Fig 1 Synthesis of E/IUD copolymers and PE ionomers.
Published:01 August 2024,
Published Online:26 June 2024,
Received:21 March 2024,
Revised:21 April 2024,
Accepted:22 April 2024
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Owing to its high production volume and wide range of applications, polyethylene has gained a great deal of attention, but its low surface energy and non-polar nature have limited its application in some important fields. In this study, ethylene/11-iodo-1-undecene copolymers were prepared and used as the intermediates to afford a series of imidazolium-based ionomers bearing methanesulfonate (CH3SO3−), trifluoromethanesulfonate (CF3SO3−), or bis(trifluoromethane)sulfonimide (Tf2N−) counteranions. The tensile test results showed that the stress-at-break (7.8−25.6 MPa) and the elongation-at-break (445%−847%) of the ionomers could be adjusted by changing the counterion species and the ionic group contents. Most importantly, the ionomers exhibited marvelous antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The ionomers bearing Tf2N− exhibited antibacterial activities >99% against both S. aureus and E. coli when ionic content reached 9.1%. The imidazolium-based ionomers prepared in this work demonstrated excellent comprehensive properties, especially high-efficient and broad-spectrum antibacterial ability, exhibiting the potential for the application as the antibacterial materials in packaging, medical, and other fields.
Polyethylene;
Ionomer;
Polymerization catalysis;
Imidazolium;
Antibacterial material
Polyethylene (PE) is one of the most highly produced polyolefin materials and has a wide range of applications in daily necessities, automobiles, packaging, construction, agriculture, and other fields.[
PE ionomers are usually prepared by direct copolymerization or reactive intermediate methods. The direct copolymerization method has strict requirements for the catalyst, and only a very few catalysts are capable of directly copolymerizing ethylene with ionized monomers.[
The reactive intermediate method involves the synthesis of PE containing highly reactive groups which then undergoes functional group transformations to yield functionalized PE.[
PE materials have been widely used in biomedical applications, such as packaging, containers, implants, artificial joints, catheters, etc.[
All oxygen- and/or moisture-sensitive procedures were performed in an Etelux glove box or under nitrogen protection using standard Schlenk techniques. Anhydrous toluene was purified using the Etelux solvent purification system. The rac-Et(Ind)2ZrCl2 complex was purchased from Strem Chemicals, Inc., America. Methylaluminoxane (MAO), 1.5 mol/L in toluene was purchased from Innochem Technology, Co., Ltd., China. Commercial ethylene (99.9%) was purchased from Liufang Gas, Co., Ltd., China, and was purified by oxygen-trap columns and molecular sieves prior to use. IUD was synthesized according to the procedures described in previous literature.[
The copolymerization of ethylene and IUD was carried out in a Schlenk flask equipped with a mechanical stirrer with a total system volume of 120 mL. The flask was heated at 120 °C for 45 min under vacuum, then charged with nitrogen and evacuated to remove water and oxygen. After the flask was cooled to ambient temperature, it was placed in a water bath at a constant temperature of 25 °C. Ethylene gas was then pressurized to the flask (constant pressure of 0.1 MPa). IUD, toluene, and MAO were added sequentially. The rac-Et(Ind)2ZrCl2 complex (15 μmol) was dissolved in toluene (10 mL) and added to the flask to initiate polymerization. After stirring at 600 r/min for 20 min, the gas feed was stopped and the polymerization was terminated by air. The reaction mixture was rapidly poured into an acidic ethanol solution (5% HCl) for precipitation and the white solid was obtained after filtration. After full washing with ethanol, the resulting product was dried under vacuum at 80 °C to constant weight. The resultant copolymers were reacted with CH3SO3Na, CF3SO3K and LiTf2N, respectively, in an ion-exchange reaction, and then the PE ionomers bearing CH3SO3−, CF3SO3− and Tf2N− counterions, respectively were obtained.
