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Direct copolymerization of propylene and functional monomers using early transition metal catalysts is a prominent synthesis method to render a functionality to polypropylene maintaining high stere...

The copolymerization of norbornene (NB) and various α-olefins [1-octene (O), 1-decene (De), and 1-dodecene (Do)] was achieved with high activity using (tBuNSiMe2Flu)TiMe2 (1)-[Ph3C][B(C6F5)4] and 2...

Copolymerizations of ethylene with polar monomers such as 5-hexene-1-yl acetate and allyl acetate are explored using nickel complexes bearing a class of anilinonaphthoquinone ligands. High tolerability of this complex toward polar comonomer is achieved by the installation of sterically bulky substituent on the aniline ligand. Moreover, the heterogenization of the nickel complexes using silica-supported modified methylaluminoxane enhances the copolymerization performances. The catalyst is highly active and thermally stabile to give semicrystalline ester-functionalized high molecular weight polyethylenes.

Copolymerizations of norbornene with propylene and 1-octene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe2Flu]TiMe2 (1), [t-BuNSiMe2(3,6-tBu2Flu)]TiMe2 (2), [t-BuNSiMe2(2,7-tBu2Flu)]TiMe2 (3), and [t-BuNSiMe2(C29H36)]TiMe2 (4; C29H36, octamethyloctahydrodibenzofluorenyl), activated by trialkylaluminum-free modified methylaluminoxane. The catalytic systems promoted random copolymerizations in a living manner regardless of the titanium complex used. The activity increased by the introduction of the tBu groups on the Flu ligand, and 4 showed the highest activity for each copolymerization. The comonomer content of the copolymers obtained was controllable in a wide range by changing comonomer feed ratio with these catalytic systems. The linear relationships were observed between the norbornene content and the glass transition temperature of the copolymer, whereas the slopes depended on the titanium complex used. The result suggested that the titanium complexes affect...

Crystalline styrene−butadiene−styrene (SBS) triblock copolymers consisting of elastic cis-polybutadiene (cis-PB) chemically bonded with crystallizable syndiotactic polystyrene (syn-PS) were synthesized through a stereospecific sequential triblock copolymerization of S with B catalyzed by C5Me5TiMe3/B(C6F5)3/trioctylaluminum (Al(oct)3) under controllable polymerization conditions. The first polymerization step was conducted at −25 °C, yielding syn-PS with controllable molecular weight by changing the polymerization time. The second one was started with the addition of excess B to the progressing syn-PS polymerization at −40 °C, yielding syn-PS/cis-PB diblock copolymer with high block efficiencies. The third one was conducted at −25 °C just by removal of the unreacted B in order to enhance the reinsertion and propagation of the remained S, yielding crystalline SBS triblock copolymers with relatively high PS compositions. The livingness of the whole polymerization process was confirmed through a linear incre...

[t-BuNSiMe2(2,7-t-Bu2Flu)]TiMe2 and [t-BuNSiMe2(3,6-t-Bu2Flu)]TiMe2 were synthesized and characterized by elemental analysis, 1H NMR, and single-crystal X-ray analysis. These complexes were applied for propylene polymerization using dried modified methyaluminoxane (dMMAO) as a cocatalyst at 0 and 25 °C. The introduction of tert-butyl substituents to the fluorenyl ligand improved the activity more than 3 times regardless of the position of the substituents. The postpolymerization testified that both catalytic systems conducted the propylene polymerization in a living manner at both 0 and 25 °C. The propagation rate increased linearly against the Al/Ti ratio from the range of 100−400 with keeping the number of polymer chains constant, which directly indicates that a larger amount of dMMAO enhanced the propagation rate. The introduction of tert-butyl substituents also improved the syndiospecificity: the 3,6-position was more effective than the 2,7-position, and [t-BuNSiMe2(3,6-t-Bu2Flu)]TiMe2 gave the livin...

