Preparation and Characterization of Polymeric Microspheres Having Isotactic Poly(methacrylic acid) on Their Surfaces

A poly（ tert -butyl methacrylate）（PBMA） macromonomer was synthesized by anionic polymerization with bis（2,6-di- t -butyl phenoxy） methyl aluminum [MeAl（ODBP）2] as the initiator and trimethylsilylmethacrylate（TMSMA） as the end capping agent in dry THF. Then, a poly（methacrylic acid）（PMAA） macromonomer was obtained by means of hydrolysis reaction from the PBMA macromonomer in the presence of hydrochloric acid. The structures of the PBMA macromonomer were characterized by using 1H NMR. It was found that the resulted PBMA macromonomer has highly isotactic properties and the PMAA macromonomer has an end vinyl group on per polymer chain. The monodisperse polymeric microspheres, which consisted of polystyrene cores and PMAA branches on their surfaces, were prepared by the dispersion copolymerization of styrene with the PMAA macromonomer in an ethanol/water mixed solvent. It was found that the concentration of the PMAA macromonomer would affect the microsphere formation, the morphology and its size in the copolymerization system.

Effect of Diluent on the Morphology and Performance of IPP Hollow Fiber Microporous Membrane via Thermally Induced Phase Separation

Isotactic polypropylene （iPP） hollow fiber microporous membranes were prepared using thermally induced phase separation （TIPS） method. Di-n-butyl phthalate （DBP）, dioctyl phthalate （DOP）, and the mixed solvent were used as diluents. The effect of α （DOP mass fraction in diluent） on the morphology and performance of the hollow fiber was investigated. With increasing α, the morphology of the resulting hollow fiber changes from typical cellular structure to mixed structure, and then to typical particulate structure. As a result, the permeability of the hollow fiber increases sharply, and the mechanical properties of the hollow fiber decrease obviously. It is suggested that the morphology and performances of iPP hollow fiber microporous membrane can be controlled via adjusting the compatibility between iPP and diluent.

High Efficieney Synthesis of Isotaetie Polypropylene and Linear Polyethylene Using a New C_2-symmetric Carbon-bridged Zirconocene Catalyst

Ansa-Cyclohexyl-bis（4,5,6,7-tertrahydro-l-indenyl） zirconium dichloride （5） was used as catalyst for propylene and ethylene polymerization together with methyl aluminoxane （MAO） as the cocatalyst. Isotactic polypropylene （PP） was obtained with the highest activity of 6.37× 107g PP （molZr）^-1h^-1. The mesomeso （mmmmm） pentads sequence content of PP was determined by 13C NMR spectroscopy. The dependence of the microstructure on the reaction temperature and the AI/Zr molar ratio was examined and the catalytic activity of complex 5 was compared with that of the similar ansa-zirconocene 3. The high activity of the new zirconocene 5 for propylene isospectic polymerization at high temperature （60℃） is the result of its unique bridged-group structure. Complex 5/MAO displays also high catalytic activity of 0.46× 10^6 to 9.87× 10^6g PE（molZr）^-h^-in the homo-polymerization of ethylene, The visometric molecular weight of PE ranges from 0.97×10^4 to 11.16×10^4 g.mol^- under the given conditions.^13C NMR spectroscopy analysis proves the PE to be linear polyethylene （LPE）.

PARTIAL MELTING AND RECRYSTALLIZATION OF ISOTACTIC POLYPROPYLENE

A relatively high predetermined crystallization temperature （135℃） was chosen to grow well developed iPP spherulites, then the partial melting was carried out at a temperature of 165℃, where the preformed spherulites were seen to only decrease their size but not completely melted. The crystallization behavior of partially melted isotactic polypropylene （iPP） has been carefully examined by different scanning calorimetry （DSC） and polarized light microscopy （PLM）. The experimental results show that at a special annealing temperature （165℃） the melting behavior of iPP includes two parts with different mechanism, one part is the melting of iPP spherulite outside, another is the partial lamellae perfection during longer annealing time in the unmelted spherulite. The conformational orders of the iPP melt decrease with the increase of the annealing temperature.

