Effect of accelerators on the vulcanization of natural rubber was investigated by analyzing structure of the crosslinking junctions through rubber state NMR spectroscopy. The accelerated sulfur vulcanization of natural rubber was carried out with one of the three accelerators, i.e., Zinc diethyldithiocarbamate (ZDEC), Zinc dibutyldithiocarbamate (ZDBC) and Zinc salt of 2-mercaptobenzothiazole (ZMBT), in the presence of sulfur, ZnO and stearic acid. Structure of the crosslinking junctions of the vulcanized natural rubbers was determined through rubber-state NMR spectroscopy with bilevel complete decoupling (BCM), distortionless enhancement by polarization transfer (DEPT) and attached proton test (ATP). The mechanism of the vulcanization of natural rubber was demonstratively analyzed on the basis of the structure of the resulting crosslinking junctions. It was classified into two schemes: that is, radical mechanism and ionic mechanism followed by radical mechanism, depending on the sort of accelerators used in the present study.

Conventional bio-degradable polymers have been successfully developed but the control of degradation is indispensable for actual application as useful materials in sustainable society. Here biomonomer having multifunctional structure such as itaconic acid (IA) which has two carboxyls and double bond and whose bioavailability was very high. was used for Nylon development. But IA polymerization was very difficult and the polycondensation of IA to prepare the polyamide structure was not reported as scientific paper. We have prepared IA-derived Nylon via salt-type monomers composed of diacidic IA and diamines. These salts thermally converted into Nylon in the presence of phosphate catalysts to create a pyrrolidone ring in the polymer backbone. The Nylon have thermally softening temperature and mechanical strength higher than conventional Nylon’s. In addition, the polyamides became soluble in water by ring-opening reaction of the pyrrolidone. Actually, the ring-opening reaction was induced by ultra-violet irradiation and landfill in environmental soil as well as alkaline hydrolysis. Especially photo-induced water-solubilization is very important for development of environmentally-corrosive fish line to avoid the ghost-fishing destroying the ecological system around ocean.

The design, synthesis, and function of dynamic soft materials utilizing the rotaxane’s structural characteristics have collected much interests of polymer scientists. Directed toward the development of the dynamic soft materials based on the linear-branched polymer topology transformation, the various linear-branched polymer topology transformation systems were constructed by using the dynamic nature of the rotaxane’s components. The topology difference between the linear and branched polymers prepared in this work could be confirmed by the difference in hydrodynamic volume, crystallinity, and morphology. In particular, three-armed star polymer-type branched polymer was synthesized using living polymerization and polymer reaction for the arm and star polymer synthesis, while the star polymer showed clear morphological difference besides those in hydrodynamic volume and viscosity toward the corresponding linear counterpart. Four-armed star polymer having two rotaxane-linked polymer chains was synthesized for the study on the physical property difference from the linear counterpart prepared by the cleavage of the attractive interaction between the rotaxane components. The physical property difference between the star and linear polymers was explained by the difference in polymer topology. Reversible linear-branched polymer topology system was constructed by the introduction of N-methyl moiety on the ammonium salt moiety placed on the axle component of the crown ether-based rotaxane structure. These results suggest the possible development of the dynamic soft materials as the stimuli-responsive polymers based on the reversible polymer topology transformation through the rotaxane’s dynamic structural control.