13Carbon nuclear magnetic resonance of ethylene–propylene–1‐decene terpolymers

Many studies have been reported on the ¹³C NMR characterization of ethylene–α‐olefin copolymers, but only a few have been reported on terpolymers. The incorporation of an α‐olefin into the polyethylene chain changes the structure and, consequently, the properties of the polymer obtained. Looking for new products, we obtained a series of ethylene–propylene–1‐decene terpolymers with the metallocenic system rac‐ethylene bisindenyl zirconium dichloride/methylaluminoxane. We performed a complete ¹³C NMR characterization of these terpolymers qualitatively and quantitatively. Here we present a detailed study of the ¹³C NMR chemical shifts, triad sequence distributions, monomer average sequence lengths, and reactivity ratios for these terpolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2531–2541, 2003     

Microstructure of metallocene isotactic propylene‐co‐1‐pentene‐co‐1‐hexene terpolymers

This study aims at characterizing in depth the microstructure of propylene‐co‐1‐pentene‐co‐1‐hexene terpolymers, which have been recently reported to develop the isotactic polypropylene δ trigonal polymorph when the total comonomer content is high enough. Such a specific crystalline form had been only reported so far in the analogous copolymers containing either 1‐pentene or 1‐hexene. A comparative ¹³C NMR study in solution of the aforementioned terpolymers and copolymers allows asserting the random insertion of both comonomers during chain growth under the polymerization conditions used. The reaction parameters, mainly catalyst and temperature, have been chosen for the purpose of assuring relatively high molar mass polymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2537–2547     

Synthesis and characterization of ethylene‐propylene‐1‐pentene terpolymers

Ethylene (E), propylene (P), and 1‐pentene (A) terpolymers differing in monomer composition ratio were produced, using the metallocenes rac‐ethylene bis(indenyl) zirconium dichloride/methylaluminoxane (rac‐Et(Ind)₂ZrCl₂/MAO), isopropyl bis(cyclopentadienyl)fluorenyl zirconium dichloride/methylaluminoxane (Me₂C(Cp)(Flu)ZrCl₂/MAO, and bis(cyclopentadienyl)zirconium dichloride, supported on silica impregnated with MAO (Cp₂ZrCl₂/MAO/SiO₂/MAO) as catalytic systems. The catalytic activities at 25 °C and normal pressure were compared. The best result was obtained with the first catalyst. A detailed study of ¹³C NMR chemical shifts, triad sequences distributions, monomer‐average sequence lengths, and reactivity ratios for the terpolymers is presented. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 947–957, 2008     

Isotactic poly(propylene‐co‐1‐pentene‐co‐1‐hexene) terpolymers: Synthesis,molecular characterization,and evidence of the trigonal polymorph

Terpolymers based on propylene with 1‐pentene and 1‐hexene as comonomeric units are satisfactorily synthesized using a metallocene catalyst. Thus, several terpolymers are prepared with distinct overall compositions in comonomers as well as three different 1‐pentene/1‐hexene ratios at a given composition to evaluate the influence on polymerization activity, intrinsic viscosity, and microstructural details. The new trigonal δ polymorph is observed in those quenched terpolymers with a global content in comonomers of about 14 mol %, independently of the ratio between both comonomers. However, preliminary results indicate a profound influence of that ratio on the crystallization rate. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3251–3259     

Radiochemical aging of ethylene–propylene–diene monomer elastomers. I. Mechanism of degradation under inert atmosphere

This article is devoted to the study of electron‐beam‐induced degradation under argon atmosphere of an ethylene–propylene–diene monomer (EPDM, based on 5‐ethylidene 2‐norbornene) and an ethylene–propylene rubber (EPR) containing the same molar ratio of ethylene/propylene. The chemical structure modifications of polymeric samples were analyzed by ultraviolet–visible and IR spectroscopies. Crosslinking reactions were deduced by measuring the changes in gel fraction and the degree of swelling in n‐heptane. Irradiation of EPDM and EPR created trans‐vinylene, vinyl, vinylidene, and dienic‐type unsaturations. The radiochemical yields for unsaturation formations in EPDM and EPR were similar. Degradation also involved crosslinking and the production of molecular hydrogen. The comparison between EPDM and EPR showed that the diene (in which a double bond is consumed with a high radiochemical yield) contributes to the increase in rate and intermolecular bridges density. Mechanisms are proposed to account for the main routes of EPDM degradation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1239–1248, 2004     