The antibacterial properties of the copolymers and ionomers were demonstrated by the ability to suppress two of the most typical bacteria, Staphylococcus aureus (S. aureus ATCC 25923) and Escherichia coli (E. coli ATCC 25922). The sandwich method was used for examining the antibacterial properties, and the bacterial cultivation and testing procedures were detailed in published studies.[
1
The introduction of halogenated groups into non-polar polymer chains not only offered polar groups and structural diversity to PE, but also provided reaction sites for subsequent conversion to various functional groups. However, the halogenated monomers, i.e., ω-halo-α-olefins, may have a poisoning effect on the active centre. According to previous study, the intensity of the poisoning effect of halogen groups on the active centre followed the order: Cl > Br > I.[
The rac-Et(Ind)2ZrCl2 is a typical bridged metallocene catalyst for olefin polymerization. In previous studies, this catalyst has been demonstrated to efficiently catalyze ethylene polymerization and copolymerization with various comonomers.[
Fig 1 Synthesis of E/IUD copolymers and PE ionomers.
Entry | Sample | IUD b (mL) | Incorp. c (mol%) | Yield (g) | Activity d | Mw e (kDa) | MWD e | Tm f (°C) | ΔH f (J/g) | XC g (%) |
---|---|---|---|---|---|---|---|---|---|---|
1 | PE | / | / | 3.3 | 0.66 | 344 | 2.6 | 135.2 | 139.4 | 47.6 |
2 | E/IUD (2.9) | 0.9 | 2.9 | 5.1 | 1.02 | 279 | 2.5 | 128.3 | 78.9 | 26.9 |
3 | E/IUD (6.1) | 1.8 | 6.1 | 6.9 | 1.38 | 218 | 2.5 | 126.9 | 43.9 | 15.0 |
4 | E/IUD (9.1) | 2.7 | 9.1 | 8.3 | 1.66 | 176 | 2.2 | 124.6 | 31.6 | 10.8 |
5 | E/IUD (12.2) | 3.6 | 12.2 | 9.8 | 1.96 | 143 | 2.3 | 120.3 | 21.2 | 7.2 |
6 | E/IUD (15.7) | 4.5 | 15.7 | 10.4 | 2.08 | 125 | 2.2 | 114.5 | 5.9 | 2.0 |
7 | E/IUD (16.6) | 5.4 | 16.6 | 10.6 | 2.12 | 111 | 2.3 | ND | ND | ND |
a Polymerization conditions: Cat.Zr=15 μmol, ethylene pressure=0.1 MPa, n(Al)/n(Zr)=1000, Vtotal=120 mL, copolymerization at 25 °C for 20 min; b The feed of comonomer; c Incorporation of comonomer was determined by 13C-NMR; d Catalytic activity: 106 g·molZr−1·h−1; e The weight-average molecular weight and MWD were determined by high temperature GPC; f The melting temperature and melting enthalpy were determined by DSC; g The degree of crystallinity was calculated using the melting enthalpy. ND: Not determined.
Fig 1 13C-NMR spectrum of the copolymer (IUD 2.9%).
The copolymerization results of ethylene with IUD are summarized in
All copolymers showed a single melting temperature (Tm) in the DSC melting curves (Fig. S4 in ESI). With the increase of IUD content, the Tms of E/IUD copolymers decreased to disappear, and the melting enthalpies (ΔHms) decreased to zero, which were determined by the position and area of the melting peaks, respectively. This was because the insertion of IUD interfered with the crystalline structure and disrupted the structural regularity of the main chains, leading to a decrease in the crystallinity (XC) of the E/IUD copolymers. The glass transition temperatures (Tgs) of E/IUD copolymers gradually shifted to lower temperatures with the increase of IUD content (Fig. S5 in ESI). This was because of the decreased crystallinity and enhanced chain mobility caused by long side chains.
To investigate the effect of the ionic groups on copolymer properties, three typical counterions (CH3SO3−, CF3SO3−, Tf2N−) were chosen because of their easy availability and different properties.[
Fig 2 1H-NMR spectra of the copolymer (IUD 15.7%) and ionomers with different counterions.
