Solubilization - Cayoka

This refers to the phenomenon in which the solubility of a poorly soluble solute in a solvent increases in the presence of a cosolute, which is called a solubilizer. When the solvent is water and the solute is an organic substance (such as an oil-soluble dye), surfactants are known to act as solubilizers. Oil-soluble dyes that have little solubility in water become quite soluble when the surfactant is present at a concentration above the micelle-forming concentration. In this case, the oil-soluble dye is taken up into the hydrophobic parts inside or on the surface of the surfactant micelle. Many water-soluble polymers also act as solubilizers. An example is polysoap, such as the partially dodecylated product of poly(2-vinylpyridine). The shape of polysoaps, which are polymer electrolytes, is determined by their interactions with the solvent molecules in solution, the degree of ionization of the charged groups, and the distribution state, but the hydrophobic groups come together to form hydrophobic domains, which are then used to take up hydrophobic compounds and solubilize them. Synthetic polymers such as poly(vinyl alcohol), polymethacrylic acid, polyethyleneimine, and polystyrene sulfonic acid, and biopolymers such as serum albumin, β-lactoglobulin, DNA, and insulin are also known as solubilizers. The phenomenon in which the solubility of poorly water-soluble substances is increased by adding large amounts of aromatic sulfonic acids, aromatic carboxylic acids, phenols, alcohols, pyrrolidones, and ureas is called hydrotropy.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

溶媒に難溶の溶質が，共存溶質(cosolute)の存在によってその溶解度を増す現象をいい，共存溶質を可溶化剤という．溶媒が水で，溶質が有機物(たとえば，油溶性染料)の場合，可溶化剤としては界面活性剤が知られている．水中でほとんど溶解度のない油溶性染料は，界面活性剤がミセル生成濃度以上に存在するとき，かなりの溶解度を示す．この場合，油溶性染料は界面活性剤ミセルの内部または表面の疎水性部分に取り込まれる．水溶性高分子にも可溶化剤としてのはたらきをもつものが多い．ポリ(2-ビニルピリジン)の部分ドデシル化物などのポリソープがその例としてあげられる．高分子電解質であるポリソープは，溶液中で溶媒分子との相互作用や荷電基のイオン化度，分布状態によってその形態が規定されるが，疎水基部分が寄り集まって疎水性のドメインを形成し，そこに疎水性化合物を取り込んで可溶化が行われる．ポリ(ビニルアルコール)，ポリメタクリル酸，ポリエチレンイミン，ポリスチレンスルホン酸などの合成高分子，血清アルブミン，β-ラクトグロブリン，DNA，インスリンなどの生体高分子も可溶化剤として知られている．芳香族スルホン酸，芳香族カルボン酸，フェノール類，アルコール類，ピロリドン類，尿素類を多量に加えると水に難溶性物質の溶解度を増大させる現象は，ヒドロトロピーと称される．

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