Incorporation Of Monomers Research Articles

Photocured Poly(Mannitol Sebacate) with Functional Methacrylic Monomer: Analysis of Physical, Chemical, and Biological Properties.

In this work, we described the formation of polymeric networks with potential antimicrobial character based on an acrylate oligomer, poly(mannitol sebacate) (PMS), and an enzymatically synthesized methacrylic monomer with thiazole groups (MTA). Networks with different content of MTA were prepared, and further physico-chemically characterized by microhardness, water contact angle measurements, and differential scanning calorimetry. Monomer incorporation into the networks and subsequent quaternization to provide thiazolium moieties affected the mechanical behavior and the surface wettability of the networks. Moreover, the introduction of permanent cationic charges in the network surface could give antimicrobial activity to them. Therefore, the antibacterial behavior and the hemotoxicity were analyzed against Gram-positive and Gram-negative bacteria and red blood cells, respectively.

Molecularly Imprinted Polymer-Based Luminescent Chemosensors

Molecularly imprinted polymer (MIP)-based luminescent chemosensors combine the advantages of the highly specific molecular recognition of the imprinting sites and the high sensitivity with the luminescence detection. These advantages have drawn great attention during the past two decades. Luminescent molecularly imprinted polymers (luminescent MIPs) towards different targeted analytes are constructed with different strategies, such as the incorporation of luminescent functional monomers, physical entrapment, covalent attachment of luminescent signaling elements on the MIPs, and surface-imprinting polymerization on the luminescent nanomaterials. In this review, we will discuss the design strategies and sensing approaches of luminescent MIP-based chemosensors, as well as their selected applications in biosensing, bioimaging, food safety, and clinical diagnosis. The limitations and prospects for the future development of MIP-based luminescent chemosensors will also be discussed.

Design and assembly of biodegradable capsules based on alginate hydrogel composite for the encapsulation of blue dye

The encapsulation of bluing agents in biodegradable polymeric capsules is an emerging option in laundry detergents sector to substitute formaldehyde-based polymers, because they are non-biodegradable, carcinogenic and toxic. In this work, we present for the first time the successful encapsulation of a blue dye in biodegradable capsules which shell was formed by an alginate hydrogel and a polyethylene glycol network. Different types of capsules were synthesized (addition or not of the diacrylate monomer) and irradiation of the crosslinking solution at different times. Furthermore, a deep characterization of each type of capsules was performed (chemical and morphological characterization, assessment of their mechanical and thermal properties, evaluation of their biodegradability), noting that the incorporation of the diacrylate monomer (PEGDMA) and the two different irradiation times selected substantially affected the final properties of the capsules. The obtained results will serve to comprehend how the dye can be released from the capsules.

Direct observation of single-molecular hIAPP fibril elongation reveal molecular mechanisms of morphological dependence and asymmetric growth.

Rapid growth of amyloid fibrils via seeded conformational conversion of monomers, is a critical step of fibrillization and important for the prion-like transmission of amyloid diseases. Amyloid fibrils are often polymorphic with relative populations morphology-dependent, but the molecular mechanisms of fibril elongation and corresponding morphological dependence remain poorly understood. Here, we applied replica exchange all-atom discrete molecular dynamics simulations to study the conformational conversion of hIAPP, an amyloid peptide associated with type-2 diabetes, catalyzed by two representative fibrils with distinct morphologies where hIAPP adopted S-shaped and extended conformations correspondingly. For both cases, the incorporation of monomers into the preformed fibrils with parallel in-register alignments was observed in our unbiased simulations. The fibril elongation free energy landscape derived from simulations is characterized by multiple basins corresponding to different intermediate states. Fibril morphology affected monomer binding at fibril elongation and lateral surfaces, and also the conformational conversion dynamics at the elongation surface, resulting into different elongation rates and thus relative populations for different fibril morphologies as observed experimentally. We also investigated the dynamics of hIAPP monomers bound to the fibril elongation surfaces at opposite ends. We observed distinct free energy landscapes in agreement with experimentally-observed asymmetric fibril growth, which can be attributed to subtle physicochemical difference of two ends in terms of contacting surfaces and patterns of available hydrogen bond donors and acceptors. Together, our results offered molecular insights to seeded conformational conformation of fibril elongation, morphological dependence, asymmetry fibril growth, and could shed light on amyloid strains with distinct disease progression.

