Cross-linked Polymers

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Chemistry".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 30136

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Institute of Chemical Technology and Engineering, Faculty of Chemical Technology, Poznan University of Technology, Berdychowo 4, PL-60965 Poznan, Poland
Interests: biopolymers; lignin chemistry; synthesis, characterization and applications of advanced functional materials; hybrid materials, biomaterials; polymer composites, biocomposites; chemical modification of synthetic and natural polymers; application of ligno-cellulosic materials in polymer chemistry; (bio)additives and eco-friendly fillers
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Department of Polymer Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University in Lublin, M. Curie-Sklodowska Sq. 3, PL-20031 Lublin, Poland
Interests: synthesis of new monomers and polymers; chemical modification of synthetic and natural polymers; synthesis of biocomposites; application of ligno-cellulosic materials in polymer chemistry; synthesis of porous polymers in the form of microspheres; investigations of the porous structure of polymeric materials; synthesis of novel polymer-based adsorbents for water treatment; photochemistry; physico-chemical, thermal and mechanical studies of polymers; synthesis of polymeric blends; synthesis of hybrid materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

DearColleagues,

Polymers are a very diverse group, which includes many different types. Cross-linked polymers are one of the most important. These connections can be found in both synthetic and naturally occurring polymers. The cross-linking of polymers significantly modifies their physico-chemical properties, really increasing their everyday utility. The polymeric networks resulting from covalent bonds between polymer chains are found in daily products.

Chemical cross-linking allows the obtaining of a more rigid structure, that is mechanically and chemically resistant, and potentially a better-defined shape. Numerous functional materials have been developed using the application of crosslinking polymers. We can find them, e.g., in soft contact lenses, automobile tires, protective coatings, high-performance adhesives, polymeric sorbents or epoxy-based materials. Cross-linked polymers successfully replace naturally occurring materials, such as wood, ceramics, metal or natural rubber.

The goal of the presented Special Issue in Polymers is to share the most significant issues associated with the mentioned research topics, as well as to elucidate the important trends for the near future.

Therefore, we invite everyone to submit their publications to a Special Edition dedicated to crosslinked polymers.

Dr. Łukasz Klapiszewski
Dr. Beata Podkościelna
Guest Editors

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Keywords

  • Cross-linking polymers
  • polymeric networks
  • bulk copolymers
  • cross-linking agents
  • epoxy resins
  • chemical resistant materials
  • composites

Published Papers (11 papers)

