Chinese Journal of Polymer Science

Five secondary amine terminated poly(ester-amine)s (defined as PEA) with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate (PDDA) and 1,1,1-trimethylolpropane triacrylate (TMPTA) at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and ¹H-NMR spectra indicated that all acrylate groups were consumed in the reaction, based on which the structural parameters were calculated from the ¹H-NMR spectra. With decreasing PDDA/TMPTA ratio, the content of secondary amine, degree of branching, molecular weight, T_g and T_d increased accordingly. These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition. The gel content, relative hardness and T_g of the resulting films increased as PEA molecules changed from linear to highly branching structures. Due to the flexibility of PEA molecules, all the films possessed excellent mechanical performance.

Narrow disperse poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine) (poly(EGDMA-co-4-VPy)) microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate (EGDMA) and 4-vinylpyridine (4-VPy) with 2,2′-azobisisobutyronitrile (AIBN) as initiator in neat acetonitrile. The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm, which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles. The catalytic properties of the pyridyl-functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction.

The objectives of this paper are to understand the crystallization behavior of polypropylene (PP) composites with surface modified tetra-needle-shaped zinc oxide whisker (T-ZnOw). T-ZnOw was surface modified with different coupling agents, such as silane coupling agents (KH-550, KH-560) and titanate coupling agent (NDZ-105), in order to improve the compatibility between PP and T-ZnOw. DSC and POM were used to characterize the melt and crystallization behavior and the crystalline structures of the composites, respectively. The results show that the surface modified T-ZnOw acts as a nucleating agent of PP crystallization, depending on the coupling agent used for modification. KH-550 and KH-560 have more apparent role in improving the interfacial interaction than NDZ-105 and induce PP crystallization at higher temperature and with smaller spherulites size. The results also suggest that the crystallization behavior depends on not only the content of coupling agent, but also the content of the surface modified T-ZnOw used in the composites.

An exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA) nanocomposite was prepared by in situ solution polymerization of methyl methacrylate (MMA) in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs). MgAl-VBS LDHs was prepared by the ion exchange method, and the structure and composition of the MgAl-VBS LDHs were determined by X-ray diffraction (XRD), infrared spectroscopy and elemental analysis. XRD and transmission electron microscopy (TEM) were employed to examine the structure of LDHs/PMMA nanocomposite. It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix. The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.

Caged bicyclic phosphate (CBP) and its dimelamine salt (PDS) were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index (LOI) and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS, although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER < PDS30/ER < PDS15/ER < CBP15/ER, whereas that of specific extinction area is CBP15/ER > CBP30/ER > PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses (TG) and Fourier transform infrared spectroscopy (FT-IR), it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy (SEM), a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species. Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.

In this paper, melt blends of poly(propylene carbonate) (PPC) with poly(butylene succinate) (PBS) were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile testing, wide-angle X-ray diffraction (WAXD), polarized optical microscopy and thermogravimetric analysis (TGA). The results indicated that the glass transition temperature of PPC in the 90/10 PPC/PBS blend was decreased by about 11 K comparing with that of pure PPC. The presence of 10% PBS was partially miscible with PPC. The 90/10 PPC/PBS blend had better impact and tensile strength than those of the other PPC/PBS blends. The glass transition temperature of PPC in the 80/20, 70/30, and 60/40 PPC/PBS blends was improved by about 4.9 K, 4.2 K, and 13 K comparing with that of pure PPC, respectively; which indicated the immiscibility between PPC and PBS. The DSC results indicated that the crystallization of PBS became more difficult when the PPC content increased. The matrix of PPC hindered the crystallization process of PBS. While the content of PBS was above 20%, significant crystallization-induced phase separation was observed by polarized optical microscopy. It was found from the WAXD analysis that the crystal structure of PBS did not change, and the degree of crystallinity increased with increasing PBS content in the PPC/PBS blends.

in situ Fibril formation of polyamide-6 (PA6) in isotropic polypropylene (iPP) was first fabricated using a slit die extrusion and hot stretching process. Then the prepared materials were subjected to injection molding in the temperature range higher than the melting temperature of iPP but lower than that of PA6. The obtained injection-molded samples were characterized via scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and two-dimensional wide-angle X-ray scattering (2D-WAXS). Mechanical properties were also investigated. The SEM result shows that the optimum fibril formation could be only achieved in the range of 20 wt% to 30 wt% of PA6 content for the studied system. The fibril morphology changes along the sample thickness in the injection-molded bars. The fibril morphology in the skin layer was better than that in the core layer. 2D-WAXS results showed that the orientation of PP decreased with the increase of PA6 content, which indicated that the orientation of PP was confined by PA6 fibrils. Combined consideration of mechanical properties and morphology indicates that only PP/PA6 composites with 20 wt% of PA6 content show better properties because of the better fibril morphology and PP chain orientation.

