Chinese Journal of Polymer Science

An ordered ladder polyester (LPE) was first synthesized through the ladder superstructure (LS) constructed by concerted interactions of hydroxyl- and aramide-based H-bonding and p-terphenyl (TP)-based π-stacking by dehydrochlorination condensation using phosgene (COCl₂) as coupling agent. LPE was characterized by GPC, FTIR, NMR, XRD, DSC and AFM. Among them, a distinct image of regularly linear alignment corresponding to the ladder main chain of LPE was first revealed by high-resolution AFM.

Thin film morphology of a symmetric semicrystalline oxyethylene/oxybutylene diblock copolymer (E₇₆B₃₈) on silicon was investigated by tapping mode atomic force microscopy (AFM). It is found that the nascent thin film is composed of multiple polymer layers having mixed thicknesses of L ≈ L₀ and L ≈ L₀/2 (L₀ is the long period of the block copolymer in bulk) besides the first layer near the substrate. This shows that the crystalline domain in the block copolymer consists of double poly(oxyethylene) layers. Annealing leads to disappearance of the polymer layers with thickness L ≈ L₀/2, indicating that such polymer layers are metastable.

The effect of N,N,N′,N′-tetraalkyl terephthalamide (TATA) on the non-isothermal crystallization and melting characteristics of polypropylene (PP) was studied. The addition of TATA can lead to the formation of β-crystal PP. With the increase in TATA concentration the degree of crystallinity for β-crystal PP increased significantly, and that for α-crystal PP decreased, which indicated that TATA effectively induced the formation of β-crystal PP. WAXD also revealed the existence of β-crystal PP after the introduction of TATA into PP. PP containing TATA crystallized at a temperature range of 5–10°C higher than that of pure PP, and the half-crystallization time (t_1/2) and Avrami exponent (n) of PP at the same cooling rate were decreased by the addition of TATA, indicating that TATA influenced the crystallization rate and crystallization growth mode of PP. The rate constant of crystallization of PP containing TATA (Z_c) was larger than that of pure PP, which further indicated that the crystallization of PP was accelerated by the addition of TATA.

Novel shish-kebab type liquid crystalline poly(p-phenylenevinylene) derivatives were synthesized by Stille coupling reaction from 2,5-bis[(4-n-alkoxyl)benzoyloxy]1,4-dibromobenzene (monomer 1) and 1,2-bis(tributylstannyl) ethylene (monomer 2). The polymers with alkoxy groups are soluble in common organic solvents and exhibit blue fluorescence. Both the cast film and the annealed film have large red-shifts in fluorescence spectra and show yellow fluorescence. The polymers with CN and NO₂ groups show poor solubility and green fluorescence. All the polymers possess liquid crystalline smectic phases. The melting point (T_m) of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The polymers are easily aligned under a magnetic field of 10 Tesla. It is found that the conjugated backbone and LC side chain are aligned perpendicular and parallel to the magnetic field, respectively. The polymers show optical dichroism in fluorescence spectra, suggesting that they are available for advance materials with linear optical polarization.

A series of thermochromic polypropylene foils were prepared by embedding various leuco dye-developer-solvent systems in the polymer matrix. Bisphenol A, laurylgallate, ethylgallate and p-hydroxybenzoic acid methyl ester were used as developers, crystal violet lactone and 3,3-bis-(1-n-butyl-2-methyl-3-indolyl)-phthalide as dyes and 1-octanoic acid methyl ester as solvent. The molar ratio between the three components of the investigated leuco dye-developer-solvent systems was kept constant. All obtained polypropylene foils exhibit an excellent thermochromic behavior. The foils, prepared by extrusion technology, switch from color to colorless with increasing temperature. The influence of molecular structure of the developer on the intensity of the colored state and the influence of a developer-surfactant complex on the resulting thermochromic properties were investigated. The results are presented and discussed in detail according to a molecular model suggesting that the ring-opening process of the leuco dye is triggered by the formation of dye-developer complexes via H-bondings.

