Kiyoshi Endo

Synthesis and Properties of Cyclic Polymers

Thousands of polymeric materials have been made into synthetic polymers, based on a linear structure, and used in commercial applications. The study of synthetic polymeric materials has focused on those derived from long chain linear molecules. Alternatively, cyclic polymers (also referred to as polymer rings or macrocycles) can be prepared, which not only can be branched or cross-linked, but can also form noncovalently linked structures based on their loop topology. Through a number of different approaches and advances in cyclization techniques, a wide range of novel cyclic polymers have been synthesized in good yields. This review will focus on a variety of synthetic methods and some properties of cyclic polymers using many polymerization mechanisms in various fields of polymer synthesis.

Synthesis and structure of poly(vinyl chloride)

Abstract This article deals with the synthesis and structure of poly(vinyl chloride) (PVC) by radical and other polymerization mechanisms. The features of solution, bulk, suspension, and emulsion polymerization of VC are described. Terminal structure and defect structures introduced in the chain during the polymerization are discussed. Control of core–shell structure provides one method to improve the thermal stability of PVC. Tacticity and crystallinity of PVC play an important role regarding the use of PVC. Radical copolymerization of VC with various vinyl monomers has been described to improve the thermal stability of PVC. Graft copolymerizations with other vinyl monomers including use of labile chlorine atoms are useful methods to improve the physical and thermal properties of PVC. Synthesis of block copolymers has also been described by mechano-chemical methods and using terminal functional polymers. Controlled polymerization can be achieved with anionic polymerization catalysts. Promising metallocene catalyst promoted polymerization of VC are also described.

Syndiospecific copolymerization of styrene with styrene macromonomer bearing terminal styryl group by CpTiCl3–methylaluminoxane catalyst

Abstract Copolymerization of styrene with styrene-terminated polystyrene macromonomer (SSTM) by CpTiCl 3 –methylaluminoxane (MAO) catalyst was investigated. SSTM was prepared by a reaction of living polystyrene initiated with sec -butyllithium ( s -BuLi) and p -chloromethyl styrene at −78°C. The synthesized SSTM has a high terminal functionality and a narrow molecular weight distribution. Graft copolymers of polystyrene consisted of syndiotactic main chain and atactic side chain were synthesized by CpTiCl 3 –MAO catalyst. The synthesized graft copolymer was confirmed to have highly syndiotactic sequence on the main chain.

Polymerization of methyl methacrylate with Ni(acac)2-methylaluminoxane catalyst

Polymerization of methyl methacrylate (MMA) with nickel(II) acetylacetonate [Ni(acac)2] in combination with methylaluminoxane (MAO) was investigated. Ni(acac)2 was found to be an effective catalyst for the polymerization of MMA. From a kinetic study of the polymerization of MMA with the Ni(acac)2–MAO catalyst, the overall activation energy was estimated to be 15 kJmol−1. The polymerization rate (Rp) was expressed as follows: Rp = k [MMA]1.0[Ni(acac)2–MAO]0.6 (the MAO/Ni mole ratio was kept constant). The mechanism for the polymerization of vinyl monomers with the Ni(acac)2–MAO catalyst is discussed. © 2000 Society of Chemical Industry

Syndiospecific copolymerization of styrene with styrene terminated isoprene macromonomer by CpTiCl3-methylaluminoxane catalyst

Copolymerization of styrene with styrene terminated polyisoprene macromonomer (SIPM) by CpTiCl3-methylaluminoxane (MAO) catalyst has been investigated (Cp: cyclopentadienyl). SIPM was prepared by reaction of living polyisoprene initiated with sec-butyllithium (s-BuLi) and p-chloromethylstyrene. The synthesized macromonomer has a high terminal degree of functionalization and a narrow molecular weight distribution. Graft copolymers of polystyrene-graft-polyisoprene have been synthesized with the CpTiCl3-MAO catalyst. The synthesized graft copolymer was confirmed to have a highly syndiotactic sequence on the main chain.

