Structures of polyethylene and copolymers of ethylene with 1-octene and oligoethylene produced with the Cp2ZrCl2 and [(C5Me4)SiMe2N(t-Bu)]TiCl2 catalysts

Polymerization of ethylene and copolymerizations of ethylene with 1-octene and oligoethylene having a vinyl end group were conducted with Cp₂ZrCl₂ and [(C₅Me₄)SiMe₂N(t-Bu)]TiCl₂^a as catalysts, and the structures of the resulting polymers were analyzed in detail. The Cp₂ZrCl₂ catalyst combined with methylalumoxane (MAO) gives polyethylene with vinyl, vinylidene and trans-vinylene groups. The use of Al(iC₄H₉)₃/(C₆H₅)₃C · B(C₆F₅)₄ as cocatalyst produces polyethylene predominantly containing trans-vinylene groups. Polyethylene with vinyl end groups was obtained selectively with [(C₅Me₄)SiMe₂N(t-Bu)]TiCl₂ MAO as catalyst. The types and contents of CC double bonds in polyethylene markedly depend upon the metallocene compound as well as as the cocatalyst. In the copolymerizations the [(C₅Me₄)SiMe₂N(t-Bu)]TiCl₂ MAO catalyst system, on the other hand, gives poly[ethylene-co-(1-octene)] with a high content of 1-octene and a polyethylene containing an appreciable amount of long-side-chain oligoethylene.     

Investigation of sequences in a poly(butadiene-co-trimethylvinylsilane) by metathesis degradation

Poly(butadiene-co-trimethylvinylsilane) with a mole fraction of 13% trimethylvinylsilane was prepared with butyllithium as initiator. It was degraded by cross-metathesis with (E)-4-octene or (Z)-2-butene in the presence of the catalyst WCl₆/Sn(CH₃)₄. The mixtures of the degradation products were investigated by means of gas chromatography (GC)/mass spectrometry (MS) coupling; mass spectra of degradation products with 4-octene are depicted and discussed. Sequences of up to six trimethylvinylsilane units inserted between 1,4-linked butadiene were identified after degradation with 2-butene. Trimethylvinylsilane inserted between 1,4- and 1,2-linked butadiene was also found. Cyclohexenyl and cyclopentenyl compounds were the preferred cyclic metathesis products.     

Reaktion an Ziegler-Natta-Katalysatoren, 12. Anwendung der Olefin-Metathese zum Nachweis einer radikalischen Aralkylierung von 1,4-Polybutadien

1,4-Polybutadiene was partially aralkylated with alkylbenzenes (toluene, ethylbenzene, o-, m- and p-xylene, mesitylene) and dicumyl peroxide in a radical reaction. The resulting polymers were investigated by IR spectroscopy and degradated in a metathesis reaction with 4-octene using a WCl₆/Sn(CH₃)₄ catalyst. The low molecular weight degradation products with aralkyl substituents were separated by gas chromatography and identified by mass spectrometry.     

Estergruppenhaltige Polyalkenylene durch Olefin-Metathese

The ring-opening polymerisation of ester group-substituted cycloolefines leads to linear polyalkenylenes with pendant ester groups in the presense of suitable metathesis-catalysts like WCl₆/(CH₃)₄Sn. The monomers 9-ethoxycarbonyl-bicyclo[6.1.0]non-cis-4-ene ( 3 ), 13-ethoxycarbonyl-bicyclo[10.1.0]trideca-trans-4, trans-8-diene ( 5 ) and 3-ethoxycarbonyl-tricyclo[3.2.1.0^2,4]oct-6-ene ( 7 ) are obtained from the cycloolefines cis-1, cis-5-cyclooctadiene ( 2 ), cis-1, trans-5, trans-9-cyclododecatriene ( 4 ) and norbornadiene ( 6 ) via carbene reaction with ethyl diazoacetate. The corresponding polyalkenylenes ( 3a, 5a and 7a ) show relatively high molecular weights. Their constitutions are determined spectroscopically and by gaschromatographic analysis of the degradation products after olefin-metathesis with a low molecular weight olefine (4-octene).     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 9. Radical Coupling Reaction of 1,1‐Diphenylethylene‐Functionalized Polymers with Potassium Naphthalenide and Its Application to Syntheses of In‐Chain‐Functionalized Polymers and Star‐Branched Polymers

