α‐Bis and α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polymers by atom transfer radical polymerization using 1,1‐bis[(4‐dimethylamino)phenyl]ethylene as tertiary diamine initiator precursor and functionalizing agent

The quantitative syntheses of α‐bis and α,ω‐tetrakis tertiary diamine functionalized polymers by atom transfer radical polymerization (ATRP) methods are described. A tertiary diamine functionalized 1,1‐diphenylethylene derivative, 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1), was evaluated as a unimolecular tertiary diamine functionalized initiator precursor as well as a functionalizing agent in ATRP reactions. The ATRP of styrene, initiated by a new tertiary diamine functionalized initiator adduct (2), affords the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3). The tertiary diamine functionalized initiator adduct (2) was prepared in situ by the reaction of (1‐bromoethyl)benzene with 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) in the presence of a copper (I) bromide/2,2′‐bipyridyl catalyst system. The ATRP of styrene proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene derivative (3) with predictable number‐average molecular weight (M_n) and narrow molecular weight distribution (M_w/M_n) in a high initiator efficiency reaction. The polymerization process was monitored by gas chromatography analysis. Quantitative yields of α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polystyrene (4) were obtained by a new post ATRP chain end modification reaction of α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3) with excess 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1). The tertiary diamine functionalized initiator precursor 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) and the different tertiary amine functionalized polymers were characterized by chromatography, spectroscopy and non‐aqueous titration measurements. Copyright © 2012 Society of Chemical Industry     

A Convenient Procedure for the Synthesis of Acetals from α‐Halo Ketones

A study for determining the scope and limitations of a procedure for synthesising ethylene acetals from haloketones is presented. The method uses 1,2‐bis(trimethylsilyloxy)ethane, BTSE, as reagent and Nafion^®‐TMS as catalyst. Two procedures have been tested: (A) stoichiometric amounts of the haloketone and BTSE and a catalytic amount of Nafion^®‐TMS were heated to reflux in chloroform solution, and (B) stoichiometric amounts of the reactants and a catalytic amount of Nafion^®‐TMS were heated to 90–100 °C in the absence of solvent. The following ketones have been tested: 2‐bromo‐1‐phenyl‐1‐ethanone, 2‐bromo‐cyclopentenone, 3‐bromo‐3‐methyl‐2‐butanone, 3‐chloro‐3‐methyl‐2‐butanone, 1‐bromo‐3,3‐dimethyl‐2‐butanone, 1‐chloro‐3,3‐dimethyl‐2‐butanone, 2‐bromocyclohexanone, 2‐chloro‐1‐cyclohexyl‐1‐ethanone, 1,1‐dibromo‐3,3‐dimethyl‐2‐butanone, 1,3‐dibromo‐3‐methyl‐2‐butanone, 1,3‐dibromo‐2‐butanone, 1,3‐dibromo‐2‐propanone, 2‐chloro‐1‐phenyl‐1‐ethanone, and endo‐2‐bromocamphor. Yields were in the range 57–100% with the exceptions of endo‐2‐bromocamphor which afforded <10% yield and the dibromoketones 1,1‐dibromo‐3,3‐dimethyl‐2‐butanone and 1,3‐dibromo‐3‐methyl‐2‐butanone for which the method failed. Factors determining the scope and limitations are briefly discussed. Full experimental details and spectroscopic data of the acetals are given.     

Poly(ether ether sulfone)s and sulfonated poly(ether ether sulfone)s derived from functionalized 1,1‐diphenylethylene derivatives

