Effect Of Comonomer Research Articles

Mechanism of the Comonomer Effect in LLDPE from Ethylene/1-Hexene Using a Quinoline-Amine Hafnium Catalyst

Mechanism of the Comonomer Effect in LLDPE from Ethylene/1-Hexene Using a Quinoline-Amine Hafnium Catalyst

Enhanced thermal conductivity and mechanical property via improvement of hydrogen bonding between hexagonal boron nitride and aramid copolymer

This study focuses on enhancing thermal properties of aramid copolymer nanocomposites by integrating hexagonal boron nitride (hBN). Pristine hBN (P-hBN) is first subjected to oxidative heat treatment at 900 °C, producing thermally treated hBN (T-hBN), which significantly improves thermal conductivity while also increasing the tensile properties of composites. The study further explores the effect of different diamine co-monomers, 3,4′- and 4,4′-oxydianiline (ODA), on the nanocomposite properties. Both types of ODA-based composite films show improvement in various properties containing T-hBN. With 20 wt% of T-hBN, the 3,4′-ODA and 4,4′-ODA-based films exhibit 33.2 % and 290 % increase in tensile strength and thermal conductivity, respectively. The functionalization of hBN by heat treatment enhances the interaction between aramid copolymer and hBN and prevents the aggregation of hBN. The rough interface was shown in fractured images for films with T-hBN, suggesting that the composite films with T-hBN withstand higher external forces. In addition, it was observed that T-hBN exhibits better dispersion compared to P-hBN. This is supported by molecular dynamics (MD) simulation, and, in addition, it also provides the underlying mechanism for the property differences between both types of co-monomers.

Negative comonomer effect induced by TiCl3-like clusters in MgCl2-based Ziegler-Natta catalysts

The comonomer effect of ethylene/α-olefin copolymerization in the Ziegler-Natta (Z-N) catalytic system, remaining largely elusive and less understood at the molecular level, has been of huge industrial importance and absorbing research interest for decades. Herein, four catalysts with similar physical structures but different polymerization activities and comonomer effects were synthesized by using n-butanol in combination with different secondary electron donors. By tracking catalyst formation, it was found that altering the secondary donor changes the ν(O-H) stability and in turn the MgCl2 facet growth, to influence the polymerization activity. In situ diffuse reflectance Ultraviolet–visible spectra show that different types of active Ti centers are in function in the ethylene polymerization and the ethylene/1-butene copolymerization. Tracing further the microscopic structures of active species upon triethylaluminium (TEA) activation by using Extended X-ray Absorption Fine Structure, it is found that: (i) for the catalysts with negative comonomer effect, the enhanced donor migration promotes the aggregation of active species and leads to the formation of TiCl3-like clusters; (ii) by contrast, for the catalysts with positive comonomer effect, the less mobile donors hinder the aggregation of active species, thus inducing the formation of isolated Ti3+ sites. Our work reveals an evident correlation between the active center and the comonomer effect, which may be strongly modified by the aggregation of the former.

Comonomer effects in vinyl based photocatalytic polymers

Photocatalytic efficiency can be altered by changing the polymer in which a small molecule photocatalyst is incorporated. The microenvironment around the active center regulates the photophysical properties, and may control substrate proximity.

Thermal oxidation of diallylbisphenol A - bismaleimide networks. Comonomer effect and kinetic modelling

Pure BMI resin based on 4,4′-bismaleimidodiphenylmethane (BMI) and its copolymers with various quantities of 2,2′-diallylbisphenol A (BMI-DABPA 2–1, BMI-DABPA 1–1, BMI-DABPA 1–2) were thermally aged. Ageing at 160 °C was monitored by FTIR and showed the greatest reactivity of diallyl groups which accelerate the degradation of BMI-DABPA copolymers. It was confirmed by a gravimetric study of ageing under nitrogen or oxygen at 350 and 375 °C. A co-oxidation kinetic model was proposed for describing the oxidation of BMI and BMI-DABPA systems. The effect of the main kinetic parameters was discussed from a parametric study. The main rate constants were estimated from the fitting of experimental curves and comparable gravimetric data from literature.

