Progress in synthesis, modification, characterization and applications of hyperbranched polyphosphate polyesters

Hyperbranched polyphosphate polyesters (HPPs) as a special class of hyperbranched polymers have attracted increased interest and have been intensively studied, because of peculiar structures, excellent biocompatibility, flexibility in physicochemical properties, biodegradability, water soluble, thermal stability, and mechanical properties. HPPs can be divided into phosphates as monomers and phosphates as end groups. In this article, the classification, general synthesis, modifications, and applications of HPP are reviewed. In addition, recent developments in the application of HPP are described, such as modified or functionalized by end capping and hypergrafting to improve the performances in polymer blends, coatings, flame retardant, leather. Furthermore, the modifications and application of HPPs in biomedical materials, such as drug delivery and bone regeneration were discussed. In summary, the hyperbranched polymer enlarges its application range and improves its application performance compared with conventional polymer. In the future, more new HPPs composite materials will be developed through hyperbranched technique. This review of HPPs will provide useful theoretical basis and technical support for the development of new hyperbranched polymer material.

Feasibility of polyethylene composites reinforced by distillers dried fibers with solubles (DDFS) after different generations of ethanol fermentation

In order to effectively evaluate the distillers dried fibers with solubles (DDFS) obtained from biorefinery processes, sorghum distiller (SD), cassava distiller (CD) and corn cob distiller (CCD) residuals from different generation bioethanol plants were used as the reinforcing phase for polyethylene composites. The mechanical performances and the physical properties of the polyethylene/DDFS composites were evaluated. The results showed that the CCD reinforced specimen offered the best mechanical performances, with a flexural strength of 21.8 ± 2.2 MPa and a tensile strength of 39.7 ± 3.2 MPa. After multigelation, the retention ratios of the rupture modulus and the elasticity modulus of the CCD reinforced specimen reached 88.7 ± 6.7% and 84.1 ± 2.7%, while after 2000 h of xenon lamp weathering they reached 96.2 ± 4.7% and 82 ± 1.8%, respectively. Hybridizing the biorefinery process with the process of composites production was feasible.

Flowchart of the process for prepares polyethylene/DDFS composites. Solid residuals after 1 G, 1.5 G and 2 G SSF bioethanol plants were used as the reinforcement.

Synthesis of a novel polyphosphate and its application with APP in flame retardant PLA

A phosphorus-containing flame retardant was synthesized via an A₂ + B₃ type reaction of bisphenolic acid-based monomer and phosphorus oxychloride. Then, intumescent flame retardant systems were prepared by combining PFRS with ammonium polyphosphate.

Influence of selective solvents on self-assembly behaviors of amphiphilic hyperbranched poly(aryl ether ketone)-graft-poly(ethylene glycol) rod–coil copolymer

An amphiphilic hyperbranched poly(aryl ether ketone)- graft-poly(ethylene glycol) (HPAEK- graft-PEG) rod–coil copolymer was synthesized by grafting linear PEG onto hydroxyl-terminated HPAEK (OH-HPAEK). The molecular structure, the number-average molecular weight and the thermal properties of HPAEK- graft-PEG were characterized by proton nuclear magnetic resonance and Fourier transform infrared spectroscopies, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis, respectively. The self-assembly behaviors of HPAEK- graft-PEG in the mixed solvents were investigated by transmission electron microscopy and scanning electron microscopy. The results demonstrated that the selective solvent in the used mixed solvents exerted remarkable influence on the morphology of the resulting micelles. When the mixed solvents were water/tetrahydrofuran (THF), trichloromethane/THF, and toluene/THF, that is, with the decrease of the selective solvents in polarity, HPAEK- graft-PEG could self-assemble into the regular microspheres with obvious core–shell structure, the similar quadrilateral-shaped micelles with the dimension of about 20 nm and the large complicated clew-shaped micelles, as well as the irregular large compound micelles, respectively. It is worth mentioning that the similar quadrilateral-shaped micelles were different from the toroidal micelles reported already, which had relatively obvious “angle”. The phenomenon may be ascribed that the rigid characteristic of rod HAPEK segment was conducive to the maintenance of the metastable state.