Vilsmeier Complex Promotes Polycondensation of Imidodisulfuryl Chloride with Diols: Preparation of Ionic Oligomer Electrolytes

We report polycondensation of imidodisulfuryl chloride with diol monomers in the presence of catalysts. The method proceeds via stabilization of imidodisulfuryl chloride by the formation of a complex with N,N-dimethylformamide. This compound is well known as a Vilsmeier complex. The method is versatile and permits the incorporation of alkyl monomers in the oligomer backbone, and a maximum of 17 repeating units is reported. Linear ionic oligomers with protons, lithium ions, and BF4– incorporated into the main chain are successfully produced to fabricate self-standing composite single-ion ionic membranes that exhibited good ionic conductivity and stability at high voltages. Pulsed-field gradient nuclear magnetic resonance (PFG NMR) has been utilized to investigate ion diffusion in membranes.

Direct Synthesis of Partially Chain-Straightened Propylene Oligomers and P-MA Co-Oligomers Using Axially Flexible Shielded Iminopyridyl Palladium Complexes.

In this study, a series of partially chain-straightened propylene oligomers and functional propylene−methyl acrylate (P-MA) co-oligomers were synthesized with 8-alkyl-iminopyridyl Pd(II) catalysts. The molecular weight and polar monomer incorporation ratio could be tuned by using Pd(II) catalysts with various 8-alkyl-naphthyl substituents (8-alkyl: H, Me, and n-Bu). In propylene oligomerization, all the 8-alkyl-iminopyridyl Pd(II) catalysts convert propylene to partially chain-straightened (119−136/1000 C) oligomers with low molecular weights (0.3−1.5 kg/mol). Among the catalysts, Pd1 with non-substituent (H) on the ligand showed the highest activity of 5.4 × 104 g/((mol of Pd) h), generating oligomers with the lowest molecular weight (Mn: 0.3 kg/mol). Moreover, polar-functionalized propylene-MA co-oligomers with very high incorporation ratios (22.8−36.5 mol %) could be obtained in the copolymerization using these 8-alkyl-iminopyridyl Pd(II) catalysts. Additionally, Pd1 exhibited the best performance in propylene-MA copolymerization as it displayed the highest MA incorporation ratio of up to 36.5 mol%. All the three catalysts are capable of generating partially chain-straightened P-MA co-oligomers and the activities decrease gradually while the molecular weight increases with the increasing steric hindrance of the alkyl substituent (H < Me < n-Bu). Compared to Pd4 with the rigid 8-aryl substituent, the flexible 8-alkyl-iminopyridyl Pd(II) catalysts (Pd1-3) not only showed much higher activities in the propylene oligomerization, but also yielded P-MA co-oligomers with significantly higher incorporation ratios in the propylene co-oligomerization.

Incorporation of pseudoproline monomer (Fmoc-Thr[ψMe,Mepro]–OH) facilitates efficient solid-phase synthesis of difficult peptides

Solid-Phase Peptide Synthesis (SPPS) is a convenient and efficient method by which to prepare peptides. However, the sequences of compounds classified as “difficult” show aggregation of growing peptide chains and their synthesis is extremely challenging by stepwise SPPS. In this context, the concourse of pseudoproline derivatives helps to break the aggregation and facilitates the synthesis. Although pseudoproline moieties are traditionally incorporated as dipeptides, the possibility of using only the monomer adds flexibility to the synthesis. Herein, the introduction of the most hindered β-branched Thr[ψMe,Mepro] derivative is studied in terms of how difficult is its acylation is by the following amino acid and the impact of its use on the final purity of two well-known ”difficult peptides”.