Symmetrically disubstituted 1,1‐diphenylethylene derivatives, 1,1‐bis[4‐(t‐butyldimethylsiloxy)phenyl]ethylene and 1,1‐bis(4‐hydroxyphenyl)ethylene, were prepared by new synthesis methods and employed as functionalized monomers in the preparation of new poly(ether ether sulfone) derivatives, with the introduction of the 1,1‐diphenylethylene unit along the polymer backbone. A series of parent 1,1‐diphenylethylene based poly(ether ether sulfone)s were prepared via (a) the cesium fluoride catalysed polycondensation reactions of dihalogenated diaryl sulfones with silylated bisphenols and (b) the base catalysed aromatic nucleophilic substitution polycondensation reaction between aromatic dihalogenated diaryl sulfones with bisphenols. The post‐polymerization sulfonation reaction via the thiol‐ene addition reaction of the poly(ether ether sulfone) precursor containing the 1,1‐diphenylethylene unit along the backbone, with sodium 3‐mercapto‐1‐propane sulfonate, afforded well‐defined sulfonated poly(ether ether sulfone), with the alkyl sulfonate group introduced pendant to the polymer backbone. The organic compounds and different polymer derivatives were characterized by standard chromatography, spectroscopy, spectrometry, thermal analyses, microscopy and X‐ray diffraction measurements. © 2016 Society of Chemical Industry     

Highly Enantioselective Phase‐Transfer Catalytic α‐Alkylation of α‐tert‐Butoxycarbonyllactams: Construction of β‐Quaternary Chiral Pyrrolidine and Piperidine Systems

A new enantioselective α‐alkylation of α‐tert‐butoxycarbonyllactams for the construction of β‐quaternary chiral pyrrolidine and piperidine core systems is reported. α‐Alkylations of N‐methyl‐α‐tert‐butoxycarbonylbutyrolactam and N‐diphenylmethyl‐α‐tert‐butoxycarbonylvalerolactam under phase‐transfer catalytic conditions (solid potassium hydroxide, toluene, −40 °C) in the presence of (S,S)‐3,4,5‐trifluorophenyl‐3,3′,5,5′‐tetrahydro‐2,6‐bis(3,4,5‐trifluorophenyl)‐4,4′‐spirobi[4H‐dinaphth[2,1‐c:1′,2′‐e]azepinium] bromide [(S,S)‐NAS Br] (5 mol%) afforded the corresponding α‐alkyl‐α‐tert‐butoxycarbonyllactams in very high chemical (up to 99%) and optical yields (up to 98% ee). Our new catalytic systems provide attractive synthetic methods for pyrrolidine‐ and piperidine‐based alkaloids and chiral intermediates with β‐quaternary carbon centers.     

Organosoluble and light‐colored fluorinated polyimides based on 1,1‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy)phenyl]‐1‐phenylethane and various aromatic dianhydrides

To investigate the CF₃ group affecting the coloration and solubility of polyimides (PI), a novel fluorinated diamine 1,1‐bis[4‐(4‐amino‐2‐ trifluoromethylphenoxy)phenyl]‐1‐phenylethane (2) was prepared from 1,1‐ bis(4‐hydrophenyl)‐1‐phenylethan and 2‐chloro‐5‐nitrobenzotrifluoride. A series of light‐colored and soluble PI 5 were synthesized from 2 and various aromatic dianhydrides 3a–f using a standard two‐stage process with thermal 5a– f(H) and chemical 5a–f(C) imidization of poly(amic acid). The 5 series had inherent viscosities ranging from 0.55 to 0.98 dL/g. Most of 5a–f(H) were soluble in amide‐type solvents, such as N‐methyl‐2‐pyrrolidone (NMP), N,N‐ dimethylacetamide (DMAc), and N,N‐dimethylformamide (DMF), and even soluble in less polar solvents, such as m‐Cresol, Py, Dioxane, THF, and CH₂Cl₂, and the 5(C) series was soluble in all solvents. The GPC data of the 5a–f(C) indicated that the Mn and Mw values were in the range of 5.5–8.7 × 10⁴ and 8.5–10.6 × 10⁴, respectively, and the polydispersity index (PDI) Mw /Mn values were 1.2–1.5. The PI 5 series had excellent mechanical properties. The glass transition temperatures of the 5 series were in the range of 232–276°C, and the 10% weight loss temperatures were at 505–548 °C in nitrogen and 508–532 °C in air, respectively. They left more than 56% char yield at 800°C in nitrogen. These films had cutoff wavelengths between 356.5–411.5 nm, the b* values ranged from 5.0–71.1, the dielectric constants, were 3.11–3.43 (1MHz) and the moisture absorptions were in the range of 011–0.40%. Comparing 5 containing the analogous PI 6 series based on 1,1‐bis[4‐(4‐aminophenoxy)phenyl]‐1‐ phenylethane (BAPPE), the 5 series with the CF₃ group showed lower color intensity, dielectric constants, and better solubility. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2399–2412, 2005     

