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Trans -polydiene rubber family as high-performance tire stock possessed excellent dynamic properties, including excellent anti fatigue, low rolling resistance, low heat buildup, good green strength, and low abrasion loss. Here, Reactor Granule Technology (RGT) was introduced into the field of synthetic rubber for the first time to produce trans -1.4-polyisoprene/ trans -1,4-poly(butadiene-co-isoprene) rubber alloy, which showed significant improvement in rubber synthetic technologies and great development in abundance of trans -rubber family. A series of trans -polyisoprene alloys with excellent spherical morphology were successfully synthesized by using sequential multistage polymerization. The alloy was fractionated into four fractions by temperature-gradient fractionation, and the fractionation was analyzed by 1 H NMR, 13 C NMR, DSC and WAXD.

Isotactic poly(butene-1) (iPB) with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.

In melt recrystallization of trans-1,4-polyisoprene (TPI), polymorphism was examined via differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). Two crystal modifications of TPI, namely β-TPI (metastable form) and α-TPI (thermodynamic stable form), exhibit difference in their ability to hold the chain cluster in the melt, and β-TPI is considered to exhibit stronger melting memory effect when compared with that of the α-TPI. Irrespective of whether the chain cluster is from the α-TPI or β-TPI, the reduced energy barrier for nucleation leads to the formation of α-TPI. Furthermore, melt recrystallization of TPI benefiting from the contribution of chain clusters makes more chains packed in an orderly manner during recrystallization, and this ultimately leads to increases in crystallinity if the recrystallization occurs at low temperatures.

Room-temperature annealing process lies between high-temperature mixing process and high-temperature vulcanization process in rubber processing technology, and definitely affects the performances of rubber composites. In this work, the influences of room-temperature annealing on the structures and properties of unfilled SSBR/BR blends and silica-filled SSBR/BR composites have been evaluated in detail. For the unfilled SSBR/BR vulcanizates, the tensile strength, tear strength and fatigue resistance deteriorate due to the reduced rubber matrix strength with lower crosslinking density and less chain entanglements with annealing time extending. While for the SSBR/BR/SiO2 vulcanizates with dual networks including filler-filler networks and polymer-polymer networks, the tensile strength and fatigue resistance reduce, the tear strength, dynamical properties concerning abrasion, heat built-up and rolling resistance improve obviously with extending annealing time, which are attributed to the enhanced filler-polymer interactions, severe silica flocculation, and reduced internal hysteresis loss with annealing time prolonging. This work is expected to provide fundamental understanding of the annealing process in the rubber processing technology for development of high-performance rubber composites.

The discovery of Ziegler − Natta catalysts has been one of the greatest developments in technology for the synthesis of stereoregular polymers in both academy and industry since the 1950s. In particular, the development of the fourth generation Ziegler − Natta catalyst with MgCl2 as support brings a revolutionary improvement to the properties of manufactured polyolefins and stimulates people to explore the stereospecific polymerization of α-olefin and diene monomers, which supplies the power to synthesize a new type of polyolefin materials. Although research on single-site catalysts has attracted a lot of attention in recent years, the ‘old’ and conventional Ziegler − Natta catalysts are still being developed vigorously due to their unique industrial advantages such as low cost, high catalytic efficiency and high stereospecificity. In this mini-review, we mainly summarize the development of the conventional supported Ziegler − Natta catalyst system and the stereoregular polyolefins synthesized with supported Ziegler − Natta catalysts. © 2013 Society of Chemical Industry

Diphenyl (4-hydroxyphenyl) hexadecyl phosphonium bromide (POH) -modified montmorillonite (POHMMT) was used to prepare a novel TiCl4/MgCl2/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiCl4/MgCl2/POHMMT compound catalyst. The POH surfactants don’t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na+MMT nanocomposites were produced with the TiCl4/MgCl2/Na+MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites.