Characterization of effects of chitooligosaccharide monomer addition on immunomodulatory activity in macrophages

The present study aimed to investigate the effects of five chitooligosaccharide monomers of different molecular weights on immunomodulatory activity in macrophage-like RAW264.7 cells. The incubation of various chitooligosaccharide monomers enhanced phagocytosis and pinocytosis activity toward Staphylococcus aureus and Escherichia coli in RAW264.7 cells. The incorporation of chitooligosaccharide monomers significantly boosted the generation of reactive oxygen species and reactive nitrogen species, as well as the release of inflammatory cytokines. To further explore the mechanism of inflammation regulated by chitooligosaccharide, the activation inhibitors of NF-кB (CAPE) and TLR-4 (TAK-242) were utilized, the determination data demonstrated that chitobiose suppressed the expression of inflammatory cytokines and NF-кB p65. In addition, the investigation results revealed that the presence of the mannose receptor inhibitor (mannan) suppressed chitohexaose-induced phagocytic activity and inflammatory cytokines. These results suggested that the five distinct chitooligosaccharide monomers had inconsistent effects, the chitobiose and chitohexaose exhibiting the best biological activity in activating RAW264.7 cells, promoting cell proliferation, and increasing non-specific immunity.

Prominent Spatial Structure and Synergistic Linkage Effects in Bimetallic Titanium Olefin Polymerization Catalysts

In this contribution, the binuclear Ti olefin polymerization catalyst 1,4-phenoxy{[Me2Si(C5H4)2]TiCl}2 (Complex 2) was synthesized by the reaction of hydroquinone with [Me2Si(C5H4)2]TiCl2. Compared to mononuclear [Me2Si(C5H4)2]TiCl2 (Complex 1), due to the synergistic effect of bimetals, Complex 2 was thermally more stable and showed higher activity up to 1.36 × 106 g/(molTi h) for ethylene polymerization at 120 °C. Remarkably, adding the phenoxy group in front of the metal center gives the catalyst a denser coordination environment, and the β-H elimination reaction is slowed down, thereby increasing the molecular weight of the polymer. DFT calculations showed that the Ti–Cp distances in active species 2 were extended by 0.059 and 0.063 Å, respectively, compared to those in active species 1. This makes the space of the active center more spacious and easier to promote olefin polymerization. Consequently, the copolymer’s 1-octene monomer incorporation rate reaches 16.21 mol %, with a fracture strain of 1140% and a stress recovery (SR) of 65%.

Modulation of Conformational Transition of Polypeptides under Slightly Acidic Environment†

Comprehensive SummaryControlling the conformational transition of polypeptides under slightly acidic environment is challenging. Herein, we report a class of pH‐responsive helix‐to‐coil conformationally transitionable polypeptides (pCTPs) by simply conjugating tertiary amine groups (TAs) to polylysine. Their conformation is highly dependent on the charge state of TAs, showing a helical structure when most TAs are deprotonated and a non‐helical structure when majority of TAs are protonated. The conformational transition pH can be modulated by tuning the hydrophobicity of TAs and the incorporation of hydrophobic monomers at a pH range of 7.2 to 6.0. Such pCTP showed a vesicle‐to‐micelle transition when their conformation transformed from helix to coil, facilitating controlled drug release. Our study provided an approach to control the conformational transition of polypeptides under slightly acidic condition.

A benzenesulfonic acid-modified organic polymer monolithic column with reversed-phase/hydrophilic bifunctional selectivity for capillary electrochromatography

Here, a styrene-based polymer monolithic column poly(VBS-co-TAT-co-AHM) with reversed-phase/hydrophilic interaction liquid chromatography (RPLC/HILIC) bifunctional separation mode was successfully prepared for capillary electrochromatography by the in situ polymerization of sodium p-styrene sulfonate (VBS) with cross-linkers 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) and 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT). The preparation conditions of the monolith were optimized. The morphology and formation of the poly(VBS-co-TAT-co-AHM) monolith were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The separation performances of the monolith were evaluated systematically. It should be noted that the incorporation of VBS functional monomer can provide π−π interactions, hydrophilic interactions, and ion-exchange interactions. Hence, the prepared poly(VBS-co-TAT-co-AHM) monolith can achieve efficient separation of thiourea compounds, benzene series, phenol compounds, aniline compounds and sulfonamides in RPLC or HILIC separation mode. The largest theoretical plate number for N,N′-dimethylthiourea reached 1.7 × 105 plates/m. In addition, the poly(VBS-co-TAT-co-AHM) monolithic column showed excellent reproducibility and stability. This novel monolithic column has great application value and potential in capillary electrochromatography (CEC).

