Method For Preparation Of Poly Research Articles

Easy and Green Method to Fabricate Highly Thermally Conductive Poly(decamethylene terephthalamide)/Graphite Nanoplatelets Nanocomposite with Aligned Structure.

With the development of miniaturization and integration of electrical and electronic equipment, the heat accumulation problems caused by the long-term operation of devices have become more and more serious. High thermal-conductivity and high-performance plastic composites have attracted significant interest from both academia and industry. Numerous studies have been recently conducted to enhance the thermal conductivity (TC) of nanofiller-filled polymeric composites. However, the homogeneous dispersion and directional arrangement of nanofillers in the resin matrix are the key factors limiting their effectiveness in enhancing thermal conductivity. Based on the feasibility considerations of mass production and industrial application, this paper reports on a novel preparation method of Poly(decamethylene terephthalamide)/graphite nanoparticle (GNP) nanocomposites with high thermal conductivity. Without borrowing solvents or other reagents, this method can effectively strip the inexpensive scaled graphite into nanoscale for its uniform dispersion and orientation arrangement by relying only on mechanical external forces. The whole technology is simple, green, and easy to industrialize. The fillers were well-dispersed and aligned in the PA10T, which played a role in significantly enhancing the thermal conductivity of the PA10T. In addition, we found that the thermal conductivity of the composites reached 1.20 W/(m·K) at 10 wt% filler content, which was 330% higher than that of the pure matrix. The mechanical properties of the composites were also significantly improved. This work provides guidance for the easy fabrication of thermally conductive composites with aligned structures.

Application of Design of Expert software for evaluating the influence of formulation variables on the encapsulation efficacy, drug content and particle size of PEO-PPO-PEO/Poly (DL-lactide-co-caprolactone) nanoparticles as carriers for SN-38.

Hydrophobic substances are mainly encapsulated into polymer nanocarriers in order to improve their solubility, enable their administration, at the same time to empower targeted tissue or cell specific delivery of the drug using the encapsulating vehicle as targeting and controlled release platform. 7-Ethyl-10-hydroxycamptothecin (SN-38) is an active metabolite of Irinotecan, showing 100-fold to 1000-fold higher effect than Irinotecan, but its clinical use is limited because of its extreme hydrophobicity, as it is practically insoluble in most physiologically compatible and pharmaceutically acceptable solvents. In order to fully exploit the potential of the nanoprecipitation as a method for preparation of Poly(DL-lactide-co-caprolactone)-poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) (P(DL)LCL/PEO-PPO-PEO) nanoparticles and evaluate the influence of the polymer P(DL)LCL, stabilizing agent PEO-PPO-PEO copolymer (Lutrol F127) and the drug concentration (SN-38) upon drug entrapment efficiency, size and drug content, a D-optimal experimental design for response surface using Design Expert Version 9.0.4.1. software investigation was created and statistically analyzed. We have observed that at higher SN-38 concentration during the preparation procedure (nanoprecipitation, solvent diffusion method), and due to its extremely low water solubility, the drug will start to precipitate as unprotected crystals at a faster pace compared to polymer aggregation, leading to extremely low encapsulation efficacy and waste of the active compound. The most desirable combination of factor settings are SN-38 = 0.5 mg, Polymer = 5 mg and F127 = 4%. This investigation utilizes the design of experiment approach and extends the primary understanding of impact of formulation development of P(DL)LCL/PEO-PPO-PEO nanoparticles as carriers for SN-38.

Biocomposite foams from poly(lactic acid) and rubber wood sawdust: Mechanical properties, cytotoxicity, and in vitro degradation

ABSTRACTThe objectives of this work were to seek a simple method for preparation of poly(lactic acid) (PLA) foams and evaluate properties of these foams for scaffold application. Using a typical blowing agent and compression molding, biocomposite foams were successfully prepared from a PLA/rubber wood sawdust (PLA/RWS) blend. Selection of RWS for the biocomposites was based on particle size. RWS particles in two size ranges were used: 212–600 μm and ≤75 μm. Alkaline and silane treatments were applied to the RWS before blending with PLA. The tensile properties, Izod impact strength, foam morphology, and thermal degradation of the biocomposite foams were evaluated. Cytotoxicity and in vitro degradation were tested to determine the potential of the biocomposite foam for use as a scaffold in tissue engineering. Silane treatment improved mechanical properties by increasing the interfacial adhesion between PLA and RWS. The density and void fraction of the foam samples had a greater effect on mechanical properties than pore size. Proliferation of MG‐63 cells increased with culture time, indicating that the foam samples were not cytotoxic. Promising samples were tested for degradation in a lysozyme/phosphate‐buffered saline and showed a slow rate of in vitro degradation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48259.

