Plastic materials, due to its light weight, have greatly contributed to improving fuel efficiency and reducing carbon dioxide emissions by substituting metals in the fields of automobiles and aircraft. On the other hand, there are concerns about carbon dioxide emissions due to the use of fossil resources in the main raw materials and production processes. In addition, the seriousness of marine pollution caused by the outflow of plastics into the sea without being decomposed has been reported. Therefore modern plastics will be required to low environmental load such as improving the ratio of renewable resources and biodegradability while maintaining high strength, lightness and processability. Cellulose nano-fibers （CNFs） accounting for about half the dry weight of plants are the largest biomass resource on earth. The densities 1.5g/cm3 of the CNFs are lighter than glass fiber （2.5g/cm3） and carbon fiber （1.8g/cm3）, and the CNFs has higher modulus, higher strength, and low thermal expansion （0.1ppm/K）.　It is promising as a plastic reinforced fiber because it has the environmental performance required for modern plastic materials. “Kyoto Process” that a CNF-reinforced plastic integrated manufacturing process developed in Kyoto is introduced in this review. The performance and functionality of the obtained materials consisted of CNFs and plastics, their application development, and the utilization of CNF other than plastic applications in Kyoto are explained in detail.

The present comprehensive paper deals with functionalization and high-performance of biopolymers by precise interface control, in which cellulose, one of the most typical biopolymers, and biomass plastics contributing to contraction of carbon neutral society are focused. By utilizing the layered structure of bacterial cellulose（ BC） produced by microorganisms and inserting hydrophilic polymers between the layers, a specific swelling-shrinking behavior was observed. Functional BC-based materials were prepared by introducing temperature-responsive polymers, ionic polymers, and conductive polymers into the layer of BC. Composites of BC and porous materials （monoliths） were developed and converted into functional activated carbons with hierarchical structure by carbonization/activation, which were applied to electrodes. Developed was an effective water-based method to render the cellulose surface with high carboxyl content through the esterification of hydroxyl groups with citric acid in a solid phase reaction without use of noxious solvents. This modified cellulose acted as filler of common plastics and poly（L-lactic acid）（ PLLA） to improve their properties. Blending of Eucommia elastomer（ EuTPI） and PLLA by the dynamic crosslinking highly improved the toughness and impact resistance.

It is known that the reaction of 4,4’-diglycidyloxydiphenylether and 4,4’-dihydroxybiphenyl gives a crystalline polymer. With the aim of introducing a crosslinked structure, the influence of adding catechol novolac （CNV） as a curing agent was investigated. By adding 10 wt% of CNV, a crystalline polymer having a crosslinking structure with a Tm of 241.0 °C was obtained. Due to its crystalline structure, the thermal conductivity was 0.29 W/m·K, which was about 1.5 times that of a conventional epoxy resin. Furthermore, it was confirmed that the orientation of the molecular chain was maintained even at a temperature of 300 °C by introducing the crosslinking structure.