The Experts below are selected from a list of 25377 Experts worldwide ranked by ideXlab platform
Niranjan Karak - One of the best experts on this subject based on the ideXlab platform.
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biobased multifunctional macroglycol containing smart thermoplastic hyperbranched polyurethane elastomer with intrinsic self healing attribute
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Tuhin Ghosh, Niranjan KarakAbstract:Smart biobased self-healable polymers are advanced sustainable materials. Thus, a thermoplastic hyperbranched polyurethane (HBPUR) elastomer was synthesized by using a biobased multifunctional macroglycol along with other required components, for the first time. This biobased macroglycol was obtained by stoichiometric controlled esterification reaction of Dimer Acid with glycerol. Fourier transform infrared, nuclear magnetic resonance spectroscopic, gel permeation chromatography, and X-ray diffraction studies confirmed the physicochemical structure of the synthesized macroglycol and HBPURs. The degree of branching value (0.78–0.91) of HBPURs varies with this macroglycol content. These thermoplastic PUR elastomers exhibited outstanding toughness (205 MJ.m–³), unprecedented high elongation at break (2810–3160%), good tensile strength (8.2–9.5 MPa), impact resistance (>17.3 kJ/m), scratch resistance (4.0–4.5 kg), durometer hardness (52–60 Shore A), adhesive strength (3.3–6.7 kPa), thermostability (241–249 °C), and chemical and UV-resistance. Notably, HBPURs also showed excellent repeatable intrinsic self-healing efficiency (100%) under exposure of microwave (450 W). Moreover, HBPURs exhibited outstanding thermoresponsive shape recovery (100%) within 50–56 s at 60 °C. In addition, HBPURs showed acceptable biodegradation under the exposure of Pseudomonus aeruginosa and Bacillus subtilus bacterial strains. Again, HBPUR demonstrated superior performance over linear analogous PUR. Thus, HBPUR has great potential as a smart sustainable self-healing thermoplastic elastomer for different applications.
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Environmentally Friendly Polyurethane Dispersion Derived from Dimer Acid and Citric Acid
2018Co-Authors: Soumen Chandra, Niranjan KarakAbstract:Sustainable polyurethane dispersion with smart properties has enormous potential in the polymer industries because of its unique and environmentally friendly characteristics. Biodegradable water dispersion thermoplastic polyurethanes (WBPUs) with self-healing capability were synthesized, and they were water-dispersible after neutralization with triethylamine (TEA). The biobased macroglycol and chain extender were synthesized via the catalyst-based esterification reactions of Dimer Acid (DA), poly(ethylene glycol) (PEG-200), citric Acid (CA), and glycerol. Three different compositions of WBPUs were synthesized by reacting poly(ε-caprolactone) diol (PCL, M.W ∼ 2000 g/mol) and biobased macroglycol with aliphatic and aromatic diisocyanates in the presence of various amounts of branch generating unit. FT-IR, 1HNMR, 13CNMR, GPC, and XRD analyses of WBPUs were conducted to study the physicochemical structure, crystallinity, and molecular weight. The WBPUs exhibited high elongation at break (678.9–485.3%), toughness (51.49–32.6MJ m–3), tensile strength (9.26–7.82 MPa), scratch hardness (3.5–2 kg), gloss at 60° (25.4–15.6°), impact resistance (8.95–8.33 kJ/m), and chemical resistance. Furthermore, these WBPUs possessed microwave assisted self-healing and UV-aging characteristics, and they were found to be biodegradable
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Biobased Multifunctional Macroglycol Containing Smart Thermoplastic Hyperbranched Polyurethane Elastomer with Intrinsic Self-Healing Attribute
