Polymer Bulletin

A method has been developed for the location of both upper and lower critical cloudpoint curves in miscible polymer blends. Ternary, solvent (1)/polymer (2)/ polymer (3) systems have been used and the phase separation temperatures have been measured in solutions containing a fixed ratio of the two polymers. Extrapolation to zero solvent then gives the critical temperatures for the blend. By measuring these for several blend compositions a miscibility range can be established for a quasi-binary blend of components with specific molecular weights. Using this method, both upper and lower critical temperatures have been established for a polystyrene-poly(vinyl methyl ether) mixture.

Proton relaxation time measurements of chemical crosslinked polystyrenes swollen in protonated and deuterated benzene have been done in order to get informations on the microdynamic behaviour of polystyrene as well as of benzene molecules under the influence of the polymeric network. By means of additional T1d-measurements further evidences for a slow anisotropic motion could be obtained, which cause a T2-“plateau” in the high temperature region. The results are compared with those of MAR-experiments.

Poly(isobutylene-b-ɛ-caprolactone) diblock and poly(ɛ-caprolactone-b-isobutylene-b-ɛ-caprolactone) triblock copolymers have been prepared and characterized. The synthesis involved the living cationic polymerization of IB, followed by capping with 1,1-diphenylethylene or 1,1-p-ditolylethylene and end-quenching with 1-methoxy-1-trimethylsiloxy-2-methyl-propene to yield methoxycarbonyl functional PIB. Hydroxyl end-functional PIB polymers were quantitatively obtained by the subsequent reduction of methoxycarbonyl end-functional PIB with LiAlH4. The structure of hydroxyl end-functional PIBs was confirmed by 1H NMR and IR spectroscopy. Poly(ɛ-caprolactone-b-isobutylene) diblock copolymers and poly(ɛ-caprolactone-b-isobutylene-b-ɛ-caprolactone) triblock copolymers were synthesized by the living cationic ring-opening polymerization of ɛ-caprolactone with hydroxyl end-functional PIB as macroinitiator in the presence of HCl•Et2O via the “activated monomer mechanism”. The block copolymers exhibited close to theoretical Mns and narrow molecular weight distributions.

Nanocomposite hydrogels including chitosan (CS)/polyvinyl alcohol (PVA)/Aloe vera (AV)/zinc oxide nanoparticles (ZnO-NPs) were prepared as a wound dressing. The ZnO-NPs was synthesized using green synthesis method by Matricaria chamomilla leaf extract. The hydrogels were investigated using ultraviolet–visible (UV–Vis), Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM). In addition, other properties such as mechanical properties, swelling ratio, degradation rate, water vapor transmission rate, porosity percentage, cell viability, and antibacterial efficacy of the hydrogels were assessed. The release of synthesized ZnO-Nps from hydrogels was investigated. The results show that the addition of 5 wt.% Aloe vera to CS/PVA, water absorption, and WVTR increased by 276% and 68.98%, respectively. The maximum tensile strength and Young’s modulus were found for the CS/PVA/AV/ZnO hydrogel containing 2 wt.% NPs, increasing by 150% and 28% over CS/PVA hydrogel, respectively. The SEM images revealed the agglomeration of NPs by increasing the ZnO-NPs content, reducing the ZnO-NPs release and skin absorption. Also, the degradation rate decreases by increasing the ZnO-NPs content from 0.5 to 2 wt.%. The cell viability studies showed no toxicity after loading of ZnO-NPs into the hydrogel and showed proper antibacterial activity against Staphylococcus aureus and Escherichia coli.

