A breathable material that can act as a barrier to chemical agents is presented. The material is composed of butyl rubber and a crosslinkable lyotropic liquid crystal. Under the right synthesis conditions, a cubic phase with the desired selectivity properties results (see figure). The material is highly permeable to water vapor, but strongly impermeable to a mustard gas simulant. Application of the material for effective personal protection against such chemical agents is envisaged.

Substituted half-titanocenes bearing coordinative ether and ester moiety in their side chains, eta(5):eta(1)-C5H4(CH2CH2OMe)TiCl3 (5b), eta(5)-C5H4(CH2CH2CH2OMe)TiCl3 (5c), and eta(5):eta(1)-C5H4(CH2COOMe)TiCl3 (5d), were prepared, and then their catalytic performances for the stereospecific living polymerization of 1,3-butadiene in the presence of the methylaluminoxane (MAO) were investigated. The introduction of intramolecular coordination between central titanium and the ether or ester moiety (5b,d) caused acceleration of polymer propagation rate and enhancement of cis-specificity. The catalyst 5d/MAO showed 114 times larger propagation rate constant than that of the parent nonsubstituted eta(5)-C5H5TiCl3 (5f)/MAO catalyst. The 5b/MAO catalyzed 1,3-butadiene polymerization gave high cis-polybutadiene (99.2% cis content) with narrow molecular weight dispersity (1.14). The single-crystal X-ray crystallographic analysis of 5d and reaction pathway are also discussed.

The polymerization of methyl methaerylate (MMA) was investigated with tris(pentafluorophenyl)alane [Al(C6F5)(3)] and four metallocene imido complexes that varied in the complex symmetry/chirality, metal, and R group in the =NR moiety, as well as a zirconocene enolate preformed from the imido zirconocene and MMA. This study examined four aspects of MMA polymerization: the effects of the metallocene imido complex structure on the polymerization activity and polymer tacticity, the degree of polymerization control, the elementary reactions of the imido complex with Al(C6F5)(3) and MMA, and the polymerization kinetics and mechanism. There was no effect of the imido complex symmetry/chirality on the polymerization stereochemistry; the polymerization followed Bernoullian statistics, producing syndiotactic poly(methyl methacrylate)s with moderate (similar to70% [rr]) to high (similar to91% [rr]) syndiotacticity, depending on the polymerization temperature. Polymerization control was demonstrated by the number-average molecular weight, which increased linearly with an increase in the monomer conversion to 100%, and the relatively small and insensitive polydispersity indices (from 1.21 to 1.17) to conversion. The reactions of the zirconocene imido complex with Al(C6F5), and MMA produced the parent base-free imido complex and the [2 + 4] cycloaddition product (i.e., zirconocene enolate), respectively; the latter product reacted with Al(C6F5), to generate the active zirconocenium enolaluminate. The MMA polymerization with the metallocene imido complex and the alane proceeded via intermolecular Michael addition of the enolaluminate to the alane-activated MMA involved in the propagation step. (C) 2003 Wiley Periodicals, Inc.

Reaction of Me2Si(eta(5)-Me4C5)((BuN)-Bu-t)TiCl2 with lithium indenide and methyllithium in a one-pot fashion produces a chiral ansa-titanocene imido complex, which is an effective initiator for syndiospecific polymerization of MMA.

A new class of monoalkyl or monochloro constrained geometry group 4 complexes has been synthesized; upon activation with aluminium activators they serve as efficient catalysts for olefin polymerisation and for polymerisation of methyl methacrylate.