2018Co-Authors: Tuhin Ghosh, Niranjan KarakAbstract:Smart biobased self-healable polymers are advanced sustainable materials. Thus, a thermoplastic hyperbranched polyurethane (HBPUR) elastomer was synthesized by using a biobased multifunctional macroglycol along with other required components, for the first time. This biobased macroglycol was obtained by stoichiometric controlled esterification reaction of Dimer Acid with glycerol. Fourier transform infrared, nuclear magnetic resonance spectroscopic, gel permeation chromatography, and X-ray diffraction studies confirmed the physicochemical structure of the synthesized macroglycol and HBPURs. The degree of branching value (0.78–0.91) of HBPURs varies with this macroglycol content. These thermoplastic PUR elastomers exhibited outstanding toughness (205 MJ.m–3), unprecedented high elongation at break (2810–3160%), good tensile strength (8.2–9.5 MPa), impact resistance (>17.3 kJ/m), scratch resistance (4.0–4.5 kg), durometer hardness (52–60 Shore A), adhesive strength (3.3–6.7 kPa), thermostability (241–249 °C), and chemical and UV-resistance. Notably, HBPURs also showed excellent repeatable intrinsic self-healing efficiency (100%) under exposure of microwave (450 W). Moreover, HBPURs exhibited outstanding thermoresponsive shape recovery (100%) within 50–56 s at 60 °C. In addition, HBPURs showed acceptable biodegradation under the exposure of Pseudomonus aeruginosa and Bacillus subtilus bacterial strains. Again, HBPUR demonstrated superior performance over linear analogous PUR. Thus, HBPUR has great potential as a smart sustainable self-healing thermoplastic elastomer for different applications
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Dimer Acid based waterborne hyperbranched poly ester amide thermoset as a sustainable coating material
Progress in Organic Coatings, 2017Co-Authors: Gaurav Gogoi, Satyabrat Gogoi, Niranjan KarakAbstract:Abstract A Dimer Acid based waterborne hyperbranched poly(ester amide) (WHPEA) was successfully synthesized via a self-catalyzed and solvent free polycondensation reaction by using a novel citric Acid derived polyamide polyol as branching unit and phthalic anhydride as the dibasic moiety. Citric Acid acted as a bio-based internal emulsifier which was neutralized by adding triethylamine to obtain the waterborne polymeric system. Four different polymers were obtained by varying the mole composition of phthalic anhydride and Dimer Acid in between 4:1 and 1:4. The synthesized WHPEA was characterized by FTIR and NMR analyses. The mechanical performance of epoxy cured WHPEA was studied and compared to the analogues thermoset prepared without using neutralizing agent (HPEA). The result showed better mechanical performance of the later than the former. However, WHPEA exhibited better chemical resistance (except in alkali) and more thermal stability compared to HPEA. Bacterial degradation study with strain of P. aeruginosa revealed better degradation of WHPEA in comparison to HPEA thermosets. Thus, waterborne system was developed as an environmentally benign and sustainable polymeric material, which can be utilized as low VOC containing coating material. The work demonstrated the use of citric Acid and Dimer Acid as a combined bio-based component in the synthesis of WHPEA coating for the first time.
Nicoleta Ilie - One of the best experts on this subject based on the ideXlab platform.
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degree of conversion of nano hybrid resin based composites with novel and conventional matrix formulation
Clinical Oral Investigations, 2013Co-Authors: Karina E Frauscher, Nicoleta IlieAbstract:Objectives This study aimed to determine the degree of conversion (DC) of two nano-hybrid resin-based composites (RBCs) with novel monomer composition based on Dimer Acid derivates (hydrogenated Dimer Acid) and tricyclodecane–urethane structure compared to three nano-hybrid materials containing conventional matrices. DC was evaluated at 0.1, 2, and 6 mm depth at varying irradiation times (10, 20, and 40 s) and layering techniques (bulk and incremental).
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depth of cure and mechanical properties of nano hybrid resin based composites with novel and conventional matrix formulation
Clinical Oral Investigations, 2012Co-Authors: Karina E Frauscher, Nicoleta IlieAbstract:Objectives This study’s purpose was to evaluate the depth of cure (DOC) and the variation of mechanical properties with depth of two nano-hybrid resin-based composites (RBCs) containing a novel monomer composition based on Dimer-Acid derivatives (h-Da) or rather tricyclodecane–urethane structure (TCD-urethane) compared to three conventionally formulated nano-hybrid RBCs based on hardness-profile measurements.