Green Copolymerization of Limonene with β-Pinene Catalyzed by an Eco-Catalyst Maghnite-H+

In this paper, we report a simple method for preparation of poly(limonene-co-β–pinene) using green and low cost catalyst. Copolymers were synthesized by cationic copolymerization by using H+ exchanged Maghnite as a catalyst (Montmorillonite type clay). Several parameters affecting the copolymerization were investigated such as the reaction kinetics, effect of temperature, catalyst mass and effect of monomer feed ratio. The copolymerization in solution leads to the yield 40.5% at −5°C for a reaction time of 6 h. The structure of the obtained copolymer is confirmed by IR and 1H NMR spectroscopy, and differential scanning calorimetry. Finally, a new method for the preparation of poly(limonene-co-β-pinene) in short reaction time was developed, in order to respect the principles of a green chemistry.

A facile solid-state heating method for preparation of poly(3,4-ethelenedioxythiophene)/ZnO nanocomposite and photocatalytic activity.

Poly(3,4-ethylenedioxythiophene)/zinc oxide (PEDOT/ZnO) nanocomposites were prepared by a simple solid-state heating method, in which the content of ZnO was varied from 10 to 20 wt%. The structure and morphology of the composites were characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The photocatalytic activities of the composites were investigated by the degradation of methylene blue (MB) dye in aqueous medium under UV light and natural sunlight irradiation. The FTIR, UV-vis, and XRD results showed that the composites were successfully synthesized, and there was a strong interaction between PEDOT and nano-ZnO. The TEM results suggested that the composites were a mixture of shale-like PEDOT and less aggregated nano-ZnO. The photocatalytic activity results indicated that the incorporation of ZnO nanoparticles in composites can enhance the photocatalytic efficiency of the composites under both UV light and natural sunlight irradiation, and the highest photocatalytic efficiency under UV light (98.7%) and natural sunlight (96.6%) after 5 h occurred in the PEDOT/15wt%ZnO nanocomposite.

Salt effects on formation of microcrystallites in poly(vinyl alcohol) gels prepared by cast-drying method

AbstractThe preparation method of poly(vinyl alcohol) (PVA) gels by a simple cast-drying technique using salt solutions was reported in the present investigation. The effects of the salt concentration on the macro- and microscopic properties were examined in detail, and the relationships between macroscopic properties, such as swelling ratio, mechanical strength, and the network microstructure were presented. It was found that the swelling ratio of PVA cast gel increased largely by adding a small amount of salt, and decreased rapidly, hereafter it increased with increasing the salt concentration above 2% (mass fraction). The changes in the breaking stress and strain corresponded to the changes in the swelling ratio. The macroscopic properties were found to be correlated with the microcrystallites and hydrogen bonds, which were characterized by the measurements using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).

Novel Preparation Method for Poly(l-lactide)-Based Block Copolymers: Extended Chain Crystallites as a Solid-State Macro-Coinitiator

A novel synthetic method for poly(L-lactide) (PLLA)-based diblock copolymers was developed by the use of PLLA extended chain crystallites (or crystalline residues) as a solid-state macro-coinitiator. In this study, we showed one example, i.e., a synthesis of diblock copolymer composed of a crystalline PLLA chain and an amorphous poly(DL-lactide) chain by ring-opening polymerization of DL-lactide initiated with stannous octoate (i.e., tin(II) 2-ethylhexanoate) in the presence of PLLA extended chain crystallites. The PLLA extended chain crystallites were prepared by hydrolytic degradation of crystallized PLLA films at 97 degrees C for 70 h. The chains inside the extended chain crystallites are expected to be protected from transesterfication reaction. Gel permeation chromatography, polarimetry, 1H NMR spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry revealed that the diblock copolymer poly(L-lactide-block-DL-lactide) was successfully prepared without significant transesterification.

