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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]

A novel macromolecular auxiliary antioxidant with polyethylene (PE) as polymer skeleton and phosphites as side groups is prepared based on commercial ethylene‐vinyl acetate (EVA) copolymers and its potential as polyolefin stabilizers is studied in depth. The synthesis approach of this PE‐grafted antioxidant consists of a typical EVA hydrolysis reaction and a two‐step nucleophilic substitution reaction of PCl3, 2,4‐di‐tert‐butylphenol, and the hydrolysis product. Results of the thermogravimetric analysis show that the macromolecular structures endow the as‐synthesized antioxidant with much better thermal stability than that of the commercial antioxidant 168. In addition, antioxidant behaviors of the PE‐grafted antioxidants in polypropylene (PP) matrix are investigated in detail through characterization of the melt flow index of multiple‐extruded stabilized PP as well as the short‐term oxidation induction time test and the long‐term thermo‐oxidative aging test. Results show that even with extremely low content of the effective antioxidant groups, the as‐synthesized macromolecular antioxidant still has excellent antioxygenic properties. [ABSTRACT FROM AUTHOR]

Novel polyethylene‐based (PE‐based) antioxidants derived from commercially available ethylene‐vinyl acetate copolymer (EVA) with PE as the backbone and hindered phenols as side groups are prepared, and their potential for application as non‐migrating polyolefin stabilizers is investigated. The synthesis route contains the typical hydrolysis of EVA and transesterification reaction between the hydrolysis product and methyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate. Thermal stabilities of these PE‐based antioxidants (AO‐PE) are studied through thermal analysis under an air atmosphere and shown to be higher than those of antioxidant 1076 and antioxidant 1010 (AO‐1010) due to their macromolecular structures. Antioxidant activities of the AO‐PE are evaluated in polypropylene (PP) by measuring the melt flow index of multiple‐extruded stabilized PP, and the results demonstrate that the antioxidant effectiveness of these antioxidants is strongly related to the molecular weight. [ABSTRACT FROM AUTHOR]

A new synthetic procedure is described for the preparation of dendritic polyethylene brushes with polysiloxane as the main chain, describing for the first time that it is possible to simply and efficiently prepare highly branched architectures for this type of polymer. Furthermore, as a result of the polymer brush architecture, polyethylene acts as the side chains and Si-O-Si as the backbone. The number average molecular weight (Mn) of the polyethylene brushes, which is determined using a multiple angle laser light scattering detector, increases from 5946 to 27 684 g mol-1 while retaining relatively narrow polydispersities (1.5-2.4). The polymer brushes are characterized by solid 29Si NMR and high-temperature ¹H NMR spectra. In addition, X-ray photoelectron spectroscopy and gel permeation chromatography were used to confirm the structure. [ABSTRACT FROM AUTHOR]

ABSTRACT High melt flow rate (MFR) of polypropylene can improve its processability and its high isotacticity is favor of keeping good mechanical properties of polypropylene. In this study, as a convenient and effective method, the mixture of phosphate and alkoxysilane as mixed external donors for Ziegler-Natta catalyst is used to improve MFR of polypropylene. The MFR of polypropylenes prepared by mixed external donors is three to five time higher than that prepared by dicyclopentyl dimethoxysilane (Donor-D) alone, which is attributed to broad molecular weight distribution and low molecular weight of polypropylene prepared by mixed external donors. In addition, isotacticity and lamella thickness of polypropylene prepared by mixed external donors containing triisopropyl phosphate or phenyl-phosphonic acid dipentyl ester are very close to that prepared by Donor-D, which lead to keep high thermal properties and good mechanical properties for the polypropylenes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44704. [ABSTRACT FROM AUTHOR]

Chain-end-functionalized polyethylenes (Cef-PEs: PESSH (Cef1), PESfurfuryl (Cef2), PESNH2 (Cef4), PESNH2•HCl (Cef5), PESCOONa (Cef6), PESCHA(Cef7), PESSO3Na (Cef8), PESOH (Cef9) and PESCOOH (Cef10)) are synthesized by thiol-ene addition of vinyl-terminated polyethylene (v-PE) with 1,2-ethanedithiol, furfurylmercaptan, cysteamine, cysteamine hydrochloride, sodium thioglycolate, L-cysteine hydrochloride, sodium 2-mercaptoethanesulfonate, mercaptoethanol, and thioglycolic acid, respectively. PEStNCO (Cef3) is obtained by subsequent reaction of Cef9 with anhydrous 4,4′-MDI. Cef-PE1-8 are reported for the first time. The conversions of all the reactions are up to 95%-100%. All the Cef-PEs are characterized by NMR, GPC, DSC, FT-IR, and TGA. In the experiments, it is found that alkaline mercaptans and solvents are adverse to the thiol-ene click reactions. [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]

