Alkylamines‐intercalated α‐zirconium phosphate as latent thermal anionic initiators

The reaction of glycidyl phenyl ether (GPE) with 1‐aminoalkanes‐intercalated α‐zirconium phosphate (α‐ZrP·1‐aminoalkane): 1‐aminoalkanes 1‐aminopropane (α‐ZrP·Pr), 1‐aminobutane (α‐ZrP·Bu), 1‐aminooctane (α‐ZrP·Oct), and 1‐aminohexadecane (α‐ZrP·Hed) was carried out at varying temperatures for 1 h periods. Reaction progress was not observed until the reactants were heated to 80 °C or above. On increasing the temperature, the conversion factors increased such that, at 140 °C, conversions of 62% (α‐ZrP·Pr), 60% (α‐ZrP·Bu), 67% (α‐ZrP·Oct), and 64% (α‐ZrP·Hed) were obtained. The thermal stabilities as latent initiators were tested: GPEs reacted with α‐ZrP·Pr, α‐ZrP·Bu, and α‐ZrP·Oct at 40 °C for 360 h achieved conversions of 83, 55, and 59%, respectively. In contrast, the reaction in the presence of α‐ZrP·Hed did not proceed at 40 °C. The order of the thermal stability of GPE in the presence of α‐ZrP·1‐aminoalkane intercalation compounds was: α‐ZrP·Hed > α‐ZrP·Bu ≈ α‐ZrP·Oct > α‐ZrP·Pr. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1854–1861     

Mechanistic study of ring‐opening copolymerization of ɛ‐caprolactam with epoxide: Development of novel thermosetting epoxy resin system

We investigated the mechanism of the ring‐opening copolymerization of ?‐caprolactam (?‐CL) with glycidyl phenyl ether (GPE) to afford poly(?‐CL‐co‐GPE) as a model reaction of the thermal curing of certain epoxy resins with ?‐CL. The reaction of ?‐CL and GPE proceeded efficiently in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) at 170^°C for 2 h. The monomer reactivities r₁ of ?‐CL and r₂ of GPE calculated according to the Fineman‐Ross method and the Kelen‐Tüdös method were 0.58 and 5.52, respectively. These values indicate that poly(?‐CL‐co‐GPE) has a pseudo‐block gradient copolymer. Based on these results, we examined the thermal curing reactions of certain epoxy resins with ?‐CL. The corresponding novel cured products were obtained quantitatively, and each of them showed a high glass transition temperature and high thermal stability, presumably due at least in part to a pseudo‐block gradient primary structure resembling that of poly(?‐CL‐co‐GPE). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2220–2228     

Convenient and useful synthesis of N‐carboxyanhydride monomers through selective cyclization of urethane derivatives of α‐amino acids

A new convenient synthesis of N‐carboxyanhydrides (NCAs) of α‐amino acids was achieved by selective cyclization of urethane derivatives of α‐amino acids. The urethanes were readily synthesized via N‐carbamoylation of α‐amino acids by bis(4‐nitrophenyl)carbonate quantitatively. These urethanes having 4‐nitrophenoxy moiety were tolerant to air and moisture to allow their facile purification and storage. When the obtained urethanes were heated in 2‐butanone at 60 °C, they underwent the selective cyclization via intramolecular nucleophilic attack of the carboxyl moiety to the urethane moiety with releasing 4‐nitrophenol, leading to the successful formation of the corresponding NCAs. Addition of carboxylic acids remarkably stabilized the formed NCAs during the reaction, allowing their isolation in high yields. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3839–3844, 2009     

Ring opening polymerization and copolymerization of L‐lactide and ɛ‐caprolactone by bis‐ligated magnesium complexes

Seven magnesium complexes ( 1–7 ) were synthesized by reaction of new ( L ³ ‐H – L ⁵ ‐H ) and previously reported ketoimine pro‐ligands with dibutyl magnesium and were isolated in 59–70% yields. Complexes 1–7 were characterized fully and consisted of bis‐ligated homoleptic ketoiminates coordinated in distorted octahedral geometry around the magnesium centers. The complexes were investigated for their ability to initiate the ring opening polymerization (ROP) of l ‐lactide (L‐LA) to poly‐lactic acid (PLA) and ?‐caprolactone (?CL) to poly‐caprolactone in the presence of 4‐fluorophenol co‐catalyst. For L‐LA polymerization, complexes containing ligand electron‐donating groups ( 1–5 ) achieved >90% conversion in 2 h at 100 °C, while the presence of CF₃ groups in 6 and 7 slowed or resulted in no PLA detected. With ?CL, ROP initiated with 1–7 resulted in lower percentage conversion with similar electronic effects. Moderate molecular weight PLA polymeric material (14.3–21.3 kDa) with low polydispersity index values (1.23–1.56) was obtained, and ROP appeared to be living in nature. Copolymerization of L‐LA and ?CL yielded block copolymers only from the sequential polymerization of ?CL followed by L‐LA and not the reverse sequence of monomers or the simultaneous presence of both monomers. Polymers and copolymers were characterized with NMR, gel permeation chromatography, and differential scanning calorimetry. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 48–59     

