Molecular Weight Mn Research Articles

Synthesis internal-plasticized PVC copolymer resin from industrial application view: Copolymerization of vinyl chloride with poly(ethylene glycol) monomethyl ether methacrylate via suspension polymerization

Developing internal-plasticized poly(vinyl chloride) (PVC) resin has been recognized as an effective way to deal with the issues of conventional PVC products such as toxicity and deterioration in properties caused by the migration of plasticizer. Herein, the copolymerization of vinyl chloride with commercial available poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) is firstly conducted via suspension polymerization and internally plasticized random copolymers (PVEGA) are synthesized successfully. These PVEGA copolymers were intensively characterized by FTIR, 1H NMR, GPC, DSC, DMTA, and SEM to determine the composition, number-average molecular weight (Mn), dispersity, glass transition temperature (Tg), and the micromorphology. As a result, the high transparency and the fracture images demonstrated the good compatability between PVC chains with long-chain polyether. The Tg of PVEGA decreased gradually from 80 to 0 °C with the fraction of PEGMA in the copolymer increased from 7 to 37 %. Furthermore, the PVEGA copolymer exhibits outstanding processibility and mechanical performance. Under optimal composition, the tensile strength and the elongation at break can reach to 8 MPa and 525 %, respectively. Meanwhile, the PVEGA copolymers exhibit much lower migration either in water or in orgnic solvent and excellent performance in hemolysis and cytotoxicity, showing great application potential in medical devices.

Poly(l-alanine-co-l-threonine succinate) as a Biomimetic Cryoprotectant.

We synthesized a series of [(l-Ala)x-co-(l-Thr succinate)y] (PATs), which are analogous to natural antifreezing glycoprotein with the structure of [l-Ala-l-Ala-l-Thr disaccharide]n, by varying the composition and degree of succinylation while fixing their molecular weight (Mn) and Ala/Thr ratio at approximately 10-12 kDa and 2:1, respectively. We investigated their ice recrystallization inhibition (IRI), ice nucleation inhibition (INI), dynamic ice shaping (DIS), thermal hysteresis (TH), and protein cryopreservation activities. Both IRI and INI activities were greater for PATs with higher l-Ala content (PATs-3 and PATs-4) than those with lower l-Ala content (PATs-1 and PATs-2). DIS activity with faceted crystal growth was clearly observed in PATs-2 and PATs-4 with a high degree of succinylation. TH was small with <0.1 °C for all PATs and slightly greater for PATs with a high l-Ala content. Except for PATs-1, the protein (lactate dehydrogenase, LDH) stabilization activity was excellent for all PATs studied, maintaining LDH activity as high as that of fresh LDH even after 15 freeze-thaw cycles. To conclude, the cryo-active biomimetic PATs were synthesized by controlling the l-Ala content and degree of succinylation. Our results showed that PATs with an l-Ala content of 65-70% and degree of succinylation of 12-19% exhibited the cryo-activities of IRI, INI, and DIS, and particularly promising properties for the cryoprotection of LDH protein.

Direct synthesis of polyethylene thermoplastic elastomers with high molecular weight and excellent elastic recovery via a hybrid steric bulky strategy

Recently, α-diimine nickel-catalyzed ethylene chain walking polymerization has enabled the direct preparation of polyethylene thermoplastic elastomers using ethylene as a single feedstock. In this study, a series of hybrid bulky butyl-based α-diimine nickel complexes constructed with o-aryl and -diarylmethyl anilines were synthesized and employed for the ethylene polymerization. All the nickel complexes showed high activities (level of 106 g mol-1h−1) and high molecular weight (Mn up to 1230.9 kg/mol) polyethylene with high branching density (82–118/1000C) were yielded in ethylene polymerization. The polyethylene obtained by Ni1-3 showed distinguished elastic properties (SR = 72–91 %) and the sample obtained by Ni1 at 50 °C exhibited optimal elastic recovery values (91 %), which is also the best reported so far in polyethylene elastomers. Compared to the corresponding nickel complexes with symmetrical ligand substituents, the complexes with unsymmetrical substituents (hybrid) in this study facilitate the synthesis of significantly higher branched polyethylene with much better elastic recovery. The hybrid cationic nickel catalysts are also capable of catalyzing the copolymerization of ethylene with methyl 10-undecenoate.

