Cross-linked Copolymer Research Articles

Salt endurable and shear resistant polymer systems based on dynamically reversible acyl hydrazone bond

The macromolecule systems constructed via dynamic covalent bonds may exhibit high viscosity and elasticity. The ketone-based copolymers were prepared via free radical copolymerization of acrylamide (AM) with diacetone acrylamide (DAAM). And the cross-linked copolymer based on dynamic acyl hydrazone bond was formed by ketone-based copolymer and adipic dihydrazide (ADH). The optimum conditions for the construction of the cross-linked copolymer and its salt endurance, shear resistance and temperature tolerance were investigated by viscosity analysis, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Moreover, the viscoelasticity behavior of copolymers in aqueous solution was explored by rheology measurements. The results showed that the system had excellent viscosity with a 1 M ratio of hydrazide at 3000 mg/L. Furthermore, the cross-linked copolymer still maintained a large hydrodynamic radius and considerable viscosity at high salinity, even after high-speed shear. The combination of high molecular weight copolymer and dynamic covalent bond makes the copolymer exhibit excellent salt and shear resistance, which provides an alternative thought of enhancing oil recovery.

Efficient synthesis of dimethyl carbonate via transesterification of ethylene carbonate catalyzed by swelling poly(ionic liquid)s

The synthesis of dimethyl carbonate (DMC) via transesterification of ethylene carbonate (EC) and methanol (MeOH) was an environmental and practical strategy. Herein, poly(ionic liquid)s (PILs) with swelling abilities were synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids, sodium 4-vinylbenzoate and cross-linker 1,8-triethylene glycoldiyl-3,3ʹ-divinylimidazolium bromide ([(EG)3-DVIm]Br2). The swelling abilities of PILs in various solvents were measured, and PILs could swell in methanol (MeOH). The swelling ability of PILs in MeOH could be modulated by changing the cross-linker content and chain length of 3-alkyl-substituents on imidazolium. The swollen state of PILs in MeOH presented a porous cross-linked network structure observed by the cryo-scanning electron microscope (cryo-SEM). The swelling PILs were used to catalyze the transesterification of ethylene carbonate (EC) and MeOH to prepare the DMC, and the catalytic activities was correlated with the swelling abilities of PILs. The PIL with 3-butyl-substituent and 2.5 mol% cross-linker (poly[VBIm-VBA-DVIm]-2.5%) had the highest swelling ratio (Q = 12.4 (g/g)) in MeOH and EC mixed solvents and exhibited excellent catalytic activities, which was similar to corresponding homogeneous ionic liquid. Furthermore, the catalyst could be reused up to seven runs without any considerable loss of its initial activity.

Characterization of Desulfurized Crumb Rubber/Styrene-Butadiene-Styrene Composite Modified Asphalt Based on Rheological Properties.

With the growing interest in bituminous construction materials, desulfurized crumb rubber (CR)/styrene–butadiene–styrene (SBS) modified asphalts have been investigated by many researchers as low-cost environmental-friendly road construction materials. This study aimed to investigate the rheological properties of desulfurized CR/SBS composite modified asphalt within various temperature ranges. Bending beam rheometer (BBR), linear amplitude sweep (LAS), and multiple stress creep recovery (MSCR) tests were performed on conventional CR/SBS composite modified asphalt and five types of desulfurized CR/SBS modified asphalts. Meanwhile, Burgers’ model and the Kelvin–Voigt model were used to derive nonlinear viscoelastic parameters and analyze the viscoelastic mechanical behavior of the asphalts. The experimental results indicate that both the desulfurized CR/SBS composite modifier and force chemical reactor technique can enhance the crosslinking of CR and SBS copolymer, resulting in an improved high-, intermediate-, and low-temperature performance of desulfurized CR/SBS composite modified asphalt. Burgers’ model was found to be apposite in simulating the creep stages obtained from MSCR tests for CR/SBS composite modified asphalts. The superior high-temperature performance of desulfurized CR/SBS modified asphalt prepared with 4% SBS, 20% desulfurized rubber, and a force chemical reactor time of 45 min contributes to the good high-temperature elastic properties of the asphalt. Therefore, this combination is recommended as an optimal preparation process. In summary, the desulfurization of crumb rubber and using the force chemical reactor technique are beneficial to composite asphalt performance and can provide a new way of utilizing waste tire rubber.