Ethylene–propylene copolymerization behavior of ansa‐dimethylsilylene(fluorenyl)(amido)dimethyltitanium complex: Application to ethylene–propylene–diene or ethylene–propylene–norbornene terpolymers

Copolymerization behavior of ethylene (E) and propylene (P) using ansa‐dimethylsilylene(fluorenyl)(amido)dimethyltitanium complex was investigated. P was more reactive than E regardless of the chain‐end monomer unit, which was very unusual in the coordination polymerization system. The terpolymerizations of E, P and norbornene (NB) or 5‐ethylidene‐2‐norbornene (5E2N) were also performed. The each content in the E/P/NB terpolymer was independently controlled by the initial concentration of NB and E/P feed ratio. Glass transition temperature (T_g) of the terpolymer was raised in proportion to the NB content and close to that of the corresponding NB/E random copolymer with the same NB content. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 685–691     

Diels–Alder reaction of 2,7‐dichloroquinoline‐5,8‐dione with a thiazole o‐quinodimethane. Assignment of the regiochemistry by 1H–13C HMBC correlations

The Diels–Alder reaction between a thiazole o‐quinodimethane and 4,6‐dichloroquinoline‐5,8‐dione gave 6‐chloro‐9‐azaanthra[2,3‐b]thiazole‐5,10‐dione as a single regioisomer. Its structure was assigned by 2D ¹H–¹³C HMBC short‐ and long‐range correlations. Measuring the spectra in CF₃CO₂D indicated that both nitrogen atoms of pyridine and thiazole rings are deuterated. Copyright © 2001 John Wiley & Sons, Ltd.     

Crystallization behavior of isotactic propylene‐1‐hexene random copolymer revealed by time‐resolved SAXS/WAXD techniques

The crystallization behavior of isotactic propylene‐1‐hexene (PH) random copolymer having 5.7% mole fraction of hexene content was investigated using simultaneous time‐resolved small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray diffraction (WAXD) techniques. For this copolymer, the hexene component cannot be incorporated into the unit cell structure of isotactic polypropylene (iPP). Only α‐phase crystal form of iPP was observed when samples were melt crystallized at temperatures of 40 °C, 60 °C, 80 °C, and 100 °C. Comprehensive analysis of SAXS and WAXD profiles indicated that the crystalline morphology is correlated with crystallization temperature. At high temperatures (e.g., 100 °C) the dominant morphology is the lamellar structure; while at low temperatures (e.g., 40 °C) only highly disordered small crystal blocks can be formed. These morphologies are kinetically controlled. Under a small degree of supercooling (the corresponding iPP crystallization rate is slow), a segmental segregation between iPP and hexene components probably takes place, leading to the formation of iPP lamellar crystals with a higher degree of order. In contrast, under a large degree of supercooling (the corresponding iPP crystallization rate is fast), defective small crystal blocks are favored due to the large thermodynamic driving force and low chain mobility. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 26–32, 2010     

Poly(1‐hexene) with long methylene sequences and controlled branches obtained by a thermostable α‐diimine nickel catalyst with bulky camphyl backbone

1‐Hexene polymerizations catalyzed by α‐diimine nickel complexes after activation with modified methylaluminoxane were performed at various reaction temperatures. Effects of catalyst structure and polymerization temperature on activity and polymer microstructure were evaluated in detail. Bulky catalyst 1b with camphyl backbone exhibited good control ability and greatly enhanced thermal stability to be capable of polymerizing 1‐hexene at 80°C. The poly(1‐hexene)s with long methylene sequences and dominate branches (methyl and butyl) were synthesized using catalyst 1b . Differential scanning calorimetry analysis further confirmed that long polymethylene block (? (CH₂)_n? , n > 20) was formed in the poly(1‐hexene)s with melting point of 64°C obtained by catalyst 1b on the basis of initial branched model polyethylene. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Chain microstructure of homogeneous ethylene‐1‐alkene copolymers and characteristics of single site catalysts using a direct 13C NMR peak method. Part II. Application to ethylene–propylene copolymers showing inversion

