Measurements of shear dynamic modulus have been made on the polybutadiene samples firstly cross-linked partly followed by the second cross-linking in large extension. The polymers prepared in this manner were expected to keep anisotropic chain configuration. The polymers showed different behaviors in G′ and tanδ from those cross-linked at no deformation. The former polymers showed lower values of G′ and higher values of tanδ than the latter polymers. The deviations became large with increase in degree of extension. It may be concluded that chain anisotropy is really one of the origins for nonlinear viscoelasticity of polymers. It lowers the energy storage term and raises the energy loss term.

抄録全体を表示

Controlled 1,4-cis specific polymerization of butadiene (Bd) with N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diphenylethylenediaminato cobalt (1), in combination with methylaluminoxane (MAO) was investigated. 1/MAO catalyst showed the high activity for the polymerization of Bd. In the polymerization of Bd with 1/MAO catalysts in CH₂Cl₂ at −30°C, the molecular weight of the polymer increased linearly with an increase of polymer yield, and the line passed through the origin. Moreover, the molecular weight distribution of the polymer was narrow (M_w/M_n=1.29) and microstructure was a high 1,4-cis content (~98%). The results demonstrate that a simultaneous control of 1,4-cis selectivity and the molecular weight of the polymer can be achieved in the polymerization of Bd with the (salen)Co(II) having t-butyl groups at 3,3′,5,5′-positions in the aromatic ring and phenyl groups at N,N′-positions in combination with MAO.

抄録全体を表示

Time-resolved simultaneous synchrotron small-angle X-ray scattering and differential scanning calorimetry experiments have been performed on crystallization of polyethylene-polyisoprene diblock copolymers (HEI or LEI) and their blends with corresponding homopolymers, polyethylene (PE) and polyisoprene (PIp). For the neat block copolymer having a 50 wt% of the crystalline component, preexisting microphase separation structure in the melt was kept at high and low crystallization temperatures T_c (T_c≥94°C and T_c<60°C), while disrupted at intermediate T_c (60°C≤T_c<94°C). This complex behavior was interpreted by combination of two mechanisms. The behavior in the crystallization below 94°C was attributed to the competition between the crystallization and chain diffusion rates, that is, the fast crystallization rate at lower T_c makes it difficult to rearrange the phase structure in the melt. On the other hand, at a higher T_c (≥94°C), the preservation of the microphase separation structure was explained by a small degree of crystallinity due to the ethyl branch of polyethylene (hydrogenated poly(butadiene)). For HEI/PE blends, crystallization behavior was the simple superposition of those for HEI and PE, while, for HEI/PIp with a small composition of PE, suppression of crystallinity was observed. Crystallization kinetics in the neat block copolymer and all the blends was not so different from that in the PE homopolymer.

抄録全体を表示

Anionic polymerization of N,N-diethyl-2-methylene-3-butenamide (DEA), which is a 1,3-butadiene derivative containing a diethylamide function, was carried out in tetrahydrofurane (THF) under various conditions. When DEA was polymerized in THF at −78°C using potassium naphthalenide (K-Naph) or diphenylmethylpotassium (DPMK) as an initiator, a polymer of predictable molecular weight with a narrow molecular weight distribution was obtained. However, the rate of polymerization was extremely slow to reach 80% conversion after 720 h. When the polymerization temperature was raised to 20°C, a low molecular weight oligomer with a broad molecular weight distribution was obtained because of a chain transfer reaction. On the other hand, no such side reaction occurred even at 20°C, when polymerization was carried out in the presence of LiCl. Also, the chain transfer reaction did not occur in lithium naphthalenide (Li-Naph) initiated polymerization. The microstructure of the polymer prepared using a potassium counter cation was a 1 : 1 mixture of 1,4-E and 1,2- structures. In the case of Li-Naph or DPMK/LiCl systems, the microstructure was a complicated mixture of 1,4-E, 1,4-Z, and 1,2-structures.

抄録全体を表示