Shi-Lin Yang

Separation and identification of ethylene-propylene block copolymer

Abstract In this paper, a commercial impact-resistant polypropylene alloy sample was fractionated with preparative temperature rising elution fractionation (t.r.e.f.) technique and a series of ethylene-propylene block copolymer fractions with different ethylene contents were obtained. Combined with fractionation results, the block structure of them was identified with 13 C nuclear magnetic resonance (n.m.r.) spectroscopy and differential scanning calorimetry (d.s.c.). There are some transition segments between polyethylene and polypropylene segment in the block copolymer. It was found that the number and kind of transition segments decreased with elution temperature, the length and melting temperature of polyethylene segment in block copolymer fractions showed a similar tendency.

Distribution of active centers on TiCl4/MgCl2 catalyst for olefin polymerization

1-Octene was polymerized with TiCl 4 /MgCl 2 -AlEt 3 and the polymerization was quenched with CH 3 COCl to introduce a CH 3 CO - group onto each propagation chain. The polymer was fractionated by fractional precipitation, and the number of active centers in each fraction was determined by measuring the CH 3 CO- content of the fraction. Distributions of the number and reactivity of active centers among the fractions were determined and discussed based on these experiments. The active center distributions were also studied by fitting the molecular-weight distribution (MWD) curve from GPC with multiple Schulz-Flory most-probable distributions. The uncontinuous reactivity distribution of active centers reveals that there exist limited types of active centers on the catalyst. Five types of active center were distinguished by the MWD fitting treatment. The correlations between the active center distributions and catalyst structures are discussed.

Microtacticity of polypropylene fractions produced by different active sites of heterogeneous Ziegler–Natta catalyst

Polypropylene (PP) prepared with the MgCl 2 /TiCl 4 -AlEt 3 /Ph 2 Si(OMe) 2 catalyst system was fractionated by a preparative temperature rising elution fractionation (TREF) technique in the wide temperature range of room temperature to 130°C. The results of fractionation showed that there were plural active sites in this heterogeneous catalyst. Some key fractions were selected for characterization of 1 H- and 13 C-NMR. 1 H-NMR results suggested that the fractionation takes place according to tacticity. Based on analysis of 13 C-NMR, it was concluded that the polymerization mechanism proceeding on highly stereospecific active sites was active site-controlled and nonstereospecific active sites were able to convert into syndiotactic active sites during the polymerization, which led to the formation of a syndiotactic block.

Orientation, characterization, and photoconductive property of ethylenediamine bridged silicon phthalocyanine polymer thin film

Abstract The oriented thin film containing ethylenediamine bridged silicon phthalocyanine polymer [PcSi(eda)]n dispersed in polyvinyl difluoride (PVDF) was fabricated by the electric field orientation. The characterization of the [PcSi(eda)]n–PVDF oriented thin film by polarized fluorescence, DSC, FTIR reflection absorption spectroscopy (FTIR-RAS), and angle-dependent XPS revealed that the planes of phthalocyanine rings were oriented parallel to the film surface in a perpendicular electric field, while largely 30° with respect to the film surface in a parallel electric field. Combining the ESR analysis, an ‘electron channel’ by π–π orbits in phthalocyanine rings overlapping each other may be formed. The photoconductivity studies by photoinduced xerographic discharge technique showed that the photosensitivities of the [PcSi(eda)]n–PVDF oriented thin films were clearly higher than those of [PcSi(eda)]n–PVDF thin films coated without an electric field, and varied with the direction of the applied electric field. It was thought that the orientation and the stacking alignment of the [PcSi(eda)]n molecules in the films might be responsible for the increase of the photoconductivity.

Thermodynamic analysis for the interaction of polyacrylate with wax in heptane

Abstract The effect of polyacrylate (PA) on wax-precipitation temperature in heptane was investigated using differential scanning calorimetry (DSC). A thermodynamic analysis for the dissolution of wax in the absence and presence of PA was conducted. Results suggested that the change in wax-precipitation temperature caused by the introduction of the additives may be regarded as an index for characterizing the interaction of polymer additives with wax.

Synthesis and photoconductivity study of phthalocyanine polymers. IV. [SiPcNHCH2CH2NH]n

The preparation of a novel polymer of ethylenediamine bridged polymeric silicon phthalocyanine (I) with quasi-one-dimensional structure is described. The product was obtained by the condensation polymerization of ethylenediamine and silicon dichloride phthalocyanine (Cl2SiPc) monomers and was characterized by IR and UV/VIS spectroscopy and elemental analysis. The photoconductivity of the polymer I with the quasi-one-dimensional structure is much better than that of not only the corresponding Cl2SiPc monomer, but also other phthalocyanine polymers whose molecules are not one-dimensional structures, and showing the one-dimensional effects of molecular structure of increasing photoconductivity.

Synthesis and photoconductivity study of VK-AA copolymer containing CuPc

Abstract A novel kind of copolymer consisting of poly(vinylcarbazole-co-acrylamide)-bonded CuPc(NO 2 ) 2 was synthesized by the reaction of the diazonium salt of dinitro-diamino copper phthalocyanine with vinylcarbazole and acrylamide. The polymer showed good photoconductivity, much better than that of the corresponding phthalocyanine monomer CuPc(NO 2 ) 4 . The main factors influencing the photoconductivity were also studied.

Photoconductivity study of doping in PVK-bonded phthalocyanine

Abstract The influence of the dopant iodine (I 2 ) on photoconductivity of polyvinylcarbazole-bonded CuPc(COOH) 3 ( I ) (Pc, phthalocyanine) was examined. The results indicate that polymer I shows increasing photoconductivity after doping with I 2 . UV-visible and fluorescence analyses indicate that a charge-transfer complex (CTC) of polymer I with I 2 may be formed.

The roles of Grignard reagent in the Ziegler–Natta catalyst for propylene polymerization

Grignard reagent PhMgCl was added during the preparation of the catalyst system MgCl2/di-n-butyl phthalate (DNBP)/TiCl4—AlEt3/diphenyl dimethoxyl silane (DPDMS) to improve its performance. It was found that PhMgCl could enhance both the activity of the catalyst and the isotacticity of the products, but decreased the Ti content of the catalysts under the same preparation conditions. The polymerization kinetics showed that PhMgCl accelerates the decay in the same time that it increased the initial and final polymerization rates. By means of UV-vis spectroscopy, electron spin resonance (ESR) spectroscopy, and the Ti content determination of the catalysts, the multiple roles of PhMgCl were disclosed: reduction of Ti4+ to Ti3+, association with MgCl2 to replace part of TiCl4 in aspecific active sites, and complexing with the original active sites to form new active sites.

Photoconductivity of phthalocyanine composites II: Double-layered photoreceptor of FeIIPcPVK

Abstract The photoconductivities of double-layered photoreceptors, containing ferrous phthalocyanine (Fe II Pc) and other phthalocyanines as charge generator and polyvinylcarbazole as charge transporter, were studied. The results show an increased photoconductivity of Fe II PcAlClPc, Fe II PcNdPc and Fe II PcMnPc compared with the pure phthalocyanines, but a decreased photoconductivity of Fe II PcInClPc. In these composites, polymorphic transformation of Fe II Pc occurs and its molecular interaction changes.