolymer (EVAL) and carboxylated multi-walled carbon nanotubes (O-MWCNT), and its structural properties were characterized. The improvement of the rheological properties of the waxy oil system by the novel pour point depressant was investigated using macroscopic rheological measurements and microscopic observations. The results showed that EVAL-CNT nanocomposite pour point depressant (PPD) could significantly reduce the pour point and improve the low temperature fluidity of crude oil and had better performance than EVAL-GO at the same addition level. The best effect was achieved at the dosing concentration of 400 ppm, which reduced the pour point by 13 °C and the low-temperature viscosity by 85.4%. The nanocomposites dispersed in the oil phase influenced the precipitation and crystallization of wax molecules through heterogeneous crystallization templates, which led to the increase of wax crystal size and compact structure and changed the wax crystal morphology, which had a better effect on the rheological properties of waxy oil.

Safety, Efficacy and Mid-Term Outcome for Transarterial Embolization (TAE) of Renal Angiomyolipoma (AML) Using Ethylene Vinyl Alcohol Copolymer Liquid Embolic Agent (EVOH).

Transarterial embolization (TAE) of renal angiomyolipoma (AML) is effective in treating and preventing hemorrhage. We report our experience using EVOH with a single-center retrospective study of all AML embolized with EVOH between June 2013 and March 2022 at the Montpellier University Hospital. A total of 29 embolizations were carried out in 24 consecutive patients (mean age: 53.86 years; 21 women and 3 men) with 25 AMLs for severe bleeding, symptomatic AML, tumor size > 4 cm, or presence of aneurysm(s) > 5 mm. Data collected included imaging and clinical outcomes, tuberous sclerosis complex status, change in AML volume, rebleeding, renal function, volume and concentration of EVOH used, and complications. Out of 29 embolizations performed for 25 AMLs, four were performed in an emergency. Technical success was achieved for 24/25 AMLs. Mean AML volume reduction was 53.59% after a mean follow-up time of 446 days using MRI or CT scan. Aneurysms on angiogram and the symptomatological nature of AML, as well as secondary TAE and multiple arterial pedicles, were statistically associated (p < 0.05). Two patients (8%) underwent nephrectomy after TAE. Four patients had a second embolization. Minor and major complication rates were 12% and 8%, respectively. Neither rebleeding nor renal function impairment was noticed. TAE of AML using EVOH is, thus, highly effective and safe.

Structure and catalytic performance relationship of ionic liquids as recyclable alcoholysis catalysts for green preparation of ethylene‐vinyl alcohol copolymer

AbstractAlcoholysis is an important reaction for the current industrial production of ethylene‐vinyl alcohol (EVOH) copolymers. Herein, two series of ionic liquids (ILs), acidic and basic ones, were used as eco‐friendly catalysts for alcoholysis of ethylene‐vinyl acetate (EVA) copolymer. The effects of the reaction parameters (catalyst loading, n(CH3OH)/n(Ac) and reaction time), EVA composition, and nitrogen flow on the alcoholysis were systematically investigated. A nearly 100% of alcoholysis degree was achieved using acidic ILs ([BHSO3MIm][HSO4]) under the optimum conditions (3.0 mol% catalyst loading relative to the VA units in EVA, n(CH3OH)/n(Ac) = 30, 70°C, 6 h). Moreover, [BHSO3MIm][HSO4] could be reused at least five times without the decrease of catalytic activity, showing excellent recyclability. The interactions between IL and the substrate methanol and the model compound ethyl acetate were investigated by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance techniques, and on the basis of these results, the plausible mechanisms of acidic and basic ILs catalyzed alcoholysis of EVA were proposed.

Oxidation stability of N-ethyl-2-pyrrolidinone under high voltage environments

This work was aimed at investigating the electrochemical oxidation behavior of poly(vinylpyrrolidone) (PVP, a popular dispersant in the process of battery production) under high voltage environments. N-ethyl-2-pyrrolidone (NEP) was selected as a compound representative of PVP. Working electrodes were designed and prepared with a mixture of NEP and ethylene vinyl alcohol (EVOH) as a vehicle, and conductive carbon black as the electron transport material. Linear sweep voltammetry (LSV) was used to monitor the reactions underwent by NEP. The oxidative products were analyzed with X-ray photoelectron spectroscopy (XPS) and gas chromatography coupled with mass spectrometry (GC–MS). LSV revealed electrochemical oxidation of NEP taking place at voltages higher than 4 V. XPS and GC–MS revealed that the electrochemical oxidative products contained an ammonium group derived from the loss of electrons of the NEP under the electric field. Two types of ammonium species were identified: (i) species resulting from the loss of four electrons followed by hydrolysis and; (ii) species of higher molecular weight as a result of the replacement of ethyl group on NEP with methoxy (from lithium methoxide) followed by loss of protons and electrons (two-electron-two-proton process) with hydrogen being exchanged with fluorine. A reasonable mechanism was proposed to explain these results.