Ring‐opening polymerization of ϵ‐caprolactam and ϵ‐caprolactone via microwave irradiation

A novel process for synthesizing nylon‐6 and poly(?‐caprolactone) by microwave irradiation of the respective monomers, ?‐caprolactam and ?‐caprolactone, is described. The ring opening of ?‐caprolactam to produce nylon‐6 was performed in a microwave oven by the forward power being controlled to about 90–135 W in the presence of an ω‐aminocaproic acid catalyst (10 mol %) and for periods of 1–3 h at temperatures varying from 250 to 280 °C. The ring opening of ?‐caprolactone to produce poly(?‐caprolactone) was performed in a microwave oven by the forward power being controlled to about 70–100 W for a period of 2 h in the presence of stannous octoate with and without 1,4‐butanediol over a temperature range of 150–200 °C. The yields, conditions of the reactions, and properties of the products generated relative to the thermal processes are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2264–2275, 2002     

Living cationic polymerization of α‐methyl vinyl ethers using SnCl4

Cationic polymerization of α‐methyl vinyl ethers was examined using an IBEA‐Et_1.5AlCl_1.5/SnCl₄ initiating system in toluene in the presence of ethyl acetate at 0 ～ ?78 °C. 2‐Ethylhexyl 2‐propenyl ether (EHPE) had a higher reactivity, compared to corresponding vinyl ethers. But the resulting polymers had low molecular weights at 0 or ?50 °C. In contrast, the polymerization of EHPE at ?78 °C almost quantitatively proceeded, and the number‐average molecular weight (M_n) of the obtained polymers increased in direct proportion to the EHPE conversion with quite narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.05). In monomer‐addition experiments, the M_n of the polymers shifted higher with low polydispersity as the polymerization proceeded, indicative of living polymerization. In the polymerization of methyl 2‐propenyl ether (MPE), the living‐like propagation also occurred under the reaction conditions similar to those for EHPE, but the elimination of the pendant methoxy groups was observed. The introduction of a more stable terminal group, quenched with sodium diethyl malonate, suppressed this decomposition, and the living polymerization proceeded. The glass transition temperature of the obtained poly(MPE) was 34 °C, which is much higher than that of the corresponding poly(vinyl ether). This poly(MPE) had solubility characteristics that differed from those of poly(vinyl ethers). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2202–2211, 2008     

Conformational analysis of the disaccharide methyl α‐d‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d‐mannopyranoside monohydrate

The crystal structure of methyl α‐d ‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d ‐mannopyranoside monohydrate, C₁₅H₂₆O₁₂·H₂O, ( II ), has been determined and the structural parameters for its constituent α‐d ‐mannopyranosyl residue compared with those for methyl α‐d ‐mannopyranoside. Mono‐O‐acetylation appears to promote the crystallization of ( II ), inferred from the difficulty in crystallizing methyl α‐d ‐mannopyranosyl‐(1→3)‐β‐d ‐mannopyranoside despite repeated attempts. The conformational properties of the O‐acetyl side chain in ( II ) are similar to those observed in recent studies of peracetylated mannose‐containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in ( II ) elongates by ～0.02 Å upon O‐acetylation. The phi (?) and psi (ψ) torsion angles that dictate the conformation of the internal O‐glycosidic linkage in ( II ) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated ( II ) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ～16°) than for ? (Δ = ～6°).     