Copolymerization of propene and norbornene (P−N) was conducted with (t-BuNSiMe2Flu)TiMe2 (1) activated by Me3Al-free methylaluminoxane (dried MAO), modified methylaluminoxane (MMAO), and Ph3CB(C6F5)4/Oct3Al at 20 °C under atmospheric pressure of propene. The 1−Ph3CB(C6F5)4/Oct3Al system showed the highest activity and gave the copolymer with the lowest molecular weight and broad molecular weight distribution. The 1−dried MAO system produced the copolymer with the narrowest molecular weight distribution. The detailed investigation of this system clarified that the norbornene content in the copolymer was almost proportional to the N/P feed ratio with a narrow polydispersity of 1.1−1.2 and the glass transition temperatures of the P−N copolymers increased linearly against the norbornene content in the copolymers, that is, 53 °C with 17 mol % of norbornene and 249 °C with 71 mol % of norbornene. The 13C NMR spectra also suggested the random distribution of the comonomers in the copolymers obtained.

Ethene−norbornene (E−N) copolymerizations were carried out by (t-BuNSiMe2Flu)TiMe2 (1) and (t-BuNSiMe2C5Me4)TiMe2 (2) activated with methylaluminoxane (free from Me3Al) under an atmospheric pressure of ethene at 40 °C. 1 showed higher activity than 2. The activity of 1 increased with increasing the feed ratio of norbornene/ethene, but the opposite trend was observed for 2. In the same feed ratio (N/E = 8), the incorporation of norbornene was higher with 1 (N = 50 mol %) than with 2 (N = 38 mol %). The 13C NMR spectrum of the E−N copolymer obtained with 1 was completely different from that with 2. The former showed the resonances of norbornene dyad and triad, whereas the latter showed only those of alternating and isolated norbornene structures. Some new signals were assigned to the rac,rac-NNN triad. The effects of activators and polymerization temperature were investigated with 1 in more detail, and the 1-Ph3CB(C6F5)4/Oct3Al system was found to show the highest activity at 80 °C and gave the E−N copolyme...

The copolymerizations of propylene with allyl monomers carrying alcohol or amine were conducted by the rac-dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane catalyst system. The allyl monomers were pretreated by alkylaluminum before the polymerization. Although the efficiency of the introduction of allyl alcohol-based comonomer was extraordinary low (0.04−0.08 mol % in polymer), the trimethylaluminum-treated allylamine was found to be introduced more effectively (0.65 mol % in polymer). The 13C NMR study indicated that the position of allylamine unit in the copolymer was influenced by the kind of alkylaluminum used at the polymerization. In the presence of trimethylaluminum, the terminally aminated polypropylene was obtained ([amino end polymer]/[whole polymer] = 0.83). In the presence of triisobutylaluminum, however, the allylamine unit is located both on the main chain and at the chain end. The end-aminated polymer was probably obtained due to the formation of dormant species after the i...

Formation of intensity gratings was studied with two s-polarized (s+s) writing beams in polymer liquid crystals (PLCs) containing a photochromic moiety (azobenzene) and a mesogenic unit (tolane, T-AB; cyanobiphenyl, CB-AB) by means of photoinduced change in alignment of PLCs. Remarkable differences were observed between these two PLCs. T-AB showed higher values of the diffraction efficiency (η) and a faster response than CB-AB. In photoinduced alignment behavior of the PLCs, T-AB exhibited a faster change in alignment than CB-AB with the value of η about 30% in the Raman−Nath regime and the maximum value for modulation of the refractive index (Δn‘) of about 0.08. It was revealed that η and Δn‘ are dependent on the structure of the mesogenic unit. In addition, we attempted the holographic image storage of three-dimensional (3-D) objects in the T-AB films. The 3-D object was reconstructed with high resolution (>5000 lines/mm).

Propene polymerization was conducted at 0 °C by [t-BuNSiMe2Flu]TiMe2 combined with B(C6F5)3, MAO, or the MAO which had been dried in a vacuum and washed with hexane before use. The effect of cocata...