One-pot synthesis of PMMA/montmorillonite nanocomposites

AbstractThis article describes simple preparation methods of poly(methyl methacrylate) (PMMA)/synthetic montmorillonite nanocomposites by single-step insitu polymerizations. Compatibility between PMMA and the silicate was ensured by an addition of (3-acrylamidepropyl) trimethylammonium chloride (AAPTMA). The work also compares how different synthetic routes, namely emulsion and solution polymerization, affect the structure as well as thermal and mechanical properties of obtained nanocomposites. The results of structural investigations clearly show, that both the techniques lead to intercalated nanocomposites, but emulsion polymerization allows more effective deflocculating and intercalating of the clay with acrylic copolymers. The addition of small amounts of layered silicates causes an increase in thermal stability and stiffness of the materials. It is demonstrated that at 5 wt. % of the filler, the temperature of 10 % weight loss was shifted up by nearly 50 K in comparison to the neat PMMA. In the same sample, the Young’s modulus of the material was found to be increased by 26 %.

Dependence of optical properties on the preparation methods of poly[(9,9?-dialkylfluorene-2,7-diyl)-alt-(1,3,4-oxadiazole-2,5-diyl)

A blue-light-emissive fluorene-based polyoxadiazole, an n-type polyfluorene derivative, was synthesized by both one-step and two-step methods. Directly polymerized poly[(9,9′-didodecylfluorene-2,7-diyl)-alt-(1,3,4-oxadiazole-2,5-diyl)] (PFOx-DP) exhibited a higher molecular weight and a more efficient photoluminescence quantum yield than poly[(9,9′-didodecylfluorene-2,7-diyl)-alt-(1,3,4-oxadiazole-2,5-diyl)] (PFOx) prepared via a polyhydrazide precursor, poly[9,9′-didodecylfluorene-2,7-(2,5-dihydrazide- 1,3,4-oxadiazole). Both polymers, differently prepared, showed similar photoluminescent properties in 1,2-dichloroethane. However, in a film state, the influence of the interchain interactions on the photoluminescence of PFOx with the lower molecular weight was larger than on the photoluminescence of PFOx-DP. The electron-deficient property of an oxadiazole group in the polymer backbone resulted in low-lying highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of −6.29 and −3.26eV, respectively, of the polymer suitable for electron-transport/hole-blocking layers and emissive layers in multilayer electroluminescence devices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3112–3118, 2004

Novel method for preparation of poly(benzoxazinone-imide)

Novel method for preparation of poly(benzoxazinone-imide)

Novel method for preparation of poly(benzoxazinone-imide)

A novel method was developed to prepare poly(benzoxazinone-imide) by the dealcoholization of poly(amide-imide), having pendent ethoxycarbonyl groups, which was prepared from poly(amide acid). The poly(amide acid) was prepared from the reaction of pyromellitic dianhydride and 4,4'-diamino-6-ethoxycarbonyl benzanilide. The curing behavior of the poly(amide acid) was monitored by DSC, which indicated the presence of two broad endotherms, one with maximum at 153 °C due to imide-ring formation and the other with maximum at 359 °C due to benzoxazinone-ring formation. The poly(amide acid) was thermally treated at 300 °C/1 h to get poly(amide-imide) with pendent ester groups, then at 350 °C/2 h to convert into poly(benzoxazinone-imide) by dealcoholization. Viscoelastic measurements of the poly(amide-imide) showed that the storage modulus dropped at about 280 °C with glass-transition temperature (T g ) at about 340 °C. The storage modulus of poly(benzoxazinone-imide), however, was almost constant up to 400 °C and no T g was detected below 400 °C. Also, the tensile modulus and tensile strength of the poly(benzoxazinone-imide was much higher than that of the poly(amide-imide). The 5% decomposition of poly(benzoxazinone-imide) film was at 535 °C, which reflects its excellent thermal stability. Also, poly(benzoxazinone-imide) showed more hydrolytic stability against alkali in comparison to polyimides.

Preparation of poly( dl-lactide-co-glycolide) nanoparticles by modified spontaneous emulsification solvent diffusion method