A new atom transfer radical polymerization initiator based on phenolphthalein for the synthesis of bis‐allyloxy functionalized polystyrene macromonomers

A new atom transfer radical polymerization (ATRP) initiator, namely 2‐(1,1‐bis(4‐(allyloxy)phenyl)‐3‐oxoisoindolin‐2‐yl)ethyl 2‐bromo‐2‐methylpropanoate, was synthesized starting from phenolphthalein, a commercially available and an inexpensive chemical. Well‐ defined bis‐allyloxy functionalized polystyrene macromonomers (M_n,GPC 4800–11 700 g mol^?1) with controlled molecular weight and narrow molecular weight distribution (1.05–1.09) were synthesized using ATRP by varying the monomer to initiator feed ratio. The presence of allyloxy functionality on polystyrene was confirmed by Fourier transform infrared and ¹H NMR spectroscopy. A kinetic study of polymerization revealed pseudo‐first‐order kinetics with respect to monomer consumption. Initiator efficiency was found to be in the range 0.80–0.95. Matrix‐assisted laser desorption ionization time of flight spectra showed a narrow molecular weight distribution with control over the molecular weight. The reactivity of the allyloxy groups on polystyrene was successfully demonstrated by quantitative photochemical thiol‐ene click reaction with benzyl mercaptan as the model thiol reagent. Furthermore, the thiol‐ene click reaction was exploited to introduce other reactive functional groups such as hydroxyl and carboxyl by reaction of α,α′‐bis‐allyloxy functionalized polystyrene with 2‐mercaptoethanol and 3‐mercaptopropionic acid, respectively. © 2014 Society of Chemical Industry     

Synthesis and characterization of novel polyaspartimides derived from 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl and various diamines

A novel bismaleimide, 2,2′‐dimethyl‐4,4′‐bis(4‐maleimidophenoxy)biphenyl, containing noncoplanar 2,2′‐dimethylbiphenylene and flexible ether units in the polymer backbone was synthesized from 2,2′‐dimethyl‐4,4′‐bis(4‐aminophenoxy)biphenyl with maleic anhydride. The bismaleimide was reacted with 11 diamines using m‐cresol as a solvent and glacial acetic acid as a catalyst to produce novel polyaspartimides. Polymers were identified by elemental analysis and infrared spectroscopy, and characterized by solubility test, X‐ray diffraction, and thermal analysis (differential scanning calorimetry and thermogravimetric analysis). The inherent viscosities of the polymers varied from 0.22 to 0.48 dL g⁻¹ in concentration of 1.0 g dL⁻¹ of N,N‐dimethylformamide. All polymers are soluble in N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethylsulfoxide, pyridine, m‐cresol, and tetrahydrofuran. The polymers, except PASI‐4, had moderate glass transition temperature in the range of 188°–226°C and good thermo‐oxidative stability, losing 10% mass in the range of 375°–426°C in air and 357°–415°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 279–286, 1999     

New photosensitive poly(amid‐imide)s containing chalcone moiety and hydantoin derivatives in the main chain: Synthesis and characterization