Effect of Terephthaloyl Chloride Comonomer on Thermal and Optical Properties of Colorless and Transparent Polyimide Films Based on 4, 4′-(Hexafluoroisopropylidene) Diphthalic Anhydride and Bis(3-aminophenyl) Sulfone

Effect of Terephthaloyl Chloride Comonomer on Thermal and Optical Properties of Colorless and Transparent Polyimide Films Based on 4, 4′-(Hexafluoroisopropylidene) Diphthalic Anhydride and Bis(3-aminophenyl) Sulfone

Synthesis, characterization, thermokinetic analysis and biological application of novel allyl glucosamine based glycopolymers

ABSTRACTThe synthesis of glycopolymers by copolymerising an allyl glucosamine (AG) monomer with co-monomers methyl methacrylate (MMA), acrylonitrile (AN) and 2-hydroxyethyl methacrylate (HEMA) was investigated via free-radical polymerisation of 2,2-azobisisobutyronitrile (AIBN) in dimethylformamide (DMF). Three new copolymers, poly(AG-co-MMA), poly(AG-co-AN) and poly(AG-co-HEMA), were obtained. The chemical structures of the glycopolymers were analysed using 1H-NMR, 13C-NMR and FTIR. The thermal properties and degradation kinetics of the three glycopolymers were examined by thermogravimetric (TG) analysis at different heating rates. The effects of different co-monomers on the copolymerisation yield, thermal properties and biological activities of the resulting glycopolymers were investigated. The activation energies of the decomposition stages were calculated using the Flynn–Wall–Ozawa (FWO) and Kissinger methods. Furthermore, the biological activity of AG monomers and glycopolymers was studied and compared to chitosan. Poly(AG-co-HEMA) had the most significant effect on MCF-7 cell viability, and all glycopolymers have a low toxic effect profile on MCF-7 cell lines.

Thermal stability of polymethacrylic based ELIUM® resin: Effect of comonomers, antioxidants and aluminum trihydrate filler

This paper presents the study of the thermal degradation of methyl methacrylate resin based materials known as ELIUM® resin. Samples under investigation were made from MMA based resin (ELIUM® V1), ELIUM® V1 with a dimethacrylate comonomer (ELIUM® V2), and ELIUM® V2 with a stabilizer package (ELIUM® V3). They were used for trying to discuss the degradation mechanisms. Blocks differing by their thickness made from ELIUM® formulation filled with aluminum TriHydrate used as flame retardant were also investigated in order to better match some industrial materials. Degradation was observed to be mainly driven by unzipping, consistent with the methacrylic nature of ELIUM® resin. Occurrence of oxidation is also discussed depending on materials formulation and temperature. A blend of antioxidants was inefficient for limiting mass loss. At 200 °C, both ATH and ELIUM® degrade, which contributes to overall mass loss. At temperatures below 180 °C, ATH does not seem to induce new degradation mechanisms but would increase oxygen diffusivity. Finally, a first simple kinetic model is proposed to predict mass loss in thick composite blocks aged under air.

Poly(N-vinylcaprolactam)-Gold Nanorods-5 Fluorouracil Hydrogels: In the Quest of a Material for Topical Therapies against Melanoma Skin Cancer.

Chemically crosslinked hydrogels based on poly(N-vinylcaprolactam) (PNVCL) were synthetized by a photoinitiated chemical method. A galactose-based monomer, 2-lactobionamidoethyl methacrylate (LAMA), and N-vinylpyrrolidone (NVP) were added with the aim to improve the physical and chemical properties of hydrogels. The effects of both comonomers on the swelling ratio (Q), volume phase transition temperature (VPTT), glass transition temperature (Tg), and Young's moduli by mechanical compression below and above the VPTT were studied. Gold nanorods (GNRDs) and 5-fluorouracil (5FU) were embedded into the hydrogels, to study the drug release profiles with and without the excitation of GNRDs by irradiation in the near-infrared region (NIR). Results showed that the addition of LAMA and NVP increased the hydrogels' hydrophilicity, elasticity, and VPTT. The loading of GNRDs in the hydrogels changed the release rate of 5FU when irradiated intermittently with an NIR laser. The present study reports on the preparation of a hydrogel-based platform of PNVCL-GNRDs-5FU as a potential hybrid anticancer hydrogel for chemo/photothermal therapy that could be applied against skin cancer for topical 5FU delivery.