Toughening Brittle Bio-P3HB with Synthetic P3HB of Engineered Stereomicrostructures.

Poly(3-hydroxybutyrate) (P3HB), a biologically produced, biodegradable natural polyester, exhibits excellent thermal and barrier properties but suffers from mechanical brittleness, largely limiting its applications. Here we report a mono-material product design strategy to toughen stereoperfect, brittle bio or synthetic P3HB by blending it with stereomicrostructurally engineered P3HB. Through tacticity ([mm] from 0 to 100 %) and molecular weight (Mn to 788 kDa) tuning, high-performance synthetic P3HB materials with tensile strength to ≈30 MPa, fracture strain to ≈800 %, and toughness to 126 MJ m-3 (>110× tougher than bio-P3HB) have been produced. Physical blending of the brittle P3HB with such P3HB in 10 to 90 wt % dramatically enhances its ductility from ≈5 % to 95-450 % and optical clarity from 19 % to 85 % visible light transmittance while maintaining desirably high elastic modulus (>1 GPa), tensile strength (>35 MPa), and melting temperature (160-170 °C). This P3HB-toughening-P3HB methodology departs from the traditional approach of incorporating chemically distinct components to toughen P3HB, which hinders chemical or mechanical recycling, highlighting the potential of the mono-material product design solely based on biodegradable P3HB to deliver P3HB materials with diverse performance properties.

Toughening Brittle Bio‐P3HB with Synthetic P3HB of Engineered Stereomicrostructures

AbstractPoly(3‐hydroxybutyrate) (P3HB), a biologically produced, biodegradable natural polyester, exhibits excellent thermal and barrier properties but suffers from mechanical brittleness, largely limiting its applications. Here we report a mono‐material product design strategy to toughen stereoperfect, brittle bio or synthetic P3HB by blending it with stereomicrostructurally engineered P3HB. Through tacticity ([mm] from 0 to 100 %) and molecular weight (Mn to 788 kDa) tuning, high‐performance synthetic P3HB materials with tensile strength to ≈30 MPa, fracture strain to ≈800 %, and toughness to 126 MJ m−3 (&gt;110× tougher than bio‐P3HB) have been produced. Physical blending of the brittle P3HB with such P3HB in 10 to 90 wt % dramatically enhances its ductility from ≈5 % to 95–450 % and optical clarity from 19 % to 85 % visible light transmittance while maintaining desirably high elastic modulus (&gt;1 GPa), tensile strength (&gt;35 MPa), and melting temperature (160–170 °C). This P3HB‐toughening‐P3HB methodology departs from the traditional approach of incorporating chemically distinct components to toughen P3HB, which hinders chemical or mechanical recycling, highlighting the potential of the mono‐material product design solely based on biodegradable P3HB to deliver P3HB materials with diverse performance properties.

Relation of 3HV fraction and thermomechanical properties of poly(3–hydroxybutyrate–co–3–hydroxyvalerate) produced by Azotobacter vinelandii OP

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has attracted substantial attention as a promising material for industrial applications. In this study, different PHBV films with distinct 3-hydroxyvalerate (3HV) contents produced by Azotobacter vinelandii OP were evaluated. The 3HV fraction ranged from 18.6 to 36.7 mol%, and the number-average molecular weight (Mn) was between 238 and 434 kDa. In the bioreactor, a 3HV fraction (36.7 mol%) and an Mn value of 409 kDa were obtained with an oxygen transfer rate (OTR) of 12.5 mmol L−1 h−1. Thermal analysis measurements showed decreased melting (Tm) and glass transition (Tg) temperatures, and values with relatively high 3HV fractions indicated improved thermomechanical properties. The incorporation of the 3HV fraction in the PHBV chain improved the thermal stability of the films, reduced the polymer Tm, and affected the tensile strength. PHBV film with 36.7 mol% 3HV showed an increase in its tensile strength (51.8 MPa) and a decrease in its Tm (170.61 °C) compared with PHB. Finally, scanning electron microscopy (SEM) results revealed that the PHBV film with 32.8 mol% 3HV showed a degradation upon contact with soil, water, or soil bacteria, showing more porous surfaces after degradation. The latter phenomenon indicated that thermomechanical properties played an important role in biodegradation.

