Triblock copolymers, poly(γ-benzyl-L-glutamate)-block-polyisoprene-block- poly(γ-benzyl-L-glutamate) (PBLG-b PI-b-PBLG), were prepared via the ring-opening polymerization of a N-carboxyanhydride of γ-benzyl-L-glutamate initiated with a diamino-terminated PI. Aggregate formation in solution was confirmed by dynamic light scattering measurement. The triblock copolymer was cross-linked via thermal polymerization of the double bond moieties in the PI segment. The phase separation behavior of the PBLG and PI segments was visualized by hydrolysis of the PBLG segment.

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SynopsisSolvent soluble branched imide resin was successfully synthesized from isocyanurates and anhydrides. This imide resin is soluble in general organic solvents such as methyl ethyl ketone cyclohexanone, propylene glycol methyl ether acetate, and so on. The branched imide resin having carboxylic groups at the chain terminals was cured with epoxy resins to give the film of excellent thermal resistance. For example, Tg of the film cured at 170℃ with o-cresole novolac type epoxy resin is 265℃. Furthermore, transparent colorless imide resin with branched structure was also successfully synthesized. It was considered that these properties come from branched structure of imide resins.

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SynopsisNovel polymers with dynamic bonds were developed from prepolymers having anthracene groups in side chains and at chain ends. The polymerization of the prepolymer by photodimerization of anthracene group and the depolymerization by photo-/thermal-dissociation of the linkage were followed by UV-vis measurement. As main chains of the prepolymers, polystyrene and poly(ethylene adipate) were selected. Polystyrene is in the glass state at room temperature while poly(ethylene adipate) is in the semicrystalline state. Through the comparison of the polymerization/depolymerization behavior of these polymers, the effect of the molecular mobility on the reaction was discussed.

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SynopsisPreparation of lignophenol (LP)-cured epoxy resin (LER) and evaluation of properties of the obtained resin were studied as a part of effective use of biomass materials. Curing reaction between LP and bisphenol A diglycidyl ether (DGEBA) was carried out by heating up to 180 °C in the presence of imidazole derivative (2E4MZ-CN) to afford LERs as novel thermosetting resins (LERs). LERs had well-balanced thermal and mechanical properties. Especially, LER2 (epoxy group : phenol group = 1 : 0.9 ) showed the superior properties, that is, glass transition temperature (Tg) of 198 °C and 5% weight loss temperature (Td5) of at 373 °C. The Tg was more than 60 °C higher than that of the conventional phenol novolac-cured DGEBA. However, the flexural strength of LER2 was 134 MPa, which was a little lower than that of the phenol novolaccured DGEBA. From these results, it was demonstrated that LP was a promising curing agent for epoxy resins.

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SynopsisTo improve the impact resistance of polyamide 6, we tried to form polymer alloy by the polymerization of ε-caprolactam in the presence of prepolymers consisting of flexible chain with isocyanate group at the both terminals. In this system, polyamide 6 and the block copolymer having flexible chain in as the middle segment were generated to form polymer alloy automatically. IZOD impact tests revealed that the polymer alloy was improved in impact strength compared with polyamide 6. Further, we evaluated the impact energy absorption of the glass fiber-reinforced composite produced with the polymer alloy as the matrix resin. As the results, the impact energy absorption was 1.4 times higher than that with polyamide 6 matrix.

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SynopsisCyclic monomers such as spiro orthoesters (SOEs), bicyclo orthoesters (BOEs), and cyclic carbonates undergo equilibrium polymerization, and therefore, their polymerization-depolymerization behaviors can be controlled by changing reaction conditions. In this review, we describe chemical recycling system by the depolymerization of linear polymers and decrosslinking of insoluble networked polymers to soluble linear polymers or bifunctional monomers based on equilibrium polymerization function of cyclic monomers.

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