Herein, we fabricated bead-free isotactic poly(4-methyl-1-pentene) (PMP) nanofiber membranes and characterized their thermo-mechanical properties. PMP nanofiber membranes were electrospun and heat-treated at 180 and 220 °C, and thermally treated under load. The report investigates the effect of thermal treatments on the morphology, degree of crystallinity and mechanical properties, improving the mechanical properties of PMP nanofibers. Prepared nanofibers were investigated by SEM, DSC, XRD and mechanical properties. The mechanical properties demonstrate a tensile strength, an elongation (%) and a Young’s modulus of the nanofiber membranes. The DSC and WAXD analysis shows an increase of degree of crystallinity with thermal treatment. Thermally treated nanofibers under load demonstrate 4.1 times higher tensile strength and 14.1 times higher Young’s modulus than PMP fibrous membrane. Thermally treated nanofibers under load at 200 °C did not retain their structure and fuse with neighboring fibers, because it almost reached the melting temperature of (230 °C).

A living free radical polymerization process was adopted to synthesize a narrow polydispersity fullerene-end-capped polystyrene(NPFECPS). The UV-Vis, DSC, GPC demonstrated that fullerene(C60) was chemically bonded to polystyrene successfully, and C60 was almost monosubstituted. The NPFECPS can be dissolved in a variety of solvents, such as THF, toluene, trichloromethane, and so on. The good photoconductivity is also found for NPFECPS.

The ion-exchange properties of interpenetrating polymer networks (IPNs) have been studied to provide metal-ion transport with high selectivity. Polypropylene (PP) membranes incorporating poly[(ar-vinylbenzyl) trimethylammonium chloride], P(ClVBTA), poly[2-(acryloyloxy)ethyl]trimethylammonium chloride] P(ClAETA), poly(acrylic acid) P(AA), poly(2-acrylamidoglycolic acid) P(AGA), poly(glycidylmethacrylate-N-methyl-d-glucamine) P(GMA-NMG), poly(2-acrylamido-2-methyl-1-propane sulfonic acid) P(AMPS), and poly[sodium (styrene sulfonate)], P(SSNa) were modified via an “in situ” radical-polymerization. The surface of PP was activated by a hydrophilic grafted polyelectrolyte and then pressure injection was used for impregnation of the reactive solution in the membrane. The following conditions were varied: the functional monomer, grafted polyelectrolyte, and cross-linked concentration. The modified PP membranes were characterized using SEM/EDS, FT-IR, electrokinetic potential, and Donnan dialysis for the chromium ion transport. The modified membranes exhibited hydrophilic character with a water-uptake capacity between 15 and 40 % and a percentage of modification between 2.5 and 5.5 % in comparison with the behavior of the unmodified polypropylene membrane as the blank probe. Hexavalent chromium ions were efficiently transported by the modified membranes containing P(ClVBTA) (61.2 %) and only 5.8 % of trivalent chromium were extracted at pH 3.0 using a 1 mol/L NaCl solution as the extraction reagent. Similarly, Cr(III) transport using membranes modified with P(SSNa) achieved 42.1 % extraction at pH 3.0 using 1 mol/L NaCl as the extraction reagent and 2.5 % extraction was achieved for Cr(VI). Unmodified PP membrane shows Cr(VI) extraction percentage between 1.6 and 3.1 %, and Cr(III)extraction percentage between 2.3 and 2.6 %.

Polymer microsphere profile control is a promising approach for the profile control of heterogeneous reservoirs. Matching between polymer microspheres after swelling in water and the reservoir pore throat is crucial for profile control. Hydration equilibrium time and swelling ratio are key properties that are a direct result of water shutoff efficacy. In this paper, a hollow structure microsphere with swelling–deswelling properties is synthesized and its physical properties including morphology, particle size distribution, water swelling property and deswelling property are thoroughly examined. Meanwhile, the displacement performances are studied. The results demonstrate that the hollow structure microspheres have good swelling–deswelling properties at different salt concentrations. Compared with two kinds of polymer microspheres with the same material, the hydration equilibrium time of hollow structure microspheres is longer than that of nonhollow polymer microspheres. Moreover, the hollow structure microspheres have an effect on deep plugging. With the hydration time increasing, the tertiary recovery of the hollow structure microspheres solution is higher than that of nonhollow polymer microspheres solution, whether in a homogeneous medium or in a heterogeneous medium.