Synthesis of polyolefin (PO)-based block copolymers is of immense research interest. In this work, we report a strategy for the construction of polystyrene (PS)-block-PO-block-PS, a useful thermoplastic elastomer, directly from olefin and styrene monomers. Multinuclear zinc species Et­[Zn­(CH2)6] a ZnEt were prepared through successive additions of BH3 and Et2Zn to 1,5-hexadiene. Poly­(ethylene-co-propylene) chains were biaxially grown from the −(CH2)6– units in Et­[Zn­(CH2)6] a ZnEt via “coordinative chain transfer polymerization (CCTP)” using the pyridylaminohafnium catalyst. PS chains were subsequently grown in one pot from the generated polymeryl–Zn sites by subsequent introduction of the anionic initiator Me3SiCH2Li·(pmdeta) (pmdeta, pentamethyl­diethylenetriamine) and styrene monomers. The fraction of the extracted PS homopolymer grown from the Me3SiCH2 sites was low (homo-PS (g)/total PS (g), 15–22%). The gel permeation chromatography (GPC) curves shifted evidently after styrene polymerization, and change in the molecular weight (ΔM n, 39–56 kDa) was approximately twice the homo-PS M n (20–23 kDa), in accordance with attachment of the PS chains at both ends of the PO chains. Transmission electron microscopy analysis of the thin films showed segregation of the PS domains in the PO matrix to form spherical or wormlike rippled structures depending on the PS content. The prepared triblock copolymers exhibited elastomeric properties in the cyclic tensile test, similar to the commercial PS-block-poly­(ethylene-co-1-butene)-block-PS.

Dimethyl carbonate (DMC) is an environmentally benign chemical currently produced using CO 2 . Using the conventional Dean-Stark apparatus, a method was developed for the effective and selective removal of the methanol generated in the transesterification of DMC with alcohol. Using this device, various diols (HO-A-OH; A 5 (CH 2 ) 4 , (CH 2 ) 2 O(CH 2 ) 2 , CH 2 C 6 H 10 CH 2 , and CH 2 C 6 H 4 CH 2 ) were converted to mixtures of the corresponding MeOC (O)[O-A-OC(O)]OMe and MeOC(O)[O-A-OC(O)] 2 OMe. Dialkyl carbonates such as dibutyl carbonate, dibenzyl carbonate, and diallyl carbonate were also efficiently prepared from the corresponding alcohols using this device. The compound prepared from 1,4-butanediol, MeOC(O)[O(CH 2 ) 4 OC(O)] 1.5 OMe, was subjected to polycondensation with HO(CH 2 ) 4 [O 2 CC 6 H 4 CO 2 (CH 2 ) 4 ] 1.5 OH or HO(CH 2 ) 4 [O 2 CC 6 H 4 CO 2 (CH 2 ) 4 ] 1.8 OH, which directly was prepared from terephthalic acid and 1,4-butanediol. The polycondensation afforded high-molecular-weight poly(1,4-butylene carbonate-co-terephthalate)s (PBCTs) with M w of 80-270 kDa and 0.40-0.46 terephthalate mole fractions. PBCTs are attractive materials with potential biodegradability and LDPE-like thermal properties.

Triblock copolymers of polystyrene (PS) and a polyolefin (PO), e.g., PS-block-poly(ethyleneco-1-butene)-block-PS (SEBS), are attractive materials for use as thermoplastic elastomers and are produced commercially by a two-step process that involves the costly hydrogenation of PS-block-polybutadiene-block-PS. We herein report a one-pot strategy for attaching PS chains to both ends of PO chains to construct PS-block-PO-block-PS directly from olefin and styrene monomers. Dialkylzinc compound containing styrene moieties ((CH 2 =CHC 6 H 4 CH 2 CH 2 ) 2 Zn) was prepared, from which poly(ethylene-co-propylene) chains were grown via "coordinative chain transfer polymerization" using the pyridylaminohafnium catalyst to afford di-end functional PO chains functionalized with styrene and Zn moieties. Subsequently, PS chains were attached at both ends of the PO chains by introduction of styrene monomers in addition to the anionic initiator Me 3 SiCH 2 Li·(pmdeta) (pmdeta = pentamethyldiethylenetriamine). We found that the fraction of the extracted PS homopolymer was low (~20%) and that molecular weights were evidently increased after the styrene polymerization (∆M n = 27-54 kDa). Transmission electron microscopy showed spherical and wormlike PS domains measuring several tens of nm segregated within the PO matrix. Optimal tensile properties were observed for the sample containing a propylene mole fraction of 0.25 and a styrene content of 33%. Finally, in the cyclic tensile test, the prepared copolymers exhibited thermoplastic elastomeric properties with no breakage up over 10 cycles, which is comparable to the behavior of commercial-grade SEBS.

The Me2Si-bridged ansa-Cp/amido half-metallocene, [Me2Si(η5-Me4C5)(NtBu)]TiCl2, termed a “constrained-geometry catalyst (CGC)”, is a representative homogeneous Ziegler catalyst. CGC derivatives with the [1,2]azasilinane framework, in which the amide alkyl substituent is joined by the Si-bridge, were prepared, and the catalytic performances of these species was studied. Me4C5HSi(Me)(CH2CH=CH2)-NH(C(R)(R’)CH=CH2) (R, R’ = H or methyl; Me4C5H = tetramethylcyclopentadienyl) was susceptible to ring closure metathesis (RCM) when treated with Schrock’s Mo-catalyst to afford -Si(Me4C5H)(Me)CH2CH=CHC(R)(R’)NH- containing a six-membered ring framework. Using the precursors and the products of RCM, various CGC derivatives, i.e., [-Si(η5-Me4C5)(Me)CH2CH=CHC(R)(H)N-]TiMe2 (13, R = H; 15, R = Me), [-Si(η5-Me4C5)(Me)CH2CH2CH2CH2N]TiMe2 (14), [(η5-Me4C5)Si(Me)(CH2CH=CH2)NCH2CH=CH2]TiMe2 (16), [(η5-Me4C5)Si (Me)(CH=CH2)NCH2CH=CH2]TiMe2 (17), and [(η5-Me4C5)Si(Me)(CH2CH3)NCH2CH2CH3]TiMe2 (18), were prepared. The catalytic activity of the newly prepared complexes was lower than that of CGC when activated with [Ph3C][B(C6F5)4]/iBu3Al. However, the catalytic activity of these species was improved by using tetrabutylaluminoxane ([iBu2Al]2O) instead of iBu3Al and the activity of 14/[Ph3C][B(C6F5)4]/[iBu2Al]2O was comparable to that of CGC/[Ph3C][B(C6F5)4]/iBu3Al (4.7 and 5.0 × 106 g/mol-Ti, respectively). Advantageously, the newly prepared complexes produced higher molecular weight poly(ethylene-co-1-octene)s than CGC.