Quasi-monodispersed nanocapsules with form stability at high temperature and under shear force for thermal energy storage

Nanoencapsulated phase change materials (NPCMs) have attracted much attentions during the past decades due to their large potential application in the sectors of solar energy harvesting, waste heat recovery, and smart buildings and fibers. However, it is still a big challenge to obtain form-stable NPCMs without leakage at high temperature (e.g. 180 ℃) and under external shear force. Form-stability investigations of almost of the reported NPCMs focus on the temperature range up to 100 ℃, which cannot satisfy the thermal processing requirements (140–200 ℃ under shear force) of commonly available thermoplastics like poly(vinyl chloride) and poly(lactic acid). We herein for the first time demonstrate a facile method to prepare a series of novel room temperature NPCMs with the latent heat up to 116.1 J g−1 and fabulous form-stability even if the surrounding temperature approximates 180 ℃ under an external shear force of 101.9 kN m−2. To this aim, quasi-monodispersed NPCMs with the average size less than 120 nm were prepared, wherein dodecanol and in-situ cross-linked acrylate copolymers were used as the heat storage core and the supramolecular lock shell layer of the NPCMs, respectively. Storage reliability, morphology, phase change behaviors, and form-stability at different conditions of the resulting NPCMs were extensively evaluated. The fabricated NPCMs exhibit outstanding monodispersity and form-stability at high temperature and under shear force, and probably opens a new avenue to develop functional thermoplastic and/or thermosetting composites for the next generation of smart building, furniture, and decoration materials with a promising heat energy storage and release ability.

Optical and structural proprieties of the new triblock copolymer (A-B-C) based on p-terphenyl, PVK and MEH-PPV for organic electronics: Experimental and theoretical study

A new cross-linked triblock copolymer has been elaborated. The optical properties have demonstrated that the resulting material presents original properties compared to the pristine homopolymers. In fact, the optical absorption of the A-B-C copolymer overlapped all the ultraviolet (UV) and visible domain. Furthermore, combined with experimental analyses, DFT and TD-DFT calculations have been used to predict the most probable appropriate model structure of the triblock copolymer. So, the electronic properties of the selected model structure have been computed. All the obtained results support that this new copolymer is usable as an active layer in the optoelectronic fields due to its original properties.

Diazo-Based Copolymers for the Wet Strength Improvement of Paper Based on Thermally Induced CH-Insertion Cross-Linking.

We present an alternative to commonly used, but from an environmental point of view, problematic wet strength agents, which are usually added to paper to prevent a loss of mechanical stability and finally disintegrate when they get into contact with water. To this end, diazoester-containing copolymers are generated, which are coated onto paper and by heating to 110-160 °C for short periods of time become activated and form carbene intermediates, which undergo a CH-insertion cross-linking reaction. The process leads to a simultaneous cross-linking of the polymer and its attachment to the cellulose substrate. The immobilization process of copolymers consisting of a hydrophilic matrix based on N,N-dimethylacrylamide and a diazoester-based comonomer to a cellulose model surface and to laboratory-engineered, fibrous paper substrates is investigated as a function of time, temperature, and cross-linker composition. The distribution of the polymer in the fiber network is studied using confocal fluorescence microscopy. Finally, the tensile properties of modified wet and dry eucalyptus sulfate papers are measured to demonstrate the strong effect of the thermally cross-linked copolymers on the wet strength of paper substrates. Initial experiments show that the tensile indices of the modified and wetted paper samples are up to 50 times higher compared to the values measured for unmodified samples. When dry and wet papers coated with the above-described wetting agents are compared, relative wet strengths of over 30% are observed.