To examine the completeness of the ion exchange, silver nitrate solution was used to test for the presence of iodide ions in the ionomers.[
The introduction of ionic groups in semi-crystalline polymers altered the values of Tm and XC. In order to explore the thermal and crystalline properties, the ionomers were carefully characterized by differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA), and wide-angle X-ray diffraction (WAXD). To clearly demonstrate the effect of different counterion types on the thermal properties, the ionomers with a relatively high ionic content of 12.2% were selected for discussion. The copolymer (IUD 12.2%) exhibited a melting peak at 120.3 °C, while the corresponding ionomers with CH3SO3−, CF3SO3−, and Tf2N− counterion showed a melting peak at 123.9, 123.1, and 122.8 °C, respectively (
Fig 3 DSC melting curves of the copolymer (IUD 12.2%) and the corresponding ionomers.
The above results indicated that the introduction of ionic groups led to the increase of Tm, which was attributed to the additional ionic interactions and the improved intermolecular forces. The ionomers with the same ionic content but different counterion types displayed different Tm, among which those bearing CH3SO3− counterion had the highest Tm due to their strongest ionic interaction.
The effect of different counterions on the crystalline behavior of the copolymers and ionomers was investigated by WAXD (Fig. S6 in ESI). Two crystalline peaks at 2θ=21.6° and 24.0° corresponding to 110 and 200 spacings and one amorphous peak at 2θ=19.6° were observed for all the copolymers and ionomers.[
After ionization, the Tg values of the ionomers shifted from −27.8 °C of the copolymer (IUD 12.2%) to −4.9 (CH3SO3−), −13.4 (CF3SO3−), and −20.2 °C (Tf2N−), respectively (
Fig 4 Typical DMA curves of the E/IUD copolymer and ionomers.
The effect of ionic content on Tg of the ionomers bearing the same counterion was also considered. For the ionomers bearing CF3SO3−, Tg varied from −13.4 °C to −6.4 °C as the ionic content varied from 12.2% to 6.1%. The same trend was observed for the ionomers bearing CH3SO3− and Tf2N− counterions. An increase in ionic content also meant an increase in side chain content, thus a greater number of side chains would lead to decreased crystallinity and enhanced chain mobility, and consequently decreased Tg.
To investigate the effect of the introduction of ionic groups on the mechanical properties, the stress-strain behaviors of the copolymers and ionomers were tested. For E/IUD copolymers, both the stress-at-break and elongation-at-break of the copolymers decreased with increasing IUD content. As presented in Fig. S7 (in ESI), the copolymer (IUD 2.9%) exhibited a stress-at-break of 20.5 MPa and an elongation-at-break of 900%. As the content of IUD reached 12.2%, the stress-at-break decreased to 2.3 MPa and the elongation-at-break decreased to 152%. On the one hand, the decrease in stress-at-break was due to the disruption of the crystalline structure of PE backbone by the incorporated IUD units. On the other hand, the decrease in elongation-at-break of the copolymers was attributed to the decreased Mw with IUD incorporation, because lower Mw weakened the chain entanglement that favored the ductility of polymers.
Fig 5 Stress-strain curves of (a) the copolymer (IUD 6.1%) and ionomers, and (b) the copolymer (IUD 12.2%) and ionomers.
The results discussed above indicated that the introduction of ionic groups remarkably affected the mechanical properties of the copolymers. This can be explained by the ability of ionic groups to form ionic aggregates in the polymer matrix, which act as physical cross-links to strengthen the intermolecular forces.[
The effect of counterion species on the mechanical properties of the ionomers has also been considered. The stress-at-break values of the ionomers with CH3SO3− ranged from 17.9 MPa to 25.6 MPa, and the elongation-at-break values ranged from 445% to 536%. The stress-at-break values of the ionomers with CF3SO3− ranged from 14.6 MPa to 24.2 MPa, and the elongation-at-break values ranged from 549% to 716%. The stress-at-break values of the ionomers with Tf2N− ranged from 7.8 MPa to 21.2 MPa, and the elongation-at-break values ranged from 681% to 847%. These results suggested that counterion type considerably impact the mechanical properties of the ionomers at the same ionic content. The stress-at-break values of the ionomers exhibited the following order: CH3SO3− > CF3SO3− > Tf2N−, while the elongation-at-break values showed the opposite trend. The trend in stress-at-break was consistent with the previously reported binding intensity of the counterions with the imidazole cation.[
Ionomers have been reported to play an important role in biomedical applications such as antibacterial material. To verify the antibacterial properties of the prepared copolymers and ionomers, the sandwich method in which a bacterial solution was coated in the middle of two polymer membranes was employed for testing. S. aureus, a typical Gram-positive bacterium, and E. coli, a typical Gram-negative bacterium, were selected for antibacterial test.[
The antibacterial activities of the ionomers were also considered. For imidazolium-based ionomers with the same ionic content, the ionomers bearing Tf2N− displayed the best antibacterial activities against both S. aureus and E. coli (Fig. S12 in ESI). The ionomers bearing Tf2N− were chosen to discuss the effect of ionic content on the antibacterial properties of the ionomers. The ionomers with different ionic contents exhibited different antibacterial activities (
Fig 6 (a) Photographs of bacterial colonies and (b) survival rates of S. aureus and E. coli after co-cultivation with the ionomers bearing Tf2N− for 4 h.