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depth of cure and mechanical properties of nano hybrid resin based composites with novel and conventional matrix formulation
Clinical Oral Investigations, 2012Co-Authors: Karina E Frauscher, Nicoleta IlieAbstract:This study’s purpose was to evaluate the depth of cure (DOC) and the variation of mechanical properties with depth of two nano-hybrid resin-based composites (RBCs) containing a novel monomer composition based on Dimer-Acid derivatives (h-Da) or rather tricyclodecane–urethane structure (TCD-urethane) compared to three conventionally formulated nano-hybrid RBCs based on hardness-profile measurements. Specimens were produced through different layering techniques (bulk, incremental) and curing times (10, 20, and 40 s). Mechanical properties (Vickers hardness (HV), modulus of elasticity (E)) were evaluated every 100 μm longitudinally throughout the bisected samples using an automatic micro-hardness indenter. DOC was determined as the depth at which the 80% hardness cutoff value in relation to the surface hardness was reached. Results were compared using one- and multiple-way ANOVA, Tukey HSD post-hoc test (α = 0.05) and partial eta-squared statistic. Increasing curing time resulted in a significant increase in DOC. Generally, the novel-formulated materials showed higher DOC values. “Curing time” and “material” showed the strongest effect on DOC. Starting in 4 mm depth, significantly higher HV and E was reached for incremental compared to bulk-curing technique. Values in 0.1 and 2 mm depth (bulk, incremental) as well as in 4 mm depth (incremental) were independent from curing time, while in greater depths, values generally increased with curing time. “Filling technique” and “material” performed the strongest influence on mechanical properties. Within the limits of this study, the novel-formulated RBCs showed better performance concerning DOC compared to conventional materials. For cavities deeper than 3 mm, all tested materials should be placed incrementally to ensure adequate polymerization. In large cavities (≥6 mm), the lowest increment should be cured at least 40 s. The novel-formulated RBCs might be cured in comparatively bigger increments.
Mark J Strynar - One of the best experts on this subject based on the ideXlab platform.
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hexafluoropropylene oxide Dimer Acid hfpo da or genx alters maternal and fetal glucose and lipid metabolism and produces neonatal mortality low birthweight and hepatomegaly in the sprague dawley rat
Environment International, 2021Co-Authors: Justin M Conley, James Mccord, Mark J Strynar, Christy S Lambright, Nicola Evans, Donna Hill, Elizabeth Medlockkakaley, Vickie S Wilson, Earl L GrayAbstract:Abstract Hexafluoropropylene oxide Dimer Acid (HFPO-DA or GenX) is an industrial replacement for the straight-chain perfluoroalkyl substance (PFAS), perfluorooctanoic Acid (PFOA). Previously we reported maternal, fetal, and postnatal effects from gestation day (GD) 14-18 oral dosing in Sprague-Dawley rats. Here, we further evaluated the perinatal toxicity of HFPO-DA by orally dosing rat dams with 1–125 mg/kg/d (n = 4 litters per dose) from GD17-21 and with 10–250 mg/kg/d (n = 5) from GD8 – postnatal day (PND) 2. Effects of GD17-21 dosing were similar to those previously reported for GD14-18 dosing and included increased maternal liver weight, altered maternal serum lipid and thyroid hormone concentrations, and altered expression of peroxisome proliferator-activated receptor (PPAR) pathway genes in maternal and fetal livers. Dosing from GD8-PND2 produced similar effects as well as dose-responsive decreased pup birth weight (≥30 mg/kg), increased neonatal mortality (≥62.5 mg/kg), and increased pup liver weight (≥10 mg/kg). Histopathological evaluation of newborn pup livers indicated a marked reduction in glycogen stores and pups were hypoglycemic at birth. Quantitative gene expression analyses of F1 livers revealed significant alterations in genes related to glucose metabolism at birth and on GD21. Maternal serum and liver HFPO-DA concentrations were similar between dosing intervals, indicating rapid clearance, however dams dosed GD8 – PND2 had greater liver weight and gestational weight gain effects at lower doses than GD17-21 dosing, indicating the importance of exposure duration. Comparison of neonatal mortality dose–response curves between HFPO-DA and previously published perfluorooctane sulfonate (PFOS) data indicated that, based on serum concentration, the potency of these two PFAS are similar in the rat. Overall, HFPO-DA is a developmental toxicant in the rat and the spectrum of adverse effects is consistent with prior PFAS toxicity evaluations, such as PFOS and PFOA.