Molecular composites composed of castor oil‐modified poly(ε‐caprolactone) and self‐assembled hydroxystearic acid fibers

After (R)‐12‐hydroxystearic acid (HSA) was mixed at 100 °C with the castor oil‐modified poly(ε‐caprolactone) (CO‐PCL) prepared by the ring‐opening polymerization of ε‐caprolactone in the presence of castor oil, the mixture was gradually cooled to room temperature to give a solidified CO‐PCL/HSA composite. The CO‐PCL/HSA sample showed an exothermic peak at around 67–71 °C which was lower than the melting point of HSA (76.8 °C), indicating the formation of mesogenic HSA aggregates. The rheological measurement of the CO‐PCL/HSA revealed the formation of HSA organogel at around 67–55 °C during the cooling process from the melt. Furthermore, the polarized and normal optical microscopic analyses of CO‐PCL/HSA on the cooling stage revealed that anisotropic fibrous materials are formed at around 60 °C and then the fibrous network propagated over the matrix polymer. The flexural modulus and storage modulus of the CO‐PCL/HSA composite increased with increasing HSA content. The CO‐PCL/HSA composite annealed at 60 °C for 2 h on the cooling process had a higher flexural and storage modulus than the sample without annealing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1281–1289, 2010     

Kinetics of hexene‐1 polymerization using [(N,N′‐diisopropylbenzene)‐2,3‐(1,8‐napthyl)‐1,4‐diazabutadiene] dibromonickel/methylaluminoxane catalyst system

Kinetics of hexene‐1 polymerization was investigated using [(N,N′‐diisopropylbenzene)2,3‐(1,8‐napthly)‐1,4‐diazabutadiene]dibromonickel/methylaluminoxane catalyst. Experiments were performed at varying catalyst and monomer concentrations in the temperature range of ?10 to 35 °C. First order time‐conversion plot shows a downward curvature at temperatures of 20 °C and 35 °C indicating the presence of finite termination reactions. A nonlinear plot of degree of polymerization (P_n) with respect to conversion indicates occurrence of transfer reactions and slow initiation. The experimental molar masses are higher than predicted, which implies that a fraction of catalyst species could not be activated or is deactivated at the early stages of the reactions. The efficiency of the catalyst (Cat_eff) varies from 0.77 to 0.89. The observed polydispersity of the poly(hexene‐1) s is in the range of 1.18–1.48. The reaction order was found to be 1.11 with respect to catalyst. The Arrhenius plot obtained using the overall propagation rate constant, k_p, at five different temperatures (?10, 0, 10, 20, and 35 °C) was found to be linear with an activation energy, E_a = 4.3 kcal/mol. Based on the results presented it is concluded that the polymerization of hexene‐1 under the above‐mentioned conditions shows significant deviation from ideal “living” behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1093–1100, 2007     

Fibrillar structure of resorbable microblock copolymers based on 1,5‐dioxepan‐2‐one and ε‐caprolactone

The copolymerization of 1,5‐dioxepan‐2‐one (DXO) and ε‐caprolactone, initiated by a five‐membered cyclic tin alkoxide initiator, was performed in chloroform at 60 °C. Copolymers with different molar ratios of DXO (25, 40, and 60%) were synthesized and characterized. ¹³C NMR spectroscopy of the carbonyl region revealed the formation of copolymers with a blocklike structure. Differential scanning calorimetry measurements showed that all the copolymers had a single glass transition between ?57 and ?49 °C and a melting temperature in the range of 30.1–47.7 °C, both of which were correlated with the amount of DXO. An increase in the amount of DXO led to an increase in the glass‐transition temperature and to a decrease in the melting temperature. Dynamic mechanical thermal analysis measurements confirmed the results of the calorimetric analysis, showing a single sharp drop in the storage modulus in the temperature region corresponding to the glass transition. Tensile testing demonstrated good mechanical properties with a tensile strength of 27–39 MPa and an elongation at break of up to 1400%. The morphology of the copolymers was examined with polarized optical microscopy and atomic force microscopy; the films that crystallized from the melt showed a short fibrillar structure (with a length of 0.05–0.4 μm) in contrast to the untreated solution‐cast films. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2412–2423, 2003     

Free‐radical copolymerization of ethyl α‐hydroxymethylacrylate with methyl methacrylate by reversible addition–fragmentation chain transfer

The controlled free‐radical homopolymerization of ethyl α‐hydroxymethylacrylate and copolymerization with methyl methacrylate were performed in chlorobenzene at 70 °C by the reversible addition–fragmentation chain transfer polymerization technique with 2,2′‐azobisisobutyronitrile as the initiator. 2‐Phenylprop‐2‐yl dithiobenzoate and 2‐cyanoprop‐2‐yl dithiobenzoate were used as chain‐transfer agents in the homopolymerization, whereas only the former was used in the copolymerization. All reactions presented pseudolinear kinetics. The effect of the monomer feed ratio on the copolymerization kinetics was examined. The conversion level decreased when the proportion of ethyl α‐hydroxymethylacrylate in the monomer feed was larger. Kinetic studies indicated that the radical polymerizations proceeded with apparent living character according to experiments, demonstrating an increase in the molar mass with the monomer conversion and a relatively narrow molar mass distribution. All copolymers were statistical in chain structure, as confirmed by determinations of the monomer reactivity ratios. The monomer reactivity ratios were determined, and the Mayo–Lewis terminal model provided excellent predictions for the variations of the intermolecular structure over the entire conversion range. Additionally, the chemical modification of poly(ethyl α‐hydroxymethylacrylate) was carried out to introduce glucose pendant groups into the structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5618–5629, 2006     

