title: LCST transition of PNIPAM-b-PVCL in water: cooperative aggregation of two distinct thermally responsive segments.
abstract: The self-aggregation behavior of poly(N-isopropylacrylamide)-b-poly(N-vinylcaprolactam) (PNIPAM-b-PVCL) during the thermal-induced phase transition in water was explored by a combination of calorimetric, turbidity, dynamic light scattering (DLS) and FTIR measurements. Only one transition can be observed via all detecting methods, revealing the cooperative aggregation of the two distinct temperature-sensitive segments. What is more, the combination of strong hydrophobic interactions among the entire polymer chains and hydrogen bonds of C=O…H-N within PNIPAM segments results in the sharp variations at the LCST and gradual variations above the LCST during the phase transition of PNIPAM-b-PVCL aqueous solution upon heating. Additional analysis by perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2Dcos) indicates that the hydrophobic C-H groups have an earlier response than the relatively hydrophilic C=O groups during the LCST transition.
authors.affiliation: The State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Laboratory of Advanced Materials, Fudan University, Shanghai 200433, China. peiyiwu@fudan.edu.cn.
authors.forename: Lei
authors.initials: L
authors.lastname: Hou
authors.forename: Peiyi
authors.initials: P
authors.lastname: Wu
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002209:Caprolactam / Q000031:analogs & derivatives* / Q000737:chemistry; D006361:Heating; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D008958:Models, Molecular; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D012542:Scattering, Radiation; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D011108:Polymers; D014867:Water; C052970:poly-N-isopropylacrylamide; C086861:poly-N-vinylcaprolactam; D002209:Caprolactam