Conformational changes of poly(N-isopropylacrylamide) chains at air/water interface: effects of temperature, compression rate, and packing density.
This study concerns the effects of temperature, compression rate, and packing density on conformational properties of polystyrene-block-poly(N-isopropylacryamide) (PS-b-PNIPAM) diblock copolymer monolayers at the air/water interface using the Langmuir balance technique. The dependency of surface pressure changes on temperature and compression rate is strongly influenced by the conformations of PNIPAM chains at the interface, which can be adjusted by varying the packing density. Specifically, when loops or tails are formed at the interface, PNIPAM chains display thermosensitive properties due to hydration/dehydration and obvious dependence on compression rate. When PNIPAM chains take train conformation at the air/water interface, however, the surface pressure changes are nearly independent of temperature and compression rate because almost all segments of the PNIPAM chains are adsorbed at the interface and the nonpolar isopropyl groups are preferentially oriented toward the air. Our work reveals that one could manipulate stimuli-responsive properties of PNIPAM chains at the interface simply by adjusting the conformations of PNIPAM chains.
Liu
Guangming
G
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Yang
Shihe
S
Zhang
Guangzhao
G
D000178:Acrylamides / Q000737:chemistry*; D000180:Acrylic Resins; D000388:Air; D008968:Molecular Conformation; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
D000178:Acrylamides; D000180:Acrylic Resins; D011108:Polymers; D014867:Water; C052970:poly-N-isopropylacrylamide