Chinese Journal of Polymer Science

This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber (SBR) with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.

The solventnatures are crucial to deeply reveal solution behavior of macromolecular chains, physical essence of condensed state structures formation of the film as well as the photoelectronic devices performance. Based on the second virial coefficient (A2), effect of the synergistic action of solvents and external electric field on both solution behavior and the film’s condensed state structure for the semi-rigid conjugated polymer, poly[2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylvinylene] (MEH-PPV) was investigated by dynamic/static light scattering, photoluminescence spectroscopy and transmission electron microscopy, etc. It was found that although the MEH-PPV solutions with different solvents (toluene, chlorobenzene, chloroform and tetrahydrofuran) all could generate a response to the external electric field, the degree of response varied significantly with the change of solvent nature. Furthermore, ordered degree of the film from the solutions was also obviously different. The essential reason for this responsive difference was firstly revealed in the research, which actually depended on the degree of interaction between the solute and solvent, and this degree of interaction could be quantitatively described by the second virial coefficient (A2). The bigger the A2, the stronger the interaction between solvent and solute in the solution, and the stronger the response to the external electric field. Further, under the induction of external electric field, chains aggregations with different sizes were formed accompanied by large-scale chains ordered structure in the solution. This ordered structure not only can effectively transfer to film prepared by the precursor solution but also is beneficial to enhance the carrier mobility and device efficiency of the photoelectronic film.

Poly(ether urethane)s (PEU), including PEUI15 and PEUH15, were prepared through chain-extension reaction of poly(ethylene glycol) (PEG-1500) using diisocyanate as a chain extender, including isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI). These PEUs were used to toughen polylactide (PLA) by physical and reactive blending. Thermal, morphological, mechanical and aging properties of the blends were investigated in detail. These PEUs were partially compatible with PLA. The elongation at break of the reactive blends in the presence of triphenyl phosphate (TPP) for PLA with PEUH15 or PEUI15 was much higher than that of the physical blends. The aging test was carried out at -20 °C for 50 h in order to accelerate the crystallization of PEUs. The PEUs in the PLA/PEU blends produced crystallization and formed new phase separation with PLA, resulting in the declined toughness of blends. Fortunately, under the aging condition, although PEUH15 in blends could also form crystallization, the reactive blend of PLA/PEUH15/TPP(80/20/2) had higher toughness than the other blends. The elongation at break of PLA/PEUH15/TPP(80/20/2) dropped to 287% for the aging blend from 350% for the original blend. The tensile strength and modulus of PLA/PEUH15/TPP blend did not change obviously because of the crystallization of PEUH15.

Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials. In this paper, we addressed the effects of solvent vapor annealing, including chloroform and water vapor, on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1 (PB-1) by means of in situ Fourier transform infrared spectroscopy (FTIR). The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity. Also, a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.

Transparent ZrO2-polyurethane nanocomposites with high refractive index were prepared by dispersing ZrO2 nanoparticles in a polyurethane matrix via ligand molecule engineering. TEM showed that the inorganic particles were well dispersed within the polymeric network with no significant macroscopic agglomeration. By controlling the phase separation it was possible to obtain transparent zirconia nanostructured coatings, characterized by improved mechanical and thermal properties. UV-Vis spectra indicated that the coatings still maintained transparency in the visible light. The refractive index of the UV-cured films depends linearly on the ZrO2 content and varies from 1.475 to 1.625 (20 wt%) at 633 nm. These coatings could find advanced applications in coatings of optical and electronic devices.

Flexible electronic devices based on reversible bonds for self-curing capabilities arouses extensive interest. However, most of the composite conductive elastomers have the problems of poor mechanical properties and slow recovery of mechanical properties during multiple stretching, which hinder their stability in continuous operation. In this study, hyperbranched-MWCNTs/hyperbranched-PDMS self-healable conductive elastomers inspired by cephalopods were successfully developed. The prepared conductive elastomer exhibited good self-healing ability (91%) at room temperature excited by multiple reversible interactions. The prepared elastomer showed outstanding mechanical properties and anti-fatigue ability, so that it can cope with more arduous tasks. Moreover, the elastomer was sensitive to the change of stress states and can be used as a stable strain sensor. Therefore, the self-repairing conductive elastomer has potential practicability in the fields of human-computer interaction, motion monitoring, soft robot and so on.

Commercial tissue adhesives have been widely applied in wound hemostats and dressings while enhancing the hemostasis and healing capabilities is challenging to meet clinical needs. Herein, we designed the glucose- and catechol-functionalized derivatives from commercial ε-polylysine (EPL) and prepared the hydrogels by simple amidation and catechol-crosslinking reactions, which have larger swelling ratios of 220%–240%, suitable microporous size of about 6–8 µm, and tissue adhesion strength of about 20–40 kPa. The hemolysis, cytotoxicity, and cellular double-staining assays indicate that those hydrogels had good biocompatibility and the H-3 hydrogel with higher glucose content gave a lower hemolysis ratio of 0.73%±0.14%. The blood-clotting index, blood cell attachment and adhesion studies showed those hydrogels had fast blood-coagulation, resulting in excellent hemostasis performance with a short hemostatic time of 38–46 s and less blood loss of 19%–34% in a liver hemorrhage model. A full-thickness rat-skin defect model further demonstrates that the H-3 hydrogel achieved fast wound healing with a wound closure of 70.0%±2.7% on postoperative day 7 and nearly full closure on day 14. Remarkably, the hydroproline level that denotes the collagen production reached a higher one of 7.24±0.55 µg/mg comparable to that in normal skins on day 14, evidencing the wound healing was close to completion in the H-3 treatment. Consequently, this work provides a simple method to construct a glycosylated and catechol-functionalized hydrogel platform from commercial EPL, holding translational potentials in wound hemostats and dressings.