Polymer Science, Series B最新文献

In the present work, a comprehensive study is carried out to use amino acid mixed polyvinyl alcohol (PVA) based hybrid hydrogels as sensing material for detection of folic acid (FA). Thioglycolic acid (TGA) capped cadmium telluride (CdTe) nanostructures were used as dopant to enhance the efficiency and sensitivity of the PVA hydrogels. Three different types of hybrid hydrogels were synthesized using L-phenylalanine (PA), L-leucine (LEU) and L-tyrosine (TYR). Various chemical and physical characterizations were carried out to investigate the properties of TGA/CdTe nanostructures and PVA based hybrid hydrogels. A fluorescence quenching based detection technique was developed to detect the concentrations of FA. From the analysis of these six different hydrogels, it was observed that CdTe doped hybrid hydrogels show the best performance with sensitivity in the range of 0.229 µg/cm³ with limit of detection of 1.86 ng/cm³.

In this study, a new type of raspberry epoxy resin composite particle had been proposed. First, a reaction-induced phase separation method was used to solidify epoxy resin in PPG1000 to prepare homogeneous macromolecular epoxy resin microspheres (EMs). Then, a sol–gel method was used to hydrolyze tetraethoxysilane (TEOS) to prepare nanoparticles of silicon dioxide. In alkaline conditions, the two microspheres were compounded by isocyanate-terminated polyurethane oligomers (PU) to prepare raspberry-shaped EP-PU@SiO₂ composite particles. By adjusting the content of PU, the wettability of the composite particles (110°~156°) can be controlled. The surface morphology of the composite particles was observed via scanning electron microscopy (SEM). The test results indicate that, under the circumstance of the same mass ratio of EMs/SiO₂, when the content of PU is relatively low, there is essentially no SiO₂ attached to the surface of EMs; when the content of PU is relatively high, a raspberry-like structure is observed. Furthermore, the influence of different EMs/SiO₂ mass ratios on the wettability of the composite microspheres was examined. Although the degree of infiltration may differ slightly, it is not significant. This indicates that PU is the decisive factor in controlling the wettability of the EP-PU@SiO₂ composite particles. When the PU content is 400% and the mass ratio of EMs to SiO₂ is 1 : 1, the static water contact angle of the EP-PU@SiO₂ composite microspheres attains the maximum value of 156.2°.

The copolymers of L-lactide and ε-caprolactone are synthesized in the presence of tin(II) ethylhexanoate at 130°C for 72 h. The composition and structure of the products are determined by IR and ¹Н NMR spectroscopy, gel permeation chromatography, and elemental analysis. The molar ratio [monomer] : [initiator] = 4000 : 1 allowed the synthesis of the polymers with an number-average molecular weight of 47 000–66 000 g/mol with the polydispersity index not above 1.6. It was found that during transition from the glassy to highly elastic state, an increase in the content of ε-caprolactone units in the copolymer from 14 to 74 mol % leads to a decrease in the elastic modulus from 1379 to 65 MPa and a decrease in the maximum stress from 33 to 4 MPa. The copolymers containing 27 and 37 mol % of ε-caprolactone units possess plasticity and sufficient strength, which enables their use in medicine and the packaging industry.

Cardo block copolymers containing phenolphthalein-based aromatic polyester blocks and 10–30 wt % of polysulfone blocks have been obtained via low-temperature single-phase polycondensation from commercially available precursors. The obtained block copolymers have been characterized by the methods of IR spectroscopy, GPC, DSC, TGA, and DMA. The processibility of the obtained block copolymers was studied measuring the stability of the melt flow index over time at different temperatures. It has been shown that, depending on the content of the polysulfone blocks, the prepared block copolymers may consist of a single phase with only one variable glass transition temperature or be separated into two macrophases enriched in polysulfone or polyarylate blocks. From the practical point of view, the block copolymers containing 30% of the polysulfone blocks have exhibited good thermomechanical parameters up to 200°C and can be processed through the melt due to its relatively low-viscosity and high temperature stability. Time-temperature parameters of stability of the block copolymer melts have been determined and possible regimes of their processing via injection molding and extrusion have been elucidated.