(Invited) Structure-Property Relationships in Highly Permeable Dioxolane-Based Perfluorinated Ionomers

Ion conducting polymers used as membranes and catalyst binders in membrane electrode assemblies (MEAs) have driven continuous improvements in fuel cell performance. Commercially available membrane materials (e.g., Nafion®) impart low gas permeability, high chemical and mechanical stability thanks to their semi-crystalline polytetrafluoroethylene (PTFE) matrix. This dense matrix also slows permeation of gases through the polymer, introducing significant mass-transport losses in the catalyst layers and limits fuel cell performance. In this presentation, I will discuss a new family of perfluorinated ionomers that incorporates an amorphous matrix based on a perfluoro(2-methylene 4-methyl-1,3-dioxolane) (PFMMD) backbone. The introduction of a PFMMD backbone disrupts the crystallinity of the matrix, increases the matrix free volume, and significantly improves its gas permeability.1 The dioxolane backbone also increases the glass transition temperature of the matrix, impacting its mobility, limiting the ionomer domain swelling and reducing its proton conductivity. I will describe a flexible synthesis method for PFMMD-based ionomers which allowed us to study ionomers with tunable sulfonic acid content and derive structure-property relationships through a combination of transport measurements (i.e., water uptake, proton conductivity, and permeability) and morphological characterization through Small- and Wide-angle X-ray scattering. We will show how the incorporation of dioxolane monomers with bulky, asymmetric side-chains results in a stiff ionomer matrix with distinct chemical and mechanical properties. By varying the dioxolane matrix mass fraction, we gained fundamental insights into the role of the matrix chemical structure on the dynamics of structural and transport processes in ion-conducting polymers.2 Through in situ water uptake measurements, we elucidated the impact of the mass fraction and matrix chemical structure on water sorption rates. The mass-transport swelling rate of Nafion was around 50% higher than in dioxolane-containing ionomers and was independent of the matrix mass fraction. Non-Fickian polymer relaxation rate was sensitive to both type and fraction of the matrix, increasing by 22% across the range of dioxolane fractions studied and by another 100% in Nafion. These effects are attributed to reduction of segmental mobility of the hydrophobic matrix upon incorporation of dioxolane groups. The polymer relaxation is shown to correlate to changes in ionomer conductivity and nanostructure, reveled through in situ Grazing-Incidence Small Angle X-ray Scattering (GISAXS) measurements, showing two distinct physical processes that enable (i) rapid water sorption and ionomer domain swelling and (ii) polymer relaxation and ordering of ionomer domain structure. Lastly, I will discuss the implication and potential utilization of these new materials for improved fuel cell performance. The results presented here underscore the significance of tailoring materials chemistry to specific requirements of fuel cell or electrolysis MEAs.

Synthesis and Characterization of Quadrupolar-Hydrogen-Bonded Polymeric Ionic Liquids for Potential Self-Healing Electrolytes.

Within the era of battery technology, the urgent demand for improved and safer electrolytes is immanent. In this work, novel electrolytes, based on pyrrolidinium-bistrifluoromethanesulfonyl-imide polymeric ionic liquids (POILs), equipped with quadrupolar hydrogen-bonding moieties of ureido-pyrimidinone (UPy) to mediate self-healing properties were synthesized. Reversible addition–fragmentation chain-transfer (RAFT) polymerization was employed using S,S-dibenzyl trithiocarbonate as the chain transfer agent to produce precise POILs with a defined amount of UPy and POIL-moieties. Kinetic studies revealed an excellent control over molecular weight and polydispersity in all polymerizations, with a preferable incorporation of UPy monomers in the copolymerizations together with the ionic monomers. Thermogravimetric analysis proved an excellent thermal stability of the polymeric ionic liquids up to 360 °C. By combining the results from differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS), and rheology, a decoupled conductivity of the POILs from glass transition was revealed. While the molecular weight was found to exert the main influence on ionic conductivity, the ultimate strength and the self-healing efficiency (of up to 88%) were also affected, as quantified by tensile tests for both pristine and self-healed samples, evidencing a rational design of self-healing electrolytes bearing both hydrogen bonding moieties and low-molecular-weight polymeric ionic liquids.

