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Reversible addition-fragmentation chain transfer radical polymerization of styrene and maleic anhydride was successfully performed in continuous-flow microreactor. Results of the structural characterization showed that the obtained styrene-maleic anhydride (SMA) copolymers possessed controlled molecular weight, low dispersity and alternating structures. Subsequently, effects of the polymerization conditions, including reaction pressure, temperature, feed flowrate and tube length, on the polymerization kinetics and molecular structure of the SMA copolymers were investigated in detail. It was found that the reaction rate was increased as the reaction temperature increased within certain limits, as well as the feed flowrate due to the increased mass and heat transfer efficiency. Besides, first-order kinetics of the polymerization was observed when the reaction times were adjusted by only changing the tube length. Good stability was exhibited when the reaction conducted continuously for 10 h. This approach can reduce the reaction time significantly from several hours to about half an hour. [ABSTRACT FROM AUTHOR]

The new aminosilane compounds including Dimorpholindimethoxysilane (Donor-Pm), Di (1-methylpiperazine) dimethoxysilane (Donor-Pz) and Di (isopropylpiperazine) dimethoxysilane (Donor-Pi) were firstly synthesized and then employed as external donors for propylene polymerization with MgCl-supported Ziegler-Natta catalyst, compared with dipiperidine dimethoxysilane (Donor-Py). The effects of the aminosilane external donors on the catalytic activity, hydrogen response, and molecular weight distribution, crystalline ability, thermal property, isotactic sequence length, isotactic sequence distribution of polypropylene were studied by differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and self-nucleation and annealing (SSA), respectively. It was found that these new aminosilane compounds were conducive to improving the isotacticity of polypropylene and the catalytic activity. The GPC results showed that the molecular weight distribution of polypropylene prepared respectively by Donor-Pz or Donor-Pi with two N atoms on each amino substituent group was broader more than 8.0, especially for Donor-Pi with the large alkyl-substituted group on each nitrogen atom, the molecular weight distribution of polypropylene was about 11.2, which was much broader than that of industrial polypropylene about 4 ~ 5. The DSC results indicated that the degrees of crystallinity of polypropylene prepared by the aminosilane external donors were higher, and the crystallization ability of polypropylene prepared by Donor-Pi was lower but closed to that of polypropylene prepared by Donor-Py. The SSA results indicated Donor-Py and Donor-Pi were conducive to improving the relative contents of the highest isotactic component of polypropylene, and the lamellae thicknesses results showed the sequence length of polypropylene prepared by Donor-Py and Donor-Pi were longer, and the isotactic sequence distribution of polypropylene prepared by Donor-Py and Donor-Pi were broader. The study results showed that the new aminosilane donor Donor-Pi was conducive to improving the stereo-regularity of polypropylene, especially revealing that it was a simple and an effective method to synthesize broad molecular weight distribution of polypropylene by using appropriate aminosilane external donor for propylene polymerization. [ABSTRACT FROM AUTHOR]

As the external donor in Ziegler-Natta catalysts have an important influence on the stereo-defects distribution of polypropylene, the effects of the mixed external donors (the mixture of Donor-C (cyclohexylmethyldimethoxysilane) and Donor-N ( n-propyltriethoxysilane) ) on the isotactic sequence length and its distribution of polypropylene prepared by Ziegler-Natta catalyst through propylene bulk polymerization were studied through the Successive self-nucleating and annealing (SSA) and C-NMR techniques. The SSA results showed that the relative contents of the highest isotactic component and the lamellar thickness in the polypropylene chain gradually increased with the increase of the relative component of Donor-C in the C/N mixed external donors, indicating the isotactic sequence length of polypropylene got longer, and the lamellar thickness distribution of polypropylene became broader, revealing the isotactic sequence length distribution of polypropylene got broader. In addition, the C-NMR results showed that the average meso isotactic sequence length ( MSL) of polypropylene gradually increased with the increase of the content of Donor-C in the C/N mixed external donors, which was in good coincident with the results calculated from SSA, showing a good correspondence between the SSA and C-NMR techniques. [ABSTRACT FROM AUTHOR]

Discusses the synthesis of well-defined functional polyethylene graft copolymer via atom transfer radical polymerization (ATRP) process. Transformation of the pendant styrene groups into ATRP initiator sites; Determination of the quantitative hydrochlorination reaction; Lack of polar functional groups on its polymer chain.

