Microwave-assisted Polycondensation Research Articles

A rapid and successful method to synthesis of branched Poly(β-aminoester) as gene carrier system: Microwave-assisted polycondensation

Poly (β-amino ester)s (PBAEs) which are the efficient carriers for gene and drug delivery, synthesize by conventional polycondensation in a very long reaction time. The goal of this study is to shorten the reaction time without decreasing the efficacy of PBAE. For this purpose usability of microwave irradiation in the synthesis of the PBAE was investigated for the first time. The structural characterization of PBAE was realized using FTIR and 1H NMR, and its molecular weight was determined by the GPC-SEC. PBAE nanoparticles (nPBAEs) were also prepared and their physicochemical characteristics were determined. The transfection efficiency of nPBAE were determined on the Human Embryonic Kidney 293T (HEK293T) and Primary Ovine Fibroblast (POF) cells. All results were evaluated in comparison with those of the conventional product (PBAEc) as reference product. It was observed that both PBAE and PBAEc have same molecular structure and similar efficiency. This study revealed that PBAE was successfully synthesized by microwaves without decreasing its efficiency. When the synthesis of PBAE carried out by microwaves compared with conventional method, the reaction time and the consumed energy dramatically reduced from 48 h to 10 min and from 1.5 kWh to 0.032 kWh respectively.

Construction of polyimide structures containing iron(ii) clathrochelate intercalators: promising materials for CO2 gas uptake and salient adsorbents of iodine from gaseous and liquid phases

Three novel imide-iron(ii) clathrochelate copolymers (ACP1–3) were synthesized via a microwave-assisted polycondensation reaction employing a specially designed diamine iron(ii) clathrochelate surrogate with various aromatic dianhydride derivatives.

On the role of polymeric hydrogels in the thermal response of gold nanorods under NIR laser irradiation.

Hydrogels are 3D cross-linked networks of polymeric chains designed to be used in the human body. Nowadays they find widespread applications in the biomedical field and are particularly attractive as drug delivery vectors. However, despite many good results, their release performance is sometimes very quick and uncontrolled, being forced by the high in vivo clearance of body fluids. In this direction, the development of novel responsive nanomaterials promises to overcome the drawbacks of common hydrogels, inducing responsive properties in three-dimensional polymeric devices. In this study, we synthesized and then loaded gold nanorods (Au NRs) within an agarose-carbomer (AC)-based hydrogel obtained from a microwave-assisted polycondensation reaction between carbomer 974P and agarose. The photothermal effect of the composite device was quantified in terms of maximum temperature and spatial-temporal temperature distribution, also during consecutive laser irradiations. This work shows that composite Au NRs loaded within AC hydrogels can serve as a stable photothermal treatment agent with enhanced photothermal efficiency and good thermal stability after consecutive laser irradiations. These results confirm that the composite system produced can exhibit an enhanced thermal effect under NIR laser irradiation, which is expected to lead to great therapeutic advantages for the localized treatment of different diseases.

Determination of the Absolute Configuration of Bioactive Indole-Containing Pyrazino[2,1-b]quinazoline-3,6-diones and Study of Their In Vitro Metabolic Profile.

In recent decades, fungi-derived naturally occurring quinazolines have emerged as potential drug candidates. Nevertheless, most studies are conducted for bioactivity assays, and little is known about their absorption, distribution, metabolism, and elimination (ADME) properties. To perform metabolic studies, the synthesis of the naturally occurring quinazolinone, fiscalin B (1), and its chloro derivative, 4-((1H-indol-3-yl)methyl)-8,10-dichloro-1-isobutyl-1,2-dihydro-6H-pyrazino[2,1-b]quinazoline-3,6(4H)-dione (2), disclosed as an antibacterial agent, was performed in a gram scale using a microwave-assisted polycondensation reaction with 22% and 17% yields, respectively. The structure of the non-natural (+)-fiscalin B was established, for the first time, by X-ray crystallography as (1R,4S)-1, and the absolute configuration of the naturally occurring fiscalin B (-)-1 was confirmed by comparison of its calculated and experimental electronic circular dichroism (ECD) spectra as (1S,4R)-1. in vitro metabolic studies were monitored for this class of natural products for the first time by ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS). The metabolic characteristics of 1 and 2 in human liver microsomes indicated hydration and hydroxylation mass changes introduced to the parent drugs.