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Research

20 pages, 2855 KiB  
Article
Synthesis and Characterization of Polymeric Blends Containing Polysulfone Based on Cyclic Bisphenol
by Mateusz Gargol and Beata Podkościelna
Polymers 2022, 14(15), 3148; https://doi.org/10.3390/polym14153148 - 02 Aug 2022
Cited by 1 | Viewed by 1883
Abstract
The elaboration of the composition and methods of preparation of new types of materials is an important issue from the plastics industry’s point of view. The paper presents the polysulfone synthesis based on 4,4′-cyclohexylidenebisphenol (bisphenol Z). This compound was used (in an amount [...] Read more.
The elaboration of the composition and methods of preparation of new types of materials is an important issue from the plastics industry’s point of view. The paper presents the polysulfone synthesis based on 4,4′-cyclohexylidenebisphenol (bisphenol Z). This compound was used (in an amount of 5 or 10 wt.% sample) for the synthesis and characterization of new polymeric blends based on the two different acrylic resins (EB-150 and EB-600) and the active solvent N-vinyl-2-pyrrolidone (NVP). The weight ratio of the used resin to solvent was 1:2; 1:1 or 2:1. These new materials were obtained applying the photoinitiated free radical polymerization with 2,2-dimethoxy-2-phenyloacetophenone as a photoinitiator used in an amount of 1 wt.%. Six polymeric blends and six copolymers without polysulfone were cured by this method. By means of ATR/FT-IR (Attenuated Total Reflection–Fourier Transform Infrared) spectroscopy the chemical structure of the synthesized polysulfone was proved. The effect of the presence of the polysulfone presence on the thermal properties of the obtained blends was analyzed by means of thermogravimetry and differential thermogravimetry (TG/DTG), as well as differential scanning calorimetry (DSC). Moreover, the dynamic mechanical studies (DMA) of these materials were also carried out, demonstrating which of the materials showed the influence of the percentage of polysulfone on the selected properties in the blended- and parent-copolymers samples. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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10 pages, 1202 KiB  
Article
Electrical Conductivities of Narrow-Bandgap Polymers with Two Types of π-Conjugated Post-Crosslinking
by Hao-xuan Guo, Hiroshi Takahara, Yusuke Imai and Hiroyuki Aota
Polymers 2022, 14(12), 2472; https://doi.org/10.3390/polym14122472 - 17 Jun 2022
Cited by 4 | Viewed by 1714
Abstract
Bandgap energy is one of the most important properties for developing electronic devices because of its influence on the electrical conductivity of substances. Many methods have been developed to control bandgap, one of which is the realization of conducting polymers using narrow-bandgap polymers; [...] Read more.
Bandgap energy is one of the most important properties for developing electronic devices because of its influence on the electrical conductivity of substances. Many methods have been developed to control bandgap, one of which is the realization of conducting polymers using narrow-bandgap polymers; however, the preparation of these polymers is complex. In this study, water-soluble, narrow-bandgap polymers with reactive groups were prepared by the addition–condensation reaction of pyrrole (Pyr), benzaldehyde-2-sulfonic acid sodium salt (BS), and aldehyde-containing reactive groups (aldehyde and pyridine) for post-crosslinking. Two types of reactions, aldehyde with p-phenylenediamine and pyridine with 1,2-dibromoethylene, were carried out for the π-conjugated post-crosslinking between polymers. The polymers were characterized by proton nuclear magnetic resonance (1H-NMR), thermogravimetric/differential thermal analysis (TG/DTA), UltraViolet-Visible-Near InfraRed spectroscopy (UV-Vis-NIR), and other analyses. The bandgaps of the polymers, calculated from their absorption, were less than 0.5 eV. Post-crosslinking prevents resolubility and develops electron-conducting routes between the polymer chains for π-conjugated systems. Moreover, the post-crosslinked polymers maintain their narrow bandgaps. The electrical conductivities of the as-prepared polymers were two orders of magnitude higher than those before the crosslinking. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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16 pages, 14866 KiB  
Article
Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study
by Francesca Nardelli, Lucia Calucci, Elisa Carignani, Silvia Borsacchi, Mattia Cettolin, Marco Arimondi, Luca Giannini, Marco Geppi and Francesca Martini
Polymers 2022, 14(4), 767; https://doi.org/10.3390/polym14040767 - 16 Feb 2022
Cited by 9 | Viewed by 3085
Abstract
The characterization of the structural and dynamic properties of rubber networks is of fundamental importance in rubber science and technology to design materials with optimized mechanical properties. In this work, natural and isoprene rubber networks obtained by curing at three different temperatures (140, [...] Read more.
