Epoxide-terminated hyperbranched polyether sulphones (EHBPESs) with different backbone structures were synthesized and used as tougheners for diglycidyl ether of bisphenol-A (DGEBA) curing system, which result in nonphase-separated cured networks. Effects of backbone structure (at comparable degree of polymerization) and loading contents on the mechanical and thermal properties of cured hybrids were investigated. The hybrid containing EHBPES3, which has the most flexible backbone, shows the best mechanical performance and highest glass transition temperature (T_g). Compared with unmodified system, the impact strength, tensile strength, elongation at break of the hybrid containing 5% EHBPES3 increased by 69.8%, 9.4%, and 60.2%, respectively. The balanced improvements were attributed to the increased crosslink density and fractional free volume as well as the unique inhomogeneous network structure because of incorporation of hyperbranched modifiers with proper structure and loading contents. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41910.

Diglycidyl ether of bisphenol A (DGEBA)/fluoro-terminated hyperbranched poly(phenylene oxide) (FHPPO) composites with improved mechanical and dielectric performances were prepared by blending a FHPPO with DGEBA. The low-polarity building blocks, abundant fluorinated terminal groups, and the inherent free volume brought by FHPPO efficiently lowered the dielectric constant and the dissipation factor. The free volumes of the cured DGEBA/FHPPO composites, which were quantified by positron annihilation lifetime spectroscopy, increased with the FHPPO loading. The moisture absorption of composites also decreased after the introduction of FHPPO due to the hydrophobicity of fluorinated substituents. Dynamic mechanical analysis tests and scanning electron morphology revealed that FHPPO phase separated from the composites during the curing process. The average diameter of dispersed FHPPO particles increased proportionally with the FHPPO loading. Composites with dispersed particle size of around 150 nm showed the best comprehensive mechanical performance. In addition, incorporation of FHPPO, which has lots of aromatic structures, into DGEBA also increased the thermal stabilities. POLYM. COMPOS., 34:1051–1060, 2013. © 2013 Society of Plastics Engineers

A new epoxy-ended hyperbranched polyether (HBPEE) with aromatic skeletons was synthesized through one-step proton transfer polymerization. The structure of HBPEE was confirmed by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) measurements. It was proved to be one high efficient modifier in toughening and reinforcing epoxy matrix. In particular, unlike most other hyperbranched modifiers, the glass transition temperature (T_g) was also increased. Compared with the neat DGEBA, the hybrid curing systems showed excellent balanced mechanical properties at 5 wt % HBPEE loading. The great improvements were attributed to the increased cross-linking density, rigid skeletons, and the molecule-scale cavities brought by the reactive HBPEE, which were confirmed by dynamical mechanical analysis (DMA) and thermal mechanical analysis (TMA). Furthermore, because of the reactivity of HBPEE, the hybrids inclined to form a homogenous system after the curing. DMA and scanning electron microscopy (SEM) results revealed that no phase separation occurred in the DGEBA/HBPEE hybrids after the introduction of reactive HBPEE. SEM also confirmed that the addition of HBPEE could enhance the toughness of epoxy materials as evident from fibril formation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1064-1073, 2013