Inversion of polymer micelles formed from double thermo-sensitive diblock copolymers

我们合成了几种由聚苯乙烯和聚苯乙烯组成的双温敏嵌段共聚物，（磺基甜菜碱）和聚（N-烷基丙烯酰胺）嵌段，其分别具有上临界溶解温度（UCST）和下临界溶解温度（LeST），通过RAFT（可逆加成断裂链转移）方法，使用4-氰基戊酸二硫代苯甲酸酯作为链转移试剂。电晕反转仅仅取决于温度，即聚（磺基甜菜碱）-核和聚在UCST以下和LCST以上分别形成了以N-烷基丙烯酰胺为核心的胶束。（3-二甲基（甲基丙烯酰氧乙基）丙磺酸铵）（PdMMAEAPS）和聚乙烯（N、N-二乙基丙烯酰胺）s（PdEA）嵌段的研究表明，v（CO）和v（SO_3）PdMMAEAPS嵌段的谱带和PdEA嵌段的酰胺I谱带在UCST和LCST处发生关键变化，结果表明，在每次跃迁时，每个嵌段的链段相互作用都发生了变化。苯胺基萘嵌段染料的胶束化温度随溶剂组成的变化而变化，如PdMIN 4AEAPS嵌段的UCST随NaCl浓度的增加而降低，PdMIN 4AEAPS嵌段的UCST随NaCl浓度的增加而降低，PdMIN 4AEAPS嵌段的UCST随NaCl浓度的增加而降低，而聚（4-二甲基丙烯酰胺丙基丙磺酸铵）嵌段的UCST增大。

We have prepared several double thermosensitive diblock copolymers consisting of poly(sulfobetaine) and poly(N-alkyl acrylamide) blocks, which have a upper critical solution temperature(UCST)and a lower critical solution temperature(LeST), respectively, by RAFT(Reversible Addition Fragmentation chain Transfer)process using 4-cyanopentanoic acid dithiobenzoate as a chain transfer regent.The block copolymers form micelles that exhibit a core-corona inversion simply depending on temperature, that is, poly(sulfobetaine)-core and poly(N-alkyl acrylamide)-core micelles are formed below the UCST and above the LCST, respectively.IR spectroscopic investigation on the micellization of a diblock copolymer consisting of poly(3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate)(PdMMAEAPS) and poly(N, N-diethylacrylamide)s (PdEA) blocks showed that the v(C0) and v(S0_3) bands of the PdMMAEAPS block and the amide I band of PdEA block critically changes at the UCST and LCST, respectively.The result indicates that segmental interaction of each block is altered at each transition.Fluorescence measurements using pyrene and 2-anilinonaphtalene showed that these dyes are incorporated in PdEA-core micelles formed above the LCST.Micellization temperatures can be controlled by adding additives such as salts and alcohols.Dependencies of micellization temperature on solvent composition is varied with properties of each block.For example, the UCST of PdMIN4AEAPS block decreases with increasing concentration of NaCI, but the UCST of poly(4-dimethyl(acrylaminopropyl) ammonium propane sulfonate)block increases.