Macromolecular Chemistry II and Bayreuth Center for Colloids and Interfaces, Universitätsstrasse 30, 95440, Bayreuth, Germany.
Macromol Rapid Commun. 2018 Dec;39(24):e1800640. doi: 10.1002/marc.201800640. Epub 2018 Oct 3.
Polymethacrylamide copolymers with hydrophobic N-substituted acrylamides, such as N-cyclohexylacrylamide and N-tert-butylacrylamide, are rare examples of polymers showing composition-dependent thermoresponsive behavior in water. They show unexpected behavior different from the conventional copolymers of a thermoresponsive polymer with hydrophobic comonomers. On increasing the amount of the hydrophobic comonomer in the polymer, there is a change from UCST-type phase behavior to complete solubility, followed by compositions showing LCST-type transition and insolubility in water (U-S-L-I-type change). At 50 mol% of less hydrophobic N-tert-butyl acrylamide (logP 0.87) in contrast to ≈25 mol% of N-cyclohexylacrylamide (logP 1.51), the broad UCST-type transition of polymethacrylamide is turned to LCST-type transitions with very narrow hysteresis in water and PBS buffer. The use of H-bond and water-structure breaker showed the role of H-bonding and hydrophobic interactions in phase transitions of UCST-type and LCST-type, respectively. This work is an important add-on to the infant field of nonionic polymers of UCST-type.
具有疏水性 N-取代丙烯酰胺的聚甲基丙烯酰胺共聚物，如 N-环己基丙烯酰胺和 N-叔丁基丙烯酰胺，是在水中表现出组成依赖性热响应行为的聚合物的罕见示例。它们表现出与传统的热敏性聚合物与疏水性共聚单体的共聚体不同的意外行为。随着聚合物中疏水性单体含量的增加，会发生从 UCST 型相行为到完全溶解的变化，然后是表现出 LCST 型转变和在水中不溶（U-S-L-I 型变化）的组成。与 ≈25 mol%的 N-环己基丙烯酰胺（logP 1.51）相比，疏水性较低的 N-叔丁基丙烯酰胺（logP 0.87）的含量为 50 mol%时，聚甲基丙烯酰胺的宽 UCST 型转变转变为 LCST 型转变，在水中和 PBS 缓冲液中具有非常窄的滞后。氢键和破坏水结构的试剂的使用表明氢键和疏水相互作用在 UCST 型和 LCST 型相转变中的作用。这项工作是 UCST 型非离子聚合物这一新生领域的重要补充。