Radical coupling reactions of both 1,1‐diphenylethylene (DPE)‐chain‐end‐ and DPE‐in‐chain‐functionalized polymers with potassium naphthalenide have been studied under the conditions mainly in THF at –78°C. Chain‐end‐functionalized polymers having M̄_n values of less than 10 kg/mol were very efficiently coupled in more than 90% yield to afford the polymeric dianion that were dimeric coupled products with two 1,1‐diphenylalkyl anions in the middle of the chains. However, the dimer yield decreased with increasing the molecular weight. The dimer was obtained in 59% yield with use of the chain‐end‐functionalized polymer having M̄_n of 33.9 kg/mol. Well‐defined in‐chain‐functionalized polymers with two benzyl bromide and DPE moieties each have been successfully synthesized by the reaction of the polymeric dianion thus obtained with 1‐(4‐bromobutyl)‐4‐(tert‐butyldimethylsilyloxymethyl)benzene and 1‐[4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene, respectively. The radical coupling reaction of in‐chain‐functionalized polymers with DPE (M̄_n ca. 20 kg/mol) with potassium naphthalenide also proceeded efficiently to afford the coupled products that were A₂A′₂ and A₂B₂ four‐arm star‐branched polymers with well‐defined structures (M̄_n ca. 40 kg/mol).     

Reaktion an ziegler-natta-katalysatoren, 16. Metathese-abbau von polybutadien-derivaten mit sauerstoff bzw. schwefel enthaltenden Substituenten

Methylene groups of 1,4-polybutadiene were partially brominated with N-bromosuccinimide. A subsequent Grignard-Wurtz-reaction with 4-methoxyphenyl-, 3,4-dimethoxyphenyl-, and 2-thienylmagnesium bromide resulted in an exchange of the bromine atoms for 4-methoxyphenyl, 3,4-dimethoxyphenyl and 2-thienyl groups. Another type of modification was the reaction of 1,4-polybutadiene with 4-methoxytoluene and o-resp: p-toluic acid methylester in the presence of dicumyl peroxide. Thereby 4-methoxyphenylmethyl and 2- resp. 4-methoxycarbonylphenylmethyl groups were introduced into the polymer. The modified polymers were investigated by IR-spectroscopy and degraded by olefin metathesis with 4-octene using a WCl₆/Sn(CH₃)₄ catalyst. The degradation products were separated by gas chromatography and identified by mass spectrometry.     

Functionalized polyacetals, 1. Copolymerization of trioxane with 1,3-dioxep-5-ene and properties of the resulting copolymer

1,3,5-Trioxane ( 1 ) and 1,3-dioxep-5-ene ( 2 ) were copolymerized with BF₃OEt₂ at 65°C. The products, after base hydrolysis, were characterized by ¹³C and ¹H NMR and were found to assume the chemical structure 4 of a copolymer containing oxymethylene and oxy-2-butenylene units with 4-hydroxy-2-butenyl and methoxy end groups, with the ratio of hydroxy-2-butenylene to methoxy end groups varying with experimental conditions. The copolymer demonstrates crystallinity and thermal stability comparable to poly(trioxane-co-ethylene oxide)s. Copolymer melting point was observed to decrease with increasing comonomer incorporation. The upper limit for incorporation of the comonomer 2 was found to be ca. 4 mol per cent. Viscosity and end group analysis (by ¹H NMR) indicate molecular weights in the range of 10⁴ to 10⁵. The comonomeric unit demonstrates the ability to act as both a stopper against unzipping and as a trap for certain degrading agents.     

