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Small dop of comonomer, giant shift of cloud point: Thermo‐responsive behavior and mechanism of poly(methylacrylamide) copolymers with an upper critical solution temperature
Author(s) -
Lu Jianlei,
Zhou Xionglin,
Sun Jialin,
Xu Mengdi,
Zhang Mingming,
Zhao Chuanzhuang
Publication year - 2021
Publication title -
journal of polymer science
Language(s) - English
Resource type - Journals
eISSN - 2642-4169
pISSN - 2642-4150
DOI - 10.1002/pol.20210161
Subject(s) - upper critical solution temperature , copolymer , comonomer , monomer , polymer , polymer chemistry , materials science , cloud point , methyl methacrylate , methacrylate , ethylene glycol , chemical engineering , lower critical solution temperature , chemistry , organic chemistry , aqueous solution , composite material , engineering
Poly(methylacrylamide) (PMAM) is a thermo‐responsive polymer with an upper critical solution temperature (UCST). Its cloud point ( T cp ) is around 60 °C, unsuitable for certain biomedical and industrial applications. This study brought up a copolymerization strategy to tune the T cp of PMAM with hydrophilic comonomers. Surprisingly, with a small portion of hydrophilic monomer doped, the T cp of the PMAM copolymer can be significantly shifted. For instances, with ≤7 mol% of acrylamide or 1 mol% of oligo(ethylene glycol) methacrylate, the T cp can be shifted in a wide range from ~69 to ~0 °C. Microdifferential scanning calorimetry demonstrated that the enthalpic effect during the phase transition of the solutions is indistinctive, while fluorescence measurement with pyrene as a probe revealed that the hydrogen‐bonding within polymer chains is enhanced by the hydrophobic aggregation of methyl groups. Therefore, the doped hydrophilic monomer could remarkably alter the ordering of water‐molecules and the extent for the aggregation of methyl groups, leading to the pronounced shifting in the T cp of the copolymers. This work would facilitate the application of PMAM as smart polymer materials and guide the inventions of functional materials based on UCST polymers.