All relevant ¹³C NMR signals of a series of 19 homogeneous ethylene–propylene copolymers were used to fit the first‐order Markov reactivity ratios of the catalyst and the theoretical feeds. The copolymers cover a broad range of comonomer incorporations, from 17.0 to 56.5%, and show both primary (1,2) and secondary (2,1) insertions. As expected, two solutions are found, the normal solution showing a better fit and reliability > 99.5%. The reactivity ratios, r₁₂ = 20.0, r₁₃ = 162.0, r₂₁ = 0.015, r₂₃ = 1.3, and r₃₁ = 0.060, provide direct information about the vanadium‐based catalyst, the kinetics, and the chain microstructure. The values also explain the comonomer content‐dependent inversion and even predict a 100% secondary insertion PP homopolymer. With these results, the direct peak method shows that the use of all relevant ¹³C NMR peaks improves the accuracy of first‐order Markov modeling. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 738–746, 2006     

Separation of ethylene‐propylene copolymers and ethylene‐propylene‐diene terpolymers using high‐temperature interactive liquid chromatography

Ethylene‐propylene‐diene terpolymers (EPDM) are generally amorphous and, therefore, do not crystallize from solution. Consequently, fractionation techniques based on crystallization, such as crystallization analysis fractionation or temperature rising elution fractionation, cannot be used to analyze their chemical composition distribution. Moreover, no suitable chromatographic system was known, which would enable to separate them according to their chemical composition. In this study, two different sorbent/solvent systems are tested with regard to the capability to separate EPDM‐terpolymers and ethylene‐propylene (EP)‐copolymers according to chemical composition. While porous graphite/1‐decanol system is selective towards ethylene and ethylidene‐2‐norbornene, carbon coated zirconia/2‐ethyl‐1‐hexanol is preferentially selective towards ethylene. Consequently, the earlier system enables to separate both EP copolymers and EPDM according to the chemical composition and the latter mainly according to the ethylene content. The results prove that the chromatographic separation in both sorbent/solvent systems is not influenced by molar mass of a sample or by its long chain branching. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Preparation of ultra high molecular weight amorphous poly(1‐hexene) by a Ziegler–Natta catalyst

High molecular weight polymers such as poly (α‐olefin)s play a key role as drag‐reducing agents which are commonly used in pipeline industry. Heterogeneous Ziegler–Natta catalyst system of MgCl₂.nEtOH/TiCl₄/donor was prepared using a spherical MgCl₂ support and utilized in synthesis of poly(1‐hexene)s with a viscosity average molecular weight (M_v) up to 3.5 × 10³ kDa. The influence of effective parameters including Al/Ti ratio, polymerization temperature, monomer concentration, effect of alkylaluminus type on the productivity, and molecular weight of the products was evaluated. It was suggested that the reactivity of the Al‐R group and the bulkiness of the cocatalyst were correlated to the performance of the Ziegler–Natta catalyst at different polymerization time and temperatures, affecting the catalyst activity and M_v of polymers. Moreover, bulk polymerization method leads to higher viscosity average molecular weights, revealing the remarkable effect of polymerization method on the chain microstructure. Fourier transform infrared, ¹³C Nuclear magnetic resonance spectra, and DSC thermogram of the prepared polymers confirmed the formation of poly(1‐hexene). The properties of the polymers measured by vortex test showed that these polymers could be used as a drag‐reducing agent. Drag‐reducing behaviors of the polymers exhibited a dependence on the M_v of the obtained polymers that was changed by variation in polymerization parameters. Copyright © 2016 John Wiley & Sons, Ltd.     

The microstructure determination of ethylene‐styrene‐propylene terpolymers at triad level by high‐temperature two‐dimensional NMR spectra

To further extend temperature range of application and low temperature performance of the ethylene‐styrene copolymers, a series of poly(ethylene‐styrene‐propylene) samples with varying monomer compositions and relatively low glass‐transition temperatures (T_g = −28 – 22 °C) were synthesized by Me₂Si(Me₄Cp)(N‐t‐Bu)TiCl2/MMAO system. Since the ¹³C NMR spectra of the terpolymers were complex and some new resonances were present, 2D‐¹H/¹³C heteronuclear single quantum coherence and heteronuclear multiple bond correlation experiments were conducted. A complete ¹³C NMR characterization of these terpolymers was performed qualitatively and quantitatively, including chemical shifts, triad sequence distributions, and monomer average sequence lengths. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 340–350     