The Effect of Vacuum Films on Physicochemical and Microbiological Characteristics of Hanwoo (Korean Native Cattle).

The objective of this study was to investigate the physicochemical and microbiological characteristics of round of Hanwoo by vacuum packaging film materials, polyvinylidene chloride (PVDC) and ethylene vinyl alcohol (EVOH). The packaged beef samples were stored in refrigerated conditions (2±1°C) for 12 weeks. Physicochemical analysis with pH, surface color, thiobarbituric acid reactive substances (TBARS) values, and volatile basic nitrogen (VBN) values and microbiological analysis with aerobic plate count (APC) and metagenomic analysis of packaged beef samples were performed. The pH and surface color did not change substantially during the 12 weeks and EVOH-packaged beef tended to be lower than those of PVDC-packaged beef. PVDC- and EVOH-packaged samples showed low TBARS and VBN values below standard limits. APC did not exceed 7 Log CFU/g for both samples during storage. In metagenomic analysis, Firmicutes and Lactobacillaceae were dominant phylum and family of the PVDC- and EVOH-packaged beef. In both packaged samples, Dellaglioa algida was the dominant species during storage, with the notable difference being the presence of Lactococcus piscium. Therefore, this study provided the information on the quality of vacuum-packaged beef according to different vacuum films for long-term refrigerated storage.

Preoperative percutaneous Onyx embolization of carotid body paragangliomas with balloon test occlusion.

The study aims to analyze our first experience with direct percutaneous embolization of carotid body tumors (CBTs) using ethylene-vinyl alcohol copolymer (Onyx) along with balloon test occlusion (BTO). A retrospective preliminary single-center study was conducted at the Otorhinolaryngology and Head and Neck Surgery Department and the Medical Imaging Department of the University Teaching Hospital. A consecutive series of three patients with CBTs was treated at the local institution between October 2018 and June 2019. All three patients underwent preoperative percutaneous embolization using ethylene-vinyl alcohol copolymer (Onyx 18) with the addition of BTO. Outcome measures were the percentage of tumor devascularization, intraoperative blood losses, and operation times. BTO was evaluated by clinical neurological examination and neurosonological transcranial Doppler examination of the middle cerebral artery (MCA). Devascularization of all three tumors was complete or near complete. All three tumors were surgically extirpated with excellent surgical outcomes. The blood losses were minimal, and the average operation time was 2 h and 8 min. BTO was positive in one patient, which was valuable additional information on carotid branches ligation limitations. The other two patients showed negative BTOs with the result of safety of eventual carotid arteries ligations. Preoperative direct percutaneous embolization of CBT with Onyx is a highly effective procedure that significantly facilitates surgery. BTO provides valuable additional information on the most appropriate and safe surgical approach.

Cation exchange chromatography membrane of Poly(ethylene vinyl alcohol) nanofiber/sulfonated polystyrene microsphere composite for lysozyme isolation

Lysozyme, as widely used bacteriostatic enzyme, the rapid and low-cost isolation of lysozyme with high purity was the basis and premise of its application. In this work, a facile approach of spray coating was proposed to engineer composite membranes consisted of sulfonated polystyrene microspheres and poly(ethylene vinyl alcohol) nanofibers. The sulfonic acid groups offer strong interaction between the ligand and lysozyme, endowing high lysozyme adsorption capacity. And simultaneously, the porous channels of nanofibrous membranes guarantee high water flux. The FTIR and XPS results indicate the incorporation of sulfonated polystyrene spheres. The EVOH/SPS composite membranes exhibit both high water permeability and lysozyme adsorption capacity. Importantly, the constructed chromatography columns possess high performance of water flux with 9172 L h−1 m−2, and excellent adsorption capacity at static and dynamic state, revealing enormous potential for application.

Use of Ethylene Vinyl Copolymer for Embolization Outside the Central Nervous System: A Case Review.

