The present work demonstrates the synthesis of new bio-based benzoxazine monomers via Mannich-like condensation of naturally occurring raw materials, for example, phloretic acid (PA) and ...furfurylamine (fa)/stearylamine (sa). The structure of the benzoxazine monomers has been established using proton nuclear magnetic resonance, carbon nuclear magnetic resonance and Fourier transform infrared spectroscopies. The monomers undergoes thermally activated ring opening polymerization to form polybenzoxazine networks, as revealed by non-isothermal differential scanning calorimetry, and the curing temperature for both was observed to be less than 473 K. Curing parameters of the developed monomers have also been compared with the reported bio-based monomers. The rheological behaviour of PA-fa monomer shows that the monomer has narrow processing window with liquefaction temperature at 426 K and gelation temperature at 437 K. Thermal degradation behaviour of polybenzoxazines was studied using thermogravimetric analysis which reveals that polybenzoxazine based on furfurylamine shows relatively high thermal stability and char yield which is credited to the additional cross-linking sites provided by the furan ring.
Graphic abstract
The performance of solid substrates is not only governed by their molecular constitution, but is also critically influenced by their surface constitution at the solid/gas or solid/liquid interface. ...In here, we critically review the use of orthogonal chemical transformations (so‐called click chemistry) to achieve efficient surface modifications of materials ranging from gold and silica nanoparticles, polymeric films, and microspheres to fullerenes as well as carbon nanotubes. In addition, the functionalization of surfaces via click chemistry with biomolecules is explored. Although a large host of reactions fulfilling the click‐criteria exist, pericyclic reactions are most frequently employed for efficient surface modifications. The advent of the click chemistry concept has led—as evident from the current literature—to a paradigm shift in current approaches for materials modification: Away from unspecific and nonselective reactions to highly specific true surface engineering.
Efficient surface modification is one of the key objectives in modern contemporary material science. The current review highlights the advances in modifying variable surfaces via orthogonal click chemistry. The review is structured by surface type, ranging from metal‐based systems to silicas and silicones as well as polymeric materials and nanometer‐sized organic objects. In addition, the increasingly important immobilization of large biomolecules onto variable surface structures is explored.
In this paper, isothermal and non-isothermal crystallization behaviour of neat polypropylene (PP), blends of PP/maleic anhydride grafted polypropylene (PP-g-MA), and PP/PP-g-MA/polyethylenimine (PEI) ...has been studied by differential scanning calorimetry (DSC). DSC analysis confirmed that PEI promotes crystallization of PP for blends compatibilized with reactive co-agent PP-g-MA, that was confirmed by decreased crystallization time in compatibilized PP-PEI blends as compared to neat PP. The Avrami equation has been used to analyze isothermal crystallization kinetics for all the compositions. Determined Avrami exponent’s (
n
) values confirmed three-dimensional crystal growth in all the samples and PP sample with 1% PEI and 1% PP-g-MA (PP/1PP-g-MA/1PEI) was found to have the least crystallization half time (
t
1/2
)
. In addition to this, activation energy (∆
E
a
) for PP/1PP-g-MA/1PEI blend decreased remarkably as compared to neat PP. The non-isothermal crystallization kinetics was studied by Jeziorny extended Avrami and Mo theories. Application of Jeziorny-Avrami equation showed larger value of
log k’
in case of PP/1PP-g-MA/1PEI indicating enhanced rate of crystallization. Lower value of Mo’s parameter
F(T)
for PP/1PP-g-MA/1PEI than neat PP established higher crystallization rate for the compatibilized blend and hence supported the prior results.
The development of general and more sustainable heterogeneous catalytic processes for Friedel–Crafts (FC) alkylation reactions is a key objective of interest for the synthesis of pharmaceuticals and ...commodity chemicals. Sustainable heterogeneous catalysis for the typical FC alkylation of an easily accessible carbonyl electrophile and arenes or with two different arene nucleophiles in one-pot is a prime challenge. Herein, we present a resolution to these issues through the design and utilization of a mesoporous silica catalyst that has been functionalized with sulfonic acid. For the synthesis of sulfonic acid-functionalized mesoporous silica (MSN-SO3H), thiol-functionalized mesoporous silica was first synthesized by the co-condensation method, followed by oxidation of the thiol functionality to the sulfonic acid group. Sulfonation of mesoporous silica was confirmed by 13C CP MAS NMR spectroscopy. Further, the devised heterogeneous catalysis using MSN-SO3H has been successfully employed in the construction of diverse polyalkanes including various bioactive molecules, viz arundine, tatarinoid-C, and late-stage functionalization of natural products like menthol and Eugenol. Further, we have utilized this sustainable technique to facilitate the formation of unsymmetrical C–S bonds in a one-pot fashion. In addition, the catalyst was successfully recovered and recycled for eight cycles, demonstrating the high sustainability and cost-effectiveness of this protocol for both academic and industrial applications.
