Castor oil is a non-edible vegetable oil harvested around 700,000 tons per year in the world. The bestfeature of the castor oil contains about 90% of Ricinoleyl group. Ricinoleic acid has a hydroxyl group on the12th carbon. And itself is used as a polyol. Castor oil based polyols have property of lower water absorptionthan that of petroleum derived polyether type or polyester polyol, and it is utilized for flooring materials,anticorrosion coatings, electric insulating potting materials, two component solvent free adhesive and foam.Further, since it is compatible with various raw materials, it is also used to improve handling property andanother property by using in combination with petroleum-derived polyol. Castor oil based polyols havesufficient adhesive strength, and switching from epoxy type adhesive is progressing. In addition, with the risein environmental awareness, the movement to shift from petroleum-derived raw materials to plant-derivedraw materials is getting widespread. Castor oil, which is non-edible oil, has attracted attention as a promisingmaterial, and it is expected that demand for green chemicals will expand in the future.

Rigid polyurethane foams are used in various fields such as building applications, freezing and refrigerationequipment applications, civil engineering applications, marine vessel applications and the like, due to theirself-adhesive properties and high insulation performance. Energy saving for reducing carbon dioxide emissionsis now an important issue even in the industrial world. And rigid polyurethane foams with high thermalinsulation performance are increasingly required to reduce energy consumption. Since　the rigid polyurethanefoam for spraying has self-adhesiveness and can form seamless high insulation layer, it is often used in anapartment or a public building. Though hydrofluorocarbons （HFCs） have high global warming potential, theyhave been used as blowing agents until the present time. But, in recent years, the substitution of HFCs forhydrofluoroolefins （HFOs） which have low thermal conductivity of gas and low global warming potential isprogressing as alternative blowing agent. However, polyol system using HFOs has some problems with storagestability and physical properties of foams. We focused on the solubility of HFOs to polyols, and have developednew polyols with high reaction activity, whose polyol system shows excellent storage stability and improvedphysical properties of foams. In addition, due to aromatic structure of Mannich condensate of these polyols,improvement in flame retardancy of foams can be also expected.Key words : Rigid polyurethane foam, Self-adhesiveness, HFCs, HFOs

Generally, polyurethanes are prepared via polyaddition with polyisocyanates and polyol. Polyisocyanate isproduced by using amine and terribly toxic　phosgene in industrial, that is, produced by heavy environmentalloading. Carbon dioxide（CO₂） is safe and available as resource, and which dimethyl carbonate （DMC）, diphenylcarbonate （DPC） and so on are derived from. Carbamate is obtained from reaction between amine andDMC or DPC. Carbamate equivalent to isocyanate is very useful. Carbamate derivative can be applied to A-Bntype monomer, which is difficult to be obtained from polyisocyanate. Elastomer, hyper-branched and starburstpolymers are prepared from polyurethane via polycondensation of A-B_n type monomer.

Polyurethane （PU） elastomers with low hard segment content was synthesized using 1,4-Bis（isocyanatomethyl） cyclohexane （1,4-H₆XDI）, which induces aggregation and crystallization of hard segment.1,4-butanediol （BD）, 1,5-pentanediol （PD）, 1,4-butanedithiol （BDT）, 1,5-pentanedithiol （PDT） were used aschain extenders. Poly（oxytetramethylene） glycol（ PTMG, M_n = 1,800.（ consistent with Fig. 1）） was used as apolyol. BD- and BDT-based PU and PTU. （consistent with Section 3） exhibited higher degree of microphaseseparation in comparison with PD- and PDT-based PU and PTU. （consistent with Section 3）. Though dithiolbasedPUT. （consistent with Section 3） exhibited higher degree of microphase separation than diol-based PU,mechanical properties are almost the same. This is because the low crystallinity of hard segment phase withdithiol.

A facile one-pot, halogen-free method of synthesizing aromatic urethane directly from carbon dioxide（ CO2）,amines, and metal alkoxide is developed. Metal alkoxide could be regenerated upon reaction with alcohol duringwater removal. Notably, various aromatic urethane could be prepared from aromatic amine, CO2, and metalalkoxides. Aniline reacted with titanium methoxide （Ti（OMe）4） in the presence of CO2（ 5 MPa） to give thecorresponding methyl N-phenyl carbamate （MPC） in 85％ yield within 20 min. Ti（OMe）4 can be regeneratedby a reaction with DMC at 220℃. This methodology opens up a new route for the production of urethanes, especiallyaromatic urethanes, which are important precursors for polyurethane（ PUR）. A tentative mechanismfor this reaction is proposed, and the negative ρ value determined by Hammett analysis indicates nucleophilicattack of the amine onto the carbonyl species of Ti-carbonate complex derived from reaction of Ti（OMe）4 andCO2.

This comprehensive paper focuses on the reactivity of polyurethanes with dynamic covalent linkages,particularly on the structural reorganization of the polyurethanes based on the exchange reactions of thedynamic covalent linkages. At first, the fundamental principle of dynamic covalent linkage is described fromthe viewpoint of physical chemistry by showing their representative examples such as thermally activatedalkoxyamine exchange, catalyst-assisted olefin metathesis, and photo-induced disulfide metathesis. Then, thedesign and synthesis of various reactive polyurethanes with dynamic covalent linkages are introduced. Linearreactive polyurethanes with dynamic covalent linkages show interchain exchange reactions between thedynamic covalent linkages to change molecular weight, composition, and blockiness. In addition, cross-linkedreactive polyurethanes with dynamic covalent linkages show de-cross-linking reactions, unusual swellingbehavior, and self-healing. By selecting appropriate dynamic covalent linkages that can be activated by heating,catalyst, photo irradiation, or no stimulation, the linkage can endow polyurethanes with dynamic properties.