The characterization of the structural and dynamic properties of rubber networks is of fundamental importance in rubber science and technology to design materials with optimized mechanical properties. In this work, natural and isoprene rubber networks obtained by curing at three different temperatures (140, 150, and 170 °C) and three different sulfur contents (1, 2, and 3 phr) in the presence of a 3 phr accelerator were studied using a combination of low-field time-domain NMR (TD-NMR) techniques, including 1H multiple-quantum experiments for the measurement of residual dipolar couplings (Dres), the application of the Carr–Purcell–Meiboom–Gill pulse sequence for the measurement of the transverse magnetization decay and the extraction of 1H T2 relaxation times, and the use of field cycling NMR relaxometry for the determination of T1 relaxation times. The microscopic properties determined by TD-NMR experiments were discussed in comparison with the macroscopic properties obtained using equilibrium swelling, moving die rheometer, and calorimetric techniques. The obtained correlations between NMR observables, crosslink density values, maximum torque values, and glass transition temperatures provided insights into the effects of the vulcanization temperature and accelerator/sulfur ratio on the structure of the polymer networks, as well as on the effects of crosslinking on the segmental dynamics of elastomers. Dres and T2 were found to show linear correlations with the crosslink density determined by equilibrium swelling, while T1 depends on the local dynamics of polymer segments related to the glass transition, which is also affected by chemical modifications of the polymer chains occurring during vulcanization. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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15 pages, 3608 KiB  
Article
Catalytic Polymerization of Phthalonitrile Resins by Carborane with Enhanced Thermal Oxidation Resistance: Experimental and Molecular Simulation
by Yuxiang Jia, Xiaojun Bu, Junyu Dong, Quan Zhou, Min Liu, Fang Wang and Maoyuan Wang
Polymers 2022, 14(1), 219; https://doi.org/10.3390/polym14010219 - 05 Jan 2022
Cited by 13 | Viewed by 3507
Abstract
Biphenyl phthalonitrile (BPh) resins with good thermal and thermo-oxidative stability demonstrate great application potential in aerospace and national defense industries. However, BPh monomer has a high melting point, poor solubility, slow curing speed and high curing temperature. It is difficult to control the [...] Read more.
Biphenyl phthalonitrile (BPh) resins with good thermal and thermo-oxidative stability demonstrate great application potential in aerospace and national defense industries. However, BPh monomer has a high melting point, poor solubility, slow curing speed and high curing temperature. It is difficult to control the polymerization process to obtain the resins with high performance. Here, a BPh prepolymer (BPh-Q) was prepared by reacting 1,7-bis(hydroxymethyl)-m-carborane (QCB) with BPh monomers. The BPh-Q exhibited much better solubility, faster curing speed and lower curing temperature compared with pure BPh and BPh modified with bisphenol A (BPh-B, a common prepolymer of BPh). Thus, the polymerization process of BPh was greatly accelerated at a low temperature, resulting in a BPh resin with enhanced thermostability and oxidation resistance. The experimental and theoretical models revealed the promotion effect of B-H bond on the curing reaction of phthalonitrile via Markovnikov addition reaction due to the special steric structure of carborane. This study provided an efficient method to obtain low-temperature curing phthalonitrile resins with high thermal and thermo-oxidative resistance, which would be potentially useful for the preparation of high-performance cyanide resin-based composites. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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10 pages, 2332 KiB  
Article
Effects of Crosslinking and Silicone Coupling Agent on Properties of EVA Composite Hot Melt Adhesive
by Zijin Wu, Yonggang Shangguan, Chunhui Zhang and Qiang Zheng
Polymers 2021, 13(23), 4101; https://doi.org/10.3390/polym13234101 - 25 Nov 2021
Cited by 9 | Viewed by 3218
Abstract
In order to improve the bonding performance, EVA composite hot melt adhesives were prepared by introducing crosslinking agent and silane coupling agent in this paper. A binary EVA resin blend as the base resin with appropriate viscosity and tensile shear strength was selected [...] Read more.
In order to improve the bonding performance, EVA composite hot melt adhesives were prepared by introducing crosslinking agent and silane coupling agent in this paper. A binary EVA resin blend as the base resin with appropriate viscosity and tensile shear strength was selected as hot melt adhesive. The effects of crosslinking agent and silane coupling agent on the properties of ethylene/vinyl acetate (EVA) composite hot melt adhesive were studied. By investigating the preparation and curing conditions of hot melt adhesive and the properties of hot melt adhesive after the introduction of dicumyl peroxide (DCP), the optimum temperature and dosage of DCP and its influence on the properties were determined. It was found that the tensile shear strength of hot melt adhesive increased from 0.247 MPa to 0.726 MPa when 2 phr DCP and 5 phr KH570 were added at the same time. The tensile strength and tensile shear strength of hot melt adhesive are only slightly improved when silicone coupling agents with different functional groups are added to EVA composite hot melt adhesive. However, it was found that excessive silane coupling agent would significantly reduce the tensile strength and shear peel strength of the material. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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19 pages, 5499 KiB  
Article
Cross-Linking and Evaluation of the Thermo-Mechanical Behavior of Epoxy Based Poly(ionic Liquid) Thermosets
by Florian Wanghofer, Archim Wolfberger, Markus Wolfahrt and Sandra Schlögl
Polymers 2021, 13(22), 3914; https://doi.org/10.3390/polym13223914 - 12 Nov 2021
Cited by 5 | Viewed by 2422
Abstract