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evidence of air dispersion hfpo da and pfoa in ohio and west virginia surface water and soil near a fluoropolymer production facility
Environmental Science & Technology, 2020Co-Authors: Jason E Galloway, Mark J Strynar, Anjelica V P Moreno, Andrew A May, Andrew B. Lindstrom, Seth Newton, Linda K WeaversAbstract:Perfluorooctanoic Acid (PFOA) was used as a fluoropolymer manufacturing aid at a fluoropolymer production facility in Parkersburg, WV from 1951 to 2013. The manufacturer introduced a replacement surfactant hexafluoropropylene oxide Dimer Acid (HFPO-DA) that has been in use at this site since 2013. Historical releases of PFOA and related epidemiological work in this area has been primarily focused on communities downstream. To provide an update on the ongoing impacts from this plant, 94 surface water samples and 13 soil samples were collected mainly upstream and downwind of this facility. PFOA was detected in every surface water sample with concentrations exceeding 1000 ng/L at 13 sample sites within an 8 km radius of the plant. HFPO-DA was also found to be widespread with the highest levels (>100 ng/L) found in surface water up to 6.4 km north of the plant. One sample site, 28 km north of the plant, had PFOA at 143 ng/L and HFPO-DA at 42 ng/L. Sites adjacent to landfills containing fluorochemical waste had PFOA concentrations ranging up to >1000 ng/L. These data indicate that downwind atmospheric transport of both compounds has occurred and that the boundaries of the impact zone have yet to be fully delineated.
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elevated levels of per and polyfluoroalkyl substances in cape fear river striped bass morone saxatilis are associated with biomarkers of altered immune and liver function
Environment International, 2020Co-Authors: T C Guillette, James Mccord, Matthew P Guillette, M E Polera, Kyle T Rachels, Clint Morgeson, Nadine Kotlarz, Detlef R U Knappe, Benjamin J Reading, Mark J StrynarAbstract:Abstract Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals of concern that persist in the environment. Environmental monitoring revealed high concentrations of hexafluoropropylene oxide Dimer Acid (HFPO-DA) and other novel PFAS in the lower Cape Fear River; however, there is limited information on PFAS exposures and effects of this contamination on aquatic biota. Serum concentrations of 23 PFAS in Striped Bass (Morone saxatilis) from the Cape Fear River (n = 58) and a reference population from an aquaculture laboratory on the Pamlico/Tar watershed (n = 29) were quantified using liquid chromatography and high-resolution mass spectrometry, and correlations between PFAS concentrations and health-related serum biomarkers were evaluated. Perfluorooctane sulfonate, the predominant PFAS in Cape Fear River Striped Bass serum, was detectable in every sample with serum concentrations reaching 977 ng/mL. Perfluorononanoic and perfluorodecanoic Acid were also detected in all samples, with perfluorohexanesulfonic Acid present in >98% of the samples. HFPO-DA (range
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evaluation of maternal embryo and placental effects in cd 1 mice following gestational exposure to perfluorooctanoic Acid pfoa or hexafluoropropylene oxide Dimer Acid hfpo da or genx
Environmental Health Perspectives, 2020Co-Authors: Bevin E Blake, Harlie A Cope, Samantha M Hall, Robert D Keys, Beth W Mahler, James Mccord, Brittany Scott, Heather M Stapleton, Mark J StrynarAbstract:Background: Perfluorooctanoic Acid (PFOA) is a poly- and perfluoroalkyl substance (PFAS) associated with adverse pregnancy outcomes in mice and humans, but little is known regarding one of its repl...