Six new poly(amid‐imide)s containing chalchone and hydantoin moieties in the main chain were synthesized through the polycondensation reaction of 1,3‐bis[4,4′‐bis(trimellityimido)phenyl]‐2‐propenone 6 with six hydantoin derivatives 7a‐f in a medium consisting of triphenyl phosphite, calcium chloride, pyridine, and N‐methyl‐2‐pyrrolidone. The polycondensation reaction produced a series of novel poly(amid‐imide)s 8a‐f in high yields with inherent viscosities between 0.26 and 0.42 dL/g. The resulting polymers were characterized by elemental analysis, viscosity measurements, solubility test, thermo gravimetric analysis (TGA and DTG), FTIR, and UV‐Vis spectroscopy. 1,3‐bis[4,4′‐bis(trimellityimido)phenyl]‐2‐propenone 6 was prepared from a three‐step reaction by using 4‐nitro benzaldehyde 1 and 4‐nitro acetophenone 2 as precursors. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ring‐opening polymerization of ε‐caprolactone by a new yttrium complex: Y[2,2′‐ethylidene‐bis(4,6‐di‐tert‐butylphenoxy)]2(ethylene glycol dimethyl ether)Na(ethylene glycol dimethyl ether)3

The main aims of the work reported here were to synthesize and characterize a new 2,2′‐ethylidene‐bis(4,6‐di‐tert‐butylphenol) (EDBPH₂)‐based bimetal yttrium complex, Y(EDBP)₂(DME)Na(DME)₃ (1c; where DME is ethylene glycol dimethyl ether), which was employed as an efficient initiator for the ring‐opening polymerization of ε‐caprolactone (ε‐CL). From single‐crystal X‐ray diffraction, the solid structure of this new bimetal initiator was well established. Experimental results show that 1c initiates the ring‐opening polymerization of ε‐CL to afford poly(ε‐CL) with a narrow molecular weight distribution (M_w/M_n = 1.09–1.36, 65 °C). Based on an in situ NMR study, a plausible coordination–insertion mechanism is then proposed. The bimetal complex 1c can be used as an initiator for the ring‐opening polymerization of ε‐CL with some living characteristics. A study of the mechanism reveals that DME displacement in 1c by ε‐CL is involved in the initiation process and the propagation may proceed through three pathways by Na? O insertion or Y? O insertion. Copyright © 2009 Society of Chemical Industry     

Synthesis and polymerizations of novel bisphosphonate‐containing methacrylates derived from alkyl α‐hydroxymethacrylates

The synthesis and polymerizations of four novel bisphosphonate‐containing monomers are reported. The monomers were synthesized from reaction of ethyl and tert‐butyl α‐bromomethacrylates with 3,3‐bis(diethoxyphosphoryl)propanoic acid or with tetraethyl 4‐hydroxybutane‐1,1‐diyldiphosphonate. Their thermal bulk polymerizations, photopolymerizations and copolymerizations with poly(ethylene glycol) methyl ether methacrylate were investigated. The homopolymerizations resulted in polymers with values of 25 000–83 000 g mol^?1; the copolymerizations yielded soluble polymers with 22–34% incorporation of the new monomers; the photopolymerizations gave some structure–reactivity correlation; and one of the homopolymers, upon hydrolysis of its bisphosphonate groups, could interact with hydroxyapatite. © 2013 Society of Chemical Industry     

Highly trans‐1,4‐specific polymerization of 1,3‐butadiene catalyzed by [2,6‐bis{(4S)‐ (−)‐isopropyl‐2‐oxazolin‐2‐yl}pyridine] chromium complex activated with modified methylaluminoxane

Chromium complexes with N,N,N‐tridentate ligands, LCrCl₃ (L = 2,6‐bis{(4S)‐(?)‐isopropyl‐2‐oxazolin‐2‐yl}pyridine ( 1 ), 2,2′:6′,2″‐terpyridine ( 2 ), and 4,4′,4″‐tri‐tert‐butyl‐2,2′:6′,2″‐terpyridine ( 3 )), were prepared. The structures of 1 and 2 were determined by X‐ray crystallography. Upon activation with modified methylaluminoxane (MMAO), 1 catalyzed the polymerization of 1,3‐butadiene, while 2 and 3 was inactive. The obtained poly(1,3‐butadiene) obtained with 1 ‐MMAO was found to have completely trans‐1,4 structure. The 1 ‐MMAO system also showed catalytic activity for the polymerization of isoprene to give polyisoprene with trans‐1,4 (68%) and cis‐1,4 (32%) structure. Copyright © 2011 Society of Chemical Industry     