Polyisoprene (PI) with a high content of cis-1,4 (up to 95%) or cis-1,4/3,4 binary structures was synthesized using a cobalt system in toluene. The cobalt system, which exhibited high activities (up to 3.50 × 106 g PI (mol Co)−1 h−1), contained a series of 2-(benzimidazolyl)-6-(1-(arylimino)ethyl)pyridine cobalt(II) dichlorides activated with ethylaluminium sesquichloride. The nature of the ligands and the reaction conditions significantly affected both the catalytic performance of the cobalt complexes as well as the structures of the resultant PI. The stereospecific polymerization of isoprene could be tuned via changing either the co-catalyst or solvent: for example, increased content of 3,4 PI (up to 36.6%) was achievable in heptane in the presence of diethylaluminium chloride. Sequence distribution analysis by 13C NMR spectroscopy indicated that most 3,4 units occurred randomly in the PI chains. © 2013 Society of Chemical Industry

Selectively epoxidized trans-1,4-polyisoprene (SETPI) and randomly epoxidized trans-1,4-polyisoprene (RETPI) were fabricated successfully through modified surface water-phase suspension epoxidation and solution random epoxidation, respectively. The effects of fabricated method and epoxy degree of ETPI on the glass transition temperature (T g), dynamic mechanical properties and phase separation phenomenon of the as-fabricated polymer have been investigated by different scanning calorimetry, dynamic mechanical analyzer and phase contrast microscope. The double bonds and epoxy groups sequence structure distribution of different ETPI have been observed and analyzed by 13C-NMR. There is a great deal of difference in the microstructure and sequence distribution of epoxy group in ETPI with different synthesis methods and epoxy degree. The results show that distribution of epoxy group in SETPI is nonuniform which brings about the phase separation.

The isotactic poly(1-butene)/ poly(1-butene-co-propylene) in-reactor alloy was prepared by heterogeneous titanium catalyst system. The differences of crystal phase transformation time, phase transformation rate and phase transformation time between Form I and Form II at a given transformation degree at 25 °C by fourier transform infrared spectroscopy(FT-IR) were discussed. It can be seen that the transformation from Form II to I of the alloy was significantly accelerated by the increase of propylene structure unit. With the further increase of the content of the propylene unit in the alloy, the transformation may be ignored and Form I can be formed immediately at 25 °C. The change of the spherulite of pure poly(1-butene) and alloy also be observed and discussed.

Polypropylene (PP)/polybutene-1 (PB) alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene (iPP) particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the iPP particles. Finally, iPP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly(buteneco-propylene) random copolymers and poly(butene-block-propylene) block copolymers. SEM measurements verified that the PB phases with size in the range of 300–400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.

TiCl4/MgCl2/clay compound catalyst was prepared by chemical reaction. Exfoliated polypropylene (PP)/clay nanocomposites were synthesized by in situ polymerization with this compound catalyst. Effects of polymerization temperature, polymerization time, propylene pressure, solvent consumption and pre-treat time of catalyst on catalyst activity and catalytic stereospecificity were studied. Under optimal conditions, activity of the nano-compound catalyst is about 88.3 kg/(mol Ti·h). Isotacticity of PP obtained in the nanocomposites is in the range of 89%–99%, and its melting temperature is about 159°C. The weight-average molecular weight of PP can reach 6.7 × 105 − 7.8 × 105, and the molecular weight distribution is between 7.7 and 7.9.

MgCl2/TiCl4/diether is a fifth-generation Ziegler–Natta catalyst for the commercial polymerization of propylene. The outstanding features of this catalyst are the high activity and high isotacticity for propylene polymerization without using an external electron donor. In this study, we explored the copolymerization of propylene and 1-octene with MgCl2/TiCl4/diether catalyst. It was found that MgCl2/TiCl4/diether catalyst showed higher polymerization activity and led to greater 1-octene content incorporation, compared with a fourth-generation Ziegler–Natta catalyst (MgCl2/TiCl4/diester). With an increase in 1-octene incorporation in polypropylene chains, the melting temperature, glass transition temperature and crystallinity of the copolymers decreased distinctly. The microstructures of the copolymers were characterized using 13C NMR spectroscopy, and the copolymer compositions and number-average sequence lengths were calculated from the dyad concentration and distribution. This result is very important for the in-reactor polyolefin alloying process, especially for the case of a single catalyst and two-step (or two-reactor) process. Copyright © 2011 Society of Chemical Industry