The effect of counterion type on the antibacterial activities of the ionomers was further investigated. The ionomers containing 9.1% ionic group but different counterions were chosen for discussion. The ionomers with different counterion types exhibited different antibacterial activities (
Fig 7 (a) Photographs of bacterial colonies and (b) survival rates of S. aureus and E. coli after co-cultivation with the copolymer (IUD 9.1%) and the corresponding ionomers for 4 h.
Among three kinds of imidazolium-based ionomers, the ionomers bearing Tf2N− exhibited the best antibacterial activities against S. aureus and E. coli. The Tf2N− counterion had the weakest ionic interaction with the imidazole cation, thus the imidazole cation was more likely to interact electrostatically with negatively charged cell membranes rather than Tf2N−. In contrast, the interaction between CH3SO3− and imidazole cation was too strong, preventing the imidazole cation group from effectively interacting with the cell membrane. The above results demonstrated the advantages of imidazolium-based ionomers in efficient and broad-spectrum antibacterial activity and their potential application as antibacterial materials.
In conclusion, a series of imidazolium-based PE ionomers bearing different types of counterions were efficiently prepared. The ionomers were obtained from E/IUD copolymers with iodine groups in the side chains via nucleophilic substitution and ion exchange reactions. The ionomers exhibited elevated Tm and Tg compared with the E/IUD copolymers, which was attributed to ionic aggregation. The stress-at-break (7.8−25.6 MPa) and the elongation-at-break (445%−847%) of the ionomers could be adjusted over a wide range by changing the counterion species and the ionic group contents. The stress-at-break values of ionomers exhibited the following order: CH3SO3− > CF3SO3− > Tf2N−, while the elongation-at-break values showed the opposite trend. The ionomers showed excellent antibacterial activities against S. aureus and E. coli. The antibacterial ability of ionomers with the same ionic content but different counterions displayed the following order: CH3SO3− < CF3SO3− < Tf2N−. The ionomers bearing Tf2N− exhibited antibacterial activities >99% against both S. aureus and E. coli when ionic content reached 9.1%.
This work not only provided a practicable approach for the synthesis of PE ionomers, but also demonstrated the great potential of PE ionomers in biomedical applications. Furthermore, the PE ionomers also showed potential applications in the field of thermoplastic elastomers due to their reversible interactions including crystallization and ionic cross-linking. Related work is in progress.