Metathesis degradation of polymers obtained by grignard-wurtz reaction of partially α-brominated 1,4-polybutadiene

1,4-Polybutadiene was partially brominated at the methylene groups with N-bromosuccinimide. Then, by means of Grignard-Wurtz reactions, the following substituents were introduced: isopropyl, butyl, pentyl, cyclohexyl, phenyl, 4-methylphenyl, 4-ethylphenyl, 3,4-dimethylphenyl, 4-isopropylphenyl, 4-fluorophenyl, 3-trifluorophenylmethyl, 4-chlorophenyl, benzyl, 2-methylbenzyl, and 4-methylbenzyl. The modified polymers (ca. 20% of the units substituted) were degraded to low molecular products with E-4-octene in the presence of the catalyst WCl₆/(CH₃)₄Sn. The degradation products were separated by gas chromatography and identified by mass spectrometry. Isomeric substituents, isomeric units, and isomeric segments in the polymers could be distinguished. — In Grignard-Wurtz reactions, transfer reactions with toluene as solvent and simultaneous reactions with two Grignard reagents (4-methylphenyl and 4-methylbenzyl compounds) were also investigated.     

Metathesis degradation of partially cyclopropanated 1,4-polybutadiene: Consideration of side reactions in the calculation of block size distribution

(Z)-1,4-Polybutadiene was partially cyclopropanated with bis(iodomethyl)zinc and the polymer was degraded with (E)-4-octene in the presence of WCl₆/(CH₃)₄Sn as catalyst. The products were identified by gas chromatography/mass spectrometry and determined by gas chromatography. The block size distribution in the partially cyclopropanated polymer was calculated from these products. A method is described by which the decrease in yield of the modified degradation products, caused by side reactions during the olefin metathesis, can be taken into account in this calculation. It is concluded that under the given experimental conditions the block size distribution is random.     

Metathesis degradation of poly(butadiene-alt-propene)

Poly(butadiene-alt-propene) ( 1 ) was degraded by metathesis reaction using symmetric olefins (3-hexene and 4-octene) in chlorobenzene solution in the presence of WCl₆/(CH₃)₄Sn as catalyst. Identification of the degradation products by means of a combination of gas chromatography (GC) and mass spectrometry (MS) revealed small amounts of “defects” in the almost ideally alternating copolymer 1 . These were non-alternating sequences of 2-butenylene and methylethylene units, vinylethylene units and branching points. In addition, the metathesis degradation of 1 with 4 -octene was investigated kinetically between 15 and 40°C. The measurements confirm that the thermodynamically stable 4-methylcyclohexene is the final product. This can be formed directly from the polymer and via oligomeric products. The formation of these intermediates is preceded by an induction period. Their concentrations pass maxima, the positions of which depend on the size of the molecules and on the temperature.     

Star polymers and block copolymers of 2-oxazolines using chloroformates as initiators

Polyfunctional chloroformates were applied to the polymerization of 2-phenyl-2-oxazoline and 2-methyl-2-oxazoline. The use of a trifunctional initiator, viz. the chloroformate of 2,2-bis(hydroxymethyl)-1-butanol, led to three-arm star polymers of 2-oxazolines. Two macromolecular initiators, viz. poly(ethylene oxide) with two chloroformate end groups (α-chloroformyl-ω-chloroformyloxypoly(oxyethylene)) with number-average molar masses 350 g/mol ≤ M?_n ≤ 6000 g/mol and α-chloroformyl-ω-methoxypoly(oxyethylene) with M?_n = 350 and 750 g/mol were applied for the synthesis of poly(2-oxazoline)-block-poly(ethylene oxide)-block-poly(2-oxazoline) and poly(2-oxazoline)-block-poly(ethylene oxide) copolymers, respectively.     

Reaktion an Ziegler-Natta-Katalysatoren, 14. Anwendung der Olefin-Metathese zum Nachweis einer Grignard-Wurtz-reaktion an hydrobromiertem 1,4-Polybutadien

1,4-Polybutadiene was partially hydrobrominated in the presence of AlBr₃. A Grignard-Wurtz-reaction with phenylmagnesium bromide resulted in an exchange of the bromine atoms for phenyl groups. The polymers were degraded in an olefin metathesis reaction with 4-octene using a WCl₆/Sn(CH₃)₄ catalyst. The low molecular degradation products with bromine or phenyl substituents, resp., were separated by gas chromatography and identified by mass spectrometry.     