Synthesis and characterization of hyperbranched poly(aryl ether ketone) terminated with phthalonitrile group

A series of novel cross-linkable hyperbranched poly(aryl ether ketone) (HPAEK) polymers (CN-HPAEK n) were synthesized using 2,4′,6-trifluoro-benzophenone as a BB′2 monomer, hydroquinone as an A2 monomer, and 4-nitrophthalonitrile as an endcapping reagent and characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. The average molecular weights of the prepared polymers were determined by gel permeation chromatographic analysis. Thermal cross-linking of CN-HPAEK n, catalyzed by p-bis[4-(4-aminophenoxy)phenyl]sulfone, was then performed via heating their films up to 350°C. The uncured synthesized polymers had good solubility, while the cured samples became insoluble in common organic solvents. Spectra measurement demonstrated trimerization reaction of terminal cyano groups to form triazine rings. The resulting cured samples had high glass transition temperatures and excellent thermal stability with high char yield. Gel content measurements demonstrated that the cured polymers had high cross-linking density, with significantly high gel content of over 95.0%. Thermal mechanical analysis indicated that the cured phthalonitrile resins possessed good thermal mechanical properties at elevated temperatures. These kinds of phthalonitrile resins may be used as a candidate for high-performance polymeric film materials.

An theoretical investigation of reaction site of 2,4′,6-trifluorobenzophenone, 2,4′,6-trifluorophenylsulfone with hydroquinone

A detailed theoretical study for the nucleophilic aromatic substitution reaction of 2,4′,6-trifluorobenzophenone (TF), 2,4′,6-trifluorophenylsulfone (TFS) with hydroquinone was performed at the density function theory level together with the polarizable continuum model. With detailed free energy profiles and transition state structures, our theoretical study confirms that TF or TFS with the para-position fluorine has more thermodynamic and kinetic advantages than that with the ortho-position fluorine. In addition, the calculations involving the local reactivity indices (Fukui function), the global reactivity indices (electronic chemical potential), and rate constants further corroborate the location of the preferred bonding site. The impacts of resonance effect, introductive effect, and steric effect were comprehensively considered to explain the reason why para-position is a good reaction site. Our computational results are in good agreement with experimental results and give the potential polymer materials TFS.

Self-assembly of amphiphilic hyperbranched poly (aryl ether ketone)-block-poly (ethylene glycol) copolymer into microspheres with excellent thermal property

An amphiphilic hyperbranched rod-coil copolymer was synthesized by grafting linear poly (ethylene glycol) (PEG) onto hydroxyl-terminated hyperbranched poly (aryl ether ketone) (OH-HPAEK). The molecular structure, the number-average molecular weight and the thermal properties of HPAEK- block-PEG were confirmed and characterized using proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis, respectively. The microspheres of HPAEK- block-PEG were fabricated by the method of self-assembly, and the morphology and diameter of the obtained microspheres were characterized using transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. The heat-treated experimental results demonstrated that the polymer microspheres possessed excellent thermal property that could stably exist even if heated at 130°C for 10 h. In addition, the diameter of the microspheres can be easily controlled by just adjusting the concentration of the copolymer.

Development of an efficient route to hyperbranched poly(aryl ether ketone)s

A two-step route to an AB2 monomer that underwent polymerization via nucleophilic aromatic substitution to afford fluoro-terminated hyperbranched poly (aryl ether ketone)s (F-HPAEKs) was developed. The synthesis of 2,6-difluoro-4′-hydroxybenzophenone (AB2 monomer) was accomplished by the reaction of 2,6-difuorbenzoyl chloride with anisole, followed by deprotection of the phenolgroup with hydrobromide (HBr) in acetic acid. The polymerization of AB2 monomer in the presence of 4,4′-bis(2, 6-difluoro-benzoyl)diphenyl ether (B4 monomer) as a core molecule afforded F-HPAEKs with number-average molecular weights ranging from 5081 to 9964 Da and polydispersity index values ranging from 2.89 to 3.76. The presence of cyclic oligomeric species, formed by an intramolecular cyclization process, was a contributing factor to the relatively low molecular weights. The degree of branching (DB) of the HPAEK samples was estimated by a comparison of the 19F-NMR spectra of the polymer samples with those of a series of model compounds, and DB values ranging from 0.54 to 0.58 were determined. The glass transition temperatures for HPAEK samples were in the range of 157–176°C, as determined by differential scanning calorimetry.