Multifaceted Shape Memory Polymer Technology for Biomedical Application: Combining Self-Softening and Stretchability Properties.

Thiol-ene polymers are a promising class of biomaterials with a wide range of potential applications, including organs-on-a-chip, microfluidics, drug delivery, and wound healing. These polymers offer flexibility, softening, and shape memory properties. However, they often lack the inherent stretchability required for wearable or implantable devices. This study investigated the incorporation of di-acrylate chain extenders to improve the stretchability and conformability of those flexible thiol-ene polymers. Thiol-ene/acrylate polymers were synthesized using 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO), Trimethylolpropanetris (3-mercaptopropionate) (TMTMP), and Polyethylene Glycol Diacrylate (PEGDA) with different molecular weights (Mn 250 and Mn 575). Fourier Transform Infrared (FTIR) spectroscopy confirmed the complete reaction among the monomers. Uniaxial tensile testing demonstrated the softening and stretching capability of the polymers. The Young's Modulus dropped from 1.12 GPa to 260 MPa upon adding 5 wt% PEGDA 575, indicating that the polymer softened. The Young's Modulus was further reduced to 15 MPa under physiologic conditions. The fracture strain, a measure of stretchability, increased from 55% to 92% with the addition of 5 wt% PEGDA 575. A thermomechanical analysis further confirmed that PEGDA could be used to tune the polymer's glass transition temperature (Tg). Moreover, our polymer exhibited shape memory properties. Our results suggested that thiol-ene/acrylate polymers are a promising new class of materials for biomedical applications requiring flexibility, stretchability, and shape memory properties.

Screening and degradation characteristics of plastic-degrading microorganisms in film-mulched vegetable soil

In recent years, the incomplete recycle of residual mulch film (RMF) leads to the increasing richness of plastic fragment in soil, which poses a serious threat to the soil ecological environment. Therefore, the degradation of RMF in soil has aroused the interest of researchers. In this study, the degradation microorganisms were screened from film-mulched vegetable field, the results showed that seven potential plastic-degradation microorganisms were screened and identified, including four bacteria (Burkholderia cepacia, Burkholderia diffusa, Burkholderia aenigmatica, Chrysebacterium nepalense) and three fungi (Geotrichum candidum, Fusarium oxysporum and Trichoderma sp.). The results of degradation ability experiments showed that the weight loss rate of single strains ranges from 1.58 to 2.44% after 90 d. The loss rate of weight-average molecular weight (Mw) and number-average molecular weight (Mn) for single strains after 30 d were 2.61–22.40% and 17.92–39.18%, respectively. In addition, the weight loss rate of the mixed strains ranges from 1.34 to 1.62% after 90 d. The loss rate of Mw and Mn for mixed strains after 30 d were 8.04–10.06% and 20.06–39.25%, respectively. The comparing results showed that there may be inhibitory interactions between microorganisms in mixed strains are culture. This research can provide theoretical basis and data support for the control and disposal measures of RMF pollution.

Degradation of Structurally Modified Polylactide under the Controlled Composting of Food Waste.

The degradation of polylactide (PLA) films of different structures under conditions of controlled composting has been studied. We have demonstrated that PLA underwent degradation within one month in a substrate that simulated standard industrial composting. Regardless of the initial structure of the samples, the number-average molecular weight (Mn) decreased to 4 kDa while the degree of crystallinity increased to about 70% after 21 days of composting. Addition of an inoculant to the standard substrate resulted in the accelerated degradation of the PLA samples for one week due to an abiotic hydrolysis. These findings have confirmed that industrial composting could solve the problem of plastic disposal at least for PLA.