Qiao, J. L.; Guo, M. F.; Wang, L. S.; Liu, D. B.; Zhang, X. F.; Yu, L. Q.; Song, W. B.; Liu, Y. Q. Recent advances in polyolefin technology.Polym. Chem.2011,2, 1611−1623.. [Baidu Scholar]
Jubinville, D.; Esmizadeh, E.; Saikrishnan, S.; Tzoganakis, C.; Mekonnen, T. A comprehensive review of global production and recycling methods of polyolefin (PO) based products and their post-recycling applications.Sustain. Mater. Technol.2020,25, e00188.. [Baidu Scholar]
Chen, E. Y. X. Coordination polymerization of polar vinyl monomers by single-site metal catalysts.Chem. Rev.2009,109, 5157−5214.. [Baidu Scholar]
Ittel, S. D.; Johnson, L. K.; Brookhart, M. Late-metal catalysts for ethylene homo- and copolymerization.Chem. Rev.2000,100, 1169−1204.. [Baidu Scholar]
Wang, F.; Pan, L.; Tuskaev, V. A.; Gagieva, S. C.; Li, Y. S. Phosphine/benzocyclone-based neutral nickel catalysts for ethylene polymerization and copolymerization with polar monomers.Chinese J. Polym. Sci. 2024 ,42, 202−212.. [Baidu Scholar]
Wang, W. B.; Zou, C.; Chen, C. L. Synthesis of pyrene based α-diimide nickel catalysts for ethylene polymerization/ copolymerization.Acta Polymerica Sinica(in Chinese) 2023 ,54, 1697–1707.. [Baidu Scholar]
Wang, H. B.; Yang, Y.; Nishiura, M.; Higaki, Y.; Takahara, A.; Hou, Z. M., Synthesis of self-healing polymers by scandium-catalyzed copolymerization of ethylene and anisylpropylenes.J. Am. Chem. Soc. 2019 ,141, 3249–3257.. [Baidu Scholar]
Dai, S. Y.; Chen, C. L., Direct synthesis of functionalized high-molecular-weight polyethylene by copolymerization of ethylene with polar monomers.Angew. Chem. Int. Ed. 2016 ,55, 13281–13285.. [Baidu Scholar]
Soshnikov, I. E.; Chen, C. L.; Bryliakov, K. P. Ni catalyzed ethylene copolymerization with polar monomers.Sci. China: Chem.2019,62, 653−654.. [Baidu Scholar]
Eisenberg, A.; Kim, J. S.; Ratner, M. Introduction to ionomers.Phys. Today1999,52, 68.. [Baidu Scholar]
Lin, H.; Ramos, L.; Hwang, J.; Zhu, T.; Hossain, M. W.; Wang, Q.; Garashchuk, S.; Tang, C. Main-chain cobaltocenium-containing ionomers for alkaline anion-exchange membranes.Macromolecules2023,56, 6375−6384.. [Baidu Scholar]
D'Auria, S.; Pourrahimi, A. M.; Favero, A.; Neuteboom, P.; Xu, X.; Haraguchi, S.; Bek, M.; Kádár, R.; Dalcanale, E.; Pinalli, R.; Müller, C.; Vachon, J. Polyethylene based ionomers as high voltage insulation materials.Adv. Funct. Mater.2023,33, 2301878.. [Baidu Scholar]
Chen, N. J.; Lee, Y. M. Anion exchange polyelectrolytes for membranes and ionomers.Prog. Polym. Sci.2021,113, 101345.. [Baidu Scholar]
Zou, C.; Zhang, H.; Tan, C.; Cai, Z. G. Polyolefins with intrinsic antimicrobial properties.Macromolecules2021,54, 64−70.. [Baidu Scholar]
Qin, L. D.; Wang, X. Y.; Mahmood, Q.; Yu, Z. X.; Wang, Y. Z.; Zou, S.; Liang, T. L.; Sun, W. H. High-performanceα-diimine nickel complexes for facile access of PE elastomers with exceptional material properties.Chinese J. Polym. Sci.2024,42, 620−635.. [Baidu Scholar]
Chen, Z.; Li, J. F.; Tao, W. J.; Sun, X. L.; Yang, X. H.; Tang, Y. Copolymerization of ethylene with functionalized olefins by [ONX]titanium complexes.Macromolecules2013,46, 2870−2875.. [Baidu Scholar]
Rodriguez, B. A.; Delferro, M.; Marks, T. J. Bimetallic effects for enhanced polar comonomer enchainment selectivity in catalytic ethylene polymerization.J. Am. Chem. Soc.2009,131, 5902−5919.. [Baidu Scholar]