The effect of molecular weight on the polymorphic transformation of isotactic poly(1-butene)(iPB) under room temperature had been investigated by fourier transform infrared spectroscopy(FT-IR). The phase transformation time, phase transformation rate and phase transformation time difference between phase I and phase II at a given transformation degree were used to analysis the phase transformation kinetics of iPB aging at room temperature. The results show that the reduction of phase II can occur quickly at room temperature and seem less dependent on the molecular weight. However, the molecular weight has great effect on the formation of phase I. When the phase transformation degree for phase I reach 90%, a distinct transformation time difference can be observed. In order to clearly explain the difference in the reduction of phase II and the growth of phase I, a phase transformation model from the chain conformation level for iPB with different molecular weight have been drawn. DSC analysis was used to support the proposed model.

Polypropylene/clay nanocomposites (PPCNs) were prepared via an in situ polymerization method with a Ziegler-Natta/clay compound catalyst in which the MgCl2/TiCl4 catalyst was embedded in the clay galleries. The wide-angle X-ray diffraction and transmission electron microscopy results showed that the clay particles were highly exfoliated in the polypropylene (PP) matrix. The nonisothermal crystallization kinetics of these PPCNs were investigated by differential scanning calorimetry at various cooling rates. The nucleation activity were calculated by Dobreva's method to demonstrate that the highly dis- persed silicate layers acted as effective nucleating agents. The Avrami, Jeziorny, Ozawa, and Mo methods were used to describe the nonisothermal crystallization behavior of the PP and PPCNs. Various parameters of nonisother- mal crystallization, such as the crystallization half-time, crystallization rate constant, and the kinetic parameter F(t), reflected that the highly exfoliated silicate layers sig- nificantly accelerated the crystallization process because of its outstanding nucleation effect. The activation energy values of the PP and PPCNs determined by the Kissinger method increased with the addition of the nanosilicate layers. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 162- 172, 2011

Electrospun nanofibrous membrane is an approved drug carrier. However, the radionuclide carrier used an electrospun membrane is rare. In this study, Poly(lactide- co -glycolide)(PLGA) nanofibrous nonwovens were prepared through electrospinning technology, and then surface modification of the nonwoven was performed to stably conjugate the radioisotope with the fibrous membrane. A novel PLGA nanofibrous nonwoven conjugated with radioactive yttrium 90 Y for tumor internal radiotherapy was prepared for the first time. Evaluation of the stability of the radioisotope indicated that the leakage of 90 Y from the PLGA membranes can be neglected after 24 h incubation in saline. The retention of 90 Y on the PLGA membrane was 75% when five half lives of 90 Y expired and the vast majority of radioactive decay had occurred. This labeled nanofibrous membrane function as a novel radio-medical appliance with excellent surface hydrophilic and mechanical properties that can be directly implanted into the lesions not only to locally kill the cancerous cells but also to play the anti-adhesion role at where surgical procedures have been made to remove the tumor tissue.

Four kinds of imidazolium surfactants with high thermal stability were designed and synthesized accordingly. The structures of these surfactants were characterized by 1 H NMR spectra. The TGA results indicated that the thermal stabilities of these surfactants with saturated alkyl groups were relatively high and the initial decomposition temperatures at 5% weight loss ( T 0.05 ) were higher than 250 °C. Imidazolium(O) modified montmorillonite (MMT) was prepared by cation exchange. TGA results showed that the OMMT showed obviously higher thermal stability than the surfactants themselves and the T 0.05 values of OMMT were higher than 330 °C. The dihexadecane imidazolium (DHI) with two long tails has the ability to enlarge the interlayer spacing to a bigger degree compared with other imidazolium surfactants with only one long tail. Polypropylene(PP)/OMMT nanocomposites were prepared by solution blending and the effects of these surfactants with different structures on the silicate layer dispersion in PP matrix were measured.