UV-photometrisch bestimmte relative molare massen von anionisch erzeugten polyäthylenoxiden mit unterschiedlichen endgruppen

Ethylene oxide was polymerized with potassium 4-(phenylazo)benzylalcoholate ( 1f ). The purified and fractionated products were acylated. The ultra-violet measurement of the end groups showed a large excess of hydroxyl end groups compared with the initiator end groups. Number average molecular weights (M?_n) could be derived from the content of the different end groups. The comparison with osmotically determined M?_n-values and viscosity average molecular weights (M?_η) confirms the supposed structure of polyethylene oxide.     

Linear Addition Polymers and Cyclic Oligomers of N,N‐Diglycidyl Aniline and Amines. Uncrosslinked Epoxide–Amine Addition Polymers, 46

The addition polymerization of N,N‐diglycidyl aniline (DGA) and disecondary diamines leads to linear addition polymers with molecular weights ranging from 2 500 to 9 100 Da respectively. Their relatively broad molecular weight distribution (M̄_w /M̄_n = 5.5 to 17) is caused by the formation of small amounts of cyclic oligomers. Surprisingly, the addition polymerization of primary monoamines and DGA results in the formation of oligomers only. These oligomers have molecular weights between 684 and 1 165 g·mol^–1. ¹³C NMR spectra proof that during addition reaction no side‐reaction took place and that the epoxide end groups were completely consumed. Obviously, the addition products mainly consist of cyclic oligomers. In the MALDI‐TOF mass spectra cyclic oligomers of repeat units between n = 1 and n = 7 were observed. The kinetics of the addition polymerization can be described by both a formal model and the smallest necessary set of elementary reactions. In order to find the optimum parameters, the set of differential equations was solved numerically by multivariate non‐linear regression. The perfect agreement between model calculations and experimental curves allows reliable predictions of the reaction behavior for arbitrary temperature–time profiles.     

Anionic synthesis of well‐defined,poly[(styrene)‐block‐(propylene oxide)] block copolymers

Well‐defined, narrow molecular weight distribution (M_w/M_n ≤ 1.1) poly[(styrene)‐block‐(propylene oxide)] block copolymers with relatively high molecular weight poly(propylene oxide) blocks [e. g. M_n (PPO) = 10 000–12 000 g/mol] have been prepared by anionic polymerization. The polystyrene block (M_n = 5 000; M_w/M_n = 1.1) was prepared by alkyllithium‐initiated polymerization of styrene followed by chain‐end functionalization with ethylene oxide and protonation with acidic methanol. The resulting ω‐hydroxyl‐functionalized polystyrene was converted to the corresponding alkali metal salts with alkali metals (Na/K alloy, Rb, Cs) and then used to initiate block polymerization of propylene oxide in tetrahydrofuran. The effects of crown ethers (18‐crown‐6 and dicyclohexano‐24‐crown‐8) and added dimethylsulfoxide were investigated. Chain transfer to the monomer resulted in significant amounts of poly(propylene oxide) formation (50%); however, the diblock molecular weight distributions were narrow. The highest molecular weight poly(propylene oxide) blocks (12 200 g/mol) were obtained in tetrahydrofuran with cesium as counterion without additives.     

Copolymerization of propene and higher α-olefins with the metallocene catalyst Et[Ind]2HfCl2/methylaluminoxane

Copolymerizations of propene with higher α-olefins including 1-butene, 1-hexene, 1-octene, 1-dodecene and 1-hexadecene were carried out with an isospecific metallocene catalyst (Et[Ind]₂HfCl₂/methylaluminoxane) at 30°C in toluene. ¹³C NMR analysis showed that all products obtained are random copolymers (r₁ · r₂ ～ 1). The reactivity of the higher α-olefins in the copolymerization is surprisingly high and decreases only slightly with increasing length of the olefin. The incorporation rates of the comonomers in this study were found to be much higher than those obtained by the use of heterogeneous Ziegler-Natta catalysts. Hence, copolymers with every desired composition and α-olefin homopolymers can be prepared. The molecular weight of the copolymers is reduced with rising comonomer content. Melting points and glass transition temperatures studied by means of differential scanning calorimetry show a decrease with rising comonomer content and increasing length of the α-olefin.     