Berkefeld, A.; Mecking, S. Coordination copolymerization of polar vinyl monomers H2C=CHX.Angew. Chem. Int. Ed.2008,47, 2538−2542.. [Baidu Scholar]
Xiang, P.; Ye, Z. B. Hyperbranched polyethylene ionomers containing cationic tetralkylammonium ions synthesized by pd–diimine-catalyzed direct ethylene copolymerization with ionic liquid comonomers.Macromolecules2015,48, 6096−6107.. [Baidu Scholar]
Kostalik, H. A.; Clark, T. J.; Robertson, N. J.; Mutolo, P. F.; Longo, J. M.; Abruña, H. D.; Coates, G. W. Solvent processable tetraalkylammonium-functionalized polyethylene for use as an alkaline anion exchange membrane.Macromolecules2010,43, 7147−7150.. [Baidu Scholar]
Wang, X. Y.; Wang, Y. X.; Li, Y. S.; Pan, L. Convenient syntheses and versatile functionalizations of isotactic polypropylene containing plentiful pendant styrene groups with high efficiency.Macromolecules2015,48, 1991−1998.. [Baidu Scholar]
Lin, W. T.; Shao, Z.; Dong, J. Y.; Chung, T. C. M. Cross-linked polypropylene prepared by PP copolymers containing flexible styrene groups.Macromolecules2009,42, 3750−3754.. [Baidu Scholar]
Dong, J. Y.; Hu, Y. L. Design and synthesis of structurally well-defined functional polyolefinsviatransition metal-mediated olefin polymerization chemistry.Coord. Chem. Rev.2006,250, 47−65.. [Baidu Scholar]
Aitken, B. S.; Buitrago, C. F.; Heffley, J. D.; Lee, M.; Gibson, H. W.; Winey, K. I.; Wagener, K. B. Precision ionomers: synthesis and thermal/mechanical characterization.Macromolecules2012,45, 681−687.. [Baidu Scholar]
Zhang, M.; Kim, H. K.; Chalkova, E.; Mark, F.; Lvov, S. N.; Chung, T. C. M. New polyethylene based anion exchange membranes (PE-AEMs) with high ionic conductivity.Macromolecules2011,44, 5937−5946.. [Baidu Scholar]
Jiang, Y.; Zhang, Z.; Jiang, H. Q.; Wang, Q. Y.; Li, S. H.; Cui, D. M. Polar group-promoted copolymerization of ethylene with polar olefins.Macromolecules2023,56, 1547−1553.. [Baidu Scholar]
Paxton, N. C.; Allenby, M. C.; Lewis, P. M.; Woodruff, M. A. Biomedical applications of polyethylene.Eur. Polym. J.2019,118, 412−428.. [Baidu Scholar]
Jenke, D. R. Extractables and leachables considerations for prefilled syringes.Expert. Opin. Drug. Del.2014,11, 1591−1600.. [Baidu Scholar]
Bauer, S.; Schmuki, P.; von der Mark, K.; Park, J. Engineering biocompatible implant surfaces.Prog. Mater. Sci.2013,58, 261−326.. [Baidu Scholar]
Brynda, E.; Houska, M.; Novikova, S. P.; Dobrova, N. B. Polyethylene/hydrophilic polymer blends for biomedical applications.Biomaterials1987,8, 57−60.. [Baidu Scholar]
Chen, M. X.; Dai, J. Y.; Zhang, L. Y.; Wang, S. P.; Liu, J. K.; Wu, Y. G.; Ba, X. W.; Liu, X. Q. The role of renewable protocatechol acid in epoxy coating modification: significantly improved antibacterial and adhesive properties.Chinese J. Polym. Sci.2024,42, 63−72.. [Baidu Scholar]
Appendini, P.; Hotchkiss, J. H. Review of antimicrobial food packaging.Innov. Food Sci. Emerg.2002,3, 113−126.. [Baidu Scholar]
Qin, L.; Sharique, M.; Tambar, U. K. Controllable, sequential, and stereoselective C–H allylic alkylation of alkenes.J. Am. Chem. Soc.2019,141, 17305−17313.. [Baidu Scholar]
Zhang, Y.; Guo, J. J.; Zhang, K. Y.; Ma, X. T.; Cao, D. F.; Bai, S.; Yuan, X. Y.; Pan, L.; Sun, J.; Li, Y. S. Robust ionic cyclic olefin polymers with excellent transparency, barrier properties, and antibacterial properties.Macromolecules2023,56, 4371−4385.. [Baidu Scholar]