A new method for destroying silicon tetrachloride has been developed, which based on a microwave plasma jet that operates at atmospheric pressure using hydrogen as work gas. Experiments showed that the silicon tetrachloride was dissociated into silicon and hydrogen chloride under the effect of the plasma jet. The silicon was deposited on the molybdenum substrate of the plasma reactor, which was yellow and typical nanosized particles. These solid samples have been analyzed by SEM, EDX, XRD, FT-IR and the active particle in the plasma is detected by atomic emission spectroscopy. The results show that the silicon tetrachloride is mainly transformed into nano-silicon with size of 54 nm. The dissociation efficiency reaches 50%.

Highly exfoliated isotactic-polypropylene/alkyl-imidazolium modified montmorillonite (PP/IMMT) nanocomposites have been prepared via in situ intercalative polymerization. TEM and XRD results indicated that the obtained composites were highly exfoliated PP/IMMT nanocomposites and the average thickness of IMMT in PP matrix was less than 10 nm, and the distance between adjacent IMMT particles was in the range of 20—200 nm. The isothermal crystallization kinetics of highly exfoliated PP/IMMT nanocomposites were investigated by using differential scanning calorimeter(DSC) and polarized optical microscope (POM). The crystallization half-time t 1/2 , crystallization peak time t max , and the Avrami crystallization rate constant K n showed that the nanosilicate layers accelerate the overall crystallization rate greatly due to the nucleation effect, and the crystallization rate was increased with the increase in MMT content. Meanwhile, the crystallinity of PP in nanocomposites decreased with the increase in clay content which indicated the PP chains were confined by the nanosilicate layers during the crystallization process. Although the well-dispersed silicate layers did not have much influence on spherulites growth rate, the nucleation rate and the nuclei density increased significantly. Accordingly, the spherulite size decreased with the increase in MMT content.

Although sodium alginate (SA) could not be electrospun from its aqueous solution, SA-based electrospun nanofibers can be fabricated with the help of polyethylene oxide (PEO). In this study, the influence of PEO on the electrospinnability of SA aqueous solution was investigated and the roles of chain entanglements and conformations of the blend system were emphasized. It was found that a little amount of PEO100 with high molecular weight could improve the electrospinnability of SA aqueous solution. However, a large amount of PEO2 with low molecular weight had no positive effect on the electrospinnability of SA aqueous solution. Dynamic laser light scattering (DLLS) results showed that only when the PEO molecular chains in aqueous solution were in an entangled state, PEO can enhance the electrospinnability of SA aqueous solution. The further study on rheological measurements showed that SA molecular chains could not form significant entanglements for the electrospinning even when the SA solution concentration approached concentrated regime. SA molecular chains are closely “overlapped” due to its rigid and extended conformation and cannot form effective chain entanglement. The main contribution of PEO100 to improve SA electrospinnability is offering entanglement sites and thereby enhancing the applicable entanglement degree of the blend system. Whereas, although the chain interaction between PEO2 and SA may improve slightly the flexibility of SA chains, the significant chain entanglements of the blend solution is not achieved. Three molecular models are proposed to depict visually the effect of PEO with different molecular weights on chain conformations and entanglements of SA.

Hyaluronic acid (HA) ultra-thin fibrous membranes by electrospinning technology had been fabricated successfully by our group. However, these HA fibrous membranes dissolve and decompose rapidly in water. In this study, chemical crosslinking of HA and HA based ultra-thin fibrous membranes was studied in detail. It was found that the chemically crosslinked pure HA ultra-thin fibrous membranes with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as the crosslinking agent did not show an obvious improvement in the water-resistance. However, by simply adding and changing the gelatin content, the degradation time of the HA based fibrous membranes could be effectively adjusted from one week to several months. That is with the increase in gelatin content, the water-resistance of the HA/gelatin bi-component membranes could be increased greatly. The crosslinked HA/gelatin bi-component membranes were evaluated in vitro by seeding with mouse embryonic fibroblasts (3T6-Swiss Albino). The results showed that the HA/gelatin fibrous membranes were cytocompatible and suitable for cell viability. However, cells were hard to attach and grow on the HA based membranes. Thus, the HA/gelatin fibrous membranes with controllable degradation rate could have good potential applications in the anti-adhesion and wound dressing fields.