Synthesis and Applications of Polymeric Reagent p-Substituted Triphenylamine

Chemical modification of chloromethylstyrene - styrene copolymer throughout reaction of p-substituted carboxylic acid group of bis-(4,4`-dibromo)-4``-triphenylamine carboxylic acid with the chloromethyl group attached to a phenyl group was carried out on soluble copolymer and polymeric cross-linked copolymer. Chemical oxidation of the neutral p-substituted triphenylamine with antimony pentachloride in dichloromethane solvent gives the corresponding cation - radical salt with the counter ion antimony hexachloride (SbCl6-). The isolated deep blue color cation radical salt is soluble or in insoluble (resin) form in the copolymer was used as a thermal cationic initiator for the polymerization of epoxy and vinyl monomers at room temperature. The cation radical resin showed good activity and stability compared to the soluble polymeric cation radical, both can initiate the cationic polymerization of cyclohexene oxide and N-vinylcarbazole in dichloromethane at room temperature.

Hydration and Thermal Response Kinetics of a Cross-Linked Thermoresponsive Copolymer Film on a Hydrophobic PAN Substrate Coating Probed by In Situ Neutron Reflectivity.

The hydration and thermal response kinetics of the cross-linked thermoresponsive copolymer poly((diethylene glycol monomethyl ether methacrylate)-co-poly(ethylene glycol) methyl ether methacrylate), abbreviated as P(MEO2MA-co-OEGMA300), thin film on a hydrophobic polyacrylonitrile (PAN) substrate coating, which resembles a synthetic fabric, is probed by in situ neutron reflectivity (NR). The PAN and monomer (MEO2MA and OEGMA300) solutions are sequentially spin-coated onto a silicon (Si) substrate. Afterward, plasma treatment is applied to realize the cross-linking of PAN and monomers. The as-prepared cross-linked P(MEO2MA-co-OEGMA300) film on the hydrophobic PAN substrate coating presents a two-layer structure: a substrate-near layer, which is a mixture of PAN and P(MEO2MA-co-OEGMA300), and a main layer, which is composed of pure hydrophilic P(MEO2MA-co-OEGMA300). During hydration in D2O vapor atmosphere, the hydrophobic PAN component prevents the formation of D2O enrichment in the substrate-near layer. However, an additional vapor-near layer is observed on top of the main layer, which is enriched with D2O. The hydration process is constrained by the cross-linking points in the film, inducing the relaxation time to be longer than that in a spin-coated P(MEO2MA-co-OEGMA300) film. Because the as-prepared cross-linked film presents a transition temperature (TT) at 38 °C, the hydrated film switches to the collapsed state when the temperature is increased from 23 to 50 °C. The response to a thermal stimulus is also slower due to the existence of the internal cross-linking points as compared to the spin-coated film. Interestingly, no reswelling is observed at the end of the thermal stimulus, which can be also attributed to the presence of internal cross-linking points.

NITROGEN-CONTAINING CHELATE COMPLEXES AND MONOMERS BASED ON THEM

By the interaction between N-methylolthiourea and Co2+, Mn2+ acetates are obtained compounds that were later used for the synthesis of vinyl bifunctional groups containing polymerizable chelate complexes. These compounds are recommended to be used as crosslinkers for obtaining, on the basis of water-based soluble monomers, spatially cross-linked water-swellable copolymers with applied purpose. There are dynamics of water absorption of copolymers from the time of their stay in water.

Accessibility of fiber surface sites for polymeric additives determines dry and wet tensile strength of paper sheets

This contribution focuses on understanding of paper wet-strength properties, by taking a closer look at the spatial distribution of wet-strengthening polymers inside the cellulosic fiber network deposited under different treatment conditions using confocal laser scanning microscopy as in situ imaging tool. We compare the behavior of paper samples treated with a photochemically cross-linkable copolymer using an impregnation process employing three different solvents, namely water, 2-propanol (IPA) and 1-butanol (BuOH), respectively. As these solvents swell paper fibers to quite different extents, the deposition of the polymer, on, in or in-between the cellulosic fibers varies quite strongly, as is shown by in-depth analysis using confocal laser scanning microscopy. The difference in accessibility of distinct surface sites exclusively on or also in and between the fibers controls the macroscopic tensile strength under both dry and wet conditions.