Thermal stabilization of the smectic-Cα* phase by doping with photo-active reactive mesogen

• The incorporation of monomers into liquid crystals changes their physical properties. • Dielectric properties and switching behaviour of liquid crystal molecules depend on the monomer concentration. • A new method for thermal stabilization of the smectic-Ca* phase is presented. • The admixture of monomer causes a relatively small decrease in spontaneous polarization of the liquid crystal system. The effect of a photo-active reactive mesogen 4-(3-acryloyloxypropyloxy)-benzoesure2-methyl-1,4-phenylester on an antiferroelectric liquid crystal was investigated in the context of possible broadening of the temperature range in which the smectic-C α * phase exists in newly synthesized hybrid materials promising for optical applications. In the mixtures of various reactive mesogen concentrations from 1 to 9 wt. %, dielectric spectroscopy and reversal current method were used to determine the temperature range and switching time of the smectic-C α * phase. As a result of reactive mesogen doping, the thermal stabilization of the smectic-C α * phase over 21.5 °C, around a room temperature, i.e. between 26.5 and 48 °C, was confirmed in the modified liquid crystal system.

Challenges to incorporate high contents of bio-based isobornyl methacrylate (IBOMA) into waterborne coatings

Emulsion polymerization of (meth)acrylic bio-based monomers is a promising method to obtain waterborne coatings with reduced carbon footprint. However, the high hydrophobicity of some bio-based monomers can hinder the straightforward incorporation of such monomers in waterborne dispersions. In this work, we explore the copolymerization of bio-based isobornyl methacrylate (IBOMA) with 2-octyl acrylate (2-OA) to produce latexes with >70 % bio-content suitable for coating applications. First, the homopolymerization of IBOMA is studied to gather more information on the emulsion polymerization of the monomer producing high Tg polymer with different surfactants. It is found that the batch emulsion homopolymerization of IBOMA is challenging due to coagulation during the polymerization, likely as a result of mass transport limitations due to the high hydrophobicity of IBOMA. Interestingly, stable dispersions are achieved when 5 % of the IBOMA is substituted by methyl methacrylate. The stability of the IBOMA/2-OA copolymer system is found to be dependent on both the IBOMA concentration in the copolymer and the solids content of the latex. Thus, we provide a stability map for IBOMA/2-OA copolymers with different compositions and solids contents showing the areas where stable and not-stable dispersions are obtained.

Effects of Filler Functionalization on Filler-Embedded Natural Rubber/Ethylene-Propylene-Diene Monomer Composites.