Onyx (ethylene vinyl copolymer; Medtronic, Minneapolis, MN) is a nonadhesive, nonabsorbable, permanent liquid embolic agent. It is Food and Drug Administration (FDA) approved for preoperative embolization of brain arteriovenous malformations (AVMs). Onyx is composed of an ethylene vinyl alcohol (EVOH) copolymer, dimethyl sulfoxide (DMSO), and micronized tantalum powder. Each substance plays a vital part in the overall effectiveness and delivery at embolization. EVOH is the embolic component and DMSO facilitates delivery through the catheter by acting as a solvent. Micronized tantalum powder allows radiographic visualization. Onyx is available in two concentrations: Onyx 18 (6% EVOH) and Onyx 34 (8% EVOH). Onyx 18 has lower viscosity which allows for greater downstream flow from the delivery microcatheter.

Potassium permanganate-based ethylene gas indicator of kiwifruit ripeness

A kiwifruit ripeness indicator was developed using potassium permanganate (KMnO4), an ethylene gas scavenger. A total of 500 g of kiwifruit was packaged in polypropylene (PP) containers (20 × 16 × 11.5 cm) with a heat-sealed PP, polyethylene (PE), and ethylene-vinyl alcohol copolymer (EVOH) cover film (50 µm thick) with the indicator inside, and stored at 15, 20, and 25 °C. The ethylene gas permeability of the cover films, kiwifruit firmness (ripeness parameter, ≤ 8 N), ethylene gas concentration, and indicator color were measured. The indicator changed from purple to brown. When the firmness reached 7.9 N, the ethylene gas concentrations for each cover film were different due to film permeability. The indicator color index (ΔE) for each cover film was also different and ranged from 15.2 to 23.9, falling within the visually detectable change.

Morphological evolution ofTMB‐5/ethylene–vinyl alcohol copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene

AbstractThe morphological evolution of TMB‐5/ethylene–vinyl alcohol (EVOH) copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene (iPP) were investigated. iPP/TMB‐5/EVOH ternary blends with TBM‐5 selectively distributed in the EVOH phase were prepared through a multistage stretching extrusion, which combined an assembly of layer multiplying elements (LMEs) with an extruder. Scanning electron microscopy revealed that the biaxial‐stretching field in LMEs transformed the TMB‐5/EVOH phase into platelets along the extrusion direction. Differential scanning calorimetry and X‐ray diffraction results indicated that the TMB‐5 particles were distributed in the EVOH phase and noβcrystals formed in as‐extruded samples. Especially, the TMB‐5 was released from the EVOH phase into iPP in the annealing process and induced the formation ofβcrystals. Compared with that of pure iPP, the oxygen permeability coefficient of iPP containing aligned TMB‐5/EVOH platelets decreased more than three times. The enhanced barrier properties resulted from the increased tortuosity of the diffusion pathway caused by the orientated high‐aspect‐ratio platelets. © 2023 Society of Industrial Chemistry.

Abstract Number ‐ 97: Middle meningeal artery embolization to treat chronic subdural hematomas – Retrospective study of morphological parameters

Introduction Chronic subdural hematomas are a common neurovascular condition that involve the gradual and continual exudation of fluid from a compromised cell layer lining the dura [1]. Embolization of the middle meningeal artery (MMAE) results in lower recurrence rates as compared to traditional surgical burr hole evacuation [2‐4]. Liquid embolic agents such as cyanoacrylates or ethylene vinyl alcohol copolymers can potentially provide a distinct advantage with greater distal penetration resulting in faster hematoma resolution [5]. Their inherent radiopacity (after pre‐mixing) also allows for accurate visualization and control over embolization. The hypothesis of this study is that liquid embolic surface area would correlate with more effective cSDH volume resolution in patients. Methods Under IRB approval, we retrospectively analyzed non‐contrast head CTs and immediate post‐embolization flat‐detector CTs from 45 patients who underwent first‐line MMAE with a liquid embolic. Patients who received any neurosurgical intervention were excluded. 3D‐Slicer was used to segment and calculate hematoma volumes pre‐embolization, as well as at 1‐month, 3‐months, and 6‐months post‐embolization. The flat‐detector CT scans were also segmented to calculate the surface area of the liquid embolic. Results There was significant reduction in hematoma volume at 1‐, 3‐ and 6‐months with respect to the preoperative cSDH volume (Figure A, Pre: pre‐treatment, mo: month). The liquid embolic surface area significantly correlated with (a) pre‐embolization hematoma volume (R2 = 0.27, p = 0.0002, n = 45), (b) the reduction in volume at 1‐month post‐embolization (R2 = 0.16, p = 0.007, n = 41), (c) volume reduction at 3‐months post‐embolization (R2 = 0.29, p = 0.0015, n = 32), (d) hematoma volume resorption rate (cc/day) calculated at 1‐month post‐embolization (R2 = 0.16, p = 0.011, n = 39), and (e) hematoma volume resorption rate calculated at 3‐months post‐embolization (R2 = 0.34, p = 0.0003, n = 34, Figure B). The liquid embolic surface area was not correlated to the volume reduction at 6‐months (p = 0.3, n = 26). Conclusions The luminal surface area of MMA vasculature embolized with liquid embolics may be correlated to the reduction in cSDH volumes. The liquid embolic segmentation method used here needs further refinement to improve accuracy. Additional data sets are required to confirm the correlations reported here.