Dechlorination of poly(vinyl chloride) without anomalous units under high pressure and at high temperature in water

Dechlorination of poly(vinyl chloride) (PVC) prepared by polymerization of vinyl chloride (VC) with two kinds of butyllithium (BuLi), t-BuLi and n-BuLi, was investigated under conditions of high pressure and high temperature water. Dechlorination was induced completely and polyene polymer was formed from PVC under high pressure and high temperature. The polymers obtained from polymerization of VC with the t-BuLi and n-BuLi revealed different decomposition behavior from that obtained with a radical initiator such as lauryl peroxide. This was attributed to the different chemical structure of the PVC sample. Namely, the PVC obtained with BuLi has no anomalous structures, but PVC obtained with radical initiator has different types of anomalous units. Complete dechlorination of PVC could be achieved in hot water at 19.3 MPa and 300°C.

Polymerization of butadiene with V(acac)3-methylaluminoxane catalyst

Full Paper: Polymerization of butadiene (Bd) with V(acac)3-methylaluminoxane (MAO) catalyst was investigated. The microstructure of the polymer was found to depend strongly on the polymerization conditions. High polymerization temperature and high MAO/V(acac)3 mole ratios were preferential to produce cis-1,4 structure. Two kinds of active species were presumed from the GPC measurement of the polymers; one gives a high molecular weight polymer bearing high cis-1,4 content, another affords a low molecular weight polymer with high trans-1,4 content. A Solvent effect was observed. A polymer consisting of mainly trans-1,4 unit was produced in CH2Cl2 in contrast to toluene and n-heptane in which polymers consisting of mainly cis-1,4 structure were observed. The addition of ethyl benzoate, triethylamine, chloranil, and tetracyanoquinodimethane to the V(acac)3-MAO catalyst gave an influence to not only the activity for the polymerization but also the microstructure of the polymer.

Determination of cyclic structure for polydithiane using electrospray ionization mass spectrometry

Disulfide polymers obtained by ring-opening polymerization have been considered to have a possibility of a cyclic catenane structure as judged from their test properties on the loss modulus and stress–strain. Electrospray ionization mass spectrometry (ESI-MS) was used to detemine molecular structure of polydithiane and polyoxyethylene to find whether they are present as a cyclic or as a linear structure. The results indicated that the polydithiane possesses the cyclic structure, and analysis of the isotope distribution of the spectral ions further showed that the polymer consists entirely of the cyclic structure without contamination of a linear polymer. A linear chain polymer with a benzylmercaptan end group was synthesized, and the ESI-MS analysis revealed that the polymer was a mixture of both the cyclic and the linear polymer. The cyclic polymer is probably formed by back-biting of the highly reactive sulfur radicals that had been formed during the polymerization reaction.

Synthesis of a novel syndiotactic poly(macromonomer) consisting of styrene‐terminated polyisoprene macromonomers using half‐titanocene catalysts

Homopolymerization of a stytene-terminated polyisoprene macromonomer (SIPM) by half-titanocene catalysts in conbination with methylaluminoxane (MAO) was investigated. Polymerization of the SIPM with CpTiCl 3 -MAO as the catalyst was found to proceed readily to give a high molecular weight polymer. 1 H and 13 C spectra of the poly(SIPM) after ozonolysis of the isoprene side chain revealed that poly(SIPM) is a highly syndiotactic polymer. Syndiotactic poly(SIPM) is soluble in usual solvents in spite of having highly syndiotactic sequences on its main chain and a considerable degree of polymerization.

1,2-Polymerization of 1,3-butadiene with Cr(acac)3-alkylaluminum catalysts

The polymerization of butadiene (Bd) with chromium(III) acetylacetonato [Cr(acac)3]-trialkylaluminum (AlR3) or methylaluminoxane (MAO) catalysts was investigated for the synthesis of 1,2-poly(Bd). The polymerization of Bd was found to proceed with Cr(acac)3-AlR3 (R-Me, Et, i-Bu) catalysts to give poly(Bd) with a high 1,2-vinyl content, but highly isotactic 1,2-poly(Bd) was not synthesized. The Cr(acac)3-MAO catalyst gave a polymer consisting of low 1,2 units. The effects of the Al/Cr mole ratios on the polymerization of Bd with the Cr(acac)3-AlR3 catalysts were observed. With an increase of Al/Cr mole ratios, the isotactic (mm) content of the polymer increased but the 1,2-vinyl contents decreased. The effects of the aging time and temperatures of the catalysts on the polymerization of Bd with the Cr(acac)3-AlR3 catalysts were also observed, and the lower polymerization temperature and the prolonged aging time were favored to produce the 1,2-vinyl structure.