Chain microstructure of homogeneous ethylene‐1‐alkene copolymers and characteristics of single site catalysts using a direct 13C NMR peak method. Part III. Application to ethylene–propylene copolymers showing no inversion

All relevant ¹³C NMR signals of two series of seven homogeneous ethylene–propylene copolymers were used to fit the second‐order Markov reactivity ratios of the catalysts and the theoretical feeds. The copolymers cover a very broad range of comonomer incorporations, from about 10 to 93%, and show only primary (1,2) insertions. For both series, solutions are found with reliabilities >>99.5%. The reactivity ratios, r₁₁₂ = 2.54, r₁₂₁ = 0.12, r₂₁₂ = 2.05, and r₂₂₁ = 0.29 for the used Zirconocone and r₁₁₂ = 1.69, r₁₂₁ = 0.32, r₂₁₂ = 1.56, and r₂₂₁ = 0.51 for the hafnocene, provide direct information about the metallocenes, the kinetics, and the chain microstructure. With these results, the direct peak method demonstrates that the use of all relevant ¹³C NMR peaks enables accurate second‐order Markov modeling, revealing subtle differences between copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 747–755, 2006     

Kinetics,polymer molecular weights,and microstructure in zirconocene‐catalyzed 1‐hexene polymerization

1‐Hexene was polymerized by rac‐(dimethylsilyl)bis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dichloride catalyst and methylaluminoxane cocatalyst over the temperature range 0–100 °C. The polymerization rate, polymer molecular weight, and polymer microstructure (stereospecificity and regiospecificity) were studied as a function of the temperature and the concentrations of monomer, catalyst, and cocatalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3802–3811, 2000     

Metallocene copolymers of propene and 1‐hexene: The influence of the comonomer content and thermal history on the structure and mechanical properties

The relationships between the structure and properties have been established for copolymers of propylene and 1‐hexene synthesized with an isotactic metallocene catalyst system. The most important factor affecting the structure and properties of these copolymers is the comonomer content. The thermal treatment, that is, the rate of cooling from the melt, is also important. These factors affect the thermal properties, the degree of crystallinity, and therefore the structural parameters and the viscoelastic behavior. A slow cooling from the melt favors the formation of the γ phase instead of the α modification. Regarding the viscoelastic behavior, the β relaxation, associated with the glass‐transition temperature, is shifted to lower temperatures and its intensity is increased as the 1‐hexene content raises. The microhardness values are correlated with those of the storage modulus deduced from dynamic mechanical thermal analysis curves, and good linear relations have been obtained between these parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1253–1267, 2006     

Complete 1H and 13C NMR chemical shift assignment of N1‐ and N3‐alkylnitrohistidines and of 1,4,6,7‐tetrahydroimidazo[4,5‐b]pyridines

¹H and ¹³C NMR data for 13 nitrohistidine derivatives are reported, providing a diagnostic method for the elucidation of the N¹‐( 2 ) and the N³‐substituted ( 3 ) regioisomers. Spectral assignments of constrained surrogates of His ( 4 ) and of the His–Gly dipeptide ( 5 and 6 ) are also described. The structure of the compounds was confirmed by NOESY and heteronuclear (¹³C, ¹H) short‐ and long‐range correlation experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

Complete assignment of 1H and 13C NMR spectra of α‐phenylsulfinyl‐N‐methoxy‐ N‐methylpropionamide and some p‐substituted derivatives

The complete assignment of the ¹H and ¹³C NMR spectra of the diastereomeric pairs of some α‐arylsulfinyl‐substituted N‐methoxy‐N‐methylpropionamides with the substituents methoxy, methyl, chloro, nitro is reported. Copyright © 2008 John Wiley & Sons, Ltd.     

1H and 13C spectral assignment of o‐chloroformyl substituted 1,4‐dihydropyridine derivatives

The ¹H and ¹³C NMR spectroscopic data for alkyl 4‐aryl‐6‐chloro‐5‐formyl‐2‐methyl‐1,4‐dihydopyridine‐3‐carboxylates were fully assigned by combination of one‐ and two‐dimensional experiments (DEPT, HMBC, HMQC, COSY, NOE). Copyright © 2002 John Wiley & Sons, Ltd.