Natural rubber (NR) presents a number of advantages over other types of rubber but has poor resistance to chemicals and aging. The incorporation of ethylene propylene diene monomer (EPDM) into the NR matrix may be able to address this issue. Mineral fillers, such as carbon black (CB) and silica are routinely incorporated into various elastomers owing to their low cost, enhanced processability, good functionality, and high resistance to chemicals and aging. Other fillers have been examined as potential alternatives to CB and silica. In this study, phlogopite was surface-modified using 10 phr of compatibilizers, such as aminopropyltriethoxysilane (A1S), aminoethylaminopropyltrimethoxysilane (A2S), or 3-glycidoxypropyltrimethoxysilane (ES), and mixed with NR/EPDM blends. The effects of untreated and surface-treated phlogopite on the mechanical properties of the rubber blend were then compared with those of common fillers (CB and silica) for rubbers. The incorporation of surface-modified phlogopite into NR/EPDM considerably enhanced various properties. The functionalization of the phlogopite surface using silane-based matters (amino- and epoxide-functionalized) led to excellent compatibility between the rubber matrix and phlogopite, thereby improving diverse properties of the elastomeric composites, with effects analogous to those of CB. The tensile strength and elongation at break of the phlogopite-embedded NR/EPDM composite were lower than those of the CB-incorporated NR/EPDM composite by 30% and 10%, respectively. Among the prepared samples, the ES-functionalized phlogopite showed the best compatibility with the rubber matrix, exhibiting a tensile strength and modulus of composites that were 35% and 18% higher, respectively, compared with those of the untreated phlogopite-incorporated NR/EPDM composite. The ES-functionalized phlogopite/NR/EPDM showed similar strength and higher modulus (by 18%) to the CB/NR/EPDM rubber composite, despite slightly lower elongation at break and toughness. The results of rebound resilience and compression set tests indicated that the elasticity of the surface-modified phlogopite/NR/EPDM rubber composite was higher than that of the silica- and CB-reinforced composites. These improvements could be attributed to enhancements in the physical and chemical interactions among the rubber matrix, stearic acid, and functionalized (compatibilized) phlogopite. Therefore, the functionalized phlogopite can be utilized in a wide range of applications for rubber compounding.

Harmonizing Topological Features of Self-Assembled Fibers by Rosette-Mediated Random Supramolecular Copolymerization and Self-Sorting of Monomers by Photo-Cross-Linking.

Random copolymerization is an effective approach to synthesize the desired polymers by harmonizing distinct properties of different monomers. For supramolecular polymers in which monomer binding is inherently dynamic, it is difficult to achieve random copolymerization of monomers with distinct molecular structures and properties due to an enthalpic advantage upon self-recognition (self-sorting). Herein, we demonstrate an example of thermodynamically controlled random supramolecular copolymerization of two monomers functionalized with barbituric acid via the formation of six-membered hydrogen-bonded rosette intermediates to exhibit structural harmonization of the two main-chain motifs, i.e., intrinsically curved and linear motifs. One monomer based on naphthalene chromophore exclusively forms toroidal fibers, whereas another one bearing additional photoreactive diacetylene moiety affords linearly elongated fibers. Supramolecular copolymerization of the two monomers is achieved by cooling hot monomer mixtures in a nonpolar solvent, which results in the formation of thermodynamically stable spirally folded yet elongated fibers. Atomic force microscopic observations and theoretical simulations of the experimental data obtained by absorption spectroscopy reveal the homopolymerization of the diacetylene-functionalized monomer in the high-temperature region, followed by the incorporation of the naphthalene monomer in the medium-temperature region to form supramolecular copolymers with random monomer sequence. Finally, we demonstrate that the random copolymerization process can be switched to a narcissistically self-sorting one by deactivating monomer exchange through the photo-cross-linking of the diacetylene-functionalized monomers.

From Organic Wastes and Hydrocarbons Pollutants to Polyhydroxyalkanoates: Bioconversion by Terrestrial and Marine Bacteria

The use of fossil-based plastics has become unsustainable because of the polluting production processes, difficulties for waste management sectors, and high environmental impact. Polyhydroxyalkanoates (PHA) are bio-based biodegradable polymers derived from renewable resources and synthesized by bacteria as intracellular energy and carbon storage materials under nutrients or oxygen limitation and through the optimization of cultivation conditions with both pure and mixed culture systems. The PHA properties are affected by the same principles of oil-derived polyolefins, with a broad range of compositions, due to the incorporation of different monomers into the polymer matrix. As a consequence, the properties of such materials are represented by a broad range depending on tunable PHA composition. Producing waste-derived PHA is technically feasible with mixed microbial cultures (MMC), since no sterilization is required; this technology may represent a solution for waste treatment and valorization, and it has recently been developed at the pilot scale level with different process configurations where aerobic microorganisms are usually subjected to a dynamic feeding regime for their selection and to a high organic load for the intracellular accumulation of PHA. In this review, we report on studies on terrestrial and marine bacteria PHA-producers. The available knowledge on PHA production from the use of different kinds of organic wastes, and otherwise, petroleum-polluted natural matrices coupling bioremediation treatment has been explored. The advancements in these areas have been significant; they generally concern the terrestrial environment, where pilot and industrial processes are already established. Recently, marine bacteria have also offered interesting perspectives due to their advantageous effects on production practices, which they can relieve several constraints. Studies on the use of hydrocarbons as carbon sources offer evidence for the feasibility of the bioconversion of fossil-derived plastics into bioplastics.

