title: Molecular weight dependence of the poly(L-lactide)/poly(D-lactide) Stereocomplex at the air-water interface.
abstract: The molecular weight dependence of poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) stereocomplex behavior at the air-water interface was studied by surface pressure-area (pi-A) isotherms and atomic force microscopy (AFM). It was found that the compression-induced sterecomplexation of a PDLA/PLLA equimolar blend with high molecular weight (M(w) = 1 x 10(6) and 9.8 x 10(5), respectively) could occur at the air-water interface. This result is in marked contrast with the stereocomplexation of PDLA/PLLA blends in the bulk from the melt or in solutions, where the homocrystallites of either PLLA or PDLA rather than stereocomplex crystallites will be formed preferentially when the molecular weights of both polymers are higher than 1 x 10(5). Unexpectedly, the Langmuir-Blodgett behavior of the PDLA/PLLA blend with lower molecular weight (M(w) = 4 x 10(3) and 3.2 x 10(3), respectively), which should be favored in the stereocomplex, was distinct from that of other higher molecular weight blends. AFM images clearly disclosed for the first time the morphological changes of the equimolar blends of PLLA and PDLA at the air-water interface induced by increasing the surface pressure of the monolayer. Of particular note, the bilayer mechanism for the plateau in the isotherm was directly verified by the AFM height images.
authors.affiliation: State Key Laboratory of Polymer Physics & Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Duan
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Harumi
authors.initials: H
authors.lastname: Sato
authors.forename: Jianming
authors.initials: J
authors.lastname: Zhang
authors.forename: Hideto
authors.initials: H
authors.lastname: Tsuji
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Ozaki
authors.forename: Shouke
authors.initials: S
authors.lastname: Yan
mesh_terms: D000388:Air; D001672:Biocompatible Materials / Q000737:chemistry*; D001709:Biotechnology / Q000379:methods; D008051:Lipid Bilayers / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008962:Models, Theoretical; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism; D013696:Temperature; D014867:Water
chemical_list: D001672:Biocompatible Materials; D008051:Lipid Bilayers; D011091:Polyesters; D011108:Polymers; D014867:Water; C033616:poly(lactide)