The intrinsic viscosity [η], Huggins constant (K_H), [η]₀, α³ and flow activation energy values of nylon 6 have been measured in water/m-cresol (0/100–20/80) systems at different temperatures (20–60°C). It has been found that the intrinsic viscosity, [η]₀ and α³ increase with the increase in water contents in m-cresol up to 15% and then decrease. They increase with the increase in temperature irrespective of solvent composition. It has been noted that the percent increase of α³ is the highest at 60°C and the lowest at 20°C for a particular solvent system. The intrinsic viscosity data obey Arrhenius equation over the considered conditions. The activation energy and the K_H values decrease very sharply with the addition of water, giving a minimum value at 15% of water and then increase slowly. The variation of all the parameters has been explained in terms of variation in thermodynamic quality of solvent with the addition of water to m-cresol and change in temperature, resulting in the change of conformational and orientational properties of polymer molecules. This change of solvent quality also results in variation of selective sorption of solvent over the polymer, such as hydrogen bonding, etc.

The effect of compatibility on phase morphology and orientation of isotactic polypropylene (iPP) blends under shear stress was investigated via dynamic packing injection molding (DPIM). The compatibility of iPP blended with other polymers, namely, atactic polypropylene (aPP), octane-ethylene copolymer (POE), ethylene-propylene-diene rubber (EPDM) and poly(ethylene-co-vinyl acetate) (EVA), have first been studied using dynamic mechanical analysis (DMA). These blends were subjected to DPIM, which relies on the application of shear stress fields to the melt/solid interfaces during the packing stage by means of hydraulically actuated pistons. The phase morphology, orientation and mechanical properties of the injection-molded samples were characterized by SEM, 2D WAXS and Instron. For incompatible iPP/EVA blends, a much elongated and deformed EVA particles and a higher degree of iPP chain orientation were observed under the effect of shear. However, for compatible iPP/aPP blends, a less deformed and elongated aPP particles and less oriented iPP chains were deduced. It can be concluded that the compatibility between the components decreases the deformation and orientation in the polymer blends. This is most likely due to the hindering effect, resulting from the molecular entanglement and interaction in the compatible system.

The brittle-ductile transition is a very important phenomenon for polymer toughening. Polypropylene (PP) is often toughened by using rubbers, e.g., ethylene-propylene diene monomer (EPDM) has often been used as a modifier. In this article, the toughening of PP by using a new kind of rubber, known as elastomeric nano-particle (ENP), and the brittle-ductile transition of PP/EPDM/ENP was studied. Compared to PP/EPDM binary blends, the brittle-ductile transition of PP/EPDM/ENP ternary blends occurred at lower EPDM contents. SEM experiment was carried out to investigate the etched and impact-fractured surfaces. ENP alone had no effect on the impact strength of PP, however, with the same EPDM content, PP/EPDM/ENP ternary blends had smaller particle size, better dispersion and smaller interparticle distance in contrary to PP/EPDM binary blends, which promoted the brittle-ductile transition to occur earlier.

The new chelate resins, abbreviated as PNBMZs and PBBMZs based on epoxide polymer, were synthesized by polycondensation of N,N-diglycidyl-4-glycidyloxyaniline or 1,4-bis(2,3-epoxypropyl)benzene with the primary amine group of 1,3-bis(benzimidazol-2yl)propylamine (BBPAH). The ion exchangers contain 2.71–3.23 mmol of the ligand contents per gram of the resin. Batch extraction capacities were determined for the metal chloride salts in buffer solutions in the pH range from -1 to 6.0. The chelate resins were very selective for Cu²⁺, Zn²⁺, Cd²⁺ in the presence of other divalent transition metal ions. The maximum uptake capacities of PNBMZ (synthetic molar ratio = 1:1.5) under non-competitive condition were found to be 0.94 mmol/g for Cu²⁺ at pH = 2, 1.3 mmol/g for Cd²⁺ at pH = 1 and 1.75 mmol/g for Zn²⁺ at pH = -1 respectively. While in the case of PBBMZ, it was 1.39 mmol/g for Cd²⁺ at pH = 1. The metal-uptake behaviors for both of them showed strong pH dependence, and their extraction capacities increase with decreasing pH. The uptake of Cu²⁺ by the resin PNBMZs at pH = 1 was found to be rather fast with t_1/2 = 18 min. Metal-uptake experiments under competitive conditions also confirm that the chelate resins have a high selectivity for Cu²⁺Zn²⁺, Cd²⁺ and the contrary pH dependence.