Synthesis,Crystal Structure,and Thermal Behaviors of 3‐Nitro‐1,5‐bis(4,4′‐dimethylazide)‐1,2,3‐triazolyl‐3‐azapentane (NDTAP)

The energetic material, 3‐nitro‐1,5‐bis(4,4′‐dimethyl azide)‐1,2,3‐triazolyl‐3‐azapentane (NDTAP), was firstly synthesized by means of Click Chemistry using 1,5‐diazido‐3‐nitrazapentane as main material. The structure of NDTAP was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy; mass spectrometry, and elemental analysis. The crystal structure of NDTAP was determined by X‐ray diffraction. It belongs to monoclinic system, space group C2/c with crystal parameters a=1.7285(8) nm, b=0.6061(3) nm, c=1.6712(8) nm, β=104.846(8)°, V=1.6924(13) nm³, Z=8, μ=0.109 mm⁻¹, F(000)=752, and D_c=1.422 g cm⁻³. The thermal behavior and non‐isothermal decomposition kinetics of NDTAP were studied with DSC and TG‐DTG methods. The self‐accelerating decomposition temperature and critical temperature of thermal explosion are 195.5 and 208.2 °C, respectively. NDTAP presents good thermal stability and is insensitive.     

Structural characterization of α‐ and β‐nucleated isotactic polypropylene

Modification of isotactic polypropylene (iPP) with two nucleation agents, namely 1,3:24‐bis(3,4‐dimethylobenzylideno) sorbitol (DMDBS) (α‐nucleator) and N, N′‐dicyclohexylo‐2,6‐naphthaleno dicarboxy amide (NJ) (β‐nucleator), leads to significant changes of the structure, morphology and properties. Both nucleating agents cause an increase in the crystallization temperature. The efficiency determined in a self‐nucleation test is 73.4 % for DMDBS and 55.9 % for NJ. The modification with NJ induces the creation of the hexagonal β‐form of iPP. The addition of DMDBS lowers the haze of iPP while the presence of NJ increases the haze. Copyright © 2004 Society of Chemical Industry     

Synthesis of ω‐amino‐α‐phenylcarbonate alkanes and their polymerization to [n]‐polyurethanes

Aliphatic [n]‐polyurethanes have recently been synthesized from ω‐isocyanato‐α‐alkanols or, more traditionally, by cationic ring‐opening polymerization of cyclourethanes or by the Bu₂Sn(OMe)₂‐promoted polycondensation of ω‐hydroxy‐α‐O‐phenylurethane alkanes. For the latter procedures, the conditions employed do not seem to be suitable for highly functionalized monomers. In contrast, the polymerization of ω‐amino‐α‐phenylcarbonate alkanes is expected to occur under milder conditions. ω‐Amino‐α‐phenylcarbonate alkanes have been synthesized from 6‐aminohexanol (1) and 3‐aminopropanol (6). The procedure involves the N‐Boc protection of the amino group, followed by activation of the alcohol. Removal of the N‐Boc affords the corresponding ω‐amino‐1‐O‐phenyloxycarbonyloxyalkane hydrochlorides. Other oligomeric comonomers between 1 and 6 have been prepared. The polymerization of these precursors takes place in the absence of metal catalysts to afford the corresponding linear and regioregular [n]‐polyurethanes. The procedure described is useful for the preparation of stable ω‐amino‐α‐phenylcarbonate alkane derivatives, which possess varied chain lengths between the terminal functions. These monomers yield [n]‐polyurethanes having various structures starting from just two aminoalkanols. The polyurethanes were obtained in high yields, with reasonable molecular weight and polydispersity values, and they were characterized spectroscopically and thermally. These studies reveal constitutionally uniform structures that are free of carbonate or urea linkages. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of new cardo poly(ether imide)s derived from 9,9‐bis [4‐(4‐aminophenoxy)phenyl]xanthene