Properties of Degradable Polyhydroxyalkanoates Synthesized from New Waste Fish Oils (WFOs).

The synthesis of PHA was first investigated using WFOs obtained from smoked-sprat heads, substandard fresh sprats, and fresh mackerel heads and backbones. All the WFOs ensured the growth of the wild-type strain Cupriavidus necator B-10646 and the synthesis of PHA, regardless of the degree of lipid saturation (from 0.52 to 0.65) and the set and ratio of fatty acids (FA), which was represented by acids with chain lengths from C14 to C24. The bacterial biomass concentration and PHA synthesis were comparable (4.1-4.6 g/L and about 70%) when using WFO obtained from smoked-sprat heads and fresh mackerel, and it was twice as high as the bacterial biomass concentration from the fresh sprat waste. This depended on the type of WFO, the bacteria synthesized P(3HB) homopolymer or P(3HB-co-3HV-co-3HHx) copolymer, which had a lower degree of crystallinity (Cx 71%) and a lower molecular weight (Mn 134 kDa) compared to the P(3HB) (Mn 175-209 kDa and Cx 74-78%) at comparable temperatures (Tmelt and Tdegr of 158-168 °C and 261-284 °C, respectively). The new types of WFO, studied for the first time, are suitable as a carbon substrates for PHA synthesis. The WFOs obtained in the production of canned Baltic sprat and Baltic mackerel can be considered a promising and renewable substrate for PHA biosynthesis.

Effects of dielectric barrier discharge plasma modification on structure, physicochemical and functional properties of watermelon peel pectin

Dielectric barrier discharge (DBD) plasma is a simple and green method for biomacromolecule modification, and watermelon peel pectin (WMP) has broad application prospect in food industry. This study investigated the effects of DBD plasma under different voltage (20 V, 40 V) and treatment time (1 min, 3 min, 5 min) on the structural, physicochemical and functional properties of WMP. The DBD plasma treatment (40 V, 5 min) exhibited the lowest molecular weight (Mw, 199.06 ± 8.05 kg/mol), average molecular weight (Mn, 27.15 ± 1.75 kg/mol), degree of methylation (DM, 36.18 ± 0.65%) and acetylation (DA, 2.33 ± 0.09%) of WMP. Moreover, DBD plasma treatment could degrade the main chain of WMP, and had less effect on the side chain. The microstructure of WMP changes from dense block structures to porous and thin fibrous, while pectin molecules are degraded and oxidized after DBD plasma treatment. Compared with the native WMP, DBD plasma treatment at different modes effectively increased the thermal stability, antioxidant ability, solubility and emulsifying properties of WMP, but lowered its shear thinning fluid behavior and liquid-like property. Conclusively, our results show that DBD plasma is a promising way to modified and improve functional properties of WMP.

Decoration, Characterization and Antimicrobial Activity Evaluation of Novel Nano‐Based 1,2‐Phenylenediamine Functionalized Maleic Anhydride‐Allylphenyl Ether Conjugate

Abstract1,2‐Phenylenediamine (o‐PDA) is a well‐known fluorescent dye that enables the decoration of next‐generation chemotherapeutics. A novel o‐PDA‐functionalized maleic anhydride‐allyl phenyl ether (poly(MA‐alt‐APE)/o‐PDA conjugate) was successfully synthesized according to the Ringsdorf model, which is the starting point for macromolecular prodrugs. Functional polymeric‐carriers were prepared by free‐radical polymerization in butyl acetate with azobisisobutyronitrile (AIBN) radical‐initiator at 70 °C. The conjugation was carried out at 40 °C in N,N‐dimethylformamide (DMF) using triethylamine (Et3N) as the conjugation catalyst. Characterization was performed by Attenuated Total Reflectance‐Fourier Transform Infrared (ATR‐FTIR), Nuclear Magnetic Resonance (1H‐NMR), UV‐Vis and Fluorescence Spectroscopy. Weight average molecular weight (Mw), number average molecular weight (Mn) and polydispersity index (PDI) (Mw/Mn) were calculated using gel permeation chromatography (GPC). The surface morphology was also elucidated by Transmission Electron Microscopy (TEM). Evaluation of antimicrobial activity against two Gram‐positive bacteria (Staphylococcus aureus, Bacillus cereus), two Gram‐negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and one yeast Candida albicans was performed using the broth microdilution method according to Clinical Laboratory Standards Institute (CLSI) criteria. Interestingly, S. aureus was found to be more sensitive to polymer‐based samples and, in particular, the minimum inhibitory concentration (MIC) of the conjugate was lower than that of ciprofloxacin used as a control compound.