The phase transition from α-tricalcium phosphate (α-TCP) into β-tricalcium phosphate (β-TCP) in tricalcium phosphate/hydroxyapatite (TCP/HA) composites was investigated by X-ray diffraction, differential scanning calorimetry, thermogravimetry and scanning electron microscopy in this study. The current experimental results indicated that the calcining temperature for the complete phase transition from α-TCP into β-TCP increased with the increasing HA content in the composite. HA/β-TCP biphasic composites with initial Ca/P molar ratios of 1.571, 1.600 and 1.636 were synthesized. The particle coarsening occurred significantly in the process of calcination.

As a natural biopolymer, sodium alginate (SA) has been widely used in the biomedical field in the form of powder, liquid, gel, and compact solid, but not in the form of nanofiber. Electrospinning is an effective method to fabricate nanofibers. However, electrospinning of SA from its aqueous solution is still a challenge. In this study, an effort has been made to solve this problem and find the key reasons that hinder the electrospinning of alginate aqueous solution. Through this research, it was found that pure SA nanofibers could be fabricated successfully by introducing a strong polar cosolvent, glycerol, into the SA aqueous solutions. The study on the properties of the modified SA solution showed that increasing glycerol content increased the viscosity of the SA solution greatly and, meanwhile, decreased the surface tension and the conductivity of the SA solution. The rheological results indicated that the increase in glycerol content could result in the enhanced entanglements of SA chains. Two schematic molecular models were proposed to depict the change of SA chain conformation in aqueous solution with and without glycerol. The main contribution of glycerol to the electrospinning process is to improve the flexibility and entanglement of SA chains by disrupting the strong inter- and intramolecular hydrogen bondings among SA chains, then forming new hydrogen bondings with SA chains.

The crystalline morphology and the liquid−liquid phase separation (LLPS) of an isotactic polypropylene/poly(ethylene-co-octene) (iPP/PEOc) polymer alloy prepared on a single multicatalyst reactor granule were studied by polarized optical microscope, phase contrast optical microscope, and scanning electron microscopy (SEM). We found that the LLPS process had a dominant effect on the final crystalline morphology of the iPP/PEOc polymer alloy. As the LLPS time was increased at 160 °C, more and more elastomer component was dispersed uniformly in the iPP spherulites as droplets, instead of being rejected to the outside and concentrated at the boundaries of the spherulites, when the sample was isothermally crystallized at 140 °C. The morphologies can be explained by the phase separation and crystallization kinetics. By simply changing the LLPS time, we could control the size of the elastomer droplets (for example between 1 and 10 μm) that dispersed in the iPP spherulites. Meanwhile, a special structural feature...

Polymorphism control of PVDF has been realized through electrospinning. PVDF fibrous membranes with fiber diameter in the range of 100 nm to several micrometers were produced by electrospinning and the crystal phase of electrospun PVDF fibers can be adjusted at the same time. Through the control of electrospinning parameters such as the solvent, electrospinning temperature, feeding rate, and tip-to-collector distance, PVDF fibrous membranes containing mainly α- or β- or γ-phase could be fabricated successfully.