Effect of Different Comonomers Added to Graft Copolymers on the Properties of PLA/PPC/PLA-g-GMA Blends

The melt-free radical grafting of glycidyl methacrylate (GMA) onto poly (lactic acid) (PLA) with styrene (St), α-methylstyrene (AMS), and epoxy resin (EP) as comonomers in a twin-screw extruder was used to prepare PLA-g-GMA graft copolymers. The prepared graft copolymers were then used as compatibilizers to prepare PLA/PPC/PLA-g-GMA blends by melt blending with PLA and polypropylene carbonate (PPC), respectively. The effects of different comonomers in the PLA-g-GMA graft copolymers on the thermal, rheological, optical, and mechanical properties and microstructure of the blends were studied. It was found that the grafting degree of PLA-g-GMA graft copolymers was increased to varying degrees after the introduction of comonomers in the PLA-g-GMA grafting reaction system. When St was used as the comonomer, the grafting degree of the PLA-g-GMA graft copolymer increased most significantly, from 0.8 to 1.6 phr. St as a comonomer also most improved the compatibility between PLA and PPC, and the haze of the blends was reduced while maintaining high transmittance. In addition, the PLA-g-GMA graft copolymer with the introduction of St as a comonomer significantly improved the impact toughness of the blends, while the thermal stability and tensile strength of the blends remained largely unchanged.

Modeling of the molecular weight distribution and short chain branching distribution of linear low-density polyethylene from a pilot scale gas phase polymerization process

Molecular weight distribution (MWD) and short chain branching distribution (SCBD) play a decisive role in the performance of linear low-density polyethylene (LLDPE). A model based on a non-standard polymerization reaction scheme is developed for ethylene/α-olefin gas phase copolymerization in a fluidized bed reactor. Experimental MWD and SCBD are simultaneously deconvoluted. The results obtained by this simultaneous deconvolution method are physically more relevant. Reduction of parameters and parameter estimability analysis are conducted to screen parameters to obtain a subset for reliable parameter estimation. The model based on the estimated parameters yields MWD and SCBD which are in good agreement with experimental ones for several LLDPE grades obtained from a pilot-scale gas phase polymerization process. The non-standard polymerization reaction scheme depicts well the “comonomer effect” - activation of dormant ethylene species.

Effect of N-vinylimidazole comonomer on blood plasma protein and endogenous toxin adsorption on mesoporous copolymer beads

N-vinylimidazole-divinylbenzene (VI-DVB) copolymer beads with a N-vinylimidazole (VI) weight content ranging from 7% to 15% were studied as possible adsorbents for hemoperfusion and compared with the cross-linked polystyrene beads from commercial devices. All the beads had a large volume fraction of mesopores with diameters of 2–50 nm, quantified by nitrogen adsorption, and BET areas from 500 to 1000 m²/g. Metal-chelate adsorption of copper (II) ions on VI-DVB was high in 0.15 M NaCl (up to 40 μmol/mL), and low in blood plasma (< 1 μmol/mL). Reversible adsorption of blood plasma proteins was high (> 100 mg/mL beads) on all the bead types. Irreversibly adsorbed proteins eluted by 2% SDS included albumin, fibrinogen, fibronectin, and transferrin. Metal chelating contributed to the irreversible adsorption. Unlike the beads from commercial devices, VI-DVB beads adsorbed the LPS endotoxin from plasma. Adsorption of bilirubin and IL-6 was high on all the beads tested, but VI-DVB beads were better adsorbents of bile acids. VI-DVB are promising as components of multifunctional devices for blood purification applicable to treatment of diseases where conventional devices have lower or negligible adsorption capacity.