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Gas-Phase Detection of Fluorotelomer Alcohols and Other Oxygenated Per- and Polyfluoroalkyl Substances by Chemical Ionization Mass Spectrometry
2019Co-Authors: Theran P. Riedel, Mark J Strynar, Johnsie R. Lang, Andrew B. Lindstrom, John H. OffenbergAbstract:Per- and polyfluoroalkyl substances (PFAS) are incorporated into an ever-increasing number of modern products and inevitably enter the environment and ultimately human bodies. Herein, we show that chemical ionization mass spectrometry with iodide reagent ion chemistry is a useful technique for the detection of fluorotelomer alcohols (FTOHs) and other oxygenated PFAS, including per- and polyfluoro carboxylic Acids such as hexafluoropropylene oxide Dimer Acid. This technique offers direct, high-time resolution measurement capability with parts per trillion by volume (nanograms per cubic meter) gas-phase detection limits. Measurements were taken by direct volatilization of samples without prior processing, allowing for fast measurements and reduced sample treatment compared to established PFAS methods. We demonstrate the utility of this technique by sampling volatile and semivolatile PFAS from fluoro additives and fluoro products to quantify levels of FTOHs and identify additional fluorinated compounds for which standards were unavailable
Karina E Frauscher - One of the best experts on this subject based on the ideXlab platform.
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degree of conversion of nano hybrid resin based composites with novel and conventional matrix formulation
Clinical Oral Investigations, 2013Co-Authors: Karina E Frauscher, Nicoleta IlieAbstract:Objectives This study aimed to determine the degree of conversion (DC) of two nano-hybrid resin-based composites (RBCs) with novel monomer composition based on Dimer Acid derivates (hydrogenated Dimer Acid) and tricyclodecane–urethane structure compared to three nano-hybrid materials containing conventional matrices. DC was evaluated at 0.1, 2, and 6 mm depth at varying irradiation times (10, 20, and 40 s) and layering techniques (bulk and incremental).
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depth of cure and mechanical properties of nano hybrid resin based composites with novel and conventional matrix formulation
Clinical Oral Investigations, 2012Co-Authors: Karina E Frauscher, Nicoleta IlieAbstract:Objectives This study’s purpose was to evaluate the depth of cure (DOC) and the variation of mechanical properties with depth of two nano-hybrid resin-based composites (RBCs) containing a novel monomer composition based on Dimer-Acid derivatives (h-Da) or rather tricyclodecane–urethane structure (TCD-urethane) compared to three conventionally formulated nano-hybrid RBCs based on hardness-profile measurements.
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depth of cure and mechanical properties of nano hybrid resin based composites with novel and conventional matrix formulation
Clinical Oral Investigations, 2012Co-Authors: Karina E Frauscher, Nicoleta IlieAbstract:This study’s purpose was to evaluate the depth of cure (DOC) and the variation of mechanical properties with depth of two nano-hybrid resin-based composites (RBCs) containing a novel monomer composition based on Dimer-Acid derivatives (h-Da) or rather tricyclodecane–urethane structure (TCD-urethane) compared to three conventionally formulated nano-hybrid RBCs based on hardness-profile measurements. Specimens were produced through different layering techniques (bulk, incremental) and curing times (10, 20, and 40 s). Mechanical properties (Vickers hardness (HV), modulus of elasticity (E)) were evaluated every 100 μm longitudinally throughout the bisected samples using an automatic micro-hardness indenter. DOC was determined as the depth at which the 80% hardness cutoff value in relation to the surface hardness was reached. Results were compared using one- and multiple-way ANOVA, Tukey HSD post-hoc test (α = 0.05) and partial eta-squared statistic. Increasing curing time resulted in a significant increase in DOC. Generally, the novel-formulated materials showed higher DOC values. “Curing time” and “material” showed the strongest effect on DOC. Starting in 4 mm depth, significantly higher HV and E was reached for incremental compared to bulk-curing technique. Values in 0.1 and 2 mm depth (bulk, incremental) as well as in 4 mm depth (incremental) were independent from curing time, while in greater depths, values generally increased with curing time. “Filling technique” and “material” performed the strongest influence on mechanical properties. Within the limits of this study, the novel-formulated RBCs showed better performance concerning DOC compared to conventional materials. For cavities deeper than 3 mm, all tested materials should be placed incrementally to ensure adequate polymerization. In large cavities (≥6 mm), the lowest increment should be cured at least 40 s. The novel-formulated RBCs might be cured in comparatively bigger increments.