Polystyrene (PS) surfaces with various morphologies have been produced by electrospinning or electrospraying, such as beads with different sizes and shapes, bead-on-string structures with different aspect ratios of the beads and fibers with different diameters and shapes. Both the solution properties and the electrospinning conditions affected the PS surface morphology obtained. The results of water contact angle (CA) measurement indicated that the surface morphology could affect the wettability distinctively. It was found that CA values of PS surfaces comprised merely fibers were in the range of 140°–150°. The CA values of PS surfaces comprised bead-on-string structures were usually about 150°. However, the CA values of PS surfaces consisted of particles could reach up to 160°, which shows a superhydrophobic property. A bilayer fibers-on-beads surface was verified to be stable and superhydrophobic.

electrospun for the purpose of improving electrospinning Summary: In the present study, electrospinning of hyaluronic acid (HA) and hyaluronic acid/gelatin (HA-GE) blends in N,N-dimethylformamide (DMF)/water-mixed solvents have been investigated. When the volume ratio of DMF to water was in the range of 1.5‐0.5, HA solutions could be electrospun into fibrous membranes successfully. The average diameter of HA fibers was about 200 nm. The HA-GE composite nanofibrous membranes with varied HA/GE weight ratio in the range of 100/20‐100/100 have also been successfully fabricated. The average diameter of HA-GE fibers was in the range of 190‐500 nm. The decrease in surface tension could promote fiber formation. Thus, an introduction of DMF that could decrease the surface tension distinctively, without significant change or increase inviscosity of the solution, could bypass the use of blowing-assisted electrospinning. Our postulated picture is that the lower surface tension could help the ejection of stream with relatively high viscosity and reduce or prevent the droplet formation during the spinning process. HA/GE (100/80) nanofibrous membrane produced by electrospinning.

The phase behavior of poly(ethylene-co-styrene) (PES) and poly(ethylene-co-butene) (PEB) blends has been studied. A closed-loop phase diagram was clearly observed in this weakly interacting system as the styrene content in the PES decreased to about 1 mol-%. At higher styrene contents the phase loop starts to interplay with the crystallization transformation at lower temperatures.

Poly(propylene)/monoalkylimidazolium-modified montmorillonite (PP/IMMT) nanocomposites were prepared by in situ intercalative polymerization of propylene with TiCl 4 /MgCl 2 /MMT catalyst. The PP synthesized possessed high isotacticity and molecular weight. Both wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the nanocomposite formation with exfoliated MMT homogeneously distributed in the PP matrix. A thermal stability study revealed that the nanocomposites possess good thermal stability.

This paper describes a new reactive blending approach to improve the compatibility of poly( l -lactide) (PLLA) and poly(ɛ-caprolacton) (PCL). For this purpose, the ring-opening polymerization of l -lactide (LLA) was carried out in the presence of PCL-OH (OH groups on one end). The P(CL-b-LLA) block copolymers were in situ formed during polymerization, and as a result, PLLA/P(CL-b-LLA) blends were obtained. The characterization of GPC and 1H NMR verified the synthesis of PLLA/P(CL-b-LLA) blends. Furthermore, the 13C NMR spectroscopy showed that no transesterification reaction occurred to a significant extent during LLA polymerization process. The in situ formed P(CL-b-LLA) compatibilizes the phase separated structure of PCL domains in PLLA matrix. The size of PCL domains in PLLA matrix became much smaller than that in a solution blended sample. The average sizes of PCL domains are controllable in the level of sub-micron scale.

The isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide) (PA-10T) was studied by differential scanning calorimetry. Several kinetic analyses were used to describe the crystallization process. The commonly used Avrami equation and the one modified by Jeziorny were used, respectively, to describe the primary stage of isothermal and nonisothermal crystallization. The Avrami exponent n was evaluated to be in the range of 2.36–2.67 for isothermal crystallization, and of 3.05–5.34 for nonisothermal crystallization. The Ozawa analysis failed to describe the nonisothermal crystallization behavior, whereas the Mo–Liu equation, a combination equation of Avrami and Ozawa formulas, successfully described the nonisothermal crystallization kinetics. In addition, the value of crystallization rate coefficient under nonisothermal crystallization conditions was calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 819–826, 2004

