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Poly(L‐lactide) (PLA) was melt‐blended with four rubber components—ethylene–propylene copolymer, ethylene–acrylic rubber, acrylonitrile–butadiene rubber (NBR), and isoprene rubber (IR)—in an effort to toughen PLA. All the blend samples exhibited distinct phase separation. Amorphous PLA constituted a topologically continuous matrix in which the rubber particles were dispersed. According to Izod impact testing, toughening was achieved only when PLA was blended with NBR, which showed the smallest particle size in its blend samples. In agreement with the morphological analysis, the value of the interfacial tension between the PLA phase and the NBR phase was the lowest, and this suggested that rubber with a high polarity was more suitable for toughening PLA. Under the tensile stress conditions for NBR and IR blend samples, these rubbers displayed no crosslinking and showed a high ability to induce plastic deformation before the break as well as high elongation properties; this suggested that the intrinsic mobility of the rubber was important for the dissipation of the breaking energy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A novel intrinsically stretchable ABA triblock copolymer can be synthesized where A and B are poly­(3-hexylthiophene) (P3HT) and polyisobutylene (PIB) segments, respectively. The deformation of the self-assembled hierarchical nanostructure of the block copolymer thin film was clearly observed by grazing incidence small- and wide-angle X-ray scattering.

The first radical polymerization of 1 -methoxy-o-quinodimethane (2) generated by thermal ring-opening isomerization of 1 -methoxybenzocyclobutene (1) is described. The polymerization of 1 in the presence of a radical initiator afforded an MeOH-insoluble polymer (3) in moderate yield at temperatures above 90°C. The structure of the obtained polymer is consistent with a ring-opening polymerization. The yield of the polymer increased with the amount of initiator. Radical copolymerization with methyl acrylate was carried out. Treatment of 3 with acid gave poly(o-phenylenevinylene), quantitatively.

The substituent effect on the polymerization of o-quinodimethanes generated by thermal isomerization of benzocyclobutenes and the reaction of the obtained polymer is described. Polymerizations of 1-methoxybenzocyclobutene (1), 1-acetoxy benzocyclobutene (2), 1-hydroxybenzocyclobutene (3), and 1-((trimethylsilyl)oxy)benzocyclobutene (4) as benzocyclobutenes bearing electron-donating groups were examined. Although polymerization of 2 and 3 did not afford any polymer, polymerization of 1 and 4 in the presence of a radical initiator gave MeOH-insoluble polymer (Mn ) 5000-11000) in moderate yields at temperatures above 90°C, respectively. The structures of the obtained polymers were confirmed to be ring-opened polymer (5, 6) by IR, 1 H-NMR, and 13 C-NMR. The yield of the polymer increased with increase of the concentration of the initiator. This polymerization was supported to proceed based on the driving force of aromatization stabilizing effect by semiempirical calculation. Radical copolymerizations of 1 with vinyl monomers were carried out to obtain the corresponding copolymers. Lastly, treatment of 3 with p-toluenesulfonic acid (10%) gave poly(o-phenylenevinylene) (7) quantitatively and its properties (UV absorption, Tg, Td10 (10% weight loss temperature)) were estimated.

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Thermoreversible crosslinking rubber (TRC-IR) was easily synthesized by modification of isoprene rubber (IR) with maleic anhydride followed by the addition of 3-amino-1,2,4-triazole (ATA), in solid phase. The mechanical properties of the resulting rubber were more similar to the sulfur-vulcanized rubber than general thermoplastic elastomers (ex. SEBS). Although the tensile strength and elongation at break were lower than those of a corresponding sulfur-vulcanized rubber, the moduli were as high as those of sulfur-cured rubber. Re-molding of TRC-IR could be repeated more than 10 times without significantly changing its mechanical properties. Differential scanning calorimetry (DSC) and infrared analyses revealed that the superior mechanical properties and good recyclability are attributable to the strong hydrogen bonding. The TRC-IR showed an endothermic transition peak at around 185 °C on the DSC chart, indicating cleavage of the hydrogen bonding. Infrared analyses also revealed that the absorption peaks of carboxylic acid were shifted to a lower region by the strong hydrogen bonding. The thermoreversible crosslinking system was also applied to EPM, EBM (ethylene-butene rubber), and IIR. These rubbers also showed superior mechanical properties as well as excellent recyclability.

Abstract4‐Vinylbenzocyclobutene (1) was prepared by the nickel‐catalyzed coupling reaction of 4‐bromobenzocyclobutene with vinylbromide in 70% yield. Radical homopolymerization of 1 at 60°C for 24 h afforded poly(4 vinylbenzocyclobutene) [poly(1)] in 89% yield and radical copolymerizations of 1 with styrene (St) or methyl methacrylate (MMA) were carried out to obtain the corresponding copolymers. The Q = 1.07, e = 0.046. As a model reaction of the polymer reaction of the polymer reaction of poly(1) and poly(4‐vinylbenzocyclobutene‐co‐styrene) [copoly(1‐St)] with dienophiles, the Diels‐Alder reaction of benzocyclobutene with N‐phenylmaleimide (MI) or maleic anhydride (MANH) was carried out to determine the optimum reaction conditions. Under the optimum condition, the Diels‐Alder reaction of poly(1) and copoly(1‐St) with MI and MANH in the presence of 4‐tert‐butyl‐catechol as an inhibitor were carried out to yield the corresponding polymers in good yields. The properties (solubilities, Tg, and temperature of 10% weight loss) of the products obtained from the polymer reaction were different from these of poly(1). © 1995 John Wiley & Sons, Inc.