Sequential stereoblock copolymerization of propylene (P) and methyl methacrylate (MMA) using Group IV single-site metallocene catalysts efficiently produces PP-b-PMMA stereodiblock copolymers. When activated with B(C6F5)(3), C-2-symmetric rac-Et(Ind)(2)ZrMe2 yields isotactic-PP-b-isotactic-PNMA diblock copolymer, whereas C-s-symmetric Me2Si(C5Me4)(tBuN)TiMe2 affords atactic-PP-b-syndiotactic-PMMA diblock copolymer. In the copolymerization catalyzed by the C-2-symmetric catalyst, a very small amount of PMMA homopolymer formed can be removed from the copolymer by extracting the bulk polymer product with boiling methylene chloride. However, separation of isotactic PP formed if any from the copolymer product approves very difficult, due to very similar solubility between the diblock copolymer and isotactic PP homopolymer in various high-boiling chlorinated solvents. On the other hand, in the copolymerization catalyzed by the Cs-symmetric catalyst, both PMMA and atactic PP homopolymers formed in small weight fractions during the copolymerization can be successfully removed from the predominant copolymer product by solvent extraction using boiling heptane. After successful removal of both homopolymers, for example, an atactic-PP-b-syndiotactic-PMMA diblock copolymer has high molecular weight ((M) over bar (n) = 21 100), narrow molecular weight distribution (PDI = 1.08), high PMMA incorporation (33.8 mol-% of PMMA), and moderate syndiotacticity for the PMMA block ([rr] approximate to 80%). Furthermore, the comonomer composition in the copolymer can be controlled by the time for propylene polymerization and the conversion of MMA. A pronounced activator effect is observed; when the same C-s-symmetric catalyst is activated with Ph3CB(C6F5)(4), formation of homopolymers is predominated.

Propylene polymerization was carried out using the [ArN(CH2)3NAr]TiCl2 (Ar = 2,6-iPr2C6H3)/Al(iBu)3/Ph3CB(C6F5)4 catalyst system in the presence of cyclohexene. It was found that isospecific polymerization is promoted by adding cyclohexene even at low propylene concentration. It was also indicated that a considerable number of isospecific active species retain the metal-polymer bond. Based on this fact, isotactic poly(propylene)-block-poly(1-hexene) could be obtained.

Syntheses of terminally hydroxylated and iodinated isotactic poly(propylene)s were carried out by the reactions of oxygen and iodine with polymer–Al bonds produced in propylene polymerization with [ArN(CH2)3NAr]TiCl2 (Ar = 2,6-iPr2C6H3) combined with methylaluminoxane (MAO) as a cocatalyst. The resulting isotactic polymer (ca. 45 wt.-%) was separated from the atactic one by extraction with boiling ether. From 13C NMR measurements of the isotactic fraction, it was found that the content of the terminally functionalized isotactic poly(propylene) was more than 80 mol-% in all cases.

Communication: Supported type cocatalysts using triphenylcarbenium perchlorate (Ph3CClO4) were prepared by impregnation on inorganic carrier, magnesium chloride (MgCl2) and applied to ethylene polymerizations with rac-Et[Ind](2)ZrCl2. Homogeneous polymerizations with Ph3CClO4 were also carried out for comparison. The activity of homogeneous polymerization was much lower than that obtained with methylaluminoxane (MAO). On the other hand, rac-Et[Ind](2)ZrCl2 activated by the supported type Ph3CClO4/MgCl2 system displayed high activity comparable to that obtained with MAO. From the results of fractionation and polymerization of the rac-Et[Ind](2)ZrCl2-Ph3CClO4/MgCl2 catalyst system, it was found that the increased activity mainly came from the active species in the supernatant part. UV-vis spectroscopic measurements combined with ICP analysis indicate that the active species in the supernatant fraction are composed of a stoichiometric amount of perchlorate and metallocene catalyst.

Three kinds of MgCl2-supported trivalent titanocene catalyst (Cat. 1: Cp2TiCl2AlCl2/MgCl2, Cat. 2: CpCp*TiCl/MgCl2, Cat. 3: Cp2TiCl/MgCl2) were prepared and tested for propylene polymerization. It was found that Cat. 1, combined with ordinary alkylaluminum as cocatalyst, produced PP containing 31.8 wt % of isotactic PP in fairly good yield. On the other hand, Cats. 2 and 3 hardly showed any activity. The effects of diisopropyldimethoxysilane (DIPDMS) on isospecificity of the Cat. 1 also were investigated. The isotactic index (I.I.) of PP was improved drastically by the addition of DIPDMS as external donor and reached the value as high as 98.4%, even in the absence of any internal donors. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3355–3359, 2000