Rheology, crystallization, and enhanced mechanical properties of uniaxially oriented ethylene–octene copolymer/polyolefin elastomer blends

The application of polyethylene in artificial turf promotes research on the processing and properties of uniaxial extension modified polyethylene materials. The effects of comonomer (octene/butene) structure on the properties of pre-stretched linear low density polyethylene (LLDPE)/polyolefin elastomer (POE) blends are investigated. The melt tensile stress and melt stretch ratio of LLDPE ethylene‒octene copolymer (EOC)/POE reach 4.0 × 105 Pa and 12.8, respectively. At the pre-stretching ratio λ = 5, the tensile strength of EOC/POEλ5 reaches 62.5 MPa, the critical length is 5.7 mm, and the strain hardening degree increases. Differential scanning calorimetry, Raman spectroscopy and X-ray diffraction show the crystallinity of EOC/POEλ5 is higher than that of LLDPE ethylene‒butene copolymer (EBC)/POEλ5. Large short-chain branch length EOC is demonstrated to rebuild the “physical crosslinking point” after pre-stretched, thereby enhancing the interaction between molecular chains in EOC/POEλ5. This research provides a new clue for the development of artificial turf materials.

Physical Properties and Polymorphism of Acrylic Acid-Grafted Poly(1,4-butylene adipate-co-terephthalate)/Organically Modified Layered Double Hydroxide Nanocomposites.

Novel and biodegradable acrylic acid-grafted poly(1,4-butylene adipate-co-terephthalate)/organically modified layered double hydroxide (g-PBAT/m-LDH) nanocomposites were synthesized through the polycondensation and transesterification process, with the covalent linkages between the polymer and the inorganic materials. X-ray diffraction and transmission electron microscopy were used to characterize the structure and morphology of the g-PBAT/m-LDH nanocomposites. The experimental results show that the m-LDH was exfoliated and widely distributed in the g-PBAT matrix. The addition of m-LDH into the g-PBAT extensively improved the storage modulus at −90 °C, when compared to that of the pure g-PBAT matrix. The effects of the minor comonomer of the butylene terephthalate (BT) unit and the addition of m-LDH on the crystallization behavior, and the polymorphic crystals of the g-PBAT at numerous crystallization temperatures, were examined, using a differential scanning calorimeter (DSC). The data indicate that the minor comonomer of the BT unit into g-PBAT can significantly change the starting formation temperatures of the α-form and ꞵ-form crystals, while a change in the starting formation temperatures of the α-form and ꞵ-form crystals using the addition of m-LDH into g-PBAT is not evident.

Thermoresponsive oligo(ethylene glycol) methyl ether methacrylate based copolymers: composition and comonomer effect

Thermoresponsive polymers based on oligo(ethylene glycol) (OEG) methyl ether methacrylate monomers from unimers to micelles to precipitation.

Structural evolution of mesomorphic propylene–1‐butene random copolymer during heating process