Photoinduced alignment behavior in a series of polymer liquid crystals containing different azobenzene moieties in the side chain was investigated. With increase of the strength of donor and acceptor at 4 and 4‘ positions of the azobenzene groups, the possibility of an alignment change in the polymer liquid crystals having the same methacrylic backbone decreased due to the slightly increased enthalpic stability of the mesophase and the significantly decreased concentration of cis-azobenzene, although the cis−trans isomerization rate increased. However, a high alignment efficiency was observed in polymer liquid crystal ACB-ABA6, which contained strong donor−acceptor pairs in the azobenzene moiety and exhibited low stability of mesophase, since both the rate of cis−trans isomerization and the mobility of mesogens are favorable for alignment change. Three different relaxation processes were observed in the aligned polymer liquid crystals.

Polymerization of propene was conducted by [t-BuNSiMe2Flu]TiMe2-based catalysts at −50 °C in the presence of trioctylaluminum. When B(C6F5)3 was used as a cocatalyst, polymer yield monotonically increased with increasing polymerization time. The polypropene obtained showed narrow molecular weight distribution, and the number average molecular weight of the polymer linearly increased against the polymer yield. In addition, the number of polymer chains, which was approximately a half the number of Ti used, was almost constant during the polymerization. The living nature of the [t-BuNSiMe2Flu]TiMe2 catalyst depended on polymerization temperature and cocatalyst. Deactivation occurred at 0 °C or even at −50 °C when Ph3CB(C6F5)4 was used in place of B(C6F5)3. 13C NMR analysis of the polymer indicated that the living polymerization proceeded highly regiospecifically via 1,2-insertion to give syndiotactic-rich polymer. Polymerization of 1-hexene with [t-BuNSiMe2Flu]TiMe2/B(C6F5)3 also proceeded in a living manner...

Polydomain films of liquid crystalline polymer (MACB-AB6) with low content (6 mol %) of azobenzene units were prepared and irradiated with linearly polarized light at 366 nm, thus inducing an alignment of the photochromic side groups as well as the nonphotoactive mesogens, the cyanobiphenyl groups. An induced order parameter, S, was obtained from polarized UV and IR spectroscopy, and it increased with increase in temperature at first and then decreased due to phase transition. The effect of light intensity on the alignment behavior has been investigated in detail. Alignment change can take place even for a low intensity (0.7 mW/cm2) of irradiation light. Irradiation light at high intensity induced alignment as well as a phase transition at relatively low temperature. A higher saturation order parameter and faster achievement of the order parameter were obtained, since a higher concentration of cis-azobenzene was produced when the film was exposed to polarized light with a higher intensity. This is due to ...

Propene polymerization was conducted by a MgCl2/diisobutyl phthalate/TiCl4 catalyst combined with AlEt3 as cocatalyst. The polymerization was quenched by oxygen gas, and the polymer was fractionated into atactic and isotactic parts with boiling heptane. Each part was analyzed by 1H NMR. The spectra showed the resonances of vinylidene, vinyl, and hydroxymethylene groups, whose intensities were strongly dependent on the polymerization temperature and the stereoregularity. Raising the polymerization temperature increased the intensity of the hydroxymethylene group in both parts. The relative intensity of the hydroxymethylene to that of the vinylidene group was much higher in the atactic parts. These results suggest that the rates of β-hydrogen transfer and transfer by AlEt3 should be affected by the stereospecificity of the active species as well as polymerization conditions. Heat treatment at 120 °C in the presence of 1-octene quantitatively converted the terminal aluminum−carbon bond to a vinylidene group.