We report the functionalization of cross-linked poly(divinylbenzene) (pDVB) microspheres using both thiol−ene chemistry and azide−alkyne click reactions. The RAFT technique was carried out to ...synthesize SH-functionalized poly(N-isopropylacrylamide) (pNIPAAm) and utilized to generate pNIPAAm surface-modified microspheres via thiol−ene modification. The accessible double bonds on the surface of the microspheres allow the direct coupling with thiol-end functionalized pNIPAAm. In a second approach, pDVB microspheres were grafted with poly(2-hydroxyethyl methacrylate) (pHEMA). For this purpose, the residual double bonds on the microspheres surface were used to attach azide groups via the thiol−ene approach of 1-azido-undecane-11-thiol. In a second step, alkyne endfunctionalized pHEMA was used to graft pHEMA to the azide-modified surface via click-chemistry (Huisgen 1,3-dipolar cycloaddition). The surface-sensitive characterization methods X-ray photoelectron spectroscopy, scanning-electron microscopy and FT-IR transmission spectroscopy were employed to characterize the successful surface modification of the microspheres. In addition, fluorescence microscopy confirms the presence of grafted pHEMA chains after labeling with Rhodamine B.
Access to clean and safe water supply remains inadequate in many developing countries. One of the key challenges is to remove pathogenic bacteria from the water supply via effective water ...disinfection technologies to prevent the spread of diseases and to ensure the safety of consumers. Herein, a highly effective point-of-use (on-demand) water disinfection technology, in the form of a polymeric scaffold called macroporous antimicrobial polymeric gel (MAPG), is demonstrated. MAPG is easy to fabricate, completely organic and possess inherent antimicrobial property which makes it non-reliant on inorganic compounds such as silver where the long-term toxicity remains unknown. MAPG is highly bactericidal and can disinfect bacteria-contaminated water (ca. 10
CFU mL
) at a capacity of about >50 times the mass of the organic material used, inactivating >99% of both Gram-negative and Gram-positive bacteria including Escherichia coli, Vibrio cholerae and Staphylococcus aureus within 20 minutes of treatment. When fabricated in a syringe, MAPG eliminates E. coli from contaminated water source by >8.0 log
reduction in bacteria counts (i.e., no viable bacteria were detected after treatment), and the syringe can be reused multiple times without losing potency. The MAPG technology is not only restricted to water disinfection but may also be applicable in other bacteria inactivation applications.
Zwitterionic poly(cysteine methacrylate) was synthesized
via
reversible addition-fragmentation chain transfer polymerization (RAFT) in an aqueous medium. Firstly, cysteine methacrylate was prepared ...by the reaction between cysteine and 3-(acryloyloxy)-2-hydroxypropyl methacrylate in an aqueous medium
via
thiol-Michael reaction. The synthesized monomer was characterized by
1
H and
13
C NMR spectroscopy. Further, the synthesized monomer was used for the preparation of poly(cysteine methacrylate) in the presence of a RAFT agent in an aqueous medium at 70°C. The synthesized poly(cysteine methacrylate) was characterized by
1
H NMR and UV–Vis spectroscopy. The synthesized poly(cysteine methacrylate) exhibited zwitterionic behavior in the pH range 4.0 to 6.9 and showed an upper critical solution temperature at 44°C. Further, the antibacterial assay of the polymer was investigated under acidic and neutral conditions using Gram-negative (
E. coli
) and Gram-positive bacteria (
R. erythropolis
). Poly(cysteine methacrylate) displayed significant antibacterial efficacy under acidic conditions due to the cationic nature of the polymer as compared to the neutral medium. The minimum inhibitory concentrations (MICs) were found to be 70 and 100 µg/mL against
E. coli
and
R. erythropolis
.