Synthesis and its application on fabrics of disperse dye-encapsulated with waterborne polyurethane (WPU)

BackgroundUtilizing waterborne polyurethane (WPU), the commercial dyes disperse red 60 (R60), disperse yellow 54 (Y54), and disperse blue 56 (B56) are encapsulated to form micelle structures. When applied to fabric dyeing, this approach effectively enhances properties such as colorfastness and resistance to dry and wet rubbing. MethodCommercial disperse dyes were physically encapsulated using WPU to form micelles in a water medium. The structures of the encapsulated dyes were confirmed using 1H-NMR and FTIR spectroscopy. The average molecular weight (Mn) of the materials ranged from 2.2 × 104 to 2.9 × 104 g mol−1. UV-visible (UV-vis) spectra comparisons before and after encapsulation showed no significant color shift, indicating minimal alteration of the original dyes. However, all dye-WPU samples exhibited a notable quantum yield of 41% in the fluorescence spectra and displayed higher thermal stability compared to the dyes without WPU. Significant findingsThe electrical layer on dye-WPU particles enhanced fluorescence intensity. Zeta potential measurements confirmed particle stability (-32 to -55 mV). Micelle size ranged from 70-150 nm. Encapsulated dye-WPU showed improved thermal stability and Tg of −58 to −65 °C. Applied to fabrics, especially cotton, dye-WPU exhibited excellent color fastness and resistance to thermal migration in immersion or digital printing.

The Mechanical Properties and Degradation Behavior of 3D-Printed Cellulose Nanofiber/Polylactic Acid Composites.

Polylactic acid (PLA) has been widely used in many fields because of its good biodegradability, biocompatibility, and renewability. This work studied the degradation behavior and mechanical properties of cellulose nanofiber (CNF)/PLA composites. In vitro degradation experiments of 3D-printed samples were conducted at elevated temperatures, and the degradation characteristics were evaluated by mechanical tests, gel permeation chromatography (GPC), differential scanning calorimetric (DSC), and scanning electron microscope (SEM). The results indicated that the addition of CNF (0.5 wt%) accelerated the degradation rate of PLA. The decreases in number average molecular weight (Mn) and weight average molecular weight (Mw) of composites were 7.96% and 4.91% higher than that of neat PLA, respectively. Furthermore, the tensile modulus of composites was 18.4% higher than that of neat PLA, while the strength was 7.4% lower due to poor interfacial bonding between CNF and PLA. A mapping relationship between accelerated and normal degradation showed that the degradation experienced during 60 days at 37 °C was equivalent to that undergone during 14 days at 50 °C; this was achieved by examining the alteration in Mn. Moreover, the degradation process caused a notable deformation in the samples due to residual stress generated during the 3D printing process. This study provided valuable insights for investigating the in vitro degradation behavior of 3D-printed products.