Poly(ionic liquids) (PILs) and ionenes are polymers containing ionic groups in their repeating units. The unique properties of these polymers render them as interesting candidates for a variety of applications, such as gas separation membranes and polyelectrolytes. Due to the vast number of [...] Read more.
Poly(ionic liquids) (PILs) and ionenes are polymers containing ionic groups in their repeating units. The unique properties of these polymers render them as interesting candidates for a variety of applications, such as gas separation membranes and polyelectrolytes. Due to the vast number of possible structures, numerous synthesis protocols to produce monomers with different functional groups for task-specific PILs are reported in literature. A difunctional epoxy-IL resin was synthesized and cured with multifunctional amine and anhydride hardeners and the thermal and thermomechanical properties of the networks were assessed via differential scanning calorimetry and dynamic mechanical analysis. By the selection of suitable hardeners, the glass transition onset temperature (Tg,onset) of the resulting networks was varied between 18 °C and 99 °C. Copolymerization of epoxy-IL with diglycidyl ether of bisphenol A (DGEBA) led to a further increase of the Tg,onset. The results demonstrate the potential of epoxy chemistry for tailorable PIL networks, where the hardener takes the place of the ligands without requiring an additional synthesis step and can be chosen from a broad range of commercially available compounds. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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16 pages, 6367 KiB  
Article
Dielectric Permittivity, AC Electrical Conductivity and Conduction Mechanism of High Crosslinked-Vinyl Polymers and Their Pd(OAc)2 Composites
by Elsayed Elbayoumy, Nasser A. El-Ghamaz, Farid Sh. Mohamed, Mostafa A. Diab and Tamaki Nakano
Polymers 2021, 13(17), 3005; https://doi.org/10.3390/polym13173005 - 05 Sep 2021
Cited by 14 | Viewed by 2922
Abstract
Semiconductor materials based on metal high crosslinked-vinyl polymer composites were prepared through loading of Pd(OAc)2 on both Poly(ethylene-1,2-diyl dimethacrylate) (poly(EDMA)) and poly(ethylene-1,2-diyl dimethacrylate-co-methyl methacrylate) (Poly(EDMA-co-MMA)). The thermochemical properties for both poly(EDMA) and poly(EDMA-co-MMA) were investigated by thermal gravimetric analysis TGA technique. The [...] Read more.
Semiconductor materials based on metal high crosslinked-vinyl polymer composites were prepared through loading of Pd(OAc)2 on both Poly(ethylene-1,2-diyl dimethacrylate) (poly(EDMA)) and poly(ethylene-1,2-diyl dimethacrylate-co-methyl methacrylate) (Poly(EDMA-co-MMA)). The thermochemical properties for both poly(EDMA) and poly(EDMA-co-MMA) were investigated by thermal gravimetric analysis TGA technique. The dielectric permittivity, AC electrical conductivity and conduction mechanism for all the prepared polymers and their Pd(OAc)2 composites were studied. The results showed that the loading of polymers with Pd(OAc)2 led to an increase in the magnitudes of both the dielectric permittivity and AC electrical conductivity (σac). The value of σac increased from 1.38 × 10−5 to 5.84 × 10−5 S m−1 and from 6.40 × 10−6 to 2.48 × 10−5 S m−1 for poly(EDMA) and poly(EDMA-co-MMA), respectively, at 1 MHz and 340 K after loading with Pd(OAc)2. Additionally, all the prepared polymers and composites were considered as semiconductors at all the test frequencies and in the temperature range of 300–340 K. Furthermore, it seems that a conduction mechanism for all the samples could be Quantum Mechanical Tunneling (QMT). Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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15 pages, 27528 KiB  
Article
Reaction-Induced Phase Separation and Morphology Evolution of Benzoxazine/Epoxy/Imidazole Ternary Blends
by Jun Yue, Honglei Wang, Qian Zhou and Pei Zhao
Polymers 2021, 13(17), 2945; https://doi.org/10.3390/polym13172945 - 31 Aug 2021
Cited by 3 | Viewed by 2122
Abstract
Introducing multiphase structures into benzoxazine (BOZ)/epoxy resins (ER) blends via reaction-induced phase separation has proved to be promising strategy for improving their toughness. However, due to the limited contrast between two phases, little information is known about the phase morphological evolutions, a fundamental [...] Read more.
Introducing multiphase structures into benzoxazine (BOZ)/epoxy resins (ER) blends via reaction-induced phase separation has proved to be promising strategy for improving their toughness. However, due to the limited contrast between two phases, little information is known about the phase morphological evolutions, a fundamental but vital issue to rational design and preparation of blends with different phase morphologies in a controllable manner. Here we addressed this problem by amplifying the difference of polymerization activity (PA) between BOZ and ER by synthesizing a low reactive phenol-3,3-diethyl-4,4′-diaminodiphenyl methane based benzoxazine (MOEA-BOZ) monomer. Results indicated that the PA of ER was higher than that of BOZ. The use of less reactive MOEA-BOZs significantly enlarged their PA difference with ER, and thus increased the extent of phase separation and improved the phase contrast. Phase morphologies varied with the content of ER. As for the phase morphological evolution, a rapid phase separation could occur in the initial homogeneous blends with the polymerization of ER, and the phase morphology gradually evolved with the increase in ER conversion until the ER was used up. The polymerization of ER is not only the driving-force for the phase separation, but also the main factor influencing the phase morphologies. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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20 pages, 11053 KiB  