A series of new cardo poly(ether imide)s bearing flexible ether and bulky xanthene pendant groups was prepared from 9,9‐bis[4‐(4‐aminophenoxy)phenyl]xanthene with six commercially available aromatic tetracarboxylic dianhydrides in N,N‐dimethylacetamide (DMAc) via the poly(amic acid) precursors and subsequent thermal or chemical imidization. The intermediate poly(amic acid)s had inherent viscosities between 0.83 and 1.28 dL/g, could be cast from DMAc solutions and thermally converted into transparent, flexible, and tough poly(ether imide) films which were further characterized by X‐ray and mechanical analysis. All of the poly(ether imide)s were amorphous and their films exhibited tensile strengths of 89–108 MPa, elongations at break of 7–9%, and initial moduli of 2.12–2.65 GPa. Three poly(ether imide)s derived from 4,4′‐oxydiphthalic anhydride, 4,4′‐sulfonyldiphthalic anhydride, and 2,2‐bis(3,4‐dicarboxyphenyl))hexafluoropropane anhydride, respectively, exhibited excellent solubility in various solvents such as DMAc, N,N‐dimethylformamide, N‐methyl‐2‐pyrrolidinone, pyridine, and even in tetrahydrofuran at room temperature. The resulting poly(ether imide)s with glass transition temperatures between 286 and 335°C had initial decomposition temperatures above 500°C, 10% weight loss temperatures ranging from 551 to 575°C in nitrogen and 547 to 570°C in air, and char yields of 53–64% at 800°C in nitrogen. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and properties of polyamides based on 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐hexahydro‐4,7‐methanoindan

A new diamine 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐hexahydro‐4,7‐methanoindan ( 3 ) was prepared through the nucleophilic displacement of 5,5′‐bis(4‐hydroxylphenyl)‐hexahydro‐4,7‐methanoindan ( 1 ) with p‐halonitrobenzene in the presence of K₂CO₃ in N,N‐dimethylformamide (DMF), followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of new polyamides were synthesized by the direct polycondensation of diamine 3 with various aromatic dicarboxylic acids. The polymers were obtained in quantitative yields with inherent viscosities of 0.76–1.02 dl g⁻¹. All the polymers were soluble in aprotic dipolar solvents such as N,N‐dimethylacetamide (DMAc) and N‐methyl‐2‐pyrrolidone (NMP), and could be solution cast into transparent, flexible and tough films. The glass transition temperatures of the polyamides were in the range 245–282 °C; their 10% weight loss temperatures were above 468 °C in nitrogen and above 465 °C in air. © 2000 Society of Chemical Industry     

Facile synthesis and characterization of star‐shaped polystyrene: self‐condensing atom transfer radical copolymerization of N‐[4‐(α‐bromoisobutyryloxy)phenyl]maleimide and styrene

BACKGROUND: Generation of stars around in situ formed cores provides a facile approach to star‐shaped polymers. Therefore the self‐condensing atom transfer radical copolymerization (SCATRCP) of N‐[4‐(α‐bromoisobutyryloxy)phenyl]maleimide (BiBPM) and a large excess of styrene (St) was investigated. RESULTS: BiBPM and St formed a charge transfer complex (CTC), which underwent the SCATRCP, leading to the branched core initiating the atom transfer radical polymerization of St, finally giving star‐shaped polystyrene (PS). Kinetic and structural study showed that a higher dosage of BiBPM resulted in an enhanced polymerization rate, a higher degree of branching and a larger number of short PS arms. Differential scanning calorimetry suggested that the glass transition temperature of the star‐shaped PS decreased with molecular weight. Melt rheometry showed that even a slightly branched architecture of the PS led to a significantly lower viscosity; both the melt flow index and the activation energy increased with the degree of branching. CONCLUSION: Due to the preferential consumption of BiBPM and formation of a CTC, even a very low dosage of BiBPM could lead to star‐shaped PS, which, in comparison with linear analogues, could possess much better melt fluidity. Copyright © 2008 Society of Chemical Industry     