Study on high-temperature degradation of acrylamide-based polymer ZP1 in aqueous solution

As exploration of deep and ultra-deep becomes more active, the utilization of acrylamide-based polymers as drilling fluid additives in challenging subsurface conditions, particularly at high temperatures, is growing. In this study, various monomers including acrylamide (AM), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and dimethyl diallyl ammonium chloride (DMDAAC) were used to synthesize an acrylamide-based polymer ZP1. Subsequently, 2.5 wt% aqueous solution of polymer ZP1 was subjected to a high-temperature degradation test at temperatures of 150, 180, 200, 220, and 240 °C, respectively. The degradation behavior of the polymer in aqueous solution and drilling fluid was investigated using various analytical techniques, including FT-IR, 1H NMR, XPS, GPC, TG-IR, and SEM. The research results indicate that the degradation temperature of the solid polymer sample was 258 °C, while in the solution at a temperature higher than 200 °C, the hydrolysis and imidation reaction in the polymer molecular chain was accelerated, which caused the main chain of the polymer to break easily. When the molecular weight (Mn) of the polymer decreased to less than 10,000, the protective influence of the polymer on the drilling fluid was lost, resulting in deterioration of the performance of the drilling fluid. However, the functional groups (amide groups, sulfonic acid groups, and quaternary ammonium groups) on the molecular chain of the polymer were retained.

Ring‐Opening Polymerization of ϵ‐Caprolactone by Benzoic Acid in the Presence of Benzyl Alcohol as Initiator

AbstractThe development of a feasible industrial method for poly(ϵ‐caprolactone) (PCL) preparation is great of significant and challenging. The bulk ring‐opening polymerization of ϵ‐caprolactone (ϵ‐CL) using various organic acid catalysts and benzyl alcohol (BnOH) as the initiator was developed. Benzoic acid (BA) has been proved to be an efficient catalyst for the ROP of ϵ‐CL under mild conditions. The conversion of ϵ‐CL to PCL was 84.7 % under the optimized reaction conditions, with number‐average molecular weight (Mn) and dispersity (PDI) of 7700 g/mol and 1.25, respectively. Moreover, a monomer‐activated ring‐opening polymerization mechanism mediated by benzoic acid was proposed. Overall, this work is expected to provide a feasible industrial method for the preparation of PCL using benzoic acid as organocatalyst.

Rational design for the development of thermoplastic poly(ether-ester) elastomers from bio-based 2,5-furandicarboxylic acid with high elasticity

Development of bio-based thermoplastic poly(ether-ester) elastomer (TPEE) with high performance similar to commercial and petroleum-based TPEE is of great interesting nowadays. Herein, by considering both the hard and soft segments, a rational design strategy is proposed for the synthesis of bio-based TPEE with high elasticity based on a bio-based aromatic monomer 2,5-furandicarboxylic acid (FDCA). The hard segment is poly(neopentyl glycol 2,5-furandicarboxylate) (PNF), a FDCA-based polyester with both high melting temperature and crystallization ability. While the soft segment is poly(tetramethylene glycol) (PTMG), which is widely used for the synthesis of TPEE. By adjusting the molecular weight (Mn) of PTMG soft segment from 650 to 2900 g/mol and its content from 50 to 70 wt%, a series of bio-based TPEEs with excellent performance were synthesized. Our preliminary study of PNF-PTMG multiblock copolymers has shown that the elastic recovery rate is outstanding. The initial elastic recovery ratio at 200 % strain can approach 80 % when the Mn of PTMG is 2000 g/mol and the wt.% of PTMG was 70 %, which is significantly higher than those of the commercial TPEEs. PNF-PTMG displays increasing thermal resistance with Tm up to 194 °C with the increasing of soft segment length. This study suggests a feasible solution for the preparation of bio-based TPEE with ideal performance.

Hot Melt Extrusion as a Formulation Method of Terpolymer Rods with Aripiprazole: A Preliminary Study