Wang, X. Y.; Long, Y. Y.; Wang, Y. X.; Li, Y. S. Insights into propylene/ω-halo-α-alkenes copolymerization promoted byrac-Et(Ind)2ZrCl2and (pyridyl-amido)hafnium catalysts.J. Polym. Sci., Part A: Polym. Chem.2014,52, 3421−3428.. [Baidu Scholar]
Wang, X. Y.; Wang, Y. X.; Shi, X. C.; Liu, J. Y.; Chen, C. L.; Li, Y. S. Syntheses of well-defined functional isotactic poly- propylenes via efficient copolymerization of propylene withω-halo-α-alkenes by post-metallocene hafnium catalyst.Macromolecules2014,47, 552−559.. [Baidu Scholar]
Mehdiabadi, S.; Soares, J. B. P. In-depth investigation of ethylene solution polymerization kinetics withrac-Et(Ind)2ZrCl2/MAO.Macromol. Chem. Phys.2013,214, 246−262.. [Baidu Scholar]
Liu, S. J.; Yao, Z.; Cao, K.; Li, B. G.; Zhu, S. P. Preparation of polar ethylene–norbornene copolymers by metallocene terpolymerization with triisobutylaluminium-protected but-3-en -1-ol.Macromol. Rapid Commun.2009,30, 548−553.. [Baidu Scholar]
Meng, Q. Q.; Wang, B.; Pan, L.; Li, Y. S.; Ma, Z. Synthesis and properties of isotactic polypropylene ionomers containing ammonium ions.Acta Polymerica Sinica(in Chinese) 2017 , 1762−1772.. [Baidu Scholar]
Cui, J.; Nie, F. M.; Yang, J. X.; Pan, L.; Ma, Z.; Li, Y. S., Novel imidazolium-based poly(ionic liquid)s with different counterions for self-healing.J. Mater. Chem. A 2017 ,5, 25220−25229.. [Baidu Scholar]
Zhang, J.; Mao, X. H.; Ma, Z.; Pan, L.; Wang, B.; Li, Y. S. High-performance polyethylene-ionomer-based thermoplastic elastomers exhibiting counteranion-mediated mechanical properties.Macromolecules2023,56, 4219−4230.. [Baidu Scholar]
Pan, L.; Liu, Y. G.; Zhang, K. Y.; Bo, S. Q.; Li, Y. S. Investigation of the effect of branched structure on the performances of the copolymers synthesized from ethylene andα-olefin withrac-Et(Ind)2ZrCl2/MMAO catalyst system.Polymer2006,47, 1465−1472.. [Baidu Scholar]
Eisenberg, A. Clustering of ions in organic polymers. A theoretical approach.Macromolecules1970,3, 147−154.. [Baidu Scholar]
Eisenberg, A.; Hird, B.; Moore, R. B. A new multiplet-cluster model for the morphology of random ionomers.Macromolecules1990,23, 4098−4107.. [Baidu Scholar]
Wakabayashi, K.; Register, R. A. Morphological origin of the multistep relaxation behavior in semicrystalline ethylene/ methacrylic acid ionomers.Macromolecules2006,39, 1079−1086.. [Baidu Scholar]
Choi, U. H.; Lee, M.; Wang, S.; Liu, W.; Winey, K. I.; Gibson, H. W.; Colby, R. H. Ionic conduction and dielectric response of poly(imidazolium acrylate) ionomers.Macromolecules2012,45, 3974−3985.. [Baidu Scholar]
Bates, C. M.; Maher, M. J.; Janes, D. W.; Ellison, C. J.; Willson, C. G. Block copolymer lithography.Macromolecules 2014 ,47, 2−12.. [Baidu Scholar]
Richter, M. F.; Drown, B. S.; Riley, A. P.; Garcia, A.; Shirai, T.; Svec, R. L.; Hergenrother, P. J. Predictive rules for compound accumulation yield a broad-spectrum antibiotic.Nature2017,545, 299−304.. [Baidu Scholar]
Tong, S. Y. C.; Davis, J. S.; Eichenberger, E.; Holland, T. L.; Fowler, V. G.Staphylococcus aureusinfections: epidemiology, pathophysiology, clinical manifestations, and management.Clin. Microbiol. Rev. 2015 ,28, 603−661.. [Baidu Scholar]
Chung, Y. C.; Chen, C. Y. Antibacterial characteristics and activity of acid-soluble chitosan.Bioresour. Technol.2008,99, 2806−2814.. [Baidu Scholar]
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