In this study, we employed two distinct branching coagents to optimize the topology structure of long-chain branched polylactide (LCB-PLA) via melt grafting with 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (Trigonox301) and PLA. Our findings reveal that an impressive 22.8% degree of branching degree in PLA was attainable with the addition of merely 2 wt % allyl glycidyl ether (AGE) and 0.75% Trigonox301. Three mathematical models were applied to quantitatively assess the degree of branching based on molecular weight distribution, zero-shear viscosity η₀, and phase angle. Notably, the presence of gel complicated the precise determination of the branching degree when using LCB_G derived from molecular weight distribution fitting. Comparatively, the η₀ and LCB_C, derived from complex viscosity fitting for LCB-PLA samples enriched with 2 wt % AGE, saw a marked escalation from 2140 Pa s and 0 mol % to 13286 Pa s and 22.8 mol %, respectively.

Furthermore, the preferential end-group reaction between the epoxy group of AGE and the carboxyl group of the PLA molecule chain indicated that AGE was more efficacious in enhancing the branching degree than trimethylolpropane triacrylate (TMPTA).

The possibility of using oxirane and imidazole rings as “anchor” functional groups in the structure of flexible-chain polymers for their reactive mixing has been demonstrated. It has been shown that the obligatory condition for the crosslinking of oxirane- and imidazole-containing polymers is the presence of water in the reaction system. Polymer networks formed similarly from linear water-soluble lactam- and imidazole-containing polymers form stimulus-sensitive hydrogels with ionic conductivity upon swelling in water.

Conductive polymer-based adsorbent such as polyaniline has a great potential in replacing conventional adsorbent to remove heavy metal. In this research, different polyanilines were synthesized by modifying synthesis methods and parameters in expectance to yield different properties, which may affect nickel removal efficiency. Besides, titanium dioxide and carboxymethyl cellulose were added to further improve Ni removal efficiency. All synthesized samples were examined with FTIR and UV–Vis to confirm their chemical structures and oxidation states. The electrical conductivities of the samples were measured on a four-point probe and their crystallographic information and incorporation of metal oxide were confirmed using XRD and EDX respectively. The samples’ thermal stability and morphologies were investigated using TGA and FESEM respectively. Among the different morphologies obtained, nanotubes showed highest Ni removal efficiency of 31.250% as its longitudinal structure allowed easier access of polyaniline active sites to interact with Ni ions. With the incorporation of TiO₂ and carboxymethyl cellulose, the Ni removal efficiency of polyaniline/TiO₂/carboxymethyl cellulose significantly improved to 66.8% with TiO₂ improving the charge transport network and surface roughness while carboxymethyl cellulose provides additional active sites and improved hydrophilicity for the transfer of Ni ions from solution to adsorbent surface.

High-density polyethylene (HDPE) was synthesized using a Ziegler-Natta catalyst in two different ways: one step and two-step processes in a hexane slurry polymerization. The study explored the impact of adding hydrogen as a chain-terminating agent on various properties of the polymer, such as productivity of catalyst, molecular weight distribution variation, melt flow index (MFI) and resin average particle size distribution. The results revealed that increasing hydrogen concentrations led to the production of low-molar mass and high MFI polyethylene in the one-step process. Conversely, decreasing hydrogen concentration and increasing ethylene concentration produced higher molar mass/low MFI polyethylene in the same one-step process. In the two-step process, low-molar mass PE was formed first, followed by high-molar mass PE, resulting in broad molecular weight distribution (MWD). This research provides insights into controlling the molecular weight of polyethylene in slurry polymerization processes, which is significant for industrial polymerization technology.

The synthesis of porous polymeric materials with a high proportion of micropores, including ultramicropores, from a multifunctional branched monomer by the Ni-catalyzed cyclotrimerization reaction followed by heat treatment at 500°C is presented. The textural surface properties of these polymeric materials have been studied. It has been shown that heat treatment at 500°C leads to an increase in the proportion of micropores, including ultramicropores, in the material. The specific surface area was determined, and the adsorption capacity of the obtained compounds was found to be linearly related to the volume of ultramicropores. A sample with the largest volume of ultramicropores had the highest CO₂ adsorption, being 3.12 mmol/g at 273 K and 100 kPa.

Amphiphilic and polyelectrolyte crosslinked polymer products with different types of network structure capable of limited swelling in aqueous media to form hydrogels exhibiting pH-sensitive properties were synthesized by the interaction of tetrazole-containing polysaccharides with the epoxy resin and oxirane-containing carbon chain polymers.