Tuning the Phase Transition from UCST‐Type to LCST‐Type by Composition Variation of Polymethacrylamide Polymers. Issue 24 (3rd October 2018)

• Record Type: Journal Article
• Authors: Käfer, Florian; Pretscher, Martin; Agarwal, Seema
• Is Part Of: Macromolecular rapid communications. Volume 39:Issue 24(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-10-03
• Subjects: composition -- LCST -- polymethacrylamide -- thermoresponsive polymers -- UCST; Macromolecules -- Periodicals; Polymers -- Periodicals; Chemistry -- Periodicals; 547.705
• DOI: 10.1002/marc.201800640
• Languages: English
• ISSNs: 1022-1336

Abstract

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. Abstract : The broad UCST‐type cooling/heating hysteresis of polymethacrylamide in water can be changed to either a soluble, insoluble, or a narrow LCST‐type transition based on copolymer composition on copolymerization with hydrophobic N ‐substituted acrylamides. The cloud points of LCST‐type are stable to change in concentration and can be tuned by additives such as urea.