Examines the design of a novel synthetic route used for preparing propylene-styrene copolymer. Catalysis of a propylene copolymerized with a 4-(3-butenyl) styrene by a propylene active catalyst to form a polymer which has a polypropylene main chain and some styryl side groups.

Details the development of a catalytic system with high polymeric activity. Intercalation of the cocatalysts, which included methylaluminoxane (MAO, between layers of montmorillonite (MMT) for ethylene oligomerization; Formation of a dual functional catalytic system by adding metallocene catalyst Me2Si(Ind)2ZrCl2 and MAO; Preparation of the PE/MMT nanocomposite by copolymerization of ethylene with α-olefins produced in situ from ethylene; Conclusion that the PE/MMT nanocomposites are stable and have more tensile strength; Temperature of maximum weight loss (Tonset).

Discusses the effects of co-catalysts on the morphology of isotastic polypropene prepared using metallocene catalyst. Preparation of the isotastic polypropene with good morphology and high bulk density; Proposal of the formation mechanism of active centers; Adjustment of the polymerization conditions to solve the problem of morphology.

Polynorbornene was synthesized by β -diketonate titanium / MAO (methylaluminoxane) catalysts. The polymerization activity was up to 8 × 103 g polymer/(mol Ti h). FT-IR, 1H NMR, 13C NMR and WAXD analyses showed that the polynorbornenes contained both ring-opening metathesis (trans and cis) and addition polymer chain structures and they are amorphous. The portions of trans- and cis- double bonds decreased when the polymerization temperature and Al/Ti molar ratio decreased. In addition, using 1,2-dichlorobenzene, instead of toluene, as the polymerization solvent increased the activity and produced the polymer containing more cis-double bonds. The glass transition temperature of the elastic polymers ranged from 330°C ∼ 400°C. [ABSTRACT FROM AUTHOR]

Examines the polymerization of a linear low-density polyethylene. Observation of high activity in the catalytic system; Determination of the melting point of the polymer; Production of narrow molecular weight distribution.

Investigates the polymerization method in the preparation of long-branched polyethylene (LBPE). Use of late transition metal and metallocene catalysts; Characteristics of LBPE; Determination of narrow molecular weight distribution.

Reports on the preparation of a series of high molecular weight amphiphilic graft copolymers. Esterification of the copolymers under different conditions; Study of the composition using nuclear magnetic resonance and fourier transform infrared spectroscopy.

Reports two novel Fe(II) diimine complexes that were synthesized. How they generate active catalytic systems when combined with MAO; Finding they oligomerize ethylene with high catalytic activity and high selectivity for α-olefins; The effects of substituents on the aryl ring, reaction temperatures and molar ratios of Al/Fe on catalytic activity and product distribution.

Polyethylene based polyurethanes (PE-PUs) with 20% ethyl branches were synthesized through hydrogenation reaction of linear and thermoplastic hydroxyl-terminated polybutadiene based polyurethanes (HTPB-PUs), which has not been explored widely. Linear and thermoplastic HTPB-PUs with Mw ranged from 130~280 kg/mol were synthesized by microwave-assisted reaction. More importantly, we systematically researched a series of reaction conditions to ensure the degree of hydrogenation meanwhile slow down the extent of degradation reaction of urethane bond. In addition, structure and thermal performance of PE-PUs have been investigated in the present work by NMR, FT-IR, DSC and TGA. The Mw of PE-PUs ranging from 120~207 kg/mol were carried out with a high temperature GPC. Moreover, the degree of crystalline of PE-PUs with 20% ethyl branches at the range of 10% to 33% were further explored by X-ray diffraction, which in turn certify that the PE-PUs possess certain strength but lower than polyethylene with no branches. [ABSTRACT FROM AUTHOR]