We reported herein a novel two-step method combining gel casting and surface crosslinking to fabricate mechanically robust films. Polymer-mediated graphene oxide (GO) films (GOFs) were initially prepared by cast-drying gels containing GO and small amounts of rationally designed polymer, followed by surface crosslinking in EuCl₃ solution. Multiple interactions including hydrogen bonds, π–π interactions, and coordinative bonds were purposefully engineered among GOFs. The resulting GOFs exhibited high strength (112.1 MPa) and toughness (1.7 MJ m⁻³). Moreover, chemical reduction endows these films with high electrical conductivity (21.2 S cm⁻¹), and they could be used as flexible electromagnetic interference shielding materials with a shield effectiveness of 15.9 dB. This method for the fabrication of functional graphene-based films with strength-toughness balance is simple, environmentally friendly, and scalable to industrial levels.

A novel hindered amine ligand, mono-2,2,6,6-tetramethyl-4-piperidyl-succinate (MTPS), has been designed to chelate europium(III) ion with 1,10-phenanthroline (Phen) as a coligand to prepare polymer photostabilizer. The luminescent property of the stabilizer and its efficiency of protecting polymer matrix from photodegradation have also been investigated. Under UV excitation, the stabilizer has red light emission in both ethanol solution and polypropylene (PP) matrix. The PP sheets containing the stabilizer display significantly improved photostability, which may be attributed to MTPS which scavenges radical, as well as Phen which makes the complex dissipate the absorbed ultraviolet light in a harmless manner. These preliminary results demonstrate that the introduction of the stabilizer can endow polymer matrices not only excellent photoluminescent properties but also improved photostability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1399-1405, 2013

Influence of α- and β-nucleation on brittle-ductile transition temperature (BDTT) of impact-resistant polypropylene copolymers (IPCs) and their phase morphologies were comparatively investigated. Impact test showed that the BDTT of β-nucleated IPC (β-IPC) is ∼ 24°C lower than that of α-nucleated one (α-IPC). Structural characterizations including atomic force and scanning electron microscopic observations, small angle X-ray scattering examination, and dynamical mechanical analysis revealed that dispersion of the ethylene-propylene random copolymer-rich (EPR-rich) phase was finer in β-IPC in comparison with that in α-IPC. For the reason of looser lamellar arrangement, the portion of EPR-rich components included in the interlamellar region of β-IPC was higher than those of α-IPC, which led to improved mobility for the amorphous polypropylene chains. It was proposed that the finer distribution of EPR-rich phase, which might result from faster growth rate of the β-crystal and looser lamellar arrangement of β-spherulite, should be responsible for the improved impact-resistance and lower BDTT in β-IPC samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Annealing treatments have been performed on two melt-crystallized polyethylenes (PE) with different topologies, namely highly branched and linear PE, to comparatively investigate the microstructural evolution and corresponding changes of mechanical property. It shows that annealing induced different degrees of variation in the lamellar rearrangement of the two PEs. Branched PE, which incorporates comonomers on the backbones, shows a more versatile annealing effect when compared with the linear counterpart. With respect to PEs, it is for the first time a connection was made between the annealing-induced microstructural changes and an important but less understood property known as heat distortion temperature (HDT). It shows that at lower annealing temperatures, the improvement of HDT can be well correlated to the increased crystallinity induced by lamellar rearrangement for both PEs. However, for branched PE, the contribution of crystallinity is weakened at higher annealing temperatures and the dominant factor on HDT was replaced by the relaxation of lamellar structure. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1347–1359, 2011

