Rheological behaviors of a series of hyperbranched polyethers

Applicability of the Cox-Merz Rule to High-Density Polyethylene Materials with Various Molecular Masses

The Cox-Merz rule is an empirical relationship that is commonly used in science and industry to determine shear viscosity on the basis of an oscillatory rheometry test. However, it does not apply to all polymer melts. Rheological data are of major importance in the design and dimensioning of polymer-processing equipment. In this work, we investigated whether the Cox-Merz rule is suitable for determining the shear-rate-dependent viscosity of several commercially available high-density polyethylene (HDPE) pipe grades with various molecular masses. We compared the results of parallel-plate oscillatory shear rheometry using the Cox-Merz empirical relation with those of high-pressure capillary and extrusion rheometry. To assess the validity of these techniques, we used the shear viscosities obtained by these methods to numerically simulate the pressure drop of a pipe head and compared the results to experimental measurements. We found that, for the HDPE grades tested, the viscosity data based on capillary pressure flow of the high molecular weight HDPE describes the pressure drop inside the pipe head significantly better than do data based on parallel-plate rheometry applying the Cox-Merz rule. For the lower molecular weight HDPE, both measurement techniques are in good accordance. Hence, we conclude that, while the Cox-Merz relationship is applicable to lower-molecular HDPE grades, it does not apply to certain HDPE grades with high molecular weight.

Synthesis of star-shaped polyzwitterions with adjustable UCST and fast responsiveness by a facile RAFT polymerization

We describe crosslinking of polyzwitterions for the formation of novel star-shaped polymers with low polydispersities and dual-responsiveness using RAFT polymerization.

One-Step Preparation of Hyperbranched Polyether Functionalized Graphene Oxide for Improved Corrosion Resistance of Epoxy Coatings

In this paper, hyperbranched polyether functionalized graphene oxide (EHBPE-GO) was prepared by a facile one-step method. Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), thermogravimetric analyzer (TGA), and trans-mission electron microscopy (TEM) results confirmed the formation of EHBPE-GO. Then, EHBPE-GO was cured with phenolic amides at room temperature to prepare epoxy coatings. The corrosion resistance of epoxy coatings was investigated systematically by using electrochemical and traditional immersion methods. Results show that a small amount of EHBPE-GO (8 wt % of Diglycidyl ether of bisphenol A (DGEBA)) in epoxy coating achieves 50% higher improvement in acid-resistance than unmodified neat DGEBA resin. For the nanocomposite epoxy coating, the superior acid-resistance is attributed to the increased crosslink density and the impermeable 2D structure of EHBPE-GO. This work provides a facile strategy to develop the effective improved corrosion resistance nanofiller for epoxy coating.

A series of dendronized hyperbranched polymers with dendritic chromophore moieties in the periphery: convenient synthesis and large nonlinear optical effects

Excellent optical transparency and NLO coefficients were achieved by introducing dendritic chromophore moieties to the periphery of dendronized hyperbranched polymers.

Hierarchical self-assembly of protoporphyrin IX-bridged Janus particles into photoresponsive vesicles

Photoresponsive vesicles formed by PPIX-bridged Janus particles exhibited excellent photostability against intense infrared radiation and good singlet oxygen producing ability.

A water-soluble hyperbranched copolymer based on a dendritic structure for low-to-moderate permeability reservoirs

An excellent matching relationship in size exists between HPDA and the pore throat with a permeability reservoir of under 500–100 mD.