In-situ molecular-level hybridization enabling high-sulfonation-degree sulfonated poly(ether ether ketone) membrane with excellent anti-swelling ability and proton conduction

Sulfonated poly(ether ether ketone) (SPEEK) membrane with high sulfonation degree (SD) is a promising substitute of Nafion as proton exchange membrane (PEM), due to the excellent proton conductivity and low cost. However, its widespread application is limited by the inferior structural stability. Here, we report the fabrication of high SD SPEEK membrane with outstanding structural stability through an in-situ molecular-level hybridization method. Concretely, the ionic nanophase of SPEEK membrane is filled with precursors, which are then in-situ converted into polymer quantum dots (PQDs) by a microwave-assisted polycondensation process. In this manner, the micro-phase separation structure of SPEEK membrane is well maintained. PQDs with abundant hydrophilic functional groups together with the inherent –SO3H groups impart hybrid membrane highly enhanced proton conductivity of 138.2 mS cm−1 at 80 °C, which is comparable to Nafion. This then offers a 116.3% enhancement in device output power. Meanwhile, PQDs act as cross-linkers via generated electrostatic interactions with SPEEK, affording hybrid membrane with SD of 94.1% an ultralow swelling ratio of 1.35% at 25 °C, about 35 times lower than control membrane. More importantly, the in-situ molecular-level hybridization method is versatile, which can also boost the performances of chitosan (CS)-based membranes.

Hydrophobically modified guar gum films for wound dressing

Hydrophobically modified guar gum (HMG) was prepared by microwave-assisted polycondensation of naturally abundant guar gum (GG) and dimer acid (DA) following green chemistry principles. HMG was blended with polyvinyl alcohol (PVA) along with gentamicin sulphate (a hydrophilic antibacterial drug) or amoxicillin (a hydrophobic antifungal drug) to obtain drug-loaded films. The two films were characterized by FTIR spectroscopy, X-ray diffraction analysis and scanning electron microscopy. Water absorbency, drying time (water holding time) and vertical wicking time were also determined. The results suggest that the drug-loaded films, HMGA with amoxicillin and HMGG with gentamicin sulphate, could retain moisture for 5–7 h and easily absorb wound exudates. Drug release data were analysed using first-order, Higuchi, Hixson–Crowell and Korsmeyer–Peppas kinetic models and reveal that the HMG-based films exhibit good drug delivery efficiency for hydrophobic as well as hydrophilic drugs. The results of agar diffusion method indicate the two films to exhibit significant resistance toward bacterial (Staphylococcus aureus and Escherichia coli) and fungal (Candida albicans) growth. In vivo wound healing studies on Wistar albino rats show almost full wound closure within 15 days. These results demonstrate the HMG-based drug-loaded films to be promising candidates to serve as biodegradable wound dressing.

Improved synthesis and properties of BTDA-TDI/MDI ternary copolyimides via microwave-assisted polycondensation

Polyimides are usually synthesized over a long period of time, and the process is complex. In order to shorten the synthesis time and simplify the process, we developed an improved synthesis method, namely, microwave-assisted polycondensation. The 3,3′-4,4′-benzophenone tetracarboxylic dianhydride (BTDA)–2,4-tolylene diisocyanate (TDI)/1,1′-methylenebis(4-isocyanatobenzene) (MDI) ternary copolyimides prepared in this work have been synthesized using microwave heating at rather short reaction times (15 min), without the need for either the once-off addition of TDI/MDI or the drop-wise addition of that mixture. The structure of the desired ternary copolyimide was confirmed by proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. Its glass-transition temperature is above 400°C, and the temperature for 5% thermal loss under nitrogen atmosphere is 508.8°C. The tensile strength is 141 MPa, which shows that the microwave-assisted copolyimide has excellent heat resistance and mechanical properties.

Microwave-assisted polycondensation for screening of organically-modified TiO2/SiO2 catalysts

Development of efficient and environmental-friendly solid catalysts is an important target for polyester production. Herein, we report a novel screening strategy based on microwave-assisted polycondensation and its application for exploring organically-modified TiO2/SiO2 catalysts with varied chemical composition and organic functionality. Modification of TiO2/SiO2 catalysts with specific organic groups resulted in superior polycondensation performance at a reduced amount of titanium. Among these, phenylethyl modification was found to be most promising, which exhibited at least 9 and 19 times higher activity than industrial TiO2/SiO2 and Sb2O3 catalysts. The phenylethyl modification during coprecipitation led to smaller catalyst particles with improved hydrophobicity, and the dilution of surface titanium sites by silicon atoms for enhanced Lewis acidity. Synergistic combination of these positive consequences realized the high activity of the developed catalyst, particularly at low temperature.

