Cyclic polymers have attracted more and more attentions in recent years because of their unique topological structures and characteristic properties in both solution and bulk state. There are relatively few reports on cyclic polymers, partly because of the more demanding synthetic procedures. In recent years, "click" reaction, especially Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), has been widely utilized in the synthesis of cyclic polymer materials because of its high efficiency and low susceptibility to side reactions. In this review, we will focus on three aspects:(1) Constructions of monocyclic polymer using CuAAC "click" chemistry; (2) Formation of complex cyclic polymer topologies through CuAAC reactions; (3) Using CuAAC "click" reaction in the precise synthesis of molecularly defined macrocycles. We believe that the CuAAC click reaction is playing an important role in the design and synthesis of functional cyclic polymers.

A series of novel praseodymium (Pr)-bonded polymers were successfully synthesized via the coordination reaction and palladium-catalyzed Suzuki coupling reaction of 2,7-dibromo-9,9'-dioctylfluorene and different amounts of 5,5'-dibromo-2,2'-bipyridine. The resulting polymers were characterized by ¹H-NMR and GPC. The photoluminescence (PL) and electroluminescence (EL) properties of the resulting polymers were studied to explore the effects of the Pr triisopropyloxide. The results showed that the incorporation of Pr into the polymers caused better coplanarity and effective intermolecular or intramolecular interaction, leading to the higher emission intensity at long-wavelength. Further, it was also found that the emission light color could be tuned from blue to green by introduction of a small amount of Pr into the polymer main chain. A single-layer green emitting EL device based on PF(BipyPr)₆ with 6 mol% Pr content was fabricated. The device had a low turn-on voltage of 6 V, a brightness of 705.3 cd·m^-2, the maximum luminous efficiency of 1.53 cd·A^-1 and the maximum power efficiency of 0.69 lm·W^-1.

Bacterial cellulose/lotus root starch (BC/LRS) composites were prepared by cultivating Acetobacter xylinum in nutrient media containing gelatinized lotus root starch. Low concentrations of gelatinized LRS had increased BC production with the maximum value at 6.67 g/L when 5 g/L of LRS was added in the culture media and the composites had thicker and denser fibrils compared with those of BC with low concentrations of LRS (2.5 and 5 g/L). When the concentration of LRS was increased above 7.5 g/L, the morphology of the BC/LRS composites contained more fibril layers that were linked with LRS. The results from X-ray diffraction (XRD) demonstrated that there was no significant difference in structure between BC and BC/LRS composites except a slight increase in crystallinity for BC/LRS composites as the concentration of LRS was lifted up. The tensile tests were performed to display BC/LRS composites prepared with LRS concentration at 2.5 and 5 g/L in media had the tensile strength of 54 and 60 MPa, respectively, which indicated an improvement in mechanical property compared to the unmodified BC (45 MPa). Live/dead assay with chondrocytes seeded on BC/LRS composite revealed higher cell viability ranging from 85% to 90% than BC. Furthermore, cell morphology with typical spindle shape was observed on the surfaces of BC/LRS composite by confocal microscope. Through the overall results, it shows that this study has provided a guidance to prepare BC/LRS composites with better cell biocompatibility and higher mechanical strength than those of BC for the potential use in cartilage tissue engineering.

Detection of Cu(Ⅱ) is very important in disease diagnose, biological system detection and environmental monitoring. Previously, we found that the product TPE-CS prepared by attaching the chromophores of tetraphenylethylene (TPE) to the chitosan (CS) chains showed excellent fluorescent properties. In this study, we tried to use TPE-CS for detecting Cu(Ⅱ) because of the stable complexation of CS with heavy metals and the luminosity mechanism of the Restriction of Intramolecular Rotations (RIR) for aggregation-induced emission (AIE)-active materials. The fluorescence intensity changed when TPE-CS was contacted with different metal ions, to be specific, no change for Na⁺, slightly increase for Hg²⁺, Pb²⁺, Zn²⁺, Cd²⁺, Fe²⁺, Fe³⁺ due to the RIR caused by the complexation between CS and metal ions. However, for Cu²⁺, an obvious fluorescence decrease was observed because of the Photoinduced-Electron-Transfer (PET). Moreover, we found that the quenched FL intensity of TPE-CS was proportional to the concentration of Cu(Ⅱ) in the range of 5 μmol/L to 100 μmol/L, which provided a new way to quantitatively detect Cu(Ⅱ). Besides, TPE-CS has excellent water-solubility as well as absorbability (the percentage of removal, R=84%), which is an excellent detection probe and remover for Cu(Ⅱ).