Article
Conjugated Polymer Films Having a Uniaxial Molecular Orientation and Network Structure Prepared by Electrochemical Polymerization in Liquid Crystals
by Jiuchao Dong, Shigeki Nimori and Hiromasa Goto
Polymers 2021, 13(15), 2425; https://doi.org/10.3390/polym13152425 - 23 Jul 2021
Cited by 2 | Viewed by 2182
Abstract
A new method for fabricating conjugated polymer films was developed using electrochemical polymerization in liquid crystals and magnetic orientation. A uniaxial main chain orientation and a crosslinked network structure were achieved with this method. By employing eight types of monomers, the influence of [...] Read more.
A new method for fabricating conjugated polymer films was developed using electrochemical polymerization in liquid crystals and magnetic orientation. A uniaxial main chain orientation and a crosslinked network structure were achieved with this method. By employing eight types of monomers, the influence of the crosslinking for the film was investigated. The crosslinking was found to improve the solvent resistance of the conjugated polymer films. This new method is expected to be useful in various applications, such as high-powered organic electronic devices with durability. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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15 pages, 3585 KiB  
Article
Characteristics and Performance of PTU-Cu Composite Membrane Fabricated through Simultaneous Complexation and Non-Solvent Induced Phase Separation
by Marianito Tiangson Margarito, Arnel Bas Beltran and Aileen Huelgas-Orbecido
Polymers 2021, 13(11), 1743; https://doi.org/10.3390/polym13111743 - 26 May 2021
Cited by 1 | Viewed by 2016
Abstract
This study aims to integrate copper (Cu) during membrane formation by a facile simultaneous phase separation process to alleviate biofouling and improve membrane performance. Polythiourea (PTU) polymer synthesized through condensation polymerization of 4,4-oxydianiline and p-phenylene diisothiocyanate in dimethyl sulfoxide was used in the [...] Read more.
This study aims to integrate copper (Cu) during membrane formation by a facile simultaneous phase separation process to alleviate biofouling and improve membrane performance. Polythiourea (PTU) polymer synthesized through condensation polymerization of 4,4-oxydianiline and p-phenylene diisothiocyanate in dimethyl sulfoxide was used in the preparation of dope solution. By incorporating different concentrations of cupric acetate in the non-solvent bath, both non-solvent induced phase separation and complexation induced phase separation occur instantaneously. Scanning electron microscopy—energy dispersive X-ray, fourier-transform infrared spectroscopy and time-of-flight secondary ion mass spectroscopy analysis accompanied by color change of the membrane surfaces—confirms the interaction of the polymer with Cu. Interaction of Cu at the interface during membrane formation results in a decrease in contact angle from 2 to 10° and a decrease in surface roughness from 30% to 52% as measured by atomic force microscope analysis. Pure water flux of PTU-Cu membrane increased by a factor of 3 to 17 relative to pristine PTU membrane. Both the pristine PTU and PTU-Cu membrane showed antibacterial characteristics against E. coli. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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15 pages, 3785 KiB  
Article
Ammonium Release and Adsorption Characters of Polyurethane–Biochar Crosslinked Material as an Additive Filler in Stormwater Treatment
by Yuan Wang, Yike Meng, Chuanyue Wang and Bao Wang
Polymers 2021, 13(10), 1557; https://doi.org/10.3390/polym13101557 - 13 May 2021
Cited by 2 | Viewed by 2217
Abstract
The additive fillers in bioretention facilities play a leading role in stormwater treatment to purify polluted runoff. At present, many traditional materials could not meet the requirements at the same time, including low ammonium leaching quantities, high water storage volume and strong ammonium [...] Read more.
The additive fillers in bioretention facilities play a leading role in stormwater treatment to purify polluted runoff. At present, many traditional materials could not meet the requirements at the same time, including low ammonium leaching quantities, high water storage volume and strong ammonium adsorption. This study investigated a polymer material, polyurethane–biochar crosslinked material (PCB), to evaluate the feasibility of using it as an additive filler in stormwater treatment compared with its raw material hardwood biochar (HB), and two traditional fillers. Successive leaching and ammonium isothermal adsorption experiments were conducted in deionized water and artificial stormwater. PCB leached 4.98–5.31 μmol/g NH4-N, less than the leaching quantities of compost, the traditional filler. After polyurethane modification, ammonium adsorption of PCB was improved: at a typical ammonium concentration of 2 mg/L in stormwater, PCB could adsorb 43.6 mg/kg ammonium versus 34.6 mg/kg for HB. With the addition of PCB in sand column, the ammonium adsorption improved from 31.34 to 84.72%. To improve the performance of bioretention facilities, PCB is recommended to be added into filter layers in stormwater treatment, taking advantage of its high cation exchange capacity and spongy internal structure to minimize overland flooding and enhance removal of ammonium from stormwater. Full article
(This article belongs to the Special Issue Cross-linked Polymers)
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