Electronic Interactions in Illuminated Carbon Dot/MoS2 Ensembles and Electrocatalytic Activity towards Hydrogen Evolution.

The preparation, characterization, and photophysical and electrocatalytic properties of carbon dot (CD)/MoS2 ensembles is reported. Based on electrostatic interactions, ammonium-functionalized MoS2 , which was prepared upon reaction of 1,2-dithiolane tert-butyl carbamate with MoS2 followed by acidic deprotection, was coupled with CDs bearing multiple carboxylates on their periphery, as derived upon microwave-assisted polycondensation of citric acid and ethylenediamine followed by alkaline treatment. Insights into electronic interactions between the two species within CD/MoS2 ensembles emanated from absorption and photoluminescence titration assays. Efficient fluorescence quenching of CDs by MoS2 was observed and attributed to photoinduced electron/energy transfer as the decay mechanism for the transduction of the singlet excited state of CDs. Finally, the electrocatalytic performance of the CD/MoS2 ensemble was assessed towards the hydrogen evolution reaction and found to be superior to that of individual CDs species.

The Synthesis of RGD-functionalized Hydrogels as a Tool for Therapeutic Applications

The use of polymers as biomaterials has provided significant advantages in therapeutic applications. In particular, the possibility to modify and functionalize polymer chains with compounds that are able to improve biocompatibility, mechanical properties, or cell viability allows the design of novel materials to meet new challenges in the biomedical field. With the polymer functionalization strategies, click chemistry is a powerful tool to improve cell-compatibility and drug delivery properties of polymeric devices. Similarly, the fundamental need of biomedicine to use sterile tools to avoid potential adverse-side effects, such as toxicity or contamination of the biological environment, gives rise to increasing interest in the microwave-assisted strategy. The combination of click chemistry and the microwave-assisted method is suitable to produce biocompatible hydrogels with desired functionalities and improved performances in biomedical applications. This work aims to synthesize RGD-functionalized hydrogels. RGD (arginylglycylaspartic acid) is a tripeptide that can mimic cell adhesion proteins and bind to cell-surface receptors, creating a hospitable microenvironment for cells within the 3D polymeric network of the hydrogels. RGD functionalization occurs through Huisgen 1,3-dipolar cycloaddition. Some PAA carboxyl groups are modified with an alkyne moiety, whereas RGD is functionalized with azido acid as the terminal residue of the peptide sequence. Finally, both products are used in a copper catalyzed click reaction to permanently link the peptide to PAA. This modified polymer is used with carbomer, agarose and polyethylene glycol (PEG) to synthesize a hydrogel matrix. The 3D structure is formed due to an esterification reaction involving carboxyl groups from PAA and carbomer and hydroxyl groups from agarose and PEG through microwave-assisted polycondensation. The efficiency of the gelation mechanism ensures a high degree of RGD functionalization. In addition, the procedure to load therapeutic compounds or biological tools within this functionalized network is very simple and reproducible.

From lignocellulosic biomass to lactic- and glycolic-acid oligomers: a gram-scale microwave-assisted protocol.

The conversion of lignocellulosic biomass into platform chemicals is the key step in the valorization of agricultural waste. Of the biomass-derived platform chemicals currently produced, lactic acid plays a particularly pivotal role in modern biorefineries as it is a versatile commodity chemical and building block for the synthesis of biodegradable polymers. Microwave-assisted processes that furnish lactic acid avoid harsh depolymerization conditions while cutting down reaction time and energy consumption. We herein report a flash catalytic conversion (2 min) of lignocellulosic biomass into lactic and glycolic acids under microwave irradiation. The batch procedure was successfully adapted to a microwave-assisted flow process (35 mL min(-1) ), with the aim of designing a scalable process with higher productivity. The C2 and C4 units recovered from the depolymerization were directly used as the starting material for a solvent and catalyst-free microwave-assisted polycondensation that afforded oligomers in good yields.