AbstractThe study of the transition of mesophase to α‐crystal (meso–α transition) is of great significance for understanding the crystallization, morphology as well as processability of polypropylene materials. The structural evolution of mesomorphic isotactic propylene–1‐butene (iPPBu) random copolymer during the continuous heating process was investigated using in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction and dynamic mechanical analysis. The presence of the butene comonomer influences the meso–α transition behavior. Compared with the mesomorphic iPP homopolymer, the presence of butene comonomer reduces both onset temperature (Tonset) and end temperature (Tend) of the meso–α transition, and narrows the transition temperature range. The content of the 31 helical sequence with 12 monomers remains invariant during the meso–α transition, differing from that of mesomorphic iPP homopolymer. Similar to mesomorphic iPP homopolymer, the 31 helical sequence with monomer number n ≤ 12 is found to exist in the rigid amorphous fraction of iPPBu, but is different from that of a mesomorphic propylene–ethylene random copolymer. In the meso–α transition (from 60 to 100 °C), the redshift of the peak position of the band at ca 841 cm−1 provides new information for the approaching of adjacent stems at the molecular level. Moreover, a new peak at around Tend is found in the tan(δ)–T plot, and is correlated with the meso–α transition. The activation energy of the meso–α transition of mesomorphic iPPBu is 32.5 kJ mol−1, which is slightly lower than that of mesomorphic iPP homopolymer. This work sheds new light on further understanding of the meso–α transition mechanism of iPPBu copolymer at the molecular level and elucidates the effect of butene comonomer on the meso–α transition. © 2021 Society of Industrial Chemistry.

Amino acid functionalized macroporous gelatin cryogels: Characterization and effects on cell proliferation

Gelatin and N-methacryloyl-(L)-histidine methyl ester [MAH] containing poly(2-hydroxyethyl methacrylate) [PHEMA] based cryogels were prepared to aid in enhancing cell proliferation. In order to evaluate effects of MAH comonomer and gelatin, cryogels were prepared containing different amounts of gelatin and MAH. Accordingly, four different groups of cryogels which were PHEMA, poly(2-hydroxyethyl methacrylate)-gelatin [PHEMA/GEL], poly(2-hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester) [PHEMAH] and poly(2-hydroxyethyl methacrylate-N-methacryloyl-(L)-histidine methyl ester)-gelatin [PHEMAH/GEL] were prepared and a total of eight cryogel groups were obtained depending on the varying gelatin ratios. Swelling tests, scanning electron microscope (SEM), microcomputed tomography (Micro-CT) and Fourier transform infrared spectroscopy- Attenuated Total Reflectance (FTIR-ATR) were performed for characterization studies. FTIR-ATR studies confirmed that gelatin and MAH were incorporated into the cryogel structures. Average pore size of cryogels was in the range of 18−198 μm confirmed by Micro-CT and SEM analysis. Then, cryogels were evaluated for cell proliferation abilities by MTT analysis for 24 h and 48 h for cell viability in L929 mouse fibroblast cells. Cell viability of PHEMAH/0.2GEL cryogels reached 209 %. Interaction and proliferation of fibroblast cells on cryogels demonstrated by SEM examination.

Effects of Comonomers on the Performance of Stable Phosphonate-Based Gel Terpolymer Electrolytes for Sodium-Ion Batteries with Ultralong Cycling Stability.

Gel polymer electrolyte (GPE) is one of the most promising alternatives to solve the bottlenecks of nonaqueous liquid electrolytes such as decomposition, safety hazards, and growth of dendrites. In this work, three novel methyl phosphonate-based crosslinking gel terpolymer electrolytes with different comonomers are designed and prepared by in situ radical polymerization. The gel polymer electrolytes have excellent thermal stability, wide electrochemical windows (≥4.9 V), and high ionic conductivities (±3 mS cm-1), and may be used as less-flammable electrolytes for sodium-ion batteries. 31P NMR spectra, Arrhenius plot, and density functional theory (DFT) calculations confirm that multifunctional phosphonate structural units promote the dissociation of NaClO4 and help to transport the sodium ions freely in the polymer framework. X-ray photoelectron spectroscopy (XPS) results show that the gel polymer electrolytes have the capability of inhibiting liquid electrolyte decomposition and the formation of the stable solid electrolyte interphase (SEI) film. The Na3V2(PO4)3/GPE/Na cells exhibit better ultralong cycling stability and enhanced temperature performance than those of liquid cells. Strikingly, GPE1 has the best comprehensive electrochemical performance, especially the rate performance and long-term cycling stability with a capacity retention ratio of 82.6% after 3500 cycles, which indicates that different comonomers have obvious effects on the performance. Therefore, the full cell of SnS2/GPE1/Na3V2(PO4)3 is evaluated and delivers good cycling stability of 500 cycles, holding a great prospect for the design and production of phosphorus-containing electrolytes for safer sodium-ion batteries.