A series of polyamic acid copolymers (co-PAAs) containing phosphorous groups in the side chains were synthesized from[2,5-bis(4-aminophenoxy) phenyl] diphenylphosphine oxide (DATPPO) and 4,4'-oxydianiline (ODA) with 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) through the polycondensation in N,N'-dimethyacetamide (DMAc). The co-PAA solutions were spun into fibers by a dry-jet wet spinning process followed by thermal imidization to obtain co-polyimide (co-PI) fibers. FTIR spectra and elemental analysis confirmed the chemical structure of PI fibers. SEM results indicated that the resulting PI fibers had a smooth and dense surface, a uniform and circle-shape diameter. The thermogravimetric measurements showed that with the increase of DATPPO content, the resulting PI fibers possessed high decomposition temperature and residual char yield, indicating that the PI fibers had good thermal stability. The corresponding limiting oxygen index (LOI) values from the experiment results showed that the co-PI fibers possessed good flame-retardant property. Furthermore, the mechanical properties of the co-PI fibers were investigated systematically. When the DATPPO content increased, the tensile strength and initial modulus of the co-PI fibers decreased. However, the mechanical properties were improved by increasing the draw ratio of the fibers. When the draw ratio was up to 2.5, the tensile strength and initial modulus of the co-PI fibers reached up to 0.64 and 10.02 GPa, respectively. The WAXD results showed that the order degree of amorphous matter increased with increased stretching. In addition, the SAXS results displayed that valuably drawing the fibers could eliminate the voids inside and lead to better mechanical property. WAXD revealed that the orientation of the amorphous polymer influenced the mechanical properties of the fibers.

Plasticized poly(L-lactide) (PLLA) materials have been applied in many fields and the microstructure performance of such materials attracts much attention of researchers. However, few reports declared the hydrolytic degradation ability of the plasticized PLLA materials. In this article, a small quantity of poly(ethylene glycol) (PEG) was introduced into PLLA, which aimed to understand the hydrolytic degradation behavior of the plasticized PLLA materials. The microstructures of the plasticized samples were comparatively investigated using scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and Flourier transform infrared spectroscopy (FTIR), etc. The results demonstrated that PEG improved the hydrophilicity of sample surface, and the relatively high content of PEG enhanced the crystallization ability of PLLA matrix. The hydrolytic degradation measurement was carried out at 60℃ in an alkaline solution of pH=12. The results demonstrated that the plasticized PLLA samples exhibited accelerated hydrolytic degradation compared with the pure PLLA sample, and the hydrolytic degradation was also dependent on the PEG content. Further results demonstrated that PEG induced the change of hydrolytic degradation mechanism possibly due to the good dissolution ability of PEG in water, which provided more paths for the penetration of water. Furthermore, the microstructure evolution of the plasticized PLLA during the hydrolytic degradation process was also investigated, and the results demonstrated the occurrence of PLLA crystallization, which was possibly contributed to the decreased hydrolytic degradation rate observed at relatively long hydrolytic degradation time. This work is of great significance and may open a new way for promoting the reclamation of PLLA waste material.

The fluorescently labelled polymers including pyrene-labelled polystyrene (PyPS) and pyrene-labelled poly(methyl methacrylate) (PyPMMA) with narrow molecular weight distributions were synthesized by the atom transfer radical copolymerization (ATRCP) of styrene or methyl methacrylate with 1-pyrenemethyl methacrylate (PyMMA). The ultrathin PyPS and PyPMMA films with the thickness ranging from 30 nm to 400 nm supported on the quartz slides were prepared by spin-coating. The fluorescent quantum yield (QY) of the pyrene probe in the ultrathin polymer films was investigated by the photoluminescence spectrometer using an integrating sphere detector. The QY decreased with the reduction of film thickness in the sub-200 nm range.