Aripiprazole (ARP) is an atypical neuroleptic used in the therapy of mental diseases such as schizophrenia. The lack of optimal adherence to an oral therapy regime creates the basis for designing ARP long-acting injections. This study aimed to use 105 °C hot melt extrusion (HME) as a formulation method for rods based on poly(d,l-lactide-co-glycolide-co-trimethylene carbonate) with a molecular weight (Mn) of 21 kDa (Td,l 21), poly(l-lactide-co-glycolide-co-trimethylene carbonate) with a Mn of 59 kDa (Tl 59), and with a Mn of 77 kDa (Tl 77). The following methods were involved in the research: NMR, DSC, XRD, HSM, FTIR, GPC, SEM, and mechanical tests. HME at 105 °C (i) ensured flow behavior for terpolymers, (ii) did not influence the terpolymers’ composition and (iii) the polymorph changes of ARP, and (iv) resulted in the changes in terpolymers’ Mn. For the rods with ARP based on Td,l 21 (Td,l 21 rod-ARP) and Tl 59 (Tl 59 rod-ARP), plasticization was noted. No drug–terpolymer interactions were revealed. No pores were observed on the surface. Due to its high flexibility and rubber character, Td,l 21 rod-ARP may be proposed for intramuscular administration, whereas Tl 59 rod-ARP, due to its higher strength and moderate stiffness, is proposed for subcutaneous administration.

Impact of Bark-Sourced Building Blocks as Substitutes for Fossil-Derived Polyols on the Structural, Thermal, and Mechanical Properties of Polyurethane Networks.

The hydrophilic extractives isolated from black alder (Alnus glutinosa) bark through hot water extraction were characterized as novel renewable macromonomers capable of forming polyurethane (PU) networks based on a commercial polyisocyanate, with partial or complete replacement of petroleum-derived polyol polyether. The bark-sourced bio-polyol mainly consists of the xyloside form of the diarylheptanoid oregonin, along with oligomeric flavonoids and carbohydrates, resulting in a total OH group content of 15.1 mmol·g-1 and a molecular weight (Mn) of approximately 750 g∙mol-1. The 31P NMR data confirmed a similar proportion of aliphatic OH and phenolic groups. Three-component PU compositions were prepared using polyethylene glycol (Mn = 400 g∙mol-1), bio-polyol (up to 50%), and polymeric diphenylmethane diisocyanate, which were pre-polymerized in tetrahydrofuran (THF) solution with tin organic and tertiary amine catalysts. The resulting mixture was cast and subjected to thermal post-curing. Calculation and experimental data confirmed the crosslinking activity of the bark-sourced bio-polyol in PU, leading to an increase in glass transition temperature (Tg), a decrease in sol fraction yield upon leaching of cured PU networks in THF, a significant increase in Young's modulus and tensile strength. The macromonomers derived from bark promoted char formation under high temperature and oxidative stress conditions, limiting heat release during macromolecular network degradation compared to bio-polyol-free PU. It was observed that amine catalysts, which are active in urethane formation with phenolic groups, promoted the formation of PU with higher Tg and modulus at tensile but with less limitation of heat liberation during PU macromolecular structure degradation. The high functionality of the bark-derived bio-polyol, along with the equal proportion of phenolic and aliphatic OH groups, allows for further optimization of PU characteristics using three variables: increasing the substitution extent of commercial polyethers, decreasing the NCO/OH ratio, and selecting the type of catalyst used.

Highly active and thermally robust pyridylbenzotriazole iron-based catalysts for preparation of polyisoprenes that feature high wet traction and low rolling resistance

A series of pyridylbenzotriazole iron (II) complexes with general formula (L2FeCl2) were synthesized and characterized by IR, ESI-MS, and elemental analysis. Determined by single-crystal X-ray crystallography, complex Fe1 adopts a distorted octahedral geometry. Upon activation with methylaluminoxane (MAO), the activity of the complex for isoprene polymerization decreased as the bulkiness of the substituent at 6-position of the pyridyl ring of the ligand increased. Notably, Fe1 exhibited excellent activity of 4.1 × 106 g/(mol (Fe)•h), affording polymers with ultra-high molecular weight (Mn = 2380 × 103 g/mol) and narrow distributions (Mw/Mn = 1.72). The resulting polyisoprenes possessed predominantly cis-1,4/3,4 alternating structure and short cis-1,4 and 3,4 sequences, irrespective of the reaction conditions, indicating high thermal stability of the catalyst. Moreover, the prepared polyisoprene composite showed higher mechanical properties compared to SSBR-2466 and SSBR-5025 which are the key components of current commercial tread rubber, and had comparable wet traction and superior rolling resistance.