TEXTURE AND CRYSTALLINITY EVOLUTION IN ISOTACTIC POLYPROPYLENE INDUCED BY ROLLING AND THEIR INFLUENCE ON MECHANICAL PROPERTIES

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.

AN ATOMIC FORCE MICROSCOPY STUDY ON THE AGGREGATION OF ISOTACTIC POLY(METHYL METHACRYLATE)

Aggregation process of isotactic poly（methyl methacrylate） （i-PMMA） has been studied extensively for many years, and considerable progress has been made in both experimental and theoretical studies. They are, however, seldom sustained by real-space observations of the underlying morphology. In this paper, the aggregation process of i-PMMA in concentrated acetone solutions and the fractal structure of the resulting three-dimensional clusters were characterized on the basis of real-space AFM observations of their two-dimensional projection. It was found that spherical multiple-chain particles formed upon collapse and aggregation of the involving chains as a whole during quenching the solution to room temperature. By keeping the solution at room temperature, the initially formed particles stick together upon contact to form larger particles through reassembling very slowly. The succeeding collision of the enlarged spherical particles leads to the formation of small clusters. These newly formed small clusters grow when they meet with other clusters or single Brownian particles. This leads to the formation of large clusters with fractal dimension of 1.95 ± 0.05, which suggest a reaction-limited cluster aggregation of i-PMMA in a concentrated acetone solution. This is in accordance with the conclusion obtained by light scattering measurements.

Vibration-dependent Crystal Form of Isotactic Polypropylene under Nonisothermal Crystallization

A study concerning the effect of vibration on the crystal structure and morphology for isotactic polypropylene(iPP) was conducted. The crystallite size, crystal structure and crystallinity of iPP under or without vibration treatment were investigated by means of differential scanning calorimetry(DSC) and wide-angle X-ray diffraction(WAXD). The results reveal that the crystallinity of the vibrated samples decreases at a high cooling rate, but it remains constant at a low cooling rate because of the chain relaxation of iPP. It has been found that vibration obviously increases the content of β-form of crystal phase and the amount of β-crystal mainly depends on the vibration amplitude.

Experiment and simulation of foaming injection molding of polypropylene/nano-calcium carbonate composites by supercritical carbon dioxide

Microcellular injection molding of neat isotactic polypropylene(iPP) and isotactic polypropylene/nano-calcium carbonate composites(i PP/nano-CaCO_3) was performed using supercritical carbon dioxide as the physical blowing agent. The influences of filler content and operating conditions on microstructure morphology of i PP and i PP/nano-CaCO_3 microcellular samples were studied systematically. The results showed the bubble size of the microcellular samples could be effectively decreased while the cell density increased for i PP/nano-CaCO_3 composites, especially at high CO_2 concentration and back pressure, low mold temperature and injection speed, and high filler content. Then Moldex 3D was applied to simulate the microcellular injection molding process, with the application of the measured ScCO_2 solubility and diffusion data for i PP and i PP/nano-Ca CO_3 composites respectively. For neat i PP, the simulated bubble size and density distribution in the center section of tensile bars showed a good agreement with the experimental values. However, for i PP/nano-CaCO_3 composites, the correction factor for nucleation activation energy F and the pre-exponential factor of nucleation rate f_0 were obtained by nonlinear regression on the experimental bubble size and density distribution. The parameters F and f_0 can be used to predict the microcellular injection molding process for i PP/nano-CaCO_3 composites by Moldex 3D.

Determination and Temperature Dependence of Plateau Modulus for Polymerization of Propylene to Isotactic Polypropylene with Ultra-high Molecular Weight under Catalysis of Ziegler-Natta Catalyst

The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.

EPITAXIAL CRYSTALLIZATION OF POLY(ε-CAPROLACTONE)ON HIGHLY ORIENTED ISOTACTIC POLYPROPYLENE

Electron microscope and electron diffraction have been used to study epitaxial crystallization of poly(ε-caprolactone)(PCL).on highly oriented film of isotactic polypropylene(iPP).The results obtained from bright field(BF)electron micrograph and electron diffraction indicate that the PCL can epitaxially grow on iPP substrate and form cross-hatched lamellar texture.The c axes of PCL are ±500 apart from the c axes of iPP. The contact planes of the two kinds of crystals are(010)of iPP and(100) of PCL,respectively.