Highly stretchable and tough thermo-responsive double network (DN) hydrogels: Composed of PVA-borax and poly (AM-co-NIPAM) polymer networks

The development of polymeric double network (DN) hydrogels consisting of polyvinyl alcohol-borax (PVA-Borax), poly(N-isopropylacrylamide) and poly(acrylamide) are encouraging to utilize them in many applications like as soft materials for biomedical and other applications due to their unique characteristics such as stretchability, toughness, thermo-responsiveness, resilient and self-healing property. The DN hydrogels are hydrophilic in nature and also soft smart materials that have higher capability to absorb water and also, they respond external stimuli such as temperature, pressure and chemical trigging. Thus, DN hydrogels of PVA-Borax as the first network and poly (NIPAM-co-AM) as the second network are prepared and characterized. Synthesized DN hydrogels are sensitive to temperature by introducing the temperature sensitive polymer, poly (NIPAM) into the network. Poly (AM) is used for high swelling and the stiffness improvement. The degree of swelling increases with the increasing amount of AM in the network. The highest degree of swelling is achieved as high as 1272% in GNAM-1 which contains 100% AM in second network (No NIPAM). The lower critical solution temperature (LCST) was observed to be 31.5 °C for GNAM-5 (100 wt% NIPAM and no AM) DN hydrogel by swelling study. In DSC analysis volume phase transition has been observed to be 33.72 °C for this hydrogel. However, marginal increment of phase transition is observed due to incorporation of more hydrophilic AM monomer in the second network. The synthesized DN hydrogels exhibit excellent mechanical properties. We tested all the samples with different water content (WC). Such a DN hydrogel (GNAM-3) sustains high compressive stress 5.75 MPa at 87.71 % strain with 30% WC, whereas it was decreased to 1.33 MPa at 75.02% strain with 60% WC and to 0.0.86 MPa at 75.86% with 90% WC. The maximum compressive fracture energy is observed for this sample with 30% WC which is 36.72 MJ/m3. This DN hydrogel also maintained its shape after many mechanical cycles, indicating the achievement of desirable resilience properties. Furthermore, it could be stretched up to 944 % strain with the tensile strength of 0.473 MPa with 60% WC. Fracture strain of the hydrogels was increased with poly(NIPAM) amount in the DN hydrogels till the 1:1 of Poly(NIPAM): poly(AM) after that it was started to decrease. The highest fracture strength of 1.36 MPa is observed for GNAM-5 hydrogels with 30% WC.

Polyimide-supported Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl catalytic systems: Aromatic donor-acceptor interaction-directed cooperative catalysis

Non-covalent immobilization of multifunctional catalysts onto polymer supports is a promising technique to build highly efficient heterogeneous cooperative catalysts. Here, we present a strategy to build polyimide-supported Cu/2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) catalytic systems based on hydrophobic interactions and aromatic donor-acceptor interactions. Pyrene-containing catalytic species and naphthalene diimide (NDI)-based polyimides were chosen for the preparation of nanoparticle catalysts using the nanoprecipitation technique. The cooperative behaviors of catalytic components were evaluated by the catalytic activities of aerobic oxidation of benzyl alcohol (BnOH) in water. We studied the influence of effective constituent ratio of polymers, chain length of monomer, and the incorporation of a second monomer on catalytic activities. The aggregate structures were investigated by X-ray powder diffraction (XRD) patterns and small angle X-ray scattering (SAXS), and speculated to be random distributions of aromatic stacking clusters within nanoparticle catalysts. This strategy will find applications in the construction of other multifunctional heterogeneous catalysts.