Functionalized copolymers were synthesized by the copolymerization of ethylene and 1,9-decadiene with Me2Si(Flu)2ZrMe2–MAO catalyst system. Alternating copolymers were obtained with the degree of alternation higher than 98.2%. Undesirable side reactions such as cyclization and crosslinking were found completely suppressed. The resulting copolymer was quantitatively grafted by polysiloxanes by the hydrosilylation reaction as shown in the scheme. This is the first result reporting the alternating copolymerization of dienes and ethylene without any side reactions of a second double bond and the quantitative functionalization on the side chains of the copolymers.

Inorganic siliceous porous materials such as Mn type zeolite, mesoporous silica MCM-41 and silica gel with different average pore diameters were applied to the adsorptive separation of methylaluminoxane (MAO) used as a cocatalyst in alpha-olefin polymerizations. The separated MAOs combined with rac-ethylene-(bisindenyl)zirconium dichloride (rac-Et(Ind)(2)ZrCl2) were introduced to propylene polymerization, and their influences on the polymerization activity and stereoregularity of the resulting polymers were investigated. The polymerization activity and isotactic [mmmm] pentad of the produced propylene were markedly dependent upon the pore size of the porous material used for adsorptive separation. From the results obtained from solvent extraction of the produced polymers, it was suggested that there are at least two kinds of active species with different stereospecificity :in the rac-Et(Ind)(2)ZrCl2/MAO catalyst system.

Poly(styrene-co-divinylbenzene) beads supported rac-Ph2Si(Ind)2ZrCl2 was prepared and tested as a catalyst for ethene polymerization using methylaluminoxane (MAO) as a cocatalyst. At a polymerization temperature below 100°C, the catalyst showed pretty high activity to give polyethene beads replicating the shape of the carrier. With increasing polymerization temperature up to 150°C, the catalyst activity increased drastically but the spherical shape of polyethene disappeared due to the melting. From the plots of apparent activity against polymerization temperature, it was suggested that the polymerization below 100°C is more or less controlled by monomer diffusion through the crystalline polyethene films.

Polymerization of propylene was conducted at 0 ∼ 150°C with the [ArN(CH2)3NAr]TiCl2 (Ar = 2,6-iPr2C6H3) complex using a mixture of trialkylaluminium (AIR3, R = methyl, ethyl and isobutyl) and Ph3CB(C6F5)4 as cocatalyst. When AlMe3 or AlEt3 was employed, atactic polypropylene (PP) was selectively produced, whereas the use of Al(iBu)3 gave a mixture of atactic and isotactic PP. The isotactic index (I.I.; weight fraction of isotactic polymer) depended strongly upon the polymerization temperature, and the highest I.I. was obtained at ca. 40°C. The 13C NMR analysis of the isotactic polymer suggests that the isotactic polymerization proceeds by an enantiomorphic-site mechanism. It was also demonstrated that the present catalyst shows a very high regiospecificity.

Various MgCl2-supported Ti(4,4,4-trifluoro-1-phenyl-1,3-butanedionato)(2)Cl-2 catalysts with different Ti contents (0.017 similar to 0.002 mmol/g) were synthesized and applied to propene polymerization using tri ethylaluminium and di-i-propyldimethoxysilane (DIPDMS) as the cocatalyst and external donor, respectively. When polymerization was conducted in the absence of DIPDMS, neither the activity nor the isospecificity of catalyst were dependent upon the Ti content. However, the effect of DIPDMS on the catalyst performance was found to be markedly dependent upon the Ti content, i.e., the addition of DIPDMS to the catalyst with low Ti content caused a prominent increase in the activity for isotactic polymerization. As a result, the present catalyst with low Ti content gave a highly isotactic polypropene with T-m= 169.3 degrees C and [mmmm] > 99% in high selectivity (I.I.. = 97.7%).