Four novel well-defined polyethylene-bound antioxidants (PE-bound antioxidants) with distinct secondary structures are synthesized via transesterification reactions between methyl 3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate and hydroxyl-terminated polyethylenes. The results of thermal gravimetric analysis under an air atmosphere demonstrate that the thermal stabilities of PE-bound antioxidants are higher than that of commercial antioxidant Irganox1076 and are strongly related to their chemical structures. Particularly, the most thermally stable PE-bound antioxidant is the one bearing both primary and secondary antioxidant moieties. The antioxidant activities of the PE-bound antioxidants are evaluated in polypropylene by their melt flow index. [ABSTRACT FROM AUTHOR]

The effects of different mixed external donors on the crystallization behavior and sequence length distribution of polypropylene prepared by MgCl2-supported TiCl4 Ziegler-Natta catalyst were studied through successive self-nucleation and annealing (SSA) technique. The SSA results show that the crystallization ability and the relative contents of long isotactic sequence length gradually increase with the increase of the relative component of Donor-1 (cyclohexylmethyldimethoxysilane, dicyclohexyl(dimethoxy)silane, and dipiperidinedimethoxysilane) in the different mixed external donors when the ratio of the mixed external donors/Ti (Si/Ti) is unchanged. The thickness distribution of lamellar also becomes broader, indicating the sequence length distribution of polypropylene gets broader. The crystallization ability and the relative contents of long isotactic sequence length of polypropylene prepared by the mixed cyclohexylmethyldimethoxysilane and n-propyltriethoxysilane (CN) external donors are lowest. However, the effect of the mixed dicyclohexyl(dimethoxy)silane and n-propyltriethoxysilane (HN) and the mixed dipiperidinedimethoxysilane and n-propyltriethoxysilane (PyN) external donors on the crystallization ability and sequence length of polypropylene are more significantly. Especially, the relative content of long isotactic sequence length increases sharply from 0.2 to 27.5% in the polypropylene chain of sample prepared by the mixed PyN external donors when the proportion of Donor 1 is running up to 90%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

A series of star block polymers with a hyperbranched core and 26 arms are successfully synthesized by atom transfer radical polymerization of styrene (St), and poly(ethylene glycol) methyl ether methacrylate from a hyperbranched polystyrene (HBPS) multifunctional initiator. All-solid polymer electrolytes composed of these multiarm star polymers and lithium salts are prepared. The influences of polyoxyethylene (PEO) side-chain length, PEO content, lithium salt concentration and type, and the structure of polymer on ionic conductivity are systematically investigated. The resulting polymer electrolyte with the longest PEO side chains exhibits the best ionic conductive properties. The maximum conductivity is 0.8 × 10−4 S cm−1 at 25°C with EO/Li = 30. All the prepared multiarm star block polymers possess good thermal stability. The mechanical property is greatly improved owing to the existence of polystyrene blocks in the multiarm star polymer molecules, and flexible films can be obtained by solution-casting technique. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [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]

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 [ABSTRACT FROM AUTHOR]

Melamine (MA), as the formaldehyde (FA) absorbent of polyoxymethylene (POM), was polymerically modified by a condensation reaction with FA to form the melamine-formaldehyde (MF) polycondensates with high molecular weight and comparatively high processing thermal stability. Ultrasonic irradiation was used for the synthesis, and ultrafine, crosslinked, and thermally stable MF polycondensates were obtained. The synthetic technique was discussed, and the thermal stabilization and nucleation effects of MF on POM were studied by the measurements of isothermal weight loss, balance torque, analysis of the formaldehyde emission amounts (FEAs), multiple extrusions, polarized light microscopy (PLM), isothermal and non-isothermal differential scanning calorimetry (DSC), and scanning electron microscopy (SEM), which indicated that the thermal stability and the crystallization performance of POM was greatly enhanced by using MF as a thermal stabilizer and nucleation agent. The MF prepared using ultrasonic irradiation can improve the mechanical properties of POM more effectively compared with that prepared with normal mechanical stirring. Copyright © 2008 John Wiley & Sons, Ltd. [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]