Multiresponsive Cellulose Nanocrystal Cross-Linked Copolymer Hydrogels for the Controlled Release of Dyes and Drugs.

Multiresponsive hydrogels have attracted tremendous interest due to their promising applications in tissue engineering, wearable devices, and flexible electronics. In this work, we report a multiresponsive upper critical solution temperature (UCST) composite hydrogel based on poly (acrylic acid-co-acrylamide), PAAc-co-PAAm, sequentially cross-linked by acid-hydrolysis cellulose nanocrystals (CNCs). Scanning electron microscopy (SEM) observations demonstrated that the hydrogels are formed by densely cross-linked porous structures. The PAAc/PAAm/CNC hybrid hydrogels exhibit swelling and shrinking properties that can be induced by multiple stimuli, including temperature, pH, and salt concentration. The driving force of the volume transition is the formation and dissociation of hydrogen bonds in the hydrogels. A certain content of CNCs can greatly enhance the shrinkage capability and mechanical strength of the hybrid hydrogels, but an excess addition may impair the contractility of the hydrogel. Furthermore, the hydrogels can be used as a matrix to adsorb dyes, such as methylene blue (MB), for water purification. MB may be partly discharged from hydrogels by saline solutions, especially by those with high ionic strength. Notably, through temperature-controlled hydrogel swelling and shrinking, doxorubicin hydrochloride (DOX-HCl) can be controllably adsorbed and released from the prepared hydrogels.

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Hydrophilic Cross-Linked Aliphatic Hydrocarbon Diblock Copolymer as Proton Exchange Membrane for Fuel Cells.

This study proposes a hydrophobic and hydrophilic aliphatic diblock copolymer wherein the hydrophobic block contains glycidyl methacrylate (GMA) units that are distanced by poly(acrylonitrile) (PAN) segments to fabricate a proton exchange membrane (PEM). This diblock copolymer also known as ionomer due to the hydrophilic block comprising 3-sulfopropyl methacrylate potassium salt (SPM) block. The diblock copolymer was synthesized in the one-pot atom transfer radical polymerization (ATRP) synthesis. Subsequently, the membrane was fabricated by means of solution casting in which an organic diamine, e.g., ethylene diamine (EDA), was introduced to crosslink the diblock copolymer chains via the addition of amine to the epoxide group of GMA. As a result, the PEM attained possesses dual continuous phases, in which the hydrophobic domains are either agglomerated or bridged by the EDA-derived crosslinks, whereas the hydrophilic domains constitute the primary proton conducting channels. The in-situ crosslinking hydrophobic block by using a hydrophilic cross-linker represents the merit aspect since it leads to both improved proton conductivity and dimensional stability in alcohol fuel. To characterize the above properties, Nafion® 117 and random copolymer of P(AN-co-GMA-co-SPM) were used as control samples. The PEM with the optimized composition demonstrates slightly better fuel cell performance than Nafion 117. Lastly, this diblock ionomer is nonfluorinated and hence favors lowering down both material and environmental costs.

Cross-linked valerolactone copolymer implants with tailorable biodegradation, loading and in vitro release of paclitaxel

Implantable drug delivery systems, formed from degradable and non-degradable polymers, can offer several advantages over traditional dosage forms for sustained drug delivery. The majority of degradable implant systems developed to date are composed of poly(lactide-co-glycolide) (PLGA). However, PLGA-based systems are not suitable for the delivery of all drugs. Each drug is unique in terms of physico-chemical properties, and polymer-drug compatibility plays a significant role in determining a drug formulation's performance. In this study, two novel cross-linkable δ-valerolactone-based copolymers were synthesized and used to prepare cross-linked disc-shaped implants. The manipulation of the composition of the discs and conditions used during drug loading were found to influence various aspects of the delivery system performance including the degree of swelling, degradation, drug-loading and in vitro release. The polymeric discs resulted in no adverse effects following subcutaneous implantation in naïve rats. These studies support further development of cross-linkable valerolactone matrices as implantable formulations for sustained drug delivery.