Microwave-assisted polycondensation of 4-octylaniline with dibromoarylene

The Pd-catalyzed polycondensation of 4-octylaniline with various dibromoarylenes was carried out under microwave heating. Microwave heating led to a decrease in the reaction time and an increase in the molecular weight of the polymers as compared to conventional heating. Microwave heating also allowed the catalyst loading to be reduced to 1 mol %, yielding polymerization results that were comparable to those under conventional heating and 5 mol % catalyst. Investigations regarding field-effect transistors and organic photovoltaic cells using the obtained poly(arylamine) with azobenzene units revealed that increasing the molecular weight of the polymer led to improved device performance, including hole mobility and power conversion efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 536–542

Microwave-Assisted Polycondensation via Direct Arylation of 3,4-Ethylenedioxythiophene with 9,9-Dioctyl-2,7-dibromofluorene

For synthesis of π-conjugated polymers, polycondensation via direct arylation reactions of C–H bonds in aromatic monomers with dibromo-arylenes has attracted increasing attention as a simple synthetic method in which the preparation of organometallic reagents is unnecessary. To develop direct arylation polycondensation for practical use in the synthesis of optoelectronic polymer materials, microwave-assisted reactions were investigated and optimized in terms of a kind of base, concentration, reaction time, and amount of catalyst. Under the optimized conditions, the microwave-assisted direct arylation of 3,4-ethylenedioxythiophene with dibromofluorene for 30 min with catalyst (1 mol %) gave the corresponding polymer with an extremely high molecular weight up to 147 000. The high molecular weight of the polymer enables formation of a large and flexible self-standing film, leading to an advantage in fabricating organic thin-film devices. The elemental analysis and MALDI-TOF-MS reveal that the polymer has hig...

Optically Active, Amphiphilic Poly(meta-phenylene ethynylene)s: Synthesis, Hydrogen-Bonding Enforced Helix Stability, and Direct AFM Observation of Their Helical Structures

Optically active, amphiphilic poly(meta-phenylene ethynylene)s (PPEa) bearing L- or D-alanine-derived oligo(ethylene glycol) side chains connected to the backbone via amide linkages were prepared by microwave-assisted polycondensation. PPEa's exhibited an intense Cotton effect in the π-conjugated main-chain chromophore regions in various polar and nonpolar organic solvents due to a predominantly one-handed helical conformation stabilized by an intramolecular hydrogen-bonding network between the amide groups of the pendants. The stable helical structure was retained in the bulk and led to supramolecular column formation from stacked helices in oriented polymer films as evidenced by X-ray diffraction. Atomic force microscopy was used to directly visualize the helical structures of the polymers in two-dimensional crystalline layers with molecular resolution, and, for the first time, their absolute helical senses could unambiguously be determined.

Simple and efficient microwave-assisted polycondensation for preparation of chiral poly(amide-imide)s having pendant phenol moiety

Chiral bisaminoacids were synthesized by interaction of pyromellitic dianhydride with different aminoacids (phenylalanine, leucine, isoleucine, valline and alanine) in boiling glacial AcOH. Polycondensation of prepared bisaminoacids with aromatic diamine, containing pendant hydroxyl-groups, was carried out in molten tetrabutylammonium bromide under action of microwave irradiation. With yields 88–96% were prepared optically active polyamidoimides (PAIs), having inherent viscosities from 0.30 to 0.58 dL/g (0.5% solution in DMF, 25°C) and [α]58925= −28...−48 deg. As shown X-ray diffraction and emission scanning electron microscopy, PAIs are nanostructured and amorphous polymers.

Bis(nitrone) as crosslinking agent for unsaturated polyesters via 1,3-dipolaric cycloaddition

The microwave-assisted polycondensation of maleic anhydride and 1,6-hexanediol was carried out using p-toluenesulfonic acid as catalyst. The resulting unsaturated polyester was characterized using Fourier transform infrared (FTIR) and 1H NMR spectroscopy, and the molecular weight determined using gel permeation chromatography. 4,4′-Decanediyldioxydi(N-methyl-p-phenylenenitrone) was chosen as a model compound for the crosslinking of the unsaturated polyester. The crosslinking, which is known to proceed via 1,3-dipolaric cycloaddition, was followed using differential scanning calorimetry. Additionally, the kinetics of the cycloaddition was evaluated at 120 °C using FTIR spectroscopy. Copyright © 2012 Society of Chemical Industry

Optically active: microwave-assisted synthesis and characterization of l-lysine-derived poly (amide-imide)s