Polymerization of methyl methacrylate (MMA) was conducted with the catalyst systems of rac-Et(Ind) 2 Zr(CH 3 ) 2 /Ph 3 CB(C 6 F 5 ) 4 , rac-Et(IndH 4 ) 2 Zr(CH 3 ) 2 /Ph 3 CB(C 6 F 5 ) 4 , and rac-Me 2 Si(Ind) 2 Zr(CH 5 ) 2 /Ph 3 CB(C 6 F 5 ) 4 . These catalysts only were found to be inactive. However, the addition of suitable Lewis acids like alkylzinc and alkylaluminum compounds gave highly isotactic PMMA. The isotactic pentad [mmmm] in PMMA as well as the propagation rate constant (k p ) depended significantly upon the zirconocene compounds. Both the microstructure ([mmmm]) and propagation rate constant (k p ) increased in the following order. Me 2 Si(Ind) 2 CH 2 CH 3 > (CH 2 ) 3 CH 3 . When the polymerization was initiated by the rac-Et(Ind) 2 Zr(CH 3 ) 2 /Ph 3 CB(C 6 F 5 ) 4 /Zn(C 2 H 4 CH=CH 2 ) 2 catalyst system at 0°C in toluene, the molecular weight of PMMA increased in proportion to the conversion of MMA. The increase of temperature from 0 to 80°C caused a decrease in isotactic pentad content by approximately 10%. The isotactic polymerization of MMA was revealed to proceed by an enantiomorphic site-controlled mechanism

Bis(3-butenyl)zinc (BBZ) and bis(7-octenyl)zinc (BOZ) were synthesized from ZnCl 2 and the Grignard reagent prepared from the corresponding bromide. Propene polymerization was conducted with TiCl 3 using those compounds as cocatalyst. The activity strongly depended on the kind of cocatalyst and increased in the following order BBZ < BOZ < AlEt 2 Cl. These catalyst systems gave isotactic polypropylenes whose melting points were around 160 °C. The bis(ω-alkenyl)zinc compounds acted as a chain transfer reagent to give zinc-terminated polymers with low molecular weights. IR, 1 H NMR, and 12 C NMR analyses of the produced polymers indicated incorporation of the 7-octenyl group at the initiation chain end, whereas the 3-butenyl group was not observed, probably due to back-biting cyclization. BOZ copolymerized with propene to give PP having hexylzinc groups as side chains, while BBZ did not. The zinc-carbon bonds at the termination end as well as the side chain were converted to vinyl groups by coupling with allyl bromide to give α,ω-divinyl isotactic polypropylene with pendant 8-nonenyl groups.

Atactic and isotactic polypropylenes having terminal vinylidene groups were prepared with bi(cyclopentadienyl)zirconium dichlorideandethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride-methylaluminoxane catalyst systems. The produced polymers having a vinylidene end group were treated with an excess of borane in benzene, followed by treatment with an excess of 1-hexene. The resulting trialkylboranes were diproportionated with BCl 3 in xylene at 110 o C to obtain alkyldichloroboranes. The products were then brought into contact with 1-butylazide to obtain the polypropylenes having a 1-butylamino group at the chain end in over 80% yield

Atactic and isotactic polypropylenes were respectively prepared with Cp 2 ZrCl 2 - and Et[H 4 -Ind] 2 ZrCl 2 -methylaluminoxane catalyst systems. These polymers were found predominantly to contain vinylidene end groups caused by β-hydrogen elimination. The vinylidene groups were caused to react with an excess amount of (iso-C 4 H 9 ) 2 AlH in heptane or octane at refluxing temperatures to give quantitatively hydroaluminated polymers

Silica-supported titanium catalysts were prepared either by treatment of a silica-supported TiCl 4 with alkyl aluminium under very mild conditions or by supporting CpTiCl 3 on silica. These catlysts gave polypropylene with a high content of insertion errors mostly in blocks of 2,1-oriented propene units. From the copolymerization of propene with a small amount of ethylene, it was found that ethylene is incorporated in the copolymer next to the propene unit with 2,1-orientation.

A liquid-crystalline polymer of 6-[4-(4-ethylphenyl)diazenylphenyloxy]hexyl methacrylate and copolymer of the azobenzene monomer with 4‘-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl were cast as t...

Reaction dans le toluene entre 20 et 40°C en presence de cet amorceur prepare en modifiant un amorceur du type Battelle par MgCl 2 dissous dans l'ethyl-2 hexanol-1

Etude comparee de l'isospecificite des systemes TiCl 3(4) /AlEt 3 et TiCl 3(4) /Cp 2 TiMe 2 supportes sur MgCl 2 dans la polymerisation du propene. L'utilisation de Cp 2 TiMe 2 comme un cocatalyseur permet d'obtenir une isospecificite superieure a 95%