The orientation and crystallinity evolution of isotactic polypropylene (iPP) induced by rolling were studied using wide angle X-ray scattering with an area detector. The tensile mechanical properties of rolled isotactic polypropylene sheets were also measured in this work. The texture component method was used to analyze the rolling texture. The rolling texture consists mainly of (010)[001], (130)[001] and [001]//RD fiber components in the sample with a rolling true strain of 1.5. The results reveal that crystallinity drastically decreases during rolling. It is suggested that amorphization is a deformation mechanism which takes place as an alternative to crystallographic intralamellar slip depending on the orientation of the lamellae. Both the orientation and crystallinity affect the tensile mechanical properties of rolled polypropylene. Crystallinity influences the elastic modulus on both directions and yield strength on transverse direction at the first stage of deformation. Orientation is the main reason for the changes of mechanical properties, especially at the latter part of deformation. The changes of both tensile strength and elongation percentage on rolling direction are larger than those on transverse direction, which results from the orientation. At last, the anisotropic mechanical properties occur on the rolling and transverse direction: high tensile strength with low elongation percentage on rolling direction and low tensile strength with high elongation percentage on transverse direction.

A novel hyperbranched poly(phenylene oxide) (HPPO) with phenolic terminal groups was prepared from 4-bromo-4′,4"-dihydroxytriphenylmethane as AB2 monomer in dimethylsulfoxide (DMSO) via a modified Ullmann reaction. The molecular weight and polydispersity (PD) of the resulting polymers increased with increasing reaction time. In the presence of core molecules (bisphenol A and 1,3,5-trihydroxybenzene), which have the similar molecular backbones to the reactive monomer, the molecular weight could be controlled by varying the core-to-monomer ratio. Incorporation of a very small amount of core molecules could lead to a higher molecular weight as compared with that without the addition of core molecules. However, when the core content reached certain extent, the molecular weight would decrease with the further increase in the core content. A new similar behavior of control over the PD was also obtained. The resulting polymers were characterized by ¹H-NMR, ¹³C-NMR, FT-IR, and GPC.

Surface modification by physical adsorption of a series of non-ionic surfactants including Tween 20, Tween 40, Tween 60, Tween 80 and Tween 85, was accomplished on polypropylene microporous hollow fiber and flat membranes. The adsorption curve of the membrane surface was analyzed by weight measurements and the typical results showed a two-platform character similarly. Differences in the degree and curve shape of adsorption resulting from such factors as concentration, temperature, as well as water cleaning time were observed for Tween 85 among other Tweens. Attenuated total reflection — Fourier transform infrared spectroscopy analysis and field emission scanning electron microscopy observation showed that the adsorption of Tween on polypropylene microporous membrane (PPMM) is effective and occurs mainly in the pores of PPMMs at low adsorption amount, and on the membrane surface also at high adsorption value.

A surfactant-assisted method for preparing colloidal spheres with narrow size distribution from a polydispersed azo polymer has been developed in this work. The colloidal spheres were formed through gradual hydrophobic aggregation of the polymeric chains in THF-H₂O dispersion media, which was induced by a steady increase in the water content. Results showed that the addition of a small amount of surfactant (SDBS) could significantly narrow the size distribution of the colloidal spheres. The size distribution of the colloidal spheres was determined by the concentrations of azo polymer and the amount of surfactant in the systems. When the concentrations of polymer and surfactant amount were in a proper range, colloidal spheres with narrow size distribution could be obtained. The colloidal spheres formed by this method could be elongated along the polarization direction of the laser beams upon Ar⁺ laser irradiation. The colloidal spheres are considered to be a new type of the colloid-based functional materials.

The reduced viscosity of polymer guar gum solutions containing a certain concentration of sodium dodecyl benzene sulfonate (SDBS) was measured. It has been found that the Huggins coefficient k_H of polymer solutions is very sensitive to the concentration of the surfactant, c_SDBS, in solutions. If c_SDBS is lower than CMC, the critical micelle concentration of SDBS, k_H increases rapidly with c_SDBS. On the other hand, if c_SDBS is larger than CMC, k_H decreases rapidly with c_SDBS. Comparatively, the intrinsic viscosity of polymer solution does not show a notable change with c_SDBS. The experimental results indicate that the interchain association of polymer guar gum in solution is greatly associated with SDBS interacted with polymer chains through hydrogen bonds. However, the effect of SDBS upon the intrachain association of polymer guar gum solution is negligible, presumably due to the fact that guar gum is a slightly stiffened random-coil chain polymer.