Preparation and physical properties of poly(4,4′‐diamino‐3′‐carbamoylbenzanilide terephthalamide) and poly(4,4′‐diamino‐3′‐carbamoylbenzanilide isophthalamide) films

To prepare thermally stable and high‐performance polymeric films, new solvent‐soluble aromatic polyamides with a carbamoyl pendant group, namely poly(4,4′‐diamino‐3′‐carbamoylbenzanilide terephthalamide) (p‐PDCBTA) and poly(4,4′‐diamino‐3′‐carbamoylbenzanilide isophthalamide) (m‐PDCBTA), were synthesized. The polymers were cyclized at around 200 to 350 °C to form quinazolone and benzoxazinone units along the polymer backbone. The decomposition onset temperatures of the cyclized m‐ and p‐PDCBTAs were 457 and 524 °C, respectively, lower than that of poly(p‐phenylene terephthalamide) (566 °C). For the p‐PDCBTA film drawn by 40% and heat‐treated, the tensile strength and Young's modulus were 421 MPa and 16.4 GPa, respectively. The film cyclized at 350 °C showed a storage modulus (E′) of 1 × 10¹¹ dyne/cm² (10 GPa) over the temperature range of room temperature to 400 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 775–780, 2000     

Photoinduced and thermal reactions of α‐cyano‐β‐bromomethylcinnamide with 1‐benzyl‐1,4‐dihydronicotinamide

The photoinduced reaction of a mixture of (Z)‐α‐cyano‐β‐bromomethylcinnamide (1) and (E)‐α‐cyano‐β‐bromomethylcinnamide (2) with 1‐benzyl‐1, 4‐dihydronicotinamide produces a mixture of the (E)‐ and (Z)‐ isomers of α‐cyano‐β‐methylcinnamide (3 and 4). Using spin‐trapping technique for monitoring reactive intermediate, it is shown that the reaction proceeds via electron transfer‐debromination‐H abstraction mechanism. The thermal reaction of the same substrate with BNAH at 60°C in the dark gives three products: the (E)‐ and (Z)‐isomers of α‐cyano‐β‐methylcinnamide and a dehydrodimeric product; 2, 7‐dicyano‐3, 6‐diphenylocta‐2, 4, 6‐trien‐1, 8‐dioic amide (7). Based on product analysis, scavenger experiment and cyclic voltammetry, an electron transfer‐debromination‐disproportionation mechanism is proposed.     

Synthesis of novel hyperbranched poly(ester‐amide)s based on neutral α‐amino acids via “AD + CBB′” couple‐monomer approach

A series of novel hyperbranched poly(ester‐amide)s (HBPEAs) based on neutral α‐amino acids have been synthesized via the “AD + CBB′” couple‐monomer approach. The ABB′ intermediates were stoichiometrically formed through thio‐Michael addition reaction because of reactivity differences between functional groups. Without any purification, in situ self‐polycondensations of the intermediates at elevated temperature in the presence of a catalyst afforded HBPEAs with multihydroxyl end groups. The degrees of branching (DBs) of the HBPEAs were estimated to be 0.40–0.58 and 0.24–0.54 by quantitative ¹³C NMR with two different calculation methods, respectively, depending on polymerization conditions and structure of monomers. The influences of catalyst, temperature, and intermediate structure on the polymerization process and molecular weights as well as properties of the resultant polymers were investigated. FTIR, NMR, and DEPT‐135 NMR analyses revealed the branched structure of the resultant polymers. The HBPEAs possess moderately high molecular weights with broad distributions, glass transition temperatures in the range of ?25.5 to 36.5 °C, and decomposition temperatures at 10% weight loss under nitrogen and air in the regions of 243.4–289.1 °C and 231.4–265.6 °C, respectively. Among them, those derived from D ,L ‐phenylalanine display the lowest degree of branching, whereas the highest glass transition temperature and the best thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [Ph? C(CH₃)(CH₂OH)–PIB–CH₂? C(CH₃)₂Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from ?75 to ?50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ～ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and ¹H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and ¹H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002     