Preparation of Ultra-High Molecular Weight Polypropylene Using Ziegler-Natta Catalyst via Combining Internal Electron Donor and Cocatalyst Loading

Due to the development of the new energy industry,polypropylene with ultra-high molecular weight plays a crucial role for battery isolation membrane.This work investigated the effect of internal electron donor of Ziegler-Natta catalyst system on the molecular weight of the obtained polypropylene.The scanning electron microscope(SEM)and Canon camera were used to characterize the surface morphologies of catalyst particles and polymer particles,respectively.Compared with the polypropylene particles featuring a spherical shape,these study results confirmed that the morphology duplication theory from the catalyst particle to the morphology of polymer particle was exhibited.The gel permeation chromatography(GPC)results revealed that the obtained polypropylene has a much higher average molecular weight than those prepared by conventional method.The Fourier transform infrared spectrometry(FT-IR)and X-ray photoelectron spectroscopy(XPS)revealed that the carbonyl oxygen atom on ester group was preferentially bound to Mg and Ti,as compared to the ether oxygen atom.The XPS results showed that the ratio of Ti^(3+)/Ti^(4+)could be changed by internal electron donors.When Ti3+content was nearly 99%in the Ziegler-Natta catalyst system,isotactic polypropylene with an ultra-high molecular weight of up to 1.42×10^(6)g/mol was obtained by Cat.3.This result implied that internal electron donor ID3 could reduce theβ-hydride elimination reaction to further increase the molecular weight of the obtained polymer.

TIPS behavior for IPP/nano-SiO_2 blend membrane formation and its contribution to membrane morphology and performance

In the present work, the TIPS behavior of isotactic polypropylene(iP P)/di-n-butyl phthalate(DBP)/dioctyl phthalate(DOP)/nano-SiO_2 system and the competition relation between liquid–liquid phase separation and polymer crystallization are successfully adjusted by adding nano-SiO_2. The liquid–liquid phase separation temperature of the system increases with increasing nano-SiO_2 content. Besides, iP P crystallization temperature is also changed after adding nano-SiO_2. IPP/nano-SiO_2 blend hollow fiber microporous membrane is prepared via TIPS method. SEM photos show that the membrane exhibits mixed morphology combining cellular structure relating to liquid–liquid phase separation and branch structure originating from polymer crystallization. The relative weight of cellular structure first decreases and then increases with the increase of nano-SiO_2 content. Furthermore, porosity, connectivity among pores and pure water flux of the membrane first increase and then decrease with increasing nano-SiO_2 content. However, mechanical performance of the membrane is improved at all times with increasing nano-SiO_2 content.

A DYNAMIC MECHANICAL ANALYSIS STUDY OF THE TRANSITION BEHAVIOUR OF I-PP/EPDM BLENDS

The transition behaviour of the blends of isotactic polypropylene (i-PP) with ethylene-propylene terpolymer (EPDM) containing 42 wt% propylene was investigated by dynamic mechanical analysis technique (DMA). Owing to its high propylene content, EPDM is compatible with i-PP to some degree. The interaction between the two components was strengthened. As expected, for partially compatible system the glass transition temperature of i-PP in the blends shifted to lower temperature. It was found that there existed two transitions, αEPDM and βEPDM, for the EPDM used in this work. The former was considered to be the glass transition of the random chain segments of EPDM, while the latter the local motion of the long ethylene sequences in EPDM. The unusual transition behaviour of αEPDM in the blends was explained in terms of the greater thermal expansion of EPDM and the compatibility of the two components. On the other hand, the βEPDM changed with the composition of the blends in a regular manner.

Enantioselective Alternating Copolymerization of Propylene with Carbon Monoxide Using Cationic Palladium-Chiral Diphosphine Catalyst

Enantioselective alternating copolymerization of carbon monoxide with propylene was carried out using palladium catalyst modified by 1,4-3,6-dianhydro-2,5-dideoxy-2,5-bis (diphenylphosphino)-L-iditol (DDPPI). The chiral diphosphine was proved to be effective at enantioselective copolymerization. Optical rotation, elemental analysis, H-1, C-13-NMR and IR spectra showed that the copolymer was optically active, isotactic, alternating poly(1,4-ketone) structure.

