Macromolecular engineering is composed of three essences: (1) Monomer design, (2) Polymerization design, and (3) Function design. However, these essences are separated in each academic field, that is, organic chemistry, polymer chemistry, and material science. In Kohsaka’s group, we recombine these research fields and lead the total design of ‘new advanced polymer materials’ based on sophisticated (macro)molecular design.
	The major research interests are alpha-functionalized acryl monomer. Acryl monomers are industrially important materials that are usually functionalized at the ester substituent. Functional group can be incorporated by a simple and facile reaction, esterification, while the functional group is far from the polymerization points so that they do not strongly affect the reaction. In contrast, functionalization at the alpha-substituent is rare. The early researches in 1950s-1960s have revealed that the substitution of alpha-position with bulky group prevents the polymerization both in radical and anionic mechanisms. Nowadays this is a ‘common sense’ and the functionalization at the alpha-position seems unpractical.
	On the other hand, pioneering researches in 1970s-1990s suggest that some alpha-functionalized acrylates undergo polymerization in specific reaction mechanism. Inspired by them, we recognize alpha-functionalized acrylates as key materials leading novel polymerization and function. Figures demonstrated in right means the strategy of our molecular design. Here let me allow to avoid the detail as they include professional knowledges, but we would emphasize that such alpha-functionalized acrylates provide remarkable new function and/or reactivity, although they are very simple molecules
	Polymerization of Highly Functionalized Ring The 6-membered lactone described in right has three functional groups in the ring, that is, vinyl group, ester bond, and acetal bond. As 5 of 6 atoms join the functions, the lactone can be regarded ultimately functionalized. Vinyl polymerization can be employed with radical and anionic initiator, while cationic and anionic ring-opening polymerization might be applicable. Now we have proceeded the projects on the polymerization and post-polymerization modification. [Relative paper]　 "α-Exomethylene lactone possessing acetal-ester linkage: Polymerization and postpolymerization modification for water-soluble polymer" Y. Kohsaka, Y. Matsumoto, T. Zhang, Y. Matsuhashi, T. Kitayama, J. Polym. Sci. Part A: Polym. Chem. 54, 955-961 (2016). (Spotlight Article)
	pH- and Thermo-Responsive Vinyl Polymers by Amino Acid Derivatives Amino acids bearing polymerizable vinyl group are interesting platforms to prepare stimuli-responsive biocompatible vinyl polymers. alpha-(Aminomethyl)acrylic acid is a naturally occurring beta-amino acid. We have found the radical polymerization of the monomer proceeds in a unique mechanism to afford pH- and thermos-responsive polymer in acidic aqueous media. Further researches focused on both polymerization chemistry and material science are under construction. [Relative paper] "α-(Aminomethyl)acrylate: polymerization and spontaneous post-polymerization modification of β-amino acid ester for a pH/temperature-responsive material " Y. Kohsaka, Y. Matsumoto, T. Kitayama, Polym. Chem. 6, 5026-5029 (2015).
	Synthesis of Chemically Degradable Biocompatible Polymer Based on Conjugate Substituon alpha-(Halomethyl)acrylates, which have characters of both acrylate and allyl halide, undergoes conjugate substitution with various nucleophiles under ambient conditions. The reaction products, alpha-(substituted methyl)acrylates, are still active to conjugate substitution/addition. Therefore, we have interested in the polycondensation of bis[alpha-(halomethyl)acrylates] resulting in poly(conjugated esters), which can be decomposed by further conjugate substitution. Similar poly(conjugated ester)s can be obtained through the ring-opening polymerization of 6-membered cyclic hemiacetal ester (lactone) described above. ［関連論文］ "Polymerization of α-(Halomethyl)acrylates through Sequential Nucleophilic Attack of Dithiols using a Combination of Addition–Elimination and Click Reactions" Y. Kohsaka, K. Hagiwara, K. Ito, Polym. Chem. 8, 976-979 (2017). "Conjugate substitution and addition of α-substituted acrylate: a highly efficient, facile, convenient, and versatile approach to fabricate degradable polymers by dynamic covalent chemistry" Y. Kohsaka, T. Miyazaki, K. Hagiwara, Polym. Chem. advanced article. DOI: 10.1039/C7PY02114C