Synthesis of phosphate‐pendant polymers and their application to thermally latent polymeric initiators

A novel phosphate monomer, O‐p‐(methacryloyloxymethyl)benzyl O,O‐diethyl phosphate (MDP) was synthesized by the reaction of diethyl phosphorochloridate with 1,4‐benzenedimethanol, followed by the reaction with methacryloyl chloride in the presence of triethylamine. The radical polymerization of MDP and copolymerization with methyl methacrylate were carried out in the presence of 2,2′‐azobisisobutyronitrile (3 mol %) in dimethylacetamide at 60 °C for 20 h to afford phosphate‐pendant polymers. The polymerization of glycidyl phenyl ether (GPE) was carried out with the phosphate‐pendant polymer as an initiator in the presence of ZnCl₂. The polymerization did not proceed below 90 °C but rapidly proceeded above 90 °C to afford polyGPE. The phosphate‐pendant polymer served as a good thermally latent polymeric initiator. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3365–3370, 2001     

Anionic polymerization of N,N‐dialkyl‐2‐methylenebut‐3‐enamide: Effect of alkyl substituents on polymerization behavior

Anionic polymerizations of three 1,3‐butadiene derivatives containing different N,N‐dialkyl amide functions, N,N‐diisopropylamide (DiPA), piperidineamide (PiA), and cis‐2,6‐dimethylpiperidineamide (DMPA) were performed under various conditions, and their polymerization behavior was compared with that of N,N‐diethylamide analogue (DEA), which was previously reported. When polymerization of DiPA was performed at ?78 °C with potassium counter ion, only trace amounts of oligomers were formed, whereas polymers with a narrow molecular weight distribution were obtained in moderate yield when DiPA was polymerized at 0 °C in the presence of LiCl. Decrease in molecular weight and broadening of molecular weight distribution were observed when polymerization was performed at a higher temperature of 20 °C, presumably because of the effect of ceiling temperature. In the case of DMPA, no polymer was formed at 0 °C and polymers with relatively broad molecular weight distributions (M_w/M_n = 1.2) were obtained at 20 °C. The polymerization rate of PiA was much faster than that of the other monomers, and poly(PiA) was obtained in high yield even at ?78 °C in 24 h. The microstructure of the resulting polymers were exclusively 1,4‐ for poly(DMPA), whereas 20–30% of the 1,2‐structure was contained in poly(DiPA) and poly(PiA). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3714–3721, 2010     

Homogeneous tandem catalysis of the bis‐(diphenylphosphino)‐amine/chromium tetramerization catalyst with metallocene catalysts

Homogeneous tandem catalysis of the bis(diphenylphoshino)amine‐chromium oligomerization catalyst with the metallocenes Ph₂C(Cp)(9‐Flu)ZrCl₂ and rac‐EtIn₂ZrCl₂, is discussed. GC, CRYSTAF, and ¹³C NMR analysis of the products obtained from reactions at constant temperatures show that during tandem catalysis, α‐olefins, mainly 1‐hexene and 1‐octene, are produced from ethylene by the oligomerization catalyst and subsequently built into the polyethylene chain. At 40 °C the Cr/PNP catalyst acts as a tetramerization catalyst while the polymerization catalyst activity is low. Copolymerization of ethylene and the in situ produced α‐olefins have also been carried out by increasing the temperature from 40 °C, where primarily oligomerization takes place, to above 100 °C, where polymerization becomes dominant. The melting temperature of the polymer is dependent on the catalyst and cocatalyst ratios as well as on the temperature gradient followed during the reaction, while the presence of the oligomerization catalyst reduces the activity of the polymerization catalyst. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6847–6856, 2006     

Electron spin resonance study on chemical‐crosslinking reaction mechanisms of polyethylene using a chemical agent. VI. Effect of α‐methyl styrene dimer

The effect of α‐methyl styrene dimer (AMSD), which is used as a scorch retarder, on the reaction mechanisms of the chemical crosslinking of polyethylene (PE) with dicumyl peroxide (DCP) at high temperatures was investigated using electron spin resonance. When AMSD was added to PE containing DCP, the AMSD radical was observed; however, the PE alkyl radical or allyl radical presence was not detected. At 145 °C, crosslinking was obstructed as a result of the reaction between AMSD and alkyl radicals. As the temperature increased, AMSD fragmented to form 2‐phenyl‐2‐propyl and double bonds in PE. This generation of double bonds, however, accelerated crosslinking at 180 °C and was more effective than when AMSD was not present. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2151–2156, 2001     

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