PREPARATION AND MORPHOLOGY OF ISOTACTIC POLYPROPYLENE WITH HIGH CONTENT OF β CRYSTALLINE FORM

Isotactic polypropylene (iPP) with high content of ~ crystalline form was prepared by adding a series of new p form nucleators. The spherulites and morphology of//farm iPP (//-iPP) were investigated by wide-angle X-ray diffraction(WAXD), polarizing microscope (PLM), scanning electron microscope (SEM) and small-angle light scattering (SALS). WAXD experimental results indicate that the amount of p form in iPP (K_x) increases with increasing /~ nucleator content from zero to 0.07 wt% or crystallization temperature T_c from 20 to 120℃ and that the highest K_x value is up to 0.95. PLM observations suggest that p spherulites exhibit bright color and that their Maltese Crosses display some concentric banding of a rather spiky, jagged character. Their !amellae are smooth and relaxed layer-plate like structure by SEM and their SALS H_v patterns arc four-petalled.

A STUDY ON THE MORPHOLOGY AND PROPERTIES OF IPP/IIR BLENDS

The effect of isobutylene-isoprene rubber (IIR) on the crystallizing behavior of isotactic polypropylene (IPP) as well as the morphology of the blends in relation with its properties have been studied by DSC, WAXD, polarized light microscope, SEM and mechanical properties test. The experimental results show that IIR has slight influence on melting point, crystallinity, crystallization rate of IPP. It seems certain that IIR has not entered into IPP phase in melt state. IIR has retarding action on the growth of IPP crystal and is an effective nucleating agent of IPP spherulites. The impact strength of the blend increases rapidly with IIR content more than 30 parts; the tensile strength of the blend, however, decreases as IIR content increases. The temperature and time of alter heat-treatment also have great influence on the impact strength of the blend. The impact strength of IPP/IIR (100/20) heat-treated at about 130℃ for 2h is 5 times as high as that of the untreated blend.

STRUCTURE AND PROPERTIES OF POLY (N-VINYLCARBAZOLE) OBTAINED VIA ASYMMETRICALLY STEREOSELECTIVE POLYMERIZATION

The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtained via asymmetrically stereoselective polymerization have been studied by using **1H NMR spectra, UV spectra, DSC analysis and GPC. The steric microstructure i.e. the content of isotactic sequences was found to be increased by using AIBN to ( minus )Sp***** plus ( plus )CSA***** minus as the initiators or catalysts and the mole extinction coefficient to be decreased. Bimodal molecular weight distribution (MWD)s of the obtained PVCZs were caused by two propagating species of the free ions and the ion-pairs associated with the organic salts during polymerization. (Author abstract) 19 Refs.

The Synthesis of Isotactic Polypropylene with Spherical Morphology via Supported Metallocene Catalyst

Polymerization of propylene was carried out under bulk process at 70 degrees C using the supported metallocene catalyst with four kinds of SiO2 as carrier with triethylaluminum used as cocatalyst. The morphology of the products was studied by SEM. It was found the property of the carriers gave great effect on the fine structure of the products as well as the apperance.

Characterization of Isotactic Polypropylene/Talc Composites Prepared by Extrusion Cum Compression Molding Technique

Extrusion-Compression molded isotactic polypropylene (iPP) composites containing 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% of talc filler were studied by scanning electron microscopy (SEM), simultaneous thermal analysis (STA) and physical testing. The scanning electron microscope (SEM) micrographs of neat iPP and composites with 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% talc content show that neat PP, 10 wt%, 20 wt%, and 30wt% talc composites surface is smooth in comparison to 40 wt% and 50 wt% talc composites. It is also observed that talc is dispersed uniformly in the matrix and this uniform dispersion is not decreased even with talc content as high as 30 wt% talc. The composites of 40 wt% and 50 wt% talc contain more crack, agglomerates or larger particles. Bulk density of the composites decreases with the increase of talc content. With the increase of percentage of talc and period of immersion, the water absorption (WA) increases. Thermal analyses indicate a considerable increase of thermal stability of the composites with filler addition.