Plasticized polymer electrolytes were prepared using poly(ethylene oxide) (PEO)/poly(vinylidene fluoridehexafluoro propylene) (PVdF-HFP) with lithium perchlorate (LiClO₄) and different plasticizers. XRD and FTIR spectroscopic techniques were used to characterize the structure and the complexation of plasticizer with the host polymer matrix. The role of interaction between polymer hosts and plasticizer on conductivity is discussed using the results of alternating current (a.c.) impedance studies. TG-DTA and SEM were used for thermal and physical characterizations. Maximum ionic conductivity (3.26×10^-4 S·cm^-1) has been observed for ethylene carbonate (EC)-based polymer electrolytes. Electrochemical performance of the plasticized polymer electrolyte is evaluated in LiFePO₄/plasticized polymer electrolytes (PPEs)/Li coin cell. Good performance with low capacity fading on charge discharge cycling is demonstrated.

In this study, we demonstrate a novel method for fabricating polythiophene patterns, i.e., cylindrical holes and cylinders, through blending of a thermally curable polythiophene carrying with tertiary ester groups (PT-tert-ESTER) and poly(methyl methacrylate) (PMMA), followed by thermal conversion of the PT-tert-ESTER to an insoluble polythiophene via low-temperature cleavage of the tertiary ester groups and removal of the PMMA component via ultraviolet degradation. We show that the surface polarity of substrates, the mass ratio of PT-tert-ESTER to PMMA in the blend solutions as well as the concentration of the blend solutions strongly influence the formation of the polythiophene patterns. Cylindrical holes are more readily formed on less polar substrates when a PT-tert-ESTER dominated blend solution is used, while cylinders are more readily formed on more polar substrates when a PMMA dominated blend solution is used. Moreover, the diameters of both the cylindrical holes and the cylinders decrease as the PT-tert-ESTER concentration is increased in the respective ranges of the PT-tert-ESTER/PMMA ratios where the patterns are formed. Grazing incident X-ray diffraction data have indicated that the patterning of the PT-tert-ESTER component in the blend films improves the crystallinity of PT-tert-ESTER as well as the molecular packing of the insoluble polythiophene in the resultant patterned polythiophene films.

The morphology of polyamide 6/poly(butylene terephthalate) (PA6/PBT, 70/30, W/W) blends filled with pristine Zinc oxide (ZnO) nanoparticles and ZnO surface-modified by γ-glycidoxypropyltrimethoxysilane (K-ZnO) was investigated. The incorporation of ZnO and K-ZnO by one-step compounding both resulted in a smaller size and narrower distribution of PBT domains and the effect of ZnO was greater than K-ZnO. To reveal the underlying mechanism, two-step compounding in which ZnO or K-ZnO was premixed with PA6 or PBT was conducted and the finest morphology was achieved when mixing PA6 with premixed PBT/ZnO. Transmission electron microscopy (TEM) demonstrated that ZnO was distributed in PBT in all cases and K-ZnO was enriched at the interface except when K-ZnO was premixed with PBT. ZnO and K-ZnO caused a deterioration in the melt rheological properties of PBT, which played a dominating role in the morphological changes. In addition, the interfacial localization of K-ZnO enhanced the dynamic rheological properties of PA6/PBT blends substantially.

A critical challenge for initiating many applications of the carbon nanotubes (CNTs) is their dispersion in organic solvent or in polymer melt. In the present study, we described a novel strategy for fabricating carbon nanotubes (CNTs)-reinforced epoxy nanocomposite by utilizing aniline trimer (AT) as the noncovalent dispersant. Tensile testing showed that the tensile modulus of the CNTs-reinforced epoxy composites was considerably improved by adding a small amount of AT functionalized CNTs. Additionally, the as-prepared CNTs-epoxy nanocomposites exhibited superior tribological properties with much lower frictional coefficients and wear rates compared to those of neat epoxy resin. The well dispersed AT-functionalized CNTs in epoxy matrix played an important role in enhancing the mechanical properties, as well as acting as a solid lubricant for improving the tribological performance of epoxy/CNTs nanocomposite.