Copolymerization of ethylene/α‐olefins over (2‐MeInd)2ZrCl2/MAO and (2‐BzInd)2ZrCl2/MAO systems

Ethylene homopolymerization and ethylene/α‐olefin copolymerization were carried out using unbridged and 2‐alkyl substituted bis(indenyl)zirconium dichloride complexes such as (2‐MeInd)₂ZrCl₂ and (2‐BzInd)₂ZrCl₂. Various concentrations of 1‐hexene, 1‐dodecene, and 1‐octadecene were used in order to find the effect of chain length of α‐olefins on the copolymerization behavior. In ethylene homopolymerization, catalytic activity increased at higher polymerization temperature, and (2‐MeInd)₂ZrCl₂ showed higher activity than (2‐BzInd)₂ZrCl₂. The increase of catalytic activity with addition of comonomer (the synergistic effect) was not observed except in the case of ethylene/1‐hexene copolymerization at 40°C. The monomer reactivity ratios of ethylene increased with the decrease of polymerization temperature, while those of α‐olefin showed the reverse trend. The two catalysts showed similar copolymerization reactivity ratios. (2‐MeInd)₂ZrCl₂ produced the copolymer with higher M_w than (2‐BzInd)₂ZrCl₂. The melting temperature and the crystallinity decreased drastically with the increase of the α‐olefin content but T_m as a function of weight fraction of the α‐olefins showed similar decreasing behavior. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 928–937, 2000     

Synthesis of novel azo‐containing polyureas derived from 4‐[4′‐(2‐hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione

4‐[4′‐(2‐Hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione ( HNAPTD ) ( 1 ) has been reacted with excess amount of n‐propylisocyanate in DMF (N,N‐dimethylformamide) solution at room temperature. The reaction proceeded with high yield, and involved reaction of both N? H of the urazole group. The resulting bis‐urea derivative 2 was characterized by IR, ¹H‐NMR, elemental analysis, UV‐Vis spectra, and it was finally used as a model compound for the polymerization reaction. Solution polycondensation reactions of monomer 1 with Hexamethylene diisocyanate ( HMDI ) and isophorone diisocyanate ( IPDI ) were performed in DMF in the presence of pyridine as a catalyst and lead to the formation of novel aliphatic azo‐containing polyurea dyes, which are soluble in polar solvents. The polymerization reaction with tolylene‐2,4‐diisocyanate ( TDI ) gave novel aromatic polyurea dye, which is insoluble in most organic solvents. These novel polyureas have inherent viscosities in a range of 0.15–0.22 g dL^?1 in DMF at 25°C. Some structural characterization and physical properties of these novel polymers are reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3177–3183, 2001     

Bis(3,5‐dimethylphenyl)‐(S)‐pyrrolidin‐2‐ylmethanol: an Improved Organocatalyst for the Asymmetric Epoxidation of α,β‐Enones

The asymmetric epoxidation of α,β‐enones by the readily available bis(3,5‐dimethylphenyl)‐(S)‐pyrrolidin‐2‐ylmethanol and tert‐butyl hydroperoxide (TBHP) is described. Stereoelectronic substitution on the aryl moiety of diaryl‐2‐pyrrolidinemethanols was found to significantly affect the efficiency with respect to the previously reported (S)‐diphenyl‐2‐pyrrolidinemethanol. Improved reactivity and enantioselectivity were achieved with bis(3,5‐dimethylphenyl)‐(S)‐pyrrolidin‐2‐ylmethanol at reduced catalyst loading (20 mol %) with ees up to 94% for chalcone epoxides under mild reaction conditions, whereas (S)‐diphenyl‐2‐pyrrolidinemethanol afforded a maximum ee of 80%. Interestingly, the methodology is applicable to the epoxidation of more challenging aliphatic or enolizable enones with good control of the asymmetric induction (up to 87% ee).