Tuhin Ghosh - One of the best experts on this subject based on the ideXlab platform.
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biobased multifunctional macroglycol containing smart thermoplastic hyperbranched polyurethane elastomer with intrinsic self healing attribute
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Tuhin Ghosh, Niranjan KarakAbstract:Smart biobased self-healable polymers are advanced sustainable materials. Thus, a thermoplastic hyperbranched polyurethane (HBPUR) elastomer was synthesized by using a biobased multifunctional macroglycol along with other required components, for the first time. This biobased macroglycol was obtained by stoichiometric controlled esterification reaction of Dimer Acid with glycerol. Fourier transform infrared, nuclear magnetic resonance spectroscopic, gel permeation chromatography, and X-ray diffraction studies confirmed the physicochemical structure of the synthesized macroglycol and HBPURs. The degree of branching value (0.78–0.91) of HBPURs varies with this macroglycol content. These thermoplastic PUR elastomers exhibited outstanding toughness (205 MJ.m–³), unprecedented high elongation at break (2810–3160%), good tensile strength (8.2–9.5 MPa), impact resistance (>17.3 kJ/m), scratch resistance (4.0–4.5 kg), durometer hardness (52–60 Shore A), adhesive strength (3.3–6.7 kPa), thermostability (241–249 °C), and chemical and UV-resistance. Notably, HBPURs also showed excellent repeatable intrinsic self-healing efficiency (100%) under exposure of microwave (450 W). Moreover, HBPURs exhibited outstanding thermoresponsive shape recovery (100%) within 50–56 s at 60 °C. In addition, HBPURs showed acceptable biodegradation under the exposure of Pseudomonus aeruginosa and Bacillus subtilus bacterial strains. Again, HBPUR demonstrated superior performance over linear analogous PUR. Thus, HBPUR has great potential as a smart sustainable self-healing thermoplastic elastomer for different applications.
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Biobased Multifunctional Macroglycol Containing Smart Thermoplastic Hyperbranched Polyurethane Elastomer with Intrinsic Self-Healing Attribute
2018Co-Authors: Tuhin Ghosh, Niranjan KarakAbstract:Smart biobased self-healable polymers are advanced sustainable materials. Thus, a thermoplastic hyperbranched polyurethane (HBPUR) elastomer was synthesized by using a biobased multifunctional macroglycol along with other required components, for the first time. This biobased macroglycol was obtained by stoichiometric controlled esterification reaction of Dimer Acid with glycerol. Fourier transform infrared, nuclear magnetic resonance spectroscopic, gel permeation chromatography, and X-ray diffraction studies confirmed the physicochemical structure of the synthesized macroglycol and HBPURs. The degree of branching value (0.78–0.91) of HBPURs varies with this macroglycol content. These thermoplastic PUR elastomers exhibited outstanding toughness (205 MJ.m–3), unprecedented high elongation at break (2810–3160%), good tensile strength (8.2–9.5 MPa), impact resistance (>17.3 kJ/m), scratch resistance (4.0–4.5 kg), durometer hardness (52–60 Shore A), adhesive strength (3.3–6.7 kPa), thermostability (241–249 °C), and chemical and UV-resistance. Notably, HBPURs also showed excellent repeatable intrinsic self-healing efficiency (100%) under exposure of microwave (450 W). Moreover, HBPURs exhibited outstanding thermoresponsive shape recovery (100%) within 50–56 s at 60 °C. In addition, HBPURs showed acceptable biodegradation under the exposure of Pseudomonus aeruginosa and Bacillus subtilus bacterial strains. Again, HBPUR demonstrated superior performance over linear analogous PUR. Thus, HBPUR has great potential as a smart sustainable self-healing thermoplastic elastomer for different applications