High-modulus nanocomposite scaffold based on waterborne polyurethane grafted collagen polypeptide/hydroxyapatite for potential bone healing

A potential nanocomposite scaffold based on waterborne polyurethane grafted collagen polypeptide/hydroxyapatite (WPU-g-CP/HAp) was investigated in this research. First, a non-solvated WPU-g- CP copolymer emulsion was synthesized via water phase cross-linking copolymerization between waterborne polyurethane (WPU) prepolymer and KH550 modified collagen polypeptide (CP). Then, the WPU-g-CP/HAp was fabricated employing bionic precipitation method of HAp nanocrystals, followed by freeze-drying casting. TEM images of WPU-g-CP/HAp emulsion particles showed an assembly of polymer nano-microspheres with a HAp mineralized area. FT-IR and XRD results confirmed that the large quantities of HAP microcrystalline structures were formed in the WPU-g-CP/HAp nanocomposite. DMA analysis demonstrated that the WPU-g-CP/HAp had extremely high storage modulus (7000 MPa) and mechanical strength, which were very important for mechanical support as an ideal bone healing material. TG/DTG, SEM and EDS indicated that HAp has been uniformly dispersed into the nanocomposite in the form of crystallites, and showed good thermal stability and structural stability. Biodegradation test revealed that the degradation cycle of WPU-g-CP/HAp can meet the requirements of bone healing material. It could be expected that in the process of nanocomposite degradation the HAp will be continuously released into the extracellular environment to achieve bone healing via providing scaffolding for osteoconduction, proliferation, growth factors for osteoinduction, and new bone formation, which is extremely beneficial as a bone tissue healing scaffold.

Redox-responsive poly(ionic liquid) microgels explored as the building blocks for supramolecular assembly

In this study, poly(ionic liquid) (PIL) microgel functionalized by ferrocene (Fc) was fabricated via a facile one-step cross-linking copolymerization in selective solvent. The results demonstrated that the sizes of PIL microgels could be well-tuned through the feeding ratio of IL monomers to the cross-linker. The presence of Fc groups in PIL microgel was confirmed through ultraviolet–visible (UV–vis), inductively coupled plasma optical emission spectrometer (ICP-OES) and Fourier transform infrared (FT-IR) measurements, as well as cyclic voltammetry (CV) technique. In addition, Fc-anchored PIL microgels were found to be electrochemically active and could respond reversibly to the redox stimulus. As a prototype application, Fc-anchored PIL microgels were explored as the building blocks for the supramolecular self-assembly. Through the host-guest inclusion complexation interaction of Fc group with β-cyclodextrin (β-CD) dimer, PIL microgels could undergo a reversible association and dissociation. Importantly, an enhanced peak current could be achieved when PIL microgel-supported Fc groups were complexed with β-CD dimer. The founding thus pave a way toward fabricating supramolecular systems using nanoparticles as the building blocks, which will find wide applications in smart material, drug delivery and electrochemistry.

Preparation and electrochemical properties of a polyN,N’-methylene diacrylamide-based cross-linking copolymer film on 6063 Al alloy

ABSTRACT A N, N’-methylene diacrylamide-based cross-linking copolymer film was thermally polymerised on a 6063 Al alloy using ethylene glycol maleic rosinate acrylate (EGMRA) as the cross-linking agent. The chemical structure and morphology of the copolymer films were examined by Fourier transform-infrared spectroscopy and scanning electron microscopy, respectively. Results confirmed that the polyN, N’-methylene diacrylamide (PMBA)-based cross-linking copolymer films were prepared on the 6063 Al alloy. The corrosion resistance of the PMBA-based films in the absence and presence of the EGMRA was evaluated in 3.5 wt.% NaCl solution by polarisation curves and electrochemical impedance spectroscopy as well as immersion tests. The results showed that the PMBA–EGMRA cross-linked film effectively protected the Al alloy.