Polymerization of Vinyl Acetate Initiated with Di‐tert‐butyl Perfumarate

The polymerization behavior of vinyl acetate ( 2 ) was studied in benzene using di‐tert‐butyl perfumarate ( 1 ) as an initiator. Low molecular weight polymer (M̄_n ≈ 3 000) is formed in the early stage of polymerization where 1 is substantially consumed by thermal decomposition, copolymerization with 2 , and chain transfer reactions through an addition‐substitution mechanism. As a result, the low molecular weight polymer formed in the early stage of polymerization contains five peroxy ester groups per polymer molecule. Then, the polymerization of 2 initiated with the low molecular weight polymer further proceeds to yield high molecular weight poly( 2 ) (M̄_n = 2.5–23×10⁴). Decomposition of the peroxy ester group of 1 in benzene was studied in the absence and in the presence of methyl methacrylate (MMA) or 2 . The activation energy of decomposition of the peroxy ester group of 1 is 118 kJ/mol in the absence of the monomers. The decomposition of the peroxy ester group of 1 is highly accelerated in the presence of MMA. The peroxy ester groups derived from 1 decompose in two stages in the presence of 2 . In the first stage, some of them are rapidly consumed mainly by the chain transfer reaction. In the second stage, the peroxy ester groups of copolymer from 1 and 2 decompose slowly.     

Bildung von Cyclopentenylverbindungen beim Metathese-Abbau von modifiziertem 1,4-Polybutadien

This investigation deals with metathesis degradation products of modified 1,4-polybutadiene (poly(1-butenylene)) which have not been taken into consideration as yet, e.g. substituted cyclopentene and linear isomerization products. Substituents were introduced into 1,4-poly-butadiene either by partial bromination with N-bromosuccinimide followed by a Grignard-Wurtz reaction or by reaction with the corresponding methyl compound and dicumyl peroxide. Polymers with 2-methylbenzyl, 4-methylbenzyl, 4-chlorobenzyl, 4-methoxybenzyl, 2-naphthylmethyl, 2,4,6-trimethylphenyl, 1-naphthyl, 9-anthryl, and 9-phenanthryl substituents were degraded by metathesis with 4-octene using WCl₆/(CH₃)₄Sn as a catalyst and were analyzed by gas chromatography/mass spectrometry and by liquid chromatography.     

Pseudo‐Living Anionic Telomerization of Buta‐1,3‐diene

Low‐molecular‐weight liquid polybutadienes (1 000–2 000 g · mol^?1) consisting of 60 mol‐% poly(buta‐1,2‐diene) repeating units were synthesized via anionic telomerization. Maintaining the initiation and reaction temperature at less than 70 °C minimized chain transfer and enabled the polymerization to occur in a living fashion, which resulted in well‐controlled molecular weights and narrow polydispersity indices. MALDI‐TOF mass spectrometry confirmed that the end groups of liquid polybutadienes synthesized via anionic telomerization contained one benzyl end and one protonated end. In comparison, the end groups of liquid polybutadienes synthesized via living anionic polymerization contained one sec‐butyl or butyl end and one protonated end.

     

Metalloester, 9. Untersuchung des anfangsstadiums der anionischen polymerisation von methylmethacrylat. Reaktion von methyl-2-sodioisobutyrat mit methylmethacrylat

In the reaction of methyl methacrylate ( 2 ) with methyl 2-sodioisobutrate ( 1 ) (a model of the active center in the anionic polymerization of 2 ) in a mole ratio of 2:1, the concentrations of all known initial compounds and reaction products were estimated. This reaction was studied in a flow reactor with reaction times between 0,02 and 1,4 s using GLC, LC and GPC as analytical methods. At the same time, a rise in temperature of the reaction mixture by 6°C was observed (for [ 2 ] = 0,2 mol/1); at a higher concentration of 2 (0,6 mol/1), this rise was 27°C and hence not negligible in the interpretation of the results. The concentration changes of the individual products were in accordance with the concept of a stepwise addition of 2 , to the metalloesters. At the end of the reaction the mean molecular weight of the addition products corresponded roughly to the ratio 2 /effective 1 . The cyclization of Na-trimer 4a to a cyclic trimer 9 was shown to be an important side reaction. The Na-tetramer 5a and the higher Na-oligomers 6a probably undergo a similar cyclization. 2 added 1 very quickly; the following approximate order of reaction rates (Scheme 1) is proposed: R₁ > R₂, R₃, R₄, … > R_c.