Journal of Polymer Science最新文献

Segregated conductive polymer composites (CPCs) show high conductivity at low loading of filler. However, the weak interactions between fillers and polymer matrix may destroy the mechanical property of the segregated CPCs. Moreover, even with the introduction of dynamic bonds in thermoset polymers, the preparation of thermosetting CPCs remains a big challenge, as most crosslinked polymers should be ground into granules or crushed into powder with liquid nitrogen before mixing with fillers. Herein, the dynamic crosslinked polythiourethane microspheres (PTUM) are designed and synthesized. Then, a special mixing method (the mixing temperature is higher than melting temperature of soft segments of PTUM) is used to make the carbon nanotubes (CNTs) adhering closely to the surface of the crosslinked PTUM, promoting the formation of compacted conductive network. The CNT-3%/PTUM shows the electrical conductivity of 21.9 S/m and an elongation at break of 472%. Additionally, the CNT/PTUM composites exhibit good self-healing property, reprocessability, and close-loop recycling property. The construction of dynamic crosslinked microspheres and compacted segregated conductive network in this work supplies a new approach to prepare thermoset CPCs with simultaneous high electrical conductivity and mechanical property, which is expected to be applied to wearable strain sensors.

The anionic polyaddition of methyl-substituted 1,1-diphenylethylene derivatives, catalyzed by lithium diisopropylamide, was examined. Polymerization of the monomer was conducted at 50°C in THF with the addition of diisopropylamine. NMR and MALDI-TOF-MS analyses of the obtained polymer indicate that polymerization proceeded via a polyaddition reaction, in other words, repetition of the lithium amide-induced metalation reaction of the monomer at the methyl group and the subsequent nucleophilic addition reaction of the corresponding benzyllithium with the vinyl group in the monomer. On the other hand, the unsubstituted diphenylethylene monomer could not be polymerized by the same reaction condition. Consequently, the resulting polymer was indeed obtained by an anionic polyaddition mechanism. In conclusion, a novel hydrocarbon polymer containing a phenyl group in the main chain of the repeating unit was successfully obtained from a methyl-substituted 1,1-diphenylethylene monomer.

Cellulose nanocrystals (CNCs) have received an abundance of attention because of their distinctive chiral nematic structure and exceptional optical characteristics. However, the use of free-standing films is constrained by the inherent stiffness and brittleness. In this work, CNC films with robust mechanical properties are prepared by simply coating them with polymeric spherulites. Maleic anhydride-grafted polypropylene (PP-g-MA) is used to coat CNC films. The optical properties of coated films were also analyzed using polarized optical microscope. It is observed that the circular extinction patterns for the coated CNC film were created by the radial symmetry of banded spherulites, which were responsible for the perception of the optical transmission bands of the CNC film. Interfacial anchoring plays a crucial role in enhancing the overall performance and properties of the composite system. The future development of numerous portable functional components needing improved optical, mechanical, and thermal qualities of CNC films is made possible by this protective coating approach.

Polyolefin elastomer (POE) has very weak crystalline ability, consequently, applying the conventional preparative temperature-rising elution fractionation (P-TREF) to separate is challenging. Here, a unique, home-built P-TREF apparatus with an extensive range of temperatures from −80°C to 150°C is applied to first fractionate POE depending on its crystallizability. The main fractions are eluted at 0°C, 8°C, 15°C, 20°C, 25°C, 30°C, and 35°C. The corresponding weight percentages of fractions are 8.31, 13.38, 15.59, 12.05, 13.39, 17.30, and 10.53 wt%, respectively. The chain structures of fractions are further analyzed by high-temperature gel permeation chromatography (HT-GPC), ¹³C-nuclear magnetic resonance spectroscopy (¹³C-NMR), differential scanning calorimetry (DSC), and successive self-nucleation and annealing (SSA). The crystallinity of the fraction grows continually as the elution temperature rises. The 1-octene comonomer concentrations within the fractions decreases from 13.8 to 7.9 mol% when the elution temperature rises from −10°C to 40°C. These findings enable for the detailed recognition of the chain microstructure of POE resin and the extension of the TREF approach to POE resins. This lays the groundwork for fundamental studies and practical uses in industry.