A Highly Expanded Polycarboxylate Gel and New Environmental Response Effects for Efficiently Adsorbing and Recovering Cu(II) from Water.

A new highly expanded polycarboxylate gel (EPCG) was accidentally formed in a facile cross-linking copolymerization system. When used as an adsorbent material, the EPCG could be quickly expanded 29.44 times in water to have a high permeability inside for realizing the efficient adsorption toward Cu(II) from water. The adsorption capacity of EPCG toward Cu(II) was 261.70 mg/g, which was higher than that of all the selected existing adsorbents reported in recent years. The adsorption rate of expanded EPCG was 3.61 times higher than that of the previous polyantionic gel. Similarly, due to the high expansion and high permeability of EPCG, the EPCG skeleton could be further coated with an alkaline NaOH, forming a novel NaOH-coated EPCG material, and its adsorption capacity toward Cu(II) was further improved to 333.21 mg/g compared to that of pure EPCG adsorbent. Moreover, the EPCG wastes after adsorbing Cu(II) could be fully desorbed to be regenerated for reuse. A total of 99.39% of the adsorbed Cu(II) was desorbed from EPCG wastes to be recovered. The adsorption capacity of regenerated EPCG reused for adsorbing Cu(II) was 259.05 mg/g, which was very near that of the original EPCG. In addition, a series of simulation experiments and instrumental analysis were adopted to confirm the new environmental response effects as the key factors in the purification of Cu(II)-containing wastewater, including “expansion-shrink,” “alkali-coating,” and “acid-desorption” responses.

Amphiphilic Poly(dimethylsiloxane-ethylene-propylene oxide)-polyisocyanurate Cross-Linked Block Copolymers in a Membrane Gas Separation.

Amphiphilic poly(dimethylsiloxane-ethylene-propylene oxide)-polyisocyanurate cross-linked block copolymers based on triblock copolymers of propylene and ethylene oxides with terminal potassium-alcoholate groups (PPEG), octamethylcyclotetrasiloxane (D4) and 2,4-toluene diisocyanate (TDI) were synthesized and investigated. In the first stage of the polymerization process, a multiblock copolymer (MBC) was previously synthesized by polyaddition of D4 to PPEG. The usage of the amphiphilic branched silica derivatives associated with oligomeric medium (ASiP) leads to the structuring of block copolymers via the transetherification reaction of the terminal silanol groups of MBC with ASiP. The molar ratio of PPEG, D4, and TDI, where the polymer chains are packed in the “core-shell” supramolecular structure with microphase separation of the polyoxyethylene, polyoxypropylene and polydimethylsiloxane segments as the shell, was established. Polyisocyanurates build the “core” of the described macromolecular structure. The obtained polymers were studied as membrane materials for the separation of gas mixtures CO2/CH4 and CO2/N2. It was found that obtained polymers are promising as highly selective and productive membrane materials for the separation of gas mixtures containing CO2, CH4 and N2.

Semi-Crystalline Copolymer Hydrogels as Smart Drug Carriers: In Vitro Thermo-Responsive Naproxen Release Study.

In this study, poly(N-isopropylacrylamide-co-2-hydroxypropyl methacrylate) hydrogels were synthesized using free radical initiated copolymerization method. Four hydrogels with different cross-linker concentrations were prepared. Semi-crystalline, cross-linked copolymer networks were confirmed by FTIR, SEM and XRD analysis. Variation of swelling behaviour was monitored gravimetrically and thermo-responsiveness has been noticed. An application of synthesized thermo-responsive hydrogels as carriers for the modulated release of anti-inflammatory model drug was investigated. Moreover, naproxen loading into these hydrogels was also determined using FTIR, SEM and XRD techniques and release was analyzed using HPLC method at simulated physiological conditions. Swelling kinetic and mechanism of water transport, as well as diffusion of naproxen through the hydrogels were analyzed. Thus, the aim of this work was to study various compositions of obtained hydrogels and their possibility of application as a thermo-responsive carrier for prolonged naproxen release in order to evaluate as a potential candidate for drug carrier in future pharmaceutical applications.