Thermal performance of bio-based materials continues to be a vital concern in its path to commercialization and can be alleviated by performing hybridization of organic polymer with inorganic ...functionalities. The objective of the present work is to hybridize bio-based benzoxazine monomers with inorganic siloxane (Si-O-Si) linkage with an aim to develop hybrid thermosets possessing an impressive thermal performance. Hybrid bio-based benzoxazine monomers have been synthesized via Mannich like condensation of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (APTMDS) with phenols of natural origin (cardanol, eugenol, guaiacol and vanillin) and paraformaldehyde using ethanol as environmentally preferable reaction medium. The structural characterization of the monomers has been performed using Fourier transform infrared (FT-IR) and nuclear magnetic resonance (1H, 13C NMR) spectroscopy. The polymerization behavior of the monomer has been evidenced using differential scanning calorimetry (DSC). In addition, rheological measurements were performed to ensure solvent-less processing of the benzoxazine resins. The contact angle measurements has been performed and surface free energy values have been calculated to study the effect of siloxane linkages on the hydrophobicity of hybrid polybenzoxazine. The influence of siloxane linkages on the thermal performance of bio-based polybenzoxazine network has been investigated by thermogravimetric analysis (TGA) which reveals Tmax to be in the range of 490–570 °C and 49–70% char yield for the thermosets. Furthermore, char yield obtained has been utilized to calculate Limiting Oxygen Index (LOI) value, which is an indicative of flame retardancy and was obtained in the range of 37–45 for thermosets. DSC investigation has been performed in order to study the glass transition temperature of the synthesized materials. Moreover, hybrid resins has been explored for adhesive application using standard procedures.
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•Bio-based benzoxazine monomers hybridised with siloxane linkage were prepared.•Methyl substituted siloxane linkage in the monomer shows dilution effect resulting in high polymerization temperature.•Hybrid polybenzoxazine network shows impressive thermal performance, with Tmax in the range of 494 to 576 °C.
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•Nitrogen enriched thermosets have been developed from side-chain type benzoxazine functionalized polyethyleneimine resins.•Thermogravimetric analysis indicates one step degradation ...and Tmax > 347 °C for all thermosets.•Dynamic mechanical analysis of thermosets reveals glass transition value in the range of 56 – 92 °C.•Lap shear strength value has been found to be relatively highest for cardanol based resins.•Nitrogen content of thermosets have been found to be in the range of ~5.4 to 13.7%.
We present a simple methodology to develop nitrogen enriched polybenzoxazine thermosets by integrating polybenzoxazine network with polyethylenimine (PEI). Thermosets have been developed by polymerizing side-chain type resins, which have been prepared by introducing benzoxazine moieties on the amine terminated branches of nitrogen enriched PEI, using cardanol and eugenol as bio-based phenols. The aim of this study is to investigate the potential of benoxazines synthesized using different bio-based phenols and PEI, on the performance of nitrogen enriched thermosets, as well as to contribute in the array of side-chain type benzoxazine resins. The present work is a next leg of our previously reported article on the synthesis of side-chain type benzoxazine resins using guiacol and PEI (G-pei), where the reaction parameters such as reaction medium, time, and stoichiometry were optimized. It is to be noted that, due to relatively better performance of G-pei resins prepared at 8:1:16 and 10:1:20 (phenol: amine: paraformaldehyde) molar ratio, the same stoichiometry has been specifically adopted for the preparation of cardanol and eugenol-based analogous resins in the present work. The functionalization of PEI with benzoxazine as side-chains, has been confirmed using FTIR, 1H, 13C NMR spectroscopy techniques. Polar amine groups as well as alkyl chains of phenols, are expected to alter the polymerization behaviour of oxazine moieties and the same has been investigated using DSC studies, where the curing profiles display exotherms in the temperature range of 208–222 °C. Further, rheological studies suggest solvent-less processing for cardanol based resins. Polybenzoxazine network bonded with polyethyleneimine has been confirmed from FT-IR spectra of cured thermosets, and the nitrogen content has been evidenced from elemental analysis. Furthermore, the thermal stability of the crosslinked materials has been investigated using thermogravimetric analysis (TGA), while the glass transition temperature for the cured specimens has been obtained by dynamic mechanical analysis (DMA). Moreover, polarity associated with the polybenzoxazine network as well as nitrogen enriched amine, is expected to affect the surface property of the end materials, which has been investigated by performing contact angle measurements on the surface of cured thermosets. Lap shear adhesion experiments have been additionally performed using ASTM D1002 standard, and the results indicates relatively good wettability of cardanol based resins.
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