In this research, a series of lanthanide complexes with a low molecular weight hindered amine have been synthesized for the first time from lanthanide chloride and bis-(2,2,6,6-tetramethyl-4-piperidinyl)-decanedioicacid (L) by simply using a solvent-free solid-state reaction. Elemental and thermo analysis suggest that the component of the complexes is LnLCl₃ 2H₂O (Ln = Y, La, Nd, Sm, Eu, Gd, Dy, Er). Infrared spectra indicate that the lanthanide ions are coordinated with oxygen atoms of the carbonyl group in ligand. Polypropylene films containing the ligand and complexes were prepared by melt blending and compression molding, and were exposed to UV irradiation before and after ethanol extraction. The measurements of carbonyl index, thermal decomposition temperature, and tensile elongation at break reveal that these complexes have comparable photostabilizing efficiency and improved extraction resistance compared to the ligand alone. This study suggests that hindered-amine lanthanide complexes can provide novel approach to the cheap and efficient light stabilizers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The crystallization conditions dependence of polymorphs composition in β nucleated propylene/ethylene copolymers (PPR) and propylene homopolymers (PPH) were comparatively investigated via wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) measurements. It is interesting to note that the amount of β form as a function of crystallization conditions presents an opposite trend for the β nucleated PPR and the β nucleated PPH under the conditions we investigated. For the β nucleated copolymers, the content of β form shows also an opposite tendency with that of γ form with the change of crystallization conditions. The formation of γ form is preferred under lower cooling rates or higher isothermal crystallization temperatures, whereas the amount of β form increased with increasing the cooling rates or decreasing the isothermal temperatures. This opposite tendency could be interpreted in terms of the competition between the β nucleation ability of β nucleating agent and the γ nucleation action of the comonomer defects. The existing comonomer defects that favor the formation of γ form may suppress the nucleation ability of β nucleating agent. A higher proportion of β form in PPR containing a β nucleating agent could be achieved under faster cooling rates or lower crystallization temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Magnesium salt (M-HOS) whisker and β-nucleating agent were introduced into polypropylene and their effects on the crystalline structures, morphologies, mechanical properties, and thermal resistance of polypropylene (PP) were investigated. The results of wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and polar optical microscopy (POM) examinations suggested that the presence of the whisker did not cause any negative effect on the occurrence of β-modification, and β-phase became absolutely dominant form in β-nucleated samples. The mechanical and thermal properties tests demonstrated that there is an excellent synergy between the β-nucleating agent and the whisker. For PP composite containing 0.1 wt% of the β-nucleating agent and 10 wt% of the whiskers, the Izod notched impact strength, elongation at break, flexural modulus, and heat deflection temperature were increased by 108, 194, 31, and 40%, respectively, compared with those of neat PP. By combining the toughening effect of α–β transition with the reinforcing effect of the whisker, simultaneous improvement in toughness, flexural modulus, and thermal performance of PP was successfully achieved. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The crystalline structure, morphology, and nonisothermal crystallization behavior of isotactic polypropylene (iPP) with and without a novel rare earth-containing β-nucleating agent (WBG) were investigated with wide-angle X-ray diffraction, polar optical microscopy, and differential scanning calorimetry. WBG could induce the formation of the β form, and a higher proportion of the β form could be obtained by the combined effect of the optimum WBG concentration and a lower cooling rate. The content of the β form could reach more than 0.90 in a 0.08 wt % WBG nucleated sample at cooling rates lower than 5°C/min. Polar optical microscopy showed that WBG led to substantial changes in both the morphological development and crystallization process of iPP. At all the studied cooling rates, the temperature at which the maximum rate of crystallization occurred was increased by 8–11°C in the presence of the nucleating agent. An analysis of the nonisothermal crystallization kinetics also revealed that the introduction of WBG significantly shortened both the apparent incubation period for crystallization and the overall crystallization time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Two kinds of β-nucleating agents, named a rare earth complex (WBG) and a N,N′-dicyclohexylterephthalamide (TMB5), were introduced into isotactic polypropylene (iPP), and their effect on crystallization and melting behavior of iPP was comparatively investigated. Wide angle X-ray diffraction measurements revealed that both the two additives were highly effective in inducing β modification. At their respective optimum concentrations of 0.08 wt % for WBG and 0.06 wt % for TMB5, the relative amount of β-form calculated by Turner-Jones equation both exceeds 92%. However, the isothermal crystallization kinetics investigated by differential scanning calorimetry demonstrated that WBG had more pronounced effect than TMB5 in accelerating the overall crystallization rate. The Lauritzen–Hoffman theory analysis also revealed that WBG was more effective not only in increasing the nucleus number but also in accelerating the growth rate of crystallization. After completing isothermal crystallization process, the subsequent melting behavior examination suggested that the addition of WBG expanded the upper limit temperature of forming β modification, and therefore was more effective in delaying the β-α transformation than TMB5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008