L-lysine hydrochloride was transformed to ethyl L-lysine dihydrochloride. This salt was reacted with trimellitic anhydride to yield the corresponding diacid (1). Microwave-assisted polycondensation results a series of novel Poly (amide-imide)s (PAI (a-i)). These polymers have inherent viscosities in the range of 0.23-0.66 dl g(-1), display optical activity from +8.02 to +15.11 (as there is no obvious regioselectivity between alpha and epsilon amino groups of the chiral diacid during the polymerization step then random orientation of diacid moieties along the polymer backbone can be predicted and the concept of "tacticity" cannot be addressed in this research), and are readily soluble in polar aprotic solvents. They start to decompose (T (10%)) above 362°C and display glass-transition temperatures at 119-153°C. All of the above polymers were fully characterized by UV, FT-IR and (1)H NMR spectroscopy, elemental analysis, thermogravimetric analyses, DSC, inherent viscosity measurement and specific rotation.

Microwave-assisted synthesis and characterization of some optically active poly(ester-imide) thermoplastic elastomers

AbstractPyromellitic dianhydride (1) was reacted with L-leucine (2) to result in [N,N'-(pyromellitoyl)-bis-L-leucine diacid] (3). This compound (3) was converted to N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride (4) by reaction with thionyl chloride. The microwave-assisted polycondensation of this diacid chloride (4) with polyethyleneglycol-diol (PEG-200) and/or three synthetic bisphenols furnish a series of new PEIs and Co-PEIs in a laboratory microwave oven (Milestone). The resulting polymers and copolymers have inherent viscosities in the range of 0.31- 0.53 dl g-1. These polymers are optically active, thermally stable and soluble in polar aprotic solvents such as DMF, DMSO, NMP, DMAc and sulfuric acid. All of the above polymers were fully characterized by IR spectroscopy, 1H NMR spectroscopy, elemental analyses, specific rotation and thermal analyses. Some structural characterizations and physical properties of these optically active PEIs and Co-PEIs are reported.

Microwave irradiation as a versatile tool for increasing reaction rates and yields in synthesis of optically active polyamides containing flexible l-leucine amino acid

In this investigation, a series of thermally stable and optically active polyamides (PA)s containing bulky pendant chiral functionality from polymerization of a diacid monomer containing rigid phthalimide and flexible L-leucine groups, (2S)-5-[4-(4-methyl-2-phthalimidylpentanoylamino)benzoylamino]isophthalic acid with several aromatic and aliphatic diisocyanates such as 4,4'-methylenebis(phenyl isocyanate), toluylene-2,4-diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate under gradual heating method were prepared and compared with microwave-assisted polycondensation method. The polymerization reactions occurred rapidly under microwave irradiation and produced a series of PAs with good yields and moderate inherent viscosities of 0.26-0.68 dL/g. All of the new PAs showed good solubility and were readily dissolved in aprotic organic solvents. The resulting polymers were characterized by FT-IR, (1)H NMR spectroscopy, and elemental analysis technique. Thermal stability and thermal properties of PAs were evaluated by thermogravimetric analysis and differential scanning calorimetry. The interpretation of kinetic parameters (E, Delta H, Delta S, and Delta G) of thermal decomposition stages have been evaluated using Coats-Redfern equations.

Microwave-assisted synthesis and characterization of optically active poly (ester-imide)s incorporating l-alanine

Pyromellitic dianhydride (1) was reacted with L-alanine (2) to result [N,N'-(pyromellitoyl)-bis-L-alanine diacid] (3). This compound (3) was converted to N,N'-(pyromellitoyl)-bis-L-alanine diacyl chloride (4) by reaction with thionyl chloride. The microwave-assisted polycondensation of this diacyl chloride (4) with polyethyleneglycol-diol (PEG-200) and/or three synthetic aromatic diols furnish a series of new PEIs and Co-PEIs in a laboratory microwave oven (Milestone). The resulting polymers and copolymers have inherent viscosities in the range of 0.31-0.53 dl g(-1). These polymers are optically active, thermally stable and soluble in polar aprotic solvents such as DMF, DMSO, NMP, DMAc, and sulfuric acid. All of the above polymers were fully characterized by IR spectroscopy, (1)H NMR spectroscopy, elemental analyses, specific rotation and thermal analyses. Some structural characterizations and physical properties of these optically active PEIs and Co-PEIs have been reported.