International Journal of Polymer Analysis and Characterization最新文献

Four kinds of polypyrrole-thiophene derivatives (PPy-Th) are prepared via solution polycondensation using pyrrole, 3-acylpyrrole, and 2-thenaldehyde as monomers. The structure, molecular weight, micromorphology, thermal degradation, ultraviolet-visible absorption, and luminescence performance of the derivatives are investigated by fourier transform infrared (FTIR), hydrogen nuclear magnetic resonance (¹HNMR) spectroscopy, gel permeation chromatography (GPC), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), and fluorescence spectra. FTIR and ¹HNMR confirm that the derivatives have been successfully fabricated, and GPC indicates that the derivatives belong to oligomers with narrow molecular weight distribution. For acyl-substituted derivatives, the microstructures are mainly lamellar accumulation. Furthermore, under ultraviolet excitation, the derivatives can produce blue or green light emission, corresponding to the transitions of large π electrons in the conjugated structure of the molecular chains. Especially, the maximum emission wavelengths and Stokes shifts of the acyl-substituted derivatives are markedly larger than that of the non-acyl-substituted derivatives. The fluorescence quantum yield and band gap of the PVT are 4.46% and 2.01 eV, respectively. The fabricated PPy-Th can be used as luminescent materials in the development and application of polymer light-emitting diodes.

Some defects of polylactic acid (PLA), especially its poor mechanical properties, were modified using a minimum content of non-biodegradable maleated polypropylene (MAPP). To this end, first, the amount of MAPP was optimized, which was 20 wt.%. Second, MgO was used as a new catalyst to improve the exchange reactions between active groups in both polymers in a reactive blending process. Tensile and izod analyses showed that, compared to neat PLA, with a slight decrease in modulus and tensile strength, elongation at break, and impact resistance were improved in the presence of 20 and 0.1 wt.% of MAPP and MgO, respectively. This improvement in mechanical properties can be related to the exchange reactions between two polymers and the formation of PLA-MAPP block copolymers. MFI and WDCA analyses demonstrated the increase in melt flowability and surface hydrophilicity of the resulting blends, respectively. DSC analysis showed that the T_g values of both polymers approached each other in the presence of catalyst. Also, the elimination of cold crystallization of PLA and the decrease in the T_m and crystallinity of both polymers are clear reasons for the miscibility of the alloy. TEM displayed the proper dispersion of MgO nanoparticles within the polymer matrix, and in addition, the XRD test also proved the decrease in the crystallinity of both polymers and appropriate miscibility of the samples containing 20 and 0.1 wt.% of MAPP and MgO, respectively. These results can promise the design of a compound with the maximum amount of PLA for further use in various industries.

This article describes the study of a thermo-responsive hybrid systems based on polyurethane (PU) modified with sensitive acrylamide derivates. The hybrid systems were synthesized using PU and two acrylamide derivatives (N-isopropylacrylamide (NIPA) and N-isopropylmethacrylamide (NIPMA)) in different proportions. The systems were characterized using infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic light scattering (DLS). Water-uptake capacity and sedimentation rate were also determined. The results showed that the hybrids with 30% acrylamide derivate (AD) showed a T50 of approximately 360 °C indicating that thermal degradation decreased with the addition of NIPA and NIPMA. Additionally, the incorporation of AD increases the glass transition temperature from −34 to −22 °C when 30% AD was used. The hybrids with 30% AD showed a variation in the diameters (above 60%) when the temperature was decreased from 50 to 22 °C. These changes were attributed to the hydrophilic → hydrophobic transition that occurs when measuring below and above the low critical solution temperature (LCST) of the polymer. Furthermore, the extra methyl group in the structure of NIPMA makes the collapse less pronounced than in NIPA, decreasing the relative diameter change by 10%. Sedimentation tests showed that the addition of the hybrid hydrogels in the sand increased the time of decantation by 60%. So, the combination of two thermo-responsive polymers to alter the hydrophilic/hydrophobic balance allows these polymers to modify their conformation at a specific temperature and could be potentially useful as self-suspending support agents or drug delivery systems.

Fabrication of a suitable drug delivery system forms an attractive strategy to overcome the low bioavailability of quercetin. Poly(2-hydroxyethyl methacrylate–co-N-hydroxyethyl acrylamide), P(HEMA-co-HEAA) copolymer samples, and homopolymers of 2-hydroxyethyl methacrylate (PHEMA) and N-hydroxyethyl acrylamide (PHEAA) offer potential as quercetin delivery matrices owing to their favorable properties rendered in this study. Free radical polymerization applied under cryogenic conditions produced the polymer gels. The homopolymers and copolymers are noncytotoxic, porous, soft cryogels with surfaces resistant to protein and HCT-116 cancer cell adhesion. In vitro, quercetin release studies from samples reveal swelling-controlled, zero-order drug release at pH = 7.4 and 37 °C with high cumulative release percentages ranging from 92.03% to 94.82%. The durability of the cryogels and limited quercetin release at pH = 2.0 indicate that these cryogels are promising matrices for successfully delivering quercetin to the small intestine, where its primary absorption occurs.

The article presents research on the thermal decomposition of individual ingredients and compositions that are physical mixtures of emulsion poly(vinyl chloride) (PVC), cadmium yellow, and stearic acid. The results of the tests were TG, DTA, and DTG graphs. From their course, the initial decomposition temperatures, maximum decomposition rate, and final temperatures were determined, and changes in the mass of samples and the values of thermal effects were calculated. The influence of pigment and stearic acid on the thermal decomposition of PVC was investigated. Cadmium yellow, modified in an alkaline medium and containing hydroxyl groups, was also used for the tests. It was found that the presence of both pigment and stearic acid had a retarding effect on the initiation of thermal decomposition of PVC. The addition of CdS modified in an alkaline environment had a more or less similar effect on the initial decomposition temperature of PVC. Depending on the composition of the polymer and the value of the final temperature, different values of thermal effects and the amount of products formed were indicated.