Purpose: The objectives of this study were to establish a new preparation method for poly( dl-lactide-co-glycolide) (PLGA) nanoparticles by modifying the spontaneous emulsification solvent diffusion (SESD) method and to elucidate the mechanism of nanoparticle formation on the basis of the phase separation principle of PLGA and poly(vinyl alcohol) (PVA) in the preparation system. Methods: PLGA nanoparticles were prepared by the modified-SESD method using various solvent systems consisting of two water-miscible organic solvents, in which one solvent has more affinity to PLGA than to PVA and the other has more affinity to PVA than to PLGA. The yield, particle size, size distribution and PVA content of the PLGA nanoparticles were evaluated, and the phase separation behaviors of the polymers were elucidated. Results: The modified-SESD method provided a good yield of PLGA nanoparticles over a wide range of composition ratios in the binary mixture of organic solvents. Several process parameters, including the fed amount of PLGA, PLGA concentration and PVA concentration were examined to achieve the optimum preparation conditions. The discrete powder of PLGA nanoparticles was obtained by freeze-drying. No change in the PVA content of PLGA nanoparticles was observed even after several times of washing treatment by ultrafiltration, suggesting a strong surface adsorption. It was found that the appropriate selections of binary solvent mixtures and polymeric concentrations in both organic and aqueous phases could provide excellent yield and favorable physical properties of PLGA nanoparticles. Conclusion: The proposed modified-SESD method can be used to provide PLGA nanoparticles of satisfactory quality at an acceptable yield for industrial purposes.

Preparation of poly(ethylene glycol)–polystyrene block copolymers using photochemistry of dithiocarbamate as a reduced cell-adhesive coating material

This article reports a novel preparation method of poly(ethylene glycol) (PEG)–polystyrene (PST) amphiphilic block copolymers with well-defined block lengths by using photopolymerization of an iniferter, benzyl N,N-diethyldithiocarbamate. PEG macroiniferters, which were prepared by end-capping of PEG monomethyl ethers with benzyl N,N-diethyldithiocarbamate group at one end, were irradiated with UV light in the presence of styrene (ST). NMR analyses showed that the PST block was chain-extended from the PEG block, resulting in the preparation of PEG–PST block copolymers. The number-average molecular weights of the copolymers increased almost linearly with irradiation time, light intensity, and concentration of ST. The polydispersities of the copolymers remained relatively small throughout the reaction ( M w/ M n≈1.3). The composition of two PEG-PST block copolymers thus obtained was as follows: PEG ( M n; 1.9×10 3 g mol -1)–PST (3.0×10 3 g mol -1) and PEG (4.9×10 3 g mol -1)–PST (2.6×10 3 g mol -1). These copolymers were coated onto a poly(ethylene terephthalate) film surface. X-ray photoelectron spectroscopy analyses and water wettability measurements showed that the PST block was enriched at the outermost layer as cast in air, whereas upon immersion into water, the PEG block was oriented toward water. Enhanced wettability was observed for the diblock copolymer with a higher PEG content. Significantly reduced cell adhesion was observed on both the coated surfaces. Thus, the PEG–PST block copolymer may function as a cell adhesion-resistant coating which reduced cell–substrate interaction.

New preparation method of poly(amide‐imide)s using direct polycondensation with thionyl chloride and their characterization

AbstractA study for the development of a new, economical manufacturing process for high‐molecular‐weight poly(amide‐imide) (PAI) was performed via direct polycondensation of trimellitic acid anhydride (TMA) or diimide diacids (DIDAs) with aromatic diamines using an equimolar amount of thionyl chloride in NMP at relatively low temperatures. The polyamidation of DIDAs and diamines for head‐to‐head polymers (H‐PAIs) was sensitive to the reaction temperature and proceeded very quickly, 1 h was sufficient to complete the reaction. The highest value of inherent viscosity, ηinh, of 72 mL g−1 was obtained by polymerization at room temperature. Also several randomly sequenced polymers (R‐PAIs) were prepared by polycondensation from TMA and diamines, followed by imidization with various methods, such as using TPP as a co‐condensing agent, azeotropic dehydration of polyamic acid (PAA) and solid‐state imidization from PAA. Solid state imidization from polyamic acids at 235°C gave satisfactory results with an inherent viscosity 58–85 mL g−1. Solvent content, imidization temperature and time were major controlling factors for the degree of imidization as well as for the molecular weight. Both H‐PAI and R‐PAI showed good mechanical properties with tensile strength of 118–131 MPa and Tg ranged between 263–299°C depending on the nature of monomers. The melt viscosity of the PAIs ranged between 7.4 · 103 and 4.5 · 103 Pa s for H‐PAI and R‐PAI respectively. These values are comparable to that of conventional PAI, Torlon® 4000T of 5.6 · 103 Pa s.

Novel Preparation Method for Poly(2,6-dichloro-1,4-phenylene oxide)

Novel Preparation Method for Poly(2,6-dichloro-1,4-phenylene oxide)