A high-trans 1,4-butadiene/isoprene copolymer (TBIP) was synthesized in a 5-L autoclave with hydrogen as an effective molecular weight modifier. The effects of hydrogen on the catalyst efficiency and molecular weight of the copolymers were investigated. The processability and physicomechanical properties of TBIP and their relationship to the composition, composition distribution, and molecular weight of TBIP were examined in detail. Increasing the H2 pressure effectively reduced the molecular weight of TBIP. The optimum Mooney viscosity of TBIP and the 1,4-butadiene molar content in the feed were 30–50 and 5–25%, respectively. No cis–trans isomerization was observed during the roll processing procedure for TBIP. The vulcanization characteristics of TBIP were similar to those of general rubbers, and no reverse vulcanization was observed for TBIP. A high green strength was the typical characteristic of TBIP. Vulcanized TBIP (TBIR) with an optimum composition and molecular weight presented outstanding antifatigue properties and low heat buildup in comparison with general rubbers. Compared with general sidewall stock [natural rubber (NR)/butadiene rubber (BR) = 50/50], TBIR exhibited a greater than 15-fold increase in its crack-initiation resistance. The other mechanical properties of TBIR were similar to those of 50/50 NR/BR. The heat-aging mechanism of TBIR was crosslinking aging. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2941-2948, 2004

采用负载钛－三异丁基铝催化体系合成高反式－1，4-丁二烯－异戊二烯共聚物，控制单体初始配比中丁二烯摩尔分数10%~20%，在适宜的聚合条件下所得共聚物T(下标 g)约－73℃，T(下标 m)约30℃。共聚物中丁二烯链节反式－1，4-结构摩尔分数大于90%，异戊二烯链节反式－1，4-结构摩尔分数大于98%。50℃溶液共聚合的竞聚率为5.7，0.17。

Polymerization behaviors of isoprene under different polymerization conditions with 2-(1-methyl-2-benzimidazolyl)-6-(1-(arylimino)ethyl) pyridine cobalt(II) dichloride and ethylaluminum sesquichloride or diethylaluminum chloride catalyst systemwere evaluated. The effects of temperature, solvents, [Al]/[Co] molar ratio, and the structure of cocatalysts on the catalyst activityand the characteristics of polyisoprenes (PIs) were investigated and optimum conditions for synthesizing stereoselective PIs wereobtained. The results showed that pre-catalyst activity was strongly influenced by polymerization temperature, [Al]/[Co] molar ratioand solvents, and the kinds of solvents and cocatalysts affected the microstructures of PIs greatly. V C 2013 Wiley Periodicals, Inc. J. Appl.Polym. Sci. 2014, 131, 39703. KEYWORDS: catalysts; properties and characterization; rubberReceived 18 December 2012; accepted 26 June 2013DOI: 10.1002/app.39703INTRODUCTION Great progress has been achieved in polyolefin industry with thedevelopment of coordination polymerization catalysts, whichplayed an important role in control of polymer stereoregular-ities. Among the coordination polymerization catalysts, tradi-tional Ziegler-Natta catalysts

Crystallization and polymorphic transformation of poly(1-butene)/(1-butene-co-propylene) in-reactor alloy (iPB/B-co-P) with different chain structure prepared by two stage sequential polymerization was investigated by DSC, FTIR and POM. As can be concluded from DSC results, the crystal form II to I transformation rate is enhanced with the increase of propylene unit content for alloy with the chain structure of isolated propylene unit distribution. However, the alloy which has the chain structure of predominant segmented propylene co-unit distribution, although with the highest propylene unit content and lowestmolecular weight, the crystal form II to I transformation rate still lower than two of the three alloys with isolated propylene unit and lower propylene unit content. This conclusion was also demonstrated by the subsequent in-situ FT-IR characterization. The crystallization process and morphology was investigated through polarized optical microscopy.

High molecular weight poly (lactic acid) (PLA) was obtained by chain extending with hexamethylene diisocyanate (HDI). The influences of the amount of chain extender, reaction time, and molecular weight changes of prepolymers on the poly(lactic acid) were investigated. PLA prepolymer with a viscosity, average molecular weight (Mη) of 2 × 104 g/mol was synthesized froml-lactide using stannous octoate as the catalyst. After 20 min of chain extension at 175°C, the resulting polymer hadMwof 20.3 × 104 g/mol andMnof 10.5 × 104 g/mol. Both FT-IR and1H-NMR verified that the structure of PLA did not change either before chain extending or after. The optically active characterized that the chain extending-product was left handed. DSC and XRD results showed that both theTgand the crystallinity of PLA were lowered by chain-extension reaction. The crystalline transformation happened in PLA after chain extending, crystallineα′form toαform.

