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  • Title: Tuning the Phase Transition from UCST-Type to LCST-Type by Composition Variation of Polymethacrylamide Polymers.
    Author: Käfer F, Pretscher M, Agarwal S.
    Journal: Macromol Rapid Commun; 2018 Dec; 39(24):e1800640. PubMed ID: 30284344.
    Abstract:
    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.
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