Amphiphilic star-block copolymers composed of polystyrene and poly(acrylic acid) were synthesized by iodide-mediated radical polymerization. Firstly, free radical polymerization of styrene was carried out with AIBN as initiator and 1,1,1-trimethyolpropane tri(2-iodoisobutyrate) as chain transfer agent, giving iodine atom ended star-shaped polystyrene with three arm chains, R(polystyrene)₃. Secondly, tert-butyl acrylate was polymerization using polystyrene obtained as macro-chain transfer agent, and star-block copolymer, R(polystyrene-b-poly(tert-butyl acrylate))₃ with controlled molecular weight was obtained. Finally, amphiphilic star-block copolymer, R(polystyrene-b-poly(acrylic acid))₃ was obtained by hydrolysis of R(polystyrene-b-poly(tert-butyl acrylate))₃ under acidic condition.

A macroporous polymeric adsorbent NG-8 was synthesized with divinylbenzene using conventional suspension polymerization technique. Its aminated product NG-9 was prepared by introducing tertiary amino groups into NG-8 for removal of tannin acid from aqueous solutions. NG-9 could be used directly without a wetting process and had higher adsorption capacity than NG-8, which might be attributed to the enhanced adsorbent-adsorbate interaction due to the tertiary amino groups on the polymeric matrix. The Langmuir equation was successfully employed to describe the adsorption process. The adsorption enthalpy change further validated the uptake of tannin acid on NG-9 to be an enhanced physical adsorption because of the Lewis acid-base interaction. In addition, adsorption kinetic studies testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate maybe for the hindrance of the tertiary amino groups and water clusters built up.

In this paper two different kinds of dynamic mechanical techniques (inversed torsion pendulum and energy dissipation apparatus) were used to study the dynamic behavior of atactic monodisperse polystyrene above glass transition. The plots of energy dissipation versus temperature were presented for two atactic polystyrene samples. An apparent energy dissipation peak occurred above T_g in each plot measured by the inversed torsion pendulum, and simultaneously the sample was found to flow assuredly at the moment. To exclude the influence of the flow and demonstrate there was a peak indeed above T_g, the energy dissipation apparatus was used, in which the samples were put into a cup. An obvious peak appeared, and it was in agreement with the peak observed by the inversed torsion pendulum. On basis of the results measured by the two kinds of apparatus, a conclusion is drawn that a peak occurrs above T_g, which gives a manifestation for the existence of the liquid-liquid transition.

P(N-isopropylacrylamide) (PNIPAM) prepared by reversible addition fragmentation chain transfer (RAFT) polymerization exhibited gelation retardation. The intermediate before gelation was characterized and indicated the presence of branched or hyperbranched chains. The swelling behavior was investigated, and the gel by RAFT polymerization (RAFT gel) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional gels (CG). The study was extended to gels prepared by using 2-hydroxy-1-ethanethiol as chain transfer agent and by using low concentration solutions. The two systems also exhibited retardation effects and improved deswelling kinetics. The different swelling behaviors of these gels and CG could be attributed to the presence of dangling chains caused by gelation retardation.

New hyperbranched poly(aryleneethynylene)s containing carbazole moieties are synthesized in high yields (up to 87%) by polycyclotrimerization of 3,6-bis(4-ethynylphenyl)-9-octylcarbazole and its copolymerization with 1-octyne catalyzed by CpCo(CO)₂ in THF. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, photoluminescence, and cyclic voltammetry analyses. All the polymers are soluble in common organic solvents and show outstanding thermal stability (≥ 430°C). They graphitize in high yields (up to 79%) when pyrolyzed at 800°C. Upon photoexcitation, the polymers emit a strong deep blue light of ca. 400 nm with quantum yields larger than 60%.

A phosphrous-containing poly(aryl ether ketone) was synthesized derived from bisphenol-A and bis[4-(4-fluorobenzoyl)phenyl] phenyl phosphine oxide (FPPPO) by nucleophilic substitution reaction. The structure of the polymer was characterized by FT-IR, ¹H-NMR and ³¹P-NMR. The thermal property of the PAEK was measured by DSC and TGA. The glass transition temperature (T_g) of the polymer was 205°C, and the 5% weight loss temperature under nitrogen was 475°C. Good solubility of the polymer in organic solvents, such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and chloroalkanes was observed, flexible film was obtained from the polymer's CH₂Cl₂ solution. The limiting oxygen index (LOI) of the PAEK was 40, which indicated that organic phosphorus moiety can offer good flame retardant property to the polymer.