For materials containing fluorine, it has been generally accepted that fluorinated segments or end groups tend to aggregate in the outer surface because of the low surface energy, which endows the fluorinated materials with special surface properties such as self-cleaning, superhydrophobicity, and so forth. However, for the electrospun fibrous membranes of polyurethane elastomers containing perfluoropolyether segments (FPU), abnormal fluorine aggregations in the core of the electrospun fibers were observed. The XPS analysis indicated a rather low fluorine content at the surface of the electrospun FPU fibers. Further study with dynamic light scattering and fluorescence showed that FPU chains can form aggregates in the concentrated solution. Therefore, it can be deduced that the rapid evaporation of solvent and fast formation of fibers during the electrospinning process could result in the freeze-in of the aggregated chain conformation and the depletion of fluorine units on the surface of the electrospun FPU fibers.

A new method for destroying silicon tetrachloride has been proposed, which is based on a microwave plasma jet that operates at atmospheric pressure using hydrogen as work gas. The influence of input power (P) and silicon tetrachloride concentration (phi) on the percent destruction and removal of SiCl(4) was investigated. And the reclaimed solid byproducts were characterized by SEM, EDX and XRD. Species in the plasma, which were identified by atomic emission spectroscopy were found to include no halogen. Results indicate that the destruction efficiency of silicon tetrachloride can reach 96% when P=800 W and phi=1.0%, and the main solid byproduct was Si. The silicon deposited on the molybdenum substrate of the plasma reactor was yellow and typical nano-sized particles with grain size of 54 nm.

Fibers prepared by melt spinning process from the PP (polypropylene)/organoclay nanocomposite were characterized in details with the aid of SEM, FTIR, XRD, DSC, and mechanical measurements. The results suggested that the lower content of organoclay (0.1%) added to the PP matrix increased the crystallinity and mechanical property (tensile strength) of the PP/organoclay nanocomposite fiber. With increasing the content of organoclay (≥ 0.3%), the crystallinity and the tensile strength both a little decreased, and the fiber containing organoclay exhibited multi-peaks at the same draw ratio during the heating process. Furthermore, the degree of orientation of the fiber increased a little with lower content of organoclay (0.1%) introduction to PP during the infrared dichroism measurement. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

1 Key Laboratory of Rubber-Plastics, Ministry of Education/Shandong Provincial Key Laboratory of Rubber-Plastics, School of Polymer Science and Engineering, Qingdao University of Science and Technology, Qingdao, Shandong 266042, China 2 State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China 3Department of Bioengineering, University of Washington, Seattle, WA 98195, USA 4Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing 10029, China

In this work, electrospun poly(lactide-co-glycolide) (PLGA) fibrous membranes were functionalized with radionuclides by surface modification. After the introduction of chitosan and bifunctional ligands (DTPA) on soft hydrolyzed PLGA nanofibrous membranes, more than 80% of the radionuclides (90Y) in aqueous solutions were attached as labels to the target nanofibers. To get a high chelating efficiency without changing the physical properties of the membranes, the hydrolysis conditions, the reactive media for the introduction of DTPA, and the chelating time were thoroughly investigated. These radionuclide labelled PLGA fibrous membranes have similar mechanical properties as human tissues. 90Y on PLGA nanofibers shows a desirable stability of more than four half-lives.

In this paper, a new core–shell nanostructure is proposed which is based on ZnS microspheres but the core and shell nanostructures are different. The conversion from such core–shell ZnS nanostructures to Zn(S,O)@ZnS ones and porous ZnO microspheres has been established by annealing ZnS microspheres in air atmosphere and investigated in detail by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction. During the conversion, both physical and chemical performances such as optical and photocatalytic properties can be tuned and enhanced.