Isospecific alternating copolymerization of unprotected polar styrenes and ethylene by the Cs symmetric scandium precursor via synergistic effects of two substituent groups

Coordination polymerization of polar monomers bearing two functional groups has been a formidable challenge due to much higher poisonous possibility. In this contribution, we reported the coordination (co)polymerization of FMOSs bearing two functional groups, 4-fluoro-2-methoxystyrene (2,4-FMOS), 5-fluoro-2-methoxystyrene (2,5-FMOS) and 6-fluoro-2-methoxystyrene (2,6-FMOS) using the quinolyl methylene fluorenyl complexes (Flu-CH2-Qu)Sc(CH2SiMe3)2 (1) and (Flu-CH2-Qu)Y(CH2SiMe3)2(THF) (2) and the β-diketiminato complex (bis(2,6-dimethyl anilido)ketimine)Y(CH2SiMe3)2(THF) (3). Excellent syndiotactic P(2,6-FMOS) (rrrr > 99%) was isolated from complex 1 in a moderate activity, while, almost atactic P(2,6-FMOS) was obtained by complexes 2 and 3. Polymerizations of both 2,4-FMOS and 2,5-FMOS showed high activities and excellent syndioselectivity (rrrr>99%) by complexes 1 and 2, and perfect isoselectivity (mmmm > 99%) by complex 3. Moreover, copolymerizations of ethylene (E)/2,4-FMOS and E/2,6-FMOS catalyzed by complex 1, respectively, displayed the positive comonomer effect in much higher activities than those of E/2,5-FMOS and E/2-methoxystyrene (MOS) to afford perfect isotactic (mmmm > 99%) alternating products E-alt-FMOS. This work represents the first example of isoselective alternating copolymerization of E and the unprotected polar styrenes, in particular those bearing two polar substituents. The reasons for the formation of isoselective and alternating structures of polymers might be attributed to the unique synergistic effects of fluorine and o-methoxy groups. The mechanism was elucidated by the DFT calculations.

Surface vs Homogeneous Organo-Hafnium Catalyst Ion-Pairing and Ligand Effects on Ethylene Homo- and Copolymerizations

Heterogeneous catalysts have long dominated polyethylene and polypropylene production, but understanding their catalysis is challenged by uncertainties in active site structures and percentages. Surface-bound organometallic catalysts are an emerging strategy to combine successful homogeneous catalysts having well-understood structures, relatively high percentages of active sites, and exceptional control of selectivity, with the attractions of surface catalysts, to transition promising homogeneous systems to large-scale heterogeneous ones. Nevertheless, surface-bound olefin polymerization catalysts typically produce ultrahigh Mw’s but with low activity and comonomer selectivity. Here, we report the systematic synthesis and characterization of a series of pyridylamido–Hf complexes and their corresponding surface catalysts chemisorbed on sulfated alumina (AlS) and zirconia (ZrS). Comparative ethylene homo- and 1-octene copolymerizations reveal similar activity and 1-octene selectivity trends in the homogeneous and heterogeneous systems. For the surface pyridylamido–Hf catalyst series, large variations in activity (up to 10×) and 1-octene incorporation (up to 28×) are achieved by ligand and support manipulation. Interestingly, while the homogeneous catalysts exhibit positive comonomer effects in ethylene/1-octene copolymerization, the surface catalysts behave oppositely. Extended X-ray absorption fine structure (EXAFS) reveals significantly elongated Hf···O bond distances vs typical Hf–O covalent bonds (2.06 vs 1.97 Å). Density functional theory (DFT) analysis of the heterolytic ion pair separation enthalpies, olefin insertion energetics, and NBO/Bader charges also suggest electrostatic Hf cation–anionic support binding and catalytic patterns, which are modulated by the ion-pairing energetics and ligand architecture.