EMBOLIZATION OF THE INTERNAL ILIAC ARTERY USING LIQUID EMBOLYZING SYSTEMS

Among the complications of endovascular abdominal aortic aneurysm repair the most common are the so–called endoleaks - the preservation of blood flow inside an isolated aneurysmal sac. This complication occurs in almost every fourth patient and is the main cause of reinterventions, which makes the late development of this complication one of the urgent problems under discussions. The report presents a clinical case of treatment of a patient with an aneurysm of the infrarenal abdominal aorta with its spread to the common iliac artery using the technique of preventive embolization of the internal iliac artery with application of a liquid tantalum-containing ethylene vinyl alcohol copolymer. All stages of the operation were performed in the catheterization laboratory using a stationary angiographic system. The embolizing material was introduced after implantation of the stent-graft into the target position, through a microcatheter pre-installed at the ostium of the embolizing internal iliac artery. The introduction of a tantalum-containing ethylene vinyl alcohol copolymer after the installation of the stentgraft, under conditions of significant reduction of arterial antegrade blood flow in the lumen of the internal iliac artery, allowed to create a reliable occlusion of the ostium segment of the artery, reduced the risk of migration of embolizing substance into the distal arterial bed.

Regiospecific Poly(ethylene-co-vinyl alcohol) by ROMP of 3-Acetoxycyclooctene and Postpolymerization Modification for Barrier Material Applications

Ethylene vinyl alcohol (EVOH) is an oxygen barrier polymer used to prevent premature degradation of food, pharmaceuticals, and other products due to its semicrystallinity, strong intermolecular interactions, and consequently low free volume. EVOH is made using traditional free-radical copolymerization, which leads to little structural regularity. We utilized ring-opening metathesis polymerization (ROMP) to determine how regioregularity impacts the barrier properties of EVOH-related materials. A regioregular (head-to-tail) polymer was synthesized from ROMP of 3-acetoxycyclooctene, followed by hydrogenation and deacylation to give a linear, highly regioregular EVOH (PH3OHCOE) containing the equivalent of 75 mol % ethylene units. The same process was carried out with 5-acetoxycyclooctene, but the resulting polymer (PH5OHCOE) is regiorandom. Both polymers were compared to an industry benchmark, EVOH-44, containing 44 mol % ethylene units. After processing, differential scanning calorimetry showed that the semicrystalline PH3OHCOE had a higher melting temperature and enthalpy of melting compared to semicrystalline PH5OHCOE, indicating that PH3OHCOE is more crystalline. This was confirmed by wide-angle X-ray scattering (WAXS). WAXS, rheological studies, and polarized optical microscopy showed that PH3OHCOE has a more well-defined crystal structure, a higher degree of hydrogen-bonding between −OH groups, and a higher glass transition temperature compared to PH5OHCOE. These differences were also highlighted in their tensile behavior, where PH3OHCOE and EVOH-44 exhibited brittle failure compared to the ductile behavior observed for PH5OHCOE. Oxygen barrier testing demonstrated that regioregular PH3OHCOE had an oxygen permeability more than a factor of 3 lower than regiorandom PH5OHCOE but still higher than EVOH-44, while water barrier testing showed that PH3OHCOE had the lowest water permeability, more than 6 times lower than EVOH-44. These results highlight the importance of regioregularity on the barrier properties of EVOH-like materials and show that structural regularity can lower oxygen permeability while maintaining low water permeability at the low vinyl alcohol content.