Solid polymer electrolyte blends with varied compositions of poly(ethylene oxide) (PEO)/carboxymethyl cellulose (Na-CMC) in 10/90, 50/50, and 90/10 compositions have been successfully prepared by means of the solution cast technique at room temperature. The modification of the structural, optical, and electrical properties of the prepared blend samples was studied by employing XRD, FTIR, UV-Vis, and electrical impedance spectroscopy methods. X-ray diffraction studies revealed that the crystalline nature gradually transforms into amorphous as the Na-CMC content increases in the sample. The variation of bands noticed in the Fourier transform infrared spectroscope characteristic spectrum of the blends reveals the formation of complexes between the individual polymers. The analysis of optical properties using a UV-Vis spectrometer in the wavelength range of 900–1100nm, shows a gradual decrease in the optical indirect energy band gap with an increase in Na-CMC content in the blend. The study of the electrical properties of the blend carried out in the frequency range 50 Hz–1MHz and temperature range 303K–338K, using an electrical impedance analyzer reveals that, the dielectric constant and loss decrease with the rise in frequency, exhibiting the usual behavior of the polymers. AC conductivity is found to increase with an increase in temperature. The highest value of ionic conductivity is found to be 6.06 × 10⁻³Scm⁻¹ for the blend with a 10/90 composition.

In the present work, a family of functionalized statistical copolymers was synthesized by radical polymerization from a varied composition of benzyl methacrylate (BzMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA) comonomers using 2,2’-azobisisobutyronitrile (AIBN) as initiator. The characterization, identification, and composition analysis of each copolymer were carried out by spectroscopic methods (FTIR and 1H-NMR). Then, different properties were evaluated: molecular size was determined by measurement of intrinsic viscosity [η] in THF at 25 °C and glass transition temperature (Tg) analyzed by differential scanning calorimetry. Films were prepared by the solvent casting method from selected samples with different compositions and their mechanical properties were analyzed by tensile tests. It was observed that the composition of the functionalized copolymers substantially affects their macromolecular and mechanical properties, evidencing greater flexibility when the DMAEMA content in the copolymer increased.

During the blending process, styrene–acrylonitrile–glycidyl methacrylate (SAG) was grafted through in-situ formation of polyamide 66 (PA66) as a compatibilizer for poly (2,6-dimethyl-1,4-phenoxy) (PPO) composites. SAG has an obvious advantage over the PA66/PPO blends in terms of terminal performance in the dynamic rheological analysis. Moreover, the gap between the PA66 and PPO glass-transition temperatures decreases with the SAG content increasing, which indicates improved compatibility. The particle morphology of the PA66/PPO/SAG blends had narrower size distributions and became smaller after adding SAG. In addition, the compatibilization improved the mechanical properties of blends significantly when SAG reached 5 by weight per hundred resins (phr). This is attributed to enhanced interfacial adhesion and a finer dispersion morphology. However, when 7 phr of SAG are added, the exceeded compatibilizer produces a limitation on the improvement of the mechanical properties. Our results indicate that the optimal concentration of the compatibilizer, SAG, is between 3 and 5 phr for PA66/PPO (60/40).

In this research, a series of silicone foam/polytitanosiloxane composites (SF-pTS) were fabricated with hydroxy-, vinyl-, hydrogen-containing polydimethylsiloxanes, and polytitanosiloxane filler in the presence of a platinum catalyst under ambient conditions. The effect of the amount of polytitasiloxane on the micromorphology and flame retardancy of silicone foam was studied, and a relative flame retardancy mechanism was proposed. It could be found that the polytitanosiloxane exhibited a good dispersion level in the silicone foam, thus improving the flame retardancy of the composite. When the content of polytitanosiloxane is 9 wt%, the limiting oxygen index and UL-94 grade of the SF-pTS9 composite are increased to 29.2% and FV-0, respectively. Cone experiment results suggested that the SF-pTS9 possessed relative balanced PHRR (148.9 kW/m²), THR (58.5 MJ/m²), TSP (0.6 m²), and mass residue (83.9%) among the prepared silicone foam materials. This work provides a new avenue to fabricate a silicone foam composite with enhanced flame retardancy.

The emergence of additive manufacturing has enabled scientists to efficiently construct complex geometric forms, facilitating the creation of robust structures with enhanced resistance to external forces. Fused filament fabrication (FFF) enables the attainment of personalization, enhanced design flexibility, waste reduction, expedited prototyping, and the generation of intricate profiles. In this study, an impact test was conducted to measure the energy absorption of polymer composites fabricated through fused filament deposition. Specifically, the composites investigated were poly-lactic acid reinforced with multi-walled carbon nanotubes, carbon fibers, and graphene. The study examined the effects of different infill patterns and infill densities on the energy absorption capabilities of these composites. The utilization of a gyroid infill pattern with a 100% infill density has been found to demonstrate the highest level of energy absorption in the context of graphene-reinforced poly-lactic acid. In order to examine the relationship between the given process parameters and the energy-absorbing behavior, an analysis of variance using Taguchi’s approach is employed on the impact test findings. The examination of fractured surfaces using scanning electron microscopy (SEM) unveiled several types of voids, exhibiting enhanced interlayer adhesion in distinct composite materials. The thermal characteristics of the composite material were determined by the utilization of differential scanning calorimetry (DSC) analysis. The experimental results demonstrate that polymer composites have future potential to be employed